SEARCH · PubMed Health

Results for “Methotrexate”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources

PubMed1997

Randomised trial of systemic methotrexate versus laparoscopic salpingostomy in tubal pregnancy.

BACKGROUND: Laparoscopic salpingostomy is a well-established treatment for patients with tubal pregnancy who desire to retain fertility. Another approach that preserves the fallopian tube is medical treatment. We compared systemic methotrexate and laparoscopic salpingostomy in the treatment of tubal pregnancy. Outcome measures were treatment success, tubal preservation, and homolateral tubal patency. METHODS: Between January, 1994, and September, 1996, haemodynamically stable patients with laparoscopically confirmed unruptured tubal pregnancy and no signs of active bleeding were randomly assigned systemic methotrexate (four 1.0 mg/kg doses of intramuscular methotrexate alternated with 0.1 mg/kg oral folinic acid) or laparoscopic salpingostomy. Treatment success was defined as complete elimination of the tubal pregnancy (serum human chorionic gonadotropin < 2 IU/L) and preservation of the tube. Homolateral tubal patency was assessed by hysterosalpingography. Analysis was by intention to treat. FINDINGS: 100 patients were included in the trial. Of 51 patients allocated systemic methotrexate, 42 (82%) were successfully treated with one course; two (4%) patients needed a second course for persistent trophoblast. Surgical intervention was needed in seven (14%) patients; salpingectomy was necessary in five of these patients for tubal rupture. Of the 49 patients allocated laparoscopic salpingostomy, 35 (72%) were successfully treated by laparoscopic salpingostomy alone; salpingectomy was needed in four (8%) patients, and ten (20%) needed methotrexate for persistent trophoblast. The tube was preserved in 46 (90%) patients in the methotrexate group versus 45 (92%) in the salpingostomy group (rate ratio 0.98 [95% CI 0.87-1.1]). Homolateral tubal patency could be assessed in 81 patients: the tube was patent in 23 (55%) of 42 patients in the methotrexate group and in 23 (59%) of 39 patients in the salpingostomy group (rate ratio 0.93 [0.64-1.4]). INTERPRETATION: In haemodynamically stable patients with unruptured tubal pregnancy, systemic methotrexate and laparoscopic salpingostomy were successful in treating the majority of cases. We found no significant difference between the treatments in the homolateral patency rate. Subsequent fertility outcome has to be awaited to show which treatment yields better fertility prospects.

Adult↗

PubMed1996

Effective clearance of methotrexate using high-flux hemodialysis membranes.

We report the first series demonstrating effective clearance of methotrexate using acute intermittent hemodialysis with a high-flux dialyzer. The study was performed on six patients, two females and four males aged 13 to 72 years. All were patients at M.D. Anderson Cancer Center. Patients were dialyzed for 4 to 6 hours daily using a Fresenius F-80 membrane (Fresenius Inc, Walnut Creek, CA). Following the initiation of dialysis, there was a reduction in arterial and venous serum concentration of methotrexate with time. Mean plasma clearance of methotrexate during dialysis in these six patients was 92.1 +/- 10.3 mL/min. One patient who was nearly functionally anephric was studied in detail. In this patient, following a high dose of methotrexate (7.2 g/m2), approximately 63% of this dose was cleared with 6 hours of hemodialysis. With subsequent dialysis performed daily for 6 hours, the drug was cleared completely in 5.6 +/- 0.3 days (n = 7 separate methotrexate treatments). A reduction in plasma methotrexate concentration from 1,733 +/- 40 micromol/L 1 hour postinfusion to less than 0.3 micromol/L in 5 to 6 days was observed for these seven separate treatments. We conclude that significant clearance of methotrexate can be achieved with high-flux dialyzers, making methotrexate therapy a viable treatment option in patients with responsive malignancies despite the presence of renal failure.

Adolescent↗

PubMed2004

[Medical treatment of ectopic pregnancy: a randomized clinical trial comparing metotrexate-mifepristone and methotrexate-placebo].

BACKGROUND: Medical treatment of ectopic pregnancy is widespread. To increase the efficacy of methotrexate, combination with mifepristone has been proposed. METHODS: We performed a large prospective multicentre double-blind sequential randomized trial in order to compare the efficacy of methotrexate and mifepristone (600 mg given orally) versus methotrexate and placebo. RESULTS: Two hundred twelve ectopic pregnancies were randomized. There was no significant difference in the initial characteristics between the 2 groups. There was no significant difference in the success rate of medical treatment between the methotrexate-mifepristone (n=113) and the methotrexate-placebo group (n=99): 79.6% (90/113) vs 74.2% (72/97) respectively, RR [95% CI]: 1.07 [0.92-1.25], p=0.41. However, there was a quantitative interaction between progesterone level and effect of treatment: when progesterone level was 10 ng/l, the efficacy of the combination of mifepristone and methotrexate was significantly higher than the combination of methotrexate and placebo, with a 83.3% success rate (15/18) vs 38.5% (5/13) respectively. CONCLUSION: Our study failed to demonstrate any benefit of the addition of mifepristone to methotrexate. By contrast, the quantitative interaction between treatment effect and base line serum progesterone suggested that this combination could be reserved to ectopic pregnancies associated with high serum progesterone concentrations.

Abortifacient Agents, Nonsteroidal↗

PubMed2001

Clinical and pregnancy outcome following ectopic pregnancy; a prospective study comparing expectancy, surgery and systemic methotrexate treatment.

BACKGROUND: The improved possibility of an early diagnosis of ectopic pregnancy by use of serial quantitative beta-subunit human chorionic gonadotropin hormone levels together with transvaginal ultrasound has opened up options for conservative treatment. Systemic methotrexate treatment of unruptured ectopic pregnancy has emerged as a safe and effective alternative to surgical procedures. The aim of the present study was to investigate the effectiveness of methotrexate treatment in routine clinical practice, but also to assess pregnancy outcome during a 2.5-year follow-up period. METHODS: All patients presenting to the Department of Obstetrics and Gynecology, Umeå University Hospital, with signs and symptoms of ectopic pregnancy between January 1, 1995 and December 31, 1997 were included in this prospective study. Patients with ectopic pregnancy were either managed expectantly, treated with methotrexate or by laparoscopic or open surgery (salpingostomy/salpingectomy). Systemic methotrexate (Pharmacia & Upjohn, Stockholm, Sweden) was administered as an intramuscular injection of 50 mg/m(2). RESULTS: One hundred and seven patients presented with signs and symptoms of a possible ectopic pregnancy, of these 89 patients eventually were diagnosed as having an ectopic pregnancy. Twenty-six (29%) patients were treated with methotrexate, 46 (52%) patients with laparoscopy or laparotomy, and 17 (19%) patients by expectant management. Success rate in the methotrexate group, after one or more injections, was 77% (20 patients out of 26). The mean time to resolution was 24+/-9 days. There was no difference in pregnancy rate following methotrexate treatment compared to surgical treatment. CONCLUSIONS: Systemic single-dose methotrexate treatment is a safe treatment option with a reasonably high success rate, with similar probability of a later intrauterine pregnancy as conventional surgical treatment.

Abortifacient Agents, Nonsteroidal↗

PubMed1998

Cyclophosphamide, methotrexate and infusional 5-fluorouracil (infusional CMF) in metastatic breast cancer.

Bolus 5-fluorouracil (5-FU) is a phase-specific drug with a short plasma half-life that is used in combination with bolus cyclophosphamide and methotrexate in the treatment of breast cancer. The efficacy of 5-FU can be improved by continuous intravenous infusion using portable infusion pumps (infusional 5-FU). Infusional 5-FU, 200 mg m(-2) day(-1), in combination with standard doses of bolus cyclophosphamide and methotrexate, was evaluated in a phase I/II dose-finding study. The cyclophosphamide and methotrexate were administered in 28-day cycles as follows: cohort 1, cyclophosphamide 600 mg m(-2), days 1 and 8, and methotrexate 40 mg m(-2), day 1; cohort 2, cyclophosphamide 400 mg m(-2), days 1 and 8, and methotrexate 40 mg m(-2), day 1; cohort 3, cyclophosphamide 480 mg (m-2), days 1 and 8, and methotrexate 40 mg m(-2), day 1; cohort 4, cyclophosphamide 480 mg m(-2), days 1 and 8, and methotrexate 40 mg m(-2), days 1 and 8. Median overall survival was 10 months (range 3-21 months). Objective tumour responses were seen in 9 of 25 patients (36%, 95% CI 18-58%), including 3 of 13 patients (23%) previously treated for metastatic disease. Cohorts 1 and 4 proved to be too toxic, with five of six patients in cohort 1 and three of four in cohort 4 developing grade III/IV neutropenia. The dose intensity of cyclophosphamide achieved was as follows: cohort 1, 82%; cohort 2, 86%; cohort 3, 97%; cohort 4, 90%. Infusional 5-FU can be administered safely and is effective in combination with cyclophosphamide 480 mg m(-2), days 1 and 8, and methotrexate 40 mg m(-2), day 1, in the treatment of metastatic breast cancer.

Adult↗

PubMed1990

Coadministration of naproxen and low-dose methotrexate in patients with rheumatoid arthritis.

Fifteen patients (30 to 78 years of age) with diagnoses of rheumatoid arthritis were administered oral and intravenous methotrexate (15 mg), alone or with concomitant naproxen (1000 mg/day). Serial blood samples and urine were collected for 24 hours after the dose of methotrexate and were assayed for methotrexate by a specific radioenzymatic method. In twelve patients who completed the study, methotrexate systemic clearance was not statistically different with naproxen (103.3 +/- 35.0 ml/min) versus without naproxen (113.4 +/- 48.3 ml/min; p = 0.37). Oral clearance of methotrexate was not statistically different with naproxen (161.7 +/- 55.0 ml/min) versus without naproxen (176.7 +/- 68.3 ml/min; p = 0.14). Likewise, there was not a significant difference in methotrexate renal clearance or plasma protein binding with or without naproxen. No toxicity was observed when patients received methotrexate alone or with naproxen. This study indicates that concomitant naproxen does not abruptly alter the disposition of low-dose methotrexate in patients with rheumatoid arthritis who have normal renal function.

Absorption↗

PubMed1997

The absorption of low-dose methotrexate in patients with inflammatory bowel disease.

BACKGROUND: Recent clinical trials have demonstrated that methotrexate may have an important therapeutic role in the treatment of patients with inflammatory bowel disease, who are either refractory or intolerant to traditional medical therapy. The aim of this study was to evaluate the pharmacokinetics of low-dose oral methotrexate in patients with inflammatory bowel disease. METHODS: Methotrexate (12.5 mg) was given orally to nine patients with inflammatory bowel disease: five with Crohn's disease, and four with ulcerative colitis, and to six patients with rheumatoid arthritis who served as a control group. Blood samples were drawn at specific intervals to evaluate methotrexate plasma levels. RESULTS: Methotrexate was rapidly absorbed in all patients. Peak concentrations (Cmax) varied considerably, ranging from 0.25-0.87 micro M. The mean Cmax values were similar in all patient groups (0.59 +/- 0.12, 0.69 +/- 0.16 and 0.54 +/- 0.18 micro M, P not significant) for Crohn's disease, ulcerative colitis and rheumatoid arthritis, respectively. The mean area under curve in 120 min (AUC0-120) was also similar in all patient groups (32.9 + 11.3, 43.6 + 9.9 and 41.8 + 14.9 ng.min/mL, P not significant) for Crohn's disease, ulcerative colitis and rheumatoid arthritis, respectively. The mean time to reach Cmax, (tmax), varied between patient groups (84, 112 and 95 min, respectively, with a significant difference, P < 0.02, between the Crohn's disease and ulcerative colitis groups. A negative correlation was found between methotrexate dosage/kg and Cmax (r = -0.74) only in Crohn's disease patients but not in the other patient groups. CONCLUSIONS: Orally administered methotrexate is well absorbed in patients with inflammatory bowel disease including those with severe small bowel disease or resection. If methotrexate is proven to be effective in inflammatory bowel disease, it should be administered orally.

Adult↗

PubMed1996

Methotrexate in chronic active ulcerative colitis: a double-blind, randomized, Israeli multicenter trial.

BACKGROUND & AIMS: Uncontrolled studies have suggested that methotrexate may be effective in patients with active ulcerative colitis. The aim of this study was to evaluate the effectiveness of oral methotrexate in chronic steroid-dependent ulcerative colitis in a randomized, double-blind multicenter trial. METHODS: Patients with active ulcerative colitis who have received steroids and/or immunosuppressives for at least 4 months during the preceding 12 months with a current Mayo Clinic score of > or = 7 were included in the study. Methotrexate (12.5 mg) or placebo was added to their treatment once weekly for 9 months. RESULTS: Sixty-seven patients were included (methotrexate, 30 patients, placebo, 37 patients). The proportion of patients entering first remission (methotrexate, 46.7%; placebo, 48.6%), the time to reach first remission (methotrexate, 4.1 +/- 1.9 months; placebo, 3.4 +/- 1.7 months), as well as the proportions of patients having a relapse after first remission (methotrexate, 64.3%; placebo, 44.4%) were not significantly different between the two groups. The mean Mayo Clinic score, the mean monthly steroid dose, and the proportion of abnormal laboratory results during the study were also similar. CONCLUSIONS: Methotrexate at a weekly oral dose of 12.5 mg was not found to be better than placebo in the induction or maintenance of remission in patients with chronic active ulcerative colitis.

Administration, Oral↗

PubMedDate not supplied

[The effect of methotrexate pharmacokinetics and of leucovorin rescue on the prognosis of osteosarcoma].

A total of 129 high-dosage methotrexate therapies performed in 19 patients with osteosarcoma were retrospectively analyzed. Serum methotrexate peak concentrations were found to vary widely, both inter-individually as well as in the same patient. The measured MTX peak concentrations correlated closely with pharmacokinetic data such as area under the curve and total body clearance. No correlations were found between the serum MTX correlations and different times after methotrexate administration. Increase in leucovorin rescue or low MTX peak concentrations were associated with poor prognosis. High-dosage methotrexate therapies with leucovorin rescue need to be further optimized in accordance with biochemical knowledge of the mode of action and the individual pharmacokinetic data of methotrexate. Such optimization may be expected to improve the prognosis for osteosarcoma. Serum methotrexate concentrations should be determined not only 24, 48, and 72 hours after methotrexate administration, in order to avoid elevated toxicity of the therapy, but also at the start of methotrexate infusion, in order to influence MTX peak concentrations at an early stage if necessary. Measurement of L-leucovorin in serum will be necessary, to enable a restrictive leucovorin rescue to be performed safely.

Adolescent↗

PubMed1983

Comparison of intermediate-dose methotrexate with cranial irradiation for the post-induction treatment of acute lymphocytic leukemia in children.

We compared two regimens with respect to their ability to prolong disease-free survival in 506 children and adolescents with acute lymphocytic leukemia. All responders to induction therapy were randomized to treatment with 2400 rad of cranial irradiation plus intrathecal methotrexate or to treatment with intermediate-dose methotrexate plus intrathecal methotrexate, as prophylaxis for involvement of the central nervous system and other "sanctuary" areas. Patients were then treated with a standard maintenance regimen. Complete responders were stratified into either standard-risk or increased-risk groups on the basis of age and white-cell count at presentation. Among patients with standard risk, hematologic relapses occurred in 9 of 117 given methotrexate and 24 of 120 given irradiation (P less than 0.01). The rate of central-nervous-system relapse was higher in the methotrexate group (23 of 117) than in the irradiation group (8 of 120) (P = 0.01). Among patients with increased risk, radiation offered greater protection to the central nervous system than methotrexate (P = 0.03); there was no difference in the rate of hematologic relapse. In both risk strata the frequency of testicular relapse was significantly lower in the methotrexate group (1 patient) than the radiation group (10 patients) (P = 0.01). Methotrexate offered better protection against systemic relapse in standard-risk patients and better protection against testicular relapse overall, but it offered less protection against relapses in the central nervous system than cranial irradiation.

Adolescent↗

PubMed1986

Clinical pharmacodynamics of high-dose methotrexate in acute lymphocytic leukemia. Identification of a relation between concentration and effect.

High-dose methotrexate (500 to 33,600 mg per square meter of body-surface area) with leucovorin rescue is a common component of therapy for acute lymphocytic leukemia. To increase understanding of the relation between the serum concentration and the effect of methotrexate, we conducted a randomized, prospective study of 108 children with "standard-risk" acute lymphocytic leukemia who were treated with 15 doses of methotrexate (1000 mg per square meter) that were infused over 24 hours. The median length of follow-up was 3.5 years from diagnosis for patients still in remission. Variability between patients in methotrexate clearance produced steady-state serum concentrations that ranged from 9.3 to 25.4 microM. Patients with median methotrexate concentrations of less than 16 microM (n = 59) had a lower probability of remaining in remission (P less than 0.05) than patients with concentrations of 16 microM or more (n = 49). Multivariate analyses indicated that patients with methotrexate concentrations of less than 16 microM were 3 times more likely to have any kind of relapse during therapy (P = 0.01) and 7 times more likely to have a hematologic relapse during therapy (P = 0.001). Stepwise Cox's regression identified leukemic-cell DNA content, methotrexate concentration, and hemoglobin as significant prognostic variables for hematologic relapse (P = 0.0005). We conclude that there is a concentration-effect relation for high-dose methotrexate in acute lymphocytic leukemia and that 1000 mg per square meter infused over a period of 24 hours may not be optimal for patients with relatively fast drug clearance.

Adolescent↗

PubMed1992

Methotrexate in resistant juvenile rheumatoid arthritis. Results of the U.S.A.-U.S.S.R. double-blind, placebo-controlled trial. The Pediatric Rheumatology Collaborative Study Group and The Cooperative Children's Study Group.

BACKGROUND: The antimetabolite methotrexate has been shown in placebo-controlled trials to be effective in adults with rheumatoid arthritis. Methotrexate may also be effective in children with resistant juvenile rheumatoid arthritis, but the supporting data are from uncontrolled trials. METHODS: Centers in the United States and the Soviet Union participated in this randomized, controlled, double-blind trial designed to evaluate the effectiveness and safety of orally administered methotrexate. Patients received one of the following treatments each week for six months: 10 mg of methotrexate per square meter of body-surface area (low dose), 5 mg of methotrexate per square meter (very low dose), or placebo. The use of prednisone (less than or equal to 10 mg per day) and two nonsteroidal antiinflammatory drugs was also allowed. RESULTS: The 127 children (mean age, 10.1 years) had a mean duration of disease of 5.1 years; 114 qualified for the analysis of efficacy. According to a composite index of several response variables, 63 percent of the children who received low-dose methotrexate improved, as compared with 32 percent of those in the very-low-dose group and 36 percent of those in the placebo group (P = 0.013). As compared with the placebo group, the low-dose group also had significantly larger mean reductions from base line in the number of joints with pain on motion (-11.0 vs. -7.1), the pain-severity score (-19 vs. -11.5), the number of joints with limited motion (-5.4 vs. -0.7), and the erythrocyte sedimentation rate (-19.0 vs. -6 mm per hour). In the methotrexate groups only three children had the drug discontinued because of mild-to-moderate side effects; none had severe toxicity. CONCLUSIONS: Methotrexate given weekly in low doses is an effective treatment for children with resistant juvenile rheumatoid arthritis, and at least in the short term this regimen is safe.

Administration, Oral↗

PubMed1995

Methotrexate for the treatment of Crohn's disease. The North American Crohn's Study Group Investigators.

BACKGROUND: Although corticosteroids are highly effective in improving symptoms of Crohn's disease, they may have substantial toxicity. In some patients, attempts to discontinue corticosteroids are unsuccessful. METHODS: We conducted a double-blind, placebo-controlled multicenter study of weekly injections of methotrexate in patients who had chronically active Crohn's disease despite a minimum of three months of prednisone therapy. Patients were randomly assigned to treatment with intramuscular methotrexate (25 mg once weekly) or placebo for 16 weeks. The patients also received prednisone (20 mg once a day), which was tapered over 10 weeks unless their condition worsened. The primary outcome measure was clinical remission at the end of the 16-week trial. Remission was defined by the discontinuation of prednisone and a score of < or = 150 points on the Crohn's Disease Activity Index. RESULTS: A total of 141 patients were randomly assigned in a 2:1 ratio to methotrexate (94 patients) or placebo (47 patients). After 16 weeks, 37 patients (39.4 percent) were in clinical remission in the methotrexate group, as compared with 9 patients (19.1 percent) in the placebo group (P = 0.025; relative risk, 1.95; 95 percent confidence interval, 1.09 to 3.48). The patients in the methotrexate group received less prednisone overall than those in the placebo group (P = 0.026). The mean (+/- SE) score on the Crohn's Disease Activity Index after 16 weeks of treatment was significantly lower in the methotrexate group (162 +/- 12) than in the placebo group (204 +/- 17, P = 0.002). The changes in quality-of-life scores and serum orosomucoid concentrations were similar. In the methotrexate group, 16 patients (17 percent) withdrew from treatment because of adverse events (including asymptomatic elevation of serum aminotransferase in 7 and nausea in 6), as compared with 1 patient (2 percent) in the placebo group. CONCLUSIONS: In a group of patients with chronically active Crohn's disease, methotrexate was more effective than placebo in improving symptoms and reducing requirements for prednisone.

Adult↗

PubMed2002

Oral methotrexate for treatment of ectopic pregnancy.

OBJECTIVE: The purpose of this study was to evaluate oral methotrexate tablets in the treatment of ectopic pregnancy. STUDY DESIGN: Patients with a diagnosis of ectopic pregnancy were offered oral methotrexate tablets rather that intramuscular injection. Oral methotrexate was given in 2 divided doses 2 hours apart at a dose of 60 mg/m(2) with standard 2.5 mg methotrexate tablets. Patients were followed up with the use of the same protocol that was used typically for intramuscular methotrexate. RESULTS: Nineteen of 22 patients (86%) were successfully treated. There was no statistical difference between patients who were treated successfully or unsuccessfully, with respect to initial human chorionic gonadotropin titers (P =.55), ectopic size (P =.77), or methotrexate dose (P =.18). Nineteen of 22 patients (86%) had increased pain during treatment. Outside of pain, gastrointestinal side effects were the most common. Thirty-two percent of patients required more than one treatment cycle. CONCLUSION: Oral methotrexate can be used to treat ectopic pregnancy successfully, but there are few advantages to recommend its use over intramuscular methotrexate.

Abortifacient Agents, Nonsteroidal↗

PubMed2003

Targeting Ras signaling through inhibition of carboxyl methylation: an unexpected property of methotrexate.

The antifolate methotrexate is one of the most successful drugs in cancer chemotherapy. Although its efficacy is widely attributed to a decrease in nucleotide biosynthesis (1), methotrexate is known to increase homocysteine (2), a compound associated with an elevated risk of heart disease, Alzheimer's disease (3), and neural tube defects (4). A potential mechanism for the detrimental effects of homocysteine is cellular hypomethylation from an increase in S-adenosylhomocysteine (5), an inhibitor of methyltransferases including isoprenylcysteine carboxyl methyltransferase (Icmt). Among the substrates of Icmt is the monomeric G protein Ras, a critical component of many signaling pathways that regulate cell growth and differentiation. Because carboxyl methylation of Ras is important for proper plasma membrane localization and function (6), we investigated the role of Icmt in the antiproliferative effect of methotrexate. After methotrexate treatment of DKOB8 cells, Ras methylation is decreased by almost 90%. This hypomethylation is accompanied by a mislocalization of Ras to the cytosol and a 4-fold decrease in the activation of p44 mitogen-activated protein kinase and Akt. Additionally, cells lacking Icmt are highly resistant to methotrexate. Whereas cells expressing wild-type levels of Icmt are inhibited by methotrexate, stable expression of myristoylated H-Ras, which does not require carboxyl methylation for membrane attachment (7), confers resistance to methotrexate. These results suggest that inhibition of Icmt is a critical component of the antiproliferative effect of methotrexate, expanding our understanding of this widely used drug and identifying Icmt as a target for drug discovery.

Animals↗

PubMed1978

Conjugation of methotrexate to poly(L-lysine) increases drug transport and overcomes drug resistance in cultured cells.

Methotrexate and [(3)H]methotrexate were conjugated through a carbodiimide-catalyzed reaction to a 70,000 molecular weight poly(L-lysine) in molar ratios of approximately 13 to 1. The cellular uptake of labeled conjugate was far in excess of the uptake of free drug in cells that were either proficient or deficient in methotrexate transport. The conjugate markedly inhibited the growth of PRO(-)3 Mtx(RII) 5-3 Chinese hamster ovary cells, which are known to be drug resistant by virtue of a deficient methotrexate transport. The cells, however, were not inhibited by the same concentrations of free poly(Lys) and free drug. The 100-fold difference in drug concentration needed to inhibit the mutant cells and their corresponding wild type was totally abolished by exposing the methotrexate-resistant cells to methotrexate-poly(Lys). That the drug is carried into the resistant cells as intact drug-poly(Lys) is evident also from the fact that the conjugate is rendered inactive by brief trypsinization in vitro. Because the conjugate fails to inhibit dihydrofolate reductase (5,6,7,8-tetrahydrofolate: NADP(+) oxidoreductase; EC 1.5.1.3) in vitro, it must be concluded that the strong growth inhibitory effect of the conjugate is due to the intracellular hydrolysis of its polymeric backbone, followed by the release inside the cell of a pharmacologically active form of methotrexate. Our date show that in methotrexate-resistant cells the intracellular release of active drug after uptake of conjugate is of the same order of magnitude as the uptake of free drug by transport-proficient cells and, hence, that the drug resistance due to deficient transport can be totally overcome.

Biological Transport↗

PubMed1980

Methotrexate polyglutamate synthesis by cultured human breast cancer cells.

We studied the conversion of methotrexate to poly-gamma-glutamyl derivatives by cultured human breast cancer cells. After incubation with 2 micro M [3',5',9-3H]methotrexate, MCF-7 cells were washed free of extracellular drug and were boiled to lyse cells and to release drug bound to dihydrofolate reductase (tetrahydrofolate dehydrogenase; 5,6,7,8-tetrahydrofolate:NADP+ oxidoreductase, EC 1.5.1.3). The supernatant fraction was chromatographed on Sephadex G-15 to separate parent drug from polyglutamate forms. These cells rapidly and quantitatively converted methotrexate to polyglutamates, such that after 24 hr of incubation, 70 +/- (SEM) 3% of intracellular methotrexate existed as polyglutamates. Examination of that portion of intracellular methotrexate specifically bound to dihydrofolate reductase indicated that, with prolonged incubation, methotrexate polyglutamates become the predominant drug form bound to the enzyme. These studies demonstrate that methotrexate polyglutamates are readily formed in human tumor cells and bind to dihydrofolate reductase. Because these forms of the drug may be selectively retained within the cell, they may be important determinants of the duration of action and, ultimately, the cytotoxicity of methotrexate in human solid tumors.

Breast Neoplasms↗

PubMed1983

Model for specific rescue of normal hepatocytes during methotrexate treatment of hepatic malignancy.

We utilized the presence of hepatic receptors for galactose-terminal glycoproteins to achieve specific rescue of differentiated hepatocytes from methotrexate toxicity. This was accomplished by administration of a conjugate formed by covalent coupling of the methotrexate antagonist, folinic acid (leucovorin), to galactose-terminating (desialylated) bovine fetuin. Two cultured hepatocyte-derived cell lines were chosen to test rescue from methotrexate toxicity: Hep G2 cells are capable of receptor-mediated endocytosis of galactose-terminating glycoproteins; PLC/PRF/5 cells are not. In the presence of methotrexate alone, both cells lines were reduced in number to 20% of control populations by day 5. Growth rates of both lines returned to normal when free folinic acid was added to the medium containing methotrexate. When asialofetuin-folinic acid conjugate was given to both cell lines in the presence of methotrexate, Hep G2 cells doubled their numbers by day 4 and reached control (without methotrexate) populations by day 8. However, PLC/PRF/5 cells failed to respond to administered asialofetuin-folinic acid conjugate under identical conditions, and the growth curve was the same as that for cells which received methotrexate alone. Conjugates of asialofetuin bound to folic acid (folate derivative requiring dihydrofolate reductase activity for conversion to an active metabolite) and fetuin (non-galactose-terminal glycoprotein) linked to folinic acid also were made for control studies. These conjugates failed to rescue either cell line.

Asialoglycoprotein Receptor↗