ASS1 and neoplasm: The mechanistic exploration revealed that VIP treatment through VIPR1 activation leads to the upregulation of argininosuccinate synthase (ASS1), an enzyme critical for arginine biosynthesis, and to the inhibition of the de novo pyrimidine synthetic pathway by downregulating the activation of CAD.202 Sun et al.203 discovered a critical role of FOXO3a-regulated arginine metabolic plasticity in esophageal squamous cell carcinoma (ESCC) progression, which adaptively promotes both tumor proliferation and metastasis.