CD44 and neoplasm: Our strategy was to utilize an established, clinically-relevant model of human PCSCs to interrogate the mechanisms of stem cell vulnerabilities and to find effective measures for controlling the population of PCSC which express both pluripotency markers (Nanog, c-Myc and Sox2) as well as the tumor-progenitor markers (CD44, CD133, and ALDH1) [27–29].