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Growth- and differentiation-associated expression of bcl-2 in B-chronic lymphocytic leukemia cells.
- Source :
-
Blood [Blood] 1992 Jun 01; Vol. 79 (11), pp. 2981-9. - Publication Year :
- 1992
-
Abstract
- The bcl-2 gene is translocated into the Ig loci in about 80% of human follicular lymphomas and in 10% of B-type chronic lymphocytic leukemias (B-CLL), resulting in a high level of expression. We have compared the expression of bcl-2 transcripts and protein in B-CLL cells in their normal equivalent CD5+ B cells and in normal B-cell populations representative of different in vivo and in vitro stages of activation and proliferation. We report here that bcl-2 was expressed in 11 of 11 cases of CD5+ B-CLL clones, contrasting with the absent expression in normal CD5+ B cells. Activation of 173 and 183 B-CLL cells by phorbol esters (12-O-tetradecanoylphorbol-13-acetate [TPA]) to IgM secretion without concomitant DNA synthesis resulted in a rapid but transient downregulation of bcl-2 expression. In contrast, the reduction of bcl-2 at both the messenger RNA and protein levels was sustained after mitogenic stimulation, suggesting that bcl-2 expression and proliferation are inversely related in these cells. This notion was further supported by immunocytochemical analysis showing that bcl-2 was primarily expressed in small resting lymphocytes and in cells differentiating to the plasma cell stage, but less expressed in Ki67-positive proliferating B blasts. Moreover, it was also supported by the low level of bcl-2 in exponentially growing Epstein-Barr virus-carrying lymphoblastoid and B-CLL cell lines. The regulation of bcl-2 expression in B-CLL resembled that of normal tonsillar follicular B cells, in which a high level of expression was found in resting mantle zone B cells but not in the proliferating germinal center B cells. Based on these findings and the role of bcl-2 in maintaining B-cell memory, we propose that the phenotype of B-CLL cells corresponds to a mantle zone memory-type B cell.
- Subjects :
- Aged
Antigens, CD analysis
B-Lymphocytes immunology
B-Lymphocytes metabolism
CD5 Antigens
Cell Division
Female
Gene Expression Regulation, Neoplastic
Humans
Immunoglobulin M metabolism
Immunohistochemistry
Leukemia, Lymphocytic, Chronic, B-Cell immunology
Leukemia, Lymphocytic, Chronic, B-Cell pathology
Lymphocyte Activation
Male
Middle Aged
Proto-Oncogene Proteins c-bcl-2
RNA, Messenger metabolism
Tetradecanoylphorbol Acetate pharmacology
Gene Expression
Leukemia, Lymphocytic, Chronic, B-Cell genetics
Proto-Oncogene Proteins genetics
Subjects
Details
- Language :
- English
- ISSN :
- 0006-4971
- Volume :
- 79
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- Blood
- Publication Type :
- Academic Journal
- Accession number :
- 1375120