Mayo Clinic Researchers Invent "Hitchhiking" Viruses As Cancer Drug Delivery System

A Mayo Clinic research team has devised a new virus-based gene therapy delivery system to help fight cancer. Researchers say their findings will help overcome hurdles that have hindered gene therapy cancer treatments. The Mayo research team, which includes a collaborator from the United Kingdom, describes its new approach in the current edition of Nature Medicine (http://www.nature.com/nm/index.html). The approach relies on "therapeutic hitchhikers" -- particles derived from retroviruses (RNA-containing viruses that incorporate into the genomes of infected cells and then produce a therapeutic gene). The viral particles attach to a specific kind of T cell in the immune system and "hitchhike" to the tumor because T cells home in on tumors naturally; T cells are the immune system's major line of defense against tumors. By hitching a ride on the T cells, the therapeutic particles can hit their tumor target while avoiding detection (and destruction) by the immune system. When the Mayo team experimented with the hitchhiking approach in mice using human and mouse cancer cells, they observed significant cure rates of metastatic -- or spreading -- tumors. "Any clinical situation in which cells home to disease sites -- such as inflammation or autoimmune disease -- might benefit from this approach," explains Richard Vile, Ph.D., Mayo Clinic molecular immunologist and lead researcher of the investigation. "Our work is an important contribution to the maturation of the field of gene therapy because ultimately treating cancers by gene therapy depends on scientists' ability to specifically target tumor cells in the patient -- and this specific-delivery feature has eluded researchers for a variety of reasons. But by devising a way for viruses to hitch rides on antigen-specific T cells, we've been able to get over multiple obstacles to gene therapy." Dr. Vile emphasizes that the work is still experimental and not yet ready for use in human patients. But if larger studies validate these findings, the therapeutic hitchhiker approach may be employed in clinical trials of new treatments.

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