When different kinds of cancer are tackled, tumors may shrink in reaction to treatments including chemotherapy, but there is often the possibility of them springing back.
Some scientists believe that regrowth occurs because chemotherapy fails to eradicate a small number of cells, known in the field tentatively as 'cancer stem cells'. It may be the case that these kinds of cells perform the same function in all cancers that create solid tumor masses.
The suspicion of stem cell cancer cells has long been an aspect of research in the field, but the hypothesis has remained controversial -- mainly due to the artificial environments that most studies have taken place in, where human cells are transplanted into mice.
Now, studies on three different kinds of cancerous tumor has suggested a key reason why certain types of cells play a part in regrowth -- stem cells that fuel the cancer and are not killed by standard therapies.
Published in the journals Nature and Science, the new studies conducted by three independent teams of researchers believe that this discovery may be a breakthrough in the field of cancer research.
Conducting tests on mice, so-called tumor stem cells were identified in the brain, skin and gut. In one case, researchers were able to prove that treating glioblastoma -- a fatal brain tumor -- with chemotherapy left behind these kinds of cells, and eventually this sparked regrowth.
Luis F. Parada, a molecular geneticist hailing from the University of Texas Southwestern Medical Center in Dallas, and author of one of the studies, said:
"Everything has a soft underbelly once you understand it well. With all the modern molecular techniques and modern approaches we have, we should be able to find their soft underbelly."
Each study used color markers to detect when tumor cells divided in the mouse hosts. By doing so, the researchers were able to detect which cells did not replicate -- and whether old cells can fuel regrowth, or it has to be stem cell subsets.
Robert Weinberg, a biology professor at MIT who was not involved in the new studies said:
"What these three papers have done, through elegant strategies, is demonstrate, indeed there are cancer stem cells. It makes it more and more difficult for people to doubt the existence of cancer stem cells."
Image credit: Duncan Hull