Researchers Hone in on Cancer Stem Cells fo...( For the first time researchers say ta...),Health

For the first time, researchers say targeting these units can slow down tumor growth

WEDNESDAY, Jan. 16 (HealthDay News) -- Melanoma has joined the list of cancers that can arise from a rare population of primordial cancer stem cells, Harvard researchers report.

Even more importantly, the scientists demonstrated for the first time that targeting these cells can slow down the growth of a tumor.

"The findings validate for the first time the potential therapeutic utility of the cancer stem cell concept," explained study author Markus Frank. "To my knowledge, cancer stem cells have not been specifically targeted to date via a prospective molecular marker."

Frank and his colleagues were interested in a particular protein called ABCB5, which is expressed on the surface of some progenitor skin cells and has been shown to confer cancer drug resistance to melanoma.

Hypothesizing that the pool of ABCB5-positive cells could include cancer stem cells, the researchers separated human melanoma cells based on whether or not they expressed ABCB5, transplanted both types of cells into mice, and monitored their ability to form tumors.

Fourteen of 23 mice injected with ABCB5-positive cells developed tumors, compared to one of 23 mice injected with cells that did not express the protein.

When a mixture of both types of cells were injected into mice, the authors found the ABCB5-positive cells were more likely to fuel tumors, and they exhibited stem cell-like properties -- that is, they divided to form both the bulk of the tumor and to regenerate the stem cells themselves.

Those findings -- that a stem cell subpopulation appears to contain the ability to reconstitute a tumor -- have been observed before in colon, brain, breast and pancreatic cancers, among others, albeit using a different cellular protein. However, the Harvard researchers added a novel twist: They showed both that ABCB5 expressi
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