Cycloheximide‐induced apoptosis in Burkitt lymphoma (BJA‐B) cells with and without Epstein‐Barr virus infection

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Abstract
Epstein-Barr virus (EBV) has been shown, in many instances, to protect B cells from apoptosis via expression of select EBV proteins and up-regulation of bcl-2 or its homologues. However, at present little is known about the influence of EBV infection against cancer therapy-induced apoptosis in EBV-associated cancers. Many anti-cancer treatments act via inhibition of protein synthesis and so could influence the reported protein-dependent mechanisms involved in EBV inhibition of apoptosis. In the present study. Burkitt lymphoma (BJA-B) cells were treated with a potent protein synthesis inhibitor, cycloheximide (CHX). Two variants of BJA-B cells were used, one with EBV infection (EBV(+)), and one free of infection (EBV(-)). Cells were collected 0, 3, 6, 12, 24 and 48 h after addition of either 1 or 50 g/mL of CHX. Control cultures were untreated. Apoptosis was quantified using established morphological and biochemical characteristics, and protein concentrations assessed. CHX treatment of EBV(-) BJA-B cells induced massive levels of apoptosis. Apoptosis was inhibited, but remained significantly higher than 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 by 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 so may be indicative of a bcl-2 independent mechanism in this instance. The results have important implications for devising and assessing treatment of EBV-associated malignancies.