Aqueous VEGF-A Levels as a Liquid Biopsy Biomarker of Retinoblastoma Vitreous Seed Response to Therapy.

Purpose: Regression of retinoblastoma vitreous seeds (VS) during intravitreal chemotherapy can be delayed, resulting in supernumerary injections. Similarly, VS relapse may not be clinically evident at first. A predictive biomarker of tumor regression and relapse could help guide real-time clinical decision making. Retinoblastoma is an oxygen-sensitive tumor; paradoxically, VS survive in the hypoxic vitreous. We hypothesized that VS elaborate pro-angiogenic cytokines. The purpose was to determine if pro-angiogenic cytokine signatures from aqueous humor could serve as a biomarker of VS response to treatment. Methods: Multiplex ELISA was performed on aqueous from rabbit eyes with human retinoblastoma VS xenografts to identify expressed proangiogenic cytokines and changes in aqueous cytokine levels during intravitreal treatment were determined. Confirmatory RNAscope in situ hybridization for VEGF-A was performed on human retinoblastoma tumor sections and VS xenografts from rabbits. For human eyes undergoing intravitreal chemotherapy, serial aqueous VEGF-A levels measured via VEGF-A-specific ELISA were compared to clinical response. Results: VEGF-A was highly expressed in human retinoblastoma VS in the xenograft model, and was the only proangiogenic cytokine that correlated with VS disease burden. In rabbits, aqueous VEGF-A levels decreased in response to therapy, consistent with quantitative VS reduction. In patients, aqueous VEGF-A levels associated with clinical changes in disease burden (regression, stability, or relapse), with changes in VEGF-A levels correlating with clinical response. Conclusions: Aqueous VEGF-A levels correlate with extent of retinoblastoma VS, suggesting that aqueous VEGF-A may serve as a predictive molecular biomarker of treatment response.

Decreased Expression of Soluble Epoxide Hydrolase Suppresses Murine Choroidal Neovascularization.

Neovascular or "wet" age-related macular degeneration (nAMD) is a leading cause of blindness among older adults. Choroidal neovascularization (CNV) is a major pathological feature of nAMD, in which abnormal new blood vessel growth from the choroid leads to irreversible vision loss. There is a critical need to develop novel therapeutic strategies to address limitations of the current anti-vascular endothelial growth factor biologics. Previously, we identified soluble epoxide hydrolase (sEH) as a possible therapeutic target for CNV through a forward chemical genetic approach. The purpose of this study was to validate sEH as a target by examining retinal expression of sEH protein and mRNA by immunohistochemistry and RNAscope in situ hybridization, respectively, and to assess the efficacy of an adeno-associated virus (AAV) vector designed to knock down the sEH gene, Ephx2, in the murine laser-induced (L-) CNV model. nAMD patient postmortem eye tissue and murine L-CNV showed overexpression of sEH in photoreceptors and retinal pigment epithelial cells. Ephx2 knockdown significantly reduced CNV and normalized mRNA expression levels of CNV-related inflammatory markers. Thus, this study further establishes sEH as a promising therapeutic target against CNV associated with nAMD.

Ferrochelatase is a therapeutic target for ocular neovascularization.

Ocular neovascularization underlies major blinding eye diseases such as "wet" age-related macular degeneration (AMD). Despite the successes of treatments targeting the vascular endothelial growth factor (VEGF) pathway, resistant and refractory patient populations necessitate discovery of new therapeutic targets. Using a forward chemical genetic approach, we identified the heme synthesis enzyme ferrochelatase (FECH) as necessary for angiogenesis in vitro and in vivo FECH is overexpressed in wet AMD eyes and murine choroidal neovascularization; siRNA knockdown of Fech or partial loss of enzymatic function in the Fechm1Pas mouse model reduces choroidal neovascularization. FECH depletion modulates endothelial nitric oxide synthase function and VEGF receptor 2 levels. FECH is inhibited by the oral antifungal drug griseofulvin, and this compound ameliorates choroidal neovascularization in mice when delivered intravitreally or orally. Thus, FECH inhibition could be used therapeutically to block ocular neovascularization.