Retargeting of NK-92 Cells against High-Risk Rhabdomyosarcomas by Means of an ERBB2 (HER2/Neu)-Specific Chimeric Antigen Receptor.

The dismal prognosis of pediatric and young adult patients with high-risk rhabdomyosarcoma (RMS) underscores the need for novel treatment options for this patient group. In previous studies, the tumor-associated surface antigen ERBB2 (HER2/neu) was identified as targetable in high-risk RMS. As a proof of concept, in this study, a novel treatment approach against RMS tumors using a genetically modified natural killer (NK)-92 cell line (NK-92/5.28.z) as an off-the-shelf ERBB2-chimeric antigen receptor (CAR)-engineered cell product was preclinically explored. In cytotoxicity assays, NK-92/5.28.z cells specifically recognized and efficiently eliminated RMS cell suspensions, tumor cell monolayers, and 3D tumor spheroids via the ERBB2-CAR even at effector-to-target ratios as low as 1:1. In contrast to unmodified parental NK-92 cells, which failed to lyse RMS cells, NK-92/5.28.z cells proliferated and became further activated through contact with ERBB2-positive tumor cells. Furthermore, high amounts of effector molecules, such as proinflammatory and antitumoral cytokines, were found in cocultures of NK-92/5.28.z cells with tumor cells. Taken together, our data suggest the enormous potential of this approach for improving the immunotherapy of treatment-resistant tumors, revealing the dual role of NK-92/5.28.z cells as CAR-targeted killers and modulators of endogenous adaptive immunity even in the inhibitory tumor microenvironment of high-risk RMS.

More precisely defining risk peri-HCT in pediatric ALL: pre- vs post-MRD measures, serial positivity, and risk modeling.

Detection of minimal residual disease (MRD) pre- and post-hematopoietic cell transplantation (HCT) for pediatric acute lymphoblastic leukemia (ALL) has been associated with relapse and poor survival. Published studies have had insufficient numbers to: (1) compare the prognostic value of pre-HCT and post-HCT MRD; (2) determine clinical factors post-HCT associated with better outcomes in MRD+ patients; and (3) use MRD and other clinical factors to develop and validate a prognostic model for relapse in pediatric patients with ALL who undergo allogeneic HCT. To address these issues, we assembled an international database including sibling (n = 191), unrelated (n = 259), mismatched (n = 56), and cord blood (n = 110) grafts given after myeloablative conditioning. Although high and very high MRD pre-HCT were significant predictors in univariate analysis, with bivariate analysis using MRD pre-HCT and post-HCT, MRD pre-HCT at any level was less predictive than even low-level MRD post-HCT. Patients with MRD pre-HCT must become MRD low/negative at 1 to 2 months and negative within 3 to 6 months after HCT for successful therapy. Factors associated with improved outcome of patients with detectable MRD post-HCT included acute graft-versus-host disease. We derived a risk score with an MRD cohort from Europe, North America, and Australia using negative predictive characteristics (late disease status, non-total body irradiation regimen, and MRD [high, very high]) defining good, intermediate, and poor risk groups with 2-year cumulative incidences of relapse of 21%, 38%, and 47%, respectively. We validated the score in a second, more contemporaneous cohort and noted 2-year cumulative incidences of relapse of 13%, 26%, and 47% (P < .001) for the defined risk groups.

An Exponential Regression Model Reveals the Continuous Development of B Cell Subpopulations Used as Reference Values in Children.

B lymphocytes are key players in humoral immunity, expressing diverse surface immunoglobulin receptors directed against specific antigenic epitopes. The development and profile of distinct subpopulations have gained awareness in the setting of primary immunodeficiency disorders, primary or secondary autoimmunity and as therapeutic targets of specific antibodies in various diseases. The major B cell subpopulations in peripheral blood include naïve (CD19+ or CD20+IgD+CD27-), non-switched memory (CD19+ or CD20+IgD+CD27+) and switched memory B cells (CD19+ or CD20+IgD-CD27+). Furthermore, less common B cell subpopulations have also been described as having a role in the suppressive capacity of B cells to maintain self-tolerance. Data on reference values for B cell subpopulations are limited and only available for older age groups, neglecting the continuous process of human B cell development in children and adolescents. This study was designed to establish an exponential regression model to produce continuous reference values for main B cell subpopulations to reflect the dynamic maturation of the human immune system in healthy children.

Monitoring of minimal residual disease after allogeneic stem-cell transplantation in relapsed childhood acute lymphoblastic leukemia allows for the identification of impending relapse: results of the ALL-BFM-SCT 2003 trial.

PURPOSE: To elucidate the impact of minimal residual disease (MRD) after allogeneic transplantation, the Acute Lymphoblastic Leukemia Berlin-Frankfurt-Münster Stem Cell Transplantation Group (ALL-BFM-SCT) conducted a prospective clinical trial. PATIENTS AND METHODS: In the ALL-BFM-SCT 2003 trial, MRD was assessed in the bone marrow at days +30, +60, +90, +180, and +365 after transplantation in 113 patients with relapsed disease. Standardized quantification of MRD was performed according to the guidelines of the Euro-MRD Group. RESULTS: All patients showed a 3-year probability of event-free survival (pEFS) of 55%. The cumulative incidence rates of relapse and treatment-related mortality were 32% and 12%, respectively. The pEFS was 60% for patients who received their transplantations in second complete remission, 50% for patients in ≥ third complete remission, and 0% for patients not in remission (P = .015). At all time points, the level of MRD was inversely correlated with event-free survival (EFS; P < .004) and positively correlated with the cumulative incidence of relapse (P < .01). A multivariable Cox model was fitted for each time point, which showed that MRD ≥ 10(-4) leukemic cells was consistently correlated with inferior EFS (P < .003). The accuracy of MRD measurements in predicting relapse was investigated with time-dependent receiver operating curves at days +30, +60, +90, and +180. From day +60 onward, the discriminatory power of MRD detection to predict the probability of relapse after 1, 3, 6, and 9 months was more than 96%, more than 87%, more than 71%, and more than 61%, respectively. CONCLUSION: MRD after transplantation was a reliable marker for predicting impending relapses and could thus serve as the basis for pre-emptive therapy.