Researchers from the California Institute of Technology have shown that nanoparticles can specifically target human tumors leaving neighboring healthy tissue unscathed. The results of this study may help to further nanoparticle-based therapies to treat cancer in the clinic.
Mark Davis, a chemical engineering professor at Caltech, and his team published their findings this week in the journal Proceedings of the National Academy of Sciences.
"Our work shows that this specificity, as previously demonstrated in preclinical animal studies, can in fact occur in humans," said Davis. "The ability to target tumors is one of the primary reasons for using nanoparticles as therapeutics to treat solid tumors."
They chemically attached a chemotherapy drug (camptothecin) to nanoparticles 30 nanometers in size, administering the nanoparticle-drug to patients with gastric tumors and examined the tumor before and after the treatment. The tiny drug-bearing particles were present in the tumor up to 24 to 48 hours after treatment, and importantly the drug had begun carrying out its anti-cancer function--observed by the reduction of two cancer proteins.
Studying local tissue around the tumor, they did not find any localization of the particles, nor the drug, in healthy tissues.
"We can attach different drugs to the nanoparticles, and by changing the chemistry of the bond linking the drug to the nanoparticle, we can alter the release rate of the drug to be faster or slower," said Andrew Clark, a graduate student in the lab, commenting of the adaptive nature of the engineered nanoparticles.
The efficacy of these nanoparticles is due at least in part to something called "enhanced permeability and retention" which takes advantage of unhealthy (tumor) blood vessels since they are leakier than normal vessels found in healthy tissue. The result is that nanoparticles can specifically target these leaky vessels that supply tumor tissue, dumping the chemical payload and targeting the cancer only.
This phenomenon was known to exist in the animal model but this is the first evidence that it may also work successfully in human tumors. "Our results don't prove the EPR effect in humans, but they are completely consistent with it," Davis said.
Rather than a one-size-fits-all approach which is the traditional way to treat cancers, this precision medicine may see its way into the clinic soon--allowing multiple drugs to target specific tissues without harming healthy tissue.