Establishment of a CPT-11-resistant human ovarian cancer cell line.
A camptothecin analog, ((4s)-4,11-diethyl-4-hydroxy-9-[(4- piperidinopiperidino)carbonyloxy]dione hydrochloride trihydrate), (CPT-11), is a recently developed topoisomerase I (Topo I) inhibitor which attracts the attention of clinicians because of its high antitumor activity. We established a CPT-11-resistant human ovarian cell line, HAC2/CPT, from the parental HAC2 cell line. An in vitro drug sensitivity assay revealed that HAC2/CPT was 9.7 and 4.7 times as resistant as HAC2 to CPT-11 and 7-ethyl-10-hydroxy-CPT-11 (SN-38), an active metabolite of CPT-11, respectively. HAC2/CPT showed no cross-resistance to other drugs tested (adriamycin, etoposide, cisplatin and Taxol), suggesting that HAC2/CPT acquired a phenotype specifically resistant to the Topo I inhibitor. In order to elucidate the mechanism of the resistance, we measured Topo I activity of HAC2 and HAC2/CPT. The activity of Topo I of HAC2/CPT was reduced to half of that of the parental HAC2 cells. To determine the cause of the decreased activity of Topo I, the mutation of the Topo I gene was searched for by the polymerase chain reaction and the reverse transcriptase analysis. Topo I gene mutation was not detected. The amount of Topo I protein was measured by immunoblotting and a marked decrease of Topo I protein was observed in HAC2/CPT. These results suggest that the decreased protein content of Topo I causes the decreased activity of Topo I and the decreased sensitivity of HAC2/CPT to Topo I inhibitors.
Kijima
T
T
Department of Obstetrics and Gynecology, Jikei University School of Medicine, Tokyo, Japan.
Kubota
N
N
Nishio
K
K
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001483:Base Sequence; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004264:DNA Topoisomerases, Type I / Q000032:analysis; D004351:Drug Resistance; D005260:Female; D006801:Humans; D000077146:Irinotecan; D008969:Molecular Sequence Data; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin