Development of an amphotropic, high-titer retrovirus vector expressing the dihydrofolate reductase gene and conferring methotrexate resistance.

Altered mouse dihydrofolate reductase gene (DHFRR) was expressed in murine cells using Abelson murine leukemia provirus genome as a prototype vector. A cDNA clone of DHFRR was inserted into a plasmid structure containing retroviral transcriptional as well as packaging signals. The recombinant plasmid was transfected into psi-2 ecotropic cells and the transient virus was used to infect amphotropic PA-12 cells.

Endogenous thymidine and hypoxanthine are a source of error in evaluating methotrexate cytotoxicity by clonogenic assays using undialyzed fetal bovine serum.

None of 13 fresh human tumor samples of various histology cloned in a two-layer agar culture system with 20% undialyzed fetal bovine serum (FBS) showed sensitivity to three antifolates, methotrexate (MTX), trimetrexate and 5,8-dideazaisofolic acid (IAHQ), even after continuous exposure to the highest concentrations (100 microM) for 21 days. In order to investigate this lack of antifolate drug effect, we compared the toxicity of continuous MTX exposure in the human colon carcinoma cell line HCT-8, cloned in a thymidineless medium (RPMI 1640) supplemented with 10% horse serum (HS), 10% fetal bovine serum (FBS), 20% FBS or 20% dialyzed FBS. In the presence of native FBS, when the minimum clone size was set at 30 cells/colony, the survival of HCT-8 cells reached a plateau at approximately 60% of untreated control after exposure to MTX concentrations between 0.

Metastatic breast cancer: preliminary results with oral hormonal therapy.

Hormonal therapy is very effective in the treatment of patients with metastatic breast cancer. Response to various therapies leads to improved quality of life and prolonged survival. This clinical trial compared two commonly utilized additive hormonal agents, tamoxifen citrate and megestrol acetate (Megace).

Role of methotrexate polyglutamates in methotrexate- and sequential methotrexate-5-fluorouracil-mediated cell kill.

The synthesis of methotrexate (MTX) polyglutamates has been investigated in a human leukemia cell line, CCRF-CEM. An increase in either the extracellular MTX concentration (0.1-10 microM) or exposure time (4-24 h) allowed a greater accumulation of polyglutamate derivatives.

Highly selective drug combinations for human colon cancer cells resistant in vitro to 5-fluoro-2'-deoxyuridine.

In the preceding companion paper, we describe a human colon carcinoma cell line that is resistant in vitro to 5-fluoro-2'-deoxyuridine by virtue of impaired nucleoside transport. Two drug combinations, methotrexate: hypoxanthine: thymidine (dThd) and 5,8-dideazaisofolic acid: dThd, selectively kill these resistant cells with no effect on the sensitive cell population. As little as 0.

Defective facilitated diffusion of nucleosides, a primary mechanism of resistance to 5-fluoro-2'-deoxyuridine in the HCT-8 human carcinoma line.

In vitro resistance of HCT-8 cells to 5-fluoro-2'-deoxyuridine (FdUrd) has been obtained after a stepwise increase (up to 1 microM) in the concentration of the nucleoside in the culture medium over a period of 6 months. With a clonogenic assay, the toxicities of 17 antineoplastic agents on HCT-8-sensitive and -resistant cells were compared. Resistant cells were 700-fold resistant to FdUrd and showed different degrees of cross-resistance to several purine and pyrimidine nucleoside analogues; no cross-resistance was noted to base analogues and other cytotoxic drugs.

The effect of split virus influenza vaccination on theophylline pharmacokinetics.

The effects of split virus influenza vaccine on the pharmacokinetics of theophylline and the in vivo and in vitro induction of interferon were studied in 23 volunteers. No effect on the total body clearance, half-life, or mean residence time of theophylline was found as a result of influenza virus vaccine. Additionally, no interferon activity was detected in vivo for as long as 24 h after vaccination.

Thymidylate synthase inhibition in cells with arrested DNA synthesis is not due to an allosteric interaction in the replitase complex.

Activity of thymidylate synthase was measured in situ in leukemia cells by tritium release from [5-3H]dUrd. Aphidicolin, an inhibitor of DNA polymerase alpha, but not thymidylate synthase, caused a time dependent inhibition of the enzyme when added to the cells after [5-3H]dUrd. Cells treated with hydroxyurea and aphidicolin in sequence before addition of [5-3H]dUrd had a high initial thymidylate synthase activity that decreased with time.

Sequence-dependent synergism between dichloromethotrexate and cisplatin in a human colon carcinoma cell line.

We studied the cell killing effects of cisplatin (CDDP), 3',5'-dichloromethotrexate (DCM), and different combinations of these drugs in a human colon carcinoma line (HCT-8). Using a clonogenic assay, the ED50 values for DCM were 3, 0.3, and 0.

Isolation and functional effects of monoclonal antibodies binding to thymidylate synthase.

Monoclonal antibodies against electrophoretically pure thymidylate synthase from HeLa cells have been produced. Antibodies (M-TS-4 and M-TS-9) from hybridoma clones were shown by enzyme-linked immunoassay to recognize thymidylate synthase from a variety of human cell lines, but they did not bind to thymidylate synthase from mouse cell lines. The strongest binding of antibodies was observed to enzyme from HeLa cells.

Methotrexate resistant cells as targets for selective chemotherapy.

Strategies that are selective for eradicating methotrexate resistant cells are described. These strategies have been developed based on knowledge of the mechanism of drug resistance encountered in experimental systems and in the clinic. Drug resistance to methotrexate in experimental tumors is commonly due to either gene amplification (dihydrofolate reductase) or to impaired transport of methotrexate.

Phase I-II trial of mitoxantrone in acute leukemia: an interim report.

We evaluated the effect of mitoxantrone (Novantrone; dihydroxyanthracenedione) in the treatment of refractory acute leukemia and acute leukemia in relapse. In this study, 70 patients are currently evaluable. Of the 25 patients who received mitoxantrone 10 mg/m2 X 5, two of 10 with ANLL in relapse, one of five with ALL in relapse achieved complete remission, and one of seven with blastic phase CML responded.

Cytotoxic effects of folate antagonists against methotrexate-resistant human leukemic lymphoblast CCRF-CEM cell lines.

A human T-lymphoblast cell line, CCRF-CEM/R1, resistant to methotrexate by virtue of increased dihydrofolate reductase activity, was grown in stepwise increasing concentrations of methotrexate. This additional selection pressure resulted in a cell line, CCRF-CEM/R2, resistant to methotrexate by virtue of both an elevation of dihydrofolate reductase activity and a marked decrease in methotrexate transport. The R1 and R2 cells were approximately 70- and 350-fold more resistant to methotrexate than were the parent cells.

Molecular and karyological analysis of methotrexate-resistant and -sensitive human leukemic CCRF-CEM cells.

A methotrexate-resistant subline, CCRF-CEM/R1, was selected stepwise from the human leukemic lymphoblast T-cell line, CCRF-CEM, and maintained in 0.2 microM methotrexate. The development of resistance to methotrexate (75-fold) was associated with a 20-fold increase of dihydrofolate reductase activity.

Constant diazepam infusion in the treatment of continuous seizure activity.

Status epilepticus is a medical emergency that requires rapid seizure control. Intravenous bolus diazepam has been used in the rapid reversal of status epilepticus; this agent usually is combined with parenteral phenobarbital or phenytoin for a more sustained suppression of seizure activity. In certain situations, these longer-acting agents are not effective in controlling the seizure disorder, necessitating alternative therapeutic measures.

Synthesis and evaluation of 2,4-diaminoquinazoline antifolates with activity against methotrexate-resistant human tumor cells.

In an attempt to find potent antifolates with selectivity against tumor cells with intrinsic or acquired resistance to methotrexate, eleven nonclassical 2,4-diaminoquinazoline antifolates were synthesized and tested as inhibitors of dihydrofolate reductase from L5178Y cells. Several compounds appeared to be good enzyme inhibitors, with I50 values around 1 nM. Two of the compounds were also good inhibitors of cell growth in vitro.

Malignant histiocytosis. Response to VP-16-213 and cytosine arabinoside.

A patient with malignant histiocytosis who relapsed after receiving an Adriamycin (doxorubicin)-containing combination and radiation therapy subsequently had a complete remission on VP-16-213 and cytosine arabinoside. She remains free of disease 32 months after achieving a complete remission. VP-16-213 and cytosine arabinoside (Ara-C) deserve further evaluation in the treatment of this neoplasm.

A follow-up of a randomized study comparing two chemotherapy treatments for advanced diffuse histiocytic lymphoma.

In 1976 we began a randomized study for the treatment of patients with stage III and IV diffuse histiocytic lymphoma. The therapy was either ACOMLA (doxorubicin, cyclophosphamide, vincristine [oncovin], methotrexate with leucovorin rescue, and cytarabine) or CHOP-B (cyclophosphamide, doxorubicin [hydroxydaunorubicin], vincristine [oncovin], prednisone, and bleomycin). A complete response (CR) was achieved in 13 (65%) of 20 patients treated with ACOMLA and in 20 (71%) of the 28 patients treated with CHOP-B.

Prophylaxis and treatment of childhood rickets with parenteral cholecalciferol.

The safety and efficacy of parenteral cholecalciferol was evaluated in the treatment and prevention of childhood rickets. Children with active disease, and those at high risk for developing rickets were treated either with intravenous or intramuscular cholecalciferol in dosages of 1000 to 1500 IU daily, for periods of 28 to 450 days. All children with rickets responded with radiographic evidence of healing.

Occurrence and significance of D-methotrexate as a contaminant of commercial methotrexate.

Methotrexate from various commercial sources has been found to contain 0.5 to 48% (w/w) of the enantiomer D-methotrexate. The two methotrexate enantiomers were separated by using chiral high-performance liquid chromatography with an octadecyl silica column and a mobile phase containing L-proline and cupric nitrate.