Targeting gastrin-releasing peptide receptors on small cell lung cancer cells with a bispecific molecule that activates polyclonal T lymphocytes.
OBJECTIVE
Gastrin-releasing peptide (GRP) is a growth factor for small cell lung cancer (SCLC). GRP belongs to the bombesin peptide family and has significant homology to bombesin. We constructed a bispecific molecule, OKT3xAntag2, by conjugating a monoclonal antibody OKT3 (anti-CD3) with a bombesin/GRP antagonist (Antag2) and evaluated cytotoxicity against SCLC cells.


METHODS
We tested binding of the bispecific molecule to SCLC cell lines and T cells by flow cytometry, antibody-dependent cellular cytotoxicity (ADCC) of SCLC cells in vitro and in a murine SCLC xenograft model. We studied SCLC apoptosis and necrosis during ADCC and the activity and cleavage of caspase-3, caspase-9, and poly(ADP-ribose) polymerase (PARP).


RESULTS
The bispecific molecule functions as a cross-linker between T cells and SCLC cells, induces T cell activation, and mediates ADCC of SCLC cells; 40% to 80% growth inhibition of SCLC cells mediated by the bispecific molecule at low effector to target cell ratios was achieved. Activation of T cells by the bispecific molecule resulted in significant increases in IFNgamma production and apoptosis and necrosis of SCLC cells associated with cleavage of PARP and caspase-3. Targeted immunotherapy with the bispecific molecule-armed human T cells significantly reduced SCLC tumor burdens in a mouse model.


CONCLUSIONS
The bispecific molecule OKT3xAntag2 mediates growth inhibition and apoptosis of SCLC cells by activated T cells through activation and cleavage of caspase-3 and PARP in vitro and in vivo. Clinical trials of this bispecific molecule through adoptive transfer of ex vivo activated T cells in GRP receptor-positive tumors, such as SCLC, are warranted.
Zhou
Jiehua
J
Division of Blood and Marrow Transplantation, Department of Medicine and Moores University of California at San Diego Cancer Center, University of California San Diego, La Jolla, California, USA.
Chen
Jian
J
Zhong
Ruikun
R
Mokotoff
Michael
M
Shultz
Leonard D
LD
Ball
Edward D
ED
D000818:Animals; D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D001665:Binding Sites; D018288:Carcinoma, Small Cell / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003601:Cytotoxicity Tests, Immunologic; D004195:Disease Models, Animal; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry / Q000494:pharmacology*; D007167:Immunotherapy / Q000379:methods; D007371:Interferon-gamma / Q000096:biosynthesis; D008175:Lung Neoplasms / Q000188:drug therapy*; D051379:Mice; D016688:Mice, Inbred NOD; D016853:Muromonab-CD3 / Q000737:chemistry; D010121:Oxytocin / Q000031:analogs & derivatives / Q000737:chemistry; D018004:Receptors, Bombesin / Q000187:drug effects* / Q000276:immunology; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
C115890:ANTAG II; D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D018796:Immunoconjugates; D016853:Muromonab-CD3; C511762:OKT3xAntag2; D018004:Receptors, Bombesin; D010121:Oxytocin; D007371:Interferon-gamma