Evidence of inhibition of DNA methylation by fludarabine.

Abstract

Fludarabine (9-β -D-arabinosyl-2-fluoroadenine) is a synthetic adenine nucleoside analogue which is used for treatment of chronic lymphocytic leukaemia1. A postulated mechanism of fludarabine activity is incorporation of its phosphate derivative into elongating nucleic acid chains. This process leads to termination of DNA and RNA synthesis1. Our previous in vitro studies on the inhibitors of S-adenosylhomocysteine (SAH) hydrolase showed that fludarabine was a potent inactivator of SAH hydrolase 2, . We also documented that the activity of endogenous C-5 DNA methyltransferase in murine leukemic cell line, L1210, was inhibited during 72 hr growth of cells in the presence of fludarabine at 10 μM concentration (unpublished data). It was pointed out by other authors that compounds which inhibit SAH hydrolase activity probably induce, by cellular rise of SAH, inhibition of DNA methylation 4 which is very important for gene expression and differentation of cells. Up till now, however, there has been poor evidence of DNA methylation level decrease by SAH hydrolase inhibitors. The present studies were designed to estimate: 1/ cytotoxicity of fludarabine and viability of L1210 cells during 72 hr growth in the presence of the drug at different concentration, 2/ influence of fludarabine and 5-aza-2’-deoxycytidine (5-aza-dCyt, potent inhibitor of C-5 DNA