Hoffman R M
Anticancer Res. 1985 Jan-Feb;5(1):1-30.
Methionine metabolism and transmethylation are frequently altered in cancer cells. The alteration is often expressed as an inability of the cancer cells to grow when methionine is replaced by homocysteine in the culture medium, a condition that allows the growth of normal cells. This metabolic defect is termed methionine dependence. Methionine dependence may reflect an overall imbalance in transmethylation which results in the overmethylation of some substances and undermethylation of others within cancer cells. Many carcinogens affect various stages of methionine/transmethylation metabolism. The ultimate effect of the alteration of methionine/transmethylation metabolism may be the disruption of the regulation of genes involved in the oncogenic process. The known protective effect of methionine against cancer may be due to prevention of altered methionine/transmethylation metabolism or compensation of the altered metabolism.
甲硫氨酸代谢和转甲基作用在癌细胞中常常发生改变。这种改变通常表现为当培养基中的甲硫氨酸被同型半胱氨酸替代时，癌细胞无法生长，而这种条件却能使正常细胞生长。这种代谢缺陷被称为甲硫氨酸依赖性。甲硫氨酸依赖性可能反映了转甲基作用的整体失衡，这导致癌细胞内某些物质过度甲基化而另一些物质甲基化不足。许多致癌物会影响甲硫氨酸/转甲基代谢的各个阶段。甲硫氨酸/转甲基代谢改变的最终影响可能是破坏参与致癌过程的基因调控。甲硫氨酸对癌症的已知保护作用可能是由于预防了甲硫氨酸/转甲基代谢的改变或补偿了改变的代谢。
