Characterization of two novel pre-B-cell lines (LK63 and LiLa-1): potential models of pre-B-cell differentiation.
In this report we describe two newly isolated pre-B acute lymphoblastic leukaemia cell lines. Both cell lines lack EBV as detected by the EBNA-1 gene probed Southern-blots. Neither cell line expressed the B-cell-specific CD20 antigen on the cell membrane. However surface expression of CD20 was induced by phorbol ester (TPA) on both LiLa-1 and LK63 cell lines. Other pre-B and B-cell lines, such as Reh, Nalm-1, and BALL-1 did not exhibit these changes in phenotype. Previous immunoprecipitation studies have noted that a broad 50-55 kD band co-precipitates with the characteristic 33-37 kD CD20 protein. We demonstrate that, while the 33-37 kD CD20 species was undetectable on resting LiLa-1 and LK63 cells, in each case a 50-55 kD protein was immunoprecipitated by the CD20 antibody. However, the failure to detect any cell surface CD20-associated antigen on the control cells by immunophenotyping indicated that the CD20 epitope of the 50-55 kD molecule was not expressed on the cell surface. Following exposure to TPA the 50-55 kD species was reduced over 48-72 h while the level of the p33-37 CD20 protein was increased. Northern-blot analysis showed that the 50-55 kD protein was not a cryptic form of CD20 as the uninduced cells contained no detectable CD20 mRNA. The decrease of the 50-55 kD protein and the acquisition of the mature CD20 molecule were paralleled by a decline in proliferative activity in both cell lines. As expression of CD20 by normal pre-B cells also coincides with the cessation of cell division and maturation towards a mature B-cell phenotype, these cell lines appear to represent models for a discrete stage of B-cell differentiation which may be valuable in defining the signals regulating pre-B-cell proliferation.
Salvaris
E
E
Lions Clinical Cancer Research Laboratory, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.
Novotny
J R
JR
Welch
K
K
Campbell
L
L
Boyd
A W
AW
D015703:Antigens, CD / Q000378:metabolism; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015152:Blotting, Northern; D015139:Blotting, Southern; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D006801:Humans; D016130:Immunophenotyping; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D013755:Tetradecanoylphorbol Acetate