Co-expression of ANGPTL-4 and STAT3 in liver metastasis of uveal melanoma

Abstract

Purpose : Metastatic uveal melanoma (UM) has poor overall survival despite treatment, as the tumor escapes antitumor inflammatory responses. In metastatic cells of UM, STAT3 (Signal Transducer and Activator of Transcription-3) is highly expressed as reported by us. Elevated ANGPTL4 (Angiopoietin like-4) expression has been found by other groups including ourselves. STAT3 and ANGPTL4 have been shown to have pro- and anti-oncogenic functions in the liver. The liver is the predominant site of UM metastasis, and it is necessary to understand how UM promotes liver metastasis. Our goal was to determine whether these two genes are co-expressed in liver metastatic UM by mRNA in situ hybridization analysis to better delineate drug targets and define future pathways of in vitro and in vivo analysis.

Methods : Formalin-fixed paraffin-embedded (FFPE) tissue samples obtained from UM patients were studied. RNA in situ hybridization (RNAish) was used to define ANGPTL-4 (green) and STAT-3 (red) expression. Target-specific signal was enhanced, while background noise from non-specific hybridization was reduced. The mean fluorescence intensity (FI) and colocalization (CL) are reported as: moderate (m) and strong (s). The IRB at the University of Tennessee approved the protocol (ID# 20-07147).

Results : Two non-matched primary enucleated UM eyes (P1 and P2), four UM liver metastasis [LM] (P3, P4, P5, P6), one liver biopsy from a stage IV neuroendocrine tumor [NET] (P7) were included in our analysis. LM was confirmed by histopathology and positivity to Melan-A +/- S-100 +/- SOX10 +/- HMB-45. NET was confirmed by positivity to pancytokeratin, synaptophysin, CD56, TTF-1 and Ki-67 index of 77%. P1 and P2 had strong FI and CL in the UM eye tumor. LM P3 and P4 had moderate FI and CL, LM P5 and P6 had strong FI and CL. NET P7 patient had strong FI and moderate CL. Fig 1 summarizes clinical characteristics, FI and CL. Fig 2 exemplifies patients 2, 5 and 6.

Conclusions : STAT3 and ANGPTL4 are highly co-expressed in UM in both the eye and liver metastasis. We are conducting in vitro and in vivo experiments based on our current relevant findings. These results might have major implications for therapeutic approaches to metastatic uveal melanoma.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Fig 1 BT- brachytherapy. Bx- Biopsy. NA- Not available. ND- Not done as eye metastasis was the first tumor found before systemic workup.

 

Fig 2- H&E: Hematoxilin & Eosin