Transient stabilization of p53 in non-small cell lung carcinoma cultures arrested for growth by retinoic acid.
Proliferation of five non-small cell lung carcinoma (NSCLC) cultures was inhibited after 16 h exposure to retinoic acid. We investigated whether expression of the p53 protein correlated with the growth pattern of NSCLC lines observed in the presence of retinoic acid Levels of wild-type p53 protein underwent fivefold increases in lines H460a and H226b after 16 to 48 h treatment with 5 microM retinoic acid but then decreased to undetectable amounts in these cell lines after 72 h retinoic acid treatment. Levels of p53 transcripts remained unchanged during the time of increases in protein expression in retinoic acid-treated H460a cells, suggesting that a post-translational mechanism was involved in the increased expression of the protein. Pulse-chase analysis demonstrated that wild-type p53 was significantly more stabile in H460a cells treated with retinoic acid, exhibiting a half-life greater than 6 h, in contrast to 3 h for the protein in untreated control cells. The retinoic acid-mediated effect was specific for wild-type p53, since expression of mutant p53 in the H596b and H322j cell lines remained relatively unchanged even after 72 h exposure to retinoic acid. We conclude that retinoic acid induces stabilization of wild-type p53 in NSCLC cells by a post-translational mechanism. Furthermore, increases in expression of p53 were not responsible for the retinoic acid-induced transient inhibition of growth of NSCLC cells, since the growth of H358 p53-null cells also was inhibited by retinoic acid.
Maxwell
S A
SA
Department of Thoracic and Cardiovascular Surgery, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Mukhopadhyay
T
T
D000911:Antibodies, Monoclonal / Q000276:immunology; D000912:Antibodies, Neoplasm / Q000276:immunology; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism*; D009154:Mutation; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D016159:Tumor Suppressor Protein p53; D014212:Tretinoin