Identification of FBXW7α-regulated genes in M1-polarized macrophages in colorectal cancer by RNA sequencing

OBJECTIVES: To determine the FBXW7α-regulated genes in tumor-polarized macrophages in colorectal cancer. METHODS: This experimental study was performed between June 2017 and March 2019. FBXW7α siRNA transfected RAW264.7 cells, together with the control group, were co-cultured with the colon cancer cell line, Colon-26. M1 marker production from the macrophages was determined by ELISA and quantitative reverse transcription-polymerase chain reaction. Whole genomic differential expression between the FBXW7α siRNA group and the control group were determined by RNA-sequencing analysis. The target site of the microRNA-205 gene was predicted using Targetscan and was verified by the luciferase assay. By transfecting mimics or inhibitors of microRNA-205, we explored the role of FBXW7α/microRNA-205 axis in regulating the polarization of tumor-associated macrophages (TAM). RESULTS: FBXW7α knockdown in RAW264.7 enhanced the expression of cyclooxigenase (COX)-2 and inducible nitric oxide synthase (iNOS), mRNA expression and IL6, IL12, p40, and tumor necrosis factor-α (TNFα) production upon co-culture with Colon-26 cells in vitro. Further, compared with the control group, 648 genes in total were enhanced and 416 targets were downregulated in FBXW7α siRNA transfected cells, among which miR-205 was the most significantly upregulated. SMAD1 was identified as an miR-205 target. The FBXW7α/miR-205 axis might regulate TAM polarization by affecting SMAD1 expression. CONCLUSION: These results prove that the FBXW7α/miR-205 axis plays an important role in TAM polarization and could facilitate further exploration of its molecular mechanism.