"Trojan Horse" Nanoparticles Kill Cancer Cells Without Drugs

An artist's three-dimensional impression of a cancer cell. SciePro/Shutterstock

Scientists have created a “Trojan horse” that sneaks anticancer nanoparticles into cancer cells and causes them to self-destruct without any drugs. The research is still in its early days, but the new method has already proved to be remarkably effective at killing cancer cells in a petri dish and reducing tumor growth in mice. 

Researchers at Nanyang Technological University Singapore (NTU Singapore) developed their “Trojan horse” by lacing an anti-cancer nanoparticle with a specific amino acid, known as L-phenylalanine, which cancer cells rely on to grow. The cancer cells seek to absorb the amino acid, unknowingly letting in this anticancer nanoparticle and causing them to self-destruct. 

The nanoparticle is known as Nano-pPAAM, an ultrasmall particle with a diameter of 30 nanometers that has “excellent intrinsic anticancer and cancer-selective properties,” according to the paper. Once inside the cancer cells, Nano-pPAAM stimulates excessive reactive oxygen species (ROS) production, causing cancer cells to perish while remaining harmless to the healthy cells.

Reported in the journal Small, the team tested the efficacy of the nanoparticle in the lab and found that the nanoparticle killed about 80 percent of breast, skin, and gastric cancer cells, a rate comparable to some cancer drugs. It also significantly reduced tumor growth by around 60 percent in mice with human triple-negative breast cancer cells compared to control models.

"Against conventional wisdom, our approach involved using the nanomaterial as a drug instead as a drug-carrier. Here, the cancer-selective and killing properties of Nano-pPAAM are intrinsic and do not need to be 'activated' by any external stimuli. The amino acid L-phenylalanine acts as a 'trojan horse' – a cloak to mask the nanotherapeutic on the inside,” Assistant Professor Dalton Tay, lead study author from the School of Materials Science and Engineering at NTU Singapore, commented in a statement

"By removing the drug component, we have effectively simplified the nanomedicine formulation and may overcome the numerous technological hurdles that are hindering the bench-to-bedside translation of drug-based nanomedicine."

Previous research has suggested that cancer tumor growth can be slowed or prevented by “starving” cancer cells of these much-needed amino acids through fasting or special diets lacking in protein. Unfortunately, these diets are not always good for the patient, especially if they are already ill from their disease. This new method, however, would theoretically not have this negative side-effect. 

Next up, the researchers are looking into ways to further refine the design of Nano-pPAAM to make it more precise in targeting specific cancer types and become even more efficient at killing tumors. 

Of course, there’s still a long way to go before this is a viable cancer treatment for humans. However, scientists are always on the lookout for novel ways to treat cancer, especially since some cancers have developed a resistance to the current collection of drugs in our arsenal. 

"This novel approach could hold much promise for cancer cells that have failed to respond to conventional treatment like chemotherapy,” explained Associate Professor Tan Ern Yu, a breast cancer specialist at Tan Tock Seng Hospital who was independent of the study. “Such cancers often have evolved mechanisms of resistance to the drugs currently in use, rendering them ineffective. However, the cancer cells could potentially still be susceptible to the 'Trojan horse' approach since it acts through a completely different mechanism – one that the cells will not have adapted to."

 

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