Melanoma-initiating cells identified by study by Krista Conger, News release, Stanford School of Medicine, June 30, 2010. Excerpt:

Scientists at the School of Medicine have identified a cancer-initiating cell in human melanomas. The finding is significant because the existence of such a cell in the aggressive skin cancer has been a source of debate. It may also explain why current immunotherapies are largely unsuccessful in preventing disease recurrence in human patients.

The news release is about this publication: Human melanoma-initiating cells express neural crest nerve growth factor receptor CD271 by Alexander D Boiko and 11 co-authors, including Irving L. Weissman, Nature 2010(Jul 1); 466(7302): 133-7. [FriendFeed entry].

A blog post about this same publication is: Stanford scientists identify a melanoma-initiating cell by Krista Conger, Scope blog, Stanford School of Medicine, June 20, 2010.

See also a commentary about the publication: Cancer stem cells: Invitation to a second round by Peter Dirks, Nature 2010(Jul 1); 466(7302): 40-1. Excerpt:

Boiko et al. study a type of human skin cancer called melanoma and, in particular, cancer cells enriched in a stem-cell marker called CD271. They find that, unlike other cells from the same tumour, CD271-expressing (CD271+) cells could initiate and maintain tumour growth in vivo — an observation consistent with the existence of a melanoma-cell functional hierarchy.

This finding reflects a view different from that of an earlier study by Quintana et al.[3], which demonstrated that, in some cases, as many as 50% of human melanoma cells have tumorigenic potential. In addition, no marker tested identified a tumorigenic subpopulation. The authors[3] concluded that the frequency of cancer cells that can initiate tumorigenesis depends, in part, on the assessment techniques and assays.

Another news item, based on the same publication, is: New hope in fight against skin cancer as deadly 'master cells' are identified for first time, Mail Online, July 1, 2010. Excerpt:

However Dr Alexander Boiko, who made the discovery at Stanford University, said the newly discovered 'stem cells' in advanced skin cancers were often missed by conventional immunotherapy.

'Without wiping out the cells at the root of the cancer, the treatment will fail,' he said.

Comments: Boiko et al. and Dirks suggest reasons why results different from those of Quintana et al. were obtained. One possibility is that the melanomas that the latter authors studied were at an advanced stage. If, as a cancer progresses, more cells acquire the attributes of cancer stem cells, then advanced melanomas may contain very high frequencies of tumorigenic cells.

As Boiko et al. point out in their publication, "The most crucial test of the tumour stem cell hypothesis is that markers or pathways restricted to tumour stem cells can be targets for curative therapies in the patient, which has not yet been done."