Grant: Master's Award: Canada Graduate Scholarships

Breast cancer is currently the most common cancer and a leading cause of death among women in Canada. Evidence from previously conducted studies have shown a somewhat consistent relationship between vitamin D deficiency and increased risk for breast cancer, but the exact underlying biological mechanism for the protective action of vitamin D is unknown. Vitamin D signalling is essential in the control of cell proliferation, differentiation and apoptosis, and in estrogen synthesis and signalling in the breast tissue. Polymorphisms in the VDR gene, which encodes for the vitamin D receptor, may result in the formation of receptors that have impaired ability to bind to circulating vitamin D, or to other molecules in the signalling pathway that are critical for eliciting a biological response. The relationship between polymorphisms in the VDR gene and breast cancer risk has rarely been considered in previous studies, and results from these have been inconsistent. Data already available from a case-control study conducted in Vancouver, British Columbia and Kingston, Ontario will be used in this study to examine the associations between 24 single nucleotide polymorphisms (SNPs) of the VDR gene with breast cancer risk. Women aged 40-80 with in situ or invasive breast cancer were identified as cases, and age-frequency matched cancer-free women participated as controls, where one-third of participants are of Asian descent. DNA was collected and isolated, and SNP genotyping was performed in a custom Illumina array. Questionnaire data allows for adjustment for demographic, lifestyle and reproductive factors as potential confounders, and ethnicity and menopausal status as effect modifiers. This study will produce new knowledge on the role of vitamin D genetic pathways in breast tumorigenesis and is unique in being able to investigate new potential genetic susceptibility factors among those of both European and Asian descent.