As high ALDH activity leads to several types of malignancies, serves as a cancer stem cell marker, and correlates with poor prognosis [23], we then tested ALDH activity in cells transfected with TROY. Results showed TROY overexpression dramatically enhanced ALDH activity in HCC cells (Fig. 2E), indicating the cancer stemness maintenance function of TROY in HCC. This evidence concerns the gene TNFRSF19 and hepatocellular carcinoma.