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Ikram El Zaoui El-Zaoui, Michael Nicolas, Rosanna Pescini Gobert, Donata Rimoldi, Serge Leyraz, Carlo Rivolta, Alexandre Moulin; MAPkinase and PI3K/mTOR pathways inhibition in conjunctival melanoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3346.
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© ARVO (1962-2015); The Authors (2016-present)
Evidence suggests that conjunctival and cutaneous melanoma partially share similar genetic alterations. Considering the presence of BRAF and NRAS mutations in conjunctival melanoma, we have previously demonstrated ex vivo a significant activation of the Mitogen-activated protein kinase (MAPK) and the Phosphoinositide 3 kinase (PI3K/mTOR) pathways in conjunctival melanoma compared to conjunctival naevi. We now explore the inhibition of these pathways in three conjunctival melanoma cell lines.
Three conjunctival melanoma cell lines were used: CRMM1, carrying the p.V600E mutation in BRAF, CRMM2, harboring the p.Q61L NRAS mutation, and T1527A, a conjunctival melanoma cell line with no mutations in these genes that was recently established by us. WST-1 assays were performed to assess cytotoxicity with a BRAF inhibitor (PLX032), two MEK inhibitors (AZD6244 and GSK1120212), PI3K inhibitor (GDC-0941) and a dual PI3K/mTOR inhibitor (BEZ235). Viability was determined by Tryptan blue assays. Phosphorylation of ERK, MEK and S6 was tested by western blots.
CRMM1 cells were relatively more sensitive to all inhibitors than CRMM2. In addition, CRMM2 cells were also sensitive to the dual PI3K/mTOR inhibitors at low concentration (LC50 10 µM).T1527A cells showed little sensitivity to these treatments (LC50 >1 mM). Cytotoxicity was observed with all inhibitors at high concentrations for all cell lines. Furthermore, western blot experiments showed that all drugs inhibited the phosphorylation of their specific target proteins in a dose-dependent manner.
Our results confirm the sensitivity of conjunctival melanoma cell lines to selective inhibition of either the MAPK or the PI3K/mTOR pathways. However these treatments do not appear to affect the growth of a BRAF/NRAS wild type cell line (T1527A).
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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