Abstract 2830: The impact of gut microbial toxins and PGE2 on IL-23 production and its role in obesity associated colorectal tumorigenesis

Abstract

Abstract Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States. Studies indicate that excessive intake of high-fat diet (HFD) promotes CRC by modulating gut microbiome-associated inflammatory mediators. Recent evidence suggests that interleukin-23 (IL-23) plays an important role in the impact of a HFD on obesity, the gut microbiome and colon carcinogenesis. Our study aimed to elucidate the role of IL-23 in obesity associated CRC and explore an anti-IL-23 approach for prevention and treatment. First we profiled human plasma (n=15/arm) for circulating IL-23 levels and found significantly higher levels (p<0.0001) in obese individuals (BMI>30). In addition, IL-23 expression was evaluated in colonic tumors from both humans and preclinical rodent models. Data from the Cancer Genome Atlas showed significant over expression (p<0.0001) of IL-23A in CRC tumors (n=262) compared to normal tissue (n=41). This overexpression correlated with reduced disease free survival. Levels of both IL-23 and its receptor (IL23R) were evaluated in matched human CRC tissues by western blot and IHC and confirmed overexpression in CRC. IL-23 was also upregulated in colonic tumors from both sporadic (AOM-induced rat CRC) and FAP (Apcmin/+ mouse) rodent models when compared to matched normal mucosa. These data reveal a clear association of IL-23 overexpression with both obesity and colonic tumorigenesis. To understand IL-23 production in the context of gut microbial toxins and prostaglandin (PG)E2 levels, we performed several mechanistic studies to mimic the tumor microenvironment. To elucidate PGE2-mediated regulation of IL-23 in colon tumorigenesis we studied both macrophages and dendritic cell lines in in vitro and ex vivo conditions. The immune cells treated with either PGE2 or bacterial toxins (LPA/LTA) showed a significant increase in IL-23 expression which associated with macrophage polarization and dendritic cell phenotypic changes. Interestingly, when CaCo2 cancer cells were co-cultured with PGE2/LTA-LPA-educated macrophages or dendritic cells, the cancer cells displayed enhanced IL-23 expression along with increased tumor cell proliferation and self-renewal. Upon addition of human recombinant IL-23 directly to cancer cells (CaCo2 and HCT116), the cells exhibited increased IL-23R expression along with enhanced self-renewal, cell migration and invasive properties as well as loss of epithelial barrier permeability. In ex-vivo experiments we found that treatment of rat colon tumors with PGE2 increased the expression of IL-23 compared to normal mucosa. Overall our study results demonstrate that IL-23 is associated with both obesity and poor survival of CRC patients and that PGE2 and gut microbe toxins play an important role in IL-23-associated colonic tumor progression. This newly identified nexus represents a potentially important target for prevention of obesity associated colorectal cancer. Citation Format: Janani Panneerselvam, Venkateshwar Madka, Rajani Rai, Parthasarathy Chandrakesan, Courtney W. Houchen, Dharambir K. Sanghera, Katherine T. Morris, Chinthalapally V. Rao. The impact of gut microbial toxins and PGE2 on IL-23 production and its role in obesity associated colorectal tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2830.