Abstract 6717: Extracellular vesicles in diagnostic retinoblastoma aqueous humor correlate with disease stage and clinical outcome: a pilot study
Authors: Pike Sarah , Peng Chen-Ching , Neviani Paolo , Berry Jesse L. , Xu Liya 
Published: April 2023

Abstract
Introduction: Retinoblastoma (RB), a pediatric retinal malignancy, is unique in that it cannot be biopsied, impeding biomarker discovery. Aqueous humor (AH) is an ocular fluid that is an established source of tumor information, serving as a surrogate liquid biopsy. Extracellular vesicles (EVs) are promising biomarker candidates, and were recently established in RB AH. EVs are membrane-enclosed secretory vesicles carrying bioactive molecular information, which can be phenotyped using validated tetraspanin protein markers. Currently, relationships between EVs and RB clinical features are unknown, but establishing such relationships is necessary to determine the utility of EVs as RB biomarkers. Methods: We quantified and phenotyped EVs in 37 AH samples from 18 RB eyes with varying International Intraocular Retinoblastoma Classification (IIRC) stages and explored clinical correlations. Samples were collected from 10 eyes at diagnosis (DX) and 27 eyes during treatment (Tx). By outcome, 6 DX eyes were enucleated and 4 were salvaged. DX samples were collected from one A, one B, six D and two E eyes by IIRC group. 10μL of unprocessed AH underwent Single Particle-Interferometric Reflectance Imaging Sensor (SP-IRIS) (Exoview R100) analysis for fluorescent-based particle count and immunophenotyping of tetraspanin expression (CD63/81/9). Counts were converted to percentages. Statistics were done with Mann-Whitney U, ANOVA, and Tukey’s tests. Results: Samples from DX eyes (n=10) contained a higher number of EVs than samples from Tx eyes (n=27) (1.68 x 107 ± 4.28 x 107 per mL vs. 2.10x 106 ± 1.33 x 106 per mL) by SP-IRIS analysis. By percentage, DX samples were enriched with CD63/81+ EVs (P&lt;0.001) while Tx samples had more homogenous mono-CD63+ dominant EV populations (P=0.007). Enrichment of CD63/81+ EVs was significantly higher in enucleated AH (n=6) than salvaged AH (n=4) when compared by count (P=0.038) and marginally higher when compared by percentage (P=0.067). The CD9/81+ EV population percentage was significant in salvaged eyes (P=0.01). By IIRC, CD63/81+ EVs were most abundant in Group E eyes (n= 2) when compared to Group D eyes (n=6) by count (P&lt;0.001), and when compared to Group A+B eyes (n=2) by count (P=0.01) and percentage (P=0.019). Group A+B eyes had a larger percentage of CD9/81+ EVs than did Group E eyes (P=0.043). Conclusions: EV quantity in RB AH decreases with treatment, and phenotypic expression profiles vary by treatment status and clinical outcome. TheCD63/81+ EV subpopulation is higher in eyes with advanced Group E disease and those requiring enucleation, while the CD9/81+ subpopulation is higher in eyes with less advanced Group A+B disease and those salvaged with treatment. Our data suggests that EV phenotypes correlate with RB clinical features, and further research into these subpopulations offers the prospect of establishing critical RB biomarkers.
Citation Format: Sarah Pike, Chen-Ching Peng, Paolo Neviani, Jesse L. Berry, Liya Xu. Extracellular vesicles in diagnostic retinoblastoma aqueous humor correlate with disease stage and clinical outcome: a pilot study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6717.