A six-plex immunoassay comprising macrophage inhibitory cytokine-1 (MIC-1), carcinoembryonic antigen cell adhesion molecule-1 (CEACAM-1), osteopontin (OPN), melanoma inhibitory activity (MIA), spondin-1 (SPON1), and heat shock protein 27 (HSP27) demonstrated a potential advantage over Ca19–9 alone in the early detection of PDAC [37]. Here, SPP1 is linked to melanoma.