Acute lymphoblastic leukemia cells co-cultured with bone marrow stromal cells and primary human osteoblasts demonstrated decreased expression levels of miR-221 and miR-222, microRNAs that were described previously as leukemia cell proliferation regulators targeting the cell cycle inhibitor, CDKN1B (or p27). The gene discussed is CDKN1B; the disease is acute lymphoblastic leukemia.