Abstract 4586: To define how the uvel melanoma-liver environment crosstalk shapes metastasis growth and therapeutic response
Authors: Sriramareddy Sathya Neelature , Chen Zhihua , Li Jiannong , Chen Ann , Licht Jonathan D. , Harbour J William , Smalley Keiran 
Published: April 2023

Abstract
BACKGROUND: Uveal melanoma (UM) is derived from melanocytes of the eye. Up to 50% of individuals with primary uveal melanoma will eventually develop liver metastases through mechanisms that remain poorly described. At this time there are no systemic therapies that are effective against the majority of UM liver metastases. The goal of this study is to better understand the role of tumor-host cell crosstalk in the progression and therapeutic response of UM liver metastases.
METHODS: We used UM liver metastatic mouse models to study bidirectional cell-cell communication. Mice were treated with MEKi (trametinib, daily),HDACi (panobinostat, 3 times a week), or the combination for the period of 21 days.The tumor progression was monitored using MRI. Single cell RNA-Seq (scRNA-seq) was performed to delineate the host-tumor crosstalk and mechanisms of therapy response. Similarly, scRNA seq was conducted in vitro with mono- and co-cultures of hepatic stellate cells (HSCs) and uveal melanoma cells. Human cytokine arrays were carried out between mono and co-culture to identify and confirm unbiased growth factors released between HSCs and UM. ELISA assays were conducted to quantify the cytokine IL8 in mono and coculture cell culture supernatant. A vascular tube formation assay was carried to study the angiogenesis in presence of IL-8 and GDF15.
RESULTS: Our scRNA-Seq analyses of UM liver mets revealed a large infiltration of HSCs, along with myeloid derived suppressor cells, macrophages, dendritic cells and hepatocytes. As HSCs were the major host cell type in UM liver mets we performed scRNA-Seq on UM monocultures and UM-HSC co-cultures to determine the patterns of cell-cell interaction upon co-culture and in response to drug. Singlecell SignalR analysis identified key interactions between UM-HSC mediated through FGFR2 and RPS27A associated with increased IL-6, FOS/JUN, STA3, & NFκB signaling in the UM cells. Further studies showed that Class 2 UM cells secreted GDF15 that activated the HSCs resulting in the secretion of multiple growth factors, including MMPs, VEGFA, TGF-β1, IL8 and multiple ECM genes.As many of the identified growth factors were associated with angiogenesis, we performed co-culture assays with UM, HSC and endothelial cells and noted increased vascular network formation in the presence of activated HSCs. Addition of exogenous IL-8 was found to mimic the effects vascular network formation in vitro, suggesting this to be a potential mediated of HSC-driven angiogenic response in UM mets. Treatment of established UM liver mets with the MEKi+HDACi combination significantly decreased angiogenesis in UM liver mets, an effect associated with inhibition of IL-8 and GDF15 release.
CONCLUSION: Bidirectional communication between hepatic stellate and UM cells induces angiogenic pathways in UM both in in vitro and in vivo, leading to vascular network formation and tumor progression in the liver.
Citation Format: Sathya Neelature Sriramareddy, Zhihua Chen, Jiannong Li, Ann Chen, Jonathan D. Licht, J William Harbour, Keiran Smalley. To define how the uvel melanoma-liver environment crosstalk shapes metastasis growth and therapeutic response. [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 4586.