LCL161 increases paclitaxel-induced apoptosis by degrading cIAP1 and cIAP2 in NSCLC

Abstract

BackgroundLCL161, a novel Smac mimetic, is known to have anti-tumor activity and improve chemosensitivity in various cancers. However, the function and mechanisms of the combination of LCL161 and paclitaxel in non-small cell lung cancer (NSCLC) remain unknown.MethodsCellular inhibitor of apoptotic protein 1 and 2 (cIAP1&2) expression in NSCLC tissues and adjacent non-tumor tissues were assessed by immunohistochemistry. The correlations between cIAP1&2 expression and clinicopathological characteristics, prognosis were analyzed. Cell viability and apoptosis were measured by MTT assays and Flow cytometry. Western blot and co-immunoprecipitation assay were performed to measure the protein expression and interaction in NF-kB pathway. siRNA-mediated gene silencing and caspases activity assays were applied to demonstrate the role and mechanisms of cIAP1&2 and RIP1 in lung cancer cell apoptosis. Mouse xenograft NSCLC models were used in vivo to determine the therapeutic efficacy of LCL161 alone or in combination with paclitaxel.ResultsThe expression of cIAP1 and cIAP2 in Non-small cell lung cancer (NSCLC) tumors was significantly higher than that in adjacent normal tissues. cIAP1 was highly expressed in patients with late TNM stage NSCLC and a poor prognosis. Positivity for both cIAP1 and cIAP2 was an independent prognostic factor that indicated a poorer prognosis in NSCLC patients. LCL161, an IAP inhibitor, cooperated with paclitaxel to reduce cell viability and induce apoptosis in NSCLC cells. Molecular studies revealed that paclitaxel increased TNFα expression, thereby leading to the recruitment of various factors and the formation of the TRADD-TRAF2-RIP1-cIAP complex. LCL161 degraded cIAP1&2 and released RIP1 from the complex. Subsequently, RIP1 was stabilized and bound to caspase-8 and FADD, thereby forming the caspase-8/RIP1/FADD complex, which activated caspase-8, caspase-3 and ultimately lead to apoptosis. In nude mouse xenograft experiments, the combination of LCL161 and paclitaxel degraded cIAP1,2, activated caspase-3 and inhibited tumor growth with few toxic effects.ConclusionThus, LCL161 could be a useful agent for the treatment of NSCLC in combination with paclitaxel.

Role of the YAP-1 Transcriptional Target cIAP2 in the Differential Susceptibility to Chemotherapy of Non-Small-Cell Lung Cancer (NSCLC) Patients with Tumor RASSF1A Gene Methylation from the Phase 3 IFCT-0002 Trial

“…Given that several commonly used antineoplastic drugs are able to increase IAPs' expression [29,30], this study then evaluated the impact of paclitaxel and gemcitabine treatments on the IAP-2 levels present in or absent from RASSF1A gene expression. It was observed that gemcitabine treatment alone caused a significant increase in IAP-2 expression in HBEC-3 control cells.…”

Future Therapeutic Directions for Smac-Mimetics

“…Therefore, combining the SM LCL161 with paclitaxel in NSCLC tumors was investigated. Addition of LCL161 to paclitaxel therapy increased TNF expression, degradation of cIAP1/2 and activation of caspase-8 dependent apoptotic signaling, sensitizing NSCLC cancer cells to treatment in vitro [124]. Similar findings were observed in mice xenografted with NSCLC tumors where LCL161 plus paclitaxel treatment had better anti-tumor activity than either treatment alone [124].…”

“…However, due to its limited efficacy in some patients, new combination treatments are being investigated [123]. An increase in expression of cIAP levels has been shown to correlate with poor prognosis and lower overall survival in various types of cancer, including NSCLC [124][125][126][127]. Therefore, combining the SM LCL161 with paclitaxel in NSCLC tumors was investigated.…”

Membrane-bound TNF mediates microtubule-targeting chemotherapeutics-induced cancer cytolysis via juxtacrine inter-cancer-cell death signaling

“…The reported preclinical studies and clinical trials reported the observation that high anticancer efficacy of PTX/LCL161 co-therapies (including breast and lung cancers) [47][48][49]. Our discovery of the essential role of memTNF-mediated cell death in these effects defines the mechanistic rationale that can explain how this observed synergism actually occurs.…”

“…Given that IAP proteins block apoptosis caused by TNF, and considering that IAP antagonists have profound effects in potentiating solTNF-induced apoptosis [44][45][46], we hypothesized a combination treatment with IAP antagonists Smac mimetics (S) would further sensitize cancer cells to MTA-induced apoptosis. Currently, several Smac mimetics are being evaluated in clinical trials (https://clinicaltrials.gov) and combination of LCL161 with PTX has shown synergistic effects on several cancers [47][48][49], but the mechanism remains largely unknown.…”