CCL5 promotes colon cancer progression via PI3K/AKT signaling and is negatively regulated by STAT1

Colon cancer (CC) and rectal cancer rank third in incidence, affecting millions of individuals globally. The immune-modulatory function of CCL5 in CC is the main focus of current research, and little is known about its tumor-intrinsic processes. There is a lack of systematic research on the regulatory link between STAT1 and CCL5 in CC. This study aimed to investigate the dual functions of CCL5 and its STAT1-mediated regulation in CC progression, and to elucidate the underlying molecular mechanisms.

This study combines retrospective clinical observation with experimental research. Postoperative paraffin-embedded tissues were collected from 40 colorectal cancer (CRC) patients through convenience sampling. Immunohistochemistry was employed to detect CCL5 protein expression, followed by semi-quantitative scoring. Bioinformatics analysis was conducted using public databases [The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx)]. In the experimental research, common CRC cell lines were selected, and CCL5 overexpression/knockdown models were established via lentiviral infection. Cell functions were assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), Cell Counting Kit-8 (CCK-8), Transwell, and scratch assays. Transcriptome sequencing was performed to screen differentially expressed genes (DEGs) and pathways. The regulatory role of STAT1 was validated through dual-luciferase reporter assays. Subcutaneous tumor xenograft models in nude mice were utilized to observe in vivo tumor growth.

Compared to paracancerous tissues, the expression of CCL5 is significantly downregulated in malignant tumor tissues. Further analysis within the tumor patient cohort revealed that CCL5 expression levels are positively correlated with the degree of tumor differentiation-specifically, higher in well-differentiated tumors and lower in poorly differentiated ones. More importantly, survival analysis demonstrated that patients with high CCL5 expression have a significantly longer overall survival than those with low expression.

We discovered through both in vivo and ex vivo tests that CCL5 overexpression significantly increased the CC cells' ability to proliferate, migrate, and invade, while CCL5 knockdown significantly reduced these malignant characteristics. Mechanistically, our research showed that CCL5 stimulates cancer cell migration, invasion, and proliferation by activating the PI3K/AKT signaling pathway, which advances CC progression. Furthermore, we discovered that STAT1 inhibits the production of CCL5. We found that CCL5 increases CC's ability to invade, migrate, and proliferate via activating the PI3K/AKT signaling pathway. Moreover, the upstream regulator of the CCL5 gene is STAT1.