Resistance methotrexate

Sirotnak FM, Moccio DM, KelleherLE, Goutas LJ (1981) Relative frequency and kinetic properties of transport-defective phenotypes among methotrexate-resistant L1210 clonal cell lines derived in vivo. Cancer Res. 41 4447 4452. 

Schimke RT (1986) Methotrexate resistance and gene amplification. Mechanisms and implications. Cancer 57 1912-1917... 

Dolnick BJ, Pink JJ. Effects of 5-fluorouracil in dihydrofolate reductase and dihydrofolate reductase mRNA from methotrexate-resistant KB cells. J Biol Chem 1985 260 3006-3014. 

W.M. Spees, T.P.F. Gade, G.L. Yang, W.P. Tong, W.G. Bornmann, R. Gorlick, J.A. Koutcher, An F-19 magnetic resonance-based in vivo assay of solid tumor methotrexate resistance Proof of principle, Clin. Cancer Res. 11 (2005) 1454-1461. 

Kaufman RJ, Brown PC, Schimke RT. Amplified dihydrofolate reductase genes in unstably methotrexate-resistant cells are associated with double minute chromosomes. Proc Natl AcadSci USA 1979 76 5669-5673. 

The main folate antagonist is methotrexate, an analogue of folic acid. Methotrexate competitively inhibits dihydrofolate reductase, the enzyme responsible for the synthesis of purine and pyramidine from folic acid. Trimetrexate, a methotrexate analogue, is useful in treating methotrexate-resistant tumours. It is also used to treat Pneumocystis carinii infections. Methotrexate is usually given orally, but may also be given intravenously or intrathecally. In addition to its use in cancer therapy, it is used in the treatment of psoriasis. Methotrexate can cause an obstructive nephropathy due to its precipitation in the renal calyx. 

After several weeks of chemotherapy in the form of methotrexate, a cancer patient s tumor begins to show signs of resistance to treatment. Which of the following mechanisms is most likely to explain the tumor s methotrexate resistance ... 

Consequently, in methotrexate-resistant strains of Leishmania (and also in cancer cells) both enzyme activities are increased equally by gene amplification.423 This presents a serious problem in the treatment of... 

O Hare, K., Benoist, C. and Breathnach, R. (1981) Transformation of mouse fibroblasts to methotrexate resistance by a recombinant plasmid expressing a prokaryotic dihydrofolate reductase. Proc. Natl. Acad. Sci. USA, 78, 1527-1531. 

Resistance Nonproliferating cells are resistant to methotrexate. Resistance in neoplastic cells can be due to amplification (production of additional copies) of the gene that codes for dihydrofolate reductase resulting in increased levels of this enzyme. The enzyme affinity for MTX may also be diminished. Resistance can also occur from a reduced influx of MTX, apparently caused by a change in the carrier-mediated transport responsible for pumping methotrexate into the cell. 

Such methotrexate-resistant cells are found in cancer patients who had been given methotrexate as a single agent, where a remission is followed by relapse with drug-resistant cancer. 

QSAR analysis of studies at the cellular level allows us to get a handle on the physicochemical parameters critical to pharmacokinetics processes, mostly transport. Cell culture systems offer an ideal way to determine the optimum hydrophobicity of a system that is more complex than an isolated receptor. Extensive QSAR have been developed on the toxicity of 3-X-triazinesto many mammalian and bacterial cell lines (202, 209). A comparison of the cytotoxicities of these analogs vs. sensitive murine leukemia cells (L1210/S) and methotrexate-resistant murine leukemia cells (L1210/R) reveals some startling differences. 

Miller AD, Law MF, Verma IM. 1985. Generation of helper-free amphotropic retroviruses that transduce a dominantacting, methotrexate-resistant dihydrofolate reductase gene. Mol. Cell. Biol. 5 431-37... 

R.T., Urlaub, G., and Chasin, LA. (1978) Amplified dihydrofolate reductase genes are localized to a homogeneously staining region of a single chromosome in a methotrexate-resistant Chinese hamster ovary cell line. Proc. Natl. Acad. Sci. USA 75 5553-5556. 

Ouellette, M., Fase-Fowler, F. and Borst, P. (1990) The amplified H circle of methotrexate-resistant Leishmania tatrentolae contains a novel P-glycoprotein gene. EMBO J. 9 1027-1033. 

Kaur, K., Coons, T., Emmett, K., and Ullman, B. (1988) Methotrexate-resistant Leishmania donovani genetically deficient in the folate-methotrexate transporter. J. Biol. Chem. 263 7020-7028. 

Beverley, S. M., Coderre, J. A., Santi, D. V. and Schimke, R. T. (1984) Unstable DNA amplifications in methotrexate-resistant Leishmania consist of extrachromosomal circles which relocalize during stabilization. Cell 38 431-439. 

Reduction-sensitive spacers. Shen and Ryser coupled methotrexate via a disulphide-containing spacer with poly(D-lysine). " The conjugate was able to enter methotrexate-resistant cell lines cultured in vitro. There was evidence for a reductive cleavage of tlje spacer in the cytosol compartment. This example indicates another possibility for achieving intracellular release of drugs from polymeric conjugates by proper selection of the spacer. 

It is used in the treatment or rhabdomyosarcoma in children and methotrexate-resistant choricarcinoma in women. It has also been used to inhibit immunoligical response particularly the rejection of renal transplants. 

Wilm s, Ewing sarcoma, embryonal rhabdomyosarcoma, methotrexate-resistant gestational choriocarcinoma, testicular tumors... 

Figure 5. Overexpression of PTRl, a known methotrexate resistance protein, in a drug resistant strain of L. major (strain MTX 60.2). A. Comparison of 2D gel images revealed a highly overexpressed spot in the resistant mutant versus the wildtype. MALDI-TOF analysis identified the spot as PTRl. B. DNA amplification (visible in the ethidium bromide-stained panel to the left) is a common mechanism of protein overexpression in Leishmania. Southern hybridisation using a PTRl probe (right panel) confirmed a substantial amplification of the PTRl gene, providing a mechanism for the overexpression seen by 2D gels.

Richard D, Kundig C, Ouellette M. A new type of high afiinity folic add transporter in the protozoan parasite Ldshmania and deletion of its gene in methotrexate-resistant cells. J Biol Chem 2002 277(33) 29460-29467. 

Drummelsmith J, Girard I, Trudel N et al. Difierential protein expression analysis c Leishmania major reveals novel roles for methionine adenosyltransferase and S-adenosylmethionine in methotrexate resistance. J Bioi Chem 2004 279(32) 33273-80. 

The purpose of this present paper Is to review the Information obtained from our studies of selectively deuterlated and fluorine labelled dlhydrofolate reductase (3-12). The enzyme used In these studies was Isolated and purified from a methotrexate resistant strain of Lactobacillus easel as described by Dana and coworkers (19). This strain of L.easel Is auxotroplc for all the aromatic amino acids... 

When the polymeric backbone is susceptible to hydrolysis, drug release may eventually result following degradation of the carrier. Ryser and Shen have shown that methotrexate (MTX) covalently bound to poly(L-lysine) (one molecule of drug per 27 lysyl residues) is able to impair the growth of a normally methotrexate — resistant Chinese hamster ovary cell line MTX-poly(L-Lys) is regarded as a lysosomotropic... 

There are now known several cell culture systems in which variants selected as resistant to a particular inhibitor show elevated levels of the target enzyme(s), the most studied being that of methotrexate resistance which results in elevated levels of dihydrofolate reductase (4), To develop a similar system for ADA overproduction would require (a) a potent inhibitor of ADA activity and (b) growth conditions under which ADA activity was essential for cell survival. Deoxycoformycin (dCF), a specific inhibitor of ADA, has been described. This nucleoside analogue has a high affinity for ADA with a Ki of 10 10 - iq-IIm (5). ... 

Inhibition of thymidylate synthetase by tetrahydrohomofolic acid does not appear to be responsible for its activity against methotrexate-resistant mouse leukemias it may be acting by preventing the uptake of... 

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