Unlike many cancers, which have seen a tremendous increase in effective treatment options and, as a result, an increase in survival rates, the prognosis for patients diagnosed with glioblastoma (GBM) brain tumors remains pretty bleak. One of the biggest challenges associated with GBM is the fact that the blood-brain barrier prevents efficient drug dosing to tumors through traditional methods. Viral vectors and engineered nanoparticles have also offered some hope when it comes to overcoming diffusion barriers and selectively detecting and destroying tumor cells, but both of these methods still face significant challenges, including immunotoxicity and protein absorption, just to name a few.
In a recent study by Mehta, et al, published in the March 2017 issue of Molecular Therapy: Oncolytics, however, it was shown that specific bacterial carriers that are “actively motile and programmed to migrate and localize to tumor zones” seem to have the ability to suppress tumor growth by delivering targeted anti-cancer drugs directly to the GBM tumor in xenograft rat models. Mehta, et al designed a bacterial carrier that has a mutation in the msbB gene, which was shown to impede systemic toxicity in glioblastoma cancer xenograft models – one of the primary concerns associated with drug delivery through viral vectors – and is therefore expected to be safe for use in humans as well.
Specifically, the authors of this study engineered the bacterial carriers to express hypoxia-inducible expression of p53 and the pro-apoptotic drug, Azurin to kill the GBM tumors, and the results were rather remarkable. “In a xenograft model of human glioblastoma in rats, bacterial carrier therapy conferred a significant survival benefit with 19% overall long-term survival of >100 days in treated animals relative to a median survival of 26 days in control untreated animals.”
Although it is impossible to know for certain from this single study whether these findings will fully translate to successful patient therapies for the treatment of glioblastoma tumors, the bacterial carrier most definitely opens the door for the creation of some highly targeted therapies that could effectively suppress GBM tumor growth.