BEX4 and cancer: For this family, BEX2 overexpression reportedly promoted the proliferation of cancer cells, whereas its downregulation promoted apoptotic cell death.12, 13 Microarray data demonstrated a higher expression level of BEX4 in primary tumors that had metastasized than in those that had not.14 In addition, mRNA levels of BEX4 in human lung and liver tissues were reportedly higher than those in normal tissues.15, 16