Inhibition of IL-6/STAT3 axis and targeting Axl and Tyro3 receptor tyrosine kinases by apigenin circumvent taxol resistance in ovarian cancer cells

Abstract

Abstract.Ovarian cancer is the number one cause of death from gynaecological malignancy. Platinum-based and taxolbased chemotherapy has been used as a standard therapy, but intrinsic and acquired resistance to chemotherapy is a major obstacle to treat the disease. In the present study, we found that in the chemoresistant ovarian cancer SKOV3/TR cells, interleukin-6 (IL-6), IL-6 receptor and signal transducers and activators of transcription 3 (STAT3) expression as well as STAT3 phosphorylation were upregulated compared to those in parental cells. Silencing of IL-6 using IL-6 siRNA was found to suppress IL-6 production, STAT3 and phospho-STAT3 levels, which eventually reduced proliferation and clonogenicity of taxol-resistant SKOV3/TR cells. In addition, stattic, a STAT3 inhibitor, was found to result in decrease of cell viability and clonogenicity of these cells, indicating that the elevated IL-6 and STAT3, phosphoSTAT3 levels are associated with the development of taxol resistance. Next, we found anti-proliferative effect of apigenin on both SKOV3 and SKOV3/TR cells. RT-PCR and western blot results showed that apigenin significantly reduced the expression of Axl and Tyro3 receptor tyrosine kinases (RTKs) at mRNA and protein level, which account for its cytotoxic activity. We further found that apigenin decreased Akt phosphorylation and the level of B-cell lymphoma-extra large (Bcl-xl or BCL2-like 1 isoform 1), an inhibitor of apoptosis. On the contrary to these results, apigenin had no effect on IL-6 production, STAT3 and phosphoSTAT3 protein levels, suggesting that apigenin exerts its anti-proliferative activity via downregulation of Axl and Tyro3 expression, Akt phosphorylation and Bcl-xl expression, but not modulation of IL-6/STAT3 axis. Taken together, our data suggest that inhibition of IL-6/STAT3 signaling pathway and downregulation of Axl and Tyro3 RTKs expression might be a therapeutic strategy to overcome taxol resistance in ovarian cancer cells. IntroductionOvarian cancer is in the fifth place in respect of cancer-related death in woman (1). Worldwide the annual number of new cases and deaths of ovarian cancer is estimated to be around 0.22 and 0.14 million, respectively (2). Combination of surgery and chemotherapy has been used as a standard therapy for the treatment of ovarian cancer patients, but overall 5-year survival of the patients with stage III and IV still remains at only 20 to 40%. Such poor prognosis of advanced stage ovarian cancer is accounted for by the intrinsic and acquired chemoresistance, since 30% of patients with advanced stages have been reported not to respond to the first-line chemotherapy, paclitaxel and cisplatin/carboplatin, and ~80% of the initial responders eventually relapse and develop chemoresistance (3). However, the underlying molecular mechanisms of chemoresistance in ovarian cancer are not fully understood.The signal transducers and activators of transcription (STAT) family proteins have been reported to be fairly upregulated and constitutively activated in many tum...

Inhibition of JAK2 Reverses Paclitaxel Resistance in Human Ovarian Cancer Cells

“…8,9 Constitutive STAT3 activation has been linked to resistance to standard-of-care chemotherapies, supporting that the development of paclitaxel resistance in ovarian cancers involves transcriptional control of drug resistance genes. 8 In keeping with this, inhibition of STAT3 using stattic, a small-molecule inhibitor, blocks STAT3 phosphorylation, decreases cell viability, and reduces clonogenicity of paclitaxel-resistant ovarian cancer SKOV3/TR cells.…”

“…8 In keeping with this, inhibition of STAT3 using stattic, a small-molecule inhibitor, blocks STAT3 phosphorylation, decreases cell viability, and reduces clonogenicity of paclitaxel-resistant ovarian cancer SKOV3/TR cells. 9 Recently, we found that Janusactivated kinase 2 (JAK2) gene was significantly upregulated in OC3/TAX300 cell line and in patient tissues. Because JAK2 can induce STAT3 activation, this suggests that the JAK2-STAT3 pathway might be related to paclitaxel resistance in ovarian cancers.…”

WITHDRAWN: Metformin antagonizes MPS-1-mediated IL-6/Stat3 signaling in ovarian cancer cells: possible mechanisms of stemness and angiogenesis inhibition

“…Signal transducer and activator of transcription 3 (Stat3) proteins, a member of the Stat family, has been shown to mediate a wide spectrum of cellular responses, including apoptosis, proliferation, pluripotency, invasion and angiogenesis (VEGF) [6], and be closely linked with tumorigenesis www.impactjournals.com/oncotarget/ Oncotarget, Advance Publications 2018 [7]. In addition, Stat3 is activated by the upregulation of upstream signaling molecules such as IL-6 [8] which can also stimulate expression of the vascular endothelial growth factor (VEGF) [3].…”

Investigational therapies targeting signal transducer and activator of transcription 3 for the treatment of cancer

“…Several drug-treated 'oncogeneaddicted' cancer cells induce a positive feedback loop leading to STAT3 activation, consequently promoting cell survival and limiting overall drug response. For example, overactivation of STAT3 is associated with resistance to chemotherapy (i.e., taxol [137]) and targeted agents used in a variety of tumors, including the anti-EGFR mAb cetuximab, the anti-HER2/neu receptor mAb trastuzumab and TKIs erlotinib, sunitinib, sorafenib, crizotinib and imatinib mesylate [138][139][140][141]. The combined use of these agents with STAT3 inhibitors should be investigated in clinical trials, even to understand if STAT3 inhibitors should be administered from the start of targeted therapy to reduce primary resistance or at time of acquired resistance.…”