About a dozen Hoosier pet dogs are considered success stories after undergoing an experimental therapy for bladder cancer being developed at Purdue University. Each dog had a bleak prognosis—all were terminally ill and had exhausted all existing treatment options. Amazingly, the pooches were treated with what most non-chemists would consider a chemical weapon: anthrax. Purdue researchers believe the bacterial toxin—when purified and modified—could be the key to treating bladder cancer for humans too.
“We think this [experimental treatment] is transformative; that’s a word we try not to use lightly,” says Purdue College of Science Associate Professor and Biological Sciences Assistant Head Dr. R. Claudio Aguilar.
The disease has the highest rate of recurrence among all cancers—an alarming 70%—and is the most expensive cancer to treat. Additionally, the human toll is so high that Aguilar says many patients quit treatment. The standard practice involves surgical removal of the tumor, then follow-up therapies that attempt to block the cancer’s likely recurrence.
The most common follow-up therapy is BCG, which involves introducing a bacteria to the bladder; patients must endure several hours of having a severely full bladder. Aguilar says the treatment is only mildly effective, and a worldwide shortage of the bacteria means doctors are scrambling to stretch the therapy by reducing doses.
Aguilar believes the most transformative aspect of his new therapy, recently published in the International Journal of Cancer, is its efficiency. Similar to BCG’s method, a solution containing a bacteria is put inside the bladder, but only needs to be held there a few minutes, rather than hours. The bacteria just happens to be anthrax toxins that have been modified and purified.
“The [anthrax] toxin has two components and is completely innocuous until you mix the two components. Paradoxically, it’s very, very safe; it’s non-toxic if you’re not a cancer cell. If you’re a cancer cell, we’re targeting a specific characteristic that makes them susceptible to it,” says Aguilar. “The toxin is incorporated into the [cancer] cell very, very quickly—a matter of three minutes—and immediately triggers a response in the cell that leads to the cell death. In a few hours, the cancer cells are dead, and the normal cells are spared.”
That’s because a normal bladder cell secretes a mucus that forms a protective layer around the cell to shield it from coming into contact with urine—“a very aggressive and nasty environment that cells don’t like to be exposed to,” says Aguilar. The mucus protects the healthy cell from the toxin, but tumor cells are exposed to it, because they don’t produce the mucus.
Requiring only a very small amount of the toxin, the treatment is efficient, highly specific and very fast, says Aguilar. The dogs treated with the experimental therapy at the Purdue Veterinary Teaching Hospital, on average, showed a 30% reduction of tumor mass with a single cycle of treatment.
“These are tumors that were resistant to every known treatment, and we were successful,” says Aguilar. “Hopefully, we’ll soon be able to treat dogs earlier in the development of the cancer and better help them.”
Aguilar’s team is confident the results will translate to the human patient population. The Indiana University School of Medicine Department of Urology is providing the Purdue team with samples of freshly resected cancerous bladder tumors from humans. Testing the anthrax agent on these tumors is also showing success.
“The technology is so efficient, it’s been proposed to be used following [surgical removal of the tumor], but also as a possibility of being the primary intervention, because it would be able to eliminate the tumor,” says Aguilar. “As a matter of fact, in the test we did with canine patients, it was the primary intervention—replacing even the surgery.”
While anthrax may jog memories of powder in envelopes during the days following the 9/11 terrorist attacks, Aguilar says this modified form is safe and has produced no toxicity in the canine patients. The team is “working very hard” to advance the technology to human clinical trials. The technology is patented, and the researchers are working with Purdue’s Office of Technology Commercialization.
“I’m excited about providing something of high-efficiency that is less traumatic for the patient,” says Aguilar. “We think it will definitely change the scenario of how we treat bladder cancer, and that’s really, really appealing to us and the patients.”
Aguilar says the team is advancing the bladder cancer therapy toward clinical trials, while also exploring how the agent could be adapted for other cancers, including prostate.
Aguilar says the successful treatment of Hoosier dogs at Purdue generated buzz in other places.