64Cu-DOTA-anti-CTLA-4 mAb enabled PET visualization of CTLA-4 on the T-cell infiltrating tumor tissues

• Published in: PloS one 2014-11, Vol.9 (11), p.e109866-e109866
• Main Authors: Higashikawa, Kei, Yagi, Katsuharu, Watanabe, Keiko, Kamino, Shinichiro, Ueda, Masashi, Hiromura, Makoto, Enomoto, Shuichi
• Format: Article
• Language: English
• Subjects: Animal tissues; Animals; Antibodies, Monoclonal; Antigens; Autoimmune diseases; Bearing; Biology and Life Sciences; Biopsy; Cancer; Cancer therapies; Cell Line, Tumor; Colon; Copper Radioisotopes; CTLA-4 Antigen - antagonists & inhibitors; CTLA-4 Antigen - genetics; CTLA-4 Antigen - metabolism; CTLA-4 protein; Cytotoxicity; Dentistry; Diabetes; Disease Models, Animal; Emission analysis; Epidermal growth factor; Female; Gene Expression; Humans; Immune system; Immunoglobulins; Life sciences; Ligands; Lymphocytes; Lymphocytes T; Lymphocytes, Tumor-Infiltrating - metabolism; Medical imaging; Medicine; Medicine and Health Sciences; Melanoma; Mice; Monoclonal antibodies; Neoplasms - diagnosis; Neoplasms - genetics; Neoplasms - metabolism; Organometallic Compounds; Pharmaceutical sciences; Polymerase chain reaction; Positron emission; Positron emission tomography; Positron-Emission Tomography - methods; Prostate; Protein Binding; Radiopharmaceuticals; Research and Analysis Methods; Reverse transcription; Rodents; Side effects; Therapy; Tomography; Visualization
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0109866

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) targeted therapy by anti-CTLA-4 monoclonal antibody (mAb) is highly effective in cancer patients. However, it is extremely expensive and potentially produces autoimmune-related adverse effects. Therefore, the development of a method to evaluate CTLA-4 expression prior to CTLA-4-targeted therapy is expected to open doors to evidence-based and cost-efficient medical care and to avoid adverse effects brought about by ineffective therapy. In this study, we aimed to develop a molecular imaging probe for CTLA-4 visualization in tumor. First, we examined CTLA-4 expression in normal colon tissues, cultured CT26 cells, and CT26 tumor tissues from tumor-bearing BALB/c mice and BALB/c nude mice by reverse transcription polymerase chain reaction (RT-PCR) analysis and confirmed whether CTLA-4 is strongly expressed in CT26 tumor tissues. Second, we newly synthesized 64Cu-1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-anti-mouse CTLA-4 mAb (64Cu-DOTA-anti-CTLA-4 mAb) and evaluated its usefulness in positron emission tomography (PET) and ex-vivo biodistribution analysis in CT26-bearing BALB/c mice. High CTLA-4 expression was confirmed in the CT26 tumor tissues of tumor-bearing BALB/c mice. However, CTLA-4 expression was extremely low in the cultured CT26 cells and the CT26 tumor tissues of tumor-bearing BALB/c nude mice. The results suggested that T cells were responsible for the high CTLA-4 expression. Furthermore, 64Cu-DOTA-anti-CTLA-4 mAb displayed significantly high accumulation in the CT26 tumor, thereby realizing non-invasive CTLA-4 visualization in the tumor. Together, the results indicate that 64Cu-DOTA-anti-CTLA-4 mAb would be useful for the evaluation of CTLA-4 expression in tumor.