PRODH and melanoma: Since brain metastases represent a common lethal outcome for patients with melanoma, lung and breast cancers (Preusser et al. 2012; Dagogo-Jack et al. 2016), and since PRODH overexpression is associated with the most aggressive and life-threatening form of primary brain glioblastomas (Panosyan et al. 2017), the promising ability of N-PPG to cross the blood–brain barrier and downregulate PRODH expression deserves further study in preclinical models of primary and metastatic brain tumors.