JTC801 regresses uveal melanoma progression through novel methuosis-like cell death via lysosomal dysfunction

Uveal melanoma (UM) is the most frequent primary intraocular malignancy in adults with high metastasis and mortality rate, whose effective therapeutic strategy is still in urgent need. Specifically, apoptosis-resistance is a great challenge for advanced UM patients, therefore novel therapeutic options targeting otherwise death modality, which may potentially enhance treatment effect, need to be further identified. Here, by a kinase inhibitor library of 113 approved drugs screening, JTC801, a selective antagonist of nociceptin receptor (NOP), exhibits a specifically strong tumor-killing ability in a lower dosage. JTC801 induces UM cell methuosis-like death characterized by cytoplasmic vacuolization, markedly regresses tumor progression and metastasis, prolongs the survival in multiple UM tumor models without apparent adverse effects. Mechanistically, JTC801-caused nutrient-deficient stress by mitochondrial damage which triggers macropinocytosis and cytoplasmic vacuolization in UM cells. Concomitantly, JTC801 is trapped into the macropinosomes that fuse with lysosomes, further causing lysosomal over-acidification, de-glycosylation of lysosomal associated membrane protein 1(LAMP1), inhibiting cathepsinsmaturation, and exacerbating lysosomal membrane permeabilization (LMP), eventually inducing UM cell methuosis-like death. Collectively, our findings identify JTC801 as a potential valuable antitumor drug especially for apoptosis-resistant advanced UM patients, and provide insight into the distinct tumor cytotoxicity role of JTC801 in UM treatment.