Feb. 15 (HealthDay News) -- A laboratory-engineered virus can successfully slow the growth of two types of hard-to-treat pediatric tumors without harming healthy tissue, a new study shows.

The targeted viral therapy, dubbed rQT3, slowed neuroblastoma and peripheral nerve sheath tumors in mice, according to findings published in the Feb. 15 issue of Cancer Research. It also resulted in longer life spans in the mice compared with ones receiving just saline or other treatments for the tumors.

Neuroblastoma is the most common solid cancer tumor in childhood, most often striking those under age 5. Malignant peripheral nerve sheath tumors affect the connective tissue surrounding nerves.

Researchers at Cincinnati Children's Hospital Medical Center armed the oncolytic herpes simplex virus (oHSV)with a gene that steps up the body's work to block enzymes that aid the development and progression of certain cancers. Previous studies had shown oHSV can infect and kill human cancer cells without causing other harm or disease.

"Malignant solid tumors are still very difficult to treat effectively, especially without causing harm to normal tissues, so we need to find innovative therapeutic approaches," Dr. Timothy Cripe, a physician and researcher at Cincinnati Children's Hospital Medical Center, said in a prepared statement. "In our study, this tumor-targeting viral therapy enhanced anti-tumor activity by stimulating multiple biological processes, including directly killing the cancer cells and reducing the formation of blood vessels that fed the tumors. These data support continuing development and study of our tumor-targeted viral therapy to fight cancer."

The gene added to the virus carries instructions for a cancer-fighting protein, human tissue inhibitor of metalloproteinase 3 (TIMP3). TIMP3 blocks enzymes that aid the development and progression of cancer, called matrix of metalloproteinases (MMP).

MMPs help break down molecules that are important for the structural support and normal development of cells, organs and maintenance of tissues. However, when MMP activity becomes unbalanced, the enzyme plays a well-documented role in the formation of invasive and metastatic cancers, including pediatric neuroblastoma.

SOURCE: Cincinnati Children's Hospital Medical Center, news release, Feb. 15, 2008