There are three different types of basic cell communication and they are: surface membrane to surface membrane, exterior, which is between receptors on the cell, and direct communication, which means signals pass inside the cell itself. The junctions of these cells is incredibly important because they are the means by which cells communicate with one another. Epithelial cells especially rely on these junctions because when one is injured, these junctions provide the means and communication to seal these injuries. These junctions are especially present in the organs of most species. However, it is also through cell signaling that tumors and cancer can also develop. Stem cells and tumor-causing cells, however, do not have gap junctions so they cannot be affected in the way that one would control a typical epithelial cell. Upstream cells signaling pathways control the proteins and genes that are expressed, which can both create a means for cancer to develop without stopping or a means for treatment for these diseases by targeting these specific upstream signaling pathways. Much of cell communication happens when ligands bind to the receptors of the cell membrane and control the actions of the cell through this binding. Genes can be suppressed, they can be over expressed, or they can be partially inhibited through cell signaling transduction pathways. Some research has found that when gap junction genes were transfected into tumor cells that did not have the gap junction genes, the tumor cells became stable and points to the ability of gap junction genes to inhibit tumors.
Communication in Cancer
Cancer cells will communicate via gap junctions most of the time, and the proteins that form these gap junctions are known as connexins. These connexins have been shown to suppress cancer cells, but this suppression is not the only thing that connexins facilitates. Connexins can also promote tumor progression; therefore, this makes connexins only conditional tumor suppressors. However, this relationship that connects cells makes the spreading of drugs through a system much more effective as small molecules can pass through gap junctions and spread the drug much more quickly and efficiently. The idea that increasing cell communication, or more specifically, connexins, to suppress tumors has been a long, ongoing debate that is supported by the fact that so many types of cancer, including liver cancer, lack the cell communication that characterizes normal cells.