S-adenosyl-L-homocysteine: a non-cytotoxic hypomethylating agent.

The cytotoxic effect caused by the hypomethylating agent S-adenosyl-L- homocysteine (SAH) was compared with that of two drugs commonly used to induce DNA hypomethylation, 5-azacytidine and 5-aza-2'-deoxycytidine. Two in vitro cytotoxicity tests, the tetrazolium MTT assay and the intracellular lactate dehydrogenase (LDH) activity test, suggest that SAH induces hypomethylation without causing any cytotoxic effect. We propose the use of SAH as a non-cytotoxic agent which may be more suitable for inducing experimental DNA hypomethylation.