SP cells’ excreting dyes are related to ABC transporters (especially ABCG2) [9], which are a series of membrane transport proteins that hydrolyze ATP transmembrane transport substrates and are expressed in a variety of CSCs, resulting in drug resistance in cancers such as esophageal cancer and oral squamous cell carcinoma [10,11]. The gene discussed is ABCG2; the disease is esophageal cancer.