Establishment of a CPT-11-resistant human ovarian cancer cell line
Kijima, T.; Kubota, N.; Nishio, K.
Anticancer Research 14(3a): 799-803
1994
ISSN/ISBN: 0250-7005 PMID: 8074481 Document Number: 438607
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 de- creased protein content of Topo I causes the decreased activity of Topo I and the decreased sensitivity of HAC2/CPT to Topo I inhibitors.