Genistein Inhibits Matrix Metalloproteinase Type 2 Activation and Prostate Cancer Cell Invasion by Blocking the Transforming Growth Factor -Mediated Activation of Mitogen-Activated Protein Kinase-Activated Protein Kinase 2–27-kDa Heat Shock Protein Pathway

Genistein is a candidate cancer chemopreventive drug being tested in clinical trials. We have shown that genistein blocks prostate cancer (PCa) cell invasion, that p38 mitogen-activated protein (MAP) kinase regulates activation of matrix metalloproteinase type 2 (MMP-2) and cell invasion, and that genistein prevents transforming growth factor (TGF ) from activating p38 MAP kinase. More recently, we identified MAP kinaseactivated protein kinase 2 (MAPKAPK2) and the 27-kDa heat shock protein (HSP27) as downstream regulators of p38 MAP kinase. However, MAPKAPK2 and HSP27 can be regulated by factors other than p38 MAP kinase, and HSP27 is up-regulated during PCa progression. The current study was undertaken to examine the role of MAPKAPK2 and HSP27 in modulating genistein-mediated regulation of PCa cell invasion. Genistein inhibited TGF -mediated phosphorylation of MAPKAPK2 and HSP27. Inhibitory effects by genistein upon cell signaling, inhibition of MMP-2, and inhibition of invasion were retained when both PC3 and PC3-M cells were transfected with either wildtype MAPKAPK2 or HSP27. However, transfection with dominant-negative MAPKAPK2 or nonphosphorylatable mutant HSP27 led to decreases in cell invasion and to abrogation of responsiveness to either TGF -mediated increases or genistein-mediated decreases in MMP-2 and cell invasion. It is noteworthy that, after transfection with constitutive active MAPKAPK2 or with pseudophosphorylated HSP27, levels of MMP-2 activation and cell invasion were high and overcame any inhibitory effect of genistein. These findings demonstrate that genistein-mediated inhibition of cell invasion rests upon blocking activation of the MAPKAPK2-HSP27 pathway, and that its activation during cancer progression has the potential to mitigate therapeutic efficacy. Among American men, prostate cancer (PCa) is the most common invasive malignancy (Jemal et al., 2005). Despite increased surveillance and early detection, PCa is still ranked second as a cause of cancer-related death. New forms of therapy are thus needed. Genistein (4 ,5,7-trihydroxyflavone) is a predominant constituent of soy and is a potential PCa chemopreventive agent (Davis et al., 2000; Bergan et al., 2001). Phase 1 trials of genistein in men with PCa have been completed by us (Takimoto et al., 2003) and others (Mills et al., 1989; Knight and Eden, 1996; Busby et al., 2002; Dalais et al., 2004; Fischer et al., 2004), and phase 2 efficacy trials are under way. To optimize clinical development, it is important to understand the molecular pharmacology of genistein, particularly as it relates to