In the present study, our findings indicate that bortezomib-mediated inhibition of cell proliferation of chronic myelogenous leukemia cells (CML) cell lines is associated with down-regulation of SKP2 with concomitant up-regulation/stabilization of p27Kip1. The gene discussed is CDKN1B; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.