LRIG1 is a leucine-rich repeat (LRR) and Ig-like domain-containing single-pass transmembrane glycoprotein. LRIG1 shares 45-50% aa identity with its mammalian paralogs, LRIG2 and LRIG3. LIRG1 is expressed widely throughout mouse and human tissues, including the liver, brain, stomach, small intestine, skeletal muscle, cornea, and hair follicle. It has been shown to suppress tumor growth, regulate tissue homeostasis, and maintain stem cell quiescence. The LRIG1 ECD contains three C-type Ig-like domains as well as fifteen LRRs that are flanked by cysteine-rich regions. LRIG1 functions as a tumor suppressor by controlling cell proliferation through the negative regulation of the EGF family of receptor tyrosine kinases. LRIG1 expression, which is often dysregulated in human cancers, is a prognostic indicator of cancer development and relapse? Decreased LRIG1 is associated with an increase in recurrence and mortality for a variety of cancers including breast, uterine, headandneck, glioma, prostate, and squamous cell. Tissue homeostasis and stem cell dormancy is also thought to be modulated by the actions of LRIG1 on cell proliferation.