Cancer Research in Switzerland - Krebsliga Schweiz

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“hierarchical structure” of a tumour, which had its
origins in one cancer stem cell from which all other
tumour cells derived.
Cancer stem cells – a new perspective in research
and therapy
With the discovery and experimental investigation of
cancer stem cells, the way of looking at how cancer
could be treated must be reconsidered. Namely, traditional
therapy strategies cannot or can only insufficiently
reach cancer stem cells. For example, chemotherapies
aim to stop the growth and survival of the
cancer as a whole. But cancer stem cells appear to
possess a specific protective mechanism that allows
them to send toxic chemical substances out of the
cell. And so, chemotherapies seem to destroy a large
part of the tumour cells – but without being able to
get to the root of the actual cause of the carcinogenesis.
Cancer recurrence following chemotherapy
could therefore be due to just a few cancer stem cells
surviving in the patient’s body.
For this reason, cancer stem cell research must find
new ways to fight cancer. Here the focus is on targeted
destruction of the cancer stem cells producing
the tumour. But methods are also being tested that
specifically block the cell division of cancer stem cells
or that accelerate their differentiation into less malignant
cells. To be able to implement these new types
of strategies of cancer therapy, research is needed on
the molecular and cellular characteristics and growth
conditions of cancer stem cells in different tumour
types. As for normal stem cells, it can also be assumed
for cancer stem cells that their characteristics,
their growth conditions, and their potential for
spreading are dependent upon the tissue of origin
and thus on the type of cancer.
Cancer stem cells have already been demonstrated in
various types of cancer in different organs, such as
breast cancer, colon cancer, brain tumours, different
forms of blood cancer (leukaemias) and some other
cancers. Depending on the cancer type and on the
patient, cancer stem cells in the tumour tissue appear
to differ in number. In our research, we are mainly
studying malignant skin cancer (melanoma). This
type of cancer is extremely aggressive, and the incidence
rate of melanoma is rising. Melanoma develops
from a malignant change in melanocytes, which
are pigment cells and, in developmental biology, develop
from what is called the neural crest. The neural
crest is a structure in the embryo with great development
potential. Not only pigment cells but also
nerve cells in the peripheral nervous system, for example,
and facial cartilage and bones derive from the
neural crest. To be able to build these structures,
neural crest stem cells must divide substantially and
move across long distances in the embryo.
Since pigment cells in the skin also derive from neu­
ral crest stem cells, we raised the question as to
whether these normal stem cells could have something
to do with the cause of skin cancer. We supposed
that possible cancer stem cells in the melanoma
could show the characteristics of normal
neural crest stem cells. That kind of connection could
also explain why melanoma cells are so aggressive –
why they can multiply so strongly and spread through
tissue to form metastases. And in fact, in numerous
melanoma biopsies we found cells that clearly
showed the features of neural crest stem cells. In