Ferrarone, J.; Thomas, J.; Unni, A.; Zheng, Y.; Nagiec, M.; Gardner, E.; Mashadova, O.; Li, K.; Koundouros, N.; Montalbano, A.; Mustafa, M.; Cantley, L.; Blenis, J.; Sanjana, N.; Varmus, H.

The tumor suppressor LKB1 is a serine/threonine protein kinase that is frequently mutated in human lung adenocarcinoma (LUAD). LKB1 regulates a complex signaling network that is known to control cell polarity and metabolism; however, the pathways that mediate the tumor suppressive activity of LKB1 are incompletely defined. To identify mechanisms of LKB1-mediated growth suppression we developed a spheroid-based cell culture assay to study LKB1-dependent growth. Using this assay, along with genome-wide CRISPR screens and validation with orthogonal methods, we discovered that LKB1 suppresses growth, in part, by activating the PIKFYVE lipid kinase, which promotes the internalization of wild-type EGFR. Our findings reveal a new mechanism of regulation of EGFR, which may have implications for the treatment of LKB1-mutant LUAD.