Study author Mark Prince, M.D., assistant professor of otolaryngology at the University of Michigan Medical School and section chief of otolaryngology at the VA Ann Arbor Healthcare System has said that

"This finding will impact our understanding of head and neck cancer, and we hope it will lead to treatments that will be more effective."

Results of the study appear in the Jan. 16 issue of the Proceedings of the National Academy of Sciences.

Researchers at the U-M Comprehensive Cancer Center and Stanford University School of Medicine took tumor samples from patients undergoing surgery for head and neck squamous cell carcinoma, including cancers of the tongue, larynx, throat and sinus. Cells from the samples were separated based on whether they expressed a marker on their surface called CD44. The sorted cells were then implanted into immune-deficient mice to grow tumors.

The cells that expressed CD44 were able to grow new tumors, while the cells that did not express CD44 did not grow new tumors. The tumors that grew were found to be identical to the original tumors and to contain cells that expressed CD44 as well as cells that did not express the marker. This ability to both self-renew and produce different types of cells is a hallmark of stem cells.

The current finding in head and neck tumors does not pinpoint the exact stem cells, the researchers believe, but rather narrows down the field. The percent of cells within a tumor expressing CD44 varied from one sample to the next, with one sample composed of as high as 40% of these cells. Studies in other cancer types have found the stem cell population to be smaller than 5%.

"The CD44-positive cells contain the tumorigenic cells, but we don’t think that’s a pure population of cancer stem cells. We still need to drill down further to find the subpopulation of those cells that is the pure version," Prince says.

In addition to Prince, U-M study authors were doctoral student Andrew Kaczorowski and Gregory Wolf, M.D., professor and chair of otolaryngology.
Stanford authors were Ranjiv Sivanandan, Michael Kaplan, M.D.; Piero Dalerba; Irving Weissman, M.D.; Michael Clarke, M.D.; and Laurie Ailles.

Funding for the study was from the U-M Specialized Program of Research Excellence (SPORE) grant in head and neck cancer and from an anonymous gift fund for cancer stem cell research at Stanford University.