The cancer stem cell hypothesis suggests that a majority of cancers are driven and supported by a small population of errant stem cells, and that these cells are characteristic in ways allowing them to be identified and destroyed. Without the cancer stem cells, a cancer would whither. In other words, cancer stem cells offer the hope that there are in fact broad commonalities in the mechanisms of different forms of cancer, and that this fact will lead to a unified, single technology platform and robust cures for even late-stage cancers.
The existence and universality of cancer stem cells is a hotly debated topic in medical research, and rightly so for the reasons given above. Good evidence and arguments can be found on either side. Is cancer something that can be solved through a single mechanism or group of very similar mechanisms? Or only some cancers? Or only few cancers? These are important questions, and the answers, when they arrive, will tell us whether the prospects are for many cures arriving soon or for a slow and incremental flow of therapies over decades.
Today I noticed a good introductory popular science article that walks through the present state of research and scientific thought on this topic, and provides copious references along the way. You might find it interesting:
Take some cells from a tough-to-treat tumor, sort them, and inject each fraction into a different immunodeficient mouse, and only a small percentage of those cells will thrive and form tumors. This sort of experiment illustrates a concept that has been gaining traction within the cancer research community. Tumors contain a diverse mixture of cells, and only a handful of them can bounce back after treatment. That deadly minority can reproduce indefinitely and differentiate into a wide variety of cell types, just like stem cells. And often they express many of the same genes that are active in induced or embryonic stem cells and inactive in mature tissue.
The logic of pursuing therapies that might zero in on cancer stem cells is compelling to many. But the methods to evaluate such therapies' effectiveness, or to personalize cancer treatments according to stem cell markers, are not nearly as well developed. Without an array of proper markers, it's hard to tell whether drugs that target cancer stem cells are working as intended. ... Things are looking up for genetic analysis, but the poor reliability of cancer stem-cell-surface markers remains a confounding problem. For nearly a decade, biologists have known that antigens such as CD133 can be found on the surfaces of cancer stem cells. But these markers are not particularly specific.
But for solid tumors, which account for about 85% of all cancer diagnoses, the search for such stem-cell-surface markers is still in the early days. In such [cancers] cell-surface markers can vary from one type of cancer to another or even from one cell within a tumor to another. Until better markers are discovered [the] cancer stem cell field will remain somewhat embryonic.