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Establishment of a human small‐cell lung‐cancer subline resistant to okadaic acid
Author(s) -
Takeda Yuichiro,
Nishio Kazuto,
Kubota Naohiro,
Miura Kaoru,
Morikage Toshihiko,
Ohmori Tohru,
Kudoh Shoji,
Niitani Hisanobu,
Saijo Nagahiro
Publication year - 1994
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910580623
Subject(s) - okadaic acid , phosphatase , dephosphorylation , cyclin dependent kinase 1 , endocrinology , medicine , biology , intracellular , cell culture , cell cycle , phosphorylation , biochemistry , cell , genetics
Okadaic acid (OA), a specific protein phosphatase inhibitor, has various biological functions. To elucidate the mechanism of OA resistance, we have established a small‐cell lung‐cancer subline (H69/OA100) resistant to the growth‐inhibitory effect of OA; this was done by using the parental cell line (H69) and increasing the concentration of OA. H69/OA100 was about 8 times more resistant to OA than H69. Intracellular retention of the fluorescent OA derivative in H69/OA100 was the same as that in H69. The catalytic activity of protein phosphatase from H69/OA100 was significantly reduced compared with that from H69. The protein phosphatase from H69/OA100 was 3.6 times more resistant to OA than that from H69. We examined the effect of OA on the activity of the immunoprecipitated protein phosphatase type 1 (PPI) and type 2A (PP2A) from the 2 cell lines. The PPI and PP2A from H69/OA100 showed more resistance to OA than those from H69. We next examined the effect of OA on the cell cycle of H69 and H69/OA100. In H69, G 2 /M block was observed at an OA concentration of 30 ng/ml whereas in H69/OA100, no G 2 /M block was observed at concentrations up to 100 ng/ml OA. We finally evaluated the amount of p34 cdc2 kinase expression and the phosphorylation status of p34 cdc2 . There was no difference in p34 cdc2 expression between H69 and H69/OA100 at several concentrations of OA. However, dephosphorylation of p34 cdc2 was observed at 30 ng/ml OA in H69, but not in H69/OA100 up to 100 ng/ml OA. These data suggest that the resistance to OA and the resistance of the cell‐cycle block to OA in H69/OA100 might be due to alteration of protein phosphatase activity.