Influence of the C161T but not Pro12Ala polymorphism in the peroxisome proliferator‐activated receptor‐gamma on colorectal cancer in an Indian population

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Abstract
The aim of the present study was to investigate associations between Pro12Ala and C161T polymorphisms in the peroxisome proliferator‐activated receptor‐gamma (PPAR‐γ) gene and colorectal cancer (CRC) risk. We recruited 301 newly diagnosed CRC patients and 291 healthy control subjects at the Madras Cancer Institute in Chennai, India, from 1999 to 2001. Genotypes of the Pro12Ala and C161T polymorphisms were determined using the PCR‐RFLP method. After adjustment for age, sex, smoking habit, family history and family income, an increased risk of CRC was observed for the C/T + T/T genotype compared to the C/C genotype of the C161T polymorphism (odds ratio = 1.61, 95% confidence interval: 1.10–2.36), whereas no significant association was found for Pro12Ala (odds ratio = 1.06, 95% confidence interval: 0.70–1.61). Analysis with estimated haplotypes showed a significant difference in haplotype frequencies between cases and controls (χ2 = 11.62, P = 0.009, d.f. = 3). The relationship between the two polymorphisms and CRC risk was not significantly modified by dietary intake of fish. Although the biological mechanisms of the observed association remain to be elucidated, our findings suggest that the C161T polymorphism of the PPAR‐γ gene is related to risk of CRC. Further research is needed to investigate functional implications of polymorphisms of the PPAR‐γ gene in CRC development. (Cancer Sci 2005; 96: 507 –512)