MEIS1 and nonpapillary renal cell carcinoma: To investigate how MEIS1 regulates cell cycle, we tested whether MEIS1 modulates the endogenous expression of positive G1/S transition regulators, Cyclin D1 and Cyclin A. As shown in Fig. 8, MEIS1 overexpression decreased Cyclin A and Cyclin D1 in ccRCC cells (Fig. 8a, b).