“Self-healing” is not a word that people usually associate with cancer. But researchers studying a very unusual and rare form of skin cancer that can clear up by itself have learned some lessons that could potentially lead to new treatments for the disease in the future.
It's a rare hereditary cancer called multiple self-healing squamous epithelioma, or MSSE for short – it only affects a handful of people every year in the UK, and most of them can trace their ancestry to a single family from Scotland. The disease causes large flat tumours on the skin which heal up of their own accord, leaving disfiguring scars but no other lasting effects.
Because of the inheritance pattern of the disease, scientists know that it must be caused by a fault in a single gene, but the identity of this gene has been a mystery for more than 40 years. But now an international team of researchers led by Cancer Research UK's Dr David Goudie in Dundee have found the culprit. The team have published their findings in the journal Nature Genetics this week, and their discovery could shed light on more common types of cancer as well.
The researchers looked at DNA samples from around 60 people with MSSE, and compared them with DNA from more than a hundred of their relative who were unaffected. They focused in particular on a region of DNA that had previously been shown to harbour the likely gene, narrowing down their search until they found the gene TGFBR1.
This gene encodes a receptor protein, which receive signals from a protein called TGF beta. These signals tell cells to divide, or to stop dividing, and the researchers were able to prove that carrying a faulty version of TGFBR1 caused people to develop MSSE tumours. Intriguingly, faults in TGF beta signalling have been found in many types of cancer.
TGF beta signalling is very interesting to cancer researchers, because it can be both a 'goodie' and a 'baddie' in the disease. In the early stages of more normal cancers, it tells cells to stop dividing, acting as a brake on tumour growth. But after a while, it switches sides, and TGF beta signals tell cells to divide and grow faster, fuelling the growth of cancer.
But in the case of MSSE, the opposite seems to happen. Cells start off growing out of control, forming the characteristic skin tumour, but then they stop growing and go into reverse.
TGFBR1 is just one of a family of receptors that are involved in receiving TGF beta signals. The researchers think that the pattern of signals must be changing as the tumours grow and then heal, allowing the 'good' side to come forward.
Although MSSE is a very rare and unusual cancer, this discovery could shed light on other, more common, types of cancer, because we know that TGF beta signalling is involved in many types of cancer. If researchers could figure out exactly how the changes in TGF beta signalling make MSSE tumours heal up, then maybe it could pave the way for future treatments for more common types of cancer. So this is a nice example of how research into a very unusual disease could have a much wider relevance.
Goudie, D. et al (2011). Multiple self-healing squamous epithelioma is caused by a disease-specific spectrum of mutations in TGFBR1 Nature Genetics DOI: 10.1038/ng.780