CD44 and cancer: To exclude the possibility that what we were calling “cancer-derived hiPSCs” might actually represent simply an enrichment and expansion of the small population of highly tumorigenic cells known as cancer stem cells (CSCs) that populate many solid tumors (Ma et al., 2014; Nagayama et al., 2016; Todaro et al., 2010), we analyzed the parental cancer population and their respective reprogrammed RAS-inhibited hiPSCs for the most commonly accepted CSC markers, CD44 and CD133, using flow cytometry.