According to Penn State researchers, a newly developed “GPS nanoparticle,” injected intravenously, can locate cancer cells to deliver a gene drive to the protein involved in tumor growth and spread. They tested their approach in human cell lines and in mice to effectively disable a cancer-causing gene, reporting that the technique can potentially offer a more precise and effective treatment for notoriously difficult-to-treat basal-like breast cancers.
They published their work today (March 11) in ACS Nano. They also filed a provisional application to patent the technology described in this study.
“We developed a GPS nanoparticle that can find where it’s needed,” said corresponding author Dipanjan Pan, Dorothy Foehr Huck & J. Lloyd Huck Professor of Nanomedicine and professor of nuclear engineering and of materials science and engineering at Penn State. . “Once there, and only there, it can deliver gene-editing proteins to prevent cancer cells from spreading. It was a difficult task, but we showed that the system works for basal-type breast cancers.”
Like triple-negative breast cancers, basal-type breast cancers may be less prevalent than other breast cancers, but they can be much more difficult to treat, largely because they lack the three therapeutic targets found in other breast cancers. They also tend to be aggressive, fast-growing tumors that shed cells that spread to other parts of the body. Those cells can seed additional tumors, a process called metastasis.
“Metastasis is a big challenge, especially in cancers such as triple-negative and basal-type breast cancer,” Pan said. “The cancer can be difficult to detect and does not show up during a routine mammogram, and mainly affects the population younger or African American who may not be receiving preventive care yet. The outcome may be very, very poor, so there is a clear “Unmet clinical need for more effective treatments when cancer is not detected early enough.”
The team made a Trojan horse nanoparticle, disguising it with specially designed fatty molecules that look like natural lipids and filling it with CRISPR-Cas9 molecules. These molecules can target a cell’s genetic material, identify a particular gene, and knock it down or render it ineffective. In this case, the system focused on the human forkhead box c1 (FOXC1), which is involved in the instigation of metastasis.
Pan described the designed lipids as “zwitterionic,” meaning they have a nearly neutral charge in the nanoparticle shell. This prevents the body’s immune system from attacking the nanoparticle, because it is disguised as a normal, non-threatening molecule, and can help release the payload, but only when the lipids recognize the low pH environment of the cancer cell. To ensure that the lipids were only activated at that low pH, the researchers designed them to change their charges to positive once they enter the more acidic microenvironment of the tumor, triggering the release of the payload.
But the body is a huge place, so how could researchers ensure that the CRISPR-Cas9 payload reached the right target? To ensure that the nanoparticle bound to the correct cells, they attached an epithelial cell adhesion molecule (EpCAM), which is known to adhere to basal-type breast cancer cells.
“No one has ever tried to target a basal-type breast cancer cell with a context-sensitive delivery system that can genetically inactivate the gene of interest,” Pan said. “We are the first to show that it can be done.”
Others have developed viral delivery systems, sequestering a virus particle to deliver the treatment to cells, and non-viral delivery systems, using nanoparticles. The difference, Pan said, to his team’s approach is that the surface lipid is designed to respond only in the target environment, reducing the potential for off-target delivery and damage to healthy cells. Additionally, he added, since the body does not consider lipids to be a threat, there is less chance of an immune response, which they validated in their experiments.
The team first tested the approach in human triple-negative breast cancer cells, validating that the nanoparticle would deploy the CRISPR/Cas9 system in the right environment. They confirmed that the nanoparticle could reach a tumor in a mouse model, deploy the system, and successfully knock down FOXC1.
Next, Pan said, the researchers plan to continue testing the nanoparticle platform with the ultimate goal of applying it clinically in humans.
“We are also exploring how else we could apply the platform technology,” Pan said. “We can customize the molecules on the surface, the payload they carry and use them to stimulate healing in other areas. This platform has a lot of potential.” .
The first author, Parikshit Moitra, was an assistant research professor of nuclear engineering in Pan’s lab at Penn State at the time of the study and is now an assistant professor at the Indian Institute of Science Education and Research in Berhampur; David Skrodzki, Matthew Molinaro, Nivetha Gunaseelan, all PhD students at Penn State; Dinabandhu Sar, University of Illinois, Urbana-Champaign; Teresa Aditya, a postdoctoral researcher in nuclear engineering at Penn State; Dipendra Dahal and Priyanka Ray, both postdoctoral researchers in Pan’s lab at his former institution at the University of Maryland in Baltimore.
Penn State, University of Maryland Baltimore School of Medicine, Centers for Disease Control and Prevention, U.S. National Science Foundation, and Department of Defense Congressionally Directed Medical Research Program of the USA funded this work.