a molecular case-control study on the association of melatonin hormone and rs#10830963 single nucleotide polymorphism in its receptor mtnr1b gene with breast cancer

background : the main function of the pineal hormone melatonin which is mediated via its two receptors, mtnr1a and mtnr1b, is to mediate dark signals in addition to anti-oxidation, immune system enhancement, protection from radiation, and anti-cancer functions. a common single nucleotide polymorphism in the mtnr1b gene is rs#10830963, which is well known as a risk factor for type 2 diabetes mellitus. this study intends to figure out the role of melatonin and its receptor mtnr1b gene rs#10830963 polymorphism in breast cancer incidence, diagnosis and prognosis. methods : this study included 43 females with breast cancer and 45 apparently normal healthy females. restriction fragment length polymorphism-pcr was used for amplification and genotyping of the mtnr1b gene rs#10830963 polymorphism in whole blood. serum melatonin levels were measured using a ready-for-use radioimmunoassay kit. results : for the mtnr1b gene rs#10830963 polymorphism, we observed a significantly higher gg genotype frequency among cases (72.1%) than controls (13.3%), with a diagnostic sensitivity of 83.78% and specificity of 76.47%. the cases had a frequency of 11.6% for the cc genotype and 16.3% for the cg genotype which was significantly lower compared to controls that had a 44.4% frequency of the cc genotype and 42.2% frequency of the cg genotype. the gg genotype had a significant association with larger tumor volume (p=0.048). serum melatonin levels were significantly lower among breast cancer patients than controls. using the roc curve analysis, serum melatonin showed a significant auc (72.6%, p39.5 pg/ml. conclusion : the risk for breast cancer incidence increased as the serum levels of melatonin decreased and in females homozygous for the g allele (gg genotype) of the mtnr1b gene rs#10830963 polymorphism. the gg genotype was found to be associated with increased breast tumor volume as a marker of a poor prognosis breast cancer.