It was suggested that the dysregulation of self-renewal pathways in CSCs, such as SMO, NOTCH1 and BMI1, could be the cause for CSC tumorigenicity and treatment resistance.43–45 Studies have reported that chemotherapies using CIS and 5-FU might cause the selection of CSCs and increased the expression of self-renewal and drug resistance-related genes, like BMI146,47 or ALDH1A1,21,48,49 which were also found in our study. The gene discussed is ALDH1A1; the disease is in situ carcinoma.