When researchers combined an FDA-approved cancer immunotherapy with a new tumour-roasting nanotechnology, both therapies improved, according to a new proof-of-concept study.
Further, the potent combination also attacked satellite tumours and distant cancerous cells, completely curing two mice and effectively vaccinating one against the disease.
“The ideal cancer treatment is non-invasive, safe, and uses multiple approaches,” says Tuan Vo-Dinh, professor of biomedical engineering, professor of chemistry, and director of the Fitzpatrick Institute for Photonics at Duke University.
“We also aim at activating the patient’s own immune system to eradicate residual metastatic tumours. If we can create a long-term anticancer immunity, then we’d truly have a cure.”[pull_quote]
As reported in Scientific Reports, the new approach relies on a “photothermal immunotherapy” technology that uses lasers and gold nanostars to heat up and destroy tumours in combination with an immunotherapeutic drug.
This photothermal therapy hinges on the widely demonstrated fact that nanoparticles accumulate preferentially within a tumour due to its leaky vasculature.While several researchers around the world are pursuing techniques using nanoparticles, Vo-Dinh has pioneered the development of a unique type of nanoparticle called gold nanostars, which have the advantage of geometry. Because gold nanostars have multiple sharp spikes, they are able to capture the laser’s energy more efficiently, allowing them to work with less exposure and making them more effective deeper within a tissue.
“The nanostar spikes work like lightning rods, concentrating the electromagnetic energy at their tips,” Vo-Dinh says. “We’ve experimented with these gold nanostars to treat tumours before, but we wanted to know if we could also treat tumours we didn’t even know were there or tumours that have spread throughout the body.”
To attack distant cancerous cells outside of the treatment site, Vo-Dinh teamed up with colleagues Brant Inman and Greg Palmer in the surgery and radiation oncology department and Paolo Maccarini of biomedical engineering. The researchers combined this gold nanostar therapy with a cancer immunotherapy recently already cleared by the FDA and in clinical use. Normally, the body’s immune system protects against the growth of cancerous cells. Many tumours, however, overproduce a molecule called PD-L1, which effectively disables T cells, the immune system’s main soldiers.
Several pharmaceuticals are being developed to attempt to block the action of PD-L1, allowing the immune system to destroy the cancerous cells. Inman has been active in the early development and current clinical use of these drugs—which were used in this study—to treat bladder cancer.
In the experiment, researchers injected bladder cancer cells into both hind legs of a group of mice. After waiting for the tumours to grow, they began trying different types of treatments—but only on one of the legs. Those that received no treatments all quickly succumbed to the cancer, as did those receiving only the gold nanostar phototherapy—the treatment did nothing to affect the tumour in the untreated leg. While a few mice responded well to the immunotherapy alone, with the drug stalling both tumours, none survived more than 49 days.
The group of mice treated with both the immunotherapy and the gold nanostar phototherapy fared much better, with two of the five mice surviving more than 55 days.
“When a tumour dies, it releases particles that trigger the immune system to attack the remnants,” Vo-Dinh says. “By destroying the primary tumour, we activated the immune system against the remaining cancerous cells, and the immunotherapy prevented them from hiding.”
The combined treatment worked so well that, in a bit of a surprise, one mouse is still alive nearly a year out with zero recurrence of the cancer. Even a month later, when the researchers injected more cancerous cells, the mouse’s immune system attacked and destroyed them without a problem indicating a vaccine effect in the cured mouse.
“This is our goal—our dream,” Vo-Dinh says.
While the proof-of-concept experiment was conducted with a small number of mice, the results are encouraging. Researchers now plan to follow up with larger cohorts and to work with other clinical researchers to test the treatment on mouse models of brain, breast, and lung cancer.