Heterogeneity in Mitogen-Activated Protein Kinase (MAPK) Pathway Activation in Uveal Melanoma With Somatic GNAQ and GNA11 Mutations

• Published in: Investigative ophthalmology & visual science 2019-06, Vol.60 (7), p.2474-2480
• Main Authors: Boru, Getachew, Cebulla, Colleen M, Sample, Klarke M, Massengill, James B, Davidorf, Frederick H, Abdel-Rahman, Mohamed H
• Format: Article
• Language: English
• Subjects: Anatomy and Pathology/Oncology; Blotting, Western; Cell Line, Tumor; Cohort Studies; DNA Mutational Analysis; GTP-Binding Protein alpha Subunits - genetics; GTP-Binding Protein alpha Subunits, Gq-G11 - genetics; Humans; Immunohistochemistry; Melanoma - enzymology; Melanoma - genetics; Mitogen-Activated Protein Kinases - metabolism; Mutation; Plasmids; Polymorphism, Restriction Fragment Length; Sequence Analysis, DNA; Signal Transduction; Transfection; Uveal Neoplasms - enzymology; Uveal Neoplasms - genetics
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.18-26452

The activation of the mitogen-activated protein kinase (MAPK) pathway has been suggested as the major downstream target when GNAQ and GNA11 (GNAQ/11) are mutated in uveal melanoma (UM). However, clinical trials with single agent MEK inhibitor showed no clinical significance in altering the overall outcome of the disease in UM; therefore, we investigated the correlation between naturally occurring mutations in GNAQ/11 and activation of MAPK pathway in vivo in primary UM. Screening for activating mutations in codons 183 and 209 of GNAQ/11 was carried out by sequencing and restriction fragment length polymorphism (RFLP) in a cohort of 42 primary UM. Activation of the MAPK pathway and other potential downstream signals was assessed by immunohistochemistry and/or Western blot analysis. Potential downstream signaling of mutant and wild type GNAQ/11 was studied by transient transfection assay in nonmutant cell lines. Somatic mutations in GNAQ/11 were observed in 35/42 (83.3%) of primary UM. Tumors with GNAQ/11 mutations showed variations in the activation of ERK1/2 with significant tumor heterogeneity. Weak and undetectable ERK1/2 activation was observed in 4/35 (11.4%) and 8/35 (22.9%) of the GNAQ/11 mutant UM, respectively. Tumor heterogeneity of GNAQ/11 mutations was also observed in a subset of tumors. Our results indicate that there is marked variation in MAPK activation in UM with GNAQ/11 mutations. Thus, GNAQ/11 mutational status is not a sufficient biomarker to adequately predict UM patient responses to single-agent selective MEK inhibitor therapy.