Pegargiminase Suppresses the Fanconi Anemia Pathway and Promotes Melphalan‐Induced DNA Double‐Strand Breaks in Uveal Melanoma

ABSTRACT

Uveal melanoma is a hard‐to‐treat arginine‐dependent cancer secondary to argininosuccinate synthetase 1 (ASS1) loss with half of patients succumbing to liver‐dominant metastases. Arginine deprivation with pegargiminase is a novel antimetabolite strategy for patients with uveal melanoma. We investigated the preclinical rationale for combining pegargiminase with melphalan, an alkylating agent approved recently for the treatment of hepatic‐centric disease. Drug sensitivity of ASS1‐deficient uveal melanoma cell lines was performed in 2D culture using proliferation and cytotoxicity assays, with analysis of cell death, cell cycle, DNA double‐strand breaks, and interrogation of the molecular mechanism of action by RNA‐seq. ADI‐PEG20 and melphalan suppressed uveal melanoma cell line proliferation and triggered cytotoxicity, effects which were enhanced with the drug combination. ADI‐PEG20 downregulated multiple genes of the Fanconi anemia pathway and synergized with melphalan to increase DNA double‐strand breaks. Melphalan and pegargiminase is a rational new drug combination that warrants clinical testing in uveal melanoma.