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Targeting and amplification of immune killing of tumor cells by pro‐Smac
Author(s) -
Li Rui,
Rüttinger Dominik,
Urba Walter,
Fox Bernard A.,
Hu HongMing
Publication year - 2003
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.11655
Subject(s) - cytotoxic t cell , granzyme b , granzyme , ctl* , fusion protein , biology , immune system , perforin , microbiology and biotechnology , caspase , cancer research , apoptosis , cytotoxicity , chemistry , programmed cell death , immunology , t cell , in vitro , recombinant dna , biochemistry , gene
Overexpression of inhibitors of apoptosis (IAP) is one potential mechanism for tumor cells to evade immune surveillance. To determine whether immune‐mediated killing of tumor cells can be enhanced by neutralization of IAP proteins, 2 novel eGFP‐Smac fusion proteins (pro‐Smac) were introduced into the poorly immunogenic mouse melanoma cell line, B16BL6‐D5 (D5). Each fusion protein contained Smac and a cleavage site specific for granzyme B (GrB) or caspase 8, thereby targeting the 2 major killing mechanisms of cytotoxic T‐lymphocyte (CTL) and NK cells. Expression of a pro‐Smac fusion protein by D5 tumor cells greatly enhanced the susceptibility to killing by lymphokine‐activated killer (LAK) cells or purified GrB. GrB‐mediated killing was increased to a much greater extent when tumor cells expressed the eGFP‐Smac fusion protein with a GrB cleavage site compared to a caspase 8 cleavage site. In contrast, perforin‐deficient LAK cells, which lack GrB‐mediated cytotoxicity but process normal ligands for death receptors, killed D5 tumor cells expressed pro‐Smac with caspase 8 cleavage site more efficiently. Enhanced killing by GrB was also accompanied by processing of the fusion protein and increased caspase‐3‐like activity. These results indicate that killing of tumor cells can be amplified by targeting cell‐mediated cytotoxic mechanisms via expression of pro‐Smac fusion proteins. © 2003 Wiley‐Liss, Inc.