Abstract 5330: Leukemia initiating cells are frequent and oligoclonal in de novo resistant ALL

Abstract

Abstract Xenotransplantation of primary leukemia cells constitutes an attractive strategy to model disease for translational research, but the consequences of selective pressure on leukemia cells need to be clarified. Here we evaluate the phenotypic and genetic stability of primograft samples that were established by xenotransplantation of ALL cells from a group of patients with very high-risk precursor B-cell ALL, characterized by the persistence of minimal residual disease (VHR-ALL by MRD) after an intensive induction and consolidation therapy. Phenotypic properties remained unchanged, with concordant immunophenotypes in 9-10/10 leukemia-associated markers after up to 5 passages in Nod/scidIL2Rgammanull (NSG) mice and with stable drug response profiles in vitro on bone marrow stroma co-cultures. In 4/6 cases, 100 unsorted ALL cells were sufficient to reconstitute the leukemia. From up to 5 recurrent copy number abnormalities (CNA) detected in diagnostic samples, most were maintained in primografts. Changes in CNAs upon transplantation in NSG mice were few with 0-2 new lesions per case, mostly occurring during the first xenotransplantation. At the single cell level, the pattern of deletions in the CDKN2A/B locus revealed distinct subsets of ALL cells, which could reproducibly be tracked in primografts. These results provide unequivocal data for the existence of clonally closely related but distinct subsets of leukemia initiating cells in ALL, which has important implications for the use of this model for translational research. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5330. doi:10.1158/1538-7445.AM2011-5330