Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CPT-11, a recently developed topoisomerase I (Topo I) inhibitor, attracts the attention not only of basic researchers but also of clinicians because of its high antitumor activity. The CPT-11 resistant human lung cancer cell line, PC-7/CPT, showed 10-fold resistance compared to parental cell line, PC-7. The total activity of Topo I in the resistant cell line was one fourth that of the parental sensitive cell line. The Topo I from the resistant cells was also 5-fold more resistant to the inhibitory effect of CPT-11 than that of the parental cells. We speculated that the alteration of the Topo I gene may be responsible for the change in topoisomerase activity of the CPT-11 resistant cell line. Therefore, we analyzed the mutation of Topo I gene using the method of single strand conformation polymorphism of polymerase chain reaction and the reverse transcriptase. We divided Topo I cDNA into ten fragments which overlapped each other and covered whole coding sequences of the Topo I cDNA. We observed mobility shift of two fragments in the PC-7/CPT, suggesting the presence of some mutations in these fragments. We performed the direct-sequencing of these portions by the dideoxy chain termination method and observed an altered sequence having a G to A base change in PC-7/CPT. This base substitution results in replacement of the conserved threonine at 729 position with alanine. These results suggest that the point mutation of Topo I gene is related to the decreases of Topo I activity and the sensitivity to Topo I inhibitor in PC-7/CPT cells.
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PMID:Detection of topoisomerase I gene point mutation in CPT-11 resistant lung cancer cell line. 133 3

Etoposide (VP-16) is one of the most important anticancer agents available and is used in many chemotherapeutic regimens. To characterize resistance to this drug, we established a VP-16-resistant human ovarian cancer cell line, SKOV3/VP, by continuous stepwise exposure of SKOV3 cells to VP-16. The degree of resistance to VP-16 of SKOV3/VP was about 25 times that of the parent cell line (SKOV3), and SKOV3/VP showed cross-resistance to teniposide, adriamycin, CPT-11, and vincristine. The accumulation of [3H]-VP-16 observed in SKOV3/VP cells was about half that seen in SKOV3 cells, and the accumulation of Adriamycin by this resistant cell line was also lower than that of its parent. Overexpression of neither the multidrug resistance gene mdr-1, the multidrug-resistance-associated protein (mrp) gene, nor P-glycoprotein was detected using reverse transcriptase-polymerase chain reaction analysis and flow cytometry with MRK-16, a monoclonal antibody against P-glycoprotein. The topoisomerase II activity of nuclear extracts from SKOV3/VP cells was lower than that from the parental cells, as was the amount of DNA topoisomerase II, demonstrated by immunoblotting. These results suggest that the mechanism responsible for the multidrug resistance of this cell line may be attributable to changes on its DNA topoisomerase II and to its reduced accumulation of the drugs as compared with the parental line SKOV3.
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PMID:Characterization of an etoposide-resistant human ovarian cancer cell line. 791 42

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.
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PMID:Establishment of a CPT-11-resistant human ovarian cancer cell line. 807 81

We recently reported that p.o. administration of the new synthetic bacterial lipopeptide JBT-3002 can protect mice from irinotecan (CPT-11)-induced intestinal injury, but the mechanism was not known. Because interleukin-15 (IL-15) is associated with maintenance of intestinal epithelial cell integrity, we examined whether p.o. administration of JBT-3002 elevates expression of this monocyte-derived cytokine. Four daily i.p. injections of 100 mg/kg CPT-11 were effective against liver metastases produced by CT-26 murine colon cancer cells, but severe damage to the intestinal epithelium and early death of the mice also resulted. Three consecutive daily p.o. doses of JBT-3002 prior to i.p. injection of irinotecan prevented the undesirable side effects of irinotecan without reducing its ability to eradicate liver metastases. Immunohistochemical analyses of the intestines of mice treated with JBT-3002 and CPT-11 demonstrated an increase in the number of dividing cells in the crypts and enhanced expression of IL-15 in lamina propria cells; the increase correlated with increased expression of the IL-15 gene as determined by semiquantitative reverse transcriptase-PCR. In vitro studies demonstrated that JBT-3002 induced expression of IL-15 in peritoneal macrophages but not in normal intestinal epithelial cells (IEC-6). Moreover, the presence of IL-15 decreased irinotecan-mediated cytotoxicity of IEC-6 epithelial cells. These data show that the p.o. administration of JBT-3002 induces expression of IL-15 by macrophages in the lamina propria, which can prevent irinotecan-induced injury to the intestinal mucosa.
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PMID:Oral administration of the immunomodulator JBT-3002 induces endogenous interleukin 15 in intestinal macrophages for protection against irinotecan-mediated destruction of intestinal epithelium. 1047 99