College of Agricultural and Life Sciences

College of Agricultural and Life Sciences

Above ↑ Mark Shahan, of Quintessence Biosciences, is helping develop a powerful cancer treatment using knowledge generated in the campus lab of biochemist Ron Raines. Raines found a way to alter an enzyme so that it destroys cancer cells while leaving healthy cells alone.

Toxic in a Good Way

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A reworked enzyme kills cancer cells but lets healthy cells live

Imagine a drug that stops some cancers at their source — cleaving the very genetic material they need to replicate — but leaves healthy cells untouched. It may seem like science fiction, but two versions of the drug are now under development.

One is further along — already in the third phase of human trials for treating lung cancer — but the second drug shows promise of being even more effective.

That’s important news in Wisconsin, because that’s where the second drug is being developed. It is based on findings made in a College biochemistry lab and is being developed by a Madison firm.

The story centers around Ron Raines, a biochemistry professor in the College for more than 15 years, who works with enzymes.

“Enzymes fascinate me because they are the crossroads of chemistry and biology. They’re how nature does chemical reactions,” says Raines.
Raines has been working at the intersection of the two disciplines since his undergraduate days at M.I.T., where he studied chemistry and biology.

“By working where chemistry and biology meet, you can make a huge impact on science, because you can make molecules with properties that are not provided by nature — or by chemical supply companies. You can ask questions you couldn’t ask otherwise.”

It was during his undergraduate years that Raines got his first chance to work in research labs. That experience led him to Harvard, where he earned a Ph.D. in organic chemistry, and then to a fellowship at the University of California-San Francisco that included a stint at a biotechnology company.

By the time he came to Madison in 1989, he brought an appreciation for industry, expertise in recombinant DNA technology, and the foundation for a research program centered around an adroit molecule called ribonuclease.

What a cell creates, it must destroy

Ribonuclease is an enzyme that degrades RNA, which is an essential cell function. RNA is the genetic material that tells cells how to build proteins. It is also what some viruses, including certain types of cancer, use to replicate.

As Raines puts it, “Everything that’s created in a cell must also be destroyed — by destroying RNA we can interrupt the flow of information in a cell.”

Raines works mostly on ribonuclease A, a bovine enzyme made in the pancreas and likely involved in digestion. All vertebrates have some equivalent of ribonuclease A, says Raines — the human version is ribonuclease 1 — but cow ribonuclease is readily available and has been widely studied. During his San Francisco fellowship, Raines cloned for the first time the gene that codes for ribonuclease in cows.

Scientists have known since the 1950s that mammalian ribonuclease is toxic to certain types of cancer, but only in quantities too large to be useful from a clinical standpoint. In the early 1990s, a researcher discovered that ribonuclease from the Northern Leopard Frog is also toxic to cancer cells — at a much lower dose. Subsequent work with frog ribonuclease has led to a new drug, Onconase, which is now in Stage III human trials for treating lung cancer.

This discovery piqued Raines’ curiosity. He wondered why an enzyme from a frog was toxic to cancer while a very similar enzyme from a cow was not.

The answer, he suspected, lay in an inhibitor protein that cells use to prevent ribonuclease from cleaving RNA.

“It binds to ribonuclease incredibly tightly and keeps it from destroying RNA,” he explains. “The cells in your body use the protein to suppress the action of ribonuclease until it is needed.”

Inhibiting the inhibitor

Raines then looked for a way to disrupt the interaction. He concentrated on the way the molecules come together. When molecules interact — like ribonuclease and the inhibitor protein — they snap in place like puzzle pieces, fitting together at key sites.

Raines wanted to see if he could disrupt this binding by tweaking the ribonuclease molecule. His research team added what he calls a “bump”—a small extra molecule — to a crucial binding site on the ribonuclease. The bump blocked the protein from attaching, making the altered ribonuclease more evasive to the inhibitor. What’s more, tests showed that the new ribonuclease was toxic to cancer cells at a low to moderate dose.

“The more evasive we make the ribonuclease, the more toxic it is to tumor cells,” says Raines. “We don’t yet know exactly why ribonuclease is toxic to cancer cells and not regular cells, but it’s an ongoing area of research in our lab.”

After his initial success, Raines worked with Julie Mitchell, a fellow biochemist who has a joint appointment in mathematics, to subtly adjust the ribonuclease molecule to make it even more evasive. Mitchell designed a computer program that analyzes protein-to-protein interfaces and was able to spot areas where the two molecules fit tightly together. Raines’ team then altered structure in these regions to decrease the likelihood of a good fit between the molecules.

“The region that she identified as most promising was the region we had already discovered,” says Raines, “but she was able to identify some other regions we had not yet explored, and those have turned out to be very fruitful. We now have molecules that are three-fold more toxic than Onconase to tumor cells in a test tube and have been working well in animal tests.”

In addition to being more toxic, Raines’ altered enzyme may also be a better drug than Onconase because it comes from mammalian cells.

“Your immune system is programmed to treat your own proteins as friends,” he explains. “That’s not true of proteins from foreign sources. It’s known that Onconase can cause toxicity to kidneys, but all tests so far on mice indicate that the mammalian ribonucleases have been much better tolerated.”

From discovery to drug

Raines conducted the basic research on ribonuclease at his campus lab, with funding from the state of Wisconsin and the National Cancer Institute. His findings were then licensed through the Wisconsin Alumni Research Foundation by a firm called Quintessence Biosciences, which Raines founded with his wife, Laura Kiessling, also a professor of biochemistry and chemistry.

“I’ve always been interested in practical applications to my work,” Raines says. “As a scientist I study nature, and it never becomes uninteresting. But I also like things I do to have a practical application that I can see in my lifetime.”

Raines took a sabbatical from the university to get the company up and running, and then recruited Ralph Kauten, the former president and chairman of PanVera Corporation in Madison, to act as CEO. The company is run independently of the UW-Madison, and no Quintessence employee has worked on campus.

Raines says that he chose to license his own technology because he believes in the promise it holds. “It became clear to me that there might be an important commercial application for this work,” he says. “And I felt that given my background, I was in a position to be able to move it along.”

The biochemistry department, the College and the UW-Madison have been a good match for Raines and have helped to advance his work, he says.

"Wisconsin fosters interdisciplinary research and the faculty and administration work well together. This has been a key to my research success."