title: Induction of apoptosis in cultured retinoblastoma cells by the protein phosphatase inhibitor, okadaic acid.
abstract: The induction of apoptosis in cultured retinoblastoma cells by diverse drugs was examined by analyzing DNA fragmentation, a hallmark of apoptosis. First, the ability of six retinoblastoma cell lines to undergo apoptosis was surveyed using etoposide (30 micrograms/ml, 20 h exposure). The NCC-RbC-60 cell line, established in this laboratory showed DNA fragmentation clearly, whereas the other cell lines tested, including the representative retinoblastoma cell line, Y-79, did not show distinct DNA fragmentation. Biochemical modulators, such as A23187, forskolin, retinoic acid, phorbol 12-myristate 13-acetate and okadaic acid, were examined to ascertain whether they could induce apoptosis in NCC-RbC-60 and Y-79 cells after exposure for 20 h. Only okadaic acid induced DNA fragmentation in all the retinoblastoma cell lines tested and it induced DNA fragmentation in Y-79 cells in a time- and concentration-dependent manner. Flow-cytometric analysis and microscopic examination revealed that Y-79 cells treated with okadaic acid for 24-48 h accumulated at the G2/M, especially M, phases, before undergoing DNA fragmentation. Other mitotic poisons, nocodazole, colcemid and taxol, also induced apoptosis in Y-79 cells. In the K1034 cell line, established from non-malignant retinal pigmented epithelium, okadaic acid failed to induce both G2/M arrest and DNA fragmentation. These findings suggest that okadaic-acid-induced apoptosis occurs as a result of metaphase arrest.
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D000001:Calcimycin / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002675:Child, Preschool; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005047:Etoposide / Q000008:administration & dosage; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D008297:Male; D008938:Mitosis / Q000187:drug effects; D015739:Nocodazole / Q000494:pharmacology; D019319:Okadaic Acid; D017239:Paclitaxel / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D012175:Retinoblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D005576:Colforsin; D019319:Okadaic Acid; D000001:Calcimycin; D014212:Tretinoin; D005047:Etoposide; D002772:Cholera Toxin; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate; D017239:Paclitaxel; D015739:Nocodazole