CDK5 and cancer: Blockade of Cdk5 can remarkably downregulate the two active forms of Ral proteins RalA-GTP and RalB-GTP, and Rho-GTP and Rac-GTP levels, all of which play an important role in oncogenic Ras-induced neoplasia, tumor progression and metastasis, revealing the important roles of Cdk5 in cancer progression [67].