Abstract 4235: Obesity drives inflammation and metabolic reprogramming in an orthotopic mouse model of early colon cancer
Authors: Glenny Elaine M. , Mirminachi Babak , McFarlane Tori L. , Roper Jatin , Hursting Stephen D. 
Published: April 2023

Abstract
Obesity is strongly associated with colon cancer incidence and, in animal models, promotes colon cancer growth and progression. Mounting evidence indicates that circulating growth factors and chronic inflammation are procancer factors likely mediating this relationship. While obesity blunts antitumor immunity in many cancer types, how obesity-driven inflammation and reduced antitumor immunity may cooperate to promote colon cancer progression is not yet clear. Here we used a murine syngeneic orthotopic transplantation model of colon cancer to profile changes driven by diet-induced obesity (DIO) in the immune and cancer cell compartments of the tumor using digital spatial profiling and RNA sequencing. 7-9-week-old male and female C57BL/6 mice remained on either a 10 kcal% fat diet (control, n=34) or a 60 kcal% fat diet (DIO, n=27) for at least 19 weeks. 700 Apc-null;KrasG12D/+;Trp53-null;Smad4-null;tdTomato (i.e., AKPS) organoids were transplanted into the colonic wall of control and DIO mice via colonoscopy-guided injection. Tumors were excised after four weeks of growth, an early time point to assess changes between diet groups independent of tumor size differences or weight loss associated with tumor growth. RNA sequencing was performed on RNA extracted from tumoral CD45+ and EpCAM+ cell fractions isolated using Milltenyi MicroBeads. DIO mice weighed more than controls (males: controls 37.0 g ± 5.1 vs. DIO 47.4 g ± 4.3; females: controls 26.4 g ± 3.7 vs. DIO 45.9 g ± 9.7) and had more mesenteric fat surrounding the colon (males: controls 388 mg ± 217 vs. DIO 577 mg ± 185; females: controls 201 mg ± 143 vs 1176 mg ± 589). Leptin, resistin, and plasminogen activator inhibitor-1 were significantly elevated in the serum of DIO mice relative to control mice. Tumor weight did not differ between groups. Gene set enrichment analysis demonstrated that tumor cells from DIO mice were significantly enriched for pathways related to inflammation (INFLAMMATORY_RESPONSE, IL6_JAK_STAT3_SIGNALING), glucose and lipid metabolism (GLYCOLYSIS, FATTY_ACID_METABOLISM), and proliferation (E2F_TARGETS, G2M_CHECKPOINT). Within the CD45+ transcriptomic profiles, Tumor Immune Estimation Resource (TIMER2.0) indicated an increase in M0- and M1-like macrophages and B cells in tumors from DIO compared with control mice. Analysis of whole tumor sections from DIO mice showed significantly reduced CD3+ cells by immunofluorescence and more Ki67+ CD45+ immune cells by digital spatial profiling relative to tumors from control mice. Taken together, obesity drives an inflammatory profile in both the immune and epithelial cell populations of AKPS murine tumors, which is associated with increased markers of proliferation. Future studies will address whether inflammatory signals from the mesenteric fat adjacent to the colon tumors may contribute to obesity-driven tumor inflammation, and thereby to colon cancer progression.
Citation Format: Elaine M. Glenny, Babak Mirminachi, Tori L. McFarlane, Jatin Roper, Stephen D. Hursting. Obesity drives inflammation and metabolic reprogramming in an orthotopic mouse model of early colon cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4235.