A Novel Synergistic Combination of Cyclophosphamide and Gene Transfer of Interleukin-12 Eradicates Colorectal Carcinoma in Mice

Abstract

Purpose: Interleukin-12 (IL-12) is an immunostimulatory cytokine with potent antitumor effects in several animal models. However, serious toxicity has been associated with its systemic application in humans. Gene transfer has emerged as a tool to specifically express therapeutic genes into the tumor/peritumoral milieu, thus avoiding systemic toxicity. The aim of this study was to analyze whether subtherapeutic doses of an adenovirus encoding IL-12 (AdIL-12) might synergize with low immunopotentiating doses of cyclophosphamide in the treatment of colorectal carcinoma. Experimental Design: The antitumor effect of combining a single low dose of cyclophosphamide with an intratumoral injection of AdIL-12 was evaluated in an in vivo murine colorectal carcinoma model. The immune responses achieved with different treatments were monitored, comparing the effect of combining both therapies with individual treatments. Results: The combined therapy induced a complete tumor regression in >50% of mice in a synergistic fashion, and it significantly prolonged their survival. This strategy was superior to each single treatment in reducing both peripheral and splenic CD4+CD25+Foxp3+ regulatory T cells, increasing the number of activated dendritic cells, and inducing IFN-γ-secreting CD4-positive T lymphocytes. Importantly, the combined treatment generated a powerful tumor-specific CTL response. Consistently, a significant reduction in IL-10 levels was found. Our data suggest that the combination of nontoxic doses of cyclophosphamide with AdIL-12 allows the generation of good antitumoral responses, thus avoiding undesired side effects of both agents. Conclusions: Our data strongly support the use of a combination of cyclophosphamide and AdIL-12 as a novel therapeutic strategy against colorectal carcinoma. (Clin Cancer Res 2009;15(23):7256–65)

Arsenic Trioxide Exerts Antitumor Activity through Regulatory T Cell Depletion Mediated by Oxidative Stress in a Murine Model of Colon Cancer

“…Multiple immunotherapy strategies for colorectal carcinoma are currently under preclinical and clinical evaluation (21). Immunotherapy usually has to face strong mechanisms of immune escape induced by tumors.…”

“…To increase the efficacy of immunotherapy strategies, it is potentially interesting to explore therapeutic interventions that exploit tolerogenic processes such as those induced by T regs in tumor-bearing hosts (22). In this context, it has been shown that low-dose CYP decreases the number of T regs (8,21) and can enhance the antitumor activity of adoptively transferred T cells, as well as tumor vaccines (23). However, CYP may exert a toxic effect on other lymphocyte populations that could attenuate its immunostimulatory effect.…”

New insights into IL-12-mediated tumor suppression

“…[77][78][79][80][81][82][83] Furthermore, the combination with chemotherapeutic or antiangiogenic agents in lung, skin and colorectal cancer, or with antiangiogenic agents in prostate cancer proved to be more efficient than viral-mediated IL-12 gene therapy alone in different types of tumors. [84][85][86][87][88][89] Even though local delivery of IL-12 by gene therapy resulted in a more sustained expression of IL-12 in comparison with the levels obtained by injecting the recombinant protein, the lack of selectivity and the occurrence of non-specific immune responses associated with the use of viral vectors remain a major concern when using this strategy to deliver IL-12.…”

Immunomodulatory effects of low dose chemotherapy and perspectives of its combination with immunotherapy

“…In this direction, Malvicini et al 72 observed in a murine model of colorectal carcinoma that the combination of CTX with an IL-12-encoding adenovirus vector induces complete regression in more than 50% of tumor-bearing mice. Such treatment was able to decrease the number of peripheral and spleen Treg, at the same time that it increased the numbers of activated DC and IFN-c-secreting CD4þ lymphocytes.…”