Oxaliplatin Sensitizes Human Colon Cancer Cells to TRAIL Through JNK-Dependent Phosphorylation of Bcl-xL

Abstract

BACKGROUND & AIMS:Oxaliplatin sensitizes drug-resistant colon cancer cell lines to tumor necrosis factorrelated apoptosis inducing ligand (TRAIL), a death receptor ligand that is selective for cancer cells. We investigated the molecular mechanisms by which oxaliplatin sensitizes cancer cells to TRAIL-induced apoptosis. METHODS: We incubated the colon cancer cell lines HT29 and V9P, which are resistant to TRAIL, with TRAIL or with oxaliplatin for 2 hours, followed by TRAIL. Annexin V staining was used to measure apoptosis; RNA silencing and immunoblot experiments were used to study the roles of apoptosis-related proteins. Site-directed mutagenesis experiments were used to determine requirements for phosphorylation of Bcl-xL; coimmunoprecipitation experiments were used to analyze the interactions among Bcl-xL, Bax, and Bak, and activation of Bax. RESULTS: Oxaliplatin-induced sensitivity to TRAIL required activation of the mitochondrial apoptotic pathway; reduced expression of Bax, Bak, and caspase-9, and stable overexpression of Bcl-xL, reduced TRAIL-induced death of cells incubated with oxaliplatin. Mitochondrial priming was induced in cells that were sensitized by oxaliplatin and required signaling via c-Jun N-terminal kinase and phosphorylation of Bcl-xL. Mimicking constitutive phosphorylation of Bcl-xL by site-directed mutagenesis at serine 62 restored sensitivity of cells to TRAIL. Co-immunoprecipitation experiments showed that oxaliplatin-induced phosphorylation of Bcl-xL disrupted its ability to sequestrate Bax, allowing Bax to interact with Bak to induce TRAIL-mediated apoptosis. CONCLUSIONS: Oxaliplatin facilitates TRAIL-induced apoptosis in colon cancer cells by activating c-Jun N-terminal kinase signaling and phosphorylation of Bcl-xL. Oxaliplatin-induced sensitivity to TRAIL might be developed as an approach to cancer therapy.

Secretory clusterin contributes to oxaliplatin resistance by activating Akt pathway in hepatocellular carcinoma

“…Its main mechanism is to trigger cell death by forming adducts with DNA and block DNA replication. (3) The present study has also demonstrated that OXA induced apoptosis of HCC cells by upregulating expression of Bax, downregulating Bcl-2 and Bcl-xL, and leading activation of caspase-9, in accordance with a report by El Fajoui et al (43) Downregulation of sCLU by siRNA or antisense oligonucleotides resensitizes resistant prostate cancer cells to docetaxel, (44,45) and overexpression of sCLU in prostate cancer cells renders them resistant to paclitaxel. (46,47) Custirsen (OGX-011), an antisense oligonucleotide drug, has been applied to treat prostate cancer and NSCLC in clinical trials.…”

STI571 reduces TRAIL-induced apoptosis in colon cancer cells: c-Abl activation by the death receptor leads to stress kinase-dependent cell death

“…Thus, sensitizing cancer cells to TRAIL through activating JNK and p38, which subsequently regulate pro-apoptotic and anti-apoptotic Bcl-2 family members and p53, becomes a promising approach to cancer therapy [41-44]. Using pharmacological inhibitors, we showed the involvement of JNK and p38 in TRAIL-induced cytotoxicity and in STI571-induced cell protection in HCT116 cells.…”

Molecular Targets of TRAIL-Sensitizing Agents in Colorectal Cancer

“…More recently, lapatinib, a dual inhibitor of EGFR and HER2, was reported to increase TRAIL-induced cell death in CRC cells by promoting JNK/c-Jun-driven DR over-expression [42]. Modulation of molecules involved in the intrinsic/mitochondrial pathway accounts for the sensitization of TRAIL resistant CRC cells to sunitinib, a tyrosine kinase inhibitor, and oxaliplatin, a third-generation platinum agent [43,44]. In particular, sunitinib decreases the expression of the anti-apoptotic proteins Mcl-1 and XIAP [43] while the oxaliplatin-mediated TRAIL sensitization increases phosphorylation of Bcl-xL, thus reducing the anti-apoptotic activity of this protein [44].…”