Longitudinal Analysis of Aqueous Humor Proteomic Biomarkers in Uveal Melanoma

Uveal Melanoma is the most common primary intraocular tumor in adults. Currently, UM is successfully treated with brachytherapy in most cases, however the way to evaluate prognosis and risk of metastatic disease remains unknown. Liquid biopsy of the AH in patients affected with UM allows for a minimally invasive and repeatable way to analyse the proteins present in order to investigate their prognostic significance and to monitor both disease and treatment outcomes. The aim of this study was to investigate in a prospective manner the longitudinal proteomic changes in the AH of subjects with UM, at baseline to one-year post-treatment. Thirty-six eyes of 36 subjects with UM were prospectively included in the study. All tumors were classified and staged according to the 8th edition of the American Joint Committee on Cancer (AJCC) classification system. The AH samples were collected with a needle and analyzed using protein chip array and ELISA techniques, as well as comprehensive multimodal imaging including ophthalmoscopy, color fundus photography, ocular ultrasonography, and SD-OCT at baseline post-brachytherapy and subsequently during follow-up at 3, 6 and 12 months. The mean age at study inclusion was 67.5 ± 12.5 years. Thirty patients (83%) had choroidal melanoma only, while 6 patients (17%) had both choroidal and ciliary body melanoma. At baseline, all the 114 quantified AH proteins showed higher expression levels in eyes with primary UM compared with the historical control group (p>0.05). The molecular signature of the cohort was characterized by a high abundance of inflammatory proteins, tissue remodeling inhibitors and specific angiogenic drivers, and a distinct homeostasis profile mediated by aquaporins. Liquid biopsy of AH proteomics can provide a molecular counterpart to structural imaging biomarkers. The post-treatment the activation of pathways involved in angiogenesis, inflammation, extracellular remodeling and fluid-regulation demonstrates that there is a complex system regulating the tumor microenvironment and suggests that tumor regression continues to evolve even after early apparent clinical control has been achieved.