A new cancer therapy, called checkpoint blockade, has had some striking successes, but unfortunately it hasn’t shown potential for treating the most lethal tumors. Now scientists are testing a way to spur checkpoint blockade into more potent action using nanoparticles.
Wenbin Lin, a chemistry professor at the University of Chicago, said:
“Everybody out there working in the cancer space is trying to figure out ways to enhance checkpoint blockade immunotherapy. In this work, we were able to achieve that.”
Checkpoint blockade therapy works by interfering with cancer’s ability to turn off the body’s immune reaction. When cancer cells first develop, the body is able to recognize them as foreign, triggering T-cells to attack and eliminate them.
But as malignant cells multiply and form tumors, they release biochemical signals that suppress the immune system and the T-cells no longer function properly.
Checkpoint blockade therapy obstructs those signals, makes T-cells see the cancer cells as invaders again and allows the immune system to do its job. The problem, says Lin, is that if a tumor has been growing for years there are no longer any T-cells inside it to activate, so the therapy fails.
“So what we’re trying to do is to come up with ways to recruit T-cells to the tumor,” he says, “and if you have a way to make the T-cells recognize cancer cells, the T-cell will be able to kill the cancer cells.”
Pyrolipid Layer Triple Punch
The treatment Lin and collaborators invented is a drug cocktail contained in a nanoparticle. The nanoparticles assemble themselves from zinc and a drug called oxaliplatin, which is widely used against advanced-stage metastatic colon cancer. A photosensitizing agent called pyrolipid forms the outer layer.
When light is shined on the pyrolipid it generates molecules that can kill cancer. It also activates T-cells that can recognize cancer cells, so the nanoparticles pack a triple punch.
Used together, the nanoparticles and a checkpoint blockade agent eliminated tumors in a mouse, even when the tumors were widely separated and one of them had received no treatment.
The scientists injected a checkpoint blockade drug into the abdomen of a mouse that had two tumors growing at different places on its body, and then injected the nanoparticles into the mouse’s tail vein. They shined light onto one of the tumors to activate the pyrolipid. The other tumor was left untreated.
The irradiated tumor disappeared as expected. Remarkably the distant, untreated tumor disappeared as well. No irradiation with light meant no T-cells were activated in the second tumor,
“So we should not expect that tumor to disappear,” Lin says. “But we believe that this combination is able to activate the immune system to generate the T-cells that will recognize the cancer cells.
Then they go around the body and kill the cancer cells in the distant site that has not been irradiated with the light.”
This ability to activate T-cells in one place and have them travel to disease sites in the body could be a powerful tool for treating cancer. Most cancer patients die from metastatic disease, not their primary tumor. When patients have surgery, doctors don’t know if there are other, smaller lesions elsewhere in the body.
“You cannot treat them because you don’t know where to look for them,” Lin says. “If you activate immune cells, they can home in to cancer cells selectively. So you have a better chance of getting rid of these small metastatic tumors throughout the body.”
The National Cancer Institute, University of Chicago Medicine Comprehensive Cancer Center, Cancer Research Foundation, and Ludwig institute for Metastasis Research funded the work.
Chunbai He, Xiaopin Duan, Nining Guo, Christina Chan, Christopher Poon, Ralph R. Weichselbaum & Wenbin Lin Core-shell nanoscale coordination polymers combine chemotherapy and photodynamic therapy to potentiate checkpoint blockade cancer immunotherapy Nature Communications 7, Article number: 12499 (2016) doi:10.1038/ncomms12499
Image: MRC NIMR, Wellcome Images