Effects of cycloheximide on B-chronic lymphocytic leukaemic and normal lymphocytes in vitro: induction of apoptosis

Abstract

Summary A number of reports indicate that protein synthesis is a requirement for the occurrence of apoptosis. In this study, the effect of the protein synthesis inhibitor cycloheximide (CHM) on spontaneous apoptosis of B-chronic lymphocytic leukaemia (B-CLL) cells, previously shown to occur when they are cultured in RPMI-1640 medium with autologous or heterologous serum, was examined. No definite inhibition of apoptosis was observed. Indeed, CHM-treatment augmented apoptosis in the B-CLL cultures and also induced apoptosis of cultured normal peripheral blood lymphocytes. Augmentation was dose-dependent for B-CLL cells over the concentration range 106 M (0.28 yig ml-') to 102 M (2800 yg ml-'), resulting in 9% to 98% apoptosis respectively by 24 h of culture (r = 0.619, P = 0.0008). Normal lymphocytes were affected by CHM over the range 10-4 M to 10-2 M, resulting in 7% to 74% apoptosis respectively (r = 0.794, P = 0.0001). Inhibition of protein synthesis in these cells by CHM was virtually complete at a concentration of 10-3 M. The findings are in accord with some recent reports indicating that suppression of protein synthesis by CHM does not inhibit apoptosis in all circumstances. They also illustrate the marked susceptibility of B-CLL cells, compared with normal lymphocytes, to the induction of apoptosis by this drug. The manner in which CHM triggers apoptosis of some cell types is at present uncertain.

Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells

“…At concentrations > 1 lLM we found it to induce significant (> 50% by 48 h) apoptosis, as has been reported by others (Collins et al, 1991). We found that concentrations less than 1 ,IM for 48 h did not induce apoptosis.…”

Activation of nuclear factor ?B in hepatitis C virus infection: Implications for pathogenesis and hepatocarcinogenesis

“…However, the latter study has added actinomycin D and cycloheximide to the cell culture before the assay of TNF-␣-induced apoptosis. Since both actinomycin D 43,44 and cycloheximide [45][46][47] have been reported to be apoptosisinducing agents, this made their data difficult to interpret. Moreover, the enhancement of TNF-␣-induced apoptosis by HCV core protein is clearly inconsistent with the clinicopathological observations in hepatitis C patients that exacerbations are not often found in the natural history.…”

Degradation of eukaryotic polypeptide chain initiation factor (eIF) 4G in response to induction of apoptosis in human lymphoma cell lines

“…The fact that several disparate inducers of apoptosis, which probably act by di erent mechanisms (Boix et al, 1998), all lead to the loss of eIF4G indicates that the pathways activated by these agents converge on this target protein. Low serum conditions activate apoptosis in immortalized or transformed cell lines (Kulkarni and McCulloch, 1994;Wang and Pandey, 1995;Kawanishi, 1997), probably by depriving the cells of growth factors necessary to promote cell cycle progression (Ohta et al, 1997); cycloheximide is also an e cient inducer of apoptosis in a variety of cell types, perhaps because it blocks the synthesis of one or more proteins essential for the prevention of apoptosis (Martin et al, 1990;Collins et al, 1991;Ledda-Columbano et al, 1992;Ishii et al, 1997); the CD95 (Fas) receptor acts by binding a number of proteins to the`death domain' located on its intracellular portion; etoposide interacts with DNA topoisomerase II and induces DNA strand breaks. The point of convergence of these pathways at the level of eIF4G is most likely the activation of one or more`executioner' caspases (Longthorne and Williams, 1997; Kamada et al, 1997;Cohen, 1997).…”