Two newly synthesized 5-methyltetrahydrofolate-like compounds inhibit methionine synthase activity accompanied by cell cycle arrest in G1/S phase and apoptosis in vitro.
Cobalamin-dependent methionine synthase, with a cofactor of vitamin B12, catalyzes the reaction of 5-methyltetrahydrofolate and homocysteine to form methionine and tetrahydrofolate, which takes a core position in folate cycle, one-carbon-unit transfer, and sulfur amino acid pathways. The 'methyl folate trap' hypothesis suggests that methionine synthase is a potential target for anticancer drug development. ZL031 and ZL033 are 5-methyltetrahydrofolate-like compounds that have been newly synthesized as potential inhibitors of the enzyme. To identify the effect of these two compounds on methionine synthase activity, a spectrophotometric assay was used and the results proved that ZL031 and ZL033 inactivated methionine synthase in HL-60 cells with an IC50 dose of 10.0 and 1.4 mumol/l, respectively. Moreover, obvious inhibitory effect on proliferation of HL-60 cells was observed, leading to our further investigation of the underlying anticancer mechanism. Under the circumstances of methionine synthase deficiency and subsequent folate depletion, cell cycle was arrested in G1/S phase and apoptosis was also observed. Analysis of cell cycle regulatory proteins demonstrated that cyclin E and cyclin-dependent kinase 2 were both increased. Furthermore, reduction of caspase-3, poly (ADP-ribose) polymerase, caspase-8, and caspase-9 protein levels were observed. In all the biological experiments we have performed, ZL033 has shown a better efficacy compared with ZL031. These results suggest that ZL031 and ZL033, as novel methionine synthase inhibitors, caused G1/S phase delay and apoptosis and eventually inhibit the proliferation of HL-60 cells in vitro. ZL033, with a carboxylic acid substituent, might have a better potential for drug development than ZL031 with an ester substituent.
Tang
Cai
C
State Key Laboratory of Natural and Biomimetic Drugs, Peking University Health Science Center, Beijing, PR China.
Zhang
Zhili
Z
Xu
Bo
B
Li
Min
M
Liu
Junyi
J
Cui
Jingrong
J
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000037:antagonists & inhibitors*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D019927:Cyclin E / Q000096:biosynthesis; D051357:Cyclin-Dependent Kinase 2 / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects*; D005971:Glutamates / Q000494:pharmacology*; D018922:HL-60 Cells; D006801:Humans; D011743:Pyrimidines / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects*; D013763:Tetrahydrofolates / Q000494:pharmacology
D000970:Antineoplastic Agents; D019927:Cyclin E; D004791:Enzyme Inhibitors; D005971:Glutamates; C531187:N-(4-((2-(2,4-diamino-5-(2,3-dibromopropyl)-5,6,7,8-tetrahydropyrido(3,2-d)pyrimidin-6-yl)methyl)amino)-3-bromobenzoyl)glutamic acid; D011743:Pyrimidines; D013763:Tetrahydrofolates; C531186:diethyl N-(4-((2-(2,4-diamino-5-(2,3-dibromopropyl)-5,6,7,8-tetrahydropyrido(3,2-d)pyrimidin-6-yl)methyl)amino)-3-bromobenzoyl)glutamate; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; C005984:5-methyltetrahydrofolate