Biomedical subjects

J S Stehlin

Publications and source records attributed to J S Stehlin.

At least 19 recordsLinked to original sources

PubMed2000

Dependence of anticancer activity of camptothecins on maintaining their lactone function.

Camptothecins contain a lactone ring that exists in the closed form below ph 7. Above 7, the open (CPT+) and the closed (CPT) form coexist in a 50-50 ratio in mouse plasma and in a 90-10 ratio in human plasma due to the high affinity of human serum albumin (HSA) for CPT+. CPT+ is much less toxic than CPT and it is excreted much faster. In complete RPMI 1640 culture medium, the equilibrium CPT(+)-CPT is 50-50. If 4% HSA is added, it moves to 90-10 modeling for the human physiological situation.

Animals↗

PubMed2000

Structure-activity relationship of alkyl camptothecin esters.

The cytotoxicity of camptothecin (CPT) esters 1-6 was measured. Like parental camptothecin, esters 2 and 3, but not 1, 4, 5, and 6, inhibited proliferation of human leukemia cells in culture and induced programmed cell death as assessed by flow cytometry studies. Exhibition of similar levels of antiproliferative activities of CPT 2 and 3 required different incubation time periods in cell cultures, with CPT and 3 requiring the shortest and longest periods, respectively. Both 2 and 3 were inactive against cells resistant to the semisynthetic CPT derivative 9-nitrocamptothecin and unable to stabilize DNA-topoisomerase I (Topo I) "cleavable complexes" in a cell-free system, suggesting that Topo I activity was required but insufficient for the mechanism of action of 2 and 3. Mouse liver homogenate converted esters to parental CPT, but the conversion rates were different with different esters. Of four tested esters in this experiment, ester 2 had the fastest conversion rate. In vivo studies showed that ester 2 had an exceptional lack of toxicity in nude mice, even at enormous doses, and demonstrated extensive activity against human breast and colon tumors grown as xenografts in immunodeficient nude mice, whereas no antitumor activity was observed for the other esters. In conclusion, ester 2 is a prodrug of the antitumor compound CPT, and it can be administered at very high doses in mice with no appearance of toxicity. This study provides a basis for further evaluation of CPT ester 2 as an investigational anticancer agent.

Animals↗

PubMed1999

A phase II clinical and pharmacological study of oral 9-nitrocamptothecin in patients with refractory epithelial ovarian, tubal or peritoneal cancer.

9-Nitrocamptothecin (9-NC) is a water-insoluble topoisomerase I inhibitor with a broad antitumor activity in animal models. A phase II study was performed in patients with heavily refractory ovarian, tubal or peritoneal cancer (median number of previous chemotherapy regimens > 3) to determine the activity of a daily oral dose of 9-NC. 9-NC dose was 1.5 mg/m2/day for four consecutive days every week. Increments of 0.25 mg/day were authorized in patients without significant side effects. Of 29 evaluable patients, a 7% remission rate was observed. Thirty-four percent of patients had stable disease. The median survival was 8 months. Toxicity was evaluated in 31 patients. Grade 3 or 4 hematologic toxicity consisted of anemia in 10 patients (32%), neutropenia in eight (26%) and thrombocytopenia in three (10%). Grade > or = 2 non-hematologic toxic effects were nausea and vomiting in 26 (84%), diarrhea in 12 (39%), weight loss in seven (22%), chemical cystitis in six (19%) and neutropenic sepsis in six (19%). 9-NC was tolerated for sustained periods of time in some patients (up to 47 weeks). The observed 8-month survival in such a refractory patient population is noteworthy. Further clinical research of prolonged exposure to less toxic analogs of 9-NC is warranted.

Administration, Oral↗

PubMed1999

A study of 9-nitrocamptothecin (RFS-2000) in patients with advanced pancreatic cancer.

This ongoing study evaluates the efficacy of oral 9-nitrocamptothecin (9NC), or RFS-2000, in the treatment of advanced pancreatic cancer. Patients received 9NC orally for 5 days/week; 8 weeks of therapy is required to achieve minimum effective dose. Starting dose was 1.5 mg/m2/day, with adjustments made as necessary. Patients were analyzed for changes in tumor size by CT scan, changes in serum CA 19-9 tumor marker levels, quality of life, and survival. 107 consecutive patients with advanced adenocarcinoma of the pancreas were enrolled before November 3, 1997. Of this group, 47 patients did not receive the minimum 2 courses of treatment necessary to induce response, leaving 60 evaluable patients. Primary dose-limiting toxicities were myelosuppression and interstitial cystitis. No deaths were attributed to 9NC. Median survival was 6.5 months for the 107 total patients and 8.7 months for the 60 evaluable patients, with one patient surviving at 44+ months. Of the 60 evaluable patients, 31.7% were responders (median survival 18.6 months; range 6.5-44.7+ months), 31.7% were stable (median survival 9.7 months), and 36.6% were non-responders (median survival 6.8 months). Fifty-seven previously untreated patients had a median survival of 7.3 months compared to 4.7 months for the 50 previously treated patients. Thirty-three patients who failed gemcitabine therapy prior to 9NC treatment had a median survival of 4.7 months. 9NC is safe and efficacious as first-line therapy for the treatment of advanced pancreatic cancer. It also shows some modest success as second-line therapy in treating gemcitabine failures.

Adult↗

PubMed1998

Alkyl esters of camptothecin and 9-nitrocamptothecin: synthesis, in vitro pharmacokinetics, toxicity, and antitumor activity.

Eleven camptothecin esters, 6a-e and 7a-f, were prepared by straightforward acylation of camptothecins with the corresponding acylating reagents such as organic anhydrides and carboxylic acid chlorides. The in vitro pharmacokinetic determination of lactone levels of esters 6a and 7b showed that the biological life span of their lactone forms in human and mouse plasma significantly increased when compared with their mother compounds, camptothecin (3) and 9-nitrocamptothecin (4). The differences of lactone levels between human plasma and mouse plasma for 6a and 7b were much smaller than what was observed for their mother compounds. The in vivo antitumor activity and toxicity studies demonstrated that some of these esters were very active against human tumor xenografts in nude mice and had an exceptional lack of toxicity in nude mice, even at enormous doses.

Acylation↗

PubMed1998

A phase I clinical and pharmacological study of oral 9-nitrocamptothecin, a novel water-insoluble topoisomerase I inhibitor.

9-Nitrocamptothecin (9NC) is a water-insoluble topoisomerase I inhibitor with a broad antitumor activity in animal models. To determine the maximum tolerated oral dose (MTD), a phase I study was performed in patients with advanced cancer refractory to conventional chemotherapy. 9NC was administered orally with escalating doses to cohorts of five patients beginning at 1 mg/m2/day for five consecutive days every week for 4 weeks. Increments were 0.5 mg/m2/day for each cohort. Toxicity was evaluated in 28 patients diagnosed with various malignancies. Seven patients received 1 mg/m2/day for 28 weeks; 10 patients, 1.5 mg/m2/day for 68 weeks; and 26 patients, 2 mg/m2/day for 159 weeks. At 1.5 mg/m2/day or higher, the dose-limiting toxicity was hematologic, with grade 4 anemia in eight (29%); neutropenia in seven (25%) and thrombocytopenia in five (18%). Grade 2 or higher toxic effects occurred at each dose level: nausea and vomiting in 15 (54%), diarrhea in nine (32%), chemical cystitis in seven (25%), neutropenic sepsis in six (21%) and weight loss in five (18%) (N=28). Responses were observed after 2-8 weeks of therapy in five patients with pancreatic, breast, ovarian and hematologic tumors. Fourteen patients had a disease stabilization and one patient received treatment up to 18 months. The MTD of 9NC given orally has been estimated at 1.5 mg/m2/day for five consecutive days weekly. 9NC may be tolerated for sustained periods of time, but has the potential for significant hematologic, gastrointestinal and urinary bladder toxicity. Significant antitumor activity was observed, warranting further clinical investigations.

Adult↗

PubMed1997

Comparative disposition of the antineoplastic agent 9-nitrocampotothecin and the inactive isomer 12-nitro camptothecin in CASE-bearing nude mice: effect of route of administration on tissue distribution.

PURPOSE: 9-Nitrocamptothecin (9-NC) and 12-nitrocamptothecin (12-NC) are synthetic structural analogues of camptothecin (CPT) which have been prepared to explore the structure/activity relationship of this group of compounds against a wide variety of experimental tumors. As part of our investigation of the pharmacology and the mechanism of tumor inhibition of these compounds, we examined the effect of route of administration on the distribution of tritium-labeled 9-NC and 12-NC, an active and a poor chemotherapeutic agent, respectively. METHODS: Quantitative whole-body autoradiography was used and our results were compared with previous results obtained with the parent compound CPT. RESULTS: These studies revealed that, independent of the route of administration, both CPT derivatives were rapidly distributed to gall bladder, gastrointestinal tract and kidney. The excretion from these organs was indicated by the high levels of radioactivity in urine (urinary bladder) and feces (large intestines). The studies also indicated that the distributions of 9-NC and 12-NC were qualitatively similar, but quantitatively higher uptake of radioactivity was observed in animals treated with 12-NC than in those treated with 9-NC at 30 min following treatment. With the exception of the late sampling time (12 h after administration), the accumulation of radioactivity in the lungs (bronchioles) of animals that received an intravenous (i.v.) dose of 9-NC or 12-NC was higher than those treated with an intramuscular (i.m.) dose. However, the retention of drug-derived radioactivity in the tumors of mice treated with an i.m. dose of 9-NC was higher than that in the tumors of i.v.-treated animals and was also higher than that in tumors of animals treated with 12-NC. CONCLUSIONS: These results suggest that higher accumulation of 9-NC in tumor tissues than of 12-NC may contribute to the more potent chemotherapeutic activity of the former agent. Our results also suggest that i.m. injection is a more effective route of administration than i.v. administration.

Animals↗

PubMed1996

Protocols for the treatment of human tumor xenografts with camptothecins.

Thirty-five human tumors of various histological types xenografted at various sites into nude mice and rats have been used to assess the anticancer activity of camptothecin and derivatives administered by different routes (subcutaneous, intramuscular, intravenous, intrastomach, and transdermal). Camptothecins are active against human tumors at every site including the brain. So far, the best anticancer/toxicity ratio has been found with 9-nitrocamptothecin (9NC) and 9-aminocamptothecin (9AC) to which 9NC converts in the body of mammals. Comparing the results obtained during clinical trials with the animal ones, it is evident that camptothecins are much less active in humans than in mice against human tumors. This is probably due to the fact that in humans the lactone ring of camptotecins opens much faster than in mice. Measurement of the area under the curve (AUC) in mice and humans under comparable conditions of administration gives values of 3% closed lactone for man versus 55% in mice for 9NC. Clearly this is the crucial problem to overcome in order to improve the efficacy of the camptothecins as anticancer agents.

Animals↗

PubMed1996

Phase I clinical and pharmacological studies of 20-(S)-camptothecin and 20-(S)-9-nitrocamptothecin as anticancer agents.

Groups of 52 and 29 patients with refractory cancers received either native camptothecin (CPT) or 9-nitrocamptothecin (9NC), respectively, in Phase I clinical trials designed to determine the maximum tolerated dose, toxicity and potential efficacy of orally administered camptothecins. Favorable responses occurred with both compounds (11% after CPT, 24% after 9NC). Although both agents could be taken safely for extended periods, dose limiting toxicities were substantial. Diarrhea was the major clinical problem with CPT, and myelosuppression with 9NC. Both compounds could cause hemorrhagic cystitis. The antitumor activity demonstrated suggests that further investigation of orally administered camptothecin analogs is warranted.

Adult↗

PubMed1996

Influence of route of administration on [3H]-camptothecin distribution and tumor uptake in CASE-bearing nude mice: whole-body autoradiographic studies.

Camptothecin (CPT) inhibits the growth of a wide variety of experimental tumors. As a part of our exploration of this drug for use as a cancer chemotherapeutic agent, we studied the effect of route of administration on the absorption, distribution and tumor uptake of [3H]-CPT. The rate of disappearance of [3H]-CPT-derived radioactivity from blood during the first 48 h was highest following oral than following intravenous (i.v.) administration. Thereafter blood levels were low irrespective of route of administration. Considerable [3H]-CPT-derived radioactivity was detected in urine and feces up to 48 h after dosing. Distribution studies were conducted using quantitative whole-body autoradiography (WBA). These studies revealed that independent of the route of administration, [3H]-CPT was rapidly excreted in the bile (gallbladder) followed by elimination into the small and large intestinal tract. Levels of CPT-derived radioactivity in the kidneys were minimal and mostly localized in the renal pelvis. Hepatic concentrations of CPT were low and were almost equal to those of the tumor. The lungs of animals treated i.v. showed higher uptake of radioactivity than those treated intramuscularly or orally. Tumor/blood ratios were slightly higher following oral administration than following administration by other routes. This study indicates that CPT is primarily eliminated via the bile. The gastrointestinal tract is the major site of accumulation and excretion of CPT.

Administration, Oral↗

PubMed1995

Growth inhibition of human cancer metastases by camptothecins in newly developed xenograft models.

Several metastatic models have been developed using clonal selection of human malignant cells metastasizing into a specific organ in NIH-I Swiss immunodeficient mice. The organs of choice were the central nervous system (CNS), targeted by metastases of malignant melanoma, and the liver, with metastases of colon adenocarcinoma. Additional models of adrenal metastases by malignant melanoma, and CNS involvement by implanted human lung squamous carcinoma or lymphoblastoid cells, are also available. Organ metastases, as well as the effects of treatment, were confirmed by autopsies and histological examination of the tissues or by a surgical inspection of the liver. The treatment end points were established as the increases in survival times of treated mice relative to placebo-treated controls. Camptothecins injected i.m. or delivered via gastrointestinal tract inhibit the growth of CNS metastases and increase the survival of treated animals. 9-Amino-20(S)-camptothecin was effective in the CNS model and in the model of liver metastases. The drug increased 3.3- and 5.7-fold the survival rates relative to untreated controls with metastases of colon adenocarcinoma to the liver, and all camptothecins were significantly more effective than 5-fluorouracil, currently a drug of choice in treatment of this disease. The xenograft models of metastases are available for studies of drug passage through the blood-brain barrier optimization of drug delivery to the liver, and for the development of new camptothecin-based treatment strategies.

Adenocarcinoma↗

PubMed1992

Complete inhibition of growth followed by death of human malignant melanoma cells in vitro and regression of human melanoma xenografts in immunodeficient mice induced by camptothecins.

The plant alkaloid camptothecin and three camptothecin derivatives were used to study responses of human malignant melanoma (BRO) cells xenografted in immunodeficient (nude) mice. Camptothecin and its derivatives 9-nitro-20(S)-camptothecin and 9-amino-20(S)-camptothecin inhibited growth of tumors and caused regression in all tumor-bearing mice. Tumor regression was accompanied by degenerative changes in the tumor cells, as assessed by microscopic observations of histological sections prepared from the tumors. No toxic effects were observed in the drug-treated mice, with or without xenografts. In parallel experiments, camptothecin, 9-nitro-20(S)-camptothecin, and 9-amino-20(S)-camptothecin inhibited proliferation of BRO cells in vitro and resulted in dramatic morphological cellular changes comparable to those observed in the sections of solid tumors. The derivative 12-nitro-20(S)-camptothecin had no effect on BRO tumors or cell cultures. The difference between 9-nitro-20(S)-camptothecin and 12-nitro-20(S)-camptothecin is the position at which the NO2 group is attached to the camptothecin molecule. In contrast to BRO melanoma cells, none of the camptothecin derivatives had any effect on cultured human melanocytes, the normal counterparts of melanoma cells. Taken together, the findings indicate that camptothecin and derivatives exert different effects on the growth and morphology of normal and malignant (BRO) melanocytes.

Animals↗

PubMed1991

Complete growth inhibition of human cancer xenografts in nude mice by treatment with 20-(S)-camptothecin.

20-(S)-Camptothecin (CAM), a plant alkaloid, was tested against 13 human cancer xenograft lines carried by immunodeficient (nude) mice. The drug, formulated in 20% intralipid and given i.m., was more effective than any other clinically available drug tested. It was found that: (a) CAM, at nontoxic doses, suppressed growth and induced regression of cancer of the colon (3 lines), lung (4 lines), breast (2 lines), stomach (1 line), ovary (1 line), and malignant melanoma (2 lines); (b) the drug was equally effective administered i.m. or p.o. Both routes are significantly better than i.v. administration; (c) CAM is substantially more effective and less toxic than its sodium salt, which was unsuccessfully tested in cancer patients. CAM should be further tested against responsive cancers as a drug which is easy to isolate and formulate for large-scale studies.

Animals↗

PubMed1991

Heterotransplantation of human breast carcinomas in nude mice. Correlation between successful heterotransplants, poor prognosis and amplification of the HER-2/neu oncogene.

Four hundred and thirty-three human breast carcinomas and 23 cell lines derived from human breast carcinomas were heterotransplanted in nude mice. Twenty-eight tumors and 13 cell lines took and could be serially transplanted. Their human origin was established by isozyme analysis performed on successive passages. Sixteen primary infiltrating duct-cell carcinomas (PIDC) took, from a total of 262 transplanted (6.1%). This is in striking contrast to the greater than 50% rate of takes of most major cancers of epithelial origin. All 16 PIDC growing in nude mice were highly cellular and lacked desmoplastic hyperplasia. The clinical prognosis of the PIDC patients whose tumors were successfully transplanted was poor. Ten of 16 (63%) died of their disease within 3 years, compared to only 49 (20%) of the 246 PIDC patients whose tumors did not take in nude mice. This could not be attributed to later stage disease of the tumors that took, because only 15% of these patients had 4 or more positive axillary lymph nodes as opposed to 28% of the patients whose tumors did not take. Sixty-four percent of the breast carcinomas growing in nude mice exhibited amplification of the HER-2/neu oncogene which is also correlated with poor prognosis in human breast cancer. It is possible that the nude mouse is more susceptible to a population of highly invasive and lethal breast carcinomas.

Adult↗

PubMed1989

DNA topoisomerase I--targeted chemotherapy of human colon cancer in xenografts.

Drug development is needed to improve chemotherapy of patients with locally advanced or metastatic colon carcinoma, who otherwise have an unfavorable prognosis. DNA topoisomerase I, a nuclear enzyme important for solving topological problems arising during DNA replication and for other cellular functions, has been identified as a principal target of a plant alkaloid 20(S)-camptothecin. Significantly increased concentrations of this enzyme, compared to that in normal colonic mucosa, were found in advanced stages of human colon adenocarcinoma and in xenografts of colon cancer carried by immunodeficient mice. Several synthetic analogs of camptothecin, selected by tests with the purified enzyme and tissue-culture screens, were evaluated in the xenograft model. Unlike other anticancer drugs tested, 20(RS)-9-amino-camptothecin (9-AC) induced disease-free remissions. The overall drug toxicity was low and allowed for repeated courses of treatment.

Adenocarcinoma↗

PubMed1988

Multiple karyotypic abnormalities, including structural rearrangements of 11p, in cell lines from malignant melanomas.

Cell lines were obtained from three malignant melanoma patients by culturing cell suspensions from tumor biopsies. A total of six lines (I to VI) were established. One line each was established from the first two cases. Lines III and IV were established from two different methyl cellulose colonies derived from the primary tumor of case 3; line III was from a non-pigmented and line IV from a pigmented colony. Cloning of line IV resulted in two highly malignant (IV Cl 1 and IV Cl 3) and one less malignant (IV Cl 2) clone. Clone IV Cl 1 was inoculated intracardially in nude mice and gave rise to adrenal and brain metastases. Lines V and VI were derived from such metastases. Multiple structural and/or numerical chromosome abnormalities were detected in all lines. Line I had 57-61 chromosomes, with structural changes affecting 1p, 2p, 3q, 7p, 7q, 11p, 14q, 17q, and 22q, as well as one unidentified marker. Line II had 40-48 chromosomes, with structural changes of 1p, 1q, 4q, 5p, 6p, 8p, 11p, 11q, 14p, 20p, and two unidentified markers. Line III had 45 chromosomes, 6q+, del(11p), and a centric fusion between chromosomes 14 and 15. Line IV had 45-46 chromosomes. The clonal changes included rearrangements of 1p, 9p, 11p, and the centric fusion of chromosomes 14 and 15. Line V was pseudodiploid and contained aberrations of 1p, 9p, 11p, 14q, 20q, an isochromosome for 21q, and an unidentified marker. Finally, the pseudodiploid line VI had changes of 9p, 11p, centric fusion of chromosomes 14 and 15, and an unidentified marker. Although no single identical aberration was shared by all six lines, structural abnormalities of 11p were invariably present and, hence, might constitute a common cytogenetic feature in melanoma development. The most consistent difference between the amelanotic and melanotic lines derived from case 3 was the presence of a 6q+ marker in the former and a 9p+ marker in the latter.

Chromosome Aberrations↗

PubMed1988

Treatment of cancer of the liver. Twenty years' experience with infusion and resection in 414 patients.

The factors influencing survival for patients with cancer of the liver were studied by reviewing the records of 414 patients operated on in a private oncology practice. Approximately half (47%) had colorectal metastasis; 17% had metastatic breast carcinoma, 14% had malignant hepatoma, 5% had metastatic melanoma, and the remainder had a variety of primary cancers. Eighty-two per cent of all patients had advanced liver disease when first diagnosed. One quarter of the patients had some type of resection; the remainder had abdominal exploration plus insertion of an infusion catheter into the hepatic artery. The postoperative mortality rate after liver resection for 108 patients was 6.5%. After resection, the most important prognostic factor influencing survival was the presence or absence of extrahepatic metastases. When possible, resection was by far the best treatment available, and the best results were seen in patients who had resection of a solitary lesion. For advanced disease, when resection was not possible, intra-arterial chemotherapy, primarily with 5-fluorouracil (5-FU), was associated with response rates of 36% for colorectal cancer, 45% for breast cancer, 13% for hepatocellular cancer, 12% for melanoma, and 14% for metastases from other primary sites. The patients who responded to infusion lived longer than those who did not respond. For example, at 18 months, 26% of the responders with colorectal cancer were alive, as were 50% of the responders with breast cancer and 40% of the responders with hepatocellular cancer. In contrast, at 18 months, there were no survivors among the nonresponders with colorectal, breast, or hepatocellular cancer. For those patients treated solely by infusion chemotherapy, the extent of disease in the liver was the most reliable factor in predicting the length of survival. However, very few patients treated in this manner lived longer than 3 years.

Aged↗

PubMed1987

Improved tumor localization of 111In labeled monoclonal antibody with chelator administration to host nude mice.

Administration of calcium disodium edetate (EDTA) substantially increased the tumor:muscle ratios of nude mice injected with 111In labeled monoclonal antibody 9.2.27. This effect was apparent 3 days to 7 days after antibody injection of mice bearing the BRO human melanoma, but not earlier. The tumor:muscle ratios decreased during this time for animals not receiving chelator. Contemporaneously, EDTA treated mice lost whole body radioactivity more rapidly than did their untreated counterparts, suggesting that 111In which had dissociated from the antibody-DTPA-radiometal complex was chelated and excreted. These results suggest that effective chelator treatment might improve tumor localization of radioactivity after injection of 111In labeled antibodies.

Animals↗