Leucine-Rich Repeat-Containing Protein 3B (LRRC3B) belongs to the LRRC3 family. LRRC3B is single-pass membrane protein and contains three leucine-rich repeats, one LRRCT domain, and one LRRNT domain. LRR-containing proteins, of which there are greater than 2,000, participate in many important processes, including plant and animal immunity, hormone-receptor interactions, cell adhesion, signal transduction, regulation of gene expression, and apoptosis. A number of microarray expression profiling studies on human cancers have shown that LRRC3B is down-regulated in gastric, breast, colon, testis, prostate and brain cancers, suggesting LRRC3B involvement in carcinogenesis