Fu-Zheng-Yi-Liu formula inhibits the stem cells and metastasis of prostate cancer via tumor-associated macrophages/C-C motif chemokine ligand 5 pathway in tumor microenvironment

Prostate cancer (PCa) represents the second most frequent malignancy among males worldwide. Metastasis is the primary reason for death in PCa patients. Fu-Zheng-Yi-Liu (FZYL) formula has been extensively used for PCa treatment with encouraging therapeutic efficiency and few adverse effects. However, the underlying action mechanisms remain to be uncovered. Our previous study has proven that C-C motif chemokine ligand 5 (CCL5) derived from tumor-associated macrophages (TAMs) could significantly promote the self-renewal of prostate cancer stem cells (PCSCs) and PCa bone metastasis. This study aimed to explore whether FZYL formula could restrain PCa by suppressing TAMs/CCL5 pathway. Herein, PCa cells and TAMs were co-cultured in vitro or co-injected in vivo to simulate their coexistence. It was found that FZYL formula dramatically restrained the proliferation, colony formation, PCSCs subpopulations, and the sphere-formation efficacies of PCa cells even in the presence of TAMs co-culture. Furthermore, FZYL formula remarkably suppressed the migration, invasion, and epithelial-mesenchymal transition (EMT) of PCa cells induced by TAMs. Moreover, FZYL formula reversed the M2 phenotype polarization of TAMs and transcriptionally attenuated their CCL5 expression and secretion in a dose-dependent manner, while exhibiting little cytotoxicity in TAMs. Notably, mechanistic investigations validated TAMs/CCL5 as the crucial target of FZYL formula in suppressing PCSCs self-renewal in the co-culture system since exogenous CCL5 addition partly abrogated the suppressive effect of FZYL formula on that. More importantly, FZYL formula also remarkably restrained PCa xenografts growth, bone metastasis and PCSCs activity in vivo by suppressing TAMs/CCL5 pathway. Altogether, this study not only reveals the immunomodulatory mechanism of FZYL formula in PCa treatment but also provides novel insights into TAMs/CCL5 as a promising druggable target. (Fig. 1 is a graphical abstract).