High efficacy of CpG-ODN, cetuximab and cisplatin combination for very advanced ovarian xenograft tumors.

BACKGROUND: To mimic clinical treatment situations in advanced human ovarian disease, we tested the efficacy of CpG-oligodeoxynucleotides (CpG-ODN), synthetic DNA sequences recognized by Toll-like receptor 9 and able to induce innate/adaptive immune responses, in combination with other possible therapeutic reagents in ovarian carcinoma ascites-bearing athymic mice. METHODS: Mice injected i.p. with IGROV-1 ovarian cancer cells were treated at different stages of ascites progression for 4 weeks with CpG-ODN, alone or in combination with Bevacizumab, Polyinosinic:Polycytidylic acid (Poly(I):Poly(C)), Gefitinib, Cetuximab and Cisplatin. Median survival time (MST) was calculated for each group. IGROV-1 cells treated or not with Cetuximab were assayed for antibody-dependent cellular cytotoxicity by 51Cr-release assay, and for macrophage antibody-dependent cell-mediated phagocytosis by flow cytometry. RESULTS: In mice treated when ascitic fluid began to accumulate, CpG-ODN combined with Bevacizumab, Poly(I):Poly(C) or Gefitinib did not significantly increase MST as compared with that using CpG-ODN alone, whereas MST in mice treated with CpG-ODN plus Cetuximab was significantly increased (>103 days for combination vs 62 days for CpG alone; P = 0.0008), with 4/8 mice alive at the end of the experiment. In experiments in mice showing increased abdominal volume and body weight (27.9 ± 0.8 g after vs 23 ± 1.1 g before tumor cell injection), treatment with Cisplatin in addition to CpG-ODN/Cetuximab led to significantly increased MST (105.5 days; P = 0.001), with all mice still alive at 85 days, over that using CpG-ODN/Cetuximab (66 days), Cetuximab/Cisplatin (18.5 days), Cisplatin (23 days) or saline (16 days). At a very advanced stage of disease (body weight: 31.4 ± 0.9 g), when more than half of control mice had to be sacrificed 6 days after starting treatments, the triple-combination therapy still increased MST (45 days; P = 0.0089) vs controls. CONCLUSIONS: CpG-ODN combination therapies that enhance the immune response in the tumor microenvironment and concomitantly target tumor cells are 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 results indicate a promising strategy to treat ovarian cancer patients with bulky ascites.

Anti-tumor activity of CpG-ODN aerosol in mouse lung metastases.

Studies in preclinical models have demonstrated the superior anti-tumor effect of CpG oligodeoxynucleotides (CpG-ODN) when administered at the tumor site rather than systemically. We evaluated the effect of aerosolized CpG-ODN on lung metastases in mice injected with immunogenic N202.1A mammary carcinoma cells or 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-1ß 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 critical factors to the success of CpG therapy in the lung, and point to the value of routine sampling of the lung immune environment in defining an optimal immunotherapeutic strategy.