Lessons taught by acute promyelocytic leukemia cure

Chromatin-Based Classification of Genetically Heterogeneous AMLs into Two Distinct Subtypes with Diverse Stemness Phenotypes

Global investigation of histone marks in acute myeloid leukemia (AML) remains limited. Analyses of 38 AML samples through integrated transcriptional and chromatin mark analysis exposes 2 major subtypes. One subtype is dominated by patients with NPM1 mutations or MLL-fusion genes, shows activation of the regulatory pathways involving HOX-family genes as targets, and displays high self-renewal capacity and stemness. The second subtype is enriched for RUNX1 or spliceosome mutations, suggesting potential interplay between the 2 aberrations, and mainly depends on IRF family regulators. Cellular consequences in prognosis predict a relatively worse outcome for the first subtype. Our integrated profiling establishes a rich resource to probe AML subtypes on the basis of expression and chromatin data.

Acute myeloid/T-lymphoblastic leukaemia (AMTL): a distinct category of acute leukaemias with common pathogenesis in need of improved therapy

Advances in the classification of acute leukaemias have led to improved outcomes for a substantial fraction of patients. However, chemotherapy resistance remains a major problem for specific subsets of acute leukaemias. Here, we propose that a molecularly distinct subtype of acute leukaemia with shared myeloid and T cell lymphoblastic features, which we term acute myeloid/T-lymphoblastic leukaemia (AMTL), is divided across 3 diagnostic categories owing to variable expression of markers deemed to be defining of myeloid and T-lymphoid lineages, such as myeloperoxidase and CD3. This proposed diagnostic group is supported by (i) retained myeloid differentiation potential during early T cell lymphoid development, (ii) recognition that some cases of acute myeloid leukaemia (AML) harbour hallmarks of T cell development, such as T-cell receptor gene rearrangements and (iii) common gene mutations in subsets of AML and T cell acute lymphoblastic leukaemia (T-ALL), including WT1, PHF6, RUNX1 and BCL11B. This proposed diagnostic entity overlaps with early T cell precursor (ETP) T-ALL and T cell/myeloid mixed phenotype acute leukaemias (MPALs), and also includes a subset of leukaemias currently classified as AML with features of T-lymphoblastic development. The proposed classification of AMTL as a distinct entity would enable more precise prospective diagnosis and permit the development of improved therapies for patients whose treatment is inadequate with current approaches.

p53 as an Effector or Inhibitor of Therapy Response

Although integrity of the p53 signaling pathway in a given tumor was expected to be a critical determinant of response to therapies, most clinical studies failed to link p53 status and treatment outcome. Here, we present two opposite situations: one in which p53 is an essential effector of cure by targeted leukemia therapies and another one in advanced breast cancers in which p53 inactivation is required for the clinical efficacy of dose-dense chemotherapy. If p53 promotes or blocks therapy response, therapies must be tailored on its status in individual tumors.