Protective autophagy elicited by RAF→MEK→ERK inhibition suggests a treatment strategy for RAS-driven cancers
Conan G Kinsey, Soledad A Camolotto, Amelie M Boespflug, Katrin P Guillen, Mona Foth, Amanda Truong, Sophia S Schuman, Jill E Shea, Michael T Seipp, Jeffrey T Yap, Lance D Burrell, David H Lum, Jonathan R Whisenant, G Weldon Gilcrease 3rd, Courtney C Cavalieri, Kaitrin M Rehbein, Stephanie L Cutler, Kajsa E Affolter, Alana L Welm, Bryan E Welm, Courtney L Scaife, Eric L Snyder, Martin McMahon, Conan G Kinsey, Soledad A Camolotto, Amelie M Boespflug, Katrin P Guillen, Mona Foth, Amanda Truong, Sophia S Schuman, Jill E Shea, Michael T Seipp, Jeffrey T Yap, Lance D Burrell, David H Lum, Jonathan R Whisenant, G Weldon Gilcrease 3rd, Courtney C Cavalieri, Kaitrin M Rehbein, Stephanie L Cutler, Kajsa E Affolter, Alana L Welm, Bryan E Welm, Courtney L Scaife, Eric L Snyder, Martin McMahon
Abstract
Pancreatic ductal adenocarcinoma (PDA) was responsible for ~ 44,000 deaths in the United States in 2018 and is the epitome of a recalcitrant cancer driven by a pharmacologically intractable oncoprotein, KRAS1-4. Downstream of KRAS, the RAF→MEK→ERK signaling pathway plays a central role in pancreatic carcinogenesis5. However, paradoxically, inhibition of this pathway has provided no clinical benefit to patients with PDA6. Here we show that inhibition of KRAS→RAF→MEK→ERK signaling elicits autophagy, a process of cellular recycling that protects PDA cells from the cytotoxic effects of KRAS pathway inhibition. Mechanistically, inhibition of MEK1/2 leads to activation of the LKB1→AMPK→ULK1 signaling axis, a key regulator of autophagy. Furthermore, combined inhibition of MEK1/2 plus autophagy displays synergistic anti-proliferative effects against PDA cell lines in vitro and promotes regression of xenografted patient-derived PDA tumors in mice. The observed effect of combination trametinib plus chloroquine was not restricted to PDA as other tumors, including patient-derived xenografts (PDX) of NRAS-mutated melanoma and BRAF-mutated colorectal cancer displayed similar responses. Finally, treatment of a patient with PDA with the combination of trametinib plus hydroxychloroquine resulted in a partial, but nonetheless striking disease response. These data suggest that this combination therapy may represent a novel strategy to target RAS-driven cancers.
Conflict of interest statement
Competing Interests Statement:
Dr. McMahon served on external advisory boards for Novartis (June 2017), Genentech (December 2017) and Merck (June 2018). Dr. McMahon is the recipient of research funding from Pfizer, through a grant peer-reviewed, co-funded and awarded by the Melanoma Research Alliance.
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References
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Source: PubMed