Combined treatment of a murine breast cancer model with type 5 adenovirus vectors expressing murine angiostatin and IL-12: A role for combined anti-angiogenesis and immunotherapy

In this study, we used intratumor delivery of adenoviral vectors to induce a selective anti-tumor response by combining the potent angiogenesis inhibi tor murine angiostatin (adenovirus (Ad)-angiostatin) with the powerful immu ne simulator and angiostatic cytokine murine IL-12 (Ad-IL-12). In a murine model of breast carcinoma, intratumor injection of Ad-angiostatin delayed m ean tumor growth, as compared with control virus with an initial regression of tumor growth, in 65% of treated animals. However, all treated animals e ventually succumbed to the tumors. Mice injected with Ad-IL-12 alone respon ded with an initial regression in 20% of treated animals, with only 13% dev eloping a total regression. Coinjection of the vectors resulted in 96% of t he treated animals developing an initial regression, with 54% undergoing a total regression of the tumor. These mice were resistant to tumor rechallen ge and developed a strong CTL response. Frozen tumor sections were stained for microvessel density using an Ab against murine CD31, an endothelial cel l marker. Automated image analysis revealed the mean microvessel density fo llowing the administration of Ad-angiostatin and Ad-IL-12 alone or in combi nation was significantly reduced compared with the control-treated tumor. I n summary, we have shown that a short-term course of antiangiogenic therapy combined with immunotherapy can effectively shrink a solid tumor and vacci nate the animal against rechallenge. The rationale for this therapy is to l imit the tumor size by attacking the vasculature with angiostatin, thereby allowing IL-12 to mount a T cell-specific response against the tumor Ag.