FBXW7 mutations in melanoma and a new therapeutic paradigm.
BACKGROUND
Melanoma is a heterogeneous tumor with subgroups requiring distinct therapeutic strategies. Genetic dissection of melanoma subgroups and identification of therapeutic agents are of great interest in the field. These efforts will ultimately lead to treatment strategies, likely combinatorial, based on genetic information.


METHODS
To identify "driver" genes that can be targeted therapeutically, we screened metastatic melanomas for somatic mutations by exome sequencing followed by selecting those with available targeted therapies directed to the gene product or its functional partner. The FBXW7 gene and its substrate NOTCH1 were identified and further examined. Mutation profiling of FBXW7, biological relevance of these mutations and its inactivation, and pharmacological inhibition of NOTCH1 were examined using in vitro and in vivo assays.


RESULTS
We found FBXW7 to be mutated in eight (8.1%) melanoma patients in our cohort (n = 103). Protein expression analysis in human tissue samples (n = 96) and melanoma cell lines (n = 20) showed FBXW7 inactivation as a common event in melanoma (40.0% of cell lines). As a result of FBXW7 loss, we observed an accumulation of its substrates, such as NOTCH1. Ectopic expression of mutant forms of FBXW7 (by 2.4-fold), as well as silencing of FBXW7 in immortalized melanocytes, accelerated tumor formation in vivo (by 3.9-fold). Its inactivation led to NOTCH1 activation, upregulation of NOTCH1 target genes (by 2.6-fold), and promotion of tumor angiogenesis and resulted in tumor shrinkage upon NOTCH1 inhibition (by fivefold).


CONCLUSIONS
Our data provides evidence on FBXW7 as a critical tumor suppressor mutated and inactivated in melanoma that results in sustained NOTCH1 activation and renders NOTCH signaling inhibition as a promising therapeutic strategy in this setting.
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Iraz T
IT
Aydin
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Rachel D
RD
Melamed
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Sarah J
SJ
Adams
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Mireia
M
Castillo-Martin
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Ahu
A
Demir
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Diana
D
Bryk
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Georg
G
Brunner
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Carlos
C
Cordon-Cardo
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO).
Iman
I
Osman
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO). julide.celebi@mountsinai.org rabadan@dbmi.columbia.edu.
Raul
R
Rabadan
Affiliations of authors: Department of Dermatology (ITY, SJA, AD, DB, JTC) and Department of Pathology (ITA, SJA, MC-M, AD, DB, CC-C, JTC), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Biomedical Informatics (RDM, RR) and Department of Systems Biology (RDM, RR), Columbia University Medical Center, New York, NY; Department of Cancer Research, Skin Cancer Center Hornheide, Munster, Germany (GB); Department of Dermatology, New York University, New York, NY (IO). julide.celebi@mountsinai.org rabadan@dbmi.columbia.edu.
Julide Tok
JT
Celebi
D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D044783:F-Box Proteins / Q000235:genetics*; D000073979:F-Box-WD Repeat-Containing Protein 7; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000235:genetics*; D009154:Mutation; D060888:Real-Time Polymerase Chain Reaction; D051881:Receptor, Notch1 / Q000235:genetics*; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*
D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; C497761:NOTCH1 protein, human; D051881:Receptor, Notch1; D044767:Ubiquitin-Protein Ligases