PLK1 and myeloid leukemia: In myeloid leukemia miR-126 was found to down-regulate HOXA9, an oncogene encoding a transcription factor that regulates hematopoietic development [27], while Cammarata and colleagues found that miR-126, upregulated in acute myeloid leukemia, induced cell proliferation via the inhibition of PLK, one member of the Polo-like kinase that regulates the cell cycle [28].