FAK Inhibitor-Based Combinations with MEK or PKC Inhibitors Trigger Synergistic Antitumor Effects in Uveal Melanoma

SIMPLE SUMMARY: Uveal Melanoma (UM) is a rare and malignant intraocular tumor with dismal prognosis. Despite efficient control of the primary tumor by radiation or surgery, up to 50% of patients subsequently develop metastases, mainly in the liver. The treatment of UM metastases is challenging and the patient survival is very poor. Today, most of the tested treatments including inhibitors of protein kinase C (PKC), mitogen-activated protein kinase (MEK) or immune checkpoint blockade have been largely ineffective in patients with metastatic UM. Given that single-agent targeted therapies often activate compensatory mechanisms, combination strategies are relevant to evaluate in UM in preclinical and clinical settings. Our study confirms the previously described synergy of the dual inhibition of focal adhesion kinase (FAK) and MEK, and identifies a novel combination of drugs (FAK and PKC inhibitors) as a promising strategy for therapeutic intervention in metastatic UM. ABSTRACT: Uveal Melanoma (UM) is a rare and malignant intraocular tumor with dismal prognosis. Even if radiation or surgery permit an efficient control of the primary tumor, up to 50% of patients subsequently develop metastases, mainly in the liver. The treatment of UM metastases is challenging and the patient survival is very poor. The most recurrent event in UM is the activation of Gαq signaling induced by mutations in GNAQ/11. These mutations activate downstream effectors including protein kinase C (PKC) and mitogen-activated protein kinases (MAPK). Clinical trials with inhibitors of these targets have not demonstrated a survival benefit for patients with UM metastasis. Recently, it has been shown that GNAQ promotes YAP activation through the focal adhesion kinase (FAK). Pharmacological inhibition of MEK and FAK showed remarkable synergistic growth-inhibitory effects in UM both in vitro and in vivo. In this study, we have evaluated the synergy of the FAK inhibitor with a series of inhibitors targeting recognized UM deregulated pathways in a panel of cell lines. The combined inhibition of FAK and MEK or PKC had highly synergistic effects by reducing cell viability and inducing apoptosis. Furthermore, we demonstrated that these combinations exert a remarkable in vivo activity in UM patient-derived xenografts. Our study confirms the previously described synergy of the dual inhibition of FAK and MEK and identifies a novel combination of drugs (FAK and PKC inhibitors) as a promising strategy for therapeutic intervention in metastatic UM.