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Biomedical subjects

O M Colvin

Publications and source records attributed to O M Colvin.

At least 109 records · Page 6Linked to original sources
PubMed1989

Phase II treatment of medulloblastoma and pineoblastoma with melphalan: clinical therapy based on experimental models of human medulloblastoma.

We conducted a phase II study of intravenous (IV) melphalan in the treatment of children with recurrent medulloblastoma and in the initial treatment of children with poor-prognosis medulloblastoma and pineoblastoma. There was one complete response (CR) and two partial responses (PRs) among the 12 children with recurrent medulloblastoma. There were three PRs in the four patients initially treated with melphalan for poor-prognosis medulloblastoma or pineoblastoma. Toxicity was limited to severe myelosuppression with marked neutropenia and thrombocytopenia. These results support our laboratory studies demonstrating melphalan activity in human medulloblastoma, suggest that similar activity may be demonstrated against pineoblastoma, and support further trials with this agent (administered prior to radiotherapy) in the treatment of patients with newly diagnosed poor-prognosis medulloblastoma.

Adolescent↗
PubMed1989

In vitro chemosensitivity of two Ewing's sarcoma cell lines: implication for autologous bone marrow transplantation.

Intensive chemotherapy requiring rescue with autologous bone marrow may be an encouraging mode of treatment for poor prognosis Ewing's sarcoma (ES). In vitro chemosensitivity test may be useful for establishing an effective purging condition. We studied the in vitro effects of a variety of chemotherapeutic agents on two established ES cell lines (ES-5838 and ES-A4573) and marrow colony-forming unit-granulocyte macrophage (CFU-GM). 4-Hydroperoxycyclophosphamide (4-HC), at 100 microM produced complete inhibition (greater than 5 log) of clonogenic growth of both ES cell lines and spared 6.9% of normal CFU-GM growth. Etoposide (VP-16), at 100 microM produced 3-3.5 log inhibition of ES cell lines and complete inhibition of CFU-GM growth. Adriamycin (ADR) and vincristine (VCR) were more cytotoxic to ES-5838 cells than ES-A4573 cells. ADR at 1 microM produced 99.7% inhibition of ES-5838 cells, 92.2% of ES-A4573 cells, and 86% inhibition of CFU-GM. VCR at 1 microM produced 98.6% inhibition of ES-5838 cells, only 43.7% of ES-A4573 cells, and 75% inhibition of CFU-GM growth. Addition of verapamil did not enhance VCR cytotoxicity of ES cell lines. These studies indicate that 4-HC may be a useful agent for purging metastatic ES cells from the bone marrow for autologous marrow transplantation.

Antineoplastic Agents↗
PubMed1989

Identification of local determinants of DNA interstrand crosslink formation by cyclophosphamide metabolites.

The anti-cancer drug cyclophosphamide produces cytotoxic effects by DNA interstrand crosslink formation. Current knowledge of local physicochemical factors in DNA influencing crosslink formation in DNA has been based on physical models of Watson-Crick DNA. Specific interactions between DNA and cyclophosphamide metabolites determining formation and stabilization of interstrand crosslinks have been identified by advanced molecular computational methods. These results predict that the more favorable DNA sequence for interstrand crosslinking is 5'-GC-3' rather than the previously proposed 5'-CG-3' and that thymine methyl groups adjacent to guanine will inhibit interstrand crosslinking. In addition the conformational and energetic consequences of formamido-pyrimidine adducts and local water interactions with the drug-DNA complex were identified. These simulations of interstrand crosslinking provide a fundamental basis for understanding the mechanism of action of nitrogen mustard-type alkylating agents, and a rationale for the prospective design of more effective anti-tumor agents.

Base Sequence↗
PubMed1989

Efficacy of ex vivo purging for autologous bone marrow transplantation in the treatment of acute nonlymphoblastic leukemia.

We used an in vitro measure of drug activity to predict the efficacy of ex vivo purging of leukemic cells from autologous bone marrow grafts. We previously found that the myeloid progenitor cell (CFU-GM) content of the marrow grafts after ex vivo purging with 4-hydroperoxycyclophosphamide (4-HC) correlates with time to hematologic recovery after autologous bone marrow transplantation in patients with acute nonlymphoblastic leukemia. We observed that variable red blood cell concentration of the bone marrow incubation mixture results in differential cytotoxic activity of 4-HC. The CFU-GM content of the graft after the ex vivo treatment is a measure of this 4-HC activity. We analyzed the disease-free survival of 45 patients with acute nonlymphoblastic leukemia undergoing autologous bone marrow transplantation with 4-HC purged grafts. Patients who relapsed after transplantation had 4.2 +/- 1.1% of graft CFU-GM surviving the ex vivo purge, compared with 1.1 +/- 0.4% for patients who achieved a sustained remission (P = .06). Twenty-three patients with a CFU-GM content after 4-HC purging of greater than 1% of the pretreatment value had an actuarial disease-free survival of 12%, compared to 36% for 22 patients with a less than or equal to 1% CFU-GM content after purging (P = .006). Therefore, percent CFU-GM survival as a measure of 4-HC cytotoxicity identified a group of patients with insufficient purging. Although no randomized clinical trials have documented the need for ex vivo purging, our results suggest that effective bone marrow purging is important for the optimal application of autologous transplantation in the treatment of acute nonlymphoblastic leukemia.

Age Factors↗
PubMed1988

Buthionine sulfoximine-mediated depletion of glutathione in intracranial human glioma-derived xenografts.

D-54 MG, a human glioma-derived continuous cell line growing as subcutaneous or intracranial xenografts in athymic mice, was found to be sensitive to the effects of D,L-buthionine-(SR)-sulfoximine, a selective inhibitor of gamma-glutamylcysteine synthetase. Intraperitoneal administration of one dose of buthionine sulfoximine (BSO, 5 mmol/kg) resulted in depletion of total intracellular glutathione to 57 and 47% of control 12 hr, and 73 and 23% of control 24 hr, after BSO in subcutaneous and intracranial xenografts respectively. Concurrent measurement of total glutathione in the contralateral (non-tumor-containing) cerebral hemisphere in mice bearing intracranial D-54 xenografts demonstrated insignificant depletion of glutathione. Multiple doses of BSO, at 12-hr intervals, resulted in further depletion to 27% (s.c.) and 16.5% (i.c.) of control 12 hr following the final dose of BSO. Quantitative analysis of BSO delivery to xenograft and contralateral brain tissue revealed transfer constants, K1, of 15.8-24.1 x 10(-3) and 2.4 x 10(-3) ml.g-1.min-1 for xenograft and "normal" brain respectively. This highly selective depletion of glutathione in neoplastic tissue versus surrounding non-neoplastic host tissue may have therapeutic implications for the rational use of chemotherapeutic and radiotherapeutic intervention.

Animals↗
PubMed1988

Melphalan transport, glutathione levels, and glutathione-S-transferase activity in human medulloblastoma.

Melphalan transport, glutathione levels, and glutathione-S-transferase activity were measured in two continuous human medulloblastoma cell lines and transplantable xenografts in athymic nude mice, TE-671 and Daoy. In vitro mean glutathione levels were 10.06 nmol/10(6) cells in TE-671 and 2.96 nmol/10(6) cells in Daoy. In vitro mean glutathione-S-transferase values were 91.52 nmol/min/mg protein in TE-671 and 50.31 nmol/min/mg protein in Daoy. Transport studies revealed kinetic parameters of Km = 108.3 microM, Vmax = 363.1 pmol/10(6) cells/min in TE-671 and Km = 111.7 microM, Vmax = 180.6 pmol/10(6) cells/min in Daoy. Melphalan transport was inhibited by both DL-alpha-2-aminobicyclo[2.2.1]heptane-2- carboxylic acid and sodium ion depletion in TE-671 and Daoy cells in vitro, indicating that both systems of amino acid transport are functional in these medulloblastoma lines. In vivo s.c. xenograft glutathione values were lower (7.79 nmol/mg protein) in TE-671 than in Daoy (13.68 nmol/mg protein). The mean plasma concentration in mice given a 10% lethal dose (71.3 mg/m2) of melphalan i.p. was 50.3 microM at 10 min, with the half-life of 29.9 min. At this dose, s.c. xenograft levels were 2- to 3-fold higher in TE-671 than in Daoy tumors for the 3-h period measured. These studies demonstrate transport parameters confirming facilitated transport of melphalan in human medulloblastoma, a mean murine plasma melphalan concentration (following treatment with melphalan) above the in vitro drug dose at which there is a 90% reduction in the number of colonies in comparison to controls for TE-671 and Daoy for 2 h, and glutathione and glutathione-S-transferase levels in the same range previously reported in other melphalan-sensitive and melphalan-resistant human tumors. Future work with spontaneous and acquired melphalan-resistant human medulloblastoma cell lines and xenografts will define the role of these mechanisms in mediating drug resistance.

Animals↗
PubMed1988

Experimental chemotherapy of human medulloblastoma cell lines and transplantable xenografts with bifunctional alkylating agents.

A series of bifunctional alkylators were tested against the genotypically and phenotypically heterogeneous continuous human medulloblastoma cell lines, TE-671, Daoy, and D283 Med in vitro and against TE-671 and Daoy growing as s.c. and intracranial xenografts in athymic mice. Drugs tested included melphalan, cyclophosphamide, iphosphamide, phenylketocyclophosphamide, thiotepa, 1,3-bis(2-chloroethyl)-1-nitrosourea (in vivo), and busulfan (in vivo). Melphalan and phenylketocyclophosphamide were the most active agents in vitro with drug doses at which there is a 90% reduction in the number of colonies in comparison to controls of 2.13, 5.29, and 4.72 microM for melphalan and 4.60, 5.01, and 4.34 microM for phenylketocyclophosphamide against TE-671, D283 Med, and Daoy, respectively. Melphalan, cyclophosphamide, iphosphamide, phenylketocyclophosphamide, and thiotepa produced significant growth delays against s.c. TE-671 and Daoy xenografts, while no activity could be demonstrated for 1,3-bis(2-chloroethyl)-1-nitrosourea or busulfan. Melphalan, cyclophosphamide, iphosphamide, and thiotepa also produced significant increases in median survival in mice bearing intracranial TE-671 and Daoy xenografts. These results extend our previous studies demonstrating the antitumor activity of nitrogen and phosphoramide mustard-based bifunctional alkylating agents in the treatment of human medulloblastoma continuous cell lines and transplantable xenografts, and support the continued use of these agents in clinical trials.

Alkylating Agents↗
PubMed1988

Prediction of the ability to purge tumor from murine bone marrow using clonogenic assays.

The development of potential purging regimens for autologous bone marrow transplantation has been limited by the inability to predict the antitumor activity of these regimens at doses which will allow engraftment. We describe an in vitro model which estimates the in vivo efficacy of potential purging regimens in mice. The log kill of clonogenic L1210 cells after in vitro incubation with graded doses of 4-hydroperoxycyclophosphamide and vincristine (alone or in combination) was linearly related to the incubation dose of drugs. Clonogenic assays could only directly demonstrate about three logs of cell kill. However, the log linear dose-response allowed the extrapolation of cell kill for doses of drugs whose kill could not be determined directly. The extrapolated cell kill accurately predicted the in vitro activity of the drugs as established by determining the survival of B6D2F1 mice given injections of the drug-treated L1210 cells. Lethally irradiated B6D2F1 mice were given injections of mixtures of syngeneic bone marrow and L1210 cells purged with a combination of 4-hydroperoxycyclophosphamide and vincristine. Combining the results of in vitro granulocyte-macrophage colony-forming unit and clonogenic L1210 sensitivities to this drug combination predicted the survival of mice and, therefore, the effectiveness of the purging regimen.

Animals↗
PubMed1988

Enhanced melphalan cytotoxicity following buthionine sulfoximine-mediated glutathione depletion in a human medulloblastoma xenograft in athymic mice.

The effect and therapeutic consequences of buthionine-(SR)-sulfoximine (BSO)-mediated depletion of glutathione in the human medulloblastoma-derived cell line, TE-671, growing as s.c. xenografts in athymic nude mice were examined. The glutathione content of the s.c. xenografts was 1.11 +/- 0.15 mumol/g (7.79 +/- 1.61 nmol/mg of protein). Administration i.p. to tumor-bearing mice of D,L-BSO (two doses at 12-h intervals; 5 mmol/kg) depleted the glutathione content of the xenografts to 25.7% of control. Administration of a 30 mM solution of L-BSO in drinking water for 96 h depleted the glutathione content to 17.4% of control. Depletion of glutathione with these regimens resulted in a significant increase in the s.c. tumor growth delay over that produced by melphalan alone: 17.2 days versus 12.6 days for D,L-BSO (i.p.) plus melphalan versus melphalan and 22.9 days versus 16.6 days for L-BSO (p.o.) plus melphalan versus melphalan. These studies demonstrate the increased cytotoxicity of melphalan resulting from BSO-mediated depletion of glutathione in human medulloblastoma and support further efforts to modulate the chemosensitivity and radiosensitivity of this tumor by modulation of glutathione.

Animals↗
PubMed1988

Cerebrospinal fluid penetration of active metabolites of cyclophosphamide and ifosfamide in rhesus monkeys.

The penetration of the active metabolites of cyclophosphamide (CP) and ifosfamide (IF) into cerebrospinal fluid (CSF) was determined in rhesus monkeys following an i.v. infusion of 1 gm/m2 of CP and IF. Active metabolites were measured using a high-performance liquid chromatography assay with fluorometric detection following derivatization with m-aminophenol. CSF to blood ratios of the active metabolites of CP and IF were found to be 0.17 and 0.13 following systemic dosing of CP and IF, respectively. The levels achieved in the CSF, however, were equivalent to levels known to be cytocidal to malignant cell lines derived from tumors which metastasize to the central nervous system. Only one animal demonstrated neurotoxicity with IF. CSF levels of active metabolite in this animal were similar to those observed in the other animals.

Animals↗
PubMed1988

Ex vivo treatment of myeloma cells by 4-hydroperoxycyclophosphamide and VP-16-213.

To assess the usefulness of 4-hydroperoxycyclophosphamide (4-HC) and VP-16-213 (VP-16) as a purging agent for myeloma cells in bone marrow (BM) ex vivo, myeloma cell lines (SK-RCS-1, RPMI-8226), lymphoma cell line (SK-DHL-2) and normal BM cells were treated at different concentrations of 4-HC or VP-16. Clonogenic tumor cells from all three cell lines could be reduced by more than 4 logs, when treated alone or as a mixture with irradiated normal BM cells at a 4-HC concentration of 60 microM. Under similar conditions, approximately 1% of the normal BM myeloid progenitor granulocyte-macrophage colony-forming cells survived. These observations support the use of 4-HC for purging myeloma cells for autologous BM transplantation.

Bone Marrow↗
PubMed1988

Comparative regimens for the ex vivo chemopurification of B cell lymphoma-contaminated marrow.

The success of autologous bone marrow transplantation for B cell lymphoma may depend on the efficacy of in vitro purification of patients' tumor cell-contaminated marrow. In this study, we tested the toxicity of seven different chemotherapeutic agents against two B cell lymphoma lines (LY-16 and SK-DHL-2) as compared to normal human bone marrow granulocyte-macrophage progenitor cells (CFU-GM). 4-Hydroperoxycyclophosphamide (4-HC), VP-16-213 (VP-16), nitrogen mustard, and vincristine showed a highly selective toxicity against cultured lymphoma cells; i.e., at doses sufficient to induce a 4-log clonogenic tumor cell reduction (4-HC 21 micrograms/ml, VP-16 50 micrograms/ml, nitrogen mustard and vincristine 5 micrograms/ml), 10.0 +/- 6.7, 3.0 +/- 3.2, 23.2 +/- 22.7 and 24.0 +/- 17.0% (mean +/- 1 SD), respectively, of normal bone marrow CFU-GM were preserved. The differential sensitivity of tumor cells and normal hematopoietic precursors was less prominent after exposure of cells to cis-diamminechloroplatinum II (cis-platinum); thus, at a drug dose of 100 micrograms/ml, all detectable lymphoma cells could be eradicated (i.e., greater than or equal to 4 log reduction) while a CFU-GM recovery of only 0.2 +/- 0.2% was observed. In contrast, adriamycin and bleomycin, at the highest tumoricidal concentrations tested (5 and 100 micrograms/ml, respectively) did not exhibit a selective toxicity toward lymphoma cell lines. In summary, our results suggest that nitrogen mustard and vincristine, as well as 4-HC and VP-16, may be useful agents for the ex vivo treatment of bone marrow grafts form B cell lymphoma patients.

Antineoplastic Agents↗
PubMed1987

Intrathecal administration of 4-hydroperoxycyclophosphamide in rhesus monkeys.

The preactivated cyclophosphamide analogue, 4-HC, does not require activation by hepatic microsomal enzymes to express its cytotoxic activity and therefore, unlike cyclophosphamide, may be useful for the regional therapy of cancer. In the present study, the pharmacokinetics and toxicology of 4-HC were studied following intraventricular administration of 0.4 mg to rhesus monkeys with chronic indwelling Ommaya reservoirs. 4-HC was measured in cerebrospinal fluid (CSF) and plasma with a high-performance liquid chromatography assay utilizing a fluorometric detector following derivatization with m-aminophenol. The mean peak level of 4-HC in ventricular CSF was 100 microM 5 min after administration. The drug was cleared rapidly and the elimination was monoexponential with a mean half-life of 22 min. The mean clearance from CSF (0.33 ml/min) was 10-fold higher than CSF bulk flow. The drug was distributed throughout the subarachnoid space with lumbar levels approaching ventricular levels by 60 min. Neither acute nor chronic neurotoxicity or systemic toxicity was observed during the 6-wk observation period. Concentrations of 4-HC demonstrated to be cytocidal in vitro against human breast cancer, lymphoid leukemia, and rhabdomyosarcoma were readily achieved in CSF following intraventricular administration. This study demonstrates that intraventricular therapy with 4-HC is feasible and suggests that further study of this approach in the clinical setting should be considered.

Animals↗
PubMed1987

CFU-GM content of bone marrow graft correlates with time to hematologic reconstitution following autologous bone marrow transplantation with 4-hydroperoxycyclophosphamide-purged bone marrow.

Autologous bone marrow transplants (BMTs) can repopulate the hematologic system of patients treated with marrow-ablative chemotherapy and/or radiotherapy. However, treatment of the bone marrow graft to eliminate residual tumor cells prior to reinfusion can delay the return of peripheral blood elements, presumably from damage to or loss of hematopoietic stem cells responsible for hematologic recovery. To develop a model predictive of hematologic recovery, we studied the progenitor cell contents of 4-hydroperoxycyclophosphamide (100 micrograms/mL)-purged bone marrow grafts of 40 consecutive patients undergoing autologous BMT at this center. Granulocyte-macrophage colonies (CFU-GM) were grown from all grafts after treatment with this chemotherapeutic agent, but erythroid (BFU-E) and mixed (CFU-GEMM) colonies were grown from only 44% and 33% of the grafts respectively. The recovery of CFU-GM after purging ranged from 0.07% to 23%. The logarithm of CFU-GM content of the treated grafts was linearly correlated with the time to recovery of peripheral blood leukocytes (r = -0.80), neutrophils (r = -0.79), reticulocytes (r = -0.60), and platelets (r = -0.66). The CFU-GM content of purged autologous bone marrow grafts may reflect the hematopoietic stem cell content of the grafts and thus predict the rate of hematologic recovery in patients undergoing autologous BMT.

Adolescent↗
PubMed1987

Detection of residual murine LPC-1 myeloma cells from bone marrow cell mixture after purging by 4-hydroperoxycyclophosphamide.

Mixtures of BALB/c bone marrow (5 X 10(6) and LPC-1 myeloma (2 X 10(6) cells have been purged in vitro with 100 microM 4-hydroperoxycyclophosphamide (4HC) for 30 min at 37 degrees C. Elimination of tumor cells was assessed by monitoring newly synthesized tumor-specific IgG 2a kappa in vitro and by reinjecting the cells subcutaneously into the hindlegs of mice. Drug-treated LPC-1 cells had no detectable tumor production and did not reproduce tumors. Untreated cells regrew as solid tumors and killed the host within 3-4 weeks. Bone marrow cell suspensions purged of tumor cells were then used to reconstitute lethally pretreated mice injected 24 h earlier with 300 mg/kg cyclophosphamide (CY). Mice injected with CY alone died within 10 days. Those reconstituted with bone marrow cells or with purged bone marrow-tumor cell mixture lived longer than 7 months. Mice reconstituted with untreated bone marrow-tumor cell suspension grew tumors, had detectable tumor-specific IgG 2a kappa in their serum, and died by day 44. These studies demonstrate that the success of myeloma cell purging can be determined by monitoring newly secreted tumor protein and that 4HC successfully eliminates malignant plasma cells in vitro without impairment of normal bone marrow stem cell functions.

Animals↗
PubMed1987

Progenitor cell assays predict hematopoietic reconstitution after syngeneic transplantation in mice.

Hematopoietic reconstitution following syngeneic bone marrow transplantation with graded doses of untreated and drug-treated bone marrow was studied in B6D2F1 mice. Granulocyte-macrophage colony-forming units (CFU-GM) and spleen colony-forming units (CFU-S) showed similar in vitro drug sensitivities. Both the speed of hematologic recovery and survival of mice transplanted with untreated or drug-treated bone marrow were directly related to the number of CFU-GM or CFU-S transplanted. Similar hematologic recovery was seen for untreated marrow transplants and treated transplants that had similar CFU-GM or CFU-S content. There is a minimum number of transplanted CFU-GM or CFU-S that allows survival of lethally irradiated mice. This number is present in a marrow transplant containing the equivalent of 5 X 10(3) untreated cells or producing one to two spleen colonies. There also exists a maximum value for the number of hematopoietic progenitors in a marrow graft, above which the rate of hematologic recovery following transplantation is rapid and no detectable increase in the rate is seen with increasing CFU-GM or CFU-S content. The presence of this maximum value for transplanted progenitors and variations in culture techniques are probably the reasons previous studies have not always shown a correlation between CFU-GM content and hematologic recovery after bone marrow transplantation.

Animals↗