Protein Delivery Capsule

Scientists at the University of California, Los Angeles have invented a tiny capsule that could mean big advancements in cancer treatment, according to a new study published in the journal Nano Today.

This degradable, nanoscale shell is about half the size of the smallest bacterium and could serve as a vehicle to deliver proteins to cancer cells. Made of a water-soluble polymer, or chemical compound, this capsule safely delivers a protein complex to cancer cells to stunt tumor growth, while leaving non-cancerous cells unharmed.  

While this technology has yet to be used in preclinical or clinical trials, study author Yi Tang, a professor of chemical and biomolecular engineering at UCLA, said his team’s research “opens up opportunities for intracellular protein delivery as a way of eliminating cancer cells within a tumor.”

To test this strategy, Tang and his colleagues performed experiments on human breast cancer cell lines in laboratory mice, and they showed a significant reduction in tumor growth. However, Tang said this method could be used to treat other forms of cancer as well.

“In principle, this method can be used to treat different types of cancers,” he said in an interview with Healthline. “Thus, it presents a general improvement in our abilities to delivery otherwise difficult-to-administer, protein-based drugs that target intracellular pathways.”

The Need for a Vehicle

Unlike chemotherapy, which can kill normal cells in the process of targeting cancer cells, or gene therapies which can cause genetic mutation, this capsule offers a safer method of cancer treatment with fewer side-effects.  

“The most desirable anticancer therapy is both potent and specific toward tumor cells,” the study authors wrote. “Many conventional small molecule chemotherapeutics do not discriminate between cancerous and normal cells, cause damage to healthy tissues, and are therefore unable to be administered at high dosage.”

Currently, there are no approved methods for delivering proteins to the intracellular compartment of cells, said Tang.

"It is a difficult problem to deliver the protein if we don't use this vehicle,” Tang said in a press release. “This is a unique way to treat cancer cells and leave healthy cells untouched."

Proteins and Their Role in Cancer Treatment

Proteins are made up of thousands of smaller units called amino acids and play a critical role in the structure and function of cells, as well as the “regulation of the body’s tissues and organs,” according to the National Institutes of Health’s Genetics Home Reference. In fact, because proteins have such a significant impact on the human body, scientists have used them as a basic method of treating cancer for years.

For this particular study, Tang said his team used apoptin, a protein complex derived from an anemia virus in birds, which accumulates in the nucleus of cancer cells and tells the cells to self-destruct.

“This protein can selectively cause apoptosis (cell self-destruction) in cancer cells, but leave normal cells unharmed,” Tang said.

According to the study, "when transgenically expressed, apoptin can induce p53-independent aptosis in a variety of tumor and transformed cells.” P53 is a well-known protein among scientists, and it was brought to the forefront of cancer research 20 years ago for its ability to “set things in motion” within a cell. According to a New York Times article published in December 2012, which discussed the possibility of a cure-all drug for cancer, it has long been the “the dream of cancer researchers….to reanimate p53 in cancer cells so they will die on their own.”

Apoptin has been lauded for its potency and selectivity, according to researchers. “Different gene therapy approaches have been used to administer apoptin to mouse tumor models, in which significant reduction in tumor sizes and prolonged lifespan of mice have been observed without compromising overall health,” the study authors wrote.

"Delivering a large protein complex such as apoptin to the innermost compartment of tumor cells was a challenge, but the reversible polymer encapsulation strategy was very effective in protecting and escorting the cargo in its functional form," said Muxun Zhao, lead author of the research and a graduate student in chemical and biomolecular engineering at UCLA, in a press release.

The Future of Cancer Treatment

While his experiment focused on a specific type of protein cargo, Tang said this tiny capsule strategy "should be generalizable to any protein that needs to traverse to the inside of cells.”

However, there is still much research to be done before this strategy becomes a standard method of cancer treatment. Tang said his team has been working on this project for the past four years with various collaborators and that they will continue to research “ways of more precisely targeting tumors, prolonging the circulation time of the capsules, and delivering other highly sought-after proteins to cancer cells."

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