CD105 (Endoglin, ENG) is a type I membrane vascular endothelium glycoprotein that localizes to the cell surface and plays a crucial role in angiogenesis. It acts as a TGF-beta coreceptor and is involved in the TGF-beta/BMP signaling cascade that leads to the downstream activation of SMAD transcription factors. In cancer, it plays a role in tumor growth, survival and the metastasis of cancer cells to other locations in the body. In immunohistochemistry of normal tissue, ENG has membranous positivity on endothelial cells and placental trophoblasts, and expressed in the lung, kidney, placenta, cerebral cortex, gastrointestinal tract, muscle, reproductive and various other tissues. References: FASEB J. 2003 Jun;17(9):984-92, PMID: 12773481; Cancer Res. 2001 Nov 1;61(21):7846-54, PMID: 11691802; Clin Cancer Res. 2008 Apr 1;14(7):1931-7, PMID: 18381930