| Programmed death ligand 1 (PD‐L1) plays a significant role in colorectal tumorigenesis through induction of regulatory T cells (Tregs) and suppression of antitumor immunity. Furthermore, microRNAs (miRNAs) as the posttranscriptional
regulators of gene expression show considerable promise as a therapeutic target
for colorectal cancer (CRC) treatment. Considering this, in vitro effects of miRNA‐
124 (miR‐124‐3p) on CRC cell tumorigenesis and Tregs differentiation via targeting PD‐L1 were investigated in the current study. Functional analysis showed
that miR‐124 is significantly downregulated in CRC tissues as compared with
marginal normal samples (p < .0001), and its downregulation was negatively correlated with PD‐L1 expression. Moreover, a specific region in PD‐L1
3′‐untranslated region was predicted as the miR‐124 target and validated using
the luciferase assay. Further investigation showed that transfection of HT29 and
SW480 cells with miR‐124 mimics significantly reduced PD‐L1 mRNA, protein, and
cell surface expression, and inhibited Tregs in coculture models via modulating
interleukin [IL]‐10, IL‐2, tumor necrosis factor α, transforming growth factor beta, and
interferon gamma expression levels. Besides, miR‐124 overexpression decreased
CRC cell proliferation and arrested cell cycle at the G1 phase through downregulation of c‐Myc and induced apoptosis in CRC cells via upregulation of both
intrinsic and extrinsic pathways. Also, miR‐124 exogenous overexpression could
reduce colony and spheroid formation ability of CRC cells via downregulating
CD44 mRNA expression. miR‐124 also diminished MMP‐9 expression and subsequently suppressed cell migration and invasion. We also illustrated that STAT3
signaling was repressed by miR‐124 in CRC cells. Taken together, our findings
imply that considering the involvement of miR‐124 in the regulation of PD‐L1
through colorectal tumorigenesis and its remarkable antitumor effects, this miRNA could be regarded as the promising target for the development of therapeutic
approaches for colorectal cancer. |