Biomedicine Update: Cd Proteins And What We Are Learning

The acronym CD comes up a lot in science and technology. For those who remember them CDs or compact discs represented the primary media for music recordings from the 1980s until the rise of MP3 technology. Cd also stands for circular dicrhoism, a spectroscopic measure of light absorption in proteins. In genetics CD is short for cluster of differentiation, those genes that are associated with abnormalities leading to cancer, developmental problems, and neuro-degenerative diseases. And Cd also is the short form for CoDing when referencing certain protein characteristics. So there are lots of CDs out there.

But the Cd we are talking about is related to the characterization of certain proteins serving as cell messengers. In a study published last month researchers at Mount Sinai Hospital in Toronto, Canada, announced a major discovery about one of these, Cd81, a protein when produced in normal cells that in near the presence of cancer cells influences the latter's ability to spread or metastasize. What the researchers found is that normal cells were involved in an information exchange with neighbouring cancer cells using Cd81.

All cells release messenger proteins, also called exosomes, of which Cd81 is one. Although cancer cell exosomes have been known to influence healthy neighbouring cells this was the first time anyone had observed the role of normal cell exosomes in helping tumors to metastasize.

The image below, courtesy of System Bioscciences, shows secreted exosomes released by a normal cell. What was never understood until recently is the role these secreted proteins played. Researchers for years had thought exosomes were cellular waste byproducts. But now we understand just how important they are as messengers in transferring information between cells and that when something is wrong with a cell its exosome can trick normal cells by delivering bad instructions.

This is giving cancer fighters a better understanding in how to stop metastasis. By pinpointing the normal cells in the tumor environment involved the researchers believe they can intercept the signal and impede the tumor's growth using nanoparticles and retroviruses to block the information exchange. By impeding the growth and isolating the tumor it will be much easier to combat the disease because it is the metastasis that ultimately kills those with cancer.