CD164, also known as sialomucin core protein 24 or endolyn, is a protein found on the surface of various cells throughout the human body. It is a type I integral transmembrane sialomucin, spanning the cell membrane and heavily decorated with sugar molecules. The protein is encoded by the CD164 gene on human chromosome 6. CD164 plays a part in cellular communication and maintaining tissue organization.
The Role of CD164
CD164 serves several functions, acting as a cell adhesion molecule that helps cells stick to each other and their surroundings. It is found on various cell types, including hematopoietic stem cells, the precursors to all blood cells, and endothelial cells lining blood vessels. Its presence on these cells highlights its role in blood cell development and vascular integrity.
CD164 regulates cell adhesion, the process by which cells attach to other cells or the extracellular matrix. It also influences cell migration, the directed movement of cells, and the regulation of cell growth and differentiation into specialized types. For instance, CD164 facilitates the adhesion of CD34+ hematopoietic stem cells to the bone marrow stroma, the supportive tissue in bone marrow. It also modulates the migration of umbilical cord blood CD133+ cells through interaction with the CXCL12/CXCR4 axis.
CD164 contributes to muscle development by promoting myogenesis, the formation of muscle tissue. It enhances CXCR4-dependent cell motility, the ability of cells to move, and regulates myoblast migration and fusion into myotubes, the building blocks of muscle fibers. These functions contribute to maintaining healthy tissue architecture and coordinating various biological responses, including those of the immune system.
CD164 in Disease
Alterations in CD164 expression or function are linked to various disease states, particularly in cancer progression. Elevated levels of CD164 have been observed in numerous cancers, including prostate, lung, colon, ovarian, and bladder cancers. In these cancers, CD164’s influence on cell adhesion, migration, and proliferation is often implicated.
In prostate cancer, CD164 may play a part in metastasis, the spread of cancer cells, and their infiltration into bone marrow. Studies indicate that CD164 expression in prostate cancer cells can be responsive to stromal-derived factor-1 (SDF-1), a chemokine that guides cells to specific locations. This suggests a mechanism by which prostate cancer cells might home to bone.
CD164 also promotes tumor growth and metastasis in other cancers. For example, in lung cancer, elevated CD164 expression is associated with aggressive metastasis, advanced disease stages, and shorter overall survival. It promotes the growth of lung tumor-initiating cells and contributes to drug resistance by activating the Akt/mTOR signaling pathway. Silencing CD164 in bladder cancer cells inhibits their proliferation, migration, and invasion, and reduces tumor growth and metastasis. CD164 has also been implicated in inflammatory conditions, and its dysregulation can affect immune responses.
Research and Future Directions
Scientists are actively investigating CD164 to understand its roles in health and disease, exploring its potential as a biomarker. Elevated CD164 expression has been observed in patients with certain conditions, such as Sezary syndrome, a type of blood cancer. This suggests that measuring CD164 levels could help in diagnosing certain diseases or predicting their progression.
Research is also exploring CD164 as a potential target for therapeutic interventions, particularly in cancer. Given its role in promoting tumor growth, metastasis, and drug resistance, strategies to block its activity or target cells that express high levels of CD164 are being investigated. For instance, inhibiting the Akt/mTOR pathway, influenced by CD164, has shown promise in hindering tumor growth.
Developing therapies that specifically target CD164 or its associated pathways could offer new avenues for treating diseases where this protein is dysregulated. This research aims to translate laboratory findings into new diagnostic tools and more effective treatments for patients.