Linking miRNA regulation to BCR-ABL expression: the next dimension.

The introduction of tyrosine kinase inhibitors in the treatment of BCR-ABL1-rearranged malignancies has revolutionized therapy, but the prognosis for acute leukemias remains suboptimal. In this issue of Cancer Cell, Bueno et al. (2008) add a new dimension to the regulation of ABL1 expression. The authors demonstrate that ABL1 is a direct target of miR-203, miR-203 is silenced by genetic and epigenetic mechanisms in hematopoietic malignancies expressing either ABL1 or BCR-ABL1, and restoration of miR-203 expression reduces ABL1 and BCR-ABL1 levels and inhibits cell proliferation. These findings may have broad implications for mechanisms underlying malignant transformation in hematopoietic and other malignancies.