PROM1 and ovarian cancer: Thus, Silva et al. showed that ALDH activity is present in a small percentage of ovarian cancer cells; small number of ALDH+ cells or ALDH+/CD133+ cells are capable of initiating and propagating tumors in nude mice; CD133+ cells were detectable in only 50% ovarian cancer specimens; these cells are able to generate in immunocompromised mice xenograft tumors similar to the original tumors [207].