Abstract
Purpose: :
We have recently shown that phosphorylated (activated) receptors of several growth factors are released into the vitreous and can be detected and quantified in eyes with wet age-related macular degeneration (AMD). The current study investigates whether the level of phosphorylated vascular endothelial growth factor receptor (VEGFR-Y1175) in vitreous aspirates correlates with disease activity and can predict response to bevacizumab.
Methods: :
This is a prospective, consecutive case series of 10 patients with choroidal neovascularization and 5 control patients. Vitreous aspirates (50 - 200 uL) were analyzed by reverse-phase protein microarrays for the presence and quantification of VEGFR-Y1175.Patients were characterized as responders versus non-responders based on response to treatment. Response was defined as: 1) improvement in visual acuity of ≥ 10 letters 2) decrease in intraretinal edema and/or subretinal fluid or decrease in central 1mm retinal thickness by 40 microns on OCT 3) decreased area of leakage on fluorescein angiography by 50 % or 4) closure of retinal angiomatous proliferation (RAP) lesion.
Results: :
Among patients treated with bevacizumab, six were non-responders and five were responders. There was a statistically significant difference (p<0.0064) in VEGFR Y1175 between the responders and non-responders. There was no statistical difference between the non-responders and controls.In two eyes, VEGFR-Y1175 was measured in vitreous aspirates taken just prior to and one month following treatment. Patient 2, characterized as a responder, had an initial high level of VEGFR Y1175 prior to treatment. There was a 33 percent decrease in VEGFR-Y1175 levels after treatment.Patient 7, characterized as a non-responder had a low level of VEGFR-Y1175 prior to treatment, similar to the levels found in control eyes.
Conclusions: :
The novel use of reverse phase protein microarrays to delineate the proteome of in-office vitreous aspirates opens up new possibilities for the characterization of ocular disease. Our data has shown the previously unknown existence of phosphorylated (activated) VEGF receptor in the vitreous. We showed significant differences in the VEGF receptor levels between patients with neovascular and non-neovascular disease as well as between responders and non-responders to anti-VEGF therapy. Measurement of specific signal pathway proteins in the vitreous could become the basis for early detection, individualized timing of therapy, and help with the discovery of new therapeutic targets.
Keywords: age-related macular degeneration • proteomics • receptors: pharmacology/physiology