No abstract

Oncolytic replication-selective adenoviruses constitute a rapidly growing therapeutic platform for cancer. However, the role of the host immune response and the E3 immunoregulatory genes of the human adenovirus were unknown until now. We identified four mouse carcinoma lines of variable permissivity for adenoviral gene expression, cytopathic effects and/or burst size. To determine E3 gene effects in immunocompetent tumor-bearing hosts, we injected tumors with one of three adenoviruses: Ad5 (E3 wild type), dl309 (del. E3 10.4/14.5, 14.7 kDa) or dl704 (del. E3 gp19 kDa). Compared with Ad5 and dl704, dl309 was cleared much more rapidly and/or its activity was lower in all four models. Intratumoral injection with dl309 resulted in markedly greater macrophage infiltration and expression of both tumor necrosis factor and interferon-gamma. Adenovirus replication, CD8(+) lymphocyte infiltration and efficacy were similar upon intratumoral injection with either dl704 or Ad5. E3-dependent differences were not evident in athymic mice. These findings have important implications for the design of oncolytic adenoviruses and may explain the rapid clearance of E3-10.4/14.5,14.7-deleted adenoviruses in patients.

Purpose: Pancreatic adenocarcinoma is a rapidly progressive malignancy that is highly resistant to current chemotherapeutic modalities and almost uniformly fatal.We show that a novel targeting strategy combining oncolytic adenoviral mutants with the standard cytotoxic treatment, gemcitabine, can markedly improve the anticancer potency. Experimental Design: Adenoviral mutants with the E1B19K gene deleted with and without E3B gene expression (AdDE1B19K and dl337 mutants, respectively) were assessed for synergistic interactions in combination with gemcitabine. Cell viability, mechanism of cell death, and antitumor efficacy in vivo were determined in the pancreatic carcinoma cells PT45 and Suit2, normal human bronchial epithelial cells, and in PT45 xenografts. Results: The DE1B19K-deleted mutants synergized with gemcitabine to selectively kill cultured pancreatic cancer cells and xenografts in vivo with no effect in normal cells. The corresponding wild-type virus (Ad5) stimulated drug-induced cell killing to a lesser degree. Gemcitabine blocked replication of all viruses despite the enhanced cell killing activity due to gemcitabine-induced delay in G 1 /S-cell cycle progression, with repression of cyclin E and cdc25A, which was not abrogated by viral E1A-expression. Synergistic cell death occurred through enhancement of gemcitabine-induced apoptosis in the presence of both AdDE1B19K and dl337 mutants, shown by increased cell membrane fragmentation, caspase-3 activation, and mitochondrial dysfunction. Conclusions: Our data suggest that oncolytic mutants lacking the antiapoptotic E1B19K gene can improve efficacy of DNA-damaging drugs such as gemcitabine through convergence on cellular apoptosis pathways.These findings imply that less toxic doses than currently practiced in the clinic could efficiently target pancreatic adenocarcinomas when combined with adenoviral mutants.