Researchers on the study used a technique called radioimmunotherapy, in which radioisotopes are piggybacked onto antibodies. Once these precision-made molecules are injected into the body, the antibodies home in on a specific protein target...and the radioisotope "warhead" destroys the cell to which the protein is attached.
This novel approach is important to note because nearly 20 percent of human cancers worldwide are caused by preexisting virus infections. Prime examples are liver cancer (caused by hepatitis B and C viruses), cervical cancer (caused by human papillomaviruses) and certain lymphomas (caused by the Epstein-Barr virus). But while antigens on the surface of cells are susceptible to attack by antibodies, the viral antigens associated with cancers typically lurk inside infected cells, so scientists had assumed that antibodies couldn't reach them.
Dr. Arturo Casadevall, Forchheimer Professor and Chair of Microbiology and Immunology at Einstein and co-senior author of the study published in PloS One said, "We had a hunch that rapidly growing tumors can "outgrow" their blood supply, resulting in dead tumor cells that might spill their viral antigens amongst the living cancer cells."
Casadevall goes on to say, "So we hoped that by injecting antibodies hitched to isotopes into the blood that they'd be carried deep into the tumor mass and would latch onto these now-exposed antigens. Then the blast of radiation emitted by the radioisotope would destroy the live tumor cells nearby."
According to the study researchers tested their theory in mice by attaching the radioisotopes to the antibodies expressed by cervical-cancer cells and liver cancer cells. For both types of cancer, the radioimmunotherapy resulted in significant slowing of tumor growth compared with tumors in untreated mice. For the cervical-cancer mice, the therapy not only stopped the growth of tumors but even caused them to regress.
Dr. Ekaterina Dadachova, Associate Professor of Nuclear Medicine and of Microbiology and Immunology at Einstein said, "Radioimmunotherapy not only worked against these cancers, but in addition the radioactivity was confined entirely to the tumor masses, leaving healthy tissues undamaged."
Dadachova goes on to say, "Virus-associated cancers account for some 1.3 million cancer cases each year, so the need for new strategies in treating them is obvious and urgent."
Scientists say the results are more than promising and the study has shown in principle that radioimmunotherapy can help in treating cancers caused by viruses and for cancer prevention. Furthers studies hopefully will give insight into how to treat chronically infected people with hepatitis B or C, human papillomaviruses, or other viruses known to cause cancer. Based on the early findings with the mice radioimmunotherapy could potentially eliminate virus-infected cells before they're able to transform into cancer cells.
