To determine if the transplanted tumor cells contained stem-like cells, we evaluated the expression of the CSC marker, Sox2 [19], and found that 25.9 percent of transplanted CSCs and their descendants (YFP cells) were Sox2 positive as compared to 0.1 percent of non-stem tumor cells and their descendants (CFP cells, Fig. 4A, B). The gene discussed is CFP; the disease is neoplasm.