The WCRF/AICR Third Expert Report, Diet, Nutrition, Physical Activity and Cancer: a Global Perspective, uses a range of scientific terms, which are explained below for reference.

Absorption

The movement of nutrients and other food constituents from the gut into the blood.

Acetaldehyde

The major metabolic product of ethanol, which is generated by ethanol dehydrogenase and subsequently metabolised to acetate by aldehyde dehydrogenase.

Acetylation

The introduction of an acetyl group (CH3CO-) into a compound. Acetylation of histone proteins in chromosomes tends to activate genes or facilitate transcription of genes into mRNA and translation of mRNA into protein.

Acid-base balance

The appropriate acidity of the blood and tissues. Abnormal acid-base balance may indicate a change in respiratory or metabolic status.

Acute

Describing a condition or disease that lasts a short time, comes on rapidly, and is often accompanied by distinct symptoms.

Adenine

A purine derivative and one of the four possible nitrogenous bases in nucleotides and nucleic acids (DNA and RNA). Base pairs with thymine.

Adenocarcinoma

Cancer of glandular epithelial cells.

Adenomatous polyposis coli (APC) gene

A gene that provides instructions for making the APC protein, which plays a critical role in several cellular processes. The protein acts as a tumour suppressor, keeping cells from growing and dividing too fast or in an uncontrolled way.

Adenosine triphosphate (ATP)

The principal molecule used for storage and transfer of energy in metabolic processes.

Adenosquamous carcinoma

A type of cancer that contains two types of cells: squamous cells (thin, flat cells that line certain organs) and gland-like cells.

Adipocytes

Cells of adipose tissue, where fats (triglycerides) are stored.

Adipokines

Cytokines (cell signalling proteins) secreted by adipose tissue.

Adiponectin

A protein secreted by adipose tissue that is inversely related to body fatness. High concentrations have been associated with a lower risk of kidney cancer.

Adipose tissue

Body fat. Tissue comprising mainly cells containing triglyceride (adipocytes). It acts as an energy reserve, provides insulation and protection, and secretes metabolically active hormones.

Adiposity

Degree of body fatness; can be measured indirectly in a variety of ways including body mass index (see body mass index) and percentage body fat.

Adjustment

A statistical tool for taking into account the effect of known confounders (see confounder).

Advanced glycation endproducts (AGEs)

Proteins or lipids that become glycated following exposure to sugars.

Aerobic metabolism

The normal process of producing ATP as a source of energy using oxygen.

Aerobic physical activity/exercise

Relating to or denoting exercise taken to improve the efficiency of the body's cardiovascular system in absorbing and transporting oxygen.

Aerodigestive cancers

Cancers of the organs and tissues of the respiratory tract and the upper part of the digestive tract (including the lips, mouth, tongue, nose, throat and oesophagus).

Aflatoxins

Naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, most notably Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and carcinogenic to animals, including humans.

Alcohol

An organic compound that contains a hydroxyl group bound to a carbon atom. Releases energy when metabolised in the body. Commonly ethanol C6H5OH.

aMED (Mediterranean) score

The aMed score is a modified Mediterranean Diet score that includes consumption of vegetables (excluding potatoes), legumes, fruit, nuts, whole grains, fish, ratio of monounsaturated to saturated fat, red and processed meat and alcohol.

Amenorrhoea

The absence of menstruation

American Cancer Society (ACS) Guidelines score

The ACS score includes maintaining a healthy body weight, engaging in moderate to vigorous physical activity, making healthy dietary choices and limiting alcohol intake.

Amino acids

Building blocks of proteins that possess both a carboxyl (-COOH) and an amino (-NH2) group attached to the same carbon atom and are water-soluble organic compounds.

Anaerobic metabolism

The process of producing ATP (see adenosine triphosphate) as a source of energy without oxygen, resulting in lactic acid accumulation.

Anaerobic physical activity/exercise

Relating to or denoting exercise that does not improve the efficiency of the body's cardiovascular system in absorbing and transporting oxygen.

Anaphase bridge

When telomeres of sister chromatids fuse together and fail to completely segregate into their respective daughter cells during mitosis. Most prevalent during the anaphase, when sister chromatids move to opposite ends of the spindle fibre.

Androgen

Any masculinising sex hormone, such as testosterone.

Aneuploidy

The presence of an abnormal number of chromosomes in a cell, such as having 45 or 47 chromosomes when 46 are expected.

Angiogenesis

The process of generating new blood vessels.

Anthropogenic

Originating in human activity, usually related to environmental pollution and pollution.

Anthropometric measures

Measures of body dimensions.

Antioxidant

A molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction involving the loss of electrons, which can produce free radicals. In turn, these radicals can start chain reactions, which can cause damage or death to cells (see free radicals).

Apoptosis

The death of cells that occurs as a normal and controlled part of the cell cycle.

Arseniasis

Chronic arsenic poisoning.

Autocrine

Denoting a mode of hormone action in which a hormone binds to receptors on and affects the functions of the same cell that produced it.

Basal metabolism

The minimum amount of energy required to maintain vital functions at complete rest, measured by the basal metabolic rate in a fasting individual who is awake and resting in a comfortably warm environment.

Basal cell carcinoma

A type of cancer of the basal cells at the bottom of the epidermis. The most common form of skin cancer. Basal cell carcinomas are usually found on areas of the body exposed to the sun. They rarely metastasise (spread) to other parts of the body.

Basal metabolic rate (BMR)

The amount of energy required to maintain the essential body functions in resting and fasting conditions, expressed as megajoules, kilojoules or kilocalories per minute, hour or day.

Bias

In epidemiology, consistent deviation of an observed result from the true value in a particular direction (systematic error) due to factors pertaining to the observer or to the study type or analysis (see selection bias).

Bile

A greenish-yellow fluid secreted by the liver and stored in the gallbladder. Bile plays an important role in the intestinal absorption of fats. Bile contains cholesterol, bile salts and waste products such as bilirubin.

Bioactive constituents

Compounds that have an effect on a living organism, tissue or cell. In nutrition, bioactive compounds are distinguished from nutrients.

Bioactivity

The effect of a given agent on a living organism or on living tissue.

Bioavailability

Degree to which a drug or other substance becomes available to the target tissue after administration.

Biological mechanisms

System of causally interacting processes that produce one or more effects.

Biomarker

A naturally occurring molecule, gene or characteristic by which a particular pathological or physiological process can be identified.

Body composition

The composition of the body in terms of the relative proportions of water and adipose and lean tissue. Can also be described as the proportions of fat (lipid) and fat-free mass. May also include the content of micronutrients, such as iron, and the distribution of adipose tissue, for example, central/peripheral or visceral/subcutaneous.

Body mass index (BMI)

Body weight expressed in kilograms divided by the square of height expressed in metres (BMI = kg/m2). Provides an indirect measure of body fatness.

C-reactive protein

A specific protein whose concentration in the blood rises in response to inflammation.

Cachexia

A loss of lean tissue mass, involving weight loss greater than 5% of body weight in 12 months or less in the presence of chronic illness or as a body mass index (BMI) lower than 20 kg/m2.

Caecum

A pouch connected to the junction of the small and large intestines.

Caffeine

An alkaloid found in coffee, tea, kola nuts, chocolate and other foods that acts as a stimulant and a diuretic.

Calcium

An essential nutrient for many regulatory processes in all living cells, in addition to playing a structural role in the skeleton. Calcium plays a critical role in the complex hormonal and nutritional regulatory network related to vitamin D metabolism, which maintains the serum concentration of calcium within a narrow range while optimising calcium absorption to support host function and skeletal health.

Cancer

Any disorder of cell growth that results in the invasion and destruction of surrounding healthy tissue by abnormal cells and which may spread to distant sites. Cancer cells arise from normal cells whose nature is permanently changed.

Carbohydrate

Type of organic compound of sugars and an essential intermediate in the conversion of food to energy. A dietary micronutrient that releases energy when metabolised in the body.

Carbohydrate polymer

Macromolecules comprised of two or more monomeric sugar units bound together by glycosidic linkages.

Carcinogen

Any substance or agent capable of causing cancer.

Carcinogenesis

The process by which a malignant tumour is formed.

Carcinoma

Malignant tumour derived from epithelial cells, usually with the ability to spread into the surrounding tissue (invasion) and produce secondary tumours (metastases).

Carcinoma in situ

The first stage of carcinoma in which the malignant tumour has not spread beyond the epithelium.

Cardia stomach cancer

A sub-type of stomach cancer that occurs in the cardia, near the gastro-oesophageal junction.

Carotenoids

A diverse class of compounds providing colour to many plants. Carotenoids are often classified in two groups: as those providing the host with vitamin A, such as beta-carotene, and the non-pro-vitamin A carotenoids, such as lycopene, which provides the familiar red colour of tomatoes.

Catalyse

To speed up the rate of a chemical reaction through the use of a catalyst, a substance that remains unchanged by the reaction.

Case-control study

An epidemiological study in which the participants are chosen on the basis of their disease or condition (cases) or lack of it (controls), to test whether distant or recent history of an exposure such as tobacco smoking, genetic profile, alcohol consumption or dietary intake is associated with the risk of disease.

Cell

Structural and functional unit of most living organisms. Can exist independently or as part of a tissue or organ.

Cell adhesion

Process whereby cells interact and attach to a surface, substrate or another cell, mediated by interactions between molecules of the cell surface. Essential for maintaining multicellular structure.

Cell cycle

The highly regulated process by which cells replicate and divide, allowing tissues to grow and remain healthy.

Cell differentiation

The process of development of cells to take on the structural and functional characteristics specific to a particular tissue. Also, the degree to which tumour cells have the structure or function of the tissue from which the tumour arose. Tumours can be described as well, moderately or poorly differentiated: well-differentiated tumours appear similar to the cells of the tissue in which they arose; poorly differentiated tumours do not. The degree of differentiation may have prognostic significance.

Cell line

A cell culture developed from a single cell and therefore consisting of cells with a uniform genetic make-up.

Cell proliferation

An increase in the number of cells as a result of increased cell division.

Cell signalling

Complex communication system that governs basic activities of cells and coordinates cell actions through bonding of ligands to receptors on the cell surface. Cells within tissue use chemicals such as cytokines, growth factors, and hormones to communicate.

Cell-cycle arrest

Cessation of progress through the cell cycle at checkpoint, which halts progression into mitosis.

Cell transformation

The genetic alteration of a cell resulting from the direct uptake and incorporation of genetic material from outside the cell (exogenous DNA) from its surroundings, taken up through the cell membrane(s).

Checkpoint

Point in the cell cycle of eukaryotic cells at which progress can be halted if the appropriate conditions are not met.

Chemotherapeutic agent

Any chemical used to treat cancer, usually refers to antineoplastic drugs.

Cholangiocarcinoma

A malignant tumour in the ducts that carry bile from the liver to the small intestine.

Cholesterol

The principal sterol in animal tissues, synthesised in the body; an essential component of cell membranes and the precursor of the steroid hormones and vitamin D.

Chromatin

Substance of which eukaryotic chromosomes are composed. Consists of proteins (histones), DNA and small amounts of RNA in a highly condensed solenoid arrangement.

Chromosomal instability

Results from ongoing errors in chromosome segregation during mitosis resulting in whole chromosomes or parts of chromosomes being duplicated or deleted, rendering them unstable.

Chromosome

Threadlike structure found in the nucleus of animal cells composed of chromatin. Carries the genes.

Chromosome segregation

When two sister chromatids or paired homologous chromosomes separate from each other during mitosis and migrate to opposite poles of the nucleus.

Chronic

Describing a condition or disease that is persistent or long lasting.

Cirrhosis

A condition in which normal liver tissue is replaced by scar tissue (fibrosis), with nodules of regenerative liver tissue.

Clear cell renal cell carcinoma (CCRCC)

The most common type of kidney cancer in adults, characterised by malignant epithelial cells with clear cytoplasm.

Cofactor

Non-protein component essential for the normal catalytic activity of an enzyme consisting of organic molecules (coenzymes) or inorganic ions.

Cohort study

A study of a (usually large) group of people whose characteristics are recorded at recruitment (and sometimes later) and followed up for a period of time during which outcomes of interest are noted. Differences in the frequency of outcomes (such as disease) within the cohort are calculated in relation to different levels of exposure to factors of interest – for example, tobacco smoking, alcohol consumption, diet and exercise. Differences in the likelihood of a particular outcome are presented as the relative risk, comparing one level of exposure with another.

Colon

Part of the large intestine extending from the caecum to the rectum.

Colonisation sites

The first site in a different organ from which the cancer originates that metastatic tissue colonises.

Colonocyte

An epithelial cell of the colon.

Compliance

The extent to which people such as study participants follow an allocated treatment programme.

Confidence interval (CI)

A measure of the uncertainty in an estimate, usually reported as 95% confidence interval (CI), which is the range of values within which there is a 95% chance that the true value lies. For example, the association of tobacco smoking and relative risk of lung cancer may be expressed as 10 (95% CI 5–15). This means that the estimate of the relative risk was calculated as 10 and that there is a 95% chance that the true value lies between 5 and 15.

Confounder/confounding factors

A variable that is associated with both an exposure and a disease but is not in the causal pathway from the exposure to the disease. If not adjusted for within a specific epidemiological study, this factor may distort the apparent exposure–disease relationship. An example is that tobacco smoking is related both to coffee drinking and to risk of lung cancer, and thus unless accounted for (adjusted) in studies, might make coffee drinking appear falsely as a cause of lung cancer.

Conjugated linoleic acids

Specific fatty acids typically found in lipids derived from foods, such as milk or meats, from ruminant animals such as cows, goats or sheep.

CpG island

Stretch of DNA, several hundred to several thousand bases long, that is rich in dinucleotides containing the bases cytosine and guanine. The ‘p’ denotes a phosphodiester bond meaning the C and G residues are joined along the same strand of DNA. Abundant in the promoter region of eukaryotic genes.

CT scans

A computerised tomography (CT) scan combines a series of X-ray images taken from different angles and uses computer processing to create cross-sectional images, or slices, of the bones, blood vessels and soft tissues inside the body.

Cytokines

Cell-signalling molecules that aid cell-to-cell communication in immune responses and stimulate the movement of cells toward sites of inflammation, infection and trauma.

Cytosine

A pyrimidine derivation and one of the four possible nitrogenous bases in nucleotides and nucleic acids (DNA and RNA). Base pairs with guanine.

De-differentiated

Cell or tissue that undergoes reversal of differentiation and loss of specialised characteristics.

Deficiency disease

A disease caused by the lack of an element in the diet, usually a particular vitamin or mineral.

Deoxyribonucleic acid (DNA)

The double-stranded, helical molecular chain found within the nucleus of each cell, which carries the genetic information.

Diet, nutrition and physical activity

In the CUP, these three exposures are taken to mean the following: diet, the food and drink people habitually consume, including dietary patterns and individual constituent nutrients as well as other constituents, which may or may not have physiological bioactivity in humans; nutrition, the process by which organisms obtain energy and nutrients (in the form of food and drink) for growth, maintenance and repair, often marked by nutritional biomarkers and body composition (encompassing body fatness); and physical activity, any body movement produced by skeletal muscles that requires energy expenditure.

Dietary fibre

Constituents of plant cell walls that are not digested in the small intestine. Several methods of analysis are used, which identify different components. The many constituents that are variously included in the definitions have different chemical and physiological features that are not easily defined under a single term. The different analytical methods do not generally characterise the physiological impact of foods or diets. Non-starch polysaccharides are a consistent feature and are fermented by colonic bacteria to produce energy and short chain fatty acids including butyrate. The term ‘dietary fibre’ is increasingly seen as a concept describing a particular aspect of some dietary patterns.

Dietary supplement

A substance, often in tablet or capsule form, which is consumed in addition to the usual diet. Dietary supplements typically refer to vitamins or minerals, though phytochemicals or other substances may be included.

Differentiation

Process in development in which unspecialised cells or tissues are systemically modified and altered to achieve specific and characteristic physical forms, physiological functions, and chemical properties.

DNA adduct

A chemical that binds to DNA. This distorts the DNA structure and disrupts its replication, increasing the likelihood of errors in DNA replication, subsequent mutations and possibly cancer.

DNA methylation

A process by which methyl groups are added to DNA. DNA methylation is one of several epigenetic mechanisms that regulate gene expression.

DNA methyltransferase

Enzyme that adds methyl groups to DNA (nucleic acids) so as to modify gene expression.

DNA promoter region

Segment of DNA, upstream of a gene, where RNA polymerase binds to initiate transcription.

Dominant mutation

A pattern of inheritance in which an individual will express the mutation if they have at least one copy of the mutant (or dominant) gene.

Dose–response

A term derived from pharmacology that describes the degree to which an association or effect changes as the level of an exposure changes, for instance, intake of a drug or food.

Ecological study

A study in which differences in patterns of exposure, for instance in consumption of a particular nutrient or food, are compared at aggregate level, with populations (rather than individual people) as the unit of analysis.

Effect modification

Effect modification (or effect-measure modification) occurs when the effect of an exposure differs according to levels of another variable (the modifier).

Egger’s test

A statistical test for small study effects such as publication bias.

Eicosanoids

Compounds formed in the body from long-chain polyunsaturated fatty acids formed by cyclooxygenase or lipoxygenase, which act as local hormones and are involved in inflammation, regulating cell growth, and a variety of other functions.

Enabling characteristic

Property a cancer cell exhibits which facilitates the attainment and sustainment of the ‘hallmarks of cancer’.

Endocrine

Referring to organs or glands that secrete hormones into the blood.

Endogenous

Substances or processes that originate from within an organism, tissue or cell.

Energy

Energy, measured as calories or joules, is required for all metabolic processes. Fats, carbohydrates, proteins and alcohol from foods and drinks release energy when they are metabolised in the body.

Energy balance

The state in which the total energy absorbed from foods and drink equals total energy expended, for example, through basal metabolism and physical activity. Also the degree to which intake exceeds expenditure (positive energy balance) or expenditure exceeds intake (negative energy balance).

Energy harvest

Extraction of energy for microbial metabolism by micro-organisms normally residing in the colon, usually through fermentation of indigestible dietary carbohydrates. The by-products of fermentation can be absorbed and contribute to the energy supply for the human host.

Enzyme

Protein that acts as a catalyst in biochemical reactions. Each enzyme is specific to a particular reaction or group of similar reactions. Many require the association of certain non-protein cofactors in order to function.

Epigenetics

Relating to the control of gene expression through mechanisms that do not depend on changes in the nucleotide sequence of DNA, for example, through methylation of DNA or acetylation of histone.

Epithelial / Epithelium

The layer of cells covering internal and external surfaces of the body, including the skin and mucous membranes lining body cavities such as the lung, gut and urinary tract.

Epithelial-mesenchymal transition (EMT)

A developmental process in which epithelial cells exhibit reduced adhesion, increased cell mobility and loss of E-cadherin expression. The transition in behaviour is important in mesoderm formation and neural tube formation.

Essential nutrient

A substance that is required for normal metabolism that the body cannot synthesise at all or in sufficient amounts, and thus must be consumed.

Ethanol

An organic compound in which one of the hydrogen atoms of water has been replaced by an alkyl group (see alcohol).

Exocrine

Relating to or denoting glands that secrete their products through ducts opening on to an epithelium rather than directly into the blood.

Exogenous

Arising from outside the body.

Exposure

A factor to which an individual may be exposed to varying degrees, such as intake of a food, level or type of physical activity, or aspect of body composition.

Extracellular matrix

The material that surrounds cells in animal tissues. Contains an aqueous lattice of proteins and other molecules.

Extravasate

Allowing or forcing out a fluid, especially blood, to move from the vessel that contains it to the surrounding area.

Familial

Relating to or occurring in a family or its members.

Fat

Storage lipids of animal tissues, mostly triglyceride esters (see adipose tissue).

Fatty acid

A carboxylic acid with a carbon chain of varying length, which may be saturated (no double bonds) or unsaturated (one or more double bonds). Three fatty acids attached to a glycerol backbone make up a triglyceride, the usual form of fat in food and adipose tissue.

Flavonoids

Bioactive compounds that are found naturally in fruits and vegetables, as well as other dietary sources such as tea (Camellia sinensis).

Folate

A salt of folic acid. Present in leafy green vegetables, peas and beans, and fortified breads and cereals.

Forest plot

A simple visual representation of the amount of variation between the results of
the individual studies in a meta-analysis. Their construction begins with plotting the observed exposure effect of each individual study, which is represented as the centre of a square. Horizontal lines run through this to show the 95% confidence interval. Different-sized squares may be plotted for each of the individual studies, the size of the box increasing with the size of the study and the weight that it takes in the analysis. The overall summary estimate of effect and its confidence interval can also be added to the bottom of this plot, if appropriate, represented as a diamond. The centre of the diamond is the pooled summary estimate and the horizontal tips are the confidence intervals.

Free radicals

An atom or molecule that has one or more unpaired electrons. A prominent feature of radicals is that they have high chemical reactivity, which explains their normal biological activities and how they inflict damage on cells. There are many types of radicals, but those of most importance in biological systems are derived from oxygen and known collectively as reactive oxygen species.

Functional capacity

The optimal or maximum level at which the body, organ or tissue can function.

Functional reserve

Remaining capacity of an organ or tissue to fulfil its physiological activity, especially in the context of disease, ageing or impairment.

Gene

Unit of heredity composed of DNA. Visualised as a discrete particle, occupying specific position (locus) on a chromosome, that determines a particular characteristic.

Gene amplification

Gene amplification is an increase in the number of copies of a gene sequence. Cancer cells sometimes produce multiple copies of genes in response to signals from other cells or their environment.

Gene expression

The manifestation of the effects of a gene by the production of the particular protein, polypeptide or type of RNA whose synthesis it controls. The transcription of individual genes can be ‘switched on’ or ‘switched off’ according to the needs and circumstances of the cell at a particular time.

Genetic code

Means by which genetic information in DNA is translated into the manufacture of specific proteins by the cell. Represented by codons, which take the form of a series of triplets of bases in DNA, from which is transcribed a complementary sequence of codons in messenger RNA. The sequence of these codons determines the sequence of amino acids during protein synthesis.

Genome-wide association studies (GWAS)

Association study in which numerous genetic variants across the genome are analysed to measure differences associated with a trait, disease, or phenotype.

Genomic instability

Abnormal rate of genetic change in a cell population which becomes evident as proliferation continues.

Genotoxic

Referring to chemical agents that damage the genetic information within a cell, causing mutations, which may lead to cancer.

Germ cells

The cells that develop into eggs and sperm, through which genetic information is passed from generation to generation.

Germ-line mutation

A mutation occuring in reproductive cells or their precursors that may be transmitted to the organism’s descendants.

Glucose

A six-carbon sugar, the main product of photosynthesis, that is a major energy source for metabolic processes. It is broken down by glycolysis during cellular respiration.

Growth factors

Various chemicals, particularly polypeptides, that have a variety of important roles in the stimulation of cell growth and replication. They bind to cell surface receptors.

Guanine

A purine derivative and one of the four possible nitrogenous bases in nucleotides and nucleic acids (DNA and RNA). Base pairs with cytosine.

Guanosine

A nucleoside consisting of one guanine molecule linked to a ribose sugar molecule in DNA.

Glycaemic index

A measure of the increase in blood glucose (and insulin) after consumption of a standard amount of a food under controlled conditions.

Glycaemic load

The product of multiplying the glycaemic index by the amount of carbohydrate in a food as consumed. The glycaemic load of a diet takes into account the calculated aggregate of the glycaemic loads of the foods constituting that diet.

Haem

The part of the organic molecule haemoglobin in red blood cells containing iron to which oxygen binds for transport around the body.

Hallmarks of cancer

Key phenotypic characteristics in structure and function that represent an essential part of the biology of a cancer cell.

Hazard ratio

A measure of a risk of an outcome (for example, death) associated with an exposure of interest. Hazard ratios do not reflect a time unit of the study, but represent instantaneous risk over the study time period. Hazard ratios are often treated as a ratio of death probabilities.

Head and neck cancer

Includes cancers of the oral cavity, pharynx and larynx, nasal cavity and salivary glands.

Healthy Eating Index-2005

The HEI-2005 score assesses concordance with 2005 Dietary Guidelines for Americans and includes intakes of plant foods, milk, meat, saturated fat, sodium, energy from solid fat, alcohol and added sugar.

Helicobacter pylori (H. pylori)

A gram-negative bacterium that lives in the human stomach. It colonises the gastric mucosa and elicits both inflammatory and lifelong immune responses.

Hepatitis

Inflammation of the liver, which can occur as the result of a viral infection or autoimmune disease, or because the liver is exposed to harmful substances, such as alcohol.

Hepatocellular carcinoma

Primary malignant tumour of the liver.

Hepatocytes

The main cells of the liver.

Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs)

Potentially carcinogenic chemicals formed when muscle meat, including beef, pork, fish or poultry, is cooked using high-temperature methods.

Heterogeneity

A measure of difference between the results of different studies addressing a similar question. In meta-analysis, the degree of heterogeneity may be calculated statistically using the I2 test.

High-income countries

As defined by the World Bank, countries with an average annual gross national income per capita of US$12,236 or more in 2016. This term is more precise than and used in preference to ‘economically developed countries’.           

Histones

Family of proteins held in complexes with DNA in eukaryotic chromatin and chromosomes. Involved in the condensation and coiling of chromosomes during cell division. Chemical modification of histones (methylation and acetylation) is key in suppressing or activing gene activity.

Homeostasis

Regulation of an organism’s internal environment within a controlled range so that physiological processes can proceed at optimum rates.

Homeostatically

The tendency of the body to maintain a condition of balance or equilibrium within its internal environment, even when faced with external changes.

Hormone

A substance secreted by specialised cells that affects the structure and/or function of cells or tissues in another part of the body.

Hormone receptor status

Hormone receptors are proteins found in and on breast or other cells that respond to circulating hormones and influence cell structure or function. A cancer is called oestrogen-receptor-positive (ER+) if it has receptors for oestrogen, and oestrogen-receptor-negative (ER-) if it does not have the receptors for oestrogen.

Hyperinsulinemia

High blood concentrations of insulin.

Hypermethylation

An epigenetic control that leads to gene inactivation in cancer cells by adding methyl groups to DNA sequences, inactivating most important cellular pathways.

Hypomethylation

The loss of the methyl group or the unmethylated state of a site that is normally methylated in DNA sequences. Occurs in mostly repeated sequences and is prevalent in cancer cells as it helps these cells adapt to the tumour microenvironment during metastasis.

Hyperplasia

An increase in the number of cells in a tissue.

Immune response

The production of antibodies or specialised cells, for instance, in response to foreign proteins or other substances.

Immune system

Complex network of cells, tissues, and organs that work together to defend against external agents such as microorganisms.

In vitro

Processes that occur outside the body, in a laboratory apparatus.

In vivo

Describing biological processes as they are observed to occur within living organisms.

Incidence

Frequency of occurrence of new cases of a disease in a particular population during a specified period.

Incidence rates

The number of new cases of a condition appearing during a specified period of time expressed relative to the size of the population; for example, 60 new cases of breast cancer per 100,000 women per year.

Inflammation

The immunologic response of tissues to injury or infection. Inflammation is characterised by accumulation of white blood cells that produce several bioactive chemicals (cytokines), causing redness, pain, heat and swelling. Inflammation may be acute (such as in response to infection or injury) or chronic (as part of several conditions, including obesity).

Insulin

A protein hormone secreted by the pancreas that promotes the uptake and utilisation of glucose, particularly in the liver and muscles. Inadequate secretion of, or tissue response to, insulin leads to diabetes mellitus.

Insulin-like growth factor (IGF)

Polypeptides with high sequence similarity to insulin that are part of a complex system that cells use to communicate with their physiologic environment. IGF-I is the main mediator of growth hormone activity.

Insulin-like growth factor binding proteins (IGFBPs)

A family of proteins that bind to and transport specific IGFs (see insulin-like growth factor) in the circulation. Most circulating IGFs are bound to IGFBPs.

Insulin resistance

A pathological condition in which cells fail to respond normally to the hormone insulin.

Interleukin-6

A cytokine involved in inflammation and infection responses and also in the regulation of metabolic, regenerative and neural processes.

Intracrine

Denoting self-stimulation through cellular production of a factor that acts within the cell.

Invasion

Movement of one cell type into a territory normally occupied by a different cell type.

Ionising radiation

Radiation of sufficiently high energy to cause ionisation in the medium through which it passes. May consist of a stream of high-energy particles (electrons, protons, alpha-particles) or short-wavelength electromagnetic radiation (ultraviolet, X-rays, gamma-rays). It can cause extensive damage to the molecular structure of a substance.

Iron-deficiency anaemia

Anaemia caused by a lack of iron. Anaemia is defined as a decrease in the number of red blood cells or the amount of haemoglobin in the blood.

Isoflavones

Constituent of plants with oestrogen-like properties.

KRAS gene

Provides instructions for making the K-Ras protein, which is involved in cell signalling pathways, cell growth, cell maturation and cell death. Mutated forms are associated with some cancers.

Lactation

The production and secretion of milk by the mammary glands.

Lactose intolerance

The inability to digest lactose, a component of milk and some other dairy products. The basis for lactose intolerance is the lack of an enzyme called lactase in the small intestine.

Large cell carcinoma

A term used to describe a microscopically identified variant of certain cancers, for example, lung cancers, in which the abnormal cells are particularly large.

Lead time bias

Lead time is the time between the detection of a disease (for instance through screening) and its usual clinical presentation. Lead time bias is the spurious apparent improvement in outcome, for example, overall or disease-free survival from diagnosis, following, for example, introduction of screening, without any real change in the natural history of the condition.

Leptin

A hormone secreted by adipose cells that helps to regulate energy balance by inhibiting hunger.

Lesion

A general term for any abnormality of cells or tissues, including those due to cancer.

Less developed regions

As defined by IARC, all regions of Africa, Asia (excluding Japan), Latin America and the Caribbean, Melanesia, Micronesia and Polynesia.

Life course approach

The long-term effects on later health or disease risk of physical or social exposures during pre-conception, gestation, childhood, adolescence, young adulthood and later adult life.

Lipid peroxidation

The oxidative degradation of lipids. It is the process in which free radicals ‘steal’ electrons from the lipids in cell membranes, resulting in cell damage.

Localised cancer

A malignancy limited to the organ of origin.

Low-income countries

As defined by the World Bank, countries with an average annual gross national income per capita of US$1,005 or less in 2016. This term is more precise than and used in preference to ‘economically developing countries’.

Low- and middle-income countries

As defined by the World Bank, low-income countries, are countries with an average annual gross national income per capita of US$1,005 or less in 2016. Middle-income countries, are countries with an average annual gross national income per capita of between US$1,006 and US$12,235 in 2016. These terms are more precise than and used in preference to ‘economically developing countries’.

Macronutrient

The components of the diet that provide energy: protein, carbohydrate and fat.

Macrophage

Large phagocytic cell forming part of the body’s immune system. It can ingest pathogenic microorganisms or cell debris.

Malignancy

A tumour with the capacity to spread to surrounding tissue or to other sites in the body.

Malignant

A tumour with the capacity to spread to surrounding tissue or to other sites in the body.

Maternal programming

The causal influence of the maternal genotype, phenotype or environment on the offspring phenotype. Environmental factors can include the mother nutritional status and body composition before and during pregnancy.

Mediterranean type diet/dietary pattern

It generally describes a diet rich in fruits and vegetables, with modest amounts of meat and dairy, some fish and wine, and rich in unrefined olive oil. Traditionally it is also associated with moderate to high levels of physical activity. Currently most countries around the Mediterranean do not consume such a diet.

Melanoma

Malignant tumour of the skin derived from the pigment-producing cells (melanocytes).

Menarche

The start of menstruation.

Mendelian randomisation

A method of using natural variation in genes of known function to mimic a potential causal effect of a modifiable exposure on disease. The design helps to avoid problems from reverse causation and confounding.

Menopausal hormone therapy (MHT)

Treatment with oestrogens and progesterones with the aim of alleviating menopausal symptoms or osteoporosis. Also known as hormone replacement therapy.

Menopause

The cessation of menstruation.

Messenger ribonucleic acid (mRNA)

RNA molecule responsible for carrying the genetic code transcribed from DNA to specialised sites within the cell (known as ribosomes), where the information is translated into protein composition.

Meta-analysis

The process of using statistical methods to combine the results of different studies.

Metabolic equivalent (MET)

One MET equals the resting metabolic rate, measured as the rate of oxygen consumption, which is approximately 3.5 millilitres of oxygen per kilogram of body weight per minute. Equivalent to physical activity ratio.

Metabolism

The sum of chemical reactions that occur within living organisms.

Metabolites

Various compounds that take part in or are formed by chemical, metabolic reactions.

Metastasis/metastatic spread

The spread of malignant cancer cells to distant locations around the body from the original site.

Microbiome

The community of commensal, symbiotic and pathogenic micro-organisms, including bacteria, archaea, viruses and other microbes, inhabiting an environment such as the gastrointestinal tract.

Micronuclei

Small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division.

Micronutrient

Vitamins and minerals present in foods and required in the diet for normal body function in small quantities conventionally of less than 1 gram per day.

MicroRNA (miRNA)

Small RNA molecule that binds to target mRNA molecules and suppresses the translation of mRNA into the protein, thereby silencing gene expression.

Migrant study

A study of people who migrate from one country to other countries with different environments and cultural backgrounds. The experience, such as mortality or disease incidence, of the migrant group is compared with that of people in their current country of residence and in their country of origin.

Mitogenic

Referring to a chemical substance that encourages a cell to divide, by triggering mitosis. Mitogens are usually proteins. Mitogenesis is the induction (triggering) of mitosis, typically through a mitogen.

Mitogen-activated protein kinase (MAPK) pathway

A chain of proteins that transmits chemical signals from outside the cell to the cell’s nucleus to activate transcription factors that control gene expression.

Moderator analysis

A tool in statistics to determine whether the relationship between an exposure and an outcome is modified by another variable.

Monomeric units

A molecule that can combine with others of the same kind to form a polymer. Glucose molecules, for example, are monomeric units that can combine to form the polymer cellulose.

More developed regions

As defined by IARC, all regions of Europe plus Northern America, Australia, New Zealand and Japan.

Mucinous carcinoma

A type of cancer that begins in cells that line certain internal organs and produce mucin (the main component of mucus).

Mutation

A permanent change in the nucleotide sequence of the genome (an organism's complete set of DNA).

Mycotoxins

Naturally occurring toxins produced by fungi, which grow on a variety of crops and foods, often under warm and humid conditions. They can cause a number of acute and chronic illnesses in humans and other animals.

N-nitroso compound

A substance that may be present in foods treated with sodium nitrate, particularly processed meat and fish. It may also be formed endogenously, for example, from haem and dietary sources of nitrate and nitrite. N-nitroso compounds are known carcinogens.

Nested case-control study

A case-control study in which cases and controls are drawn from the population of a cohort study; often used for studies of prospectively collected information or biological samples.

Neoplasm

A benign or malignant tumour.

Neoplastic

Referring to abnormal new growth of tissue that persists in the absence of the original stimulus.

Neutrophils

A type of white blood cell that fights infection by ingesting microorganisms and releasing enzymes that kill microorganisms.

Nitrosamine

A compound created from a reaction between nitrites and amino compounds, which may occur during meat curing. Many nitrosamines are known carcinogens.

Non-cardia stomach cancer

A subtype of stomach cancer that occurs in the lower portion of the stomach.

Non-communicable diseases (NCDs)

Diseases which are not transmissible from person to person. The most common NCDs are cancer, cardiovascular disease, chronic respiratory diseases, and diabetes.

Non-linear analysis

A non-linear dose–response meta-analysis does not assume a linear dose–response relationship between exposure and outcome. It is useful for identifying whether there is a threshold or plateau.

Nucleotide

Organic compound consisting of a nitrogen-containing purine or pyrimidine base linked to a sugar (ribose or deoxyribose) and phosphate group.

Nutrient

A substance present in food and required by the body for maintenance of normal structure and function, and for growth and development.

Nutrition

Process by which organisms obtain energy and nutrients (in the form of food and drink) for growth, maintenance and repair.

Nutrition transition

The phenomenon whereby patterns of food consumption and physical activity in low- and middle-income countries shift from traditional ways of life and plant-based diets low in processed foods to more Western diets with more processed foods high in sugars and fat, more food from animal sources, less physical activity and more sedentary time. These patterns contribute to escalating rates of overweight, obesity and non-communicable disease.

Obesity

Excess body fat to a degree that increases the risk of various diseases. Conventionally defined as a BMI of 30 kg/m2 or more. Different cut-off points have been proposed for specific populations.

Obesity stigma

Actions against people living with obesity that can cause exclusion and marginalisation and lead to inequities; particularly in workplace or healthcare settings and in the media.

Odds ratio

A measure of the risk of an outcome such as cancer, associated with an exposure of interest, used in case-control studies; approximately equivalent to relative risk.

Oestradiol

The principal female sex hormone produced mainly by the ovaries before menopause and by adipose tissue after. It promotes the onset of secondary sexual characteristics and controls the menstrual cycle.

Oestrogen

The female sex hormones, produced mainly by the ovaries during reproductive life and also by adipose tissue.

Oligosaccharide

A compound comprising between 3 and 10 simple sugar molecules (monosaccharides).

Oncogene

Dominant mutant allele of a cellular gene that disrupts cell growth and division and is capable of transforming a normal cell into a cancerous cell.

Oral cavity cancer

Cancers of the oral cavity include malignancies of the lips, tongue, inside lining of the cheeks (buccal mucosa), floor of the mouth, gums (gingiva), palate and salivary glands. Most studies in this report excluded cancer of the lip and salivary glands.

Osteoporosis

A disease in which the density and quality of bone are reduced.

Oxidative damage

Damage to cells or structures in cells caused by oxidation, either by chemicals or by radiation. Some oxidants are generated in the normal course of metabolism. Oxidation of DNA is one cause of mutation.

Oxidative stress

Overproduction of reactive oxygen species that may damage tissues.

p53

A protein central to regulation of cell growth. Mutations of the p53 gene are important causes of cancer.

Papillary renal cell carcinoma

A type of cancer that forms inside the lining of the kidney tubules.

Paracrine

Type of cell signalling in which the target cell is close to the cell releasing the signal. Paracrine signals include neurotransmitters and neurohormones.

Pasteurisation

Partial sterilisation of foods at a temperature that destroys microorganisms such as bacteria, viruses, moulds, yeast and protozoa without major changes in the chemistry of the food.

Pathogenesis

The origin and development of disease. The mechanisms by which causal factors increase the risk of disease.

Peptide

Any group of organic compounds comprising two or more amino acids linked by peptide bonds.

Peer review

The scrutiny of scientific papers by one or more suitably qualified scientists.

Pharmaceuticals

More commonly known as medicines or drugs, are used to diagnose, cure, treat or prevent disease.

Phase I metabolising enzyme

Enzymes in the first phase of detoxification (modification) that introduce reactive and polar groups.

Phase II metabolising enzyme

Enzymes in the second phase of detoxification (conjugation) that conjugate active substances from phase one to charged species that are more easily excreted, for example, in bile.

Pharyngeal cancer

Cancer of the pharynx includes tumours of the nasopharynx, the oropharynx (including tonsils) and the hypopharynx.

Phenotype

The observable characteristics displayed by an organism; depends on both the genotype (the genetic makeup of a cell) and environmental factors.

Phosphatidylinositol 3-kinase (PI3K) pathway

Pathway essential for the normal development of many parts of the body. This signalling pathway influences many critical cell functions, including the synthesis of new proteins, cell growth and division (proliferation), and cell survival.

Physical activity

Any movement using skeletal muscles that requires more energy than resting.

Phytochemicals

Non-nutritive bioactive plant substances that may have biological activity in humans.

Point estimate

An estimate that is reported as a single value. The precision of a point estimate is indicated by the width of the confidence interval that surrounds it.

Policy

A course of action taken by a governmental body including, but not restricted to, legislation, regulation, guidelines, decrees, standards, programmes and fiscal measures. Policies have three interconnected and evolving stages: development, implementation and evaluation. Policy development is the process of identifying and establishing a policy to address a particular need or situation. Policy implementation is a series of actions taken to put a policy in place, and policy evaluation is the assessment of how the policy works in practice.

Polymorphisms

Common variations (in more than one per cent of the population) in the DNA sequence of a gene.

Polyunsaturated fatty acids (PUFAs)

Fatty acids containing two or more double bonds.

Pooled analysis

In epidemiology, a type of study in which original individual-level data from two or more original studies are obtained, combined and re-analysed.

Prevalence

The total number of individuals who have a characteristic, disease or health condition at a specific time, related to the size of the population, for example, expressed as a percentage of the population.

Processed meat

Meats transformed through salting, curing, fermentation, smoking or other processes to enhance flavour or improve preservation (see Exposures: Meat, fish and dairy products).

Progesterone

Female sex hormone, produced mainly by the ovaries during reproductive life and by the placenta during pregnancy.

Proliferation

Increase in the number of cells, for example, in a tissue.

Prostaglandins

A group of physiologically active lipid compounds having diverse hormone-like effects in animals.

Protein

Polymer of amino acids linked by peptide bonds in a sequence specified by mRNA with a wide variety of specific functions including acting as enzymes, antibodies, storage proteins and carrier proteins.

Proto-oncogene

Gene involved in regulation of cell proliferation which, if mutated or overexpressed, has the capacity to cause oncogenesis.

Publication bias

A bias in the overall balance of evidence in the published literature due to selective publication. Not all studies carried out are published, and those that are may differ from those that are not. The likelihood of publication bias can be tested, for example, with either Begg’s or Egger’s tests.

Randomised controlled trial (RCT)

A study in which a comparison is made between one intervention (often a treatment or prevention strategy) and another (control). Sometimes the control group receives an inactive agent (a placebo). Groups are randomised to one intervention or the other, so that any difference in outcome between the two groups can be ascribed with confidence to the intervention. Sometimes, neither investigators nor subjects know to which intervention they have been randomised; this is called ‘double-blinding’.

Reactive nitrogen species (RNS)

Nitrogen-containing radical species or reactive ions, such as nitric oxide (NO) and peroxynitrite (ONOO-), which are able to damage DNA, such as by inducing DNA strand breaks or base modifications.

Reactive oxygen species (ROS)

Oxygen-containing radical species or reactive ions that can oxidise DNA (remove electrons), for example, hydroxyl radical (OH–), hydrogen peroxide (H2O2) or superoxide radical (O2–).

Receptor

Protein on the surface of a cell that binds to a circulating substance (ligand) to initiate the transmission of messages to the inside of the cell.

Recessive mutation

A pattern of inheritance in which an individual expresses the mutation only if both copies of the gene are mutant.

Rectum

The final section of the large intestine, terminating at the anus.

Regionalised cancer

Tumour extension beyond the limits of the organ of origin without being distant.

Regulatory region

DNA sequence upstream of a coding region to which molecules such as transcription factors bind and regulate gene expression.

Relative risk (RR)

The ratio of the rate of an outcome (for example, disease (incidence) or death (mortality)) among people exposed to a factor, to the rate among the unexposed, usually used in cohort studies.

Resting metabolic rate

Metabolic rate in a fasting subject sitting quietly (also see basal metabolic rate).

Resilience

Property of a tissue or of a body to resume its former condition after being stressed or disturbed.

Retinoid

Compounds chemically related to or derived from vitamin A. They may be used for treatment of some cancers.

Reverse causality

When the true relationship between two variables is actually occurring in the opposite direction to how they are being studied; instead of the exposure leading to the outcome, the variable being measured as the outcome is causing the variable being measured as the exposure.

Ribonucleic acid (RNA)

The molecule created by RNA polymerase from DNA (transcription), which carries the genetic message to ribosomes (translation), where proteins are made.

Review of published reviews

A form of research synthesis which seeks to identify, appraise, and interpret published reviews on a specific topic or set of topics, creating a summary ‘overview’. This is in contrast to systematic reviews, which seek to identify, appraise and interpret primary studies on a specific topic or set of topics.

Sarcopenia

Loss of skeletal mass normally seen in association with ageing.

Saturated fatty acids

Fatty acids that do not contain any double bonds.

Satiation

The desire to stop eating, terminating the current meal.

Satiety

The lack of desire to start eating.

Selection bias

Bias arising from the procedures used to select study participants and from factors influencing participation.

Selenoproteins

Any protein which includes a selenocysteine residue, a selenium-containing amino acid.

Short chain fatty acids

Fatty acids with fewer than six carbon atoms, which are produced when bacteria ferment fibre in the colon.

Single nucleotide polymorphisms (SNPs)

Variation in the base sequence occurring at a given single position or nucleotide in the genome, found in more than 1 per cent of the population. This is the most common form of genetic variation among people.

Sister chromatid exchanges

The exchange of genetic material between two identical sister chromatids.

Socioeconomic status

A combined product of social and economic status reflecting education level, personal wealth, class and associated factors.

Squamous cell carcinoma

A malignant cancer derived from squamous epithelial cells.

Statistical power

The power of any test of statistical significance, defined as the probability that it will reject a false null hypothesis.

Statistical significance

The probability that any observed result has or has not occurred by chance. Conventionally, a probability of less than five per cent (p < 0.05) that a study result has occurred by chance is considered ‘statistically significant’ (see confidence interval).

Stem cell

Cell that is not differentiated but can undergo unlimited division to form other cells, which can either remain stem cells or differentiate to form specialised cells.

Steroid hormones

Group of structurally related hormones synthesised from cholesterol that control various physiological functions.

Stress

A state of physiological or psychological strain caused by adverse stimuli that tends to disturb the functioning of an organism.

Stromal cells

Connective tissue cells of an organ.

Substrate

Substance upon which an enzyme acts in biochemical reactions; basic chemical building block of biochemical pathways.

Survival rate

The percentage of people in a study or treatment group who are still alive for a certain period of time after they were diagnosed with or started treatment for a disease.

System

Set or series of interconnected or interdependent cells or organs that act together in a common purpose or produce results impossible to achieve by the action of one alone.

Systematic literature review (SLR)

A means of compiling and assessing published evidence that addresses a scientific question with a predefined protocol and transparent methods.

Systemic

Describing something that occurs throughout the body, not just locally.

Telomeres

Region of repetitive DNA at the end of a chromosome, which protects it from destruction during DNA replication.

Thymine

A pyrimidine derivative and one of the four possible nitrogenous bases in nucleotides and nucleic acids (DNA and RNA). Base pairs with adenine.

Tissue

A collection of one or more types of cells of similar structure organised to carry out particular functions.

Tocopherol

A form of vitamin E.

Transcription

The process in living cells in which the genetic information of DNA is transferred to a molecule of messenger RNA (mRNA) as the first step in protein synthesis. Takes place in the cell nucleus or nuclear region and is regulated by transcription factors.

Transcription factor

Any group of proteins that work synergistically to regulate gene activity by increasing or decreasing the binding of RNA polymerases to the DNA molecule during transcription.

Transitional cell carcinomas

Cancer that develops in the lining of the renal pelvis, ureter or bladder.

Translate

Process in living cells in which the genetic information encoded in mRNA in the form of a sequence of nucleotide triplets (codons) is translated into a sequence of amino acids in a polypeptide chain during protein synthesis. Takes place in ribosomes in the cell cytoplasm.

TP53

Protein that acts as a tumour suppressor, which means it regulates cell division by keeping cells from growing and dividing (proliferating) too quickly or in an uncontrolled way. TP53 is the most commonly mutated gene in human cancer.

Tumorigenesis

The process of tumour development.

Tumour

A mass of neoplastic and other cells.

Tumour initiator

An agent that damages cellular DNA, a necessary condition for the production of a new tumour.

Tumour necrosis factor

A cell-signalling protein involved in inflammation that can cause cell death.

Tumour promoter

A chemical, complex of chemicals or biological agent that promotes a later stage of carcinogenesis, called tumour promotion, by altering expression of the genetic information, rather than altering the structure of DNA.

Tumour suppressor gene

A gene that protects a cell from one step on the path to cancer. When this gene mutates to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes.

Upper aerodigestive tract cancer

Cancers of the upper aerodigestive tract (UADT) include head and neck cancers and oesophageal cancers.

Visceral obesity

Form of obesity due to excessive deposition of fat in the omentum and around the abdominal viscera, rather than subcutaneously (peripheral obesity). Poses a greater risk of diabetes mellitus, hypertension, metabolic syndrome and cardiovascular disease than peripheral obesity.

Vitamin

One of a number of organic compounds required from food or drink by living organisms in relatively small amounts to maintain normal structural function.

Waist–hip ratio (WHR)

A measure of body shape indicating central (abdominal) fat distribution.

WCRF/AICR score

The WCRF/AICR score was constructed on the basis of the WCRF/AICR Recommendations on weight management, physical activity, foods and drinks that promote weight gain, plant foods, animal foods, alcoholic drinks and breastfeeding (in women).

Weight bias

Negative attitudes and beliefs about others because of their weight. These are manifested as stereotypes and prejudice towards, and stigmatisation of people living with overweight and obesity (see obesity stigma).

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