Macrophage-derived CTSZ promotes prostate cancer progression via αVβ3 integrin-mediated activation of the AKT/FOXO1/JUNB signaling axis

Background The tumor microenvironment (TME), particularly tumor-associated macrophages (TAMs), plays a critical role in prostate cancer (PCa) progression. Cathepsin Z (CTSZ), a lysosomal protease, has been implicated in various cancers, but its specific function and mechanism within the PCa TAMs remain largely unexplored. Methods We analyzed single-cell RNA sequencing data (GSE141445, GSE137829) to identify CTSZ expression patterns. Immunofluorescence co-localization in human PCa tissues and in vitro experiments (qPCR, Western blot, flow cytometry) using THP-1-derived macrophages overexpressing CTSZ were performed to validate its role in macrophage polarization. The functional impact of CTSZ-polarized macrophages on PCa cell (PC3) malignant behaviors (proliferation, migration, invasion) was assessed via EdU, CCK-8, colony formation, scratch, and Transwell assays in vitro, and through orthotopic and lung metastasis models in vivo. RNA sequencing of treated tumor cells was conducted to identify downstream pathways. Mechanistic insights were gained using CTSZ-neutralizing antibodies, recombinant CTSZ protein, and the αVβ3 integrin inhibitor Cilengitide (Cyclo), followed by Western blot, co-immunoprecipitation, and dual-luciferase reporter assays. Results CTSZ was predominantly and highly expressed in macrophages within PCa tissues. Overexpression of CTSZ in macrophages promoted their M2 polarization, as evidenced by increased CD163 and decreased CD86/iNOS expression. Conditioned medium from OE-CTSZ macrophages significantly enhanced the proliferation, migration, and invasion of PCa cells, and boosted tumor growth and metastasis in mouse models. RNA sequencing revealed significant enrichment in the TNF signaling pathway and marked downregulation of JUNB. Mechanistically, macrophage-derived CTSZ bound to the αVβ3 integrin receptor on tumor cells, activating the AKT/FOXO1 signaling axis, leading to phosphorylation of FOXO1 and subsequent transcriptional repression of JUNB. These pro-tumorigenic effects were effectively reversed by either a CTSZ-neutralizing antibody or the αVβ3 inhibitor. Conclusion Our study unveils a novel pathway wherein macrophage-derived CTSZ promotes PCa progression by driving M2 macrophage polarization and directly activating the αVβ3/AKT/FOXO1 axis in tumor cells, culminating in JUNB downregulation. Targeting the CTSZ/αVβ3 interaction may represent a promising therapeutic strategy for PCa.