Clonal origins of relapse in ETV6-RUNX1 acute lymphoblastic leukemia

B-cell precursor childhood acute lymphoblastic leukemia with ETV6-RUNX1 (TEL-AML1) fusion has an overall good prognosis, but relapses occur, usually after cessation of treatment and occasionally many years later. We have investigated the clonal origins of relapse by comparing the profiles of genomewide copy number alterations at presentation in 21 patients with those in matched relapse (12-119 months). We identified, in total, 159 copy number alterations at presentation and 231 at relapse (excluding Ig/TCR). Deletions of CDKN2A/B or CCNC (6q16.2-3) or both increased from 38% at presentation to 76% in relapse, suggesting that cell-cycle deregulation contributed to emergence of relapse. A novel observation was recurrent gain of chromosome 16 (2 patients at presentation, 4 at relapse) and deletion of plasmocytoma variant translocation 1 in 3 patients. The data indicate that, irrespective of time to relapse, the relapse clone was derived from either a major or minor clone at presentation. Backtracking analysis by FISH identified a minor subclone at diagnosis whose genotype matched that observed in relapse ～ 10 years later. These data indicate subclonal diversity at diagnosis, providing a variable basis for intraclonal origins of relapse and extended periods (years) of dormancy, possibly by quiescence, for stem cells in ETV6-RUNX1(+) acute lymphoblastic leukemia.     

Clinical and genetic studies of ETV6/ABL1-positive chronic myeloid leukaemia in blast crisis treated with imatinib mesylate

Most chronic myeloid leukaemia (CML) patients are genetically characterized by the t(9;22)(q34;q11), generating the BCR/ABL1 fusion gene. However, a few CML patients with rearrangements of 9q34 and 12p13, leading to ETV6/ABL1 chimaeras, have also been reported. Here we describe the clinical and genetic response to imatinib mesylate treatment of an ETV6/ABL1-positive CML patient diagnosed in blast crisis (BC). A chronic phase was achieved after acute myeloid leukaemia induction therapy. Then, treatment with imatinib mesylate (600 mg/d) was initiated and the effect was assessed clinically as well as genetically, including by repeated interphase fluorescence in situ hybridization studies. Until d 71 of imatinib mesylate therapy, stable improvements in the clinical and laboratory features were noted, and the frequency of ABL1-rearranged peripheral blood cells decreased from 56% to 11%. At d 92, an additional t(12;13)(p12;q13), with the 12p breakpoint proximal to ETV6, was found. The patient relapsed into BC 126 d after the start of the imatinib mesylate treatment and succumbed to the disease shortly afterwards. No mutations in the tyrosine kinase domain of ABL1 of the ETV6/ABL1 fusion were identified in the second BC. However, whereas the ETV6/ABL1 expression was seemingly the same at diagnosis and at second BC, the expression of ETV6 was markedly lower at the second BC. This decreased expression of wild-type ETV6 may have been a contributory factor for the relapse.     

Chronic myeloid leukemia presenting ALL-type BCR/ABL transcript

Summary We assessed the origin of peripheral blood cells and bone marrow cells of 92 samples obtained from 19 patients after allo BMT by two-step polymerase chain reaction (PCR) amplification of MCT118, one of the variable number of tandem repeat regions (VNTR) which has a different length in 19 of 32 sibling pairs examined, that can detect the DNA pattern of a minor cell population of only 1% without using radioisotopes. Mixed chimerism (MC) was detected in the hematopoietic cells of four patients. Two patients who showed progressive MC developed relapse of leukemia 3 months and 4 months after the detection of MC, and two patients died with bone marrow hypoplasia 61 days and 7 months after BMT. These data suggest the clinical importance of analyzing the correlation of MC and clinical complications after BMT by this method, which can be used to monitor MC in about two thirds of allo BMT patients with an adequate sensitivity.     

Copy number genome alterations are associated with treatment response and outcome in relapsed childhood ETV6/RUNX1-positive acute lymphoblastic leukemia

The clinical heterogeneity among first relapses of childhood ETV6/RUNX1-positive acute lymphoblastic leukemia indicates that further genetic alterations in leukemic cells might affect the course of salvage therapy and be of prognostic relevance. To assess the incidence and prognostic relevance of additional copy number alterations at relapse of the disease, we performed whole genome array comparative genomic hybridization of leukemic cell DNA from 51 patients with first ETV6/RUNX1-positive relapse enrolled in and treated according to the relapse trials ALL-REZ of the Berlin-Frankfurt-Münster Study Group. Within this cohort of patients with relapsed ETV6/RUNX1-positive acute lymphoblastic leukemia, the largest analyzed for genome wide DNA copy number alterations to date, alterations were present in every ETV6/RUNX1-positive relapse and a high proportion of them occurred in recurrent overlapping chromosomal regions. Recurrent losses affected chromosomal regions 12p13, 6q21, 15q15.1, 9p21, 3p21, 5q and 3p14.2, whereas gains occurred in regions 21q22 and 12p. Loss of 12p13 including CDKN1B was associated with a shorter remission duration (P=0.009) and a lower probability of event-free survival (P=0.001). Distribution of X-chromosomal copy number alterations was gender-specific: whole X-chromosome loss occurred exclusively in females, gain of Xq only in males. Loss of the glucocorticoid receptor gene NR3C1 (5q31.3) was associated with a poor response to induction treatment (P=0.003), possibly accounting for the adverse prognosis of some of the ETV6/RUNX1-positive relapses.     

Blood outgrowth endothelial cells from chronic myeloid leukaemia patients are BCR/ABL1 negative

The existence of adult haemangioblasts with dual haematopoietic and endothelial developmental potential was confirmed after detection of Ph⁺ vascular endothelial cells in chronic myeloid leukaemia (CML) patients. Blood outgrowth endothelial cells (OECs) from CML patients were found not to harbour the Philadelphia translocation and were thus not clonally related to BRC/ABL1 ⁺ hematopoietic progenitors, but comprised a distinct subfraction of endothelial cells. Remarkably, the frequency of CML-derived OECs was 9-fold higher as compared to healthy donors ( n  = 19 and n  = 300, respectively; P  <   0·0001) and these cells showed increased proliferative potential, possibly reflecting the mobilisation of OEC progenitors by pro-angiogenic cytokines.