Single-cell RNA-seq reveals intratumoral heterogeneity in primary uveal melanomas and discloses new targetable vulnerability

Lack of specific markers for invasive uveal melanoma cells prevents early diagnosis of metastasis, while no systemic treatment options are available for patients with disseminated uveal melanomas. Intra-tumor heterogeneity has been recognized in numerous cancers as the main cause of metastasis development and therapy resistance. However, in uveal melanomas the specific subpopulations and their biological function which influence tumor behavior remained unknown. Here, using scRNA-seq analysis of six different primary uveal melanomas, we uncovered previously unrecognized intratumor heterogeneity. We localized diverse tumor-associated populations and transcriptional states in primary uveal melanomas. We also unraveled a gene regulatory network underlying a poor prognosis melanoma state. Heterogeneity was demonstrated in uveal melanoma tissue using the RNAscope assay. Thus, single-cell analysis offers an unprecedented view of intratumor heterogeneity in primary uveal melanoma, identified bona fide biomarkers for metastatic cells in the primary tumor, and unravel targetable modules driving metastase formation and growth, with critical implications for prognosis and therapeutic opportunity. Single-cell RNA-seq of uveal melanoma cells from six patients.