Oncogenic PKA signaling increases c-MYC protein expression through multiple targetable mechanisms
Gary K.L. Chan, Samantha Maisel, Yeonjoo Hwang, Bryan C Pascual, Rebecca RB Wolber, Phuong Vu, Krushna C. Patra, Mehdi Bouhaddou, Heidi L. Kenerson, Huat Chye Lim, Donald Long, Raymond S. Yeung, Praveen Sethupathy, Danielle L. Swaney, Nevan J. Krogan, Rigney E. Turnham, Kimberly J. Riehle, John D. Scott, Nabeel Bardeesy, John D. Gordan
Abstract
Genetic alterations that activate protein kinase A (PKA) are found in many tumor types. Yet, their downstream oncogenic signaling mechanisms are poorly understood. We used global phosphoproteomics and kinase activity profiling to map conserved signaling outputs driven by a range of genetic changes that activate PKA in human cancer. Two signaling networks were identified downstream of PKA: RAS/MAPK components and an Aurora Kinase A (AURKA)/glycogen synthase kinase (GSK3) sub-network with activity toward MYC oncoproteins. Findings were validated in two PKA-dependent cancer models: a novel, patient-derived fibrolamellar carcinoma (FLC) line that expresses a DNAJ-PKAc fusion and a PKA-addicted melanoma model with a mutant type I PKA regulatory subunit. We identify PKA signals that can influence both de novo translation and stability of the proto-oncogene c-MYC. However, the primary mechanism of PKA effects on MYC in our cell models was translation and could be blocked with the eIF4A inhibitor zotatifin. This compound dramatically reduced c-MYC expression and inhibited FLC cell line growth in vitro. Thus, targeting PKA effects on translation is a potential treatment strategy for FLC and other PKA-driven cancers.