Circadian Rhythm and Breast Cancer Susceptibility - A study on PERIODIC3 Gene Polymorphisms in Breast Cancer

Breast Cancer is one of the common cancers that is on the rise globally. Many risk factors have been implicated for the occurrence of the breast cancer. Recent studies show evidence towards a disruption in the circadian rhythm which could be a risk factor towards breast cancer mediated through the altered melatonin secretion which, in turn disrupts the reproductive hormones. PERIODIC 3 gene (Per 3) is one of the circadian rhythm genes that is being studied widely in several disease states. Various factors can disrupt circadian rhythm and alter normal nocturnal production of melatonin and hormonal changes influencing breast cancer aetiology. Our study sought to validate these findings in an Indian population with a case control study of 20 Breast Cancer cases and 10 non-neoplastic controls using breast tissue as our tissue of interest (in contrast to blood as in the Caucasian study). Results: Our study revealed a 55% of the samples with heterozygous alleles of the VNTR polymorphism of Exon 18 of the Per 3 gene amongst Breast Cancer tissue while the remaining 45 % were homozygous 4 repeat sequences. All ten controls that were analysed showed the presence of a 4 repeat homozygous configuration which was statistically significant (p<0.05). This study thus finds a statistically significant correlation between the presence of a heterozygous repeat sequence in Exon 18 of the Per 3 gene and breast carcinoma. However more studies with a larger sample size are required to confirm these findings