PTK7 is a member of the receptor tyrosine kinase family otherwise known as Colon Carcinoma Kinase 4 (CCK4). PTK7 is highly expressed in the kidney, liver, lung, pancreas and melanocytes with weaker expression being detected in the thyroid gland, ovaries, brain, heart and skeletal muscle. PTK7 may play a role in embryonic development. It is thought to function as a cell adhesion molecule and as a novel regulator of the planar cell polarity (PCP) pathway in vertebrates. Studies also suggest that PTK7 may be involved in the tumour progression. A loss of PTK7 expression has been observed in melanoma cell lines, whereas increased levels of PTK7 have been detected in high-throughput acute myeloid leukaemia samples. In addition, PTK7 is not expressed in normal colon but has been detected in colon carcinomas and as such is a potential marker for tumour progression.Synonyms: CCK-4, Colon carcinoma kinase 4, Tyrosine-protein kinase-like 7