Cells with high ALDH activity have been proposed to have tumor-initiating activity in several solid cancers including colon, breast, liver, ovarian and pancreatic cancer [34], but in the present study ALDH activity-based selection did not enrich for PC3 cells with enhanced self-renewal in vitro (Table 3) or enhanced tumor-initiating ability in vivo (Supplementary Table S1). This evidence concerns the gene LDHA and neoplasm.