HEY2 and non-small cell lung carcinoma: Like CD44, ALDH1 (aldehyde dehydrogenase 1) has also been ascribed as a marker for CSCs in NSCLC [96], where, remarkably, mRNA levels for Notch1, Notch2, Notch3, and their downstream effectors Hes1, Hey1, and Hey2 are found significantly upregulated compared to ALDH− cells [97].