ASS1 and neoplasm: The evidence that ASS1 is epigenetically silenced in other tumor types55 and that arginine deprivation could trigger reactivation of ASS1 in this condition56 suggests that the re-expression of ASS1 we observed in the metastatic renal cells might be driven by changes in arginine availability, an event that might have occurred at either the primary tumor level or the metastatic site.