New insights into the therapeutic efficacy of the pancreatic cancer-targeted AV25CDC oncolytic adenovirus

WEBER, H.; GIDEKEL, M.; WERBAJH, S.; SALVATIERRA E; ROTONDARO, C.; SGANGA, L.; CURIEL, D.; CAFFERATA, E.; PODHAJCER OL

Washington

Congreso; 17th Annual Meeting of the American Society of Gene & Cell Therapy; 2014

American Society of Gene & Cell Therapy

Pancreatic Cancer is the fourth leading cause of cancer death in men and women and is characterized by dismal prognosis with no available therapeutics. We constructed a novel oncolytic adenovirus, AV25CDC, whose replication was driven by a 0.5 Kb of the cdc25B promoter placed upstream of E1A. The 468 bp cdc25B fragment extended from -426 to +42 and includes two SP1 sites, a TATA box and an INR motif. Cdc25B is overexpressed in more than 70 % of human pancreatic primary and disseminated cancers while faint or no expression was observed in chronic pancreatitis and pancreatic normal cells. After previous assessment of different fiber modifications we decided to improve viral lytic efficacy by pseudotyping AV25CDC with a chimeric fiber of serotypes 5/3. We investigated the in vitro lytic effect and the in vivo therapeutic efficacy, in combination or not with gemcitabine, on human pancreatic tumor xenografts orthotopically growing in nude mice and in immunocompetent tumors in Syrian hamsters. We also assessed biochemical markers of hepatic toxicity and tumor biomarkers levels. AV25CDC exhibited a strong in vitro lytic effect on pancreatic, gastric and colon cancer cells, even at MOIs of 0.1, while it showed a highly attenuated effect on normal fibroblasts. Moreover, it showed a synergistic effect with gemcitabine, in highly resistant, SW1990 pancreatic cancer cells. These in vitro lytic effects correlated with cdc25B expression in the different cell types. Mice harboring 15-days old orthotopic human SW1990 and MiaPaca 2 pancreatic tumors, treated intratumorally with AV25CDC combined or not with gemcitabine, exhibited 70%-80% reduction in tumor size at day 65 compared to control mice. Systemic treatment with AV25CDC combined with gemcitabine of orthotopic SW1990, MiaPaCa2 and Syrian Hamster Hap-T1 pancreatic tumors also showed in average 80% inhibition in tumor growth. At the end of the study in Syrian hamsters we observed 2.5 X 105 viral particles per ng of DNA in Hap-T1 tumors, while lungs, kidneys and spleen showed no viral particles and the liver exhibited only 1% of the viral particles observed in the tumor mass. The chemo-virotherapy treatment induced a return to normal levels of biochemical parameters of hepatic toxicity such as levels of alanine transaminase, aspartate aminotransferase and pancreatic amylase; moreover, mice treated with chemo-virotherapy also exhibited more than 90% reduction in CA19.9 serum levels compared to control mice. Further studies demonstrated that viral treatment disrupted the tumor stroma facilitating gemcitabine activity. These data demonstrates that AV25CDC is an effective oncolytic agent and a potential candidate for pancreatic cancer chemo-virotherapy.