According to a literature review, PRRG4 is highly expressed in breast cancer and promotes its metastasis (13); ATP1B1 is expressed at low levels in PTC tissues (16), which is not in line with our research and thus was excluded; and GCNT2 can induce the epithelial-mesenchymal transition of oesophageal squamous cell carcinoma cells and enhance cell migration and invasion (17). Here, PRRG4 is linked to breast cancer.