Objective To investigated the strength of adenosine diphosphate ribosylation factor-like protein 14 (ARL14) expression in colorectal cancer (CRC) and its relationship with major infiltrating cells in the tumor microenvironment.

Methods Data from the 607 CRC cases and 51 normal tissues in the TCGA-CRC dataset were analyzed. ARL14 mRNA expression levels were retrospectively collected and the relationship between ARL14 expression and CRC patient prognosis was analyzed. Transcription factors and miRNAs involved upstream in regulating ARL14 expression were predicted. Bioinformatics methods were used to analyze the relationship between ARL14 expression and cell infiltration into the tumor microenvironment. Tumor and normal tissues from 45 CRC patients who underwent surgery in Tianjin Medical University Cancer Institute & Hospital from January 2020 to January 2021 were collected, and expression levels of ARL14, smooth muscle actin-α (α-SMA), and fibroblast-activated protein (FAP) were detected by immunohistochemical staining to verify the relationship between ARL14 expression and fibroblast activation.

Results Differential analysis showed that the ARL14 expression level was significantly lower in CRC tissues than in normal tissues (P<0.001). Patients with low ARL14 expression had worse prognosis than patients with high expression (Log-rank P=0.025). MCP-counter analysis showed that ARL14 expression correlated negatively with fibroblast infiltration (P<0.0001). Immunohistochemical staining results showed that ARL14 expression was significantly lower in tumors than in normal tissues (P<0.01). ARL14 expression also correlated negatively with α-SMA and FAP expression levels in the interstitium. Conclusions: ARL14 may play a tumor suppressor role in CRC and inhibit fibroblast activation.