Cancer stem cells sustaining the growth of mouse melanoma are not rare.

Cancer stem cell (CSC) is generally believed to be a very small proportion of tumor cells capable of initiating and sustaining growth of the tumor. Its existence is usually demonstrated by xenotransplanting human cancer cells in immunodeficient mice. In this paper, we report that the growth of B16-F10 melanoma cells in syngeneic mice could be maintained by a relatively larger proportion (>10%) of tumor cells. The result of this study does not seem to support the current view that cancer stem cells (CSCs) responsible for the sustainable growth of tumor are rare.