ALDH1A1 and lung adenocarcinoma: Furthermore, research on ALDH1 expression in lung adenocarcinoma revealed that ALDH1 expression is positively correlated with epithelial-like phenotype proteins, and through immunohistochemistry and mRNA expression profiling of adenocarcinoma tissues, it was confirmed that ALDH1 expression is associated with good prognosis (Koh et al., 2019).