Reduced expression of DNA topoisomerase II confers resistance to etoposide (VP-16) in small cell lung cancer cell lines established from a refractory tumor of a patient and by in vitro selection.
Cell lines, LC-5 and LC-172, were established from tumors of a small cell lung cancer patient prior to and after combination chemotherapy including etoposide (VP-16), when drug-resistant tumors developed in relapse. A VP-16-resistant cell line, LC-172/VP, was selected from the LC-172 cells in culture in multiple steps with VP-16. LC-172 cells were 3.5-fold resistant to VP-16 in growth inhibition, and 3.3-fold resistant to adriamycin as compared with LC-5 cells. LC-172/VP cells showed large differences in cross-resistance to topoisomerase II-targeting drugs such as VP-16, 200-fold, adriamycin, 10-fold, and MST-16, 4.3-fold; the cells were moderately refractory, 5.5-fold, to vincristine. VP-16 accumulation in the cells was similar in three cell lines. Topoisomerase II unknotting activity was reduced 7- to 10-fold in LC-172/VP and 1.5- to 2-fold in LC-172 cells compared with LC-5 cells, while relaxing activity of topoisomerase I appeared to be unchanged. Topoisomerase II protein was also reduced 5- to 10-fold in LC-172/VP and marginally so in LC-172 cells. Topoisomerase II alpha and II beta were each reduced 10-fold and 2-fold, respectively, in LC-172/VP cells, while they were both slightly decreased (-1.5-fold), respectively, in LC-172 cells compared with LC-5 cells. No apparent alteration in ATP requirement for catalytic activity and in sensitivity to VP-16 was observed for topoisomerase II from the three cell lines. Taken together, these results suggested that resistance to VP-16 in LC-172 and LC-172/VP is associated with a quantitative reduction in expression of topoisomerase II alpha of the parental type.
Andoh
T
T
Laboratory of Biochemistry, Aichi Cancer Center Research Institute, Aichi Cancer Center Hospital, Nagoya, Japan. andoh@sccl.t.soka.ac.jp
Nishizawa
M
M
Hida
T
T
Ariyoshi
Y
Y
Takahashi
T
T
Ueda
R
R
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D018288:Carcinoma, Small Cell / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D004250:DNA Topoisomerases, Type II / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D004790:Enzyme Induction; D005047:Etoposide / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D012641:Selection, Genetic; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014750:Vincristine / Q000494:pharmacology
D009363:Neoplasm Proteins; D010879:Piperazines; D059005:Topoisomerase II Inhibitors; D014750:Vincristine; D005047:Etoposide; D004317:Doxorubicin; D004250:DNA Topoisomerases, Type II; C057773:sobuzoxane