Characterization of a taxol-resistant human small-cell lung cancer cell line.
Taxol is a novel anticancer agent with activity against a broad range of tumors. It has a unique ability to stabilize polymerized tubulin into microtubule bundles within the cell. We have established a taxol-resistant human small-cell lung cancer cell line (H69/Txl) by exposing H69 cells to stepwise increases in taxol concentration. The resistance of H69/Txl cells to taxol was 4.7-fold that of the original H69 cells: the IC50 values for H69 and H69/Txl were 113.7 +/- 56.54 nM and 538.7 +/- 214.7 nM by the tetrazolium dye assay, respectively. Removal of the drug from the medium resulted in a 38% decrease in the growth rate of H69/Txl as compared with that in the presence of 30 nM taxol, suggesting that the growth of H69/Txl was partially dependent on taxol. H69/Txl showed higher sensitivity to vinca alkaloids such as vindesine, vincristine and vinblastine than the parental H69. There was no significant difference in intracellular [3H]taxol content between H69 and H69/Txl cells. No MDR-1 mRNA was detected in H69/Txl by the reverse transcription polymerase chain reaction. There was no significant difference of total and polymerized tubulin content between H69 and H69/Txl cells. Altered mobility of one of the alpha-tubulin isoforms in H69/Txl was revealed by using isoelectric focusing and Western blotting with anti-alpha-tubulin antibody. In H69, two alpha-tubulin isoforms were observed, whereas three were evident in H69/Txl, two of them comigrating with the isoforms of H69 and the other being more acidic. We observed the increased acetylation of alpha-tubulin in H69/Txl cells as compared with that in H69 cells. The acetylation of alpha-tubulin may be responsible for the taxol resistance and/or taxol-dependent growth of H69/Txl.
Ohta
S
S
Pharmacology Division, National Cancer Center Research Institute, Tokyo.
Nishio
K
K
Kubota
N
N
Ohmori
T
T
Funayama
Y
Y
Ohira
T
T
Nakajima
H
H
Adachi
M
M
Saijo
N
N
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000107:Acetylation; D001483:Base Sequence; D015153:Blotting, Western; D018288:Carcinoma, Small Cell / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002352:Carrier Proteins / Q000096:biosynthesis; D002455:Cell Division / Q000187:drug effects; D004351:Drug Resistance; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D008969:Molecular Sequence Data; D017239:Paclitaxel / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012313:RNA / Q000032:analysis; D014404:Tubulin / Q000378:metabolism; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D014404:Tubulin; D012313:RNA; D017239:Paclitaxel