 Hi, and welcome to another fun Eureka Science video. Today we are going to learn about an exciting cancer finding, where scientists tried to predict how patients would respond to a specific treatment by looking at the DNA inside the tumors. Let's take a look at what they found. Stem cells produce all of the tissues in our bodies. When we are born, specialized stem cells maintain the health of specific tissues. For example, our colon has specialized stem cells that keep our colon healthy by continuously renewing the tissue. They do this in a very elegant way. In this depiction of our colon, the colonic stem cells are located at the base. The stem cells will divide and produce cells that will move up until they slough off at the top. As the cells move up, they take on specific functions, such as absorbing nutrients into our bloodstream, or secreting mucous needed for the tissue to function. We call these differentiated cells. Interestingly, we can find cells that resemble stem cells in some colon cancers. These are called colorectal cancer stem cells. So what are those? Well, cancer's tumors are composed of all kinds of cancer cells. In particular, certain cancers contain cancer cells that resemble stem cells. It's important to understand that these cells are not identical to normal stem cells. Instead of recreating a tissue like normal stem cells do, they can recreate an entire tumor. Colon cancer is a type of cancer that is thought to arise from cells that resemble stem cells. It is the second leading cause of cancer deaths and is currently treated with surgery and chemotherapy. However, after surgery, 30 to 50% of patients experience what we call disease relapse, where the tumor comes back and can be lethal. There's often very little we can do when a tumor relapses, because new tumors can occur all over the body and can be hard to treat. So from a therapeutic standpoint, we'd like to understand which patients are more likely to experience tumor relapse. However, we don't know much about what dictates colon cancer relapse. The Batia Laboratory in the Institute for Research in Biomedicine, Barcelona, and Spain wanted to better understand what causes colon cancer relapse by examining what genes or chunks of DNA are active in tumors from patients that eventually experience relapse, compared to those that don't. Genes are chunks of DNA that produce protein. However, genes only produce proteins when they are active. The activity of genes dictates what sets of proteins are produced and, in turn, controls how the cell behaves. These scientists' findings are published in their article titled, The Intestinal Stem Cell Signature Identifies Colorectal Cancer Stem Cells and Predicts Disease Relapse, published in Cell Stem Cell in May 2011. First, scientists determine what genes or chunks of DNA are active in normal, non-cancerous colon stem cells, compared to differentiated cells of the normal colon. The sets of active genes in a cell is called the gene signature. Next, the scientists looked at the sets of genes that are active, or gene signature, of a variety of different patient tumors, looking at the DNA inside the tumor. And what they found was that tumors from patients that eventually had relapse and the tumor came back after surgery had a gene signature that resembled that of colon stem cells. So the genes that were active in the cancers that relapsed were similar to active genes in colon stem cells. On the other hand, tumors that didn't relapse after surgery had a gene signature more similar to differentiated normal cells. So the next question is, is this stem cell gene signature represented here in blue in all of the cells or only a subset? When zooming into a tumor, the scientists found two different types of cells, cancer cells that resembled stem cells and cancer cells that resembled differentiated cells. When injected into mice, only the cancer cells that resembled stem cells could make another tumor, whose architecture was identical to that of the tumor it came from, with cancer stem cells and differentiated cancer cells. Scientists could again take just the cancer stem cells of this new tumor, inject them into mice, and those cells would produce a new tumor with the same organization. This has proved that these cells that resemble stem cells are truly cancer stem cells, because they're able to make more of themselves over the long term and are able to produce differentiated cancer cells. So what can we take away from this? Thanks to this study, we now know that colon cancer is driven by a special cell that resembles a stem cell, but has malignant properties, a cancer stem cell. When we isolate these human cancer stem cells, they can produce tumors in mice that look just like the tumor the cells came from, and it looks a little bit like it disorganized a normal colon. So could these cells be responsible for remaking a tumor in the case of relapse? Yes, it's possible. This study also tells us that the more the cancer gene signature resembles that of a stem cell, the more aggressive the tumor is, and the more likely the patient is to experience tumor relapse. So what does this mean for you? Using the gene signature of a tumor, is it stem cell-like, or does it resemble differentiated cells? We cannot predict tumor relapse better than disease score can. So this is very significant. If two patients present to the clinic with colon cancer, one of them has a tumor with a stem cell gene signature and the other doesn't, the first patient is predicted to relapse more often. In light of this new information, perhaps these two patients should get different cancer treatments. However, it is still unknown exactly why these cancer stem cells with a stem cell gene signature are more likely to cause relapse. As you can tell, we are not digging deeper into the tumor by examining DNA sequences and what genes are active. This will be the future of healthcare with personalized treatments based on a patient's tumor genetic makeup, because not every cancer is created equal. This video has been provided to you by Eureka Science. To stay in touch with Eureka Science, like us on Facebook, follow us on Twitter, or subscribe to our YouTube channel, or visit us at www.eurekascience.com. Thank you for watching.