C3435T polymorphism in the MDR1 gene and breast cancer risk in northeastern Mexico

The multidrug resistance gene 1 ( ) encodes a membrane-bound phosphoglycoprotein (P-gp). It functions as a transmembrane efflux pump for various structurally unrelated carcinogens and toxins. Polymorphism C3435T of has been investigated for its association with breast cancer in different populations. However, the results are inconsistent and inconclusive. The objective of this study was to determine whether an association exists between the C3435T polymorphism and the risk of breast cancer in a population from northeastern Mexico, which displays ethnic characteristics that differentiate it from other populations of the country. Genotypes were determined for 243 women with histologically confirmed breast cancer and 118 control subjects. Polymorphism of C3435T was analyzed by DNA microarray. We found an increased breast cancer risk associated with CT and CC genotypes (OR = 1.88, 95% CI: 1.04-3.39, P = 0.033 for CT vs. TT; OR = 2.91, 95% CI: 1.48-5.74, P = 0.001 for CC vs. TT). Furthermore, there was significantly increased risk of breast cancer associated with the C allele (OR = 1.59, 95% CI: 1.16-2.18, P = 0.003). In conclusion, we found an association between the C3435T polymorphism and risk of breast cancer in subjects from northeastern Mexico. Identification of inter-individual variability in this polymorphism may be useful for individualizing breast cancer genetic screening and therapeutic intervention.