CDKN1B and acute lymphoblastic leukemia: ALL cells exposed to primary human bone marrow niche cells, including bone marrow stromal cells (BMSC) and primary human osteoblasts, show a decrease in miR-221 and -222 levels, with an increase of the target protein p27 (CDKN1B), leading to the accumulation of tumor cells in the G0 phase and resistance to chemotherapy-induced death [141].