CDK4 and neoplasm: In fact, in vitro studies have demonstrated the anti-tumour effect of 800 μM melatonin for 72 h, as it is able to inhibit tumour growth through the downregulation of cyclin-dependent kinases 2 and 4 (CDK2 and CDK4) in ovarian cancer cell lines PA-1 and OVCAR-429 [158].