Kinase experiment:

AICARFT inhibition assays are carried out at room temperature by monitoring the formation of [6S]-5,6,7,8-tetrahydrofolate from 10-formyl-[6R,S]-5,6,7,8-tetrahydrofolate at A298. All solutions are purged with N2 gas prior to use. The reaction solution contains 33 mM Tris-Cl, pH 7.4, 25 mM KCl, 5 mM 2-Mercaptoethanol, 0.05 mM AICA ribonucleotide, and 16 nM (2 milliunits/mL) of AICARFT. 10-Formyl-[6R,S]-5,6,7,8-tetrahydrofolate concentrations of 0.037, 0.074, and 0.145 mM are used (0.61, 1.23, and 2.45 times its Km value, respectively). LY231514 is tested as an inhibitor at 0.08-0.8 mM (four concentrations). When the tri- and pentaglutamates of LY231514 are used as inhibitors, the concentrations are 0.0005-0.009 mM (eight concentrations). Enzyme assays are initiated by the addition of enzyme. Data is analyzed using the ENZFITTER program for competitive inhibition.

Cell experiment:

Dose-response curves are generated to determine the concentration required for 50% inhibition of growth (IC50). Pemetrexed is dissolved initially in DMSO at a concentration of 4 mg/mL and further diluted with cell culture medium to the desired concentration. CCRF-CEM leukemia cells in complete medium are added to 24-well Cluster plates at a final concentration of 4.8×104 cells/well in a total volume of 2 mL. Test compounds at various concentrations are added to duplicate wells so that the final volume of DMSO is 0.5%. The plates are incubated for 72 h at 37℃ in an atmosphere of 5% CO2 in air. At the end of the incubation, cell numbers are determined on a ZBI Coulter counter. Control wells usually contain 4×105 to 6×105 cells at the end of the incubation. For several studies, IC50s are determined for each compound in the presence of either 300 μM AICA, 5 μM thymidine, 100 μM hypoxanthine, or combination of 5 μM hymidine plus 100 μM hypoxanthine[1].

Animal experiment:

Mice[2] Female CBA mice and female NOD/SCID mice (NOD.CB17-Prkdcscid) at 6-8 wk of age are used. Premetrexed (100 mg/kg) is given i.p. from days 4-8 (5 consecutive d) to tumor-bearing mice to explore the synergistic effect when combined with anti-CD25 Ab or IgG control. The dose and schedule used for Pemetrexed in the current study is determined based on previous studies in mice.

Pemetrexed (also known as pemetrexed disodium) is a novel antifolate antimetabolite targeting multiple enzymes involved in both pyrimidine and purine synthesis. Pemetrexed is an analog of the classic antifolate GARFYT inhibitor lometroxol with a similar chemical structure, where the pyrazine ring in the pterine portion of folic acid and the benzylic nitrogen in the bridge portion of folic acid are replaced by a pyrrole ring and a methylene group respectively. Pemetrexed potently inhibits TS, DHFR, and GARFT as well as AICARFT but with a lesser potency and exhibits autitumor activity in a broad range of tumors, including non-small cell lung carcinoma, malignant mesothelioma, and carcinomas of the breast, colorectum, uterine cervix, head and neck, and bladder.

Reference

[1].Luis Paz-Ares, Susana Bezares, Jose M. Tabernero, Daniel Castellanos, and Hernan Cortes-Funes. Review of a promising new agent-pemetrexed disodium. Cancer 2003; 97(8 Suppl):2056-2063