KRAS and sarcoma: RAS genes, named after the rat sarcoma,304 were identified as the transformative factor in the Harvey and Kirsten strains of rat sarcoma viruses305 and were identified in the human genome in 1982.304,305 RAS proteins belong to a superfamily of GTPases, and three RAS genes (HRAS, NRAS, and KRAS) encode four highly homologous RAS proteins: HRAS, NRAS, KRAS4A, and KRAS4B, with the latter two KRAS isoforms arising from alternative splicing.306,307