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Stanford scientists identify a melanoma-initiating cell

There's exciting news (subscription required) in the current issue of Nature. Researchers at Stanford have identified something that looks suspiciously like a cancer stem cell in melanoma. Post-doctoral fellow Alexander Boiko, PhD, says that the finding may explain why current immunotherapies against the disease are largely unsuccessful:

These cells lack the traditional melanoma cell surface markers targeted by these treatments. Without wiping out the cells at the root of the cancer, the treatment will fail.

The cancer stem cell theory holds that, like queen bees in a hive, only a subset of cancer cells are at the root of the tumor’s growth. These cells can both self-renew (that is, make more of themselves) and differentiate into other tumor cell types.
Any therapy that doesn’t wipe out these elite cancer stem, or initiating, cells has no chance of completely eradicating the disease even if it destroys nearly all other tumor cells. That’s why, say proponents, it can be relatively easy to get a patient into remission, but extremely difficult to prevent the cancer stem cells from roaring back and causing a relapse months or years later.

Boiko conducted his research in the laboratory of stem cell researcher Irving Weissman, MD. The finding is noteworthy because previous research had suggested that melanomas, unlike several other solid cancers such as breast, brain, bladder and colon, may not have a true cancer stem cell.

Still, it's true that individual cancers may be different. In an accompanying News and Views article in the same issue of the journal, neurosurgeon and stem cell researcher Peter Dirks, MD, PhD, from the Hospital for Sick Children in Toronto warns that the data from all these studies must be carefully interpreted:

The field of cancer-stem-cell research is young and emerging, so it is not surprising that many questions remain. Each study must be carefully assessed, particularly when considering the experimental methodology and models used. One point that should always be borne in mind is the relevance of a study to tumour growth in patients.

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