Pancreatic carcinoma is a gastrointestinal malignancy with poor prognosis.Treatment with gemcitabine, the most potent chemotherapeutic against this cancer up to date, is not curative, and resistance may appear. Complementary treatment with an oncolytic virus, such as the rat parvovirus H-1PV, which is infectious but nonpathogenic in humans, emerges as an innovative option. Purpose: To prove that combining gemcitabine and H-1PV in a model of pancreatic carcinoma may reduce the dosage of the toxic drug and/or improve the overall anticancer effect. Experimental Design: Pancreatic tumors were implanted orthotopically in Lewis rats or subcutaneously in nude mice and treated with gemcitabine, H-1PV, or both according to different regimens. Tumor size was monitored by micro-computed tomography, whereas bone marrow, liver, and kidney functions were monitored by measuring clinically relevant markers. Human pancreatic cell lines and gemcitabine-resistant derivatives were tested in vitro for sensitivity to H-1PV infection with or without gemcitabine. Results: In vitro studies proved that combining gemcitabine with H-1PV resulted in synergistic cytotoxic effects and achieved an up to 15-fold reduction in the 50% effective concentration of the drug, with drug-resistant cells remaining sensitive to virus killing.Toxicologic screening showed that H-1PV had an excellent safety profile when applied alone or in combination with gemcitabine. The benefits of applying H-1PVas a second-line treatment after gemcitabine included reduction of tumor growth, prolonged survival of the animals, and absence of metastases on CT-scans. Conclusion: In addition to their potential use as monotherapy for pancreatic cancer, parvoviruses can be best combined with gemcitabine in a two-step protocol.

Pancreatic adenocarcinoma remains a fatal disease characterized by rapid tumor progression, high metastatic potential and profound chemoresistance. Gemcitabine is the current standard chemotherapy for advanced pancreatic cancer, but it is still far from optimal and novel therapeutic strategies are needed urgently. Mutations in the k-ras gene have been found in more than 90% of pancreatic cancers and are believed to play a key role in this malignancy. Thus, the goal of this study was to investigate the impact of k-ras oncogene silencing on pancreatic tumor growth. Additionally, we examined whether combining k-ras small interfering RNA (siRNA) with gemcitabine has therapeutic potential for pancreatic cancer. The treatment of tumor cell cultures with the corresponding k-ras siRNA resulted in a significant inhibition of k-ras endogenous expression and cell proliferation. In vivo, tumor xenografts were significantly reduced with k-ras siRNA GAT delivered by electroporation. Moreover, combined treatment with pSsik-ras GAT plus gemcitabine resulted in strong growth inhibition of orthotopic pancreatic tumors. Survival rate was significantly prolonged and the mean tumor volume was dramatically reduced in mice receiving the combined treatment compared with single agents. Collectively, these findings show that targeting mutant k-ras through specific siRNA might be effective for k-ras oncogene silencing and tumor growth inhibition. The improvement of gemcitabine-based chemotherapy suggests that this strategy might be used therapeutically against human pancreatic cancer to potentiate the effects of conventional therapy.

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