RUNX1 and acute myeloid leukemia: Although additional let-7b targets likely also contribute, these results agree with previous studies showing that directly silencing AML1-ETO with siRNA or shRNA releases the AML1-ETO mediated differentiation block of t(8;21) AML cells as evidenced by down-regulation of the hematopoietic stem cell marker CD34, and up-regulation of more mature myeloid markers such as CD38, CD33, and CD13 [28–30, 32, 33].