ALDH1A1 and non-small cell lung carcinoma: NSCLC CSCs isolated based on their expression of CD133 or CD44, Hoechst 33342 dye exclusion, high ALDH1 activity or spheroid growth have been found to display enhanced tumorigenicity in transplantation assays in vivo when compared to differentiated or bulk cancer cells (15, 27, 33, 40).