When it comes stem cell, most people might think about human cloning and the ongoing huge ethical debate (embroynic stem cell) etc. But actually there is another different type of stem cells-Cancer Stem Cells, which should have come to people's attention earlier.
People have gained great understanding of cancer from decades of research. But we only have limited success in cancer diagnosis and treatment, in general. So, there must be something fundamental and important which we haven't really understood about cancer. Cancer Stem Cell might be one of the answers.
Basically, the concept of cancer stem cell is that there is a very small population of cells in cancer which have the abilities to self-renew (create themselves) and to differentiate into other malignant cells. Also, because these cells always live very long time, they could potentially accumulate damages from various sources and eventually give rise to cancer cells. As a result, any kind of treatment, if these cells are not targeted, will not be successful.
Cancer stem cells have been been identified from a handful of cancers, e.g. breast cancer, brain cancer (glioma), prostate cancer, and many leukemia. Scientists are trying different ways to target these cells by either taking advantages of stem cell specific markers or engineering body's own immune system.
It might still be a long way until we conquer all cancers. But we are moving forward!!