My blog reader/friend Paul raised a very interesting question, for which I didn’t have a satisfactory answer, so I asked the general MMA myeloma patients list (link here on the right-hand side). Based on his comment (see my recent post on zerumbone), my question was: do cancer stem cells die?
I received more or less the following answer (in italics; I edited small parts of it) from a list member/doctor who takes cyclopamine and knows a lot about stem cells:
Stem cells, whether healthy or cancerous, are supposed to last a lifetime. Do some die off? Yes. For instance, the main reason people age is that they gradually lose their healthy stem cells.
But cancer stem cells have a lot of telomerase, which keeps their telomeres long, and keeps them essentially immortal. 
Cyclopamine (extracted from the corn lily, see photo) causes the cancerous stem cells to differentiate and turn into mature cancer cells without making more copies of cancer stem cells. (Aha!)
Cyclopamine (extracted from the corn lily, see photo) causes the cancerous stem cells to differentiate and turn into mature cancer cells without making more copies of cancer stem cells. (Aha!)Now, mature cancer cells (plasma cells in myeloma) do die off. They are not immortal. So, in theory, if you kill off all the cancer stem cells, then eventually the cancer cells die, too. This is the basis of using cyclopamine.
Some research shows that some cancer cells may be able to turn back into cancer stem cells. That could be a problem, but if you target both the cancer stem cells and the mature cancer cells, then the problem is solved. Of course, continuous treatment of the cancer stem cell would also take care of the problem.
In a nutshell, then, cancer stem cells are immortal. But if we manage to block certain signalling pathways, we can turn them into mortal cancer cells. My haematologist said that myeloma cells may live for weeks or even months. That depends on a lot of factors. But eventually, they kick the bucket. This makes me wonder if zerumbone has the same effect that cyclopamine has on cancer stem cells…that is, does it turn them into regular cancer cells? Good question. No answer…yet.
Fascinating topic. In addition, Paul’s comment led me to make a series of connections that I had begun to make some months ago, but then had set aside only to rediscover this morning. Thank you so much, Paul!
Oh, I do hope my current bit of research will lead to some useful information. Okay, I have to go feed my cats now.