PROLACTIN-REGULATED APOPTOSIS OF NB2 LYMPHOMA-CELLS - PIM-1, BCL-2, AND BAX EXPRESSION

Lactogen-dependent Nb2 lymphoma cells, widely employed for studying pr olactin (PRL) mitogenic mechanisms, are also useful for investigations of apoptosis in T-lineage lymphocytes, Utilizing PRL-dependent Nb2-11 cultures, apoptosis-regulatory genes were evaluated for participation in dexamethasone- (DE);) provoked cell death or its inhibition by PRL , Treatment of lactogen-starved, G(1)-arrested Nb2-11 cells with DEX ( 100 nM) activated apoptosis within 12 h evaluated by flow cytometric a nalysis of fragmented DNA, This effect was not associated with altered expression of bcl-2, bax, or pim-1. PRL (10 ng/mL), coincubated with DEX-treated cells, completely blocked DEX-induced apoptosis. This inhi bition was associated with increased expression of bcl-2 anal pim-1 mR NAs, genes reported to suppress apoptosis, within 2-6 h after addition of the hormone. Moreover, the increased transcription of bcl-2 and pi m-1 was coupled to increases in their protein levels. The results sugg est that bcl-2, bax, and pim-1 do not play a critical role in DEX-indu ced apoptosis in Nb2 cells. However, expression of bcl-2, together wit h pim-1, may have a role in mediating the antiapoptotic actions of PRL .