Demethylation and Overexpression of CSF2 are Involved in Immune Response, Chemotherapy Resistance, and Poor Prognosis in Colorectal Cancer

PURPOSE: This study aimed to evaluate the role of colony-stimulating factor 2 (CSF2) in chemotherapy resistance, prognosis, and immune response and to identify its possible mechanisms underlying drug resistance. METHODS: Drug-resistant cell lines were obtained by successively increasing drug concentration. RNA-Seq was performed to screen hub genes. CSF2 expression was analyzed via immunohistochemistry. Moreover, The Cancer Genome Atlas (TCGA), Tumor Immune Estimation Resource (TIMER) dataset, and R2 platform were used to explore the correlations among CSF2 expression, prognosis, and immune response. RESULTS: RNA-Seq indicated that microRNAs in cancer, P53 signaling pathway, and cell cycle were associated with FOLFOX chemotherapy resistance. Protein-protein interaction (PPI), molecular complex detection (MOCDE), and qRT-PCR analysis verified CSF2 as the hub gene in chemotherapy resistance. Moreover, CSF2 expression was lower in the normal tissue than in the cancerous tissue (P<0.05). Higher expression of CSF2 was associated with poor OS and DFS in colon cancer patients (P<0.05). We further found similar results in the Oncomine database and R2 platform (P<0.05). A higher expression of CSF2 in the CRC tissue may be caused by demethylation, which was verified using the TCGA datasets. Moreover, GSEA demonstrated that CSF2 was associated with immune response, which was consistent with results reported using TIMER datasets. CONCLUSION: CSF2 is a novel biomarker and a prognostic factor for the survival of CRC patients affecting the immune response, and an overexpression of CSF2 in CRC patients may be caused by DNA demethylation.