Protein biomarkers in the aqueous humor exhibit diagnostic potential for uveal melanoma

Abstract

Purpose : Uveal Melanoma (UM) is a rare, yet dangerous ocular malignancy with high rates of fatal metastasis. Timely identification of the tumor is crucial for effective intervention and management. While most UM tumors can be identified through standard eye examinations or imaging tests, smaller or less-advanced tumors may go unnoticed. Consequently, there is a pressing need for a minimally invasive solution that can reliably diagnose UM. Our objective is to explore whether a distinctive proteomic biomarker signature present in the aqueous humor can address this requirement by accurately distinguishing UM from other non-tumor ocular diseases.

Methods : In this study, we analyzed 49 diagnostic aqueous humor (AH) samples from individuals with UM and 39 samples from those with non-UM conditions including adult glaucoma, congenital retinal disorder, and congenital cataract. Using Olink's proximity extension assay-derived multiplexed platform, we examined 80 microliters of each AH sample. The normalized protein expression levels of 2886 targets were determined for each AH sample. We conducted a comparison between adult glaucoma and adult UM samples to identify differentially expressed proteins (DEPs) specifically in UM. Unpaired T-tests were used to compare the expression levels of each target in UM samples with those from individuals with adult glaucoma. The thresholds applied to determine the DEPs were p <0.01 with a fold change (FC) greater than 2 or less than 0.5 in UM.

Results : After normalizing the data, we identified 421 DEPs, with 48 showing upregulation and 373 showing downregulation in UM. Two upregulated DEPs of interest in the UM cohort were MERTK (FC=2.08, p<0.0005) and Retbindin (FC=2.48, p<4.05e-5). Some downregulated DEPs of interest include RB2 (FC=-0.70, p<0.0003), TSPAN1 (FC=-0.58, p<0.0056), RET (FC=-0.74, p<2.96e-6), and PDCD1L2 (FC= -0.41, p< 0.0005).

Conclusions : Distinctive proteomic signatures in the aqueous humor show noteworthy variations between UM and other ocular diseases. This implies that an aqueous humor protein panel has the potential to function as a diagnostic assay for UM, even in cases where the tumor size is too small for direct sampling or in non-melanoma ocular diseases. Subsequent steps in our research involve conducting a biological pathway analysis to enhance the target list for a focused panel.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.