ASS1 and cancer: To investigate the effects of arginine starvation in ASS1-deficient cancers, the ASS1-null leiomyosarcoma cell line SKLMS1 and the melanoma cell line SKMEL2 were used, whereas the osteosarcoma cell line MG63 was used as an example of a high expresser of ASS1 (Fig. 1A; refs. 1, 22, 29).