Cancer Cells Can "Infect" Their Healthy Neighbors

Heidi Ledford
23 October 2014
http://www.nature.com/news/cancer-cells-can-infect-normal-neighbours-1.16212

             In this article from nature.com, Heidi Ledford fills us in on new information researchers have uncovered regarding cancerous cells and their effect on the healthy cells in our body. When any cell needs to get rid of its wastes, it expels membrane-bound vesicles called exosomes containing proteins, DNA, and RNA. When the cell sends out these vesicles, some of them can join to other cells and dump their wastes inside. In the case of a cancer cell, this minimal cell-to-cell communication could lead to the infection of the other cells surrounding it. Researchers have done experiments to prove that when human breast cancer exosomes are mixed with normal cells, and then injected into mice, a tumor forms. Analyzing these results further could lead to the monitoring of the progression of cancer in the body.
            Researchers know from previous studies that cancerous cells expel more exosomes than regular cells, which brings up questions regarding the differences between these two types of exosomes. To seek answers, cancer researcher Raghu Kalluri isolated the exosomes from cancer cells and from regular cells. He found that exosomes from cancer cells held the products needed to create microRNA, a short fragment of RNA that can shut off the expression of some major genes. The genes of normal cells were then affected when exposed to the exosomes of cancer cells, and these altered cells then formed tumors when injected into mice. Another experiment involved taking exosome samples from the blood of healthy people and people with cancer. Again, this revealed that many of the cancerous exosomes formed tumors when mixed with regular cells and injected into mice, whereas none of the regular cells did. One can also conclude that cancerous exosomes are very mobile because researchers were able to obtain samples from blood. Researchers can use this new knowledge to detect and monitor cancer cells, with their exosomes being easier to isolate and study than tumor cells found in the blood. 
           In class, we are learning about the structure of cells and the different functions of the organelles within one. A major part of the cell we have studied is the membrane, which is very closely related to this article. We learned that many large molecules cannot move freely across a membrane without help from some sort of other force, which is where vesicles can come in. Vesicles are small membrane sacs that move products into, out of, and within a cell. The process in which vesicles remove products from a cell, called exocytosis, is referenced in this article when talking about the expelling of wastes from a cancer cell. The other process we talked about in class, endocytosis, is the process in which vesicles bud to a membrane and dump their contents into the cell. This is what happens to the healthy cells when they take in the contents of a cancerous exosome. Overall, this article parallels the information we have been learning about cells in class and also gives us hope that there may be a new great way to monitor cancer cells.