What Frogs Can Teach Us About Tumors

Researchers at the University of Rochester School of Medicine and Dentistry are using frogs as a model to study human diseases. These frogs, called South African clawed frogs or Xenopus laevis, may not resemble humans on the outside, but they are very similar on a genetic level.

The School of Medicine and Dentistry houses the largest X. laevis research resource in the world, with many genetically modified animals that have undergone special testing that makes them well suited for research on the immune system. Jacques Robert, Ph.D., professor of Microbiology and Immunology, coordinates the Xenopus Research Resource, which provides materials, animals, and training for researchers across the globe.

Robert uses the X. laevis model to better understand the minute details of how tumors grow and how the body reacts. “We still have a lack of understanding of the environment inside tumors. A tumor is not just tumor cells, there are a lot of normal cells from the invaded organ and immune cells that infiltrate the tumor – and all of this changes as the tumor grows. We need to analyze this in real time,” says Robert. The tadpoles’ transparent skin makes them an advantageous model for imaging tumors as they grow.

In a paper recently published in Developmental Biology, Robert and his colleagues transplanted tumor cells into tadpoles, which developed into semi-solid tumors that spread throughout the tadpole over the course of a few weeks. In mammals, growth and spread of tumors requires reorganization of the structural supports that surround the cells. Robert plans to use his new semi-solid tumor model in tadpoles to understand how these supports are modified and how that promotes tumor growth and spread.

Tumors also recruit and exploit immune cells for their own protection. “Tumors are very good at modifying whatever immune cells come at them,” says Robert. He plans to use the X. laevis model to view the interaction between tumor cells and immune cells to understand how the tumor induces certain immune cells to suppress the rest of the immune system.

Robert’s research in X. laevis may also shed new light on how tumors grow blood vessels, which help the tumor grow and thrive by delivering essential nutrients through the bloodstream. In tadpoles, large blood vessels from the body enter the tumors and branch into smaller disorganized vessels - similar to what happens in mammals. Robert believes the disorganization of tumor vessels may be the reason chemotherapies delivered in the bloodstream are not fully effective. Understanding how tumor vessels grow may uncover ways to inhibit vessel growth and starve the tumor, or better ways to deliver chemotherapies.

While much of Robert’s research benefits humans, he is also interested in understanding diseases that affect amphibians, fish, and reptiles, such as ranaviruses. These viruses commonly infect cultured fish and have contributed to the decline of amphibian populations around the world. Robert will discuss this work at the Science on the Edge lecture series at the Rochester Museum and Science Center this Thursday, January 7 at 6:30 p.m., followed by a meet and greet session. 

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The University of Rochester Medical Center is home to approximately 3,000 individuals who conduct research on everything from cancer and heart disease to Parkinson’s, pandemic influenza, and autism. Spread across many centers, institutes, and labs, our scientists have developed therapies that have improved human health locally, in the region, and across the globe. To learn more, visit http://www.urmc.rochester.edu/research.