gms | German Medical Science

Purpose: Advanced pancreatic cancer is at time of diagnosis frequently in a non-resectable stage. Beside surgery, there are still no promising therapies and new treatment options are urgently required. Poly (ADP-ribose)polymerase(s) (PARP) has been shown to be necessary for maintaining genome stability, via interaction and complex formation with proteins of the DNA repair machinery. The compelling evidance for the role of PARP in the cellular reaction to genotoxic stress was the stimulus to develop inhibitors as therapeutic agents to potentiate DNA damaging anticancer treatments. PARP-inhibitors like 3-aminobenzamid (3-ABA) enhance the in vitro cytotoxicity of DNA monofunctional alkylating agents such as radiation or chemotherapeutic agents. Here, we tested an approach combining the PARP inhibitor 3-ABA in combination with standard gemcitabine therapy in human pancreatic cancer cells.

Material and Methods: The combination therapy was evaluated in human pancreatic cancer cell lines Capan-1, AsPC-1 and Mia PaCa-2. Cell viability was determined by proliferation assay (XTT). Cell-cycle analysis (FACS), ELISA (M30 Apoptosense), Western Blot for caspase 8 and PARP, as soon as electron microscopy were used to identify apoptosis. Tumor growth and survival was assessed in nude mice by subcutaneously injected Capan-1 cells. In addition, Ki67 staining was performed on tumors for cell proliferation and in vivo apoptosis induction was measured by TUNEL assay and ELISA. To determine possible liver and bone marrow toxicity after therapy, we evaluated the liver enzymes AST and ALT as well as hemoglobine, white blood cells and platelets before treatment and 3 days after the last treatment.

Results: Combination therapy of gemcitabine and 3-ABA suppressed tumor cell growth dramatically more than gemcitabine alone in XTT, FACS and ELISA analysis. Our in vivo study demonstrates a significant reduced tumor weight and increased survival up to 42 days after cell inoculation compared to animals treated with PBS, gemcitabine or 3-ABA. Furthermore, TUNEL assay revealed a significant apoptosis induction and reduced proliferation in the combination group. Analysed blood samples of the animals were all within normal ranges at all times tested.

Conclusion: Combination treatment of gemcitabine and the PARP-inhibitor 3-aminobenzamide shows an additional antitumor effect in vitro and a significant tumor regression in vivo at low dosages and might become a promising therapeutic strategy for the treatment of pancreatic cancer.