Tumor Budding-Derived CCL5 Recruits Fibroblasts to Promote Colorectal Cancer Progression Through CCR5-SLC25A24 Signaling

Abstract Background: Tumor buddings have been included in the routine diagnosis of colorectal cancer (CRC) and considered to be a tumor prognostic factor independent of TNM staging. This study aimed at identifying the contribution of tumor budding-derived C-C chemokine ligand 5 (CCL5) to tumor microenvironment (TME) through fibroblasts. Methods: Co-cultivation recruitment assays and human cytokine array were used to detect the main cytokine derived from CRC tumor buddings to recruit fibroblasts. siRNA transfection and inhibitor treatment were applied to investigate the effective receptor of CCL5 on fibroblasts. Transcriptome sequencing was performed to explore the mechanism inside fibroblasts when stimulated by CCL5. Stimulation with CCL5 in vitro, orthotopic xenograft mouse model and clinical specimens were designed to clarify the contribution of CCL5 to angiogenesis and collagen synthesis.Results: H&E and immunochemistry staining confirmed that CRC with tumor buddings in the invasive front was accompanied by more fibroblasts compared with CRC without tumor buddings. Further vitro study indicated that CCL5 derived from tumor buddings could recruit fibroblasts through CCR5 receptor on fibroblasts and positively regulate solute carrier family 25 member 24 (SLC25A24) expression in fibroblasts, which could activate pAkt-pmTOR signaling. Moreover, CCL5 can increase the number of α-SMA+CD90+FAP- fibroblasts to promote tumor angiogenesis through enhancing the expression of VEGFA and making fibroblasts transdifferentiate into vascular endothelial cells. Meanwhile, CCL5 also can promote collagen synthesis through fibroblasts, thus contributing to tumor progression.Conclusions: In the invasive front of CRC, tumor-budding-derived CCL5 can recruit fibroblasts through CCR5-SLC25A24 signaling, further promoting angiogenesis and collagen synthesis through fibroblasts, eventually creating a tumor-promoting microenvironment.