title: Pro-B-cell to pre-B-cell development in B-lineage acute lymphoblastic leukemia expressing the MLL/AF4 fusion protein.
abstract: The most common chromosomal abnormality of infant acute lymphoblastic leukemia (ALL) is the t(4;11)(q21;q23) that gives rise to the MLL/AF4 fusion gene. Leukemic blasts expressing MLL/AF4 are arrested at an early progenitor stage with lymphoid or monocytoid characteristics. A novel B-lineage ALL cell line termed B-lineage-3 (BLIN-3) requiring human bone marrow (BM) stromal cell contact and interleukin-7 (IL-7) for optimal proliferation has been established. BLIN-3 cells have a CD19(+)/CD10(-) phenotype typical of infant ALL, and they harbor the t(4;11)(q21;q23) chromosomal translocation. Reverse transcription-polymerase chain reaction and Western blot analysis confirmed the presence of the MLL/AF4 fusion mRNA and protein in BLIN-3. Initial BLIN-3 cultures had a pro-B cell phenotype and did not express cytoplasmic or surface mu heavy chain. After approximately 5 months in culture on BM stromal cells plus IL-7, BLIN-3 sublines emerged expressing mu heavy chain and VpreB on the cell surfaces (ie, pre-B-cell receptor [BCR](+)). BLIN-3 cells expressing pre-BCR had the t(4;11)(q21;q23) translocation and expressed the MLL/AF4 fusion protein. Cross-linking the BLIN-3 pre-BCR led to enhanced cell proliferation, demonstrating that BLIN-3 expressed a functional pre-BCR. Increased acquisition of surface pre-BCR in BLIN-3 sublines was associated with loss of DJ rearrangements and the appearance of VDJ rearrangements. These results indicate that expression of the MLL/AF4 fusion protein is compatible with BM stromal cell and cytokine dependency, functional immunoglobulin gene segment rearrangement, and subsequent expression of a potentially diverse antigen receptor repertoire. Thus, the expression of MLL/AF4 is compatible with the normal developmental program of human B-lineage cells.
authors.affiliation: University of Minnesota Cancer Center and the Department of Laboratory Medicine and Pathology, Minneapolis 55455, USA. bertr010@tc.umn.edu
authors.forename: F E
authors.initials: FE
authors.lastname: Bertrand
authors.forename: C
authors.initials: C
authors.lastname: Vogtenhuber
authors.forename: N
authors.initials: N
authors.lastname: Shah
authors.forename: T W
authors.initials: TW
authors.lastname: LeBien
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001402:B-Lymphocytes / Q000473:pathology*; D001854:Bone Marrow Cells / Q000502:physiology; D002454:Cell Differentiation; D002455:Cell Division; D002470:Cell Survival; D003432:Cross-Linking Reagents; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000032:analysis; D007223:Infant; D015851:Interleukin-7 / Q000494:pharmacology; D051788:Myeloid-Lymphoid Leukemia Protein; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D016133:Polymerase Chain Reaction; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D003432:Cross-Linking Reagents; D007147:Immunoglobulin Light Chains; D015851:Interleukin-7; C113855:MLL-AF4 fusion protein, human; D015514:Oncogene Proteins, Fusion; D051788:Myeloid-Lymphoid Leukemia Protein