Abstract
Purpose :
Gene expression profiling (GEP) is clinically validated to stratify metastasis risk by assigning uveal melanoma (UM) patients to two prognostic classes: class 1 (low metastatic risk) and class 2 (high metastatic risk). However, GEP requires intraocular tumor biopsy which are limited by small tumor size and tumor heterogeneity. Thus, liquid biopsy has emerged as a significantly less invasive alternative. Blood biopsy has largely been unsuccessful for clinical use in UM, however eye-specific aqueous humor (AH) liquid biopsy may be a better alternative. In this study, we seek to determine the AH proteome related to the advanced GEP class 2 using the diagnostic AH specimens.
Methods :
Twenty UM treatment naive AH were collected before plaque brachytherapy. Patients were sub-grouped by GEP classes into GEP 1 (n=12) and GEP 2 (n=5). Three patients were classified as GEP unknown (GEP NA, n=3) due to the unavailability of tumor biopsy. Ten microliters of AH samples were analyzed by proximity extension assay-derived multiplexed platform. 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 Qiagen ingenuity pathway analysis for cellular pathway and upstream regulator analysis.
Results :
GEP2 class was correlated with AJCC stages (P = 0.012), advanced clinical tumor stages (P = 0.007) and mutated BAP1 (P = 0.018). 45 DEPs were identified when comparing GEP classes. Among them, 31 are up-regulated DEPs [fold-change (FC) >2, P < 0.01] and 14 are down-regulated DEPs (FC < 0.5, P < 0.01) in GEP 2 compared to GEP1. The unsupervised clustering analysis showed that the 45 DEPs differentiate AH samples by GEP classes, and the 3 GEP NA samples were clustered with GEP1 class. Pathway analysis showed that 45 DEPs contribute to metastatic-related pathways. Two upstream regulators, IL1 receptor and SPRY2, were predicted to regulate 8 out of the 45 DEPs. IL1R2 (FC = 3.4, P = 0.021) and SPRY2 (FC = 0.6, P = 0.052) protein expression levels were found matched as prediction in our dataset.
Conclusions :
45 AH DEPs could differentiate GEP class 1 and 2 at the diagnostic stage and could be detected even when the tumor was too small to biopsy. IL1R and SPRY2 are potential upstream regulators for the 8/45 DEPs that contribute to metastasis-related pathways.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.