PDE5A and neoplasm: Tadalafil is an important member of the PDE5 inhibitor family, and there were emerging evidences which have confirmed its anti-tumor effects (Serafini et al., 2006; Booth et al., 2014a; Booth et al., 2014b; Roberts et al., 2014; Califano et al., 2015; Sponziello et al., 2015; Wang et al., 2015; Weed et al., 2015; De Rose et al., 2016; Tuttle et al., 2016; Booth et al., 2017; Hassel et al., 2017; Califano et al., 2018).