Several previous studies have demonstrated the tumor-suppressive effects of PACAP38 in a variety of cancers, including breast cancer and gliomas, although studies on the downstream mechanisms of tumor suppression by PACAP38 are far from sufficient (D'Amico et al., 2013; Cochaud et al., 2015; Maugeri et al., 2016). The gene discussed is ADCYAP1; the disease is breast cancer.