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Cytogenetic and molecular investigations of Acute Lymphoblastic Leukaemia (ALL) have identified the existence of distinct clinical subgroups. Molecular monitoring of clonal Immunoglobulin and T cell receptor (IG/TR) gene rearrangements has become an important tool in stratification of therapy of ALL. In order to determine whether certain features of the patient-specific rearrangements could hold further prognostic clues or provide information on the cell of origin of ALL, a comprehensive analysis of structural and biological features (V gene usage, coding frame and mutational status and complementarity-determining region -III length) of 473 IG/TR rearrangements identified in 229 adults with ALL was carried out. Distinct variable-gene usage profiles were identified between ALL subgroups, particularly for patients positive for BCR-ABL1 compared to MLL-AFF1 positive leukaemias; suggesting that the former is derived from a more mature B progenitor. Interestingly, occurrence of TRGV1- TRGV8 was prognostic for better event-free survival (31% at 4 years with vs. 0% at 4 years without, P = 0·05). The heterogeneity in clinical outcome is suggested by the basic molecular processes of antigen receptor gene rearrangements as shown in this work. [ABSTRACT FROM AUTHOR]

The predictive value of molecular minimal residual disease (MRD) monitoring using polymerase chain reaction amplification of clone-specific immunoglobulin or T-cell Receptor rearrangements was analysed in 161 patients with non T-lineage Philadelphia-negative acute lymphoblastic leukaemia (ALL) participating in the UK arm of the international ALL trial UKALL XII/Eastern Cooperative Oncology Group (ECOG) 2993. MRD positivity (≥10−4) in patients treated with chemotherapy alone was associated with significantly shorter relapse-free survival (RFS) at several time-points during the first year of therapy. MRD status best discriminated outcome after phase 2 induction, when the relative risk of relapse was 8·95 (2·85–28·09)-fold higher in MRD-positive (≥10−4) patients and the 5-year RFS 15% [95% confidence interval (CI) 0–40%] compared to 71% (56–85%) in MRD-negative (<10−4) patients ( P = 0·0002) When MRD was detected prior to autologous stem cell transplantation (SCT), a significantly higher rate of treatment failure was observed [5-year RFS 25% (CI 0–55%) vs. 77% (95% CI 54–100%) in MRD-negative/<10−4, P = 0·01] whereas in recipients of allogeneic-SCT in first complete remission, MRD positivity pre-transplant did not adversely affect outcome. These data provide a rationale for introducing MRD-based risk stratification in future studies for the delineation of those at significant risk of treatment failure in whom intensification of therapy should be evaluated. [ABSTRACT FROM AUTHOR]

The distinct nature of acute lymphoblastic leukemia (ALL) in adults, evidenced by inferior treatment outcome and different genetic landscape, mandates specific studies of disease-initiating mechanisms. In this study, we used NOD/LtSz-scid IL2Rγ nullc (NSG) mouse xenotransplantation approaches to elucidate leukemia-initiating cell (LIC) biology in primary adult precursor B (pre-B) ALL to optimize disease modeling. In contrast with xenografting studies of pediatric ALL, we found that modification of the NSG host environment using preconditioning total body irradiation (TBI) was indispensable for efficient engraftment of adult non-t(4;11) pre-B ALL, whereas t(4;11) pre-B ALL was successfully reconstituted without this adaptation. Furthermore, TBI-based xenotransplantation of non-t(4;11) pre-B ALL enabled detection of a high frequency of LICs (<1:6900) and permitted frank leukemic engraftment from a remission sample containing drug-resistant minimal residual disease. Investigation of TBI-sensitive stromal-derived factor-1/ chemokine receptor type 4 signaling revealed greater functional dependence of non-t(4;11) pre-B ALL on this niche-based interaction, providing a possible basis for the differential engraftment behavior. Thus, our studies establish the optimal conditions for experimental modeling of human adult pre-B ALL and demonstrate the critical protumorogenic role of microenvironment-derived SDF-1 in regulating adult pre-B LIC activity that may present a therapeutic opportunity. [ABSTRACT FROM AUTHOR]