Oxidative Stress Sensitizes Bladder Cancer Cells to TRAIL Mediated Apoptosis by Down-Regulating Anti-Apoptotic Proteins

Abstract

Purpose-TRAIL, an endogenous protein involved in immunosurveillance and a novel drug in clinical trials, is of particular interest as a cancer therapeutic because it can induce apoptosis in cancer cells but not in normal cells. Since some cancers develop resistance to TRAIL, safe and effective methods of TRAIL sensitization are of great clinical interest. This study explores how chemotherapy and oxidative stress affect TRAIL sensitivity and expression of proteins in the apoptotic pathway.Materials and Methods-Sensitivity to TRAIL was assessed in viability assays. Apoptosis was measured by caspase-3/7 activity and/or nuclear condensation using Hoechst staining. Western blotting was used to determine cleavage, phosphorylation, or alterations in protein expression.Results-TRAIL reduced the viability of 5637 but not J82 and T24 bladder carcinoma cells. Chemotherapy with doxorubicin or cisplatin decreased the expression of the anti-apoptotic protein cFLIP S and increased caspase-8 cleavage, reversing TRAIL resistance in T24 cells. Specific targeting of cFLIP S by siRNA was insufficient for sensitization to TRAIL in T24 cells. However, chemotherapy-mediated TRAIL sensitization was mimicked by low concentrations of hydrogen peroxide, which resulted in phosphorylation of translation elongation factor 2 (EF2) and reduced expression of several short half-life, anti-apoptotic proteins including FLIP S , XIAP, and survivin.Conclusions-Induction of oxidative stress by low concentrations of hydrogen peroxide may reverse TRAIL resistance and warrants the further exploration of hydrogen peroxide as an adjuvant intravesical treatment to lower the apoptotic threshold of bladder cancer cells.

Sensitization of human bladder tumor cells to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis with a small molecule IAP antagonist

“…3b). These data are consistent with other reports showing the importance of XIAP in the resistance of T24 bladder tumor cells to apoptotic death [44][45][46].…”

Oxidative stress specifically downregulates survivin to promote breast tumour formation

“…It has been shown that survivin levels remain downregulated when high OS induces apoptosis (White-Gilbertson et al , 2009; Ahamed et al , 2011). Our findings further provide strong evidences that OS specifically induce early downregulation of survivin in human breast cancer cell lines.…”

PMN and anti-tumor immunity—The case of bladder cancer immunotherapy

“…Postulated mechanism of action of BCG immunotherapy for non-muscle invasive bladder cancer. [71][72][73], chlorin-based photodynamic therapy [74], gemcitabine [74], chemotin [75], doxorubicin [76], cisplatin [76], gefitinib [77], histone deacetylase inhibitors [78,79], and bortezomib [80] are some of the agents that have increased the tumoricidal activity of TRAIL against bladder tumor cells. Because of the nature of the bladder microenvironment, there is the potential for any of these molecules to be instilled into the bladder to further potentiate the efficacy of TRAIL or other death-inducing molecules (such as TNF) that are induced after BCG administration.…”