Kinase-independent role for CRAF-driving tumour radioresistance via CHK2.
Although oncology therapy regimens commonly include radiation and genotoxic drugs, tumour cells typically develop resistance to these interventions. Here we report that treatment of tumours with ionizing radiation or genotoxic drugs drives p21-activated kinase 1 (PAK1)-mediated phosphorylation of CRAF on Serine 338 (pS338) triggering a kinase-independent mechanism of DNA repair and therapeutic resistance. CRAF pS338 recruits CHK2, a cell cycle checkpoint kinase involved in DNA repair, and promotes CHK2 phosphorylation/activation to enhance the tumour cell DNA damage response. Accordingly, a phospho-mimetic mutant of CRAF (S338D) is sufficient to induce the CRAF/CHK2 association enhancing tumour radioresistance, while an allosteric CRAF inhibitor sensitizes tumour cells to ionizing radiation or genotoxic drugs. Our findings establish a role for CRAF in the DNA damage response that is independent from its canonical function as a kinase.
Department of Radiation Medicine and Applied Sciences at the UC San Diego Moores Cancer Center, University of California, San Diego, La Jolla, California 92093, USA.
Sunil J
SJ
Advani
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Maria Fernanda
MF
Camargo
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Laetitia
L
Seguin
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Ainhoa
A
Mielgo
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Sudarshan
S
Anand
Department of Radiation Medicine and Applied Sciences at the UC San Diego Moores Cancer Center, University of California, San Diego, La Jolla, California 92093, USA.
Angel M
AM
Hicks
Department of Radiation Medicine and Applied Sciences at the UC San Diego Moores Cancer Center, University of California, San Diego, La Jolla, California 92093, USA.
Joseph
J
Aguilera
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Aleksandra
A
Franovic
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
Sara M
SM
Weis
Department of Pathology at the UC San Diego Moores Cancer Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, 3855 Health Science Drive, La Jolla, California 92037, USA.
David A
DA
Cheresh
D000818:Animals; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2 / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage / Q000235:genetics / Q000528:radiation effects*; D005455:Fluorescent Antibody Technique; D045325:HCT116 Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051379:Mice; D009154:Mutation; D009368:Neoplasm Transplantation; D010766:Phosphorylation / Q000528:radiation effects; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000528:radiation effects*; D011836:Radiation Tolerance / Q000235:genetics*; D011839:Radiation, Ionizing; D012694:Serine / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D054462:p21-Activated Kinases / Q000235:genetics / Q000528:radiation effects*
D012694:Serine; D064447:Checkpoint Kinase 2; C482119:BRAF protein, human; C578634:CHEK2 protein, human; C515903:PAK1 protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D054462:p21-Activated Kinases