KRAS and colorectal cancer: Inhibition of Krasval12 by shRNA has been previously shown to decrease tumourigenicity in Capan-1 cells upon subcutaneous implantation (Brummelkamp et al, 2002) and in murine C26 colorectal cancer cells in vitro. The Kras knockdown cells formed fewer tumours and did not cause morbidity (Smakman et al, 2005).