title: Blockade of the granzyme B/perforin pathway through overexpression of the serine protease inhibitor PI-9/SPI-6 constitutes a mechanism for immune escape by tumors.
abstract: The concept for cellular immunotherapy of solid tumors relies heavily on the capacity of class I MHC-restricted cytotoxic T lymphocytes (CTLs) to eliminate tumor cells. However, tumors often have managed to escape from the cytolytic machinery of these effector cells. Therefore, it is very important to chart the mechanisms through which this escape can occur. Target-cell killing by CTLs involves the induction of apoptosis by two major mechanisms: through death receptors and the perforin/granzyme B (GrB) pathway. Whereas tumors previously were shown to exhibit mechanisms for blocking the death receptor pathway, we now demonstrate that they also can resist CTL-mediated killing through interference with the perforin/GrB pathway. This escape mechanism involves expression of the serine protease inhibitor PI-9/SPI-6, which inactivates the apoptotic effector molecule GrB. Expression of PI-9 was observed in a variety of human and murine tumors. Moreover, we show that, indeed, expression results in the resistance of tumor cells to CTL-mediated killing both in vitro and in vivo. Our data reveal that PI-9/SPI-6 is an important parameter determining the success of T cell-based immunotherapeutic modalities against cancer.
authors.affiliation: Department of Immunohematology and Bloodtransfusion, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands. medema@mail.medfac.leidenuniv.nl
authors.forename: J P
authors.initials: JP
authors.lastname: Medema
authors.forename: J
authors.initials: J
authors.lastname: de Jong
authors.forename: L T
authors.initials: LT
authors.lastname: Peltenburg
authors.forename: E M
authors.initials: EM
authors.lastname: Verdegaal
authors.forename: A
authors.initials: A
authors.lastname: Gorter
authors.forename: S A
authors.initials: SA
authors.lastname: Bres
authors.forename: K L
authors.initials: KL
authors.lastname: Franken
authors.forename: M
authors.initials: M
authors.lastname: Hahne
authors.forename: J P
authors.initials: JP
authors.lastname: Albar
authors.forename: C J
authors.initials: CJ
authors.lastname: Melief
authors.forename: R
authors.initials: R
authors.lastname: Offringa
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000276:immunology; D003110:Colonic Neoplasms / Q000276:immunology; D017931:DNA Primers; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D053804:Granzymes; D006801:Humans; D019476:Insect Proteins; D008545:Melanoma / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000276:immunology
chemical_list: D017931:DNA Primers; D019476:Insect Proteins; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D015842:Serine Proteinase Inhibitors; C425549:silk proteinase inhibitor 1, Galleria mellonella; D054353:Perforin; C509213:GZMB protein, human; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases