Joint effects between urinary selenium and polymorphisms in methylation related genes on breast cancer risk.

The aim of this study was to explore the associations of urinary selenium and polymorphisms in methylation related genes with breast cancer risk and the interactions on the risk. The present study involved in 240 female patients with incident breast cancer and 246 age-matched controls in two affiliated hospitals of Sun Yat-sen University in Guangzhou, China, from October 2009 to July 2010. DNMT1 rs2228611, MTHFR rs1801133, and MTR rs1805087 were genotyped using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry platform. Urinary concentration of selenium was measured by inductively coupled plasma mass spectrometry. Women with urinary selenium in the second tertile had a significant reduced breast cancer risk compared to those with urinary selenium in the lowest tertile [OR (95%CI): 0.50 (0.30, 0.81)]. DNMT1 rs2228611, MTHFR rs1801133, and MTR rs1805087 were not associated with breast cancer risk. Women with the third tertile of urinary selenium had a significant reduced breast cancer risk compared to those with the lowest tertile among women only with CC genotype [OR (95%CI): 0.55 (0.30, 1.00)] but not CT/TT genotypes [OR (95%CI): 1.58 (0.73, 3.42)] of MTHFR rs1801133 (P for interaction=0.044). Our results suggested that selenium was associated with a decreased risk of breast cancer and this beneficial effect was limited to women with CC genotype of MTHFR rs1801133.