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Biomedical subjects

G G Chabot

Publications and source records attributed to G G Chabot.

At least 37 records · Page 2Linked to original sources
PubMed1994

Irinotecan (CPT-11) high-dose escalation using intensive high-dose loperamide to control diarrhea.

BACKGROUND: Diarrhea is a serious side effect that may prevent the administration of high doses of the antitumor drug Irinotecan (CPT-11). PURPOSE: Intensive, high-dose loperamide was used in an attempt to control or downstage CPT-11-induced diarrhea and thus permit the use of higher dose intensities of CPT-11. METHODS: Twenty-three patients with various cancers were treated with doses of CPT-11 ranging from 400 to 600 mg/m2, administered as a 30-minute intravenous infusion every 3 weeks. Starting 8 hours or more after the administration of CPT-11, any episode of diarrhea was treated with 2 mg of loperamide taken every 2 hours. Patients stopped taking loperamide only after a 12-hour diarrhea-free period. If diarrhea was not controlled after 3 consecutive days of nonstop loperamide intake, or if the patient was dehydrated, loperamide was stopped and the patient was hospitalized for intravenous fluids. If blood or mucus were found in the stools at any time during diarrhea, loperamide was stopped and the patient was hospitalized. RESULTS: Seventeen of 23 patients had diarrhea while on CPT-11 treatment. Eighty-two CPT-11 cycles were administered to these 17 patients, and diarrhea occurred in 49 of these cycles, at a median time-to-onset of 6 days after CPT-11 administration. The loperamide protocol was followed in 46 of the 49 episodes of diarrhea, with 21 capsules of loperamide the median number being taken (range, 5-72). Only one patient was hospitalized for failure to respond to loperamide, and no major toxicity was associated with loperamide use. Fourteen of the 17 patients who experienced diarrhea were rechallenged with CPT-11 three or more times, and seven patients six or more times. CONCLUSIONS: High-dose loperamide controlled diarrhea in patients receiving CPT-11 and allowed administration of higher doses of CPT-11. IMPLICATIONS: The effectiveness of CPT-11 might be increased by higher dose intensities, which can be made tolerable by control of diarrhea with loperamide.

Adult↗
PubMed1994

Influence of tumor size on the main drug-metabolizing enzyme systems in mouse colon adenocarcinoma Co38.

Mouse colon adenocarcinoma Co38 is widely used as a screening model for human colon tumors. To understand better the influence of tumor size on the main drug-metabolizing enzyme systems, we tested 15 mouse Co38 tumors at different sizes. The average weight was 917 +/- 444 mg (range, 300-1,400 mg). Cytochromes P-450 (1A1/1A2, 2B1/B2, 2C8-10, 2E1, 3A4), epoxide hydrolase (EH), and glutathione-S-transferases (GST-alpha, -mu, and -pi) were assayed by immunoblotting. The activities of the following enzymes or cofactors were determined by spectrophotometric or fluorometric assays: 1-chloro-2,4-dinitrobenzene-GST (CDNB-GST), selenium-independent glutathione peroxidase (GPX), 3,4-dichloronitrobenzene-GST (DCNB-GST), ethacrynic acid-GST (EA-GST), total glutathione (GSH), uridine diphosphate-glucuronosyltransferase (UDP-GT), beta-glucuronidase (beta G), sulfotransferase (ST), and sulfatase (S). Our results showed the absence of all probed P-450s and EH in Co38 tumors. No relationship was found between the Co38 tumor weights and GPX, GST-alpha, and EA-GST (regression analysis). However, a significant correlation was found between the tumor weights and all other enzymes investigated. For certain enzymes or cofactors, a linear decrease (P < 0.05) was observed as a function of tumor weight (CDNB-GST, DCNB-GST, GST-mu, GST-pi, GSH, and beta G). Other enzymatic activities (UDP-GT, S, and ST) were found to decrease in medium-size tumors and to increase in large tumors (P < 0.05; quadratic correlation). These data demonstrate that the expression of many drug-metabolizing enzyme systems is altered during tumor growth and suggest that tumoral response to chemotherapy could be altered as a function of tumor size.

Adenocarcinoma↗
PubMed1994

Principal drug-metabolizing enzyme systems in L1210 leukemia sensitive or resistant to BCNU in vivo.

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) resistance has been mostly studied in vitro. In an attempt to better understand BCNU resistance in the in vivo situation, we compared the principal drug-metabolizing enzyme systems in two L1210 leukemia lines, one sensitive and one resistant to BCNU (L1210/BCNU), passaged in vivo in mice. The following enzymes were assayed by immunoblotting: cytochromes P-450 (1A1/1A2, 2B1/2B2, 2C8-10, 2E1, 3A), epoxide hydrolase (EH) and glutathione S-transferase (GST-alpha, -mu and -pi). The following enzymes and cofactors were assayed fluorometrically or spectrophotometrically: 1-chloro-2-4 dinitrobenzene-GST (CDNB-GST), total glutathione (GSH), UDP-glucuronosyltransferase, beta-glucuronidase, sulfatase and sulfotransferase. Results showed that cytochrome P-450 1A1/1A2 was the only isoenzyme detected in both L1210 and L1210/BCNU. CDNB-GST activity was significantly higher in L1210/BCNU compared with L1210. The isoenzyme GST-alpha was more abundant in L1210/BCNU compared with L1210, whereas GST-pi was expressed less in the BCNU-resistant leukemia line. GST-mu was not detected in either L1210 leukemia lines. GSH levels were similar in the two L1210 lines. No significant difference was observed between the two leukemia lines for the conjugative enzymes UDP-glucuronosyltransferase and sulfotransferase, whereas their corresponding hydrolytic enzymes beta-glucuronidase and sulfatase were about two-fold lower in the BCNU-resistant leukemia line. Epoxide hydrolase was 1.3-fold higher in L1210/BCNU compared with L1210 and this level was about three-fold higher than in mouse liver. In conclusion, these studies showed the presence of cytochrome P-450 1A1/1A2 in the two L1210 leukemia lines studied, and indicated noteworthy differences between the two leukemia lines for many enzyme systems such as GST, beta-glucuronidase, sulfatase and epoxide hydrolase. These data are of importance to better understand the mechanisms of drug resistance to nitrosoureas in vivo.

Animals↗
PubMed1994

Phase I and pharmacological study of intra-arterial hepatic administration of pirarubicin in patients with advanced hepatic metastases.

Intra-arterial hepatic (i.a.h.) administration of the doxorubicin analogue pirarubicin was evaluated in a phase I trial, based on preclinical studies that showed an advantage of pirarubicin over doxorubicin after locoregional hepatic administration. Pirarubicin was given to 9 patients with metastatic liver disease with intrapatient dose escalation. Of the 58 cycles evaluable for tolerance, no hepatobiliary or vascular toxicity was observed. The dose-limiting toxicity was granulocytopenia: the maximum administered doses ranged from 50 to 120 mg/m2, suggesting variable rates of pirarubicin hepatic extraction between patients. Pharmacokinetic data obtained in 7 patients, in which a direct comparison of intravenous (i.v.) and i.a.h. administration was possible, indicated a median i.v./i.a.h. ratio of 7.4 for the maximal plasma concentration, and a median ratio of 4 for the area under the plasma concentrations versus time curves, suggesting a high pirarubicin hepatic extraction. An unexpectedly high response rate was observed: two complete (colorectal carcinoma) and two partial responses. These data demonstrate that i.a.h. pirarubicin not only produced high locoregional concentrations and reduced systemic exposure, but can also achieve responses in metastatic liver disease of colorectal origin.

Agranulocytosis↗
PubMed1994

Phase I/II trial of continuous infusion vinorelbine for advanced breast cancer.

PURPOSE: A phase I/II trial of vinorelbine (VRL) administered by continuous infusion (CIV) was conducted in advanced breast carcinoma (ABC) patients to determine the maximum-tolerated dose (MTD) and to evaluate the toxicity pattern and antitumor activity of this alternative administration schedule to the currently recommended weekly short intravenous (IV) administration. PATIENTS AND METHODS: Between February 1990 and July 1991, 64 consecutive, eligible patients with ABC were treated; 33 had received one or two previous palliative chemotherapy combinations and 31 had not received chemotherapy for metastatic disease. VRL was administered, after an initial IV bolus of 8 mg/m2 on day 1, by a 4-day CIV at five different 24-hour dose levels (DLs) to be repeated every 21 or 28 days: DL1, 5.5 mg/m2; DL2, 7 mg/m2; DL3, 8 mg/m2, DL4, 9 mg/m2; and DL5, 10 mg/m2. RESULTS: The limiting noncumulative toxicity was neutropenia, with the MTD established at 8 mg/m2 bolus plus 10 mg/m2/d for 4 days (total dose per cycle, 48 mg/m2). At DL3 and DL4, we observed mucositis (14% of patients; five percent of cycles > grade 2), alopecia, and asthenia. By contrast, neurotoxicity was minor. The toxicity was otherwise predictable and manageable. Pharmacokinetic data obtained at DL1 and DL3 showed a mean VRL plasma concentration of 967 +/- 331 ng/mL after the initial 8 mg/m2 IV bolus dose, which declined rapidly thereafter to reach mean steady-state levels of 12 ng/mL (n = 5) for the 30-mg/m2 dose and 8 ng/mL (n = 2) for the 40-mg/m2 dose. These levels were maintained over the 96-hour CIV. The mean residence time (MRT) was 29 +/- 7 hours (terminal half-life [t1/2], 23 hours), the total-body clearance (CL) was 24 +/- 11 L/hr/m2, and the volume of distribution at steady-state (Vss) was high at 1,832 +/- 359 L/m2. Two patients achieved a complete response (CR) and 21 a partial response (PR), for an objective response rate of 36% (95% confidence interval [Cl], 23 to 49). The median duration of response was 6 months. The median survival duration was 24 months (range, 3 to 37). A relationship between given dose-intensity and objective response rate was found, with an overall response (OR) rate of 13.3% (two of 15) for 8 to 10 mg/m2/wk, 35.4% (11 of 31) for 10 to 12 mg/m2/wk, and 55.5% (10 of 18) for 12 to 14.5 mg/m2/wk. CONCLUSION: This trial, while confirming VRL activity in ABC, shows the feasability of a CIV administration schedule. A decrease of the administrated total dose per 3- to 4-week cycle to less than the weekly schedule with the same therapeutic activity suggests a better therapeutic index. The data are also suggestive of a dose-response relationship and a dose-intensity/activity correlation.

Adenocarcinoma↗
PubMed1993

Main drug- and carcinogen-metabolizing enzyme systems in human non-small cell lung cancer and peritumoral tissues.

To better understand the importance of drug-metabolizing enzymes in carcinogenesis and anticancer drug sensitivity of human non-small cell lung cancer, we studied the main drug-metabolizing enzyme systems in both lung tumors and their corresponding nontumoral lung tissues in 12 patients. The following enzymes were assayed by Western blot analysis: cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4); epoxide hydrolase; and glutathione S-transferase isoenzymes (GST-alpha, -mu, and -pi). The activity of the following enzymes or cofactor were determined by spectrophotometric or fluorometric assays: glutathione S-transferase (GST); total glutathione; UDP-glucuronosyltransferase; beta-glucuronidase; sulfotransferase; and sulfatase. Results showed the presence of cytochrome P-450 1A1/1A2 in both tumoral and nontumoral tissues. P-450 1A1/1A2 levels were 3-fold lower in tumors compared to corresponding nontumoral tissues (P < 0.05). None of the other probed cytochromes P-450 were detected in either tumoral or nontumoral lung tissues. For the glutathione system, no significant difference between tumoral and nontumoral tissues was observed (GST activity, glutathione content, GST-alpha, -mu, and -pi). A positive linear correlation was observed between GST activity and GST-alpha or GST-pi. No significant difference was observed for the glucuronide and the sulfate pathways and their corresponding hydrolytic enzymes. Epoxide hydrolase was significantly decreased in tumors compared to nontumoral lung tissues (P < 0.05). In conclusion, these results showed differences between non-small cell lung tumors and nontumoral tissues for cytochrome P-450 1A1/1A2 and epoxide hydrolase. These differences between tumors and peritumoral tissues with regard to these drug-metabolizing enzymes could reflect differences occurring after malignant transformation and may play a role in drug sensitivity to anticancer drugs.

Adult↗
PubMed1993

Main drug-metabolizing enzyme systems in human breast tumors and peritumoral tissues.

In an attempt to better understand breast tumors sensitivity or resistance to anticancer drugs, the main drug-metabolizing enzyme systems were evaluated in both breast tumors and their corresponding peritumoral tissues in 12 patients. The following enzymes were assayed by Western blot: cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4); glutathione S-transferases (GST-alpha, -mu, and -pi); and epoxide hydrolase. The activity of the following enzymes or cofactor were determined by spectrophotometric or fluorometric assays: GST; total glutathione; UDP-glucuronosyltransferase; beta-glucuronidase; sulfotransferase; and sulfatase. Results showed the absence of all probed cytochromes P-450 in both tumoral and peritumoral tissues. GST activity was significantly (P < 0.05) higher in tumors (mean +/- SD, 399 +/- 362 nmol/min/mg) than in corresponding peritumoral tissues (86 +/- 67). The GST isoenzymes GST-mu and GST-pi (determined by immunoblotting) were also higher in tumors than in corresponding peritumoral tissues (3- and 5-fold, respectively). Both GST-mu and GST-pi levels were significantly correlated with GST activity. GST-alpha was not detected in either tumoral or peritumoral tissues. Glutathione levels in tumors (22 +/- 23 nmol/mg protein) were not statistically different from peritumoral tissues (11 +/- 12). Epoxide hydrolase was expressed at similar levels in tumors and peritumoral tissues. The glucuronide-forming enzyme UDP-glucuronosyltransferase was 5-fold lower in tumors (0.1 +/- 0.2 nmol/h/mg) than in peritumoral tissues (0.5 +/- 1), whereas the opposite was observed for the hydrolytic enzyme beta-glucuronidase, which was 6-fold higher in tumors (736 +/- 1392 nmol/h/mg) compared to peritumoral tissues (125 +/- 75). No difference was noted between tumoral and peritumoral tissues for sulfotransferase (1 +/- 2 nmol/h/mg), but the corresponding hydrolytic enzyme (sulfatase) was 2-fold higher in tumoral tissues (14 +/- 15 nmol/h/mg) than in peritumoral tissues (6 +/- 2). In conclusion, several differences were observed between human breast tumors and peritumoral tissues for many conjugating enzymes (GST-mu, GST-pi, and UDP-glucuronosyltransferase) and hydrolytic enzymes (sulfatase and beta-glucuronidase). These noteworthy differences between tumoral and peritumoral tissues with regard to their main drug-metabolizing enzymes could play a role in the relative drug sensitivity or insensitivity of human breast cancer tissues to chemotherapeutic agents and could be potential targets for chemotherapeutic interventions.

Adult↗
PubMed1993

Pharmacokinetic and pharmacodynamic advantages of pirarubicin over adriamycin after intraarterial hepatic administration in the rabbit VX2 tumor model.

Intraarterial chemotherapy with Adriamycin (ADM) has shown limited advantages over i.v. administration, with no reduction in systemic toxicities and modest decrease in peripheral plasma levels. In an effort to improve the selectivity of i.a. anthracycline chemotherapy, we compared pirarubicin (4'-O-tetrahydropyranyladriamycin, THP) and ADM in the surgically implanted VX2 rabbit tumor model. Both drugs were administered at the same dose (0.5 mg/kg) either by the intraarterial hepatic route (i.a.h.) or by the i.v. route. Anthracycline plasma and tissue levels were determined by high-performance liquid chromatography with fluorescence detection. ADM peak plasma concentration and area under the curve were not significantly reduced after i.a.h. administration compared to the i.v. route; however, ADM tumor concentration was 1.9-fold higher following i.a.h. administration compared to the i.v. infusion. After THP administration by the i.a.h. route, systemic exposure (area under the curve) was markedly reduced (8-fold) compared to the same dose administered i.v. These findings correlated well with the very low concentration of the drug in heart tissue following i.a.h. infusion. After i.a.h. administration, tumor THP concentrations were 10.5 times higher compared to the i.v. route. The pharmacokinetic advantage of i.a.h. administration of THP also led to a better antitumoral effect, as shown by a significantly lower tumor growth rate [3 +/- 2% (SD)] in the i.a.h.-treated animals compared to the i.v.-treated groups (58 +/- 9%). Administration of ADM by the i.a.h. route was also inferior to i.a.h. THP. Taken together, our results suggest a clear-cut advantage of THP over ADM for i.a.h. locoregional chemotherapy, because of higher local tumor concentrations, greater antitumoral effect, and lower systemic exposure following the i.a.h. administration of THP. This anthracycline analogue could also be of therapeutic advantage in tumors partially resistant to anthracyclines that would become vulnerable to the high local concentrations achieved with i.a.h. administration. Based on these encouraging results, clinical trials using THP administered by the i.a.h. route were initiated.

Animals↗
PubMed1993

Phase I and pharmacokinetic study of brequinar (DUP 785; NSC 368390) in cancer patients.

Brequinar (DUP 785, NSC 368390) is a 4-quinoline carboxylic acid derivative with broad spectrum antitumour activity in experimental models that acts as an antimetabolite by specific inhibition of de novo pyrimidine synthesis. We performed a phase I study of brequinar administered as a 10 min intravenous (i.v.) infusion for 5 consecutive days, every 4 weeks. 67 evaluable patients were entered in this study and a total of 130 courses were administered at doses ranging from 2 to 350 mg/m2. The dose-limiting toxicity was myelosuppression with predominant thrombocytopenia. Myelosuppression was dose-related and non-cumulative, with considerable interpatient variability depending on haematological risk factors. The maximum tolerated dose of brequinar was 210 mg/m2/day in poor risk patients whereas patients with good risk haematological profile tolerated higher doses (up to 350 mg/m2/day). Other non-limiting toxicities included nausea and vomiting, mucositis and skin reactions. Brequinar plasma pharmacokinetic profiles were biphasic with alpha half-life ranging from 0.1 to 0.7 h, and beta half-life ranging from 1.5 to 8.2 h. Increase in brequinar area under the plasma concentration versus time curves (AUC) was nonlinear. Day 5 brequinar pharmacokinetics obtained in 21 patients indicated a significant increase in AUC (47%) and half-life beta (133%) compared to day 1 pharmacokinetics in the same patient. Brequinar plasma AUC and the per cent change in platelet count at nadir were correlated (P < 0.001). Although no objective response was observed in this study, one minor response was noted in cervical lymph nodes of a Hodgkin's disease patient.

Adult↗
PubMed1993

Tumour necrosis factor-alpha plasma levels after flavone acetic acid administration in man and mouse.

Flavone acetic acid (FAA) is a synthetic flavonoid with a remarkable spectrum of anticancer activities in mouse tumours, but with no anticancer activity in humans. The mechanism of action of this drug is complex and involves a tumour vasculature action similar to the effects of tumour necrosis factor (TNF). To assess directly the role of TNF in FAA mechanism of action, this cytokine was assayed in both mouse and human plasma after intravenous administration of the drug. In mouse, a species particularly sensitive to FAA antitumour action, FAA plasma concentrations reached 268 micrograms/ml at 0.5 h and remained high (165 micrograms/ml) at 6 h following the intravenous administration of an anticancer efficacious dose (540 mg/m2). After FAA administration in mouse, TNF activity (L929 mouse cell bioassay) increased to 300 pg/ml TNF-alpha-equivalent at 2 h, reached a maximum concentration of 600 pg/ml at 4 h, and declined thereafter to 220 pg/ml at 6 h. TNF activity in mouse plasma was completely abrogated in the presence of mouse TNF-alpha antibodies. FAA added directly to blank mouse plasma did not show TNF activity. In patients receiving the drug as a 6-h intravenous infusion at doses ranging from 3.6 to 8.1 g/m2, FAA plasma levels ranged from 58 to 449 micrograms/ml at the end of infusion. Human TNF-alpha levels assayed with an immunoradiometric assay were either not detectable or very low (< 25 pg/ml) before FAA administration. At completion of the FAA infusion, TNF-alpha remained near background levels in 20 of the 21 courses. A slight increase in plasma TNF-alpha was observed in 1 patient at the 8.1 g/m2 dose level of FAA, from 13 pg/ml before intravenous infusion, to 70 pg/ml at completion of intravenous infusion. Taken together, these data demonstrate a marked interspecies difference with regard to TNF-alpha secretion after FAA treatment, as this cytokine is produced in mice, whereas it is not significantly secreted in pretreated patients. Although the low TNF-alpha levels achieved in mice probably do not explain all of FAA antitumour activity in that species, the observed interspecies difference in TNF-alpha secretion after FAA administration could partly explain the marked difference in FAA antitumour activity observed between mice and humans.

Animals↗
PubMed1993

Principal xenobiotic-metabolizing enzyme systems in human head and neck squamous cell carcinoma.

To better understand drug and carcinogen metabolism pathways in head and neck squamous cell carcinoma we assayed the principal drug- and carcinogen-metabolizing enzyme systems in both tumors and their corresponding adjacent non-tumoral tissues. Cytochromes P450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4), epoxide hydrolase and glutathione S-transferases (GST-alpha, GST-mu, GST-pi) were assayed by immunoblotting. GST activity, total glutathione, UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase and sulfatase, were determined by spectral assays. Results showed the absence of all probed cytochromes P450 in tumors and non-tumoral tissues, including P450 1A1/1A2 known to be involved in tobacco-related carcinogenesis. No statistical difference was noted between tumors and adjacent non-tumoral tissues for most enzymes studied (GST-alpha, GST-mu, GST-pi, GST activity, UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase and sulfatase). However, total glutathione concentrations were significantly higher (P < 0.05) in tumors (47 +/- 20 nmol/mg protein) than in non-tumoral tissues (19 +/- 9). On the contrary, epoxide hydrolase was significantly less expressed in tumors (18 +/- 9 micrograms/mg protein) compared to corresponding non-tumoral tissues (37 +/- 9). These data provide new information concerning human head and neck cancer biology that could possibly have clinical implications.

Carcinoma, Squamous Cell↗
PubMed1993

Test dose-guided administration of cisplatin in an anephric patient: a case report.

BACKGROUND: Although cisplatin pharmacokinetics is well documented in patients with various degrees of renal dysfunction, no information is available concerning cisplatin administration to anephric patients. Since anephric patients may sometimes need cisplatin therapy, it is therefore of importance to define therapeutic guidelines for cisplatin administration in this patient population. PATIENT AND METHODS: Cisplatin was administered to an anephric patient (bilateral nephrectomy) requiring cisplatin therapy for a metastatic carcinoma of the urothelium. A test dose of 12 mg (7.5 mg/m2) of cisplatin was first administered as a 1 hour infusion in order to determine the patient's pharmacokinetic parameters. Filterable and total platinum levels were determined by flameless atomic absorption spectrophotometry. Haemodialysis was started 30 min before the beginning of the cisplatin infusion and was maintained for 4 h thereafter. RESULTS: Under haemodialysis, filterable and total platinum pharmacokinetics after the test dose were comparable with a patient with normal renal function, i.e. with peak plasma concentrations of 126 ng/ml and 166 ng/ml for the filterable and the total platinum, respectively. The area under the curves (AUC) were 154 ng.h/ml for the filterable and 11486 ng.h/ml for the total platinum. The terminal half-lives of filterable and total platinum were 0.42 h and 101 h, respectively. Based on the test dose platinum pharmacokinetics, a therapeutic dose of 100 mg (63 mg/m2) of cisplatin was administered. Following the therapeutic dose, peak plasma concentrations reached 1,120 ng/ml for the filterable and 1,280 ng/ml for the total platinum. The AUCs were 1,609 and 65,556 ng.h/ml for the filterable and the total platinum, respectively, as expected from the predicted AUCs obtained from the test dose pharmacokinetics. The terminal half-lives of filterable and total platinum were similar to the ones observed after the test dose, i.e. 0.36 h and 86 h, respectively. Although the patient died of rapidly progressive hepatic failure, the feasibility of the test dose-guided cisplatin administration in an anephric patient is demonstrated. CONCLUSION: This approach may be helpful in monitoring cisplatin therapy in similar cases requiring cisplatin administration.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

[Screening of principal enzymes involved in the metabolism of anticancer drugs in human and murine colonic tumors].

Since drug-metabolizing enzymes may influence the toxic response of tissues or organs to drugs, we studied their expression in human and colon tumor tissues, in an attempt to find new targets for chemotherapy and also to explain the intrinsic drug-insensitivity of most colon tumors to anticancer drugs. In the present work, we compared human colorectal tumors and peritumoral tissues to a mouse colorectal tumor (Co38) and normal murine colon with regard to their main drug-metabolizing enzyme systems. We investigated cytochromes P-450 (1A1/1A2, 2B1/B2, 2C, 2E1, 3A) and epoxide hydrolase (EH) by immunoblotting. Total glutathione (GSH) and the activities of the following enzymes: total GST, selenium-independent glutathione peroxidase (GPX), 1,2-dichloro-4-nitrobenzene-GST (DCNB-GST), ethacrynic acid-GST (EA-GST), UDP-glucuronosyltransferase 1 (UDPGT), beta-glucuronidase (beta G), sulfotransferase (ST) and sulfatase (S) were investigated by fluorometric and spectrophotometric assays. Results obtained by immunoblotting showed that mouse colon tumor Co38 did not express any of the probed cytochromes P-450, whereas human tumors showed the presence of cytochrome P-450 3A. EH was not expressed in either mouse colon tumor Co38 or normal mouse colon, whereas it was expressed in human peritumoral and tumoral colon tissues at similar levels. GPX and EA-GST were detected in all tumoral and non tumoral tissues of both species. DCNB-GST was expressed in all murine tissues investigated, but was not found in human tissues. For human peritumoral and tumoral colorectal tissues there was no significant difference between GST isoenzymes levels, whereas mouse colon tumor Co38 had a lower expression of DCNB-GST and EA-GST compared to normal mouse colon. No significant difference was observed between human tumors and peritumoral tissues for total GST, UDPGT1, beta G, ST and S activities. For murine colon tissues, the conjugation pathways (total GST, UDPGT1 and ST) were lower in Co38, whereas the opposite was observed for the hydrolytic enzymes (beta G and S). In conclusion, despite similarities between human and murine colon tumors, mouse colon tumor Co38 appears different from human colon tumors for many drug-metabolizing enzyme systems. These interspecies differences may have implications with regard to drug screening methodologies and preclinical evaluation of candidate anticancer drugs useful in the chemotherapy of human colorectal tumors.

Aged↗
PubMed1992

Comparison of mouse and human colon tumors with regard to phase I and phase II drug-metabolizing enzyme systems.

Since human colorectal tumors are insensitive to most chemotherapeutic agents, there is a need for the discovery of new drugs that would show activity against this disease. In an attempt to better appreciate the relevance of a widely used mouse colon tumor (colon adenocarcinoma Co38) as a screening model for human colorectal tumors, we compared the main phase I and phase II drug-metabolizing enzyme systems in both tumoral and nontumoral colon tissues. The following enzymes were assayed by Western blot: cytochromes P-450 (1A1/A2, 2B1/B2, 2C, 2E1, and 3A), epoxide hydrolase, and glutathione-S-transferases (GST-alpha, -mu, and -pi). The activities of the following enzymes or cofactors were determined by spectrophotometric or fluorometric assays: total cytochrome P-450, 1-chloro-2,4-dinitrobenzene-GST, selenium-independent glutathione peroxidase, 3,4-dichloronitrobenzene-GST, ethacrynic acid-GST, total glutathione, epoxide hydrolase, UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase, and sulfatase. Results obtained by Western blot showed that mouse colon adenocarcinoma Co38 did not express any of the probed cytochromes P-450, whereas human colorectal tumors expressed only low levels of cytochrome P-450 3A. GST-alpha and GST-pi were detected in all tumoral and nontumoral tissues of both species. The neutral GST-mu was expressed in all murine tissues investigated and was found to be polymorphic in human tissues. For human peritumoral and tumoral colorectal tissues there was no significant difference between GST isoenzyme levels, whereas mouse colon adenocarcinoma Co38 had a lower expression of GST-mu and GST-pi, compared to normal mouse colon. Enzymatic activities for glutathione peroxidase, 3,4-dichloronitrobenzene-GST, and ethacrynic acid-GST confirmed the Western blot results for GST-alpha, GST-mu, and GST-pi, respectively. Total GSH levels were similar between murine and human tumors but were 3-fold higher in human tumors than in peritumoral tissues, whereas they were 7-fold lower in mouse colon tumor Co38, compared to normal mouse colon. Epoxide hydrolase was not expressed in either mouse colon adenocarcinoma Co38 or normal mouse colon tissues, whereas it was expressed in human colon peritumoral and tumoral tissues at similar levels. No significant difference was observed between human tumors and peritumoral tissues for UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase, and sulfatase. For murine colon tissues, the conjugation pathways (UDP-glucuronosyltransferase and sulfotransferase) were lower in colon adenocarcinoma Co38, whereas the converse was observed for the corresponding hydrolytic enzymes (beta-glucuronidase and sulfatase).(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1992

Simultaneous determination of the camptothecin analogue CPT-11 and its active metabolite SN-38 by high-performance liquid chromatography: application to plasma pharmacokinetic studies in cancer patients.

CPT-11 (I; 7-ethyl-10-[4-(1-piperidino)-1- piperidino]carbonyloxycamptothecin) is a new anticancer agent currently under clinical development. A sensitive high-performance liquid chromatographic assay suitable for the simultaneous determination of I and its active metabolite SN-38 (II) in human plasma, and their preliminary clinical pharmacokinetics, are described. Plasma samples were processed using a solid-phase (C18) extraction step allowing mean recoveries of I, II and the internal standard camptothecin (III) of 84, 99 and 72%, respectively. The extracts were chromatographed on a C18 reversed-phase column with a mobile phase composed of acetonitrile, phosphate buffer and heptanesulphonic acid, with fluorescence detection. The calibration graphs were linear over a wide range of concentrations (1 ng/ml-10 micrograms/ml), and the lower limit of determination was 1 ng/ml for both I and II. The method showed good precision: the within-day relative standard deviation (R.S.D.) (5-1000 ng/ml) was 13.0% (range 4.9-19.4%) for I and 12.8% (6.7-19.1%) for II; the between-day R.S.D. (5-10,000 ng/ml was 7.9% (5.4-17.5%) for I and 9.7% (3.5-15.1%) for II. Using this assay, plasma pharmacokinetics of both I and II were simultaneously determined in three patients receiving 100 mg/m2 I as a 30-min intravenous infusion. The mean peak plasma concentration of I at the end of the intravenous infusion was 2400 +/- 285 ng/ml (mean +/- standard error of the mean). Plasma decay was triphasic with half-lives alpha, beta and gamma of 5.4 +/- 1.8 min, 2.5 +/- 0.5 h and 20.2 +/- 4.6 h, respectively. The volume of distribution at steady state was 105 +/- 15 l/m2, and the total body clearance was 12.5 +/- 1.9 l/h.m2. The maximum concentrations of the active metabolite II reached 36 +/- 11 ng/ml.

Antineoplastic Agents, Phytogenic↗
PubMed1991

Crisnatol mesylate: phase I dose escalation by extending infusion duration.

Crisnatol mesylate is a rationally designed cytotoxic arylmethylamino-propanediol with broad spectrum cytotoxic activity. A phase I study with an unconventional escalation scheme was developed using a constant drug infusion rate (mg/m2/hr) and prolonging the infusion duration from 6 to 96 hours. Sixty-five patients received crisnatol at doses from 18 mg/m2 in 6 hrs to 3400 mg/m2 in 72 hours. The dose-limiting toxicity in two of five patients at 2700 mg/m2 and two of three patients at 3400 mg/m2 was neurologic and consisted of a syndrome of confusion, agitation, and disorientation. Phlebitis mandated the use of a central line. The mean terminal phase half-life (T1/2 beta) was 3.3 hours with a total body clearance (CL) of 22.8 L/hr/m2 and a volume of distribution (Vdss) of 53 L/m2. The median steady-state peak plasma concentration (Css) at 2700 mg/m2/72 hours was 2.7 micrograms/ml and at 3400 mg/m2/72 hours was 3.8 micrograms/ml. No responses were seen. The maximum tolerated dose (MTD) on this schedule is 2700 mg/m2/72 hours in patients with no liver disease and good performance status.

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