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 mediatedvia its two receptors, mtnr1a and mtnr1b, is to mediate dark signals in additionto anti-oxidation, immune system enhancement, protection from radiation, and anti-cancerfunctions. a common single nucleotide polymorphism in the mtnr1b gene isrs#10830963, which is well known as a risk factor for type 2 diabetes mellitus. this studyintends to figure out the role of melatonin and its receptor mtnr1b gene rs#10830963polymorphism in breast cancer incidence, diagnosis and prognosis.methods: this study included 43 females with breast cancer and 45 apparently normalhealthy females. restriction fragment length polymorphism-pcr was used for amplificationand genotyping of the mtnr1b gene rs#10830963 polymorphism in whole blood. serummelatonin levels were measured using a ready-for-use radioimmunoassay kit.results: for the mtnr1b gene rs#10830963 polymorphism, we observed asignificantly 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 afrequency of 11.6% for the cc genotype and 16.3% for the cg genotype which wassignificantly lower compared to controls that had a 44.4% frequency of the cc genotypeand 42.2% frequency of the cg genotype. the gg genotype had a significant associationwith larger tumor volume (p=0.048). serum melatonin levels were significantly loweramong breast cancer patients than controls. using the roc curve analysis, serummelatonin showed a significant auc (72.6%, p < 0.001) with diagnostic sensitivity of91.1% and specificity of 58% at a cut-off level of 39.5 pg/ml. females with serummelatonin levels ?39.5pg/ml were at significantly increased risk for breast cancerincidence by about 15 times more than females with levels > 39.5 pg/ml.conclusion: the risk for breast cancer incidence increased as the serum levels ofmelatonin decreased and in females homozygous for the g allele (gg genotype) of themtnr1b gene rs#10830963 polymorphism. the gg genotype was found to be associatedwith increased breast tumor volume as a marker of a poor prognosis breast cancer.