This result is in contrast to the distinct expression signature of CD34+ chronic phase chronic myeloid leukemia patients failing to achieve a cytogenetic response on imatinib and suggests that deep molecular response to second-generation tyrosine kinase inhibitors is governed by the biology of more primitive chronic myeloid leukemia cells or extrinsic factors. This evidence concerns the gene CD34 and chronic myelogenous leukemia, BCR-ABL1 positive.