| Summary: | Several studies have revealed that MFG-E8 (milk fat globule–epidermal growth factor 8) is related to tumour development and progression. However, the relationship between MFG-E8 expression and metastasis in colorectal cancer patients and the role of MFG-E8 in colorectal cancer invasion and progression remain unknown. In this study, we performed immunohistochemistry and quantitative real-time polymerase chain reaction to assess MFG-E8 expression in colorectal cancer and adjacent non-cancerous tissues. Colorectal cancer RNAseq data from The Cancer Genome Atlas project were downloaded and MFG-E8 expression was analysed. Gene set enrichment analysis was performed for gene ontology and pathway analysis associated with MFG-E8 expression. For in vitro studies, we used lentivirus-mediated MFG-E8 RNA interference and commercialized recombinant human MFG-E8 to investigate its role in colorectal cancer cell growth, migration and invasion. It seems that MFG-E8 was overexpressed in advanced colorectal cancer tissues compared with early-stage colorectal cancer tissues and adjacent non-cancerous tissues. Correlation analysis revealed that MFG-E8 expression was significantly related to plasma membrane invasion, lymph node metastasis, distant metastasis and tumour–node–metastasis stage. Survival analysis revealed that high MFG-E8 expression predicted a poorer prognosis than low MFG-E8 expression group both in our colorectal cancer cohort and The Cancer Genome Atlas colorectal cancer cohort. In vitro study suggested that MFG-E8 knockdown can suppress the growth of colorectal cancer cells without affecting the expression of the proliferation-related gene Ki67. MFG-E8 knockdown also suppressed colorectal cancer cell migration and invasion, a change accompanied by MMP-2 and MMP-9 downregulation. Moreover, MFG-E8 knockdown induced a shift from mesenchymal makers to epithelial makers, while pretreatment with rhMFG-E8 had the opposite effect. The effect of MFG-E8 on colorectal cancer cell migration, invasion and epithelial-to-mesenchymal was partially dependent on the PI3K/AKT signalling pathway. These findings provide a better understanding of the molecular mechanism underlying colorectal cancer progression and suggest a predictive role for MFG-E8 in colorectal cancer metastasis and prognosis.
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