The Transsulfuration Pathway Makes, the Tumor Takes.

Cells can take up cysteine or synthesize it de novo from methionine, but synthesis alone does not meet the high demands of cancer cells to proliferate. In this issue, Zhu et al. (2019) identify the SAH:SAM ratio, indicative of the cellular methylation state, as limiting for effective cysteine synthesis and the growth of some tumors.