A mouse brain contains a glioma (green) three weeks after being injected with a virus that targeted mature astrocytes and altered the expression levels of two oncogenes, HRasV12 and p53. GFAP expression (red) reveals reactive astrocytes surrounding the tumor. Credit: Dr. Eric Bushong
Researchers from the US and Japan have shown that an aggressive type of brain tumor can arise from normal cells in the central nervous system such as neurons. The cells revert to an earlier, undifferentiated stem cell stage, which can then reproduce prolifically.
The international team of scientists, led by Professor Inder Verma and geneticist Dr Dinorah Friedmann Morvinski, both of the Salk Institute for Biological Studies at La Jolla in California, studied the development of malignant glioblastoma tumors in mice. They had earlier developed a new method of researching cancer by using viruses to introduce cancer-causing genes (oncogenes) into the mice brains, as reported in Phys.Org.
Many of the mouse studies on cancer revolve around transplanting human tissue or cancer cells into immune-compromised mice to begin the process of tumor formation, but this is not the way that real tumors develop in humans. The San Diego team therefore designed a new method, which aimed to imitate the appearance of random mutations by transferring novel oncogenes to healthy mouse cells via genetically modified viruses.
In the new study, they also introduced oncogenes via viruses, and when tumors began to form they then transferred some of the cells to the brains of healthy mice. They discovered that only as few as 10 cells were needed to produce a tumor in the healthy brain. Scientists had earlier assumed glioblastoma tumors only arose from glial cells, which support and protect the neurons and supply them with nutrients and oxygen. When stem cells were discovered within the brain, they were also implicated as being capable of leading to cancer cells.
The new research shows that tumors can in fact have their origins in several types of differentiated cells in the central nervous system, including neural stem cells, astrocytes (a sub-type of glial cell) and even neurons, when cancer-causing genes are introduced. Neurons do not divide, but when the genes were introduced they were found to transform into stem cells that could reproduce rapidly. Via New study finds brain tumors can arise from neurons.
