Because the drug-tolerant Du145 cells have undergone multiple epigenetic changes (Fig. 8), understandably, CD44 overexpression alone can only partially restore the tumorigenic potential of Du145-VP16 cells and CD44 knockdown in parent Du145 cells, despite inhibiting cell proliferation and tumor regeneration, does not render cells resistant to drugs (Chen et al., unpublished observations). The gene discussed is CD44; the disease is neoplasm.