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Chandrani Chattopadhyay, Elizabeth Grimm, Scott Woodman; Simultaneous Inhibition of the HGF/MET and Erk1/2 Pathways Affect Uveal Melanoma Cell Growth and Migration. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4211.
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© ARVO (1962-2015); The Authors (2016-present)
About 50% of primary uveal melanoma metastasize, and almost all metastatic uveal melanomas involve the liver. Based on the biological evidence of metastatic uveal melanoma tropism to the liver, hepatocyte growth factor (HGF) has been proposed to be an important micro-environmental element in attracting and supporting uveal melanoma metastasis through activation of MET, the HGF receptor. It is also known that unlike cutaneous melanoma, the majority (>85%) of uveal melanoma express mutations in the G-proteins (GNAQ or GNA11) that drive the MEK/ERK1/2 pathway. Therefore, we propose that the combination of MET and MEK inhibition, using clinically relevant small molecule inhibitors, would have selective inhibitory effects on the growth and migration of well-characterized mutant versus non-mutant uveal melanoma cell lines.
Western-blot analysis was done to determine the relative protein levels of ERK1/2 and MET in uveal melanoma cells. Drug treatment studies were performed to determine the singular and combinatorial effect of AZD6244 (MEKi) and MK-8033 (METi) on downstream markers. Further studies were performed to evaluate the effect of combination MEKi and METi treatment on cell growth, apoptosis and cell migration. Cell growth was tested by MTT assays, cell migration by in vitro Boyden chamber assays and apoptosis by monitoring PARP processing.
All uveal melanoma cell lines with a GNAQ mutation express MET mRNA and protein. The level of mRNA expression correlated well with protein expression. MEKi treatment, but not METi treatment, resulted in markedly reduced ERK1/2 phosphorylation. Either MEKi or METi treatment alone resulted in reduced cell proliferation, but only modest induction of apoptosis. The combination MEKi + METi resulted in significant reduction of proliferation only in GNAQ mutant cells. Uveal melanoma cell migration was blocked by the METi, but not the MEKi treatment.
MET protein expression showed no correlation with GNAQ mutation status. Combining MEKi with METi treatment may have added benefit to either treatment alone in reducing cell growth in GNAQ mutant cells, but not wild-type cells. In addition, combining METi treatment with a MEKi regimen adds the effect to limiting uveal melanoma cell migration.
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