title: Increased cyclin D1 expression can mediate BRAF inhibitor resistance in BRAF V600E-mutated melanomas.
abstract: Recent studies have shown that there is a considerable heterogeneity in the response of melanoma cell lines to MEK and BRAF inhibitors. In the current study, we address whether dysregulation of cyclin-dependent kinase 4 (CDK4) and/or cyclin D1 contribute to the BRAF inhibitor resistance of melanoma cells. Mutational screening identified a panel of melanoma cell lines that harbored both a BRAF V600E mutation and a CDK4 mutation: K22Q (1205Lu), R24C (WM39, WM46, and SK-Mel-28), and R24L (WM902B). Pharmacologic studies showed that the presence of a CDK4 mutation did not alter the sensitivity of these cell lines to the BRAF inhibitor. The only cell line with significant BRAF inhibitor resistance was found to harbor both a CDK4 mutation and a CCND1 amplification. Array comparative genomic hybridization analysis showed that CCND1 was amplified in 17% of BRAF V600E-mutated human metastatic melanoma samples, indicating the clinical relevance of this finding. As the levels of CCND1 amplification in cell lines are lower than those seen in clinical specimens, we overexpressed cyclin D1 alone and in the presence of CDK4 in a drug-sensitive melanoma line. Cyclin D1 overexpression alone increased resistance and this was enhanced when cyclin D1 and CDK4 were concurrently overexpressed. In conclusion, increased levels of cyclin D1, resulting from genomic amplification, may contribute to the BRAF inhibitor resistance of BRAF V600E-mutated melanomas, particularly when found in the context of a CDK4 mutation/overexpression.
authors.affiliation: The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA. k.smalley@mac.com
authors.forename: Keiran S M
authors.initials: KS
authors.lastname: Smalley
authors.forename: Mercedes
authors.initials: M
authors.lastname: Lioni
authors.forename: Maurizia
authors.initials: M
authors.lastname: Dalla Palma
authors.forename: Min
authors.initials: M
authors.lastname: Xiao
authors.forename: Brijal
authors.initials: B
authors.lastname: Desai
authors.forename: Suzanne
authors.initials: S
authors.lastname: Egyhazi
authors.forename: Johan
authors.initials: J
authors.lastname: Hansson
authors.forename: Hong
authors.initials: H
authors.lastname: Wu
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: King
authors.forename: Patricia
authors.initials: P
authors.lastname: Van Belle
authors.forename: David E
authors.initials: DE
authors.lastname: Elder
authors.forename: Keith T
authors.initials: KT
authors.lastname: Flaherty
authors.forename: Meenhard
authors.initials: M
authors.lastname: Herlyn
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Nathanson
mesh_terms: D019943:Amino Acid Substitution / Q000187:drug effects; D001483:Base Sequence; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D051358:Cyclin-Dependent Kinase 4 / Q000235:genetics; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005784:Gene Amplification / Q000187:drug effects; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000235:genetics*; D014633:Valine / Q000235:genetics
chemical_list: D007093:Imidazoles; C508204:SB-590885; D019938:Cyclin D1; D018698:Glutamic Acid; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051358:Cyclin-Dependent Kinase 4; D014633:Valine
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