MicroRNA-93-5p expression in tumor tissue and its tumor suppressor function via targeting programmed death ligand-1 in colorectal cancer

This work aimed to investigate miR-93-5p expression in tumor tissue and its in vitro effects in colorectal cancer (CRC) by targeting programmed death ligand-1 (PD-L1). MiR-93-5p and PD-L1 expression was detected in CRC and adjacent normal tissues by quantitative real-time polymerase chain reaction and immunohistochemistry. The correlation between miR-93-5p and PD-L1 was validated by a dual-luciferase reporter assay. HCT116 and SW480 cells were divided into blank, miR-NC, miR-93-5p mimics, miR-93-5p inhibitor, PD-L1 small interfering RNA (siRNA) and miR-93-5p inhibitor + PD-L1 siRNA groups, and wound-healing and transwell assays were performed to detect cell migration and invasion, respectively. Protein expression was measured by western blotting. The secretion of cytokines was detected in the CRC cell/T coculture models. MiR-93-5p was downregulated in CRC tissues with upregulated PD-L1. In PD-L1-negative patients, miR-93-5p expression was increased compared with that in PD-L1-positive patients. MiR-93-5p and PD-L1 expression levels were associated with the tumor differentiation, lymphatic metastasis, TNM, Duke's stage, and prognosis of CRC. PD-L1 siRNA weakened the migration and invasion abilities via decreased expression of matrix metalloproteinase-1 (MMP-1), -2, and -9, and these effects were abolished by the miR-93-5p inhibitor. Additionally, anti-PD-L1 upregulated the expressions of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), and interferon gamma (IFN-gamma) in the coculture of T cells with CRC cells, but downregulated the expressions of IL-1 beta, IL-10, and TGF-beta. However, these changes were partially reversed by miR-93-5p inhibition. miR-93-5p is expected to be a novel target for CRC treatment since it decreases the migration and invasion, as well as the immune evasion, of CRC cells via targeting PD-L1.