RhoGDIβ promotes Sp1/MMP-2 expression and bladder cancer invasion through perturbing miR-200c-targeted JNK2 protein translation.

Our most recent studies demonstrate that RhoGDIβ is able to promote human bladder cancer (BC) invasion and metastasis in an X-link inhibitor of apoptosis protein-dependent fashion accompanied by increased levels of matrix metalloproteinase (MMP)-2 protein expression. We also found that RhoGDIβ and MMP-2 protein expressions are consistently upregulated in both invasive BC tissues and cell lines. In the present study, we show that knockdown of RhoGDIβ inhibited MMP-2 protein expression accompanied by a reduction of invasion in human BC cells, whereas ectopic expression of RhoGDIβ upregulated MMP-2 protein expression and promoted invasion as well. The mechanistic studies indicated that MMP-2 was upregulated by RhoGDIβ at the transcriptional level by increased specific binding of the transcription factor Sp1 to the mmp-2 promoter region. Further investigation revealed that RhoGDIβ overexpression led to downregulation of miR-200c, whereas miR-200c was able directly to target 3'-UTR of jnk2mRNA and attenuated JNK2 protein translation, which resulted in attenuation of Sp1mRNA and protein expression in turn, inhibiting Sp1-dependent mmp-2 transcription. Collectively, our studies demonstrate that RhoGDIβ overexpression inhibits miR-200c abundance, which consequently results in increases of JNK2 protein translation, Sp1 expression, mmp-2 transcription, and BC invasion. These findings, together with our previous results showing X-link inhibitor of apoptosis protein mediating mRNA stabilization of both RhoGDIβ and mmp-2, reveal the nature of the MMP-2 regulatory network, which leads to MMP-2 overexpression and BC invasion.

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