M2 macrophages drive prostate cancer invasion via M-CSF-induced PCLAF upregulation

Advanced and castration-resistant prostate cancer (CRPC) remains a significant challenge, with the tumor microenvironment (TME) playing a critical role in its progression. Tumor-associated macrophages (TAMs), particularly the M2 phenotype, are known to foster an immunosuppressive and pro-tumorigenic milieu. Our prior research identified that M2 TAMs in PCa upregulate M-CSF secretion. This study addresses the crucial gap of identifying the specific downstream effector within prostate cancer (PCa) cells that mediates these M-CSF-driven tumor-promoting effects, aiming to uncover novel therapeutic targets.

Researchers investigated the impact of M-CSF on PCa cell behavior using the PC3 cell line. Cell viability, invasion, and migration were assessed via CCK-8, Transwell, and wound healing assays. To identify M-CSF-regulated proteins, a comprehensive DIA-PASEF proteomic analysis was performed on PC3 cells treated with or without M-CSF. Bioinformatic screening identified differentially expressed proteins. Key candidate PCLAF was validated using Western blot, analysis of TCGA-PRAD data, and immunohistochemistry on a prostate tissue microarray from 79 patients. The functional role of PCLAF was confirmed through in vitro experiments and an in vivo xenograft model in nude mice, comparing PC3 control cells, PC3 cells overexpressing KIAA0101/PCLAF, and PC3 cells with local M-CSF injections.

M-CSF stimulation significantly enhanced PC3 cell viability, invasion, and migration in a concentration-dependent manner. Proteomic analysis revealed 95 differentially expressed proteins following M-CSF treatment. Among the top candidates, PCLAF/KIAA0101 was the only protein consistently and significantly upregulated by M-CSF in validation experiments. Analysis of TCGA data confirmed PCLAF's significant overexpression in PCa tumors and its association with poorer disease-free survival. Tissue microarray analysis demonstrated that PCLAF expression was significantly higher in PCa tissues compared to benign tissues and positively correlated with PCa progression. In vitro, PCLAF overexpression alone significantly promoted PC3 cell invasion and migration, mimicking M-CSF's effects. Conversely, PCLAF knockdown abrogated M-CSF-induced invasion. In the nude mouse xenograft model, local M-CSF injections significantly promoted tumor growth and metastasis, effects that were substantially attenuated by PCLAF knockdown. Furthermore, tumors from PC3 cells overexpressing PCLAF showed significantly increased growth and metastatic potential compared to controls. This study establishes PCLAF as a critical downstream effector of the M-CSF pathway in PCa progression.

M-CSF stimulation significantly enhanced PC3 cell viability, invasion, and migration, with PCLAF identified as the key upregulated protein driving these pro-tumorigenic effects.