Nobiletin (NOB) suppresses autophagic degradation via over-expressing AKT pathway and enhances apoptosis in multidrug-resistant SKOV3/TAX ovarian cancer cells

Chemotherapy could be used as an effective therapeutic treatment for ovarian cancer and subsequent peritoneal metastasis. However, the occurrence of drug resistance reduced the treatment effect originated from cancer chemotherapy. Accumulating evidences indicated the significant role of autophagy in tumor cell resistance to chemotherapy. Thus, inhibition of autophagy using natural compounds could be a promising candidate to overcome multidrug resistance in human ovarian cancer cells. Nobiletin (NOB), a polymethoxyflavonoid found in citrus fruits such as Citrus depressa and Citrus reticulate, exhibits a number of bioactivities. In the present study, NOB selectively suppressed the growth and proliferation of human SKOV3/TAX cells, inducing G0/G1 phase arrest and reducing G2/M phase, along with the increase of p53 and p21. In addition, NOB induced significant apoptosis in SKOV3/TAX cells through the intrinsic apoptosis pathway, as evidenced by the up-regulation of cleaved Caspase-9/-3 and PARP. Further, NOB impaired the autophagic degradation in SKOV3/TAX cells, resulting in autophagic flux inhibition. Moreover, the impaired autophagic flux enhanced NOB-induced apoptosis in SKOV3/TAX cells. Importantly, AKT signaling was activated by NOB, which was involved in autophagic degradation and apoptotic cell death. In conclusion, the findings here supplied the illustration that NOB could overcome multidrug resistance in human ovarian cancer cells through AKT-regulated suppression of autophagic degradation.