Introduction: Ovarian cancer is the third common gynaecological malignancy and the leading cause of death in gynaecological cancers. Studies have suggested that changes in circadian rhythms such as bright-light exposure may affect female reproductive physiology. Night shift work is associated with higher risks of breast and endometrial cancer due to lower melatonin production by the pineal gland. Other studies have suggested that the season of birth may be an important environmental risk factor for developing gynaecological cancers. Melatonin is a lipid soluble hormone whose level changes with circadian rhythm. Melatonin has multifaceted functions, including direct free radical scavenging and inhibition of cancer cell growth. However, whether there is an association between the circulating levels of melatonin and the risk of developing ovarian cancer is unclear.
Methods: Serum from women with ovarian cancer or healthy women were collected and the level of melatonin was measured. In addition, the expression of melatonin receptors (MT1 and MT2) were measured in ovarian cancer tissues by immunohistochemistry.
Results:
1. The incidence of ovarian cancer was not associated with the season of birth in women with ovarian cancer.
2. The serum levels of melatonin were significantly lower in women with ovarian cancer compared with healthy women (p<0.05). However, there was no significant difference in melatonin levels among patients who were born in spring, summer, autumn and winter.
3. Immunohistochemistry demonstrated that the expression of melatonin receptors (MT1 and MT2) was reduced in ovarian cancer tissue compared to normal ovary tissues.
Conclusion: Our results demonstrate although there is no association between the season of birth and the risk of developing ovarian cancer, the lower levels of melatonin detected in serum of women with ovarian cancer may contribute to the pathogenesis of ovarian cancer. This further supports that melatonin may be used as an adjuvant in cancer therapy.