Immunostaining markers, such as CK5/6, can be used to distinguish squamous epithelium, whereas CAM5.2 and CK7 can be used for glandular epithelium.[25] GEO data showed that CK5 and CK6 (CK6a, CK6b, and CK6c) mRNA levels decreased in ESCC, and CK8 mRNA levels increased, compared to their healthy counterparts, but CK7 mRNA levels showed no significant difference. This evidence concerns the gene KRT6A and esophageal squamous cell carcinoma.