NUTRICASUS
NUTRICASUS
Le Journal de la Médecine Nutritionnelle et Fonctionnelle Pratique
OnconScreen : Basé sur l’Evidence et le Bon Sens
Overview of genes, diet and cancer.
Mathers JC., Genes Nutr. 2007 Oct;2(1):67-70.
Quantitative epidemiological analysis suggests that about one third of the variation in cancer risk can be attributed to variation in dietary
exposure but it has proved difficult, using conventional epidemiological approaches, to identify which dietary components, in what
amounts and over what time-scales are protective or potentially hazardous. Work in this area has been hampered by the lack of robust
surrogate endpoints. However, the rapidly accumulating knowledge of the biological basis of cancer and the application of post-genomic
technologies are helping the development of novel biomarkers of cancer risk. Genomic damage resulting in aberrant gene expression is
the fundamental cause of all cancers. Such damage includes mutations, aberrant epigenetic marking, chromosomal damage and
telomere shortening. Since both external agents and normal cell functions, such as mitosis, subject the genome to frequent and diverse
insults, the human cell has evolved a battery of defence mechanisms which (a) attempt to minimize such damage (including inhibition of
oxidative reactions by free radical scavenging and the detoxification of potential mutagens), (b) repair the damage or (c) remove severely
damaged cells by shunting them into apoptosis. When such defences fail and a tumour becomes established, further genomic damage
and further alterations in gene expression enable the tumour to grow, to cope with anoxia, to develop a novel blood supply
(angiogenesis), to escape from the confines of its initiation site and to establish colonies elsewhere in the body (metastasis). All of these
processes are potentially modifiable by food components and by nutritional status. In addition, interactions between dietary (and other
environmental and lifestyle) factors and genetic make-up [seen principally in the assembly of single nucleotide polymorphisms (SNPs)
which is unique to each individual] contributes to interindividual differences in cancer risk.
8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis.
Valavanidis A, Vlachogianni T, Fiotakis C.
J Environ Sci Health C Environ Carcinog Ecotoxicol Rev. 2009 Apr;27(2):120-39.
There is extensive experimental evidence that oxidative damage permanently occurs to lipids of cellular membranes, proteins, and DNA.
In nuclear and mitochondrial DNA, 8-hydroxy-2' -deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2' -deoxyguanosine (8-oxodG) is one of
the predominant forms of free radical-induced oxidative lesions, and has therefore been widely used as a biomarker for oxidative stress
and carcinogenesis. Studies showed that urinary 8-OHdG is a good biomarker for risk assessment of various cancers and degenerative
diseases. The most widely used method of quantitative analysis is high-performance liquid chromatography (HPLC) with electrochemical
detection (EC), gas chromatography-mass spectrometry (GC-MS), and HPLC tandem mass spectrometry. In order to resolve the
methodological problems encountered in measuring quantitatively 8-OHdG, the European Standards Committee for Oxidative DNA
Damage was set up in 1997 to resolve the artifactual oxidation problems during the procedures of isolation and purification of oxidative
DNA products. The biomarker 8-OHdG or 8-oxodG has been a pivotal marker for measuring the effect of endogenous oxidative damage
to DNA and as a factor of initiation and promotion of carcinogenesis. The biomarker has been used to estimate the DNA damage in
humans after exposure to cancer-causing agents, such as tobacco smoke, asbestos fibers, heavy metals, and polycyclic aromatic
hydrocarbons. In recent years, 8-OHdG has been used widely in many studies not only as a biomarker for the measurement of
endogenous oxidative DNA damage but also as a risk factor for many diseases including cancer.
Dietary intakes of omega-6 and omega-3 polyunsaturated fatty acids and the risk of breast cancer.
Thiébaut AC, Chajès V, Gerber M, Boutron-Ruault MC, Joulin V, Lenoir G, Berrino F, Riboli E, Bénichou J, Clavel-Chapelon F.
Int J Cancer. 2009 Feb 15;124(4):924-31.
Experimental studies suggest detrimental effects of omega-6 polyunsaturated fatty acids (PUFA), and beneficial effects of omega-3
PUFAs on mammary carcinogenesis, possibly in interaction with antioxidants. However, PUFA food sources are diverse in human diets
and few epidemiologic studies have examined whether associations between dietary PUFAs and breast cancer risk vary according to food
sources or antioxidant intakes. The relationship between individual PUFA intakes estimated from diet history questionnaires and breast
cancer risk was examined among 56,007 French women. During 8 years of follow-up, 1,650 women developed invasive breast cancer.
Breast cancer risk was not related to any dietary PUFA overall; however, opposite associations were seen according to food sources,
suggesting other potential effects than PUFA per se. Breast cancer risk was inversely associated with alpha-linolenic acid (ALA) intake
from fruit and vegetables [highest vs. lowest quintile, hazard ratio (HR) 0.74; 95% confidence interval (CI) 0.63, 0.88; p trend < 0.0001],
and from vegetable oils (HR 0.83; 95% CI 0.71, 0.97; p trend 0.017). Conversely, breast cancer risk was positively related to ALA intake
from nut mixes (p trend 0.004) and processed foods (p trend 0.068), as was total ALA intake among women in the highest quintile of
dietary vitamin E (p trend 0.036). A significant interaction was also found between omega-6 and long-chain omega-3 PUFAs, with breast
cancer risk inversely related to long-chain omega-3 PUFAs in women belonging to the highest quintile of omega-6 PUFAs (p interaction
0.042). These results emphasize the need to consider food sources, as well as interactions between fatty acids and with antioxidants,
when evaluating associations between PUFA intakes and breast cancer risk.
Vitamin D for cancer prevention: global perspective.
Garland CF, Gorham ED, Mohr SB, Garland FC. Ann Epidemiol. 2009 Jul;19(7):468-83.
PURPOSE: Higher serum levels of the main circulating form of vitamin D, 25-hydroxyvitamin D (25(OH)D), are associated with
substantially lower incidence rates of colon, breast, ovarian, renal, pancreatic, aggressive prostate and other cancers. METHODS:
Epidemiological findings combined with newly discovered mechanisms suggest a new model of cancer etiology that accounts for these
actions of 25(OH)D and calcium. Its seven phases are disjunction, initiation, natural selection, overgrowth, metastasis, involution, and
transition (abbreviated DINOMIT). Vitamin D metabolites prevent disjunction of cells and are beneficial in other phases.
RESULTS/CONCLUSIONS: It is projected that raising the minimum year-around serum 25(OH)D level to 40 to 60 ng/mL (100-150
nmol/L) would prevent approximately 58,000 new cases of breast cancer and 49,000 new cases of colorectal cancer each year, and three
fourths of deaths from these diseases in the United States and Canada, based on observational studies combined with a randomizedtrial.
Such intakes also are expected to reduce case-fatality rates of patients who have breast, colorectal, or prostate cancer by half. There are
no unreasonable risks from intake of 2000 IU per day of vitamin D(3), or from a population serum 25(OH)D level of 40 to 60 ng/mL. The
time has arrived for nationally coordinated action to substantially increase intake of vitamin D and calcium.
Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial.
Clark LC, Dalkin B, Krongrad A, Combs GF Jr, Turnbull BW, Slate EH, Witherington R, Herlong JH, Janosko E, Carpenter D, Borosso C,
Falk S, Rounder J
Br J Urol 1998 May;81(5):730-4
OBJECTIVE: To test if supplemental dietary selenium is associated with changes in the incidence of prostate cancer. PATIENTS AND
METHOD: A total of 974 men with a history of either a basal cell or squamous cell carcinoma were randomized to either a daily
supplement of 200 microg of selenium or a placebo. Patients were treated for a mean of 4.5 years and followed for a mean of 6.5 years.
RESULTS: Selenium treatment was associated with a significant (63%) reduction in the secondary endpoint of prostate cancer incidence
during 1983-93. There were 13 prostate cancer cases in the selenium-treated group and 35 cases in the placebo group (relative risk,
RR=0.37, P=0.002). Restricting the analysis to the 843 patients with initially normal levels of prostate-specific antigen (< or = 4
ng/mL),only four cases were diagnosed in the selenium-treated group and 16 cases were diagnosed in the placebo group after a 2 year
treatment lag, (RR=0.26 P=0.009). There were significant health benefits also for the other secondary endpoints of total cancer mortality,
and the incidence of total, lung and colorectal cancer. There was no significant change in incidence for the primary endpoints of basal and
squamous cell carcinoma of the skin. In light of these results, the 'blinded' phase of this trial was stopped early. CONCLUSIONS: Although
selenium shows no protective effects against the primary endpoint of squamous and basal cell carcinomas of the skin, the selenium-
treated group had substantial reductions in the incidence of prostate cancer, and total cancer incidence and mortality that demand further
evaluation in well-controlled prevention trials.
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