CYCLOHEXIMIDE-INDUCED APOPTOSIS IN BURKITT-LYMPHOMA (BJA-B) CELLS WITH AND WITHOUT EPSTEIN-BARR-VIRUS INFECTION

Epstein-Barr virus (EBV) has been shown, in many instances, to protect B cells from apoptosis via expression of select EBV proteins and up-r egulation of bcl-2 or its homologues. However, at present little is kn own about the influence of EBV infection against cancer therapy-induce d apoptosis in EBV-associated cancers. Many anti-cancer treatments act via inhibition of protein synthesis and so could influence the report ed protein-dependent mechanisms involved in EBV inhibition of apoptosi s. In the present study, Burkitt lymphoma (BJA-B) cells were treated w ith a potent protein synthesis inhibitor, cycloheximide (CHX). Two var iants of BJA-B cells were used, one with EBV infection (EBV(+)), and o ne free of infection (EBV(-)). Cells were collected 0, 3, 6, 12, 24 an d 48 h after addition of either 1 or 50 mu g/mL of CHX. Control cultur es were untreated. Apoptosis was quantified using established morpholo gical and biochemical characteristics, and protein concentrations asse ssed. CHX treatment of EBV(-) BJA-B cells induced massive levels of ap optosis. Apoptosis was inhibited, but remained significantly higher th an that found in control cultures, in similarly treated EBV(+) cells. The study demonstrates that induction of apoptosis in EBV(-) and EBV() cells is not dependent on new protein synthesis, and may be caused b y removal of a 'cell survival' protein. In addition, the reduction in CHX-induced apoptosis in the EBV(+)cells, when compared with similarly treated EBV(-) cells, is not dependent on new protein synthesis and s o may be indicative of a bcl-2 independent mechanism in this instance. The results have important implications for devising and assessing tr eatment of EBV-associated malignancies.