Cystinosin promotes melanoma development through ferroptosis via the GNMT/PARP1 pathway

Introduction Cutaneous melanoma, one of the most aggressive and lethal skin cancers, is highly metastatic and often resistant to conventional therapies. This study aims to explore the biological effects of CTNS on melanoma and its underlying mechanisms, so as to identify a novel promising therapeutic target for melanoma treatment. Methods Bioinformatic analysis assessed CTNS expression and prognostic value in melanoma. qRTPCR, western blot and immunohistochemistry detected CTNS expression. CCK8, Transwell and wound healing assays evaluated cell proliferation and migration. A nude mouse subcutaneous xenograft model explored in vivo tumor growth. Flow cytometry, microplate reader, electron microscopy and ferrous probe assays measured cell cycle, apoptosis, ROS, GPX activity, MDA, ultrastructure and free iron. Western blot, coimmunoprecipitation and immunofluorescence verified ferroptosis signaling and protein interactions. Cytoplasmicnuclear fractionation, PCR and western blot clarified CTNSdependent regulation of GNMT nuclear localization and the CTNS/GNMT/PARP1 ferroptosis axis, validated by in vivo tumor assays. Results CTNS was upregulated in melanoma and predicted poor prognosis. CTNS knockdown suppressed melanoma migration and tumor growth, triggering ferroptosis evidenced by reduced GPX activity, elevated ROS, free iron and MDA, and typical mitochondrial ferroptotic morphology. CTNS depletion increased GNMT total and nuclear levels, downregulated PARP1, and decreased GPX4, ferritin and HIF1α; GNMT silencing rescued PARP1 reduction, while PARP1 overexpression reversed ferroptosis. Discussion CTNS knockdown promotes GNMT nuclear accumulation, inhibits PARP1 expression, and consequently triggers ferroptosis in melanoma cells. Our findings suggest that CTNS merits further evaluation as a potential therapeutic target for patients with advanced melanoma.