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

PLoS One. 2014 Nov 3;9(11):e109866. doi: 10.1371/journal.pone.0109866. eCollection 2014.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal*
  • CTLA-4 Antigen / antagonists & inhibitors
  • CTLA-4 Antigen / genetics
  • CTLA-4 Antigen / metabolism*
  • Cell Line, Tumor
  • Copper Radioisotopes*
  • Disease Models, Animal
  • Female
  • Gene Expression
  • Humans
  • Lymphocytes, Tumor-Infiltrating / metabolism*
  • Mice
  • Neoplasms / diagnosis*
  • Neoplasms / genetics
  • Neoplasms / metabolism*
  • Organometallic Compounds*
  • Positron-Emission Tomography* / methods
  • Protein Binding
  • Radiopharmaceuticals

Substances

  • Antibodies, Monoclonal
  • CTLA-4 Antigen
  • Copper Radioisotopes
  • Organometallic Compounds
  • Radiopharmaceuticals

Grant support

This work was supported by a grant-in-aid for COE projects by MEXT, Japan, titled “Center of excellence for molecular and gene targeting therapies with micro-doze molecular imaging modalities.”, a grant from Japan Society for the Promotion of Science (grant number: 12J06885, URL: http://www.jsps.go.jp/english/index.html), and a grant form the Ministry of Education, Culture, Sports, Science and Technology (URL: http://www.pref.okayama.jp/page/287673.html). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.