TNF and neoplasm: CD70, as a member of tumour necrosis factor (TNF) ligand family, had been repeatedly reported to involve in tumour proliferation, invasion, metastasis and T cell immunity.34 Importantly, CD70 was considered as an emerging target in cancer immunotherapy.35 Our results showed that CD70 had an accessible promoter and actively expressed in lung‐metastatic breast cells, implying the importance of CD70 and providing a potential diagnosis and therapy biomarker.