In initial investigations of fusion receptor constructs comprised of PD-1 and the costimulatory protein CD28 transduced into transgenic murine CD8+ T-cells specific for ovalbumin (OT-1), complete tumor regressions in PDAC-carrying mice were observed with 300-fold increases in IL-2 and IFN-γ production and increased T-cell proliferation [39]. Here, CD28 is linked to neoplasm.