Rad9 Protein Contributes to Prostate Tumor Progression by Promoting Cell Migration and Anoikis Resistance

• Published in: The Journal of biological chemistry 2012-11, Vol.287 (49), p.41324-41333
• Main Authors: Broustas, Constantinos G., Zhu, Aiping, Lieberman, Howard B.
• Format: Article
• Language: English
• Subjects: Anoikis; Cancer; Cell Adhesion; Cell Biology; Cell Cycle; Cell Cycle Proteins - metabolism; Cell Invasion; Cell Line, Tumor; Cell Migration; Cell Movement; Disease Progression; DNA Repair; Down-Regulation; Gene Expression Regulation, Neoplastic; Gene Silencing; Humans; Integrin beta1 - biosynthesis; Male; Migration; Neoplasm Invasiveness; Prostate; Prostate Cancer; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - pathology; Rad9; RNA Interference; Signal Transduction
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M112.402784

Rad9 as part of the Rad9-Hus1-Rad1 complex is known to participate in cell cycle checkpoint activation and DNA repair. However, Rad9 can act as a sequence-specific transcription factor, modulating expression of a number of genes. Importantly, Rad9 is up-regulated in prostate cancer cell lines and clinical specimens. Its expression correlates positively with advanced stage tumors and its down-regulation reduces tumor burden in mice. We show here that transient down-regulation of Rad9 by RNA interference reduces DU145 and PC3 prostate cancer cell proliferation and survival in vitro. In addition, transient or stable down-regulation of Rad9 impairs migration and invasion of the cells. Moreover, stable reduction of Rad9 renders DU145 cell growth anchorage-dependent. It also decreases expression of integrin β1 protein and sensitizes DU145 and LNCaP cells to anoikis and impairs Akt activation. On the other hand, stable expression of Mrad9, the mouse homolog, in DU145/shRNA Rad9 cells restores migration, invasion, anchorage-independent growth, integrin β1 expression, and anoikis resistance with a concomitant elevation of Akt activation. We thus demonstrate for the first time that Rad9 contributes to prostate tumorigenesis by increasing not only tumor proliferation and survival but also tumor migration and invasion, anoikis resistance, and anchorage-independent growth. Background: Rad9, a cell cycle checkpoint and DNA repair protein, is functionally related to human prostate tumorigenesis. Results: Rad9 deletion in prostate cancer cells impairs migration and invasion, sensitizes to anoikis, and down-regulates integrin β1. Conclusion: Rad9 controls ITGB1 expression, migration, invasion, and anoikis resistance of prostate cancer cells. Significance: This study reveals the significance of Rad9 in prostate tumor migration and invasion.