We aimed at testing whether NOS and/or NOX would distinguish between the 2′ from the 3′ isomer of NS1 in their inhibition of recombinant NOS and NOX2 C-terminal (cytosolic part, residues 300–580) activities, and their effects on the viability and migratory properties of melanoma and breast cancer cells. The gene discussed is NOS1; the disease is breast carcinoma.