The APC/C E3 Ligase Complex Activator FZR1 Restricts BRAF Oncogenic Function.
BRAF drives tumorigenesis by coordinating the activation of the RAS/RAF/MEK/ERK oncogenic signaling cascade. However, upstream pathways governing BRAF kinase activity and protein stability remain undefined. Here, we report that in primary cells with active APCFZR1, APCFZR1earmarks BRAF for ubiquitination-mediated proteolysis, whereas in cancer cells with APC-free FZR1, FZR1 suppresses BRAF through disrupting BRAF dimerization. Moreover, we identified FZR1 as a direct target of ERK and CYCLIN D1/CDK4 kinases. Phosphorylation of FZR1 inhibits APCFZR1, leading to elevation of a cohort of oncogenic APCFZR1substrates to facilitate melanomagenesis. Importantly, CDK4 and/or BRAF/MEK inhibitors restore APCFZR1E3 ligase activity, which might be critical for their clinical effects. Furthermore,FZR1depletion cooperates with AKT hyperactivation to transform primary melanocytes, whereas genetic ablation ofFzr1synergizes withPtenloss, leading to aberrant coactivation of BRAF/ERK and AKT signaling in mice. Our findings therefore reveal a reciprocal suppression mechanism between FZR1 and BRAF in controlling tumorigenesis.Significance:FZR1 inhibits BRAF oncogenic functions via both APC-dependent proteolysis and APC-independent disruption of BRAF dimers, whereas hyperactivated ERK and CDK4 reciprocally suppress APCFZR1E3 ligase activity. Aberrancies in this newly defined signaling network might account for BRAF hyperactivation in human cancers, suggesting that targeting CYCLIN D1/CDK4, alone or in combination with BRAF/MEK inhibition, can be an effective anti-melanoma therapy.Cancer Discov; 7(4); 424-41. ©2017 AACR.See related commentary by Zhang and Bollag, p. 356This article is highlighted in the In This Issue feature, p. 339.
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. wwei2@bidmc.harvard.edu lixin.wan@moffitt.org caojuxi@gmail.com rutaocui@bu.edu ppandolf@bidmc.harvard.edu.|Department of Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida.
Lixin
L
Wan
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Ming
M
Chen
Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts. wwei2@bidmc.harvard.edu lixin.wan@moffitt.org caojuxi@gmail.com rutaocui@bu.edu ppandolf@bidmc.harvard.edu.
Juxiang
J
Cao
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Xiangpeng
X
Dai
Department of Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida.
Qing
Q
Yin
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Jinfang
J
Zhang
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Su-Jung
SJ
Song
Department of Systems Biology, Harvard Medical School, Boston, Massachusetts.
Ying
Y
Lu
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.|Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology and Frontier Institute of Life Science, FIST, Xi'an Jiaotong University, Xi'an 710049, P.R. China.
Jing
J
Liu
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Hiroyuki
H
Inuzuka
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Jesse M
JM
Katon
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Kelsey
K
Berry
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Jacqueline
J
Fung
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Christopher
C
Ng
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Pengda
P
Liu
Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Min Sup
MS
Song
Department of Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida.
Lian
L
Xue
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts.
Roderick T
RT
Bronson
Department of Systems Biology, Harvard Medical School, Boston, Massachusetts.
Marc W
MW
Kirschner
Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts. wwei2@bidmc.harvard.edu lixin.wan@moffitt.org caojuxi@gmail.com rutaocui@bu.edu ppandolf@bidmc.harvard.edu.
Rutao
R
Cui
Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. wwei2@bidmc.harvard.edu lixin.wan@moffitt.org caojuxi@gmail.com rutaocui@bu.edu ppandolf@bidmc.harvard.edu.
Pier Paolo
PP
Pandolfi
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. wwei2@bidmc.harvard.edu lixin.wan@moffitt.org caojuxi@gmail.com rutaocui@bu.edu ppandolf@bidmc.harvard.edu.
Wenyi
W
Wei
D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D063646:Carcinogenesis / Q000235:genetics; D064200:Cdh1 Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000235:genetics; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics; D010766:Phosphorylation / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
C555337:APC protein, human; D025601:Adenomatous Polyposis Coli Protein; D064200:Cdh1 Proteins; C577584:FZR1 protein, human; D046912:Multiprotein Complexes; D047428:Protein Kinase Inhibitors; D019938:Cyclin D1; D044767:Ubiquitin-Protein Ligases; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf