These have included interleukin (IL)-7 and chemokine (C-C motif) ligand 19 (CCL19) to recruit endogenous anti-tumor immune cells [32], a PD-1-CD28 switch [33], and scFv-PD-1 secretion [34] to reduce immune suppression in the tumor microenvironment and Bispecific T cell engager (BiTE) secretion to prevent tumor heterogeneity-induced tumor escape [35]. The gene discussed is PDCD1; the disease is neoplasm.