Resveratrol and STAT inhibitor enhance autophagy in ovarian cancer cells.

P Zhang,Y Zhang,J Liu,L-X Zhong,Q-Y Kong,M-L Wu,Y-N Liu,X-Y Chen,H Li

doi:10.1038/cddiscovery.2015.71

Abstract

Autophagic activity reflects cellular response to drug treatment and can be regulated by STAT3 signaling. Resveratrol inhibits STAT3 activation and causes remarkable growth arrest and cell death of ovarian cancer (OC) cells. However, the autophagic status and its relevance with resveratrol’s anti-OC effects remain unclear. We analyzed the states of autophagic activities, the nature of autophagosomes and the levels of autophagy-related proteins (LC-3, Beclin 1 and STAT3) in resveratrol-treated CAOV-3 and OVCAR-3 OC cells using multiple approaches. We elucidated the correlation of STAT3 inhibition with autophagic activity by treating OC cells with an upstream inhibitor of STAT proteins, AG490. Resveratrol efficiently suppressed growth, induced apoptosis and inactivated STAT3 signaling of the two OC cell lines. We found enhanced autophagic activity accompanied with Beclin-1 upregulation and LC3 enzymatic cleavage in resveratrol-treated OC cells. Immunofluorescent (IF) microscopic and IF-based confocal examinations demonstrated the accumulation of cytoplasmic granules co-labeled with LC3 and cytochrome C in resveratrol- or AG490-treated OC cells. Using electron microscopy, we confirmed an increase in autophagosomes and mitochondrial spheroids in either resveratrol- or AG490-treated OC cells. This study demonstrates the abilities of resveratrol to enhance apoptotic and autophagic activities in OC cells, presumably via inactivating STAT3 signaling. Resveratrol or the selective JAK2 inhibitor also leads to mitochondrial turnover, which would be unfavorable for OC cell survival and sensitize OC cells to resveratrol.

Highlights

Ovarian cancer (OC) is one of the commonest female malignancies with an extremely poor prognosis.[1,2,3] Surgical treatment is the first choice for removing OCs in cases that are well-differentiated, relatively small, or confined to the ovary.[4,5] the majority of OC patients (75%) are diagnosed at advanced stages because of the subtle symptoms at the early stages of ovarian carcinogenesis.[6]
Received 22 October 2015; revised 25 November 2015; accepted 4 December 2015; Edited by N Barlev the growth of all three OC cells was significantly suppressed Inactivated STAT3 signaling in resveratrol-suppressed OC cells (P o 0.01) by 100 μM resveratrol in time-related pattern in Immunocytochemical staining demonstrated that p-STAT3 was comparison with that of their normally cultured counterparts distributed in either cytoplasm or the nuclei of the two OC cell (Figures 1b and c)
Resveratrol-enhanced autophagic activities To elucidate the status of autophagy in OC cells and its relevance with resveratrol-caused cell crisis, double immunoflorescent staining for LC3 and Beclin-1 was conducted on the cell-bearing coverslips, which showed that these two proteins were weakly labeled in normally cultured OC cells and became enhanced especially for LC3 after being treated by 120 μM resveratrol for 48 h (Figure 3a)

Summary

Introduction

Ovarian cancer (OC) is one of the commonest female malignancies with an extremely poor prognosis.[1,2,3] Surgical treatment is the first choice for removing OCs in cases that are well-differentiated, relatively small, or confined to the ovary.[4,5] the majority of OC patients (75%) are diagnosed at advanced stages because of the subtle symptoms at the early stages of ovarian carcinogenesis.[6]. Drug resistance often occurs among OC patients and severe toxic effects caused by conventional anticancer drugs greatly reduce patients’ quality of life.[9,10,11] It is urgent to explore more effective and less toxic agents with clearer molecular targets for better adjuvant management of OCs

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Conclusion