Cancer Therapy : Preclinical Identi fi cation of Unique MEK-Dependent Genes in GNAQ Mutant Uveal Melanoma Involved in Cell Growth , Tumor Cell Invasion , and MEK Resistance

Purpose: Metastatic uveal melanoma represents the most common intraocular malignancy with very poor prognosis and no effective treatments. Oncogenicmutations in the G-proteina-subunit q and 11 have been described in about 85% of uveal melanomas and confer constitutive activation. Multiple signaling pathways are induced as a consequence of GNAQ/11 activation, which include the MEK/ERK kinase cascade.We analyzed the transcriptional profile of cell lines treatedwith amitogen-activated protein (MAP)/ extracellular signal–regulated (ERK) kinase (MEK) inhibitor to identify gene targets of activated GNAQ and to evaluate the biologic importance of these genes in uveal melanoma. Experimental Design: We conducted microarray analysis of uveal melanoma cell lines with GNAQ mutations treated with the MEK inhibitor selumetinib. For comparison, we used cells carrying BRAF and cells without either mutation. Changes in the expression of selected genes were then confirmed by quantitative real-time PCR and immunoblotting. Results:We found that GNAQmutant cells have aMEK-dependent transcriptional output and identified a unique set of genes that are downregulated byMEK inhibition, including the RNAhelicaseDDX21 and the cyclin-dependent kinase regulator CDK5R1whereas Junwas induced.We provide evidence that these genes are involved in cell proliferation, tumor cell invasion, and drug resistance, respectively. Furthermore, we show that selumetinib treatment regulates the expression of these genes in tumor tissues of patients with metastatic GNAQ/11 mutant uveal melanoma. Conclusions:Our findings define a subset of transcriptionally regulated genes by selumetinib in GNAQ mutant cells and provide new insights into understanding the biologic effect of MEK inhibition in this disease. Clin Cancer Res; 18(13); 1–10. 2012 AACR.

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