Multiple myeloma secondary to acute lymphoblastic leukemia: A case report

Transcription factor 12-mediated self-feedback regulatory mechanism is required in DUX4 fusion leukaemia

BACKGROUND

IGH::DUX4 is frequently observed in 4% B-cell acute lymphoblastic leukaemia patients. Regarding the IGH::DUX4-driven transactivation and alternative splicing, which are the main reasons behind this acute leukaemia outbreak, it remains unclear how transcriptional cofactors contribute to this oncogenic process. Further investigation is required to elucidate their specific role in leukaemogenesis.

METHODS

In order to investigate the cofactors of IGH::DUX4, integrated mining of Chromatin immunoprecipitation (ChIP)-sequencing and RNA-sequencing of leukaemia cells and patient samples were conducted. Furthermore, to elucidate the synergistic interaction between transcription factor 12 (TCF12) and IGH::DUX4, knockdown and knockout experiment, mammalian two-hybridisation assay, co-immunoprecipitation and in situ proximity ligation assays were carried out. Additionally, to further investigate the direct interaction between TCF12 and IGH::DUX4, AI-based structural simulations were utilised. Finally, to validate the synergistic role of TCF12 in promoting IGH::DUX4 leukaemia, cell proliferation, apoptosis and drug sensitivity experiments were performed.

RESULTS

In this study, we observed that the IGH::DUX4 target gene TCF12 might be an important cofactor/helper for this oncogenic driver. The co-expression of IGH::DUX4 and TCF12 resulted in enhanced DUX4-driven transactivation. Supportively, knockdown and knockout of TCF12 significantly reduced expression of IGH::DUX4-driven target genes in leukaemia REH (a precursor B-cell leukaemia cell line) and NALM-6 cells (a precursor B-cell leukaemia cell line). Consistently, in TCF12 knockout cells, the expression of structure-based TCF12 mutant, but not wild-type TCF12, failed to restore the TCF12-IGH::DUX4 crosstalk and the synergistic transactivation. More importantly, the breakdown in TCF12-IGH::DUX4 cooperation impaired IGH::DUX4-driven leukaemia cell survival, caused sensitivity to the chemotherapy.

CONCLUSIONS

Altogether, these results helped to define a previously unrecognised TCF12-mediated positive self-feedback regulatory mechanism in IGH::DUX4 leukaemia, which holds the potential to function as a pivotal drug target for the management of this particular form of leukaemia.

HIGHLIGHTS

Transcription factor 12 (TCF12) is a new novel cofactor in IGH::DUX4 transcriptional complexes/machinery. TCF12 mediates a positive self-feedback regulatory mechanism in IGH::DUX4-driven oncogenic transaction. IGH::DUX4-TCF12 structure/cooperation might represent a potent target/direction in future drug design against B-cell acute lymphoblastic leukaemia.

Synchronous plasma cell neoplasm and B lymphoblastic leukemia/lymphoma at initial presentation: first report of an unusual association with a good outcome

A synchronous diagnosis of a plasma cell neoplasm (PCN) and a non-plasma cell hematologic malignancy is very rare. We report what we believe is the first instance of a synchronous PCN and B lymphoblastic leukemia/lymphoma (B-ALL) diagnosed at initial presentation. The patient underwent laboratory evaluation for an underlying plasma cell neoplasm, including immunology studies, bone marrow biopsy, and flow cytometry immunophenotyping. Serum lambda free light chain and serum IgG were elevated, with an IgG lambda M-protein identified by serum protein electrophoresis and immunofixation. The clinical working diagnosis was plasma cell myeloma. Bone marrow biopsy was positive for a composite PCN and B-ALL. The patient received treatment with VDT-PACE chemotherapy followed by autologous stem cell transplant and maintenance therapy with bortezomib/daratumumab and is in complete remission for both diseases 3.5 years after diagnosis. This case not only adds to the known repertoire of hematologic neoplasms that can occur in association to a PCN, but also demonstrates that patients presenting with this rare combination of hematopoietic neoplasms can be effectively treated simultaneously with excellent responses. Additional research is warranted to understand the pathophysiology, to identify potential prognostic factors, and to develop specific therapeutic plans for these patients.