Abstract 5924: Priming tumor cells by immunogenic modulation to enhance IL-27 immune therapy efficacy

Abstract

Abstract Immunogenic modulation is an emerging strategy for treating bone-metastatic prostate tumors, which present an altered balance between bone resorption and bone formation, with enhanced tumor growth and severe pain and fractures. There remains a critical lack of therapies that can significantly reduce tumor burden while simultaneously restoring the bone. Emerging immune therapies include Interleukin-27 (IL-27), a multifunctional cytokine that drives antitumor activity through STAT1/T-bet/IFNγ pathway immune-activation and anti-angiogenic mechanisms. IL-27 also is a pro-osteogenic factor, as it inhibits osteoclast formation and increases the pool of mature functional osteoblasts. Our goal for this work was to examine whether IL-27 immunetherapy efficacy still could be improved by the addition of ‘priming' strategies such as chemotherapy-induced immunogenic modulation in order to more efficiently promote tumor cell elimination by the immune system. Immunogenic modulation (IMO) develops following tumor cell exposure to chemotherapy, with alterations in tumor cell phenotype that prime cells for elimination by the immune system. Our results suggest that chemotherapy can reduce tumor cell viability, however, aggressive prostate tumor cells still are relatively resistant even at high doses. We have identified a potential cytokine combination that can sensitize aggressive prostate cancer cells (PC3) to low or sublethal doses of recently FDA-approved chemotherapy agents. Gene expression analyses using quantitative real time PCR arrays suggest that single chemotherapuetic agents promote a fairly low modulation and magnitude of apoptotic transcripts. Immune therapy alone (IL27 plus OP1 or 27OP1) upregulated several apoptosis genes, however, the combination of 27OP1 synergized with either cabozantinib or cabazitaxel, especially in augmenting expression of proapoptotic genes BNIP2, and CARD8 and immune modulatory gene CD70. Preliminary pathway analyses with the gene expression data (Pathgen) generated hypotheses of possible mechanisms involving gene regulation by AP1 or SMAD related pathways. Functional assays using luciferase reporter assays showed that AP1 activity was significantly upregulated by 27OP1, Cabozantinib, Cabazitaxel+27OP1, and Cabozantinib+27OP1. SMAD1/5/8 activity was significantly upregulated by OP1, 27OP1, Cabozantinib, Cabazitaxel+27OP1, and Cabozantinib+27OP1. These results suggest that 27OP1 synergizes with cabozantinib or cabazitaxel at least through AP1 and SMAD-regulatory mechanisms. Future studies will examine the effectiveness of these combinations in vivo, and preclinical studies are planned to examine whether low-dose chemotherapy can augment 27OP1 immunotherapy efficacy. Ultimately, our goal is to identify the optimal therapeutic niche for immunotherapy in combination with current immunomodulatory chemotherapies. Citation Format: Marxa L. Figueiredo, Manoel Figueiredo Neto. Priming tumor cells by immunogenic modulation to enhance IL-27 immune therapy efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5924.