Role of Melatonin in Breast Carcinoma: Correlation of Expression Patterns of Melatonin-1 Receptor With Estrogen, Progesterone, and HER2 Receptors

Breast carcinoma is a multifaceted-etiology malignancy. The presence of estrogen (ER), progesterone (PR), and HER2 (human epidermal growth factor receptor 2) receptors in breast carcinoma tissue has therapeutic implications. Recent studies indicate that pineal hormone melatonin by its receptor melatonin 1 (MT1) also influences the development and growth of breast cancer cells. The aim of this cross-sectional study was to elucidate the expression pattern of MT1 receptor in relation to estrogen, progesterone, and HER2 receptors in breast carcinoma. Two groups (receptor positive and triple negative) of breast carcinoma were taken. For comparison, normal mammary tissue was used as control. Immunohistochemistry was carried out using anti-melatonin receptor 1A antibody. Membranous/cytoplasmic expression was seen more than the nuclear expression in the cancerous tissue. Positive correlation of the MT1 expression was seen with ER, PR, and HER 2 receptor. Higher MT1 receptor expression was seen in the receptor-positive cases in comparison with triple-negative cases, which might signify melatonin deficiency in the former, leading to reactive increase in cell receptors. No correlation of MT1 expression with Ki67 index or lymph node status in both receptor-positive and triple-negative cases was found. Normal mammary tissue mainly showed cytoplasmic MT1 immunoreactivity of epithelial cells (ducts and acini), myoepithelial cells, and lining epithelium of blood vessels. Receptor-positive cases would, therefore, benefit from the use of melatonin as supporting therapy. This indicates that melatonin receptor status can be used as an independent pathologic indicator to evaluate breast carcinoma tissue, and melatonin receptor status may help to determine treatment protocols.