The theory is that cancer stem cells are a rare ‘ruling elite’, buried deep within a tumour. Despite their scarcity, they’re the cancer’s root cause, producing most of the ‘bulk’ cells that make up a tumour. While these non-stem cells can be killed off by cancer treatments, cancer stem cells may be more resistant. They could linger in the body and cause the disease to return years after treatment.
Cancer stem cells are thought to be rather different from normal, healthy stem cells, which play a vital role in producing many specialised cells in the body, and are essential for our well-being. One theory is that cancer stem cells could be healthy stem cells that have ‘gone rogue’.
But in a provocative lecture on Tuesday morning, Dr Bob Weinberg suggested that ordinary cancer cells might sometimes be able to acquire the superpowers that are a hallmark of stem cells, turning the cancer stem cell theory on its head.
It’s clear that this exciting field is constantly evolving, and as well as Dr Weinberg’s keynote address, we heard from other researchers who are pushing the boundaries in this field.
The previous day, Professor Tariq Enver of the UCL Cancer Institute chaired a session called ‘Stem Cells and Cancer’, and opened proceedings by posing some intriguing questions. Are there very clear differences between stem cells and ‘bulk’ cancer cells that could give us clues for new treatments that specifically target the stem cells? And how can researchers find better ways to identify stem cells in different cancers?
Understanding healthy stem cells
The session’s first talk came from Dr John Stingl , who is studying healthy breast stem cells in mice at Cancer Research UK’s Cambridge Research Institute . He described his research into the complicated ‘family tree’ or hierarchy of stem cells – how these powerful cells produce the many specialised cell types that make up breast tissue.
So far his team has identified three key branches on this family tree, each producing different types of breast cell. He now plans to find out if this hierarchy in mice can also be found in human breast tissue. If so, this could yield clues to how different types of breast cancer develop, helping to uncover key weaknesses in cancer cells that could be exploited to treat the disease.
Here’s a short interview with Dr Stingl, exploring stem cells and their role in cancer.
Stem cells and leukaemia
Next, Dr Tim Somervaille from the Paterson Institute in Manchester covered a fruitful area of stem cell research – understanding how these cells are involved in acute myeloid leukaemia (AML) in animal models of the disease.
These models are helping researchers to uncover the key molecular and genetic changes that distinguish ‘leukaemic’ stem cells from the healthy stem cells that produce normal blood cells. This high-stakes game of ‘spot the difference’ is aimed at finding drugs that home in on leukaemic stem cells while leaving healthy cells unharmed. Dr Somervaille’s team is developing ever more refined animal models, and this should allow them to accurately identify and understand the cells at the heart of leukaemia.
Do stem cells play a role in ovarian cancer?
Lastly the discussion moved to ovarian cancer. This disease fits the theory of cancer stem cells – it responds well to treatment at first, but can often return months or years later. Could this be because a tough group of stem cells survive treatment and produce more ‘bulk’ cancer cells later on?
Dr Ben Neel from the Ontario Cancer Institute in Toronto, Canada, described how his team had identified tumour-initiating cells, or ‘TICs’ – cells that can kick-start ovarian cancer. It’s not clear if these are true cancer stem cells or ‘stem-like’ cells, but either way they play a key role in fuelling the disease. Dr Neel’s search for TICs in samples taken from women with ovarian cancer has uncovered some key molecular ‘markers’ that can be used to track these cells down.
But unlike in leukaemia, where the same genetic changes are found in most cases of the disease, these markers aren’t found in all ovarian TICs. Results so far also suggest that TICs change and evolve over time, meaning it could be hard to target them with specific drugs. However, there could be different groups of TICs that fuel different types of ovarian cancer – more research will tell us if this theory could help doctors to personalise treatment for the disease.
Cancer stem cells have lost none of their interest and are still a hot topic of research. Big questions remain to be answered, and we look forward to hearing about the progress in understanding these mysterious cells at next year’s conference.