Radioimmunotherapy targeting viral antigens shows potential to treat or prevent viral cancers

A new study, presented at the Society of Nuclear Medicine's 55th Annual Meeting, shows that radioimmunotherapy (RIT) targeting viral antigens offers a novel option to treat-or even prevent-many viral cancers by targeting cancer cells expressing viral antigens or infected cells before they convert into malignancy.

"There is an urgent need to find new approaches to treating and preventing viral cancers," said Ekaterina (Kate) Dadachova, associate professor of nuclear medicine and microbiology and immunology at Albert Einstein College of Medicine, Bronx, N.Y. and lead researcher of the study, Viral Antigens as Novel Targets for Radioimmunotherapy of Viral Cancers. "The magnitude and global health-burden associated with viral cancers is only now being realized."

It is estimated that up to 25 percent of all cancers are currently linked to existing viral infections. Most of these cancers are extremely difficult to treat and cannot successfully be reduced or removed using conventional therapies or treatments. Viral cancers include cervical cancers caused by infection with a human papillomavirus (HPV), a sexually transmitted disease; hepatocellular carcinoma (HCC), a cancer of the liver; various lymphomas and carcomas in patients with AIDS/HIV; and other cancers.

According to Dadachova, this is the first time that researchers have attempted to target viral antigens on cancers, although the use of RIT for the treatment of cancer has been under development for thirty years. However, the targets of RIT therapy to date have included only "self" human antigens, which are overexpressed on the tumors but also expressed on normal tissues. Viral antigens, on the contrary, are expressed only on the tumors and nowhere else in the body.

The idea to perform the study was suggested by Dr. Arturo Casadevall, chair of the department of microbiology and immunology at Albert Einstein College of Medicine, who collaborates with Dadachova on developing radioimmunotherapy of infectious diseases and cancers. The study involved treating experimental cervical cancer and hepatocellular carcinoma in nude mice with antibodies to respective viral antigens expressed on these tumors. The antibodies were radiolabeled with 188-Rhenium-a powerful beta-emitting radionuclide. "This study demonstrates a real possibility for more specifically targeted cancer treatments," said Dadachova. "Targeting those antigens with radiolabeled molecules offers exquisite specificity-and will hopefully allow us to significantly increase the efficacy of treatment by administering more individualized doses while avoiding toxicity."

"Nuclear medicine and molecular imaging offer the ability to target disease on a truly molecular level that is unmatched by any other imaging or therapeutic modality," said Dadachova. "Targeting viral antigens with radiolabeled antibodies (or also with specific peptides or aptamers) will allow the extremely precise diagnosis of such cancers and their effective therapy. Furthermore, this approach will make possible 'molecular prevention' of viral cancers, when infected cells will be targeted before they become cancerous."

Dadachova and her team will also be recognized for this study by SNM's Young Professionals' Committee, which recognizes the contributions of significant studies to the fields of nuclear medicine and molecular imaging by young researchers. The Young Professionals' Committee Award will be presented on Sunday, June 15, during a luncheon.

This study was supported by the National Institutes of Health (NIH), Center for AIDS Research (CFAR) and Albert Einstein Cancer Center (AECOM).

Scientific Paper 412: E. Dadachova, X. Wang, E. Revskaya, R.A. Bryan, A. Casadevall, Albert Einstein College of Medicine, Bronx, N.Y., "Viral Antigens as Novel Targets for Radioimmunotherapy of Viral Cancers," SNM's 55th Annual Meeting, June 14-18, 2008.