Recruitment and activation of hepatic stellate cells by uveal melanoma cells in a xenograft mouse model

Abstract

Purpose : Uveal melanoma (UM) spreads to the liver in half of the cases, and the survival rate following the report of metastasis is less than 10% at 2 years. Activated hepatic stellate cells (HSCs) play pivotal roles in the metastatic progression of colorectal and pancreatic cancers. We thus tested the hypothesis that HSCs would provide a suitable microenvironment that will enhance the UM cell invasion using a xenograft mouse model of metastatic UM.

Methods : Fluorescent metastatic UM cell lines H79, MU2F, TJU-UM001 and OMM2.3 were inoculated alone or with human HSCs in the spleen of immunodeficient mice (N=8/group) to generate micro- and macrometastases in the liver in 3-6 weeks. The growth of the hepatic lesions was imaged with an in vivo imaging system. Histological analyses were performed on formalin-fixed paraffin-embedded (FFPE) tissue sections using hematoxylin & eosin and Masson’s trichrome stains, and antibodies against MART-1, α-SMA, Ki67 and CD31 (imaging software: NDP.view 2). We compared our findings with stainings in UM liver metastases from patients treated by partial hepatectomy (N=12).

Results : All UM cell lines, inoculated alone or with human HSCs, spread to the liver as micro- or macrometastases. Furthermore, UM cell lines exhibited various invasive capabilities. Histological analyses of FFPE tissue sections revealed multiple metastasis foci, a significant recruitment of both host and injected human HSCs near the lesions, as well as an increase in extracellular matrix production. Interestingly, activated HSCs surrounding micro- and macrometastasis, as well as desmoplastic areas were also found in patient hepatectomy samples.

Conclusions : The results in both our xenograft model and a cohort of patients are consistent with our hypothesis that HSCs are recruited and activated by UM lesions, thus providing a permissive microenvironment to invasion. Further characterization of the paracrine signaling of activated HSCs and their desmoplastic stroma will be needed to understand how to antagonize these prometastatic contributors.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.