KRAS and colorectal cancer: A survey of human tumor samples, cancer cell lines, and xenografts of lung, pancreatic, and colorectal cancers found mutant allele specific imbalance (MASI), where the mutant allele makes up more than half of the gene copies, in 58% of KRAS-mutated samples; over half of these imbalances were due to complete loss of the wild-type allele (uniparental disomy) [40].