p53 suppresses lipid droplet-fueled tumorigenesis through phosphatidylcholine

Choline deficiency causes disorders including hepatic abnormalities and is associated with an increased risk of multiple types of cancer(1, 2). Here, by choline free diet-associated RNAseq analyses, we found that the tumor suppressor p53 drives the Kennedy pathway via PCYT1B to control the growth of lipid droplets (LDs) and their fueling role in tumorigenesis. Mechanistically, through upregulation of PCYT1B, p53 channeled depleted choline stores to phosphatidylcholine (PC) biosynthesis during choline starvation, thus preventing LD coalescence. Cells lacking p53 failed to complete this response to choline depletion, leading to hepatic steatosis and tumorigenesis, and these effects could be reversed by enforcing PCYT1B expression or restoring PC abundance. Furthermore, loss of p53 or defects in the Kennedy pathway increased surface localization of hormone-sensitive lipase (HSL) on LDs to release specific fatty acids that fueled tumor cells in vivo and in vitro. Thus, p53 loss leads to dysregulation of choline metabolism and LD growth, and couples perturbed LD homeostasis to tumorigenesis.