Cancer stem cell study finds genetic 'root' of disease

Definitive support for the existence of human cancer stem
cells has been found, according
to researchers at the University of
Oxford and the Karolinska Institutet in Sweden.

Cancer stem cells (CSCs) are a type of cancer cell
that have the ability to give rise to all the cell types within a tumour. CSCs
are thought to form the 'root' of the
cancer and are responsible for driving its growth and evolution. Their existence, however, has
been debated for decades by the scientific community, as clear
evidence of their appearance in human cancers has so far been
lacking.

'We have identified a subset of cancer cells [and]
shown that these rare cells are invariably the cells in which the cancer
originates', said study author Dr Petter
Woll, from the University of Oxford. 'It
suggests that if you want to cure patients, you would need to target and remove
these cells at the root of the cancer'.

Scientists investigated 15 patients with myelodysplastic syndromes,
where the bone marrow does not make enough healthy blood cells. Over time, MDS
can develop into a form of leukaemia called acute myeloid leukaemia (AML)
through an accumulation of specific genetic mutations.

The researchers took samples of the patients' bone marrow
at several points during the progression of the disease and identified
cancerous cells. By analysing genetic changes, they were able to track the
origin of mutations leading to cancer cell formation. They found a subset of
MDS cells that showed the distinctive markers of stem cells, which they
identified as CSCs as they were the only cell type that was able to fully
reproduce a tumour, supporting the theory that they function as 'roots'.

Current cancer treatments, like chemotherapy, aim to
reduce the overall size of the tumour. Chemotherapy attacks the cells that form
the bulk of the tumour, but might not reach the smaller population of CSCs,
which could then regenerate the tumour and cause a relapse of the disease.

'It's like having dandelions in your lawn. You can pull
out as many as you want, but if you don't get the roots they'll
come back,' explained Dr Woll.

CSCs have been found in a number of human cancers to date,
but the findings have remained controversial as the lab tests used in their
identification were thought to be unreliable.

'In our studies, we avoided the problem of unreliable lab
tests by tracking the origin and development of cancer-driving mutations in MDS
patients', said study lead Professor
Jacobsen.

The results
are promising but should be interpreted with caution as these results are
limited to the MDS and might not be applicable to other forms of cancer. Dr Woll noted: 'We can't offer patients today new
treatments with this knowledge. What it does is give us a target for the
development of more efficient and cancer stem cell specific therapies to
eliminate the cancer'.