Elucidation of the CD38 Metabolic Circuit in Pediatric T-ALL Suggests a Combination Strategy with Daratumumab
Background
T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy characterized by the abnormal proliferation of immature T-cells. Although initial treatment outcomes for pediatric patients have improved, options remain limited and prognosis remains poor for refractory or relapsed cases. In particular, T-ALL exhibits diverse genomic and immunophenotypic profiles, making it difficult to achieve sustained responses with single-target therapies.
CD38, a type II transmembrane glycoprotein, is expressed on the surface of T-ALL cells and is a target of the anti-CD38 antibody daratumumab, used in the treatment of multiple myeloma. Clinical trials are underway to apply CD38-targeted immunotherapy in both initial and relapsed T-ALL. However, whether CD38 functions merely as a surface marker or as a functional regulator of metabolism and signaling in leukemic cells has not been systematically elucidated. The impact of intratumoral CD38 expression variation on treatment response and relapse remains an unresolved challenge.
Key Findings
The research team applied multimodal profiling combining transcriptomic, proteomic, and metabolomic analyses to pediatric T-ALL specimens. Bulk RNA sequencing of 1,335 primary tumors revealed that CD38 expression varies across genomic and immunophenotypic subtypes. In contrast, flow cytometry of 150 primary samples and CITE-sequencing of 40 cases demonstrated broad surface expression of CD38 across multiple subtypes. While expression intensity varied, a significant proportion of patients showed potential as candidates for CD38-targeted therapy.
A transcription factor CRISPR-screen identified RUNX1, RUNX3, and TP53 as candidate regulators that increase CD38 expression. Metabolomic profiling of CD38-perturbed cell lines revealed disruption of the polyamine metabolic pathway, which is involved in cell growth and survival. Based on these findings, the researchers combined CD38 targeting with difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, and observed extended survival in preclinical models compared to monotherapy.
Another key connection was inflammatory and SRC family kinase signaling. Transcriptomic data from primary tumors, cell lines, and patient-derived xenograft (PDX) models consistently showed reduced interleukin-32 (IL32) expression when CD38 was absent or negative, supporting a functional link between CD38 and inflammatory signaling. In most genomic subtypes, CD38 expression was positively correlated with lymphocyte-specific protein tyrosine kinase (LCK). Daratumumab treatment increased LCK phosphorylation in cell lines, and combination therapy with dasatinib, an SRC family kinase inhibitor, improved preclinical survival outcomes compared to monotherapy.
Implications and Prospects
This study reinterprets CD38 not merely as a surface antigen recognized by antibodies, but as a functional hub where metabolic, inflammatory, and kinase signaling pathways intersect. The observation that LCK signaling is activated following daratumumab treatment suggests a potential adaptive survival pathway in leukemic cells in response to CD38 targeting. Blocking this pathway with dasatinib or inhibiting polyamine synthesis with DFMO may enhance the depth and duration of anti-CD38 therapy.
However, the demonstrated efficacy is based on cell line and preclinical model data. Whether the survival benefits of combination therapy are reproducible in pediatric patients must be confirmed through clinical trials. Variability in CD38 expression across subtypes, antigen loss during treatment, and potential damage to normal immune cells are important variables to consider. There is also a possibility of overlapping immunosuppressive and hematologic toxicities between dasatinib and daratumumab, and pharmacokinetic/pharmacodynamic studies are required to determine appropriate dosing and administration sequences for DFMO combination. Future development of a biomarker system that simultaneously measures CD38, LCK phosphorylation, IL32, and polyamine metabolic status could help identify patients suitable for combination therapy.
Outcomes for pediatric patients with refractory or relapsed T-cell acute lymphoblastic leukemia (T-ALL) are poor, underscoring the need for improved therapeutic strategies. CD38, a type II transmembrane glycoprotein, is a promising target in T-ALL, with clinical trials evaluating CD38-targeting immunotherapies in frontline and relapsed settings. However, the biological role of CD38 in T-ALL has not been systematically defined. We interrogated CD38 biology through multimodal profiling of pediatric T-ALL samples. Bulk RNA sequencing of 1,335 primary tumors revealed that CD38 expression varies across genomic and immunophenotypic subtypes in T-ALL. Flow cytometry of 150 primary samples and CITE-sequencing of 40 cases demonstrated broad surface expression of CD38. A transcription factor CRISPR-screen identified RUNX1, RUNX3, and TP53 as candidate positive regulators of CD38. Metabolomic profiling of cell lines further revealed disruption of the polyamine pathway following CD38 perturbation. Supporting this finding, co-targeting CD38 with difluoromethylornithine (DFMO), a polyamine metabolism disruptor, improved survival in preclinical models. Across transcriptomic datasets, including primary tumors, cell lines, and patient-derived xenograft models, IL32 expression consistently decreased following CD38 loss or negativity, supporting an association between CD38 and inflammatory signaling pathways. Additionally, CD38 and LCK expression were positively correlated across majority of genomic subtypes, implicating SRC kinase signaling. Consistent with this, daratumumab in cell lines increased LCK phosphorylation, and combination therapy with dasatinib improved survival compared to monotherapy. Collectively, these findings define previously unrecognized interactions between CD38 and targetable pathways and genes in T-ALL and identify rational combinatorial strategies to enhance CD38-directed therapies and reduce relapse risk.
Clinically, this could lead to a strategy in which CD38 expression in leukemic cells of pediatric patients with relapsed or refractory T-ALL is confirmed, and combination therapies are selected based on LCK activity or polyamine metabolic features. For example, dasatinib could be added to patients showing increased LCK phosphorylation after daratumumab treatment, and DFMO could be combined for tumors with high polyamine dependency.
From an industrial perspective, this opens opportunities for drug repositioning by developing new combinations of drugs with existing clinical experience. However, before actual development, pediatric-appropriate dosing, administration sequence, cumulative toxicity, and recovery of normal T-cells must be evaluated. Parallel development of functional metabolic and signaling biomarkers as companion diagnostics, rather than relying solely on CD38 expression for patient selection, is also necessary.