The researchers believe that such viruses can be restricted to specific tissues by engineering the virus's genetic sequence with the aid of microRNAs.
They say that the microRNAs destabilize the virus's genome, making it impossible for the virus to run amok.
"Our findings demonstrate a new tool for molecular medicine that should also help allay concern over the use of viruses as a therapeutic delivery system," Nature Medicine quoted Dr. Stephen Russell, Mayo physician-scientist and lead author of the study, as saying.
MicroRNAs are the nucleotide snippets that are encoded by genes, but don't end up as proteins. In many cases, they have a role in down-regulating different cellular genes.
The Mayo Clinic team say that they have been successful in engineering a virus to be responsive to microRNAs that are present in certain cell types, thereby redirecting it to recognize only cancer cells.
They say that the experimental mice that received the engineered virus were cured of established tumours, without suffering any ill effects.
The team say that the target sequences of microRNAs used in the study kept the virus from destroying muscle cells, while allowing viral replication to proceed in cancer cells.
That, according to the researchers, allowed the virus to completely cure mice with melanoma.
The researchers say microRNA target insertion may be a new way to make viruses safer for use in cancer therapy, and may lead to new methods of making safer vaccines.