Indeed, PDE5 inhibitors, sildenafil and vardenafil induced caspase-dependent apoptosis of B-cell chronic lymphocytic leukemia cells (Sarfati et al., 2003), whereas cytotoxic and growth suppressive effects in various breast cancer, prostate, and colon cells were seen with non-specific PDE5 inhibitors sulindac sulfone and its analogs (Thompson et al., 2000; Piazza et al., 2001; Whitehead et al., 2003; Tinsley et al., 2011). This evidence concerns the gene PDE5A and breast cancer.