Expression of Serotonin Receptors 5-HT1A, 5-HT1B, 5-HT2B and 5-HT4 in Ovary and in Ovarian Tumours

Background: Recently we have shown that serotonin receptors may be involved in prostate cancer development. In ovarian carcinogenesis, oestrogen may play a role. As oestrogen seems to mediate at least some of its biological effects through serotonin, we decided to evaluate if serotonin receptors are expressed in ovary and in ovarian tumours and if the expression is correlated to ovarian tumour development. Materials and Methods: An immunohistochemical study of the serotonin (5-HT) receptors 5-HTR1A, 5-HTR1B, 5-HTR2B and 5-HTR4 in frozen samples of ovary, and benign, borderline and invasive ovarian tumours was performed. Results: Expression of all four serotonin receptors was strong to intermediate in the ovarian epithelium. In benign and non-invasive cancer cells strong staining was seen, while in invasive cancer cells, decreased expression was observed. For 5-HTR2B, the decrease was correlated to dissemination of the disease. For none of the serotonin receptors was the expression correlated to survival. In the stromal part, a variable immunoreactivity was observed that was strongest for 5-HTR2B in both ovary and tumours. Staining of blood vessels was observed in ovary and all tumour groups for 5-HTR2B, but only occasionally was a weak expression seen for 5-HTR1A, 5-HTR1B and 5-HTR4. Conclusion: The staining pattern of serotonin receptors in ovary indicates their functional role in ovarian physiology. In ovarian tumours, the expression is in harmony with a tumour suppressor role in ovarian carcinogenesis, which is supported by observations in the literature. Further studies are necessary to resolve the connection between serotonin and ovarian tumour development.