Protein BEX2 also known as brain-expressed X-linked protein 2 is a protein that in humans is encoded by the BEX2 gene. It is exclusively expressed in the pancreas, kidney, liver, adrenal gland and testis. In accordance with cancer stem cell theory, there's is a link between BEX2 and dormant cancer stem cells of many different types of cancer.

The exact role of the protein is controversial however there is research that narrows down its effects. In cholangiocarcinoma stem cells, BEX2 suppresses mitochondrial functions through the TUMF protein and BEX2 is degraded by FEM1B-CUL2 E3 ubiquitin ligase complex. A link was found between BEX2 and MMP2 in regard to cancer invasion. Increase of BEX2 expression caused an increase in stem cell development in the liver but loss of BEX2 caused no noticeable abnormalities. BEX2 expression has also protected cells from apoptosis which can contribute to cancerous growth.

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