In the rate-controlling steps of arginine metabolism, the differences in the levels of ASS1 and argininosuccinate lyase (ASL) between ESCC tissues and their metastatic derivatives suggest that blocking ASS1 or ASL may hinder the proliferation of ESCC at the original site and potentiate distant metastatic dissemination (88). This evidence concerns the gene ASL and esophageal squamous cell carcinoma.