Comparative phosphoproteome analysis of primary and metastatic uveal melanoma cell lines

Uveal melanoma (UM) is an ocular tumor that often develops asymptomatically. Statistically, every second patient eventually develops metastases that drastically worsen the prognosis by several months of overall survival. While isolated liver perfusion with melphalan and more recently immunotherapy (Tebentafusp) are the few treatment options available for metastatic UM patients, their application is complex or expensive. There is an urgent need to understand drug response and identify potential avenues for therapy. Hence, we focused on uncovering altered phosphorylation signaling events in metastatic UM using proteomics as an approach to identify potential drug targets. We analyzed the phosphoproteomes of the primary UM cell line Mel270 and two cell lines OMM2.3 and OMM2.5, derived from metastatic lesions of the same patient. We found 177 phosphosites to be altered significantly between primary and metastatic cell lines. Pathway analysis of up-regulated phosphosites in metastatic lines suggests that Rho signaling and mitotic cell cycle to be significantly altered uncovering potential routes of signaling for metastasis. Clinical data from LUMC and TCGA datasets uncovered MARK3 expression (which links to Rho signaling) correlation with chromosome 3 status, a prognostic marker in UM, suggesting that MARK3 kinase might be involved in metastatic UM signaling.