EP300-ZNF384 transactivates IL3RA to promote the progression of B-cell acute lymphoblastic leukemia

The EP300-ZNF384 fusion gene is an oncogenic driver in B-cell acute lymphoblastic leukemia (B-ALL). In the present study, we demonstrated that EP300-ZNF384 substantially induces the transcription of IL3RA and the expression of IL3Rα (CD123) on B-ALL cell membranes. Interleukin 3 (IL-3) supplementation promotes the proliferation of EP300-ZNF348-positive B-ALL cells by activating STAT5. Conditional knockdown of IL3RA in EP300-ZF384-positive cells inhibited the proliferation in vitro, and induced a significant increase in overall survival of mice, which is attributed to impaired propagation ability of leukemia cells. Mechanistically, the EP300-ZNF384 fusion protein transactivates the promoter activity of IL3RA by binding to an A-rich sequence localized at -222/-234 of IL3RA. Furthermore, forced EP300-ZNF384 expression induces the expression of IL3Rα on cell membranes and the secretion of IL-3 in CD19-positive B precursor cells derived from healthy individuals. Doxorubicin displayed a selective killing of EP300-ZNF384-positive B-ALL cells in vitro and in vivo. Collectively, we identify IL3RA as a direct downstream target of EP300-ZNF384, suggesting CD123 is a potent biomarker for EP300-ZNF384-driven B-ALL. Targeting CD123 may be a novel therapeutic approach to EP300-ZNF384-positive patients, alternative or, more likely, complementary to standard chemotherapy regimen in clinical setting.

MRD-Negative Remission Induced in EP300-ZNF384 Positive B-ALL Patients by Tandem CD19/CD22 CAR T-Cell Therapy Bridging to Allogeneic Stem Cell Transplantation

EP300-ZNF384-positive B cell acute lymphoblastic leukemia (B-ALL) patients are reported to have a unique immunophenotype with high expression of CD19 and CD22, weak expression of CD20 and aberrant expression of CD13 and/or CD33, sensitivity to chemotherapy and a favorable outcome. To date, the cases of only 53 patients have been reported, albeit few reports on salvage therapy when conventional chemotherapies failed. Here, we describe two relapsed and refractory adult B-ALL patients with EP300-ZNF384 who achieved second remission through tandem CD19/CD22 CAR T-cell therapy. Grade 3 and 2 cytokine release syndrome were observed in cases 1 and 2, respectively. No immune effector cell-associated neurotoxicity syndrome was detected. Both patients underwent consolidate haploidentical hematopoietic stem cell transplantation (HSCT), and each maintained measurable residual disease-negative remission for 14 and 13 months, respectively. Our study suggests that CD19/CD22 CAR T-cell therapy bridging to allogeneic HSCT may be a viable option for EP300-ZNF384-positive B-ALL.

Systematic application of fluorescence in situ hybridization and immunophenotype profile for the identification of ZNF384 gene rearrangements in B cell acute lymphoblastic leukemia

INTRODUCTION

ZNF384 gene fusions resulting from translocations with several partner genes have been described in B cell acute lymphoblastic leukemia (B-ALL) with a characteristic immunophenotype (aberrant CD13 and or CD33 with dim CD10). The prognosis of patients with this rearrangement appears to depend on the fusion partner. ZNF384 rearrangements have been identified by high through put technologies such as RNA sequencing in most of the studies published. We tested the feasibility of using the characteristic immunophenotype as a tool to screen for patients with ZNF384 translocations which can be subsequently confirmed by cytogenetic / molecular methodologies.

METHODS

ZNF384 rearrangements in B-ALL patients at diagnosis with CD10 <80% and were negative for the BCR-ABL1 fusion (n = 109) were identified by fluorescence in situ hybridization followed by confirmation by reverse transcriptase-polymerase chain reaction and Sanger sequencing. The end of induction measurable residual disease evaluated by flow cytometry for these patients was obtained from patient records.

RESULTS

ZNF384 translocations were identified in 14 patients and were cytogenetically cryptic in 13. EP300-ZNF384 was the most common fusion partner (n = 12), while TAF15-ZNF384 and TCF3-ZNF384 were identified in 1 patient each. End of induction MRD by flow cytometry was positive in 5 of 8 patients with the EP300-ZNF384 fusion treated at our center.

CONCLUSION

Our findings show a practical approach for the identification of ZNF384 gene rearrangements by widely available technologies and indicate that the response to therapy may be heterogeneous even in this subset, which has been reported as having a favorable prognosis.