Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Seventeen patients with low- or medium-risk gestational trophoblastic tumors (GTT) and one patient with a placental-site trophoblastic tumor were treated according to an 8-day schedule of low-dose methotrexate (LDMTX) alternating with citrovorum factor (CF). Plasma concentrations of methotrexate (MTX) were correlated with serum human chorionic gonadotropin (hCG) levels and clinical response. After an intramuscular dose of 50 mg, plasma MTX levels rose rapidly, reached a peak concentration of 5.8 x 10(-6) M/liter at 1 hour and persisted above 10(-6) M/liter normally considered inhibitory for DNA synthesis, for approximately 7 1/2 hours. Rapid plasma clearance followed with plasma levels reaching 5-7 x 10(-8) M/liter at the time of CF administration. At 48 hours, plasma MTX levels continued to exceed 10(-8) M/liter--the break point for the appearance of clinical toxicity due to MTX. In six of sixteen, or 38%, an initial rise in hCG levels was observed. Five of the seventeen patients, or 29%, and the one patient with PSTT developed MTX resistance. The administered dose (approximately 30 mg/M2) and plasma pharmacokinetics did not differ significantly between the tumors that responded and became resistant to MTX. The authors conclude that MTX resistance in GTT occurs as a result of impaired cell membrane uptake, gene amplification of dihydrofolate reductase, or both.
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PMID:Correlation of plasma methotrexate concentration with human chorionic gonadotropin and therapeutic response to low-dose methotrexate-citrovorum factor in low-medium-risk gestational trophoblastic tumors. 164 54

A human choriocarcinoma cell line, HCCM-5, was fed with medium containing increasing concentrations of methotrexate (MTX). The initial MTX concentration, 10(-9) M which reduced the [3H] thymidine incorporation into DNA, was raised from 2- to 2.5-fold successively. After about 36 weeks of feeding, the cells became resistant to 5 X 10(-7) M which produced complete inhibition of the parent HCCM-5 cell growth. The parent line and its MTX-resistant subline (HCCM-5MTXr) had almost the same population doubling time. There were no apparent differences in morphology and human chorionic gonadotropin secretion between the two cell lines. The development of resistance was accompanied by a 10-fold decrease in the 3H-MTX uptake and a 5-fold elevation of the intracellular dihydrofolate reductase (DHFR) activity. The impairment of MTX transport in HCCM-5MTXr cells continued after transferring the HCCM-5MTXr cells into MTX-free medium, whereas the DHFR activity returned to the level found in the HCCM-5 cells. These results indicate that the MTX resistance acquired in choriocarcinoma cells chiefly involves the impaired transport of MTX and continues after the deprivation of the drug.
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PMID:Development of methotrexate-resistant human choriocarcinoma cells in culture. 403 87

The effect of methotrexate (MTX) on the growth and human chorionic gonadotropin (hCG) secretion of five gestational and two nongestational human choriocarcinoma cell lines was studied in vitro. A striking heterogeneity in hCG secretion was noted among the cell lines. The growth of cells which secreted large quantities of hCG, such as HCCM-5, BeWo, and IMa, was inhibited by continuous exposure to 2 X 10(-8)M MTX. In contrast, cells which secreted little hCG, such as SCH, ENAMI-1, and GCH-1, showed no response to the growth inhibitory action of 2 X 10(-8)M MTX and the 3H-thymidine uptake was not reduced by treatment with MTX at doses of up to 10(-4)M for 48 hours. The common morphologic alterations observed in the cells which responded to MTX were an increase in the number of multinucleated giant cells, the appearance of vacuoles and granules in the cytoplasm, and enlargement of the nuclei. Increased hCG secretion was observed in accordance with the appearance of such morphologically altered cells. Part of the mechanisms of resistance to MTX appeared to involve both impairment of MTX uptake by the cells and an increase in the level of intracellular dihydrofolate reductase.
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PMID:Effect of methotrexate on the growth and human chorionic gonadotropin secretion of human choriocarcinoma cell lines in vitro. 668 28

The sensitivity to methotrexate (MTX) and mechanisms of the drug resistance of seven kinds of human choriocarcinoma cell lines were studied in vitro. The results were as follows. Each cell line of HCCM-5 , BeWo, IMa, and NUC-1 secreted more than 200ng/10(6) cells/48 hours of human chorionic gonadotropin (hCG), whereas GCH-1, ENAMI-1, and SCH secreted less than 20ng/10(6) cells/48 hours. HCCM-5 cell line was the most sensitive to MTX judging from the inhibition of both 3H-thymidine uptake and cell growth in vitro. Each cell line of BeWo, IMa, and NUC-1 revealed sensitivity to 2 X 10(-8)M MTX, but such cell lines as GCH-1, ENAMI-1, and SCH showed resistance to MTX. The cell lines which revealed sensitivity to MTX incorporated more 3H-MTX and showed less intracellular dihydrofolate reductase activity than resistant cell lines.
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PMID:[MTX sensitivity and the mechanism of resistance of various choriocarcinoma cells in culture]. 668 70

Chimeric genes were constructed by fusing of human GH (hGH) cDNA to one, two, or three cassettes of the carboxyl-terminal peptide (CTP) of human chorionic gonadotropin (hCG)-beta-subunit. hGH variant genes were inserted into the pCI-DHFR plasmid, transfected into DG44 cells, and stable clones were selected. Bioactivity and pharmacokinetic studies were performed in hypophysectomized Sprague Dawley derived male rats. The results indicated that sc injections of GH-wild-type (WT), Biotropin (commercial), GH-CTP, or CTP-GH (0.6 mg/kg) once every 5 d for 11 d (total dose of 1.2 mg/kg) resulted in an increased weight gain by 4, 4.9, 5.1, and 7 g, respectively. Treatment with CTP-GH-CTP-CTP (GH-LA) or CTP-GH-CTP (0.6 mg/kg) once every 5 d for 11 d or with Biotropin (0.12 mg/kg) daily for 11 d (total dose 1.2 mg/kg) resulted in a dramatic increase in weight gain of 16.5, 16.8, and 17 g, respectively. Repeated injections with different doses of GH-LA, 0.6, 1.8 mg/kg every 4 d or daily injection of 0.12 mg/kg of Biotropin increased the weight gain by 16, 28, and 18 gr, respectively. In addition, the cumulative serum levels of IGF-I after injection of GH-LA was significantly higher than that detected after injection of Biotropin. Pharmacokinetic studies indicated that the half-life, mean residence time, area under the curve, time of maximal plasma concentration, and maximal plasma concentration of GH-LA are dramatically increased compared with Biotropin. This may suggest that the mechanism of GH metabolic clearance is affected by the presence of CTP. These data establish a rationale for using this chimera as a long-acting GH analog.
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PMID:Designing a long-acting human growth hormone (hGH) by fusing the carboxyl-terminal peptide of human chorionic gonadotropin beta-subunit to the coding sequence of hGH. 2066 71