MMP9 and prostate cancer: Whereas most of the effect of GSK3α knockdown on prostate cancer micrometastasis may come from the effect of GSK3α deficiency on apoptosis and proliferation, a role for GSK3α in EMT and micrometastasis cannot be ruled out based on the effect of GSK3α gene knockdown on the expression of EMT markers such as N-cadherin and MMP9.