ALDH1A1 and neoplasm: Since a single marker is not sufficient for characterization of CSC due to high inter-patient and intra-tumor variability, we employed various markers which have been used regularly in the field, such as CD44high/CD24−/low expression, aldehyde dehydrogenase 1 (ALDH1), stem cell-associated genes and proteins, and stem-cell associated histone modifier genes [23–26].