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A team of University of Texas Researchers have found that thiabendazole slows down growing tumors and could possibly be used as chemotherapy for cancer.

Researchers found the discovery by exploiting the evolutionary relatedness of yeast, frogs, mice and humans.

The findings were published in the journal PLOS Biology.

Thiabendazole is an inexpensive, FDA-approved, generic drug taken orally that has been in clinical use for 40 years as an antifungal, but is not currently used for cancer therapy.

The researchers found that the drug destroys newly established blood vessels, making it a "vascular disrupting agent." 

In mice, thiabendazole decreased blood vessel growth in fibrosarcoma tumors by more than a half. Fibrosarcomas are cancers of the connective tissue, and they are generally heavily vascularized with blood vessels.

Inhibiting blood vessel, or vascular, growth can be an important chemotherapeutic tool because it starves tumors. Tumors induce new blood vessel formation to feed their out-of-control growth.

Researchers called the findings exciting because of the possibility of the first human-approved vascular disrupting agent. They say thiabendazole could be used clinically in combination with other chemotherapies.

The researchers previously found genes in single-celled yeast that are shared with vertebrates by virtue of their shared evolutionary history. In yeasts, which have no blood vessels, the genes are responsible for responding to various stresses to the cells. In vertebrates, the genes have been repurposed to regulate vein and artery growth, or angiogenesis.

Researchers searched for a molecule that would inhibit the action of those yeast genes and found that thiabendazole did the trick. They then tested the drug in developing frog embryos. These are fast growing vertebrates in which scientists can watch blood vessel growth in living animals.

Frog embryos grown in water with the drug either didn't grow blood vessels or grew blood vessels that were then dissolved away by the drug. Interestingly, when the drug was removed, the embryos' blood vessels grew back.

The drug was tested on human blood vessel cells growing in Petri dishes, finding that the drug also inhibited their growth. Finally, they tested the drug on fibrosarcoma tumors in mice and found that it reduced blood vessel growth in the tumors as well as slowed the tumors' growth.

"We didn't set out to find a vascular disrupting agent, but that's where we ended up," said Wallingford, associate professor of developmental biology and Cha's graduate advisor with Marcotte. "This is an exciting example of the power of curiosity-driven research and the insights that can come from blending disciplines in biology."

The scientists' goal is now to move the drug into clinical trials with humans. They are talking with clinical oncologists about next steps.

They said they hope the clinical trials will be easier because it is already approved by the FDA for human use.