TRA-8 anti-DR5 monoclonal antibody and gemcitabine induce apoptosis and inhibit radiologically validated orthotopic pancreatic tumor growth.

PURPOSE: To evaluate agonistic TRA-8 monoclonal antibody to human death receptor 5 (DR5) and gemcitabine in vitro and in an orthotopic pancreatic cancer model. EXPERIMENTAL DESIGN: Pancreatic cancer cell lines were screened for DR5 expression, cytotoxicity, and apoptosis induced by TRA-8, gemcitabine, or gemcitabine and TRA-8. An orthotopic model of pancreatic cancer was established in severe combined immunodeficient mice. Mice were treated with TRA-8, gemcitabine, or a combination for one or two cycles of therapy. Tumor growth (ultrasound) and survival were analyzed. RESULTS: All five pancreatic cancer cell lines showed DR5 protein expression and varying sensitivity to TRA-8-mediated cytotoxicity. MIA PaCa-2 cells were very sensitive to TRA-8, moderately resistant to gemcitabine, with additive cytotoxicity to the combination. S2-VP10 cells were resistant to TRA-8 and sensitive to gemcitabine with synergistic sensitivity to the combination. Combination treatment in vitro produced enhanced caspase-3 and caspase-8 activation. A single cycle of therapy produced comparable efficacy for single-agent TRA-8 and the combination of TRA-8 and gemcitabine, with significant reduction in tumor size and prolonged survival compared with gemcitabine alone or control animals. With two cycles of therapy, TRA-8 and combination therapy produced enhanced inhibition of tumor growth compared with single-agent gemcitabine or untreated animals. However, the combination regimen showed enhanced survival as compared with single-agent TRA-8. CONCLUSIONS: Pancreatic cancer cell lines express varying levels of DR5 and differ in their sensitivity to TRA-8 and gemcitabine-induced cytotoxicity. TRA-8 with two cycles of gemcitabine therapy produced the best overall survival.

Combination treatment with TRA-8 anti death receptor 5 antibody and CPT-11 induces tumor regression in an orthotopic model of pancreatic cancer.

PURPOSE: Evaluate the response of human pancreatic cancer cell lines and orthotopic tumors to TRA-8, an agonistic antibody to death receptor 5, in combination with irinotecan (CPT-11). EXPERIMENTAL DESIGN: MIA PaCa-2 and S2VP10 cells were treated with TRA-8 and/or CPT 11. Cell viability was determined by ATP assay. JC-1 mitochondrial depolarization and Annexin V assays confirmed cell death by apoptosis. Immunoblotting was used to evaluate protein changes. MIA PaCa-2 cells were injected into the pancreas of severe combined immunodeficient mice. Mice underwent abdominal ultrasound to quantitate tumor size before and after treatment with twice weekly injections of 200 microg TRA-8 and/or 25 mg/kg CPT-11 for one or two treatment cycles, each lasting 2 weeks. RESULTS: MIA PaCa-2 cells were more sensitive to TRA-8 and showed additive cytotoxicity, whereas S2VP10 cells showed synergistic cytotoxicity when treated with TRA-8 and CPT-11. Cell death occurred via apoptosis with increased cleavage of caspase-3, caspase-8, and caspase-9 and proapoptotic proteins Bid and poly(ADP)ribose polymerase after combination treatment compared with either agent alone. XIAP and Bcl-XL inhibitors of apoptosis were down-regulated. After a single cycle of in vivo combination therapy, tumor sizes had diminished significantly (P<0.001) at 8 days posttreatment compared with no treatment, CPT-11, and TRA-8; and there was a 50-day increase in survival with combination treatment over untreated controls (P=0.0002), 30 days over TRA-8, and a 36-day increase over CPT-11 monotherapy (P=0.0003). With two cycles of TRA-8/CPT-11 treatment, mean survival time increased significantly (P<0.001) to 169 days versus untreated controls, TRA-8 or CPT-11 (76, 121, or 108 days, respectively). CONCLUSIONS: Combination TRA-8 and CPT-11 therapy produced enhanced cytotoxicity and survival in the MIA PaCa-2 orthotopic model of pancreatic cancer.

Treatment with gemcitabine and TRA-8 anti-death receptor-5 mAb reduces pancreatic adenocarcinoma cell viability in vitro and growth in vivo.

Gemcitabine is a first line agent for pancreatic cancer, but yields minimal survival benefit. This study evaluated in vitro and in vivo effects of a monoclonal antibody (TRA-8) to human death receptor 5, combined with gemcitabine, using two human pancreatic cancer cell lines, S2VP10 and MIA PaCa-2. A subcutaneous model of pancreatic cancer was employed to test in vivo efficacy. S2VP10 and MIA PaCa-2 cells were treated with varying doses of gemcitabine and TRA-8. Cell viability and apoptosis were determined with an adenosine triphosphate assay and annexin V staining, respectively. Mitochondrial membrane destabilization was evaluated with fluorescence-activated cell sorting analysis of JC-1 stained cells. Caspase activation was evaluated by Western blot analysis. MIA PaCa-2 subcutaneous xenografts in athymic nude mice were evaluated for response to treatment with 200 mug of TRA-8 (intraperitoneal on days 9, 13, 16, 20, 23, and 27 postimplant) and 120 mg/kg gemcitabine (I.P. on days 10, 17, and 24). Tumor growth was measured with calipers. MIA PaCa-2 and S2VP10 cells receiving combination treatment with TRA-8 and gemcitabine demonstrated enhanced cytotoxicity, annexin V staining, and mitochondrial destabilization compared to either agent alone. Combination treatment produced enhanced caspase-3 and -8 activation in both cell lines compared with either agent alone. In vivo studies demonstrated mean subcutaneous tumor surface area (produce of two largest diameters) doubling times of 38 days untreated, 32 days gemcitabine, 49 days TRA-8, and 64 days combination treatment. TRA-8 is an apoptosis-inducing agonistic monoclonal antibody that produced synergistic cytotoxicity in combination with gemcitabine in vitro through enhanced caspase activation. These findings, with substantial inhibition of tumor growth in a mouse pancreatic cancer xenograft model receiving combination therapy, are encouraging for anti-death receptor therapy in the treatment of pancreatic cancer.