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Andrew Smith, Mercy D Pawar, Cagri G Besirli, Marcian E Van Dort, Brian D Ross, Stefanie Galbán; Ocular Toxicity Profile of Novel PI3K/MEK Dual Inhibitor. Invest. Ophthalmol. Vis. Sci. 2017;58(8):251. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the ocular toxicity of a novel dual kinase inhibitor targeting MEK and PI3K pathways using in vitro and in vivo analysis.
661W, in vitro photoreceptor cell line model and ARPE-19, adult retinal pigment epithelium cells were treated with PI3K inhibitor (ZSTK474), MEK inhibitor (PD0325901), ZSTK474 & PD0325901 combined and dual inhibitor compounds targeting both the PI3K/Akt/mTOR and Ras/ MEK/ERK pathways. Cells were incubated at concentrations 1uM, 5uM, 10uM, 25uM, 50uM and 100uM for 4hours and 24hours and western blots performed to determine PI3K and MEK activity. Cell Viability and caspase activity were measured using luminescent cleavage assay kit after 24hrs of incubation with the inhibitors. Intraocular injections were performed in an animal model to determine in vivo toxicity profile.
For both cell lines. a dose-dependent decrease in levels of p-AKT and p-ERK1/2 was observed for the dual inhibitors. The PI3K inhibitor (ZSTK474) and MEK inhibitor (PD0325901) only inhibited Akt phosphorylation or Erk phosphorylation, respectively. The combined treatment of PI3K inhibitor (ZSTK474) and MEK inhibitor (PD0325901) showed complete inhibition of both Akt and Erk phosphorylation. Inhibition of the PI3K pathway with ZSTK474 in 661W cells led to increased caspase activity and cell death, which was potentiated by MEK inhibitor PD0325901. Dual inhibitor was less toxic to 661W cells, causing less caspase activity and loss of cell viability. In contrast to 661W cells, ARPE-19 cells were more vulnerable to MEK inhibition and resisted the toxic effects of dual inhibitor compared to individual or combination of PI3K and MEK inhibitors. MEK inhibitor led to retinal necrosis and retinal hemorrhages in vivo, which was observed with less intensity using the dual inhibitor.
A novel dual inhibitor of PI3K and MEK inhibited Akt and ERK phosphorylation in 661W and ARPE cells. The dual inhibitor demonstrated better toxicity profile compared to the combination of agents targeting each pathway independently. By blocking the key intracellular pathways that regulate cell survival and proliferation, PI3K/MEK dual inhibitor compounds could be potential therapeutic agents for malignant tumors with improved ocular and neurotoxic profiles.
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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