In addition, it has been shown that radioresistance of cancer cells after multiple fractions of IR exposure can be linked to the induction of epithelial–mesenchymal transition (EMT), which is defined as the loss of epithelial cell characteristics, such as E-cadherin, and the gain of mesenchymal cell characteristics, such as N-cadherin, vimentin, snail, and twist [29,30]. The gene discussed is TWIST1; the disease is cancer.