Links Between Obesity And Secreted Frizzled-Related Protein 4 (Sfrp4) In A Murine Model Of Colon Cancer.

Abstract Obesity is a well-established risk factor for colon cancer and the effect of obesity-mediated inflammation is particularly pronounced in colon carcinogenesis. An incomplete understanding of the biology underlying this strong obesity-colon cancer association has hampered efforts to identify effective colon cancer prevention strategies. The current study aims to identify novel colon tumor intrinsic targets that mediate critical inflammatory signals underlying the obesity-colon cancer connection. To induce colon tumors, FVB/N male mice were treated weekly with azoxymethane (10 mg/kg intraperitoneally) for 5 weeks. Mice were then randomized to either continue receiving 10 kcal% fat diet (control) or were switched to a 60 kcal% fat diet to promote diet-induced obesity (DIO) over a 15-week period. DIO mice were then randomized to either receive 0ppm (DIO) or 140ppm sulindac (DIO+Su), a non-steroidal anti-inflammatory drug, for 7 additional weeks. At the end of the 27-week study, colonic tumors were collected for histology and global transcriptomic analysis using Affymetrix Clariom D mouse gene expression microarrays. DIO increased tumor multiplicity and burden in AOM-treated mice. Moreover, long-term administration of dietary sulindac was sufficient to reduce inflammatory signals, tumor multiplicity, and tumor burden in DIO-Su versus DIO mice. Principal component analysis and hierarchical clustering based on the 1,000 most differentially expressed genes revealed distinct gene expression profiles in tumors from control, DIO, and DIO+Su mice. To determine the biological processes most up- or down-regulated in tumors from DIO mice, gene set enrichment analysis was run using the hallmark gene sets. Epithelial-mesenchymal-transition (EMT) was the most upregulated gene set in tumors from DIO mice compared with tumors from control mice (normalized enrichment score 2.00; adjusted p=0.0002) and compared with tumors from DIO+Su mice (normalized enrichment score 1.78; adjusted p=0.009), suggesting that obesity drives EMT via an inflammatory mechanism. Based on a leading-edge analysis, secreted frizzled-related protein 4 (Sfrp4) expression was significantly enriched in the EMT gene set. Sfrp4 is of biological interest given its biphasic modulation of Wnt signaling and association with poor prognosis in aggressive prostate cancer. We confirmed via immunofluorescence that Sfrp4 is produced by AOM-treated colonic intestinal epithelial and submucosal cell populations and observed by qPCR that it is expressed across multiple human colon cancer cell lines. Hence, Sfrp4 may be a novel target to mitigate obesity-induced exacerbation of colon tumorigenesis. Future work will determine the role of Sfrp4 in colon cancer cell-adipose interactions and whether ablation of Sfrp4 is sufficient to impede colon tumor growth. This research was supported by R35CA197627 to S. Hursting. Citation Format: Elaine M. Glenny, Laura W. Bowers, Diana Li, Jatin Roper, Stephen D. Hursting. Links between obesity and secreted frizzled-related protein 4 (Sfrp4) in a murine model of colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2579.