Induction of apoptosis in MDA-231 cells by protein synthesis inhibitors is suppressed by multiple agents.
In the present study we investigated the ability of several diverse agents to inhibit MDA-231 cell death induced by two different protein synthesis inhibitors, cycloheximide (CHX) and ricin. Cell death was evaluated by several techniques: trypan blue staining, determination of the released lactic dehydrogenase, transmission electron microscopy, and DNA fragmentation. Results from DNA gel electrophoresis and electron microscopy suggest a mechanism of death by apoptosis which terminates in necrosis. Approximately 60% of cell death was induced either by a continuous exposure to 30 micrograms/ml CHX for 48 hr or by a 1-hr exposure to 250 pg/ml ricin followed by a subsequent incubation of 48 hr in the absence of the drug. Cell survival, in the protein synthesis-inhibited cells, was enhanced by the following diverse agents: the growth factors EGF (20 ng/ml) and IGF-1 (20 ng/ml), the protein kinase C activator 12-0-tetradecanoyl-phorbol-13-acetate (5 ng/ml), the protein kinase A activator 8-bromoadenosine 3':5'-cyclic monophosphate (650 micrograms/ml), the nuclease inhibitor aurintricarboxylic acid (100 micrograms/ml), and fetal bovine serum (5%). The survival agents that stimulated protein synthesis in the control untreated cells had no effect on the CHX-inhibited protein synthesis, which indicates that new protein synthesis is not required for cell survival. The same survival agents attenuated the continuous decrease in protein synthesis in the ricin-exposed cells; therefore, the involvement of new protein synthesis in the survival mechanism could not be excluded. The protein kinase C inhibitor staurosporine blocked, in a dose-dependent manner, the survival effect of 12-0-tetradecanoyl-phorbol-13-acetate and EGF, but not that of aurintricarboxyclic acid or fetal bovine serum, in the protein synthesis-inhibited cells. These results provide evidence for several distinctive pathways, the activation of which inhibits MDA-231 cell death induced by protein synthesis inhibitors. Some of these pathways involved activation of protein kinases, probably protein kinase C.
Geier
A
A
Institute of Endocrinology, Chaim Sheba Medical Center, Tel Hashomer and Department of Life Sciences, Bar-Ilan University, Ramat Gan, Israel.
Bar-Shalom
I
I
Beery
R
R
Haimsohn
M
M
Hemi
R
R
Malik
Z
Z
Lunenfeld
B
B
Karasik
A
A
D000470:Alkaloids / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000473:pathology; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D006801:Humans; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012276:Ricin / Q000494:pharmacology; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000470:Alkaloids; D011500:Protein Synthesis Inhibitors; D004815:Epidermal Growth Factor; D004247:DNA; D012276:Ricin; D003513:Cycloheximide; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate