As you may know, the discovery of tumor stem cells has been one of the bigger breakthroughs in understanding why tumors are resistant to current therapies. Here are two articles on some important findings on the effect of tumor stem cells and the highly refractory brain tumor, glioblastoma multiforme.
http://www.sciencedaily.com/releases/2010/07/100706103410.htm
http://www.sciencedaily.com/releases/2012/04/120422134800.htm#.T5RvBvbXTU8.facebook
http://www.sciencedaily.com/releases/2010/07/100706103410.htm
http://www.sciencedaily.com/releases/2012/04/120422134800.htm#.T5RvBvbXTU8.facebook