<p>The uncontrolled recurrence and metastasis of malignant tumors is an important reason for the high mortality of malignant tumors. Ras Suppressor Protein 1 (RSU1) has been proven to play an important role in the pathogenesis and progression of multiple malignant tumors, while its role in colorectal cancer (CRC) is rarely reported. The aim of this study is to investigate the expression and prognostic of RSU1 in CRC, and its effect on the proliferation and migration of the human colon adenocarcinoma cell lines, Caco-2 cells to reveal the potential mechanism of proliferation and migration of CRC. Firstly, Kaplan-Meier plotter, Tumor immune estimate resource version 2 (TIMER2.0) databases and so on were used to assess prognostic implications and correlation of immune infiltration of RSU1 expression in CRC. For further exploration, in vitro experiments were performed to knock down RSU1 expression in Caco-2 cells with RSU1-siRNA. CCK8 assay, colony formation assay and wound healing assay were executed to detect the proliferation and migration of Caco-2 cells after RSU1 knockdown. Finally, functional enrichment analyses of RSU1 in CRC were performed to explore the specific molecular mechanisms, and the expression of related molecules was further verified by western blot analysis. According to the bioinformatic databases, RSU1 expression was increased in CRC tissues compared with normal colorectal tissues. High RSU1 expression was not conducive to Overall (OS), Relapse-free survival (RFS) and Post-progression survival (PPS) prognosis. Moreover, high expression of RSU1 decreased the immune infiltration level of CD⁸⁺ T-cell in CRC, also account for that high RSU1 expression was may be related to the bad survival prognosis of CRC. Functionally, RSU1 knockdown inhibited proliferation and migration of Caco-2 cells. KEGG pathway enrichment analysis revealed a significant connection between RSU1 and the Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway in CRC, western blot analysis also showed that RSU1 knockdown decreased PI3K and AKT protein expression. Silencing the RSU1 gene can significantly reduce the proliferation ability of Caco-2 cells and inhibit their migration behavior by suppressing the PI3K/AKT signaling pathway. Bioinformatics analysis indicated that RSU1 was highly expressed in CRC. Its high expression was not conducive to the prognosis of patients and would also reduce the immune infiltration level of CD⁸⁺ T cells. These findings provide a preliminary theoretical basis for the research on RSU1 as a potential target for prognosis assessment and immunotherapy of CRC.</p>