2-Amino-<i>O</i><sup>4</sup>-benzylpteridine Derivatives: Potent Inactivators of <i>O</i><sup>6</sup>-Alkylguanine-DNA Alkyltransferase
作者:Michael E. Nelson、Natalia A. Loktionova、Anthony E. Pegg、Robert C. Moschel
DOI:10.1021/jm049758+
日期:2004.7.1
2-Amino-O-4-benzylpteridine (1), 2-amino-O-4-benzyl-6,7-dimethylpteridine (2), 2-amino-O-4- benzyl-6-hydroxymethylpteridine (4), 2-amino-O-4-benzylpteridine-6-carboxylic acid (5), 2-amino-O-4-benzyl-6-formylpteridine (6), and O-4-benzylfolic acid (7) are shown to be as potent or more potent inactivators of the human DNA repair protein O-6-alkylguanine-DNA alkyltransferase (alkyltransferase) in vitro than O-6-benzylguanine, the prototype alkyltransferase inactivator currently in clinical trials. Additionally, the negatively charged (at physiological pH) inactivators 2-amino-O-4-benzylpteridine-6-carboxylic acid (5) and O-4-benzylfolate (7) are far more water soluble than O-6-benzylguanine. The activity of O-4-benzylfolic acid (7) is particularly noteworthy because it is roughly 30 times more active than O-6-benzylguanine against the wild-type alkyltransferase and is even capable of inactivating the P140K mutant alkyltransferase that is resistant to inactivation by O-6-benzylguanine. All the pteridine derivatives except 2-amino-O-4-benzylpteridine-6-carboxylic acid are effective in enhancing cell killing by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). However, the effectiveness of O-4-benzylfolate as an adjuvant for cell killing by BCNU appears to be a function of a cell's alpha-folate receptor expression. Thus, O-4-benzylfolate is least effective as an adjuvant in A549 cells (which express little if any receptor), is moderately effective in HT29 cells (which express low levels of the receptor), but is very effective in KB cells (which are known to express high levels of the alpha-folate receptor). Therefore, O-4-benzylfolic acid shows promise as an agent for possible tumor-selective alkyltransferase inactivation, which suggests it may prove to be superior to O-6-benzylguanine as a chemotherapy adjuvant.