PROM1 and neoplasm: To investigate whether the higher number of cells detectedby p-HTMI was merely the result of a less specific labeling, we comparedlabeling of the CD133 antibody and p-HTMI in the tumor cell line U-87MG,previously shown to contain a very small percentage of GSCs in cellculture.33 The number of cells detectedby the CD133 antibody as well as p-HTMI was much lower in the U-87MGcultures, and in these cells, the number of cells detected by theCD133 antibody was higher than that of p-HTMI (Figure 3d).