When cultured using stringent conditions in specially-formulated serum-free tissue culture medium with epidermal growth factor and basic fibroblast growth factor, tumor cells grew non-adherently in clumps of cells rather than as monolayers and cells in these tumor-derived “neurospheres” (Figure 1) expressed genes characteristic of neural stem cells including CD133, the transcription factor Sox2, and nuclear and cytoplasmic proteins musashi-1and bmi-1. Here, PROM1 is linked to neoplasm.