NOS1 and cancer: Additionally, tumor samples from hepatocellular carcinoma patients show increased ASL expression and, in human colon, breast and hepatocellular carcinoma cells, silencing of ASL expression by short-hairpin RNA, or the reduction of NO production by a NOS inhibitor, inhibited cancer cells' proliferation and anchorage-independence (Box 1) (Huang et al., 2013, 2015, 2017a).