Can stem cells help one with liver cancer?
-A curious adult from California
September 25, 2008
It feels like stem cells are in the news all the time these days. These cells might one day cure incurable conditions like Parkinson's or paralysis. They are also helping us better understand what is going on with cancer. And how better to treat it.
Recently scientists have made progress in using stem cells to treat liver cancer. Basically they are using stem cells to grow healthy liver cells to replace the cancerous ones. They are also trying to control the growth of stem cells in the liver to keep them from becoming cancer cells.
Before diving into this research, let's first make sure we know exactly what stem cells are. Once we know this, we can see how they can help with liver cancer.
Stem Cells are Different from Other Cells
Our body is made up of many different kinds of cells. There are muscle, nerve, and blood cells, just to name a few. Once these cells are formed, they can't change their type -- a muscle cell will always be a muscle cell. These cells also can't replace themselves once they die.
Stem cells are different. They can turn into many different kinds of cells and they can also replace themselves. This is how cells are replenished in our bodies. Stem cells make new copies of themselves that turn into other kinds of cells.
All stem cells are not created equal though. Some stem cells can become any other kind of cell. These are embryonic stem cells.
Other stem cells only become a few different kinds of cells. These are called adult stem cells.
We all have adult stem cells inside us. As I said, these cells are responsible for replacing worn out parts of our bodies.
For example, blood stem cells are constantly making new blood cells and skin stem cells are replacing skin cells. However, these cells can't truly become any other kind of cell. For example blood stem cells will generally only become blood cells.
Embryonic stem cells on the other hand are truly versatile, able to become any cell type. But these cells have been highly controversial as getting them involves destroying an embryo.
As a result scientists have been focusing on adult stem cells in their research. It is adult stem cells that have been used so far in helping treat and understand cancers.
Treating Cancer with Adult Stem Cells
Adult stem cells have actually been used for years to treat some cancers. Most people have heard of bone marrow transplants. These are actually just blood stem cell transplants. Doctors have been treating blood cancers like leukemia with bone marrow transplants for many years.
Other cancers have not proven as "easy" to treat with adult stem cells as has leukemia. This includes liver cancer.
Liver cancer is one of the most common cancers and has been especially hard to treat. Recently though, scientists have been able to make some advances using adult stem cells.
Right now the main treatment for liver cancers is to cut the cancerous parts out of the liver. This works well because the liver is a special organ which can actually regrow itself. As a result, surgeons can remove most of the liver and the rest will grow back and work normally.
Unfortunately, most liver cancers spread too fast and through too much of a patient's liver. The cancer can no longer be removed by surgery because there wouldn't be enough liver left behind.
Some German surgeons at the University of Dusseldorf were recently able to treat patients who had this kind of liver cancer. They injected blood stem cells into the patients' livers to grow more liver cells. Now even after surgery there is enough liver left behind. This treatment offers hope for those affected with severe liver cancers.
We can also learn new ways to treat cancers by studying stem cells. This is because stem cells and cancer cells are very similar.
Stem Cells and Cancer are a lot Alike
Just like stem cells, cancer cells can develop into different cell types and grow continuously. Studying stem cells to understand what makes them grow could help us find ways to control cancer cells.
There is an even closer connection between stem cells and cancer. More recently, a small number of stem cells have been found in tumors.
These 'cancer stem cells' could explain how cancers can regrow and spread even after being treated with chemotherapy. The idea is that the anticancer drugs kill most of the cancer but leave the cancer stem cells behind. To prevent these tumors from spreading, new drugs would need to be designed to target cancer stem cells specifically.
A small population of these liver cancer stem cells was identified in liver cancers. Georgetown university researchers found that these cells were very similar to liver stem cells. However, they were different in a key protein, TGF-Beta. This protein normally controls stem cell growth. Without this protein to apply the brakes, these liver stem cells grow uncontrollably and become cancerous.
These researchers also used mice to study liver cancer. When they removed key stem cell proteins from the mice, these mice had a lot less liver cancer. Basically, by blocking stem cells from growing continuously, they were also able to block cancer cells from forming.
Of course, we can't just remove stem cells proteins from humans, as this would affect the normal replacement of our worn-out cells. Instead, the researchers plan to use drugs to block the stem cell properties of just the liver cancer cells. They plan to target proteins specific to liver cancer stem cells, in order to prevent just these cells from growing. Their early results in mice have been promising, and offer hope for novel ways to treat liver cancer.
Sandeep Ravindran, Stanford University