Targeting gastrin-releasing peptide receptors on small cell lung cancer cells with a bispecific molecule that activates polyclonal T lymphocytes.

Abstract

PURPOSE:

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.

EXPERIMENTAL DESIGN:

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.

CONCLUSION:

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.

• Authors: Jiehua Zhou, Jian Chen, Ruikun Zhong, Michael Mokotoff, Leonard D Shultz, Edward D Ball
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 12 Issue 7 Pt 1 Pg. 2224-31 (Apr 01 2006) ISSN: 1078-0432 [Print] United States
• PMID: 16609038 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• ANTAG II
• Antibodies, Bispecific
• Antibodies, Monoclonal
• Antineoplastic Agents
• Immunoconjugates
• Muromonab-CD3
• OKT3xAntag2
• Receptors, Bombesin
• Oxytocin
• Interferon-gamma

Topics

• Animals
• Antibodies, Bispecific
• Antibodies, Monoclonal (chemistry, pharmacology)
• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects, immunology)
• Binding Sites
• Carcinoma, Small Cell (drug therapy)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cytotoxicity Tests, Immunologic
• Disease Models, Animal
• Humans
• Immunoconjugates (chemistry, pharmacology)
• Immunotherapy (methods)
• Interferon-gamma (biosynthesis)
• Lung Neoplasms (drug therapy)
• Mice
• Mice, Inbred NOD
• Muromonab-CD3 (chemistry)
• Oxytocin (analogs & derivatives, chemistry)
• Receptors, Bombesin (drug effects, immunology)
• Structure-Activity Relationship
• T-Lymphocytes (drug effects, immunology)
• Transplantation, Heterologous
• Tumor Cells, Cultured
• Xenograft Model Antitumor Assays