Free fatty acid receptors type 2 and 4 mediate the anticancer effects of fatty acids in colorectal cancer - in vitro and in vivo studies

Abstract

High incidence of colorectal cancer (CRC) is influenced by diet low in fiber (source of short chain fatty acids, SCFAs, natural agonists for free fatty acid receptor type 2 (FFAR2)) and high in fat (main source of long chain fatty acids, LCFAs, FFAR4 agonists). FFAR2 and FFAR4 are downregulated in CRC. In this study, we characterized whether the anticancer effects of SCFAs and LCFAs are FFAR-dependent in in vitro and in vivo models of CRC. In vitro, SW-480 cell growth was determined after incubation with FFARs ligands (SCFAs: acetate, butyrate; LCFAs: palmitate, stearate) using MTT assay. Cell migration and invasion were investigated by wound healing and transwell-based invasion assays. In vivo, SCFAs and LCFAs were administered to azoxymethane/dextran sodium sulfate-treated mice. Real-time qPCR and Western blot were used to determine FFARs expression. SCFAs and LCFAs significantly decreased SW-480 cell growth, migration and invasion capacities. Combination of SCFAs and LCFAs induced synergistic inhibitory effects on CRC cell growth and motility. FFAR2 and FFAR4 expression were elevated in CRC cells treated with butyrate as well as with butyrate+acetate, and butyrate+palmitate+stearate. Concurrently, only FFAR4 expression was increased in CRC cells incubated with LCFAs. In vivo, treatment with LCFAs, but not SCFAs increased ffar2 and Ffar4 expression. Our findings showed that SCFAs and LCFAs inhibit cancer cell growth and their migration and invasion capabilities. Our study evidenced that the anticancer effects of SCFAs- and LCFAs are mediated by FFAR2 and FFAR4.