As shown in Supplementary Figure 1, we found that EMT was observed in tumors harvested from one long-term gefitinib-treated mouse (relapse tumor) out of 11 with substantially increased expression of mesenchymal markers such as vimentin, Zeb1 and Snail compared to tumors harvested from vehicle-treated littermate control mouse (primary tumor). Here, ZEB1 is linked to neoplasm.