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.

Lynch syndrome is the most common hereditary colorectal cancer syndrome, and adenoma is one of the important premalignant lesions to colorectal cancer in Lynch syndrome. The first objective of this study was to calculate the detection rate of Lynch syndrome in colorectal polyps by using mismatch repair immunohistochemistry as the initial screening strategy. The second objective of this study was to optimize screening strategies for adenoma associated with Lynch syndrome by integrating polyp and/or patient characteristics such as polyp size, location, dysplasia, age of onset and/or family history of cancer. From June 2014 to May 2016, immunohistochemistry was performed for mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2) using endoscopically resected specimens obtained from newly diagnosed colorectal adenomas. Gene analysis was performed in patients with missing expression of mismatched repair protein. Five hundred and ten patients underwent colorectal polyp resection, with a total of 718 polyps. Five hundred and eight resected adenomas underwent mismatch repair protein immunohistochemical testing. Loss of mismatch repair protein expression was observed in six adenomas, accounting for 1.18% of all adenomas. Five patients then underwent genetic tests to identify two pathogenic mutations from different individuals, while another patient was suspected to have a pathogenic mutation. Three patients were younger than 50 years old. Two patients had advanced histology (high-grade dysplasia and malignant components) and one patient had a family history of cancer. Immunohistochemical detection of colorectal polyp mismatch repair protein as Lynch syndrome screening efficiency is low. Effective screening strategies may be improved by optimizing patient/polyp selection, such as focusing on young adenoma patients with a family history of cancer, or patients who present with high-risk features (large size, villous, high-grade dysplasia and malignant components).