Combination small molecule MEK and PI3K inhibition enhances uveal melanoma cell death in a mutant GNAQ- and GNA11-dependent manner.
ABSTRACT Activating Q209L/P mutations in GNAQ or GNA11 (GNAQ/11) are present in approximately 80% of uveal melanomas. Mutant GNAQ/11 are not currently therapeutically targetable. Inhibiting key down-stream effectors of GNAQ/11 represents a rational therapeutic approach for uveal melanomas that harbor these mutations. The mitogen-activated protein/extracellular signal-regulated kinase/mitogen-activated protein kinase (MEK/MAPK) and PI3K/AKT pathways are activated in uveal melanoma. In this study, we test the effect of the clinically relevant small molecule inhibitors GSK1120212 (MEK inhibitor) and GSK2126458 (pan class I PI3K inhibitor) on uveal melanoma cells with different GNAQ/11 mutation backgrounds.
We use the largest set of genetically annotated uveal melanoma cell lines to date to carry out in vitro cellular signaling, cell-cycle regulation, growth, and apoptosis analyses. RNA interference and small molecule MEK and/or PI3K inhibitor treatment were used to determine the dependency of uveal melanoma cells with different GNAQ/11 mutation backgrounds on MEK/MAPK and/or PI3K/AKT signaling. Proteomic network analysis was done to unveil signaling alterations in response to MEK and/or PI3K small molecule inhibition.
GNAQ/11 mutation status was not a determinant of whether cells would undergo cell-cycle arrest or growth inhibition to MEK and/or phosphoinositide 3-kinase (PI3K) inhibition. A reverse correlation was observed between MAPK and AKT phosphorylation after MEK or PI3K inhibition, respectively. Neither MEK nor PI3K inhibition alone was sufficient to induce apoptosis in the majority of cell lines; however, the combination of MEK + PI3K inhibitor treatment resulted in the marked induction of apoptosis in a GNAQ/11 mutant-dependent manner.
MEK + PI3K inhibition may be an effective combination therapy in uveal melanoma, given the inherent reciprocal activation of these pathways within these cells.
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ABSTRACT: Somatic mutations in GNAQ gene were described as being the main oncogenic activation in uveal melanomas, whereas mutations in BRAF gene have been described as a key genetic alteration that contributes to skin melanoma development. We have previously reported differential activation of the MAPK and AKT/mTOR signalling pathways in uveal and skin melanomas harbouring, respectively, GNAQ and BRAF mutations. The aim of this work was to compare the functional effect of GNAQ and BRAF mutations in mTOR and MAPK pathway activation, cell proliferation and apoptosis. In this work, we performed transient transfection of HEK293 cells with BRAF(WT), BRAF(V 600E), GNAQ(WT), GNAQ(Q209P) and GNAQ(Q209L) vectors. We treated melanoma cell lines displaying different BRAF and GNAQ mutational status with the mTOR inhibitor RAD001 and with the MEK1/2 inhibitor U0126 and evaluated the effects in the growth of the cell lines and in mTOR and MAPK pathway effectors expression. At variance with the significant increase in the level of pmTOR Ser2448 and pS6 Ser235/236 proteins observed in cells transfected with BRAF vectors, no significant alteration in mTOR pathway effectors was observed in cells transfected with the three GNAQ expressing vectors. Also, GNAQ overexpression enhances Stat3 activation, which might mediate GNAQ oncogenic effects. None of the vectors led to significant differences in proliferation or apoptosis in the transfected cell lines. Cell lines harbouring a BRAF mutation were more sensitive to RAD001 treatment. U0126 leads to the reduction of MAPK and mTOR pathways activation in all cell lines tested. Our results indicate that GNAQ and BRAF activation drive distinct intracellular signalling pathways that may be useful for therapeutic decisions in human melanomas.07/2013; 1:e104. DOI:10.7717/peerj.104
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ABSTRACT: Uveal melanoma (UM) is the most common cause of primary eye cancer in the western world. During embryogenesis neural crest cells migrate to the neural tract where they develop into melanocytes. Melanomas of the uvea are derived from these melanocytes. UM may arise in the iris (5%), ciliary body (23%) or choroid (72%). Choroidal melanomas are the most common and usually display a discoid, dome-shaped or mushroom shaped growth pattern. Approximately 80% of the primary intraocular tumours are diagnosed as UM in patients above the age of 20 years, with a mean age of 60 years (Singh & Topham, 2003). Despite a shift towards more conservative eye treatments, survival has not improved during 1973 to 2008 (Singh et al, 2011). Growth of the primary tumour is related with histopathological features, as well as the genetic changes within these tumours. In this chapter we will not discuss iris melanoma, as this shows a different clinical and genetic behaviour, compared to ciliary body and choroidal melanoma. The clinical features, histopathological profile and genetic alterations of UM, as well as therapeutic options for primary tumours and metastases will be discussed.Melanoma - From Early Detection to Treatment, 1st edited by G. Huyn Thien, 01/2013: chapter Diagnosis, histopathological and genetic classification of uveal melanoma: pages 137-173; InTech., ISBN: 978-953-51-0961-7
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ABSTRACT: Oncogenic mutations in GNAQ and GNA11 genes are found in 80% of uveal melanoma. These mutations result in the activation of the RAF/MEK signaling pathway culminating in the stimulation of ERK1/2 mitogen-activated protein kinases. In this study, using a siRNA strategy, we demonstrate that mutant GNAQ signals to both MEK and AKT, and that combined inhibition of these pathways with the MEK inhibitor selumetinib (AZD6244) and the AKT inhibitor MK2206 induced a synergistic decrease in cell viability. This effect was genotype dependent as autophagic markers like beclin1 and LC3 were induced in GNAQ mutant cells, while apoptosis was the mechanism of cell death of BRAF mutant cells, and cells without either mutation underwent cell cycle arrest. The inhibition of MEK/ATK pathways induced activation of AMP-activated protein kinase (AMPK) in the GNAQ mutant cells. The down-regulation of AMPK by siRNA or its inhibition with compound C did not rescue the cells from autophagy, rather they died by apoptosis, defining AMPK a key regulator of mutant GNAQ signaling and a switch between autophagy and apoptosis. Furthermore, this combination treatment was effective in inhibiting tumor growth in xenograft mouse models. These findings suggest that inhibition of MEK and AKT may represent a promising approach for targeted therapy of uveal melanoma patients.Molecular Cancer Therapeutics 02/2013; 12(5). DOI:10.1158/1535-7163.MCT-12-1020 · 6.11 Impact Factor