Modulation of CD95 in leukemia and lymphoma cells by retinoids.

Retinoids are highly active for the treatment of acute promyelocytic leukemia, but have effects on many different types of normal and transformed cells. CD95 is a member of the TNF-receptor superfamily and can mediate apoptosis. In this study, we screened a series of 7 myeloid and 12 lymphoid cell lines for the expression of CD95 and for the induction of CD95 by retinoids. A differential response was observed: in 3/7 myeloid cell lines a significant down-regulation of CD95 happened which correlated with the induction of differentiation. A significant induction of CD95 was observed in 4/ 12 lymphoid lines (2 HHV8+ cell lines, one Burkitt line and another lymphoma line). The modulation of CD95 was both time- and dose- dependent (maximum reached after 3-5 days of culture with 10-6 M retinoid). The 3 retinoid compounds studied (all-trans retinoic acid, 9-cis retinoic acid and 13-cis retinoic acid) had comparable activity. Taken together, we describe a new mode of induction of CD95 in lymphoma cells. More work is needed to define the functional consequences of these changes in CD95 surface expression.