p38 mitogen-activated protein kinase-driven MAPKAPK2 regulates invasion of bladder cancer by modulation of MMP-2 and MMP-9 activity.

In transitional cell carcinoma, the most common form of bladder cancer, overexpression of the matrix metalloproteinases MMP-2 and MMP-9 offers prognostic value as markers of disease-specific survival. These molecules have been implicated in metastasis of bladder cancer, but the underlying mechanisms through which they are controlled are poorly defined. In this study, we investigated a role of p38 mitogen-activated protein kinase (MAPK) in this process, using bladder cancer cell lines HTB9 and HTB5 that were derived from different tumor stages. p38 MAPK modulated MMP-2/9 mRNA levels at the levels of transcript stability and MMP-2/9 activity along with invasive capacity. We defined a downstream effector of p38 MAPK, MAPK-activated protein kinase 2 (MAPKAPK2), that was associated with MMP-2/9 activation. Ectopic expression of wild-type or constitutively active forms of MAPKAPK2 increased MMP-2/9 activities and invasive capacity. Conversely, p38 MAPK inhibition blocked the MAPKAPK2-mediated increase in MMP-2/9 activities and the invasive capacity of the cancer cells. Our findings implicate p38 MAPK and MAPKAPK2 in mediating bladder cancer invasion via regulation of MMP-2 and MMP-9 at the level of mRNA stability.