Carrier-mediated transport of folate compounds in L1210 cells. Initial rate kinetics and extent of duality of entry routes for folic acid and diastereomers of 5-methyltetrahydrohomofolate in the presence of physiological anions.

Comparison of the kinetic parameters for influx of highly purified [3H]folic acid versus [3H]methotrexate in L1210 cells under anionic buffer conditions showed a marked discordancy. In addition, the kinetics for influx of [3H]folic acid were unchanged in variant L1210 cells defective in [3H]methotrexate transport. In these variant cells, the Vmax for methotrexate was reduced 17-fold and the Km was increased 3-fold.

Hydrolytic cleavage of methotrexate gamma-polyglutamates by folylpolyglutamyl hydrolase derived from various tumors and normal tissues of the mouse.

Folylpolyglutamate hydrolase (folyl hydrolase) activity derived from murine tumors and various normal tissues was measured by means of high performance liquid chromatography using methotrexate polyglutamates as substrate. Enzyme-mediated hydrolysis was considerably greater (10-20-fold) on a specific activity basis in extracts from all normal mouse tissues (kidney greater than bone marrow greater than small intestine approximately equal to liver) than from tumor cells (Sarcoma 180 greater than Ehrlich approximately equal to L1210 cells). Enzyme preparations from purified absorptive and crypt cell epithelium from mouse small intestine exhibited comparable levels of specific activity and were greater than that derived from the total organ.

Extent of the requirement for folate transport by L1210 cells for growth and leukemogenesis in vivo.

In these studies the extent of the requirement for 5-methyltetrahydrofolate by L1210 cells for growth and leukemogenesis in vivo was addressed from the aspect of its cellular membrane transport. Growth characteristics and leukemogenesis in vivo were determined for parental and methotrexate-resistant L1210 cell variants with reduced capacity for folate coenzyme transport inward. These variants exhibited 6-, 16-, and 100-fold reductions compared to parental cells in influx Vmax for the high-affinity system transporting 5-substituted reduced folates and methotrexate.

New folate analogs of the 10-deaza-aminopterin series. Further evidence for markedly increased antitumor efficacy compared with methotrexate in ascitic and solid murine tumor models.

A group of folate analogs of the 10-deaza-aminopterin series, which were designed on the basis of the results of an intensive biochemical and pharmacokinetic program, have been examined in therapy experiments utilizing a group of murine tumor models. These new analogs were found to be markedly superior to methotrexate against four of five ascites tumors (L1210 leukemia, Sarcoma 180, Ehrlich carcinoma and Tapper carcinosarcoma) and against four of five solid tumors (S180, Tapper carcinosarcoma, E0771 mammary adenocarcinoma, Lewis lung carcinoma, and T241 sarcoma). Analogs alkylated (methyl or ethyl) at the 10 position of 10-deaza-aminopterin were found to be the most effective of the group.

New folate analogs of the 10-deaza-aminopterin series. Basis for structural design and biochemical and pharmacologic properties.

Structural modification of the N10 position of 4-amino folates affects mediated membrane transport in mammalian cells but has little or no effect on target enzyme (dihydrofolate reductase) inhibition. Some of these modifications have been associated with differential effects on transport in various cell types in a manner which favored greater accumulation and persistence of drug in responsive tumor cells than in normal proliferative tissue. With the aid of identifying new structures with greater potential for differential mediated accumulation, we have studied three new 10-alkyl analogs of 10-deaza-aminopterin.