PHF2 belongs to the KDM7 histone demethylase family, locating in human chromosome 9q22.31 where multiple tumor suppressor genes accumulate.46,47 Accordingly, PHF2 is susceptible to mutate in various tumor cells, which has been demonstrated as a tumor suppressor and enhances p53-mediated apoptosis in chemotherapy.28,32,33 Besides, it was reported that PHF2 plays a crucial role in mesenchymal to epithelial transition (MET) of breast cancer, with the loss of tumor-initiating ability.17,48 In our study, we further expanded its function in EMT regulation and lung cancer metastasis. The gene discussed is PHF2; the disease is breast cancer.