Expression of the Murine Proto-Oncogene bcl-2 Is Stage Specific and Cell-Type Specific

Abstract

The proto-oncogene bcl-2 is of particular interest in any consideration of neoplasia of B lymphocytes, because it has been shown to be involved in the t(14,18) (q32,q21) translocations that are found in virtually all of human follicular lymphomas, the most common B cell lymphoma in man (Bakhshi et al. 1985; Cleary and Sklar 1985; Tsujimoto et al. 1985, 1986) and in an acute pre-B lymphocytic leukemia cell line (Tsujimoto et al. 1984). The critical consequences of the interruption of the bcl-2 gene by this translocation appears to be a constitutive expression of bcl-2 transcripts that also contain sequences from the newly juxtaposed immunoglobulin heavy chain joining region (Ig-J_H) (Graninger et al. 1987; Seto et al. 1988). The normal function of the bcl-2 proto-oncogene protein product is unknown, but like many other proto-oncogenes it appears to be involved in control of normal growth and development of human hemopoietic cells. Support for this comes from data that show rapid induction of bcl-2 expression in mitogen-stimulated proliferation of normal human B and T lymphocytes (Graninger et al., 1987; Reed et al., 1987; Seto et al. 1988) and a down regulation of bcl-2 expression accompanying terminal B cell maturation (Graninger et al, 1987).