Overall, the preclinical and clinical data suggest the protective role of PDE inhibitors as adjuvant agents for chemopreventive and chemotherapeutic treatments, due to their ability to facilitate drug transport, inhibit drug efflux (via inhibition of MDR transporters), and enhance apoptosis and anti-tumor immune response through the recruitment of intratumoral T lymphocytes. This evidence concerns the gene ALDH7A1 and neoplasm.