CXCR4 and neoplasm: Low doses of endogenous TNF-α produced by normal epithelial cells or epithelial-derived cancer cells can also act as a tumor promoter, in NSCLC cells, the TNF-α expression may affect the normal lung adjacent to the tumor[27], in human breast cancer cell, TNF-α enhanced invasiveness of the malignant cells dependent on matrix metalloprotease[28], in ovarian cancer cells the CXCR4 expression also in a TNF-α–dependent manner[29].