Oncolytic Adenovirus Expressing IFN‐α synergistically potentiates chemotherapy, radiation, and chemoradiation in pancreatic cancer cells

Aside from curative resection, there is no effective treatment against pancreatic adenocarcinoma (PDAC). Late diagnosis and high recurrence results in five‐year survival of 7%. Notably, Phase II trials based on adjuvant therapy combining systemic IFN‐ α (IFN) with radiation, 5‐FU, and Cisplatin reported increase in five‐year survival of 21%. Smaller Phase II trials adding Gemcitabine to the treatment protocol also showed 30% increase in the two‐year survival of patients. Despite promising results, IFN trial drawbacks included high IFN systemic toxicity, and low IFN levels intratumorally. Drawbacks resulted in increased patient dropout, and as IFN is chemo‐radio sensitizer, low IFN in tumors could have hampered therapy full potential. Aiming to improve efficacy and tolerability of the promising IFN therapy, we developed an oncolytic adenovirus expressing human IFN (5/3DE3ADP‐IFN or OAd‐IFN). Vector has Ad5/3 fiber modification and overexpresses Adenoviral Death Protein, respectively contributing to increased infectivity and oncolysis in PDAC. Because Cox‐2 is up‐regulated in PDAC, Cox‐2 promoter was included upstream of Adenovirus (Ad) E1 region, restricting OAd‐IFN replication to PDAC. To achieve replication dependent expression of IFN, IFN gene was added to Ad E3 region under the control of major late promoter. To test vector in an immunocompetent syngeneic hamster model of pancreatic cancer, counterpart OAd vector expressing hamster IFN was generated (RGDDE3ADP‐ham‐IFN or OAd‐ham‐IFN). RGD fiber modification was included to enhance vector infectivity in hamster cells. In vitro assays demonstrated that OAd‐IFN increased cytotoxicity of chemotherapy (5‐FU, Cisplatin, and Gemcitabine), radiation (4 and 8Gy), and chemoradiation (5‐FU + radiation, Gemcitabine + Radiation, and 5‐FU+ Cisplatin + radiation) in PDAC cells. Comparison between OAd‐IFN and control vector not expressing IFN (OAd‐LUC) indicated IFN expressed by OAd‐IFN potentiated chemotherapy toxicity in PDAC cells. Combination index analysis showed that combinations of OAd‐IFN or OAd‐hamIFN with chemotherapy, radiation, or chemoradiation are synergistic. Also, combinations of OAd‐IFN and OAd‐hamIFN mimicking IFN clinical trial protocols were highly synergistic and cytotoxic. In vivo studies in hamster syngeneic model of pancreatic cancer showed that combinations of OAd‐hamIFN with chemotherapy, radiation, and chemoradiation augmented tumor shrinkage, delayed tumor recurrence, and increased survival compared to non OAd‐hamIFN treated groups. Quantification of viral replication showed OAd‐hamIFN effectively replicates and spreads in tumors. Our data confirms IFN expressing OAd improves killing effect of chemotherapy, radiation, and especially chemoradiation in PDAC cells and tumors. Impressive synergistic interaction between OAd‐IFN and chemotherapy, radiation, and chemoradiation suggests vector holds great potential to improve IFN therapy efficacy while decreasing its toxicity. As IFN therapy is of the few therapies reporting impressive improvement of pancreatic cancer survival, further development of OAd‐IFN combinations mimicking IFN therapy is highly encouraged. Support or Funding Information UofM Cancer Biology Training Grant (T32 CA009138), NIH/NCIP50CA101955 (UAB‐UMN SPORE in Pancreatic Cancer (Yamamoto and Davydova), NIH/NCIR01CA174861 (Davydova), and NIH/NCIR01CA094084 (Yamamoto).