Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.3.1.21 (CPT)
4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although glucuronidation catalyzed by uridine 5'-diphosphoglucuronosyltransferase (UGT) is a major pathway of drug inactivation in humans, glucuronidation in malignant cells has received little attention as a cause of anti-cancer drug resistance. In this study, we tried to elucidate the role of SN-38 glucuronidation in the CPT-11-resistant human lung cancer cell line PC-7/CPT. PC-7/CPT cells possessed an increased activity to glucuronidate SN-38 compared to the parent cells, PC-7. Furthermore, sensitivity of PC-7/CPT cells to SN-38 was improved by inhibiting UGT activity. Western and northern blot analyses demonstrated that this increased activity was due to increased levels of UGT protein and mRNA. These results not only imply that upregulation of UGT activity in PC-7/CPT cells may contribute in part to SN-38 resistance, but also illustrate the important of drug metabolism within malignant cells themselves, as a cause of drug resistance.
...
PMID:The role of glucuronidation in 7-ethyl-10-hydroxycamptothecin resistance in vitro. 947 40

To evaluate the concept that transfer of the human carboxylesterase (CE) gene will overcome the drug resistance of a solid tumor to CPT-11 (irinotecan), we used an adenovirus vector (AdCMV.CE) carrying human CE cDNA to infect CPT-11-resistant A549 human adenocarcinoma cells (A549/CPT) in vitro and in vivo and evaluated cell growth over time. The A549/CPT cells, selected by stepwise and continuous exposure of parental A549 cells to CPT-11 over 10 months, had a 6-fold resistance to CPT-11 and 42% CE activity in comparison with parental A549 cells. AdCMV.CE infection resulted in an increase in functional CE protein in resistant cells in vitro that was sufficient to convert CPT-11 to its active metabolite, SN-38, and effectively suppressed resistant cell growth in vitro in the presence of CPT-11. When AdCMV.CE was directly injected into established s.c. resistant A549-based tumors in nude mice receiving CPT-11, there was a 1.8-fold reduction in tumor size at day 20 compared to that of controls (P < 0.05). These observations suggest that adenovirus-mediated gene transfer of the human CE gene and concomitant administration of CPT-11 may have potential as a strategy for local control of acquired CPT-11 resistance of solid tumors.
...
PMID:Reversal of CPT-11 resistance of lung cancer cells by adenovirus-mediated gene transfer of the human carboxylesterase cDNA. 976 66

TAS-103 is a novel anticancer agent targeting both topoisomerase (Topo) I and Topo II, that stabilizes cleavable complexes of Topo-DNA at the cellular level. In this study, the in vitro antitumor effects of TAS-103 were compared with those of other known Topo I and Topo II inhibitors. TAS-103 inhibited DNA synthesis more strongly than RNA and protein synthesis, and induced an increase of cell population in the S-G2/M phase. The cytotoxicity of TAS-103 was strongest against S-phase cells, but its cell cycle phase specificity was not clear, and depended on drug concentration and exposure time. The cytotoxicity of TAS-103 (IC50: 0.0030-0.23 microM) against various tumor cell lines was much stronger than that of VP-16 and comparable to that of SN-38. The cytotoxicity of TAS-103 seemed to be more related to the amount of protein-DNA complexes than to the accumulation of TAS-103 in the cells. P-Glycoprotein (P-gp)-mediated MDR, CDDP-resistant and 5-FU-resistant cell lines did not show cross-resistance to TAS-103. Although PC-7/CPT cells bearing a Topo I gene mutation showed cross-resistance to TAS-103, the sensitivity of P388/CPT, HT-29/CPT and St-4/CPT cells, showing decreased Topo I expression, was not changed. KB/VM4 and HT-29/Etp cells, showing decreased Topo II expression, were slightly cross-resistant to TAS-103. These results suggest that TAS-103 may act as an inhibitor of both Topo I and Topo II at the cellular level. This property may be responsible for its strong antitumor effect and broad-spectrum, growth-inhibitory effect on drug-resistant cell lines.
...
PMID:In vitro antitumor activity of TAS-103, a novel quinoline derivative that targets topoisomerases I and II. 1039 Oct 99

CPT-11 is a prodrug activated by carboxylesterases to the active metabolite SN-38 which is a potent inhibitor of topoisomerase I. CPT-11 is of clinical interest in the treatment of colorectal cancer. We evaluated the activities of CPT-11 converting carboxylesterase (CPT-CE) and topoisomerase I (topo I) in 53 colorectal tumours, in eight liver metastases and in normal tissue adjacent to the tumours. Both CPT-CE and topo I activities were widely variable in the malignant and the normal tissue of patients with colorectal carcinomas. CPT-CE was only two to threefold lower in primary tumours compared to normal liver, suggesting that a local conversion to SN-38 might occur in tumour cells. CPT-CE was similar in liver and in normal colon tissues. Levels of topo I in tumour ranged from 580 to 84 900 U mg protein(-1) and was above 40 000 U mg protein(-1) in 11 of 53 patients. Similarly, a very high ratio (> 5) between tumour and normal tissues were observed in 12 of 53 patients. An inverse correlation was observed between the topo I activity and the clinical stage of disease. Clinical studies are in progress in our institution to explore a possible relationship between CPT-CE and topo I activities in tumour cells and the response to CPT-11-based chemotherapy in patients with colorectal cancer.
...
PMID:CPT-11 converting carboxylesterase and topoisomerase activities in tumour and normal colon and liver tissues. 1040 39

7-Ethyl-10[4-(1-piperidino)-1-piperidino] carbonyloxy-camptothecin (CPT-11), a DNA topoisomerase I inhibitor, undergoes several metabolic pathways to generate conjugated and unconjugated derivatives that could be excreted from the body. The objective of this study was to determine the oxidative metabolites of CPT-11 recovered in human urine samples and to identify cytochrome P450 (CYP) involved in their formation. In addition to the already known metabolites of CPT-11 [SN-38, SN-38-G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC), and 7-ethyl-10-(4-amino-1-piperidino) carbonyloxycamptothecin (NPC)], we isolated three oxidized metabolites from the urine of two children and two adults given CPT-11. M1 and M2 (molecular weight, 602) were hydroxylated, respectively, on the CPT moiety and on the terminal piperidine ring of CPT-11. M3 had a molecular mass of 602, but its urine concentration in patients was too low to establish its chemical structure by liquid chromatography/mass spectrometry. In vitro incubations with cells expressing CYP2C8, CYP2C9, CYP1A1, CYP1A2, or CYP3A7 did not produce any detectable metabolites. Only CYP3A4 produced both APC and NPC, resulting from the oxidation of the piperidinylpiperidine side chain of CPT-11 along with metabolite M2. The metabolism of CPT-11 by CYP3A5 was markedly different because neither APC or NPC nor M2 was produced, whereas only one new metabolite, M4 (molecular weight, 558), was generated by de-ethylation of the CPT moiety. No previous study has reported the presence of the M4 metabolite. Production of APC, NPC, M2, and M4 was prevented by ketoconazole, a specific CYP3A inhibitor. The parameters of CPT-11 biotransformation into M2 and M4 were examined using cell lines expressing, respectively, with CYP3A4 and CYP3A5, indicating that CPT-11 is preferentially metabolized by CYP3A4. In conclusion, CYP3A plays a major role in the metabolism of CPT-11, with some differences of the metabolic profile exhibited by 3A4 and 3A5.
...
PMID:Metabolism of irinotecan (CPT-11) by CYP3A4 and CYP3A5 in humans. 1081 27

Irinotecan (CPT-11) is a topoisomerase I inhibitor commonly used in the treatment of colorectal tumors. It is a prodrug, converted to an active metabolite, SN-38, by carboxylesterases (CEs). CEs are ubiquitary enzymes that react with numerous substrates. A specific CPT-11 converting enzyme was isolated from rat serum, with different kinetic properties than other CEs. We determined kinetic properties of specific CPT-11 CE activity (CPT-CE) in human normal liver and colon tumors. Km were very similar (3.4 microM in liver and 3.8 microM in colon tumors), but Vmax was higher in liver (2.7 pmol/min/mg protein) than in colon tumor (1.7 pmol/min/mg protein). CPT-CE and total CE (using p-nitro-phenylacetate as substrate) were weakly correlated in colon tumors. The large interpatient variability observed in liver CPT-CE activity could play a potential role in the pharmacokinetic variability observed with irinotecan.
...
PMID:Characterization of CPT-11 converting carboxylesterase activity in colon tumor and normal tissues: comparison with p-nitro-phenylacetate converting carboxylesterase activity. 1100 87

7-ethyl-10-[4-(1-piperidyl)-1-piperidyl] carbonyloxy-camptothecin, a topoisomerase I (topo I) inhibitor, is one of the most active agent against lung cancer, and its radiosensitizing effect has been reported recently. We evaluated a combination in vitro effect of irradiation and 7-ethyl-10-hydroxy-CPT (SN-38), an active metabolite of 7-ethyl-10-[4- (1-piperidyl)-1-piperidyl] carbonyloxy-camptothecin, on a human small cell lung cancer cell line (SBC-3) and its cisplatin-resistant subline (SBC-3/CDDP). Growth-inhibitory effects of irradiation with or without SN-38 were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. A modified isobologram method was used to evaluate the treatment interaction. The combination of irradiation and SN-38 showed a synergistic inhibitory effect on the growth of SBC-3/CDDP despite its cross-resistance to irradiation and SN-38. In contrast, the same combination showed only an additive effect on the growth of parental SBC-3 cells. There was no significant difference in topo I protein expression between these two cell lines. In SBC-3 cells, topo I catalytic activity was suppressed by 4 Gy of irradiation, without a decrease of nuclear topo I protein, whereas the exposure of SBC-3 cells to 1 microM SN-38 subsequent to irradiation showed no remarkable additional effects on both topo I activity and protein content. On the other hand, in SBC-3/CDDP cells, topo I activity was unchanged by irradiation, but the subsequent exposure to SN-38 gave rise to a decrease in topo I activity, which was accompanied by a significant decrease in the topo I protein content (P = 0.02). These observations may indicate that SN-38 induces sequestration of topo I onto DNA in radiation-treated SBC-3/CDDP cells and suggest that the synergistic effect of irradiation and SN-38 in SBC-3/CDDP cells was considered attributable to DNA repair-related enhanced recruitment of topo I onto the damaged DNA.
...
PMID:Synergistic effects of topoisomerase I inhibitor, 7-ethyl-10-hydroxycamptothecin, and irradiation in a cisplatin-resistant human small cell lung cancer cell line. 1180 71

7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (irinotecan, CPT-11) is a camptothecin prodrug that is metabolized by carboxylesterases (CE) to the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), a topoisomerase I inhibitor. CPT-11 has shown encouraging antitumor activity against a broad spectrum of tumor types in early clinical trials, but hematopoietic and gastrointestinal toxicity limit its administration. To increase the therapeutic index of CPT-11 and to develop other prodrug analogues for enzyme/prodrug gene therapy applications, our laboratories propose to develop camptothecin prodrugs that will be activated by specific CEs. Specific analogues might then be predicted to be activated, for example, predominantly by human liver CE(hCE1), by human intestinal CE (hiCE), or in gene therapy approaches using a rabbit liver CE (rCE). This study describes a molecular modeling approach to relate the structure of rCE-activated camptothecin prodrugs with their biological activation. Comparative molecular field analysis, comparative molecular similarity index analysis, and docking studies were used to predict the biological activity of a 4-benzylpiperazine derivative of CPT-11 [7-ethyl-10-[4-(1-benzyl)-1-piperazino]carbonyloxycamptothecin (BP-CPT)] in U373MG glioma cell lines transfected with plasmids encoding rCE or hiCE. BP-CPT has been reported to be activated more efficiently than CPT-11 by a rat serum esterase activity; however, three-dimensional quantitative structure-activity relationship studies predicted that rCE would activate BP-CPT less efficiently than CPT-11. This was confirmed by both growth inhibition experiments and kinetic studies. The method is being used to design camptothecin prodrugs predicted to be activated by specific CEs.
...
PMID:Activation of a camptothecin prodrug by specific carboxylesterases as predicted by quantitative structure-activity relationship and molecular docking studies. 1461 91

We report 27 cases of liver metastases treated with transarterial chemoembolization (TACE) with CPT-11, DSM, and mitomycin C (CPT-DSM therapy). In the 27 patients with liver metastases from colorectal cancer, CPT-DSM therapy was performed 47 times. All of these patients were a contra indication of hepatectomy. We compared a tumor marker before and after the treatment, and measured a serum level of SN-38, which is an active substance of CPT-11 and resolved from CPT-11. Although the level of CPT-11 was wearing off after CPT-DSM therapy, the peak of SN-38 level delayed 1 hour after the infusion. The CEA and CA19-9 levels were decreased to 54.2% and to 45.1% of the level before the treatment, respectively. Nine of the partial response and stable disease patients underwent surgery. The response rate was 59%. A 3-year survival rate was 20%. These results suggest that CPT-DSM therapy is one of the most effective anticancer agents. This TACE can be a feasible therapy for colorectal liver metastases as the first-line therapy.
...
PMID:[Transarterial chemoembolization with irinotecan (CPT-11) and degradable starch microspheres (DSM) in patients with liver metastases from colorectal cancer]. 1821 91

SN-38, an active metabolite of irinotecan (CPT-11), is glucuronidated into SN-38G mainly by UGT1A1, during detoxification. However, significant interindividual pharmacokinetic variability in SN-38 is caused by factors, including inherited predispositions that may affect the function and expression of UGT1A1. Moreover, these individual differences can contribute to the development of clinical conditions, such as severe leucopenia and diarrhea. Similar to SN-38, bilirubin is excreted into bile after being glucuronidated by UGT1A1. Thus, bilirubin is metabolized by a mechanism similar to that of SN-38. This suggests that the bilirubin level may be an indicator of the adverse effects caused by CPT- 11. On the other hand, the ratio between the AUC of SN-38 and the AUC of SN-38G (AUCSN-38/AUCSN-38G) indicates the ability of SN-38 to be glucuronidated, and is known to correlate with leucopenia and diarrhea. However, many blood sampling points are required to calculate these AUCs. Therefore, the daily estimation of the AUCSN-38/AUCSN-38G values of individual patients is not practical at the clinical level. Thus, the objectives of this study were as follows: (1) to establish whether or not the total bilirubin level is a useful indicator in predicting the development of CPT-11 toxicity. (2) to investigate the correlation of SN-38/SN-38G (the ratio of the serum concentrations of SN-38 and SN-38G) with AUCSN-38/AUCSN-38G. Based on the result of this investigation, it will be discussed whether or not SN-38/SN-38G may be used as an alternative to AUCSN-38/AUCSN-38G. This study included 14 patients with small cell lung cancer or non-small-cell lung cancer, in whom serum concentrations of CPT-11, SN-38, and SN-38G were measured by HPLC. The results demonstrated a significant correlation between the total bilirubin levels prior to chemotherapy and the logarithmic values for AUCSN-38/AUCSN-38G (r2=0.852). Among the cases with high values for both the total bilirubin level and the AUCSN-38/AUCSN-38G ratio, none of the patients had grade-3 diarrhea, while many cases tended to have grade-3 to -4 neutropenia. Additionally, the results of regression analysis suggest that SN-38/SN-38G (2 hr) and SN-38/SN-38G (4 hr) might be preferable as a predictive index for AUCSN-38/AUCSN-38G. These findings suggest that the total bilirubin level and SN-38/SN-38G, 2 to 4 hours after administration might be used as indicators to predict CPT-11-induced neutropenia. These indicators are likely to contribute to the pharmacogenetic analysis of UGT1A1 genes, as well as individualized therapy, in future, and further studies on this subject are expected.
...
PMID:[Assessment of total bilirubin or SN-38/SN-38G ratio as a predictor of severe irinotecan toxicity]. 1975 21


<< Previous 1 2 3 Next >>

---