title: EGFR-targeted granzyme B expressed in NK cells enhances natural cytotoxicity and mediates specific killing of tumor cells.
abstract: Natural killer (NK) cells are highly specialized effectors of the innate immune system that hold promise for adoptive cancer immunotherapy. Their cell killing activity is primarily mediated by the pro-apoptotic serine protease granzyme B (GrB), which enters targets cells with the help of the pore-forming protein perforin. We investigated expression of a chimeric GrB fusion protein in NK cells as a means to augment their antitumoral activity. For selective targeting to tumor cells, we fused the epidermal growth factor receptor (EGFR) peptide ligand transforming growth factor α (TGFα) to human pre-pro-GrB. Established human NKL natural killer cells transduced with a lentiviral vector expressed this GrB-TGFα (GrB-T) molecule in amounts comparable to endogenous wildtype GrB. Activation of the genetically modified NK cells by cognate target cells resulted in the release of GrB-T together with endogenous granzymes and perforin, which augmented the effector cells' natural cytotoxicity against NK-sensitive tumor cells. Likewise, GrB-T was released into the extracellular space upon induction of degranulation with PMA and ionomycin. Secreted GrB-T fusion protein displayed specific binding to EGFR-overexpressing tumor cells, enzymatic activity, and selective target cell killing in the presence of an endosomolytic activity. Our data demonstrate that ectopic expression of a targeted GrB fusion protein in NK cells is feasible and can enhance antitumoral activity of the effector cells.
authors.affiliation: Chemotherapeutisches Forschungsinstitut Georg-Speyer-Haus, Frankfurt am Main, Germany.
authors.forename: Pranav
authors.initials: P
authors.lastname: Oberoi
authors.forename: Robert A
authors.initials: RA
authors.lastname: Jabulowsky
authors.forename: Hayat
authors.initials: H
authors.lastname: Bähr-Mahmud
authors.forename: Winfried S
authors.initials: WS
authors.lastname: Wels
mesh_terms: D017209:Apoptosis; D015550:Cell Degranulation; D002470:Cell Survival; D003602:Cytotoxicity, Immunologic; D016503:Drug Delivery Systems; D066246:ErbB Receptors / Q000378:metabolism*; D015870:Gene Expression; D053804:Granzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007167:Immunotherapy; D019169:Jurkat Cells; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D011993:Recombinant Fusion Proteins; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D053804:Granzymes