Cancer stem cells – a promising avenue for cancer research

Are rogue stem cells the root cause of cancer?

Cancer ‘stem cells‘ are a recurring topic on this blog. Many scientists think that these are the cells at the source of tumours, drive and renewing cancers yet resistant to treatment.

Last Saturday’s Guardian contained an excellent feature article by US cancer specialist Siddhartha Mukherjee, discussing what the future holds for cancer research. It’s quiet long but well worth reading.

Like many researchers, Mukherjee believes that one day we will eventually transform cancer into a long-term, manageable disease. As he writes:

In the past, cancer was typically imagined as an acute disease, treated with surgery, radiation and chemotherapy. And the trifecta of assaults led to only two possible outcomes. Either cancer was eradicated from the body – in other words “cured” – or it remained recalcitrant to treatment, and was “incurable”. The metaphors attached to cancer followed this binary outcome. Patients fought a “battle” with cancer. If cancer was defeated, then patients “won” the war. If patients lost the battle, the cancer was victorious. There was no intermediate outcome – no truce.

But for many forms of cancer, this binary description no longer captures the truth. Take, for instance, a young woman with breast cancer. She may initially have surgery to remove the primary tumour from her breast. But we now know that surgical removal of the tumour may not cure such a patient outright. Microscopic deposits of cancer cells may be left behind after surgery that can be eradicated only with chemotherapy and radiation, typically administered over several months. And more drugs and treatments might follow. If her cancer is of a particular subtype, she may receive anti-oestrogen therapy for several years.

During this time, and for decades after, she may be tested with mammography to detect early breast cancer in her other breast. Her daughters may be tested for carrying genes that predispose to breast cancer. Indeed, her course of therapy might stretch into five or even 10 years, perhaps even to the next generation…. Cancer will become a chronic condition for her; [and] the combination of surgery, chemo and radiation will likely extend her survival… cancer will become the new “normal”.

A big part of this, according to Mukherjee, will involve understanding more about cancer stem cells: what they are, where they come from, and how they drive the disease.

In the mid-1990s, John Dick, a Canadian biologist working in Toronto, postulated that a small population of cells in human leukaemias also possess this infinite self-renewing behaviour. These “cancer stem cells” act as the persistent reservoir of cancer – generating and regenerating cancer infinitely. When chemotherapy kills the bulk of cancer cells, a small remnant population of these stem cells, thought to be intrinsically more resistant to death, regenerate and renew the cancer, thus precipitating the common relapses of cancer after chemotherapy.

Indeed, cancer stem cells have acquired the behaviour of normal stem cells by activating the same genes and pathways that make normal stem cells immortal – except, unlike normal stem cells, they cannot be lulled back into physiological sleep. Cancer, then, is quite literally trying to emulate a regenerating organ – or perhaps, more disturbingly, the regenerating organism. Its quest for immortality mirrors our own.

It’s now becoming clear that by understanding the nature and identity of these stem cells, we could – theoretically at least – put the brakes on them and stop the disease in its tracks.

Turning theory into practice is what we aim to do here at Cancer Research UK, and the exciting field of stem cell research is no exception. That’s why last week we announced that we’ve hand-picked a crack team of experts, already dubbed the ‘C-Team’,  to focus on cancer stem cell research.

We’re backing this team, more formally known as the Cancer Stem Cell Consortium, with £500,000 over two years, which they’ll be using to look for ways to spot cancer stem cells, monitor their activity, and target them with drugs.

We wish them every success in their quest.

Henry

• More about our work on stem cells