Emerging evidence suggests that PACAP–PAC1 signalling may influence melanoma progression by enhancing MAPK- and cAMP-driven transcriptional programmes that support tumour growth, by modulating cytoskeletal dynamics through PKC and calcium signalling and by interacting with immune-regulatory mechanisms that can facilitate tumour invasion and immune evasion. The gene discussed is ADCYAP1R1; the disease is neoplasm.