KRAS,also called p21,is a member of the Ras superfamily of proteins. It is located on human chromosome 12,and contains four coding exons and a 5' non-coding exon (PMID: 12778136). KRAS is a membrane-anchored guanosine triphosphate/guanosine diphosphate (GTP/GDP)-binding protein and is widely expressed in most human cells. Like other members of the Ras family,the KRAS protein is a GTPase,and it is involved in intracellular signal transduction and mainly responsible for EGFR-signaling activation (PMID: 19117687). KRAS mutations have been found in various malignancies,including lung adenocarcinoma,mucinous adenoma,ductal carcinoma of the pancreas and colorectal carcinoma. KRAS has two isoforms,a and b.