Highly efficient redirected anti-tumor activity of human lymphocytes transduced with a completely human chimeric immune receptor.
BACKGROUND
Novel antibody-based immunotherapeutic strategies exploit chimeric immune receptors (CIR), expressed on the surface of transduced human peripheral blood mononuclear cells (PBMC), to redirect potent non-MHC-dependent cytotoxicity to tumor cells expressing a tumor-associated antigen. However, clinical application of the strategy has been hampered by the potential side effects associated with immunogenicity and by low transduction efficiency.


METHODS
A fully human CIR was constructed that triggers immune activation through the zeta chain of CD3 and contains a human single-chain antibody fragment specific for an extracellular epitope of HER2. PBMC were transduced with the CIR using gibbon-ape leukemia virus envelope pseudotyped retroviruses. In vitro cytotoxicity and inhibition assays were carried out using normal and tumor cell lines expressing different levels of HER2.


RESULTS
Bulk populations of CIR-transduced PBMC could express high levels of the construct and subcloning ensured stable expression. CIR-mediated killing and growth inhibition of targets expressing high HER2 levels were very efficient at low effector-to-target ratios. Under the same experimental conditions, CIR-mediated activity against normal cells expressing low HER2 levels was marginal. The CIR-mediated recognition of target cells induced the release of soluble factors able to inhibit growth of both HER-positive and HER2-negative bystander tumor cells.


CONCLUSIONS
Human CIR-transduced PBMC exert a potent and dose-dependent anti-tumor activity. Target antigen level appeared to be a critical determinant of specificity and delivery of signals leading to redirected effector functions. Soluble factors, released by redirected effectors at the site of antigen-driven activation, mediate potent bystander killing.
Turatti
Fabio
F
Molecular Therapies Unit, Department of Experimental Oncology, Istituto Nazionale Tumori, Milano, Italy.
Figini
Mariangela
M
Alberti
Paola
P
Willemsen
Ralph A
RA
Canevari
Silvana
S
Mezzanzanica
Delia
D
D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D017252:CD3 Complex / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002860:Chromium Radioisotopes; D017931:DNA Primers; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics* / Q000627:therapeutic use; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000276:immunology / Q000378:metabolism; D007167:Immunotherapy / Q000379:methods*; D017989:Leukemia Virus, Gibbon Ape / Q000235:genetics*; D008214:Lymphocytes / Q000276:immunology / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000276:immunology / Q000628:therapy*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology / Q000378:metabolism*; D013778:Tetrazolium Salts; D013844:Thiazoles; D014161:Transduction, Genetic / Q000379:methods
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D002860:Chromium Radioisotopes; D017931:DNA Primers; D007135:Immunoglobulin Variable Region; D018719:Erb-b2 Receptor Tyrosine Kinases; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue