PROM1 and cancer: iHMGB1+ resulted in significant upregulation of mRNA and protein expression of stem cell markers (Oct4, Sox2, and Nanog) in CD133− cancer cells, their sphere-forming ability, as well as CD133+ cell percentage 7 days post coculture, which were comparable to 250–300 ng/mL rhHMGB1 (Fig. 2a–d).