Abstract LB-315: Chemoprevention gene therapy (CGT) approach for pancreatic cancer.
Authors: Siddik Sarkar, Belal Azab, Bridget A. Quinn, Xuening Shen, Paul Dent, Alexander L. Klibanov, Luni Emdad, Swadesh K. Das, Devanand Sarkar, Paul B. Fisher
Journal: Cancer Research (2013)

Abstract Pancreatic cancer is an aggressive cancer without currently effective treatment options. To develop effective therapies for pancreatic and other cancers, we developed bipartite Adenoviruses (Ads) that conditionally replicate in cancer cells and simultaneously express the cancer-specific apoptosis-inducing cytokine melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), termed Cancer Terminator Virus (CTV-M7). To enhance transduction of CTV-M7 in cancer cells in a Coxsackie-Adenovirus receptor (CAR) independent manner, a chimeric tropism-modified CTV-M7 was generated in which the Ad.5 fiber knob was replaced by the Ad.3 fiber knob (Ad.5/3-CTV-M7). This Ad displays enhanced infectivity in cancer cells with low as well as high CAR. Although mda-7 displays broad-spectrum anticancer properties, pancreatic ductal adenocarcinoma (PDAC) cells are intrinsically resistant to mda-7-mediated killing due to an mda-7 mRNA translational block. However, when Ad.5-mda-7 is combined with reactive oxygen species (ROS) inducers, there is a conversion of mda-7 mRNA into protein resulting in pancreatic cancer cell death. Hence, we employed perillyl alcohol (POH), which induces ROS and when combined with mda-7 results in profound killing of PDAC cells, a chemoprevention gene therapy (CGT) approach. ROS induced by POH results in phosphorylation of p70S6-Kinase, 4EBP-1 and eIF4E leading to formation of the pre-initiation complex of protein translation machinery causing an association of polysomes with weakly translated mda-7 mRNA, subsequently enhancing MDA-7 translation. We presently evaluated Ad.5/3-CTV-M7 plus POH as a therapy for PDAC by MTT assays and western blotting. Cell viability was reduced in pancreatic cancer cell lines irrespective of K-ras status following treatment with POH and infection with CTV-M7. This combination synergistically induced mda-7-mediated cancer-specific apoptosis by inhibiting anti-apoptotic Bcl-xL and Bcl-2 protein expression and inducing an endoplasmic reticulum stress response through induction of BiP/GRP-78, which was most evident in chimeric-modified CTV-M7-infected PDAC cells. Moreover, it was found that Ad.5/3-CTV-M7 in combination with POH sensitized MIA PaCa-2 cells over-expressing either Bcl-2 or Bcl-xL to mda-7-mediated apoptosis, demonstrating that CGT can overcome therapy resistance frequently seen in PDAC with elevated expression of these anti-apoptotic proteins. Treatment of MIA PaCa-2 overexpressing Bcl-xL cells established in both flanks of nude mice with POH and systemic administration of Ad.5/3.CTV-M7 using a ultrasound-targeted microbubble-destruction technique in tumors in one flank, resulted in tumor elimination on both flanks. These exciting studies support the potential of the CGT approach using POH and Ad.5/3-CTV-M7, for the therapy of currently intractable, therapy-resistant pancreatic cancers. Citation Format: Siddik Sarkar, Belal Azab, Bridget A. Quinn, Xuening Shen, Paul Dent, Alexander L. Klibanov, Luni Emdad, Swadesh K. Das, Devanand Sarkar, Paul B. Fisher. Chemoprevention gene therapy (CGT) approach for pancreatic cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-315. doi:10.1158/1538-7445.AM2013-LB-315