For decades the native prairie plant with tomato-like vines, and marbled-sized fruit covered in thin husks, has sprawled across the Kansas prairie in relative obscurity.
But scientists from around the world are now noticing the wild tomatillo, and wondering if it might provide a major medicinal breakthrough.
“We’ve found compounds from the wild tomatillo that have strong anti-cancer properties against breast cancer, skin cancer, thyroid cancer and brain cancer in our early studies,” said Mark Cohen, cancer physician and research scientist who has been working with the plant for more than two years.
“It’s very exciting because not only do those compounds occur naturally, but they’re more potent than some drugs currently on the market for these diseases.”
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Cohen said initial research has been done against human cancer cells in laboratory containers and mice. Things are progressing well enough that human-based trials could begin in about two years, he said.
It seems the deeper the botanists, medicinal chemists and cancer researchers dig into wild tomatillos, the more promise the prairie plant holds.
“We’ve found 15 new molecules in the plant previously not known to science,” said Barbara Timmermann, University of Kansas medicinal chemistry chair. “Nobody knew they existed and several of them are so active against cancer.”
And it’s not like this is some super-delicate plant from some far away corner of the Amazon.
Wild tomatillos, Physalis longifolia, are a tough, prolific prairie plant currently thriving over much of the central United States.
(They’re related to a domestic variety of tomatillo, but scientists don’t know if it has similar characteristics.)
But promised funding was abruptly cut less than halfway through the five-year research project.
“We are having fantastic data, and things are moving so well, then they just pulled the rug out from under us,” Timmermann said, of money from Heartland Plant Innovations. “It’s very unfortunate, and very disappointing.”
The Native Medicinal Plant Research Program began in 2010 as a joint venture using the strengths of the Kansas Biological Survey, the KU School of Pharmacy and the KU School of Medicine.
Timmermann and Kelly Kindscher, a biological survey senior scientist, have long seen the Kansas prairies as a potential pharmacy waiting to be explored.
“Everybody has been going to the rain forest and other exotic places for research,” said Timmermann, who has about 30 years of experience researching medicinal plants, “but we knew the Midwest had so many plants nobody had ever really looked at.”
Kindscher, a noted expert on America’s prairies, had also learned that for centuries native tribes were utilizing a number of plants for medicinal purposes before the state was settled.
“They weren’t collecting them randomly,” Kindscher said. “They’d learned what to use, and used them in many cases fairly effectively.”
He said modern research has shown most do indeed work.
Kindscher said any medicinal benefits found in plant compounds are mostly coincidental. Most are produced to protect the plant in some way or another.
“Plants can’t run and they can’t just grow spines if they don’t have them, so they need some kind of chemical defense against being eaten by insects or something,” he said.
They also may help them survive tough conditions, like floods and drought.
While Kindscher and crew eventually provided about 200 different species of prairie plants for testing, wild tomatillos quickly gained the most attention because of the findings in Timmermann’s lab.
As well as testing how the wild tomatillo compounds perform against cancer, the plants were also tested to see how they react to other kinds of human cells.
It would be possible, Cohen said, for a compound to be very aggressive against cancer but too toxic to healthy human cells to become a viable treatment.
Fortunately, that hasn’t been the case so far.
“It’s very exciting that (wild tomatillo compounds) do have a strong potency effect against cancer and do not have significant toxicity against other cells so far in our evaluations,” said Cohen, who is directing laboratory testing on the wild tomatillo compounds furnished by Timmermann.
Initially Cohen did so at the KU School of Medicine. He took the chores with him to a new job at the University of Michigan.
If all goes very well, Cohen said clinical trials with humans could begin within about two years. Wild tomatillo-based drugs could possibly hit the general market within about seven years.
It’s too early to know how the medicine could be administered, if it passes all testing and trials.
Cohen said it could probably be injected into patients.
An oral wild tomatillo extract could be another option.
Kindscher said some of the highest levels of cancer-fighting compounds are found in the plant’s fruit.
“The fruit is edible, and actually tastes very good,” he said, “especially when it’s ripe.”
Acquiring enough of that fruit shouldn’t be a problem in the future.
Wild tomatillos are so common Kindscher referred to them as “a common field weed” that grows on native prairies, pastures and farmlands, roughly from New Mexico to Montana and as far east as Ohio.
“It’s probably one of the few (prairie) plants that are doing about as well as ever,” he said. “It’s common because it can grow in a lot of areas. Unlike a lot of prairie plants it does well on disturbed soils.”
He said it grows well along roadsides or where the soil has been scarred by livestock.
It’s common in farm fields, too. Kindscher is certain it could be grown commercially, too.
The perennial plant has proven to be hardy to temperature and rainfall extremes.
But one thing this miracle plant cannot do, is pay for its own research. All three scientists said funding is now their greatest worry.
Timmermann said Heartland Plant Innovations originally agreed to pay $5 million over five years to fund the research.
Heartland is a Manhattan-based bio-technology company backing plant-based research. In the spring, nearing the end of the program’s second year, Timmermann was told funding would stop immediately.
“This just comes at a very bad time,” she said. “This is when we should be growing.” Currently the program is running on funding she’d saved from the previous two years.
Forrest Chumley, Heartland Plant Innovations’ president, said the decision to stop the funding at about $2.5 million was a business decision.
“We’re a for-profit company so we focus on projects where we can make the greatest difference. We’ve decided it’s time to really focus on wheat development,” he said. “We’re really proud of what (the Native Medicinal Plant Research Program) has accomplished, and think it has great potential.”
Chumley said budget cuts to the state-financed Kansas Bioscience Authority, one of his main sponsors, also left his group with less money.
Researchers are now searching for further funding.
“It’s very exciting that this may represent some new cancer drugs,” Cohen said. “Unfortunately our biggest challenge is now acquiring more funding so we can move things to the next level.”