Gene expression profiling (GEP) is clinically validated to stratify the risk of metastasis by assigning uveal melanoma (UM) patients to two highly prognostic molecular classes: class 1 (low metastatic risk) and class 2 (high metastatic risk). However, GEP requires intraocular tumor biopsy, which is limited by small tumor size and tumor heterogeneity; furthermore, there are small risks of retinal hemorrhage, bleeding, or tumor dissemination. Thus, ocular liquid biopsy has emerged as a less-invasive alternative. In this study, we seek to determine the aqueous humor (AH) proteome related to the advanced GEP class 2 using diagnostic AH liquid biopsy specimens. Twenty AH samples were collected from patients with UM, grouped by GEP classes. Protein expression levels of 1472 targets were analyzed, compared between GEP classes, and correlated with clinical features. Significant differentially expressed proteins (DEPs) were subjected to analysis for cellular pathway and upstream regulator identification. The results showed that 45 DEPs detected in the AH could differentiate GEP class 1 and 2 at diagnosis. IL1R and SPRY2 are potential upstream regulators for the 8/45 DEPs that contribute to metastasis-related pathways. AH liquid biopsy offers a new opportunity to determine metastatic potential for patients in the absence of tumor biopsy.

Small extracellular vesicles (sEVs) have been shown to promote tumorigenesis, treatment resistance, and metastasis in multiple cancer types; however, sEVs in the aqueous humor (AH) of uveal melanoma (UM) patients have never previously been profiled. In this study, we used single particle analysis to characterize sEV subpopulations in the AH of UM patients by quantifying their size, concentration, and phenotypes based on cell surface markers, specifically the tetraspanin co-expression patterns of CD9, CD63, and CD81. sEVs were analyzed from paired pre- and post-treatment (brachytherapy, a form of radiation) AH samples collected from 19 UM patients. In post-brachytherapy samples, two subpopulations, CD63/81+ and CD9/63/81+ sEVs, were significantly increased. These trends existed even when stratified by tumor location and GEP class 1 and class 2 (albeit not significant for GEP class 2). In this initial report of single vesicle profiling of sEVs in the AH of UM patients, we demonstrated that sEVs can be detected in the AH. We further identified two subpopulations that were increased post-brachytherapy, which may suggest radiation-induced release of these particles, potentially from tumor cells. Further study of the cargo carried by these sEV subpopulations may uncover important biomarkers and insights into tumorigenesis for UM.

Recent advancements in aqueous humor (AH) cell-free DNA (cfDNA) genomics have opened new avenues for ex vivo molecular profiling of retinoblastoma (RB), the most common pediatric intraocular malignancy, where biopsy is typically prohibited. While these insights offer a genetic blueprint of the tumor, they lack multi-omic molecular phenotyping, which is essential for understanding the functional state. Extracellular vesicles (EVs), naturally present in AH, are promising by offering time-resolved phenotypic information. We employed multiplex bead-based flow cytometry and Single Extracellular Vesicle Nanoscopy (SEVEN) to analyze EV phenotypes in AH from a cohort of five RB, with three uveal melanoma (UM) and two age-matched glaucoma (GLC) samples serving as controls. The studies identified CD133-enriched EVs uniquely in RB AH, absent in both GLC and UM AH. This was corroborated by further analysis of five RB cell lines, including two commercial (Y79, Weri) and three in-house developed lines, confirming CD133 enrichment and supporting its role as an RB-specific EV marker. Single-vesicle analysis demonstrated a strong association of CD133 with CD81 and CD63, with minimal CD9 presence. These results, validated through complementary techniques, position CD133 as a critical marker in RB-derived EVs, paving the way for enhanced multi-omic RB characterization and potential advancements in clinical diagnostics.

Introduction: Aqueous humor (AH), the clear fluid in front of the eye, maintains the pressure and vitality of ocular tissues. This fluid is accessible via the cornea which enables use of AH as a liquid biopsy for intraocular disease. Retinoblastoma (Rb), an intraocular cancer in children, is unique in that direct tumor biopsy is prohibited, thus liquid biopsy has great clinical potential. cfDNA in the AH as a biomarker for Rb patients has been investigated and extracellular vesicles (EVs) are detectable in the AH from adults. However, AH EVs in Rb have previously never been explored. We know very little about the heterogeneity of AH EV populations in ocular cancers. Materials and Methods: 27 AH samples from 19 patients from 13 tumor-free eyes and 11 Rb eyes were collected. Rb eyes were further divided into treatment-naïve (Rb_Tn) and treatment-active (Rb_Tx) subgroups. Unprocessed AH samples were subjected to Nanoparticle Tracking Analysis (NTA) (Nanosight NS300) for size distribution and concentration, and to Single Particle-Interferometric Reflectance Imaging Sensor (SP-IRIS) (Exoview R100) for fluorescent-based immunophenotyping of EV marker expression (CD63, CD81, and CD9). Results: NTA demonstrated the concentration of AH EVs is 3.11 x 10⁹-1.38 x 10¹⁰ vesicles/mL; majority sized 76.8-103 nm. Study group comparisons showed that non-tumor containing eyes had a smaller nanoparticle mean size compared to Rb containing eyes (P = 0.002). More EVs were significantly detected in Rb_Tn containing eyes compared to Rb_Tx containing eyes (P = 0.022), suggesting the possible presence of tumor-derived EVs in Rb_Tn which were subsequently eliminated by treatment. SP-IRIS revealed distinct patterns of tetraspanin expression of AH small EVs (sEVs). Mono-CD63+ EVs were identified to be the most dominant sEV subpopulation from AH across non-tumor and Rb_Tx eyes. However, more diverse sEV subpopulation profile was detected in Rb_Tn AH samples. Significantly lower percentage of mono-CD63+ EVs could be determined in Rb_Tn eyes compared to Rb_Tx eyes (70.3% vs. 96.1%, P = 0.001). A significant accumulation of CD9/CD63 (4.3% vs. 1.1%, P = 0.035), CD63/CD81 (20.7% vs. 2.0%, P = 0.012) and CD9/CD63/CD81 (4.8% vs. 0.8%, P = 0.022) subpopulations in Rb_Tn was also observed. An enriched mono-CD63+ sEV subpopulation identified in AH indicates this is a potential AH-specific biomarker. In the setting of Rb there was a more heterogeneous population of sEVs which normalized with treatment. Conclusions: Small EVs are readily detectable in unprocessed AH with a dominant mono-CD63+ subpopulation in AH regardless of pediatric eye disease states. Tetraspanin colocalization analysis indicates the clearance of retinoblastoma-derived EV heterogeneity by chemotherapy. These novel finding suggests a potential clinical application of measurement of sEV subpopulations in AH samples to monitor response to therapy. Citation Format: Chen-Ching Peng, Deborah Im, Shreya Sirivolu, Bibiana Reiser, Aaron Nagiel, Paolo Neviani, Liya Xu, Jesse L. Berry. Clearance of tumor-derived extracellular vesicle heterogeneity in aqueous humor after chemotherapy in retinoblastoma eyes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3416.