Iterative sorting reveals CD133+ and CD133- melanoma cells as phenotypically distinct populations

Background: The heterogeneity and tumourigenicity of metastatic melanoma is attributed to a cancer stem cell model, with CD133 considered to be a cancer stem cell marker in melanoma as well as other tumours, but its role has remained controversial. Methods: We iteratively sorted CD133+ and CD133- cells from 3 metastatic melanoma cell lines, and observed tumourigenicity and phenotypic characteristics over 7 generations of serial xeno-transplantation in NOD/SCID mice. Results: We demonstrate that iterative sorting is required to make highly pure populations of CD133+ and CD133- cells from metastatic melanoma, and that these two populations have distinct characteristics not related to the cancer stem cell phenotype. In vitro, gene set enrichment analysis indicated CD133+ cells were related to a proliferative phenotype, whereas CD133- cells were of an invasive phenotype. However, in vivo, serial transplantation of CD133+ and CD133- tumours over 7 generations showed that both populations were equally able to initiate and propagate tumours. Despite this, both populations remained phenotypically distinct, with CD133- cells only able to express CD133 in vivo and not in vitro. Loss of CD133 from the surface of a CD133+ cell was observed in vitro and in vivo, however CD133- cells derived from CD133+ retained the CD133+ phenotype, even in the presence of signals from the tumour microenvironment. Conclusion: We show for the first time the necessity of iterative sorting to isolate pure marker-positive and marker-negative populations for comparative studies, and present evidence that despite CD133+ and CD133- cells being equally tumourigenic, they display distinct phenotypic differences, suggesting CD133 may define a distinct lineage in melanoma

The dynamics of R&D communities : implications for technology strategy

"Presented at the CORS/TIMS/ORSA Conference, May 8, 1989, Vancouver, Canada.

Bandwagons, bootlegging and grapevines : structural and behavioral dynamics in the formation of R&D communities : a research agenda

"May 1990, revised December 1990.""This paper was presented at the TIMS/ORSA Joint National Meeting in Las Vegas, Nevada, May 7, 1990.

An analysis of entry and persistence among scientists in an emerging field

"December 1991: Revised September 1992.

The social construction of technological reality : the case of cochlear implants

"January 1992.

Youth and scientific innovation : the role of young scientists in the development of a new field

"August 1992, Revised Sept. 1992.

Bootleggers and bandwagoners : a comparison of early and late entrants during the growth of a research community

"January 1991."Series from publisher's list