Just days ago in the journal Stem Cells, a proof-of-concept study documented researchers’ discovery that stem cells loaded with herpes can be programmed to kill only the cancer cells remaining in mouse brains after tumor removal. The genetically engineered stem cells synthesize and secrete the cytotoxins but are not themselves affected by it. The cytotoxins are tagged so that they only attack cancer cells with a certain surface molecular marker, leaving other cells completely unharmed. Once inside the cancer cell, the cytotoxins prevents it from making proteins and growing, resulting in death of the cell.
Previous attempts with this form of drug delivery failed because the stem cells themselves were vulnerable to the toxin. Genetic engineering enabled the researchers to develop mutated human neural stem cells that don’t allow the toxin to work while retained within. Similar therapeutic strategies have worked with blood cancers, but solid tumors have remained challenging because the cancers were inaccessible and the toxins have a short half-life. These scientists put the stem cells inside a biodegradable gel capsule that they are able to place within the brain at the site of tumor resection, which solved the drug delivery problem.
Clinical trials are expected within 5 years directed toward glioblastoma, the most common brain tumor in adult humans.