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Objective:To investigate the molecular genetic and clinical characteristics of MEF2D-BCL9 fusion gene-positive acute B-cell lymphoblastic leukemia (B-ALL), and to provide the reference for the diagnosis and treatment of the disease.Methods:The medical record and experimental examination data of a 18-year-old female MEF2D-BCL9 fusion gene-positive B-ALL patient were retrospectively analyzed. The clinical manifestations and biological characteristics of MEF2D-BCL9 fusion gene-positive B-ALL were summarized.Results:This 18-year-old female patient was treated in a local hospital in December 2018 and was diagnosed as B-ALL. She achieved complete remission after chemotherapy and recurred at 6 months after the initial onset, and then she was admitted to Hebei Yanda Ludaopei Hospital in the 9 months after the initial onset.MEF2D-BCL9 fusion gene was detected through RNA-sequencing (RNA-seq) and verified by using polymerase chain reaction and Sanger sequencing. Bone marrow cell morphology was similar to mature B cells with vacuoles but without characteristic chromosome karyotype abnormalities. The patient achieved remission after VLD regimen chemotherapy, chimeric antigen receptor T-cell (CAR-T) therapy and bridged to allogeneic hematopoietic stem cell transplantation (allo-HSCT). She has maintained complete remission for 2 years at the last follow-up in February 2022.Conclusions:MEF2D-BCL9 fusion gene-positive B-ALL is characterized with high risk, early relapse and poor prognosis. These patients may benefit from CAR-T and allo-HSCT. It further emphasizes the importance of taking MEF2D-BCL9 fusion gene into the detection or identification by using RNA-seq, particularly for those newly diagnosed B-ALL patients in children and adolescents with specific bone marrow morphology.
RESUMO
For many years, immortalized tumor cell lines have been used as reliable tools to understand the function of oncogenes and tumor suppressor genes. Today, we know that tumors can comprise subclones with common and with subclone-specific genetic alterations. We sequenced DNA and RNA of sequential sister cell lines obtained from patients with pre-B acute lymphoblastic leukemia at different phases of the disease. All five pairs of cell lines carry alterations that are typical for this disease: loss of tumor suppressors (CDKN2A, CDKN2B), expression of fusion genes (ETV6-RUNX1, BCR-ABL1, MEF2D-BCL9) or of genes targeted by point mutations (KRAS A146T, NRAS G12C, PAX5 R38H). MEF2D-BCL9 and PAX R38H mutations in cell lines have hitherto been undescribed, suggesting that YCUB-4 (MEF2D-BCL9), PC-53 (PAX R38H) and their sister cell lines will be useful models to elucidate the function of these genes. All aberrations mentioned above occur in both sister cell lines, demonstrating that the sisters derive from a common ancestor. However, we also found mutations that are specific for one sister cell line only, pointing to individual subclones of the primary tumor as originating cells. Our data show that sequential sister cell lines can be used to study the clonal development of tumors and to elucidate the function of common and clone-specific mutations.