CALB2 is a mechanoresistance gene in metastatic prostate cancer

Metastatic progression hinges on the ability of circulating tumor cells (CTCs) to withstand the extreme mechanical forces of the bloodstream, yet the mechanisms that enable this survival remain poorly defined. Understanding how prostate cancer (PCa) cells adapt to fluid shear stress (FSS) is essential for identifying vulnerabilities that could be leveraged to prevent metastatic spread. Here, we generate “mechanoresistant” (MR) LNCaP and PC3 PCa cell lines by repeatedly exposing cells to high‑intensity (HI) FSS (3950 dyn/cm²), modeling the forces encountered by CTCs in circulation. LNCaP MR cells acquire marked resistance to HI FSS, exhibiting significantly reduced apoptosis compared to controls, while PC3 cells demonstrate a more innate resistance. Morphologically, PC3 MR cells adopt an amoeboid phenotype, whereas LNCaP MR cells retain parental characteristics. Both MR populations show significantly increased Piezo1 expression. Bulk RNA‑sequencing reveals that LNCaP and PC3 MR cells developed distinct molecular programs. Notably, CALB2 (calretinin) emerges as a mechanoresistance gene selectively upregulated in PC3 MR cells, and CALB2 knockout significantly reduces viability upon re‑exposure to HI FSS. Analysis of CALB2‑high PCa cases capture patient‑level molecular heterogeneity, with reproducible co‑expression correlated with EPB41L3 and DGKI, suggesting a mechanoadaptive state rather than a uniform aggressiveness-driven tumor phenotype. This is consistent with the absence of correlation between CALB2 levels and Gleason Scores. In an orthotopic PCa mouse model, the PC3 MR condition displays the most aggressive early tumor growth and the largest endpoint tumor volumes, consistent with enhanced proliferation observed in vitro. Together, these findings demonstrate that PCa cells acquire discrete mechanoadaptive phenotypes under extreme shear stress, revealing targetable pathways that may ultimately be exploited to limit metastatic competence.