title: Methotrexate (MTX) concentration in tumors following low-dose MTX.
abstract: Methotrexate (MTX) is a folate analog competitive with reduced folates for cellular transport and metabolism. Since the normal plasma folate concentration is only 10(-8) M, we tested the possibility that there may be a saturable uptake of MTX by proliferating tumor tissue at plasma MTX concentrations of only 10(-7) to 10(-6) M. Patients with advanced malignancies, refractory to accepted therapy, were given low-dose oral MTX (30-60 mg/m2 total dose in four to eight divided doses). Tumor tissue was biopsied 18-24 h after the last oral dose of MTX. The concentrations of MTX and its polyglutamated derivatives were measured in these samples. Forty-eight percent of the drug in the tumor samples was present as a polyglutamated derivative.
mesh_terms: D000284:Administration, Oral; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008727:Methotrexate / Q000032:analysis / Q000378:metabolism*; D009369:Neoplasms / Q000032:analysis / Q000378:metabolism*; D011099:Polyglutamic Acid / Q000032:analysis / Q000378:metabolism; D011869:Radioligand Assay
chemical_list: D011099:Polyglutamic Acid; D008727:Methotrexate