Researchers sneak drugs into cancer cells before triggering release

By waiting to trigger the drug's potency, the method may provide a better route toward treating malignant tumors.

Researchers sneak drugs into cancer cells before triggering release
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Image Credit: Ran Mo, PhD

Media Contact: Matt Shipman, NCSU News Services, 919.515.6386

May 9, 2014

RALEIGH, N.C. -- Researchers at the joint UNC / NC State Biomedical Engineering Department have developed an anti-cancer drug delivery method that “smuggles” a drug into a cancer cell before triggering its release. The method can be likened to keeping a cancer-killing bomb and its detonator separate until they are inside a cancer cell, where they then combine to destroy the cell.

 “This is an efficient, fast-acting way of delivering drugs to cancer cells and triggering cell death,” said Ran Mo, PhD, postdoctoral researcher in the joint BME Department and lead author of a paper published online in Angewandte Chemie. “We also used lipid-based nanocapsules that are already in use for clinical applications, making it closer to use in the real world.”

The technique uses nanoscale lipid-based capsules, or liposomes, to deliver both the drug and the release mechanism into cancer cells. One set of liposomes contains adenosine-5’-triphosphate (ATP), the so-called “energy molecule.” A second set of liposomes contains an anti-cancer drug called doxorubicin (Dox) that is embedded in a complex of DNA molecules. When the DNA molecules come into contact with high levels of ATP, they unfold and release the Dox. The surface of the liposomes is integrated with positively charged lipids or peptides, which act as corkscrews to introduce the liposomes into cancer cells.

As the liposomes are absorbed into a cancer cell, they are sealed off from the rest of the cell in an endosome – a compartment that walls off all foreign material that gets into a cell.

The environment inside an endosome is acidic, which causes the Dox liposomes and ATP liposomes to fuse together, as well as to the wall of the endosome itself.

Meanwhile, two other things are happening simultaneously. First, the ATP liposomes spill their ATP into the Dox liposomes, releasing the Dox from its DNA cage. Second, the walls of the Dox liposomes create an opening in the endosome, spilling their Dox-rich contents into the surrounding cell – leading to cell death.

In a mouse model, the researchers found that the new technique significantly decreased the size of breast cancer tumors compared to treatment that used Dox without the nanoscale liposomes.

“This work is somewhat similar to previous research we’ve done with polymer-based nanogels – but there is a key difference,” says Dr. Zhen Gu, senior author of the paper and an assistant professor in the joint BME program. “The difference is that this liposome-based technique allows us to introduce additional ATP into the cancer cell, releasing the drug more quickly.

“Being able to adjust ATP levels is important because some cancer cells are ATP deficient,” Gu adds. “But this technique would work even in those environments.”

The paper was co-authored by Tianyue Jiang, a graduate student in the joint BME program. The research was funded through a grant by the National Institutes of Health.

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