Thapsigargin-induced persistent intracellular calcium pool depletion and apoptosis in human hepatoma cells.
We found that thapsigargin (Tg), a non-phorbol ester type tumor promoter that specifically inhibits endoplasmic reticulum Ca(2+)-ATPase, transiently increased the level of cytosolic free calcium ([Ca2+]i) and subsequently induced chromatin condensation, nuclear fragmentation, and internucleosomal DNA cleavage in cultured PLC/PRF/5 human hepatoma cells. These alterations were followed by the loss of plasma membrane integrity and by cell death. Epidermal growth factor (EGF) and vasopressin similarly elevated [Ca2+]i without causing DNA fragmentation which is characteristic of apoptosis. Consequently, the elevation of [Ca2+]i itself was not sufficient for causing Tg-induced cell death. On the other hand, preculturing the cells with Tg completely suppressed Ca2+ mobilization induced by EGF and vasopressin; a result that strongly suggests that Tg depleted the endoplasmic reticulum Ca2+ pool. Such depletion is hypothesized to induce apoptotic cell death in this hepatoma cell line by changing the nuclear Ca2+ levels which probably produce a structural change in chromatin.
Kaneko
Y
Y
First Department of Medicine, University of Tokyo, Japan.
Tsukamoto
A
A
D017209:Apoptosis / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000503:physiopathology*; D002455:Cell Division / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000503:physiopathology*; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D013729:Terpenes; D004815:Epidermal Growth Factor; D019284:Thapsigargin; D004250:DNA Topoisomerases, Type II; D002118:Calcium