Notably, both gene products are oncogenic when the KRAS locus sustains a mutation in exons 2 or 3 resulting in constitutively active KRAS proteins, each capable of transforming cells (Voice et al., 1999), suggesting that studying the characteristics of both isoforms will provide a better understanding of the biology of KRAS-driven cancers (Figure 1). The gene discussed is KRAS; the disease is cancer.