Mitch Leslie in Science:
Curing the childhood eye cancer retinoblastoma often comes at a cost. The tumor, which sprouts in the retina and primarily occurs in children under the age of 5, is fatal if not treated. Yet chemotherapy can cause permanent vision loss, and patients sometimes need surgery to remove one or both eyes. Now, scientists have found that a cancer-slaying virus seems to combat this cancer in mice without serious side effects. A clinical trial has also shown early signs of promise. “It’s potentially a game-changer,” says ophthalmic oncologist David Abramson of Memorial Sloan Kettering Cancer Center in New York City, who wasn’t connected to the study. Researchers have tested cancer-targeting viruses in other types of tumors, but no one had pitted them against retinoblastoma. The tumors grow when there are defects in a molecular pathway that keeps cells from dividing out of control. Oncology researcher Ángel Montero Carcaboso of the Sant Joan de Déu Research Institute in Barcelona, Spain, and colleagues used a type of virus known as adenovirus that typically causes only mild respiratory infections in people. It had been genetically modified so it was missing a key gene and could only reproduce inside cells in which the retinoblastoma pathway had malfunctioned.
To determine whether such a virus would be safe, the scientists injected it into the eyes of rabbits without the tumor. The virus triggered side effects such as inflammation and fluid buildup in the eyes, but they disappeared within 6 weeks. Moreover, little of the virus escaped from the eyes, and it didn’t appear to reproduce elsewhere in the animals’ bodies, suggesting it wouldn’t cause harm in other organs.
…On the strength of those results, Carcaboso and colleagues have begun a clinical trial to test whether the virus is safe in children with retinoblastomas that haven’t responded to chemotherapy or radiation treatment. Two patients have received the virus so far. The researchers have noted preliminary signs that the virus is targeting the tumors.