title: Altered cell cycle response of drug-resistant lung carcinoma cells to doxorubicin.
abstract: The effect of doxorubicin treatment on cell cycle parameters in asynchronous populations of multidrug-resistant human lung carcinoma cell lines was investigated. A sensitive (DLKP-SQ) and three resistant (DLKP-SQ A250 10p#7, DLKP-A2B and DLKP-A5F) variants of a human lung carcinoma cell line DLKP were exposed to equitoxic concentrations of doxorubicin. The latter three were 8-fold, 30-fold and 300-fold resistant to doxorubicin, respectively. Irreversible G2/M arrest in sensitive (DLKP-SQ) cells was observed 24 h after initiation of doxorubicin treatment. In resistant variants, G2/M arrest occurred at 12-16 h with a subsequent bypass of the G2/M arrest to re-emerge and accumulate in G1. This transient G2/M arrest and subsequent progression into G1 indicated an inefficient checkpoint for monitoring DNA damage induced by doxorubicin treatment. Caffeine treatment could bypass the G2/M block in DLKP-SQ cells. Doxorubicin treatment did not alter cyclin B or cdc2 protein levels, the ability of cdc2 to form complexes with cyclin B or the levels of cyclin B bound to cdc2. The G2/M arrest seen in sensitive cells was associated with an increase in inhibitory phosphorylation of Tyr15 on cdc2. In contrast, tyrosine 15 phosphorylation did not change in resistant variants after drug treatment and a general increase in cdc2 kinase activity was seen. Cdc25C levels were not altered following drug treatment.
authors.affiliation: National Cell and Tissue Culture Centre/National Institute for Cellular Biotechnology, Dublin City University, Glasnevin, 9, Dublin, Ireland.
authors.forename: C
authors.initials: C
authors.lastname: O'Loughlin
authors.forename: M
authors.initials: M
authors.lastname: Heenan
authors.forename: S
authors.initials: S
authors.lastname: Coyle
authors.forename: M
authors.initials: M
authors.lastname: Clynes
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002110:Caffeine / Q000627:therapeutic use; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology*; D004338:Drug Combinations; D019008:Drug Resistance, Neoplasm; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008938:Mitosis / Q000187:drug effects; D014407:Tumor Cells, Cultured; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D018797:Cell Cycle Proteins; D019926:Cyclin B; D004338:Drug Combinations; D002110:Caffeine; D004317:Doxorubicin; D016203:CDC2 Protein Kinase; C517008:CDC25B protein, human; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D004250:DNA Topoisomerases, Type II