528. Infectivity Enhancement of a Genetic Fiber Mosaic Adenovirus Vector in Ovarian Cancer Cells

Abstract

Despite aggressive surgical debulking and chemotherapy, the 5-year survival rate for advanced ovarian cancer is very low. Thus, gene therapy is a promising treatment alternative; however, clinical cancer gene therapy trials with recombinant human adenovirus (Ad) serotype 5 have seen limited success. The efficiency of Ad gene transfer to ovarian cancer cells has been limited by low expression of the primary Ad5 receptor, the coxsackie and adenovirus receptor (CAR). Thus, development of novel Ad vectors providing CAR-independent tropism may lead directly to therapeutic gain. We have previously shown that reovirus |[sigma]|1, a fiber-like attachment protein, incorporated into Ad5 virions, contributed to achieve infectivity enhancement in ovarian cancer cells via CAR-independent manner. Also we have reported that ovarian cancer cells possess a primary receptor for Ad3, which is independent from CAR. We hypothesized that an Ad5 vector containing both reovirus and Ad3 fibers would result in expanded tropism based on cellular expression of CAR independent receptors, thereby providing increased gene delivery to ovarian cancer cells. We have constructed a mosaic fiber Ad5 vector, designated Ad5/3-|[sigma]|1, encoding a luciferase reporter gene and two fibers. The first fiber is the chimeric fiber possessing the reovirus |[sigma]|1 and the second fiber is the chimeric fiber possessing the Ad3 fiber knob. Virus particles were purified and characterized by standard manners. Ad5/3-|[sigma]|1 gene delivery, as measured by luciferase transgene activity, was analyzed in a panel of ovarian cancer cell lines and primary ovarian cancer tissues. Characterization of Ad5/3-|[sigma]|1 confirmed the incorporation of both fibers in the same virus particle. Functionally, Ad5/3-|[sigma]|1 was able to utilize primary receptors for both reovirus and Ad3 for attachment to cells. Ad5/3-|[sigma]|1 provided 28 to 62-fold greater gene transfer versus the isogenic control Ad5 vector in a panel of ovarian cancer cell lines, known for relatively low CAR expression. Additionally, Ad5/3-|[sigma]|1 yielded 4.5-fold higher gene transfer to primary ovarian cancer tissue slices. We developed an infectivity enhanced Ad5 vector to address the key issue of limited Ad5 vector efficiency. The expanded tropism of the Ad5/3-|[sigma]|1 represents a crucial attribute for an Ad-based gene therapy vector for ovarian cancer, and may represent an agent with future clinical utility.