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Natural killer cell
destroying a cancer cell
Image by Joshua Stokes

Researchers have looked to deep-sea creatures with the goal of creating a better cytotoxicity assay.

The team harnessed the power of enzymes responsible for marine animal bioluminescence to create the “Matador assay,” which can be used to determine whether cellular and immune-therapeutic agents are actually killing target cells.

The researchers said the Matador assay is quick and simple as well as “highly sensitive,” with the ability to detect cytotoxicity induced by several types of therapies.

Preet M. Chaudhary, MD, PhD, of the University of Southern California Keck School of Medicine in Los Angeles, and his colleagues described the assay in Scientific Reports.

“One of the most promising areas in cancer research is immunotherapy. . .,” Dr Chaudhary said. “It is also one of the most difficult because the methods for testing immunotherapies are not ideal.”

“Radioactive chromium release assay is the gold standard for testing whether an immunotherapy kills cancer cells. This method is expensive, complicated, and requires special disposal practices. Other available methods also suffer from limitations and don’t allow scientists to rapidly screen immunotherapeutic agents to find the best candidates.”

Dr Chaudhary and his colleagues set out to develop a simple, precise, and inexpensive cytotoxicity assay based on marine animal luciferases, the enzymes responsible for bioluminescence.

The team used a group of small crustaceans and deep-sea shrimp, which were selected for their bright bioluminescence. Their luciferases became the basis of the Matador assay.

Engineered to get trapped inside cells, the luciferases leak out of cells when they die, causing a visible glow. The level of luminescence can then be measured with a luminometer.

To test the Matador assay’s effectiveness at measuring cell death, the researchers used several types of cancer cells, including chronic myelogenous leukemia, acute myelogenous leukemia, Burkitt lymphoma, and solid tumor cells.

The team treated these cells with a variety of therapies, including chimeric antigen receptor (CAR) T cells, bispecific T-cell engagers, monoclonal antibodies, and natural killer cells.

Results showed the Matador assay could detect the death of a single cell, a level of sensitivity superior to that of existing cytotoxicity assays.

The researchers also pointed out that the Matador assay is fast, inexpensive, and can be performed in a 384-well plate format, saving time and reagents.

“In our hands, the Matador assay can detect cell death in as little as 30 minutes, which can ultimately translate to more expedient treatments for patients getting cellular immunotherapies such as CAR T cells,” Dr Chaudhary said.

In fact, Dr Chaudhary’s lab has developed more than 75 cancer cell lines expressing the marine luciferases and used them with the Matador assay to develop next-generation CAR T cells.

Dr Chaudhary believes the Matador assay has many potential applications in biomedical research and cellular therapy manufacturing.

“It could potentially play a role in screening other types of anticancer agents or even measuring environmental toxins,” he said.

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