Host Microenvironment Shapes Uveal Melanoma Tumor Properties

Abstract

Purpose : Approximately 50% of patients diagnosed with uveal melanoma (UM) will develop liver metastases. Metastasis may be present at the time of initial diagnosis in the form of micrometastases. The pathways by which these UM micrometastases transform into clinically detectable metastases are not well understood. By comparing UM cells cultured in vitro with those recovered from an in vivo orthotopic xenograft, our study tested the hypothesis that tumor-microenvironment interactions in the liver affect UM cell properties.

Methods : Athymic nude mice were inoculated intraocularly with Mel 270, a primary UM cell line known to metastasize. Livers and spleens were recovered and used to prepare ex vivo single cell suspensions. Mel 270 and its corresponding metastatic cell line OMM 2.5 were used as in vitro controls. Quantitative PCR (qPCR) was performed to determine relative gene expression among the tumor cells using HPRT1 controlled delta delta Ct analysis. Cell culture supernatants were examined using multiplex assay to quantify levels of secreted proteins from tumor cells.

Results : qPCR analysis of genes associated with cytoskeletal signaling, angiogenesis, and cell death and survival revealed a liver-specific (compared to spleen) upregulation of pro-angiogenic molecules, including VEGFA (79.2-fold) and the transcription factor HIF1A (72.2-fold). Our work also revealed an in vivo, liver-specific blockade of the tumor suppressor TP53 (141.2-fold) in UM tumor cells by HDM2 (102.7-fold) and HDMX (96.0-fold) sequestration. Multiplex analysis of human secreted proteins revealed a high concentration of IFN-α2 (344.09 pg/mL) specific to the liver sample. VEGF concentration was elevated in both liver and spleen samples (377.17 pg/mL and 191.27 pg/mL, respectively).

Conclusions : Our data show a host-dependent, liver-specific upregulation of several UM tumor genes and cytokines. This is consistent with our hypothesis that interaction with the host liver microenvironment plays a role in shaping UM tumor properties. Further study is needed to characterize the host tissue mediators.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.