GPRC5A plays a role in regulating differentiation and in maintaining homeostasis of epithelial cells, exerting its effects via multiple signaling pathways including cAMP, NF-kB, FAK/Src and STAT3. It is also thought to be involved in the embryonic development and maturation of the lung and kidneys. It is expressed in epithelial cells in the adult lung, where it is involved in negative regulation of STAT3. Deletion of GPRC5A leads to spontaneous tumorigenesis in the lung in mice, and it has suppressed expression in non-small cell lung cancer cell lines, suggesting a role as a tumor suppressor (likely via its regulation of STAT3) in the lung. In some other cancers, GPRC5A seems to promote tumorigenesis and elevated levels are associated with poor prognosis in colorectal cancer, gastric cancer, and pancreatic carcinoma. In immunohistochemistry, GPRC5A has highest membranous positivity int he lung, and is also found in the kidney, gastrointestinal tissue, thyroid, brain, and at lower levels in a few other tissues. References: Cancer Res. 2010 Nov 1;70(21):8917-26, PMID: 20959490; BioMed Research International. 2018. 2018 (1823726), DOI: 10.1155/2018/1823726