ANTITUMOR ACTIVITY OF LOCOREGIONAL COMBINED CPG-ODN THERAPY IN EXPERIMENTAL CARCINOMA MODELS

ABSTRACT Several studies in preclinical models have demonstrated the superior anti-tumor effect of CpG oligodeoxynucleotides (CpG-ODN) when administered repeatedly and locally rather than systemically (De Cesare M, et al. Clin Cancer Res 2008;14:5512-8; De Cesare M, et al. J Immunother 2010;33:8-15). Based on those evidences, we evaluated aereosolized pulmonary delivery of CpG-ODN and it’s efficacy in treating estabilished malignant lung lesions in two different murine tumors, the immunogenic N202.1A mammary carcinoma cells and the weakly immunogenic B16 melanoma cells. Upon reaching the bronchoalveolar space, aerosolized CpG-ODN activated a local immune response, as indicated by production of IL-12p40, IFN-γ and IL-1β and by recruitment and maturation of DC cells in bronchoalveolar lavage fluid of mice. Treatment with aerosolized CpG-ODN induced an expansion of CD4+ cells in lung and was more efficacious than systemic i.p. administration against experimental lung metastases of immunogenic N202.1A mammary carcinoma cells, whereas only i.p. delivery of CpG-ODN provided anti-tumor activity, which correlated with NK cell expansion in the lung, against lung metastases of the poorly immunogenic B16 melanoma. The inefficacy of aerosol therapy to induce NK expansion was related to the presence of immunosuppressive macrophages in B16 tumor-bearing lungs, as mice depleted of these cells by clodronate treatment responded to aerosol CpG-ODN through expansion of the NK cell population and significantly reduced numbers of lung metastases. Our results indicate that tumor immunogenicity and the tumor-induced immunosuppressive environment are both critical factors to the success of CpG therapy in the lung. These results indicated that aereosol delivery might be a valuable, practical approach to CpG-ODN therapy for lung tumors. Moreover, to mimic clinical treatment situations in advanced human ovarian disease, we tested the efficacy of CpG-ODN in combination with other therapeutic reagents in IGROV-1 ovarian carcinoma ascites-bearing athymic mice. Our results indicated that CpG-ODN and cetuximab combination therapy, enhancing the immune response in the tumor microenvironment and concomitantly targeting tumor cells, was highly efficacious even in experimental advanced malignancies. Although differences in the distribution of TLR9 in mice and humans and the enrichment of this receptor on innate immune cells of athymic mice must be considered, our evidenced indicated a promising strategy to treat ovarian cancer patients with bulky ascites. Despite an aggressive multimodal approach, more than 50% of patients with locally advanced SCCHN will relapse. The worse prognosis of those cancers must certainly be linked to the HNSCCs strong influence on the host immune system. We observed that the combination of cetuximab plus CpG-ODN led to a significant survival-time increase of IGROV-1 ovarian tumor ascites-bearing athymic mice, .as compared to single CpG-ODN or cetuximab treatments. Cetuximab is actually approved by FDA also to treat late-stage head and neck cancer. Based on those observations, we evaluated if the combined therapy with local and repeated CpG-ODN might improve the therapeutic efficacy of this monoclonal antibody. Our results indicated that the association of CpG-ODN was not able to significantly improve the antitumor effect of cetuximab administered as single agent.