Luger, S. M.

Abstract Cytokine receptor–like factor 2 rearrangement (CRLF2r), an aberration causing a Philadelphia chromosome–like gene expression profile and a poor prognostic marker in B-cell acute lymphoblastic leukemia (B-ALL), endows relative chemotherapeutic resistance. Extramedullary disease (EMD), including both central nervous system (CNS) and non-CNS involvement, can also be associated with worse outcomes. The relationship between CRLF2r and EMD is unknown. Based on an initial observation of patients with relapsed/refractory (R/R) CRLF2r B-ALL and EMD, a single-center retrospective review was conducted to evaluate the incidence of EMD in patients with CRLF2r B-ALL. Across 177 children, adolescents, and young adults with R/R B-ALL, 21 (11.9%) harbored CRLF2r, of whom 19 (90.5%) had EMD at some point during their treatment course. In contrast, only 78 of the 156 patients (50%) without CRLF2r ever had EMD (P = .0003). In the CRLF2r cohort, 8 (38.1%) presented with EMD at diagnosis: 7 with CNS and 1 with non-CNS EMD. At relapse, 17 (80.9%) had EMD: 4 (19%) had CNS EMD, 9 (42.9%) had non-CNS EMD, and 4 (19%) had both. Isolated EMD was observed in 2 patients (11.8%) at first relapse and in 3 (17.6%) with multiple relapses. Given these findings, further study to evaluate this potential association between EMD and CRLF2r in R/R B-ALL is indicated.

CD25 is a subunit of the interleukin-2 (IL-2) receptor on T cells and natural killer (NK) cells. Acute leukemias with oncogenic tyrosine kinases often include CD25 + leukemia subpopulations, which portend poor clinical outcomes for patients; however, acute leukemia cells do not respond to IL-2. Here, we identified CD25 and its phosphorylation by protein kinase Cδ (PKCδ) as central elements of a feedback loop that stabilized fluctuations in oncogenic tyrosine kinase signaling in acute lymphoblastic and myeloid leukemia. Genetic ablation of CD25 in murine and patient-derived xenograft (PDX) models of acute leukemias reduced clonal fitness, colony formation, and leukemia-initiation capacity in serial transplant recipients. Oncogenic tyrosine kinase signaling in leukemia cells stimulated NF-κB–mediated CD25 expression, whereas PKCδ-mediated phosphorylation of CD25 suppressed oncogenic tyrosine kinase signaling through inhibitory phosphatases, such as PTPN6. Interactome analyses and mass spectrometry–based global phosphoproteomic analyses showed that CD25 deletion abolished the phosphatase activity of PTPN6, resulting in enhanced activation of tyrosine kinases and NF-κB. Four injections of a CD25 antibody-drug conjugate induced complete remission in mice transplanted with PDX refractory leukemia. These findings highlight the dependency of tyrosine kinase–driven leukemias on robust feedback control and the role of PKCδ and CD25 in assembling its components.

7003 Background: In younger adults with newly diagnosed acute myeloid leukemia (AML), anthracycline dose intensification during induction may improve complete remission (CR) rates; however, an improvement in overall survival (OS) in a randomized trial has not been demonstrated. This unresolved issue led the ECOG to compare standard dose (SDD) to high-dose daunorubicin (HDD) in induction. Methods: Adult patients with previously untreated AML were randomized to receive either SDD (45 mg/m2/d) or HDD (90 mg/m2/d) each for 3days combined with standard-dose cytarabine (100 mg/m2/d) for 7 days by continuous intravenous infusion. Those achieving a CR were allocated to allogeneic hematopoietic stem cell transplantation (HSCT) or high-dose cytarabine (with or without a single dose of gemtuzumab ozogamicin) prior to autologous HSCT. Intravenous busulfan and cyclophosphamide was the preparative regimen for both allogeneic and autologous HSCT. The primary end point of this study was OS from the time of induction randomization. Results: 633 patients, age 18 to 60 (median 48) years, were entered in this study. There were no differences in patient demographics or disease characteristics between the two groups at presentation. In an intention-to-treat analysis, HDD resulted in a significantly higher CR rate (63.3% vs. 47.7%, p = 0.0003) than SDD. Induction deaths were similar between the two groups (5.4 vs. 5.0%, p = ns). 334 (52.8%) patients entered the consolidation phase. 57.4% of HDD and 48.1% of the SDD patients, received consolidation therapy on study, and 28.7% and 23.1% proceeded to HSCT respectively. Median OS was superior for the HDD (23.7 months) over the SDD (15.1 months) group (p = 0.005). In subgroup analysis, patients with favorable or intermediate-risk cytogenetics or age <55 years benefited from the HDD. Conclusions: We demonstrate for the first time in a prospective randomized trial that intensifying induction therapy through a higher daily anthracycline dose, in the setting of identical intensive consolidation therapy, results in a higher CR rate as well as prolonged OS. In younger AML patients a higher dose of anthracycline in induction should be considered the new standard of care. No significant financial relationships to disclose.