University Times

Kill the body and the head will die, boxing trainers say.

Kill the molecular chaperone and the virus can no longer produce tumors, Jeffrey Brodsky says.

Brodsky, assistant professor of biological sciences, knows his line isn't catchy. But the process it describes may lead to a whole new approach toward treating AIDS and preventing cancers such as cervical cancer that are thought to be caused by viruses.

A timely collaboration between Brodsky and department chairperson James Pipas led to the new insight.

Pipas, a virologist, has been studying a monkey virus called SV40 for the last two decades. Since 1990, cell biologist Brodsky has been studying molecular chaperones, which he describes as "general helper" proteins that assist other proteins in doing their jobs properly within the cell. Molecular chaperones are present in nearly every cellular compartment in all organisms, from bacteria to humans.

When Brodsky came to Pitt in 1994, he and Pipas compared notes and found, after some experimentation, that their research overlapped.

Pipas recalls, "We showed that SV40, which is very similar to some human viruses that are thought to cause cancerous tumors, has a molecular chaperone that the virus brings with it when it invades healthy cells." "That was amazing," Brodsky says.

Why? Because normally, when a virus infects a cell it steals the machinery of the cell to make more virus. But SV40 wasn't co-opting the molecular chaperone regions of invaded cells. It was bringing its own.

"When you see something like that, especially in virology, you know it's got to be important," Brodsky says. "Why is this virus bringing its own molecular chaperone instead of using what's already there?" No one knows, yet. But by genetically altering the molecular chaperone area of SV40 — "basically, stripping out the DNA from this novel region of the virus, screwing it up and putting it back in the virus," as Brodsky phrases it — he and his Pitt research team have shown that molecular chaperone activity within SV40 is essential for the virus to cause cancer.

"We've proved that when you make mutations in that part of the virus, the virus can no longer produce tumors," Brodsky says. "This was the first demonstration that chaperone activity was required to cause tumors." James DeCaprio, a nationally known researcher at Harvard medical school's DNA-Farber Cancer Institute, called the research of Brodsky and Pipas "very important" because it may enable scientists to identify existing drugs, or develop new ones, to kill molecular chaperone activity in a number of harmful viruses, thus eliminating the viruses' capacity to cause tumors.

"Jeff and Jim's work is quite well known among cell biologists nationally. It's exciting stuff," DeCaprio said.

"The point is," Brodsky says, "we now have ways to screen for compounds — pharmaceuticals or whatever — that might kill the chaperone activity in this [SV40] virus. If you can find something that will kill it in the test tube, presumably you can kill it in the body." SV40 causes tumors in rhesus monkeys and mice. "Whether it will do that in humans is unclear, although it may in effect already have happened, unfortunately," Brodsky says. "SV40 recently made it into the popular press because it's thought that, at one point, early isolates of the polio vaccine were grown in monkey cells. We now know, or at least have good reason to fear, that some of these were contaminated with SV40." Whether or not SV40 has ever infected humans, viruses have been known to make the leap from monkeys to humans. While conspiracy theorists and a small minority of virologists disagree, the scientific community generally believes that the AIDS-causing HIV virus originated in monkeys and crossed the species boundary to humans.

Some human viruses are nearly identical to SV40, Brodsky points out. And experiments have indicated that at least two such viruses, BK and JC, likewise can't produce tumors unless the viruses' molecular chaperones are present.

"You and I probably are infected with these two viruses, but they're latent," Brodsky says. "However, if we become immuno-compromised — that is, if we develop AIDS or some other disease that attacks the body's immune system — it's easy for those viruses to become active, especially in the peripheral nerves.

"Ten percent of people with AIDS die of neuronal dementia because these viruses are activated in the nerves. That's one reason why these viruses are important to study." While Brodsky says his work has more immediate implications for AIDS research, the larger question that interests him is: How general is molecular chaperone activity in creating tumors? In an article in the July issue of the Journal of Virology, Brodsky speculated that many viruses, not just the few he's identified, require molecular chaperone activity to produce tumors.

"Until now, people haven't looked for this" process in investigating AIDS and cancer, he says.

Brodsky and his colleagues are screening various compounds in the hope of finding something that kills SV40. One process involves quick-breeding baker's yeast. (Remember, molecular chaperones are common to nearly all life forms.) "Genetically, we've killed the molecular chaperone in yeast and replaced it with the chaperone protein from SV40. That produces yeast that depend on this virus to live. So, if we add a compound and it kills these yeast but it doesn't kill normal yeast, we know the compound targets the virus." Brodsky's team also uses two other assays: a patented, test tube-based process developed at Pitt and another process involving genetic engineering in mice.

But all three processes are labor-intensive, and Brodsky admits to feeling frustrated.

"We really need collaborators and additional funding to take this research to the next level," he says. "We're especially interested in finding pharmaceutical companies to work with us. They have millions of compounds that they can routinely test in roboticized assays in an effort to find something to block this chaperone activity in viruses." So far, Brodsky has not found such a collaborator.

"Because of the possibly profound implications of this research, labs at Harvard, Stanford and MIT have expressed interest in what we're doing here at Pitt," Brodsky says. "We've spoken on chaperone research at national meetings.

"Recently, we submitted a proposal to the NCI [National Cancer Institute]. They said, 'We found your work novel, interesting, imaginative. But there's not enough preliminary data, so we won't fund it.'" On the brighter side, the University of Pittsburgh Cancer Institute provided funding for Brodsky's lab to hire a post-doctoral assistant for the current academic year. And Brodsky met recently with staff from Pitt's Office of Technology Management to discuss partnerships with the private sector.

"It's been a little disappointing," Brodsky understates. "But we'll keep plugging away."

–Bruce Steele