To explore a possible role of 5-Lox in prostate cancer stem cells, we observed that treatment with MK591, which specifically inhibits 5-Lox activity by binding with FLAP or 5-lipoxygenase-activating protein [32–36], dramatically decreases the viability of PCSCs in a clear dose- and time-dependent manner (Figure 2A–2E). This evidence concerns the gene ALOX5AP and prostate cancer.