Anti-tumor activity of the TRA-8 anti-DR5 antibody in combination with cisplatin in an ex vivo human cervical cancer model.

OBJECTIVES: To investigate the cytotoxicity of TRA-8, an antibody that specifically binds death receptor 5 (DR5), alone and in combination with cisplatin, using an ex vivo human cervical cancer model. METHODS: Fifteen cervical cancer specimens were obtained at the time of radical hysterectomy and tumor slices were prepared with the Krumdieck tissue slicer. Tumor slices were exposed to varying concentrations of TRA-8, cisplatin, or the combination of TRA-8 and cisplatin. Using non-linear modeling, dose response curves and IC50 values were generated for each specimen treated with TRA-8. The additive cytotoxic effect of combination treatment was evaluated as well. In addition to ATP viability assays, treated and untreated slices were assessed by immunohistochemistry (IHC) and western blot analysis to confirm apoptosis induction via the extrinsic pathway. RESULTS: Eleven patient specimens yielded TRA-8-induced IC50 values. Sixty-four percent were found to be sensitive to TRA-8-induced cytotoxicity at IC50 doses less than 1000 ng/ml. Seven patient specimens underwent combination treatment with TRA-8 and cisplatin. Of these specimens, 86% exhibited additive cytotoxicity in comparison to treatment with either agent alone. IHC revealed an increase in DR5 expression in tumor slices treated with cisplatin for 24 h. IHC and Western blotting demonstrated TRA-8-induced cell death via apoptosis and activation of caspase 3 and 8. CONCLUSIONS: This study confirms the utility of an ex vivo human cervical cancer model, to evaluate the anti-tumor activity of TRA-8 and cisplatin. This model may be a useful pre-clinical tool to assess cytotoxicity and mechanistic properties of novel agents in cervical cancer.