Researchers in Sweden investigated the relationship between vitamin D and breast cancer risk, and how that risk is modified by genetics.
Less than 10% of breast cancers are considered hereditary and only 3-4% of breast cancers are linked to known breast cancer genes. More recent studies have uncovered genetic changes that may be associated with breast cancer. These changes, called single-nucleotide polymorphisms (SNPs), may account for up to 14% of hereditary breast cancer.
Previous ecological and epidemiological studies suggest that higher levels of vitamin D may have a positive effect on breast cancer risk and survival. However, the results of many of these studies are conflicting. Results from studies examining genetic changes in the vitamin D receptor gene and its relationship to breast cancer risk have also been inconsistent.
A Swedish study published led by Linnea Huss in Breast Cancer Research recently investigated breast cancer risk in 20 single-nucleotide polymorphisms identified as affecting vitamin D levels. The current study used data from the Malmö Diet and Cancer Study, which was conducted between 1991 and 1996 in Malmö, Sweden. All residents born between 1923 and 1950 were invited to participate. Participants gave blood samples, underwent physical examinations, and provided information on lifestyle and reproductive factors through questionnaires.
Using information from the Malmö Diet and Cancer Study, the current study identified women with and without breast cancer. Investigators collected genetic data from samples from these women along with vitamin D information. Overall, 700 women with breast cancer and 643 women without breast cancer were included in the study.
A single-nucleotide polymorphism (SNP) is a variation in the genetic code of DNA. This study investigated SNPs that were already identified to be associated with Vitamin D levels. First, they confirmed that most of the single-nucleotide polymorphisms tested were significantly linked to vitamin D levels. Then, they were able to identify a few specific single-nucleotide polymorphisms that were linked to a lower risk of breast cancer.
Overall, vitamin D may change the risk of breast cancer associated with certain single-nucleotide polymorphisms. Each person’s specific genetic composition may affect how much vitamin D levels are related to breast cancer risk. More research is needed to understand the complex association between vitamin D and breast cancer.
Written by Cindi A. Hoover, PhD
Reference: Huss L, Butt ST, Almgren P, Borgquist S, Brandt J, Försti A, Melander O, Manjer J. SNPs related to vitamin D and breast cancer risk: a case-control study. Breast Cancer Research; 2018. 20:1-13.