HYPOXIA SUPPRESSES BCR/ABL AND SELECTS IMATINIB-INSENSITIVE PROGENITORS WITHIN CLONAL CML POPULATIONS.

We previously showed that severe hypoxia enhances the maintenance, in vitro, of normal stem cells capable of shortterm hematopoietic reconstitution (Cipolleschi et al.,1,2 Ivanovic´ et al.,3 and references therein), and that resistance to hypoxia defines hierarchical levels within hematopoietic populations. The study summarized here addressed the questions (a) whether cell subsets endowed with different levels of sensitivity to severe hypoxia were identifiable within clonal chronic myeloid leukemia (CML) cell populations and (b) whether such subsets differed as for BCR/Abl expression and sensitivity to imatinibmesylate.