BIRC5 (Survivin) is an Inhibitor of Apoptosis (IAP) family protein that promotes proliferation and blocks apoptosis in cells. It is a component and regulator of the chromosome passage protein complex and is necessary for proper chromosome alignment and segregation during mitosis and cytokinesis. Furthermore, it is necessary for the proper development of neurons in the central nervous system. While BIRC5 does have limited expression in adult tissues (highest in the testes and thymus), it is predominantly expressed either during embryogenesis or in cancer, and it is a general biomarker for many cancers including lung, breast, colorectal, pancreatic, hepatocellular, esophageal, ovarian cancer, melanoma, glioma and others. BIRC5’s anti-apoptotic functions alongside its patterns of expression make it a target of inhibition therapies for various cancers. In immunohistochemistry of normal adult tissue, BIRC5 has nuclear positivity in populations of cells in the thymus and other lymphoid tissues, the gastrointestinal tract, squamous epithelia, and reproductive tissues. References: J Exp Clin Cancer Res. 2019 Aug 22;38(1):368, PMID: 31439015; Cancer Cell Int. 2016 Jun 23;16:49, PMID: 27340370; Indian J Med Res. 2015 Apr; 141(4): 389–397, PMID: 26112839; Journal of Neuroscience. 2005. 25 (30): 6962-6970, DOI: 10.1523/JNEUROSCI.1446-05.2005;