On the other hand, since EpoR has been described in established cell lines of several malignancies [8,11,22,23,25], though it may be barely detectable on cells isolated from primary tumors [67,68], we envision that it could be a novel marker of cancer stem cells, for example, in gonadal malignancies (e.g., ovarian cancer stem cells). The gene discussed is EPOR; the disease is cancer.