I am lying on a gurney being wheeled into an outpatient operating room, in part because of Stanley Lada, a coal miner who died in 1944, three years before I was born. This procedure is no big deal, I keep telling myself. No. Big. Deal. Really. And honestly it isn’t. Nonetheless, during the intake procedure the nurse raises her eyebrows at my blood pressure. “You’re a little nervous, aren’t you?” she notes. And, because of Stanley Lada, the honest answer is “Uh-hunh."
The orderly pushes the gurney down a long corridor, then through double doors into a brightly lit room, where a doctor and two nurses in surgical scrubs await. We introduce ourselves, engage in a minute or two of small talk, and then it’s down to business. I turn on my side, and the nurse injects a liquid into the IV shunt in my wrist. It feels like cold water splashing on top of my hand. And then . . . without skipping a beat it seems to me, the doctor shows me a color photo of the insides of a pink vacuum-cleaner hose.
“Some of my patients actually frame these as souvenirs,” he says as he hands me the photo.
I feel a little woozy, not from any drug that’s been administered but from the out-of-body experience of looking deep within my own body. The pink vacuum-cleaner hose is, in fact, the interior of my own large intestine, my colon.
“We found two small polyps and took care of them,” my gastroenterologist says. “You’ll get a pathology report in the mail. But I wouldn’t worry; they looked fine.” And when the report comes a few days later that’s exactly what it says. Stanley Lada, however, wasn’t so lucky. I am acutely aware that my grandfather died from colon cancer at precisely my age, and therefore of my need to be screened regularly for the disease since I may be at slightly higher risk.
This is my second colonoscopy, a procedure in which a tiny hollow tube with a light and video camera has been snaked up my internal plumbing, allowing a doctor to visually inspect my innards for polyps, small nodules that for unknown reasons sometimes form and sometimes become cancerous. I feel absolutely no discomfort afterward, even though the doctor has snipped off two polyps with tiny clippers attached to the scope. As promised, the IV sedative induced a blip of amnesia that erased any recollection of a procedure which lasted less than an hour. All I experienced of the colonoscopy was the cold splash of the IV and the doctor handing me the photo. That’s it. No big deal, just like I said.
Colon cancer, however, is a big deal. After lung cancer, it is the second-leading cause of cancer deaths in the United States. More than 130,000 new cases are diagnosed annually, while the disease claims 56,000 lives a year. Among them are the rich and the famous, like Charles Schulz, creator of the Peanuts comic strip, former Israeli foreign minister Moshe Dayan, Jackie Gleason and Audrey Hepburn, as well as the poor and unknown like Stanley Lada. By all rights, however, the death toll shouldn’t be nearly so high, since colon cancer is among the most treatable and curable cancers if caught early enough. And there’s the catch. Most fatal cases are not discovered early.
Which brings us back to colonoscopies and other screening methods. Typically colon cancer forms first in a polyp that, if it is cancer-prone, takes from five to 15 years to morph to a cancerous state, giving ample opportunity to interrupt the process through surgery, radiation and/or chemotherapy. Since the disease rarely strikes before 50, doctors recommend screening begin at that age.
With its 94 percent success rate in detecting cancer and ability to remove suspect polyps, the colonoscopy remains the gold standard of screening tests over such methods as the fecal occult blood test, which detects telltale traces of blood in the stool; the barium enema, used to make an X-ray image of the colon; and the sigmoidoscopy, which is similar to a colonoscopy but examines only the lower colon and rectum.
Arguably, colonoscopy remains even superior to such recent advances as the new DNA test for colon cancer and the virtual colonoscopy, which employs a CT or MRI scan of the colon. The DNA test is about 30 percent less accurate than conventional colonoscopy, while virtual colonoscopy can miss small polyps—although smaller polyps rarely are cancerous—and it cannot take tissue samples or remove polyps.
Nonetheless, while colonoscopy may be the current gold standard, it is not the ideal screening test. Like anything gold, it’s expensive. Colonoscopies, which are covered to some extent by Medicare and most insurance plans, can cost anywhere from $800 to $1,600, and obviously are costly in terms of time and skilled-labor. Beyond that, although extremely rare, there is a remote chance of complication. Finally, notwithstanding my testimonial, many people are squeamish because the procedure is invasive and requires clearing your digestive tract.
The bottom line is that for all the above reasons and more, the number of people getting screened is not as high as it should be. And so the race is on among colon-cancer researchers to find a superior replacement, something that is fast, accurate, simple and cheap.
Of mice and men
Some unusual mice from Notre Dame’s Walther Cancer Research Center, a unit of the Notre Dame Cancer Institute, give Rudy Navari and Mary Prorok hope that just maybe they are on to something.
Navari is director of the Notre Dame Cancer Institute as well as assistant dean and director of the Indiana University School of Medicine at South Bend. If that weren’t enough, the M.D., who also holds a Ph.D. in chemical engineering, is actively involved in several research programs, including one looking for the “magic bullet” colon-cancer biomarker that might become the basis of a fast, accurate, simple and cheap blood or urine test for the disease. A biomarker is a certain protein associated with a particular cancer. For various reasons tumors may secrete some proteins, so if you can detect the marker protein in blood or urine you should have an early warning of the cancer. That’s the theory.
“Finding a biomarker is kind of a needle-in-the-haystack thing; you have to be a little lucky,” says Prorok, a Walther Center protein chemist whom Navari enlisted to oversee the project. To find that needle, the Notre Dame research team has employed a sophisticated technique known as transcriptional profiling. This allows them to genetically compare diseased tissue with normal tissue, sorting out which genes are turned on, or “up-regulated,” in the disease state versus the healthy state.
Every cell has the same DNA blueprint in its genes. What makes one type of cell different from another—skin from bone, say—is which genes get “up-regulated,“causing a specific protein to be produced. RNA is the key compound in this process. “So we’re looking for RNAs in cancer cells that are either ’up’ or ’down,’” Prorok explains. “That would indicate either the presence of a marker or the absence of something.”
Transcriptional profiling allows researchers to scan thousands of gene interactions at a time. In fact, so great is the number that a mathematician is part of the team charged with statistically interpreting which are the dependable “up” and “down” regulated signals.
Initially, the researchers started their biomarker quest by analyzing cancer patients’ urine for telltale proteins. “That turned out to be a mess,” Prorok recalls, “because the patients were on a variety of different medicines and so we had a difficult time sorting out what was showing up in the urine."
After that false start the team decided to switch to a simpler, more easily controlled system, namely some special Walther Center mice that have a genetic defect which causes them to spontaneously develop polyps and colon cancer at about 60 days of age. “It’s a fairly decent model of the human condition,” Prorok says.
Soon after the switch good things began to happen. The biochemists found several genes that were “very much up-regulated” in the diseased mice. One protein in particular, called cathepsin E, caught their attention. While little is known about its normal function, it doesn’t appear essential for life. A strain of mice genetically engineered without the gene shows signs of dermatitis and a few minor problems but otherwise survives quite well.
What excited Navari, Prorok and their colleagues about cathepsin E is that while it is almost imperceptible in healthy mouse colon tissue, in diseased mice the levels are “absolutely explosive” and it’s always there. A red chemical stain that binds with cathepsin E showed red-stained cells, indicating the protein in every slide of mouse colon-cancer tissue—a phenomenal 100 percent hit rate.
“Whether this particular protein is a cause of the cancer—which I don’t think it is—or whether it is a consequence is almost immaterial,” Prorok says. “The fact that it is so strongly linked to the disease makes it an excellent candidate for a screening test."
But staining a mouse tissue sample 100 percent of the time for cancer is one thing, serving as an accurate screening test in a person is quite another. When it moves to the human realm, cathepsin E proves to be “promising” but not quite as phenomenally predictive as with mice. In human tumor samples the protein pops up about 50 percent of the time. The ND researchers aren’t sure exactly why the disparity, but Porok points out, “All of our mice get the same cancer in the same way; they all have the same genetic defect. In humans there may be many genetic reasons, environmental triggers, all sorts of unknown things that could cause the cancer."
Still, cathepsin E is promising enough to warrant the next step, looking for signs of the protein in mouse blood or urine. That task is daunting since a mouse supplies only about 3/100 of an ounce of blood, and getting a urine sample from the rodent obviously is tricky. Prorok and her colleagues have been up to the challenge, however, and were encouraged to find a fragment of cathepsin E in some preliminary analyses of mice pee.
“We’re hopeful that maybe we have a handle on something here,” she says. “The goal is a biomarker that is 95 percent reliable, so we’re not there yet. But this is a start, a validation of the approach."
A further benefit of the biomarker work is that a genetic fingerprint of the disease begins to emerge. “We’re already seeing clusters of genes that seem to go awry in both the human and mice samples,” Prorok notes.
Navari says in the future Notre Dame researchers hope to look for an overlap between the colon-cancer genetic profile in mice and humans. “And then, eventually, working with Notre Dame Keck Center for Transgene Research, we can see if we might be able to knock out these genes and possibly prevent colon cancer,” he says.
The future of cancer treatment lies in such targeted therapy, the Notre Dame Cancer Institute director continues. “We know, for instance, that some families develop colon cancer between 25 and 35 years of age because of a certain folding of a protein. But if you could somehow alter that amino-acid sequence without causing other damage, then maybe you could prevent that from ever developing, from being expressed in that person’s life."
Short of the ultimate goal of eradicating colon cancer outright, researchers continue to hunt for more effective drugs to combat the disease and improve survival. Sometimes that search leads in exotic directions.
Harvesting sea slugs
Unless you’re a World War II history buff versed in arcane details of the conflict, like where the legendary Indiana war correspondent Ernie Pyle lost his life, you’ve probably never heard of Ie Jima. John Kane ’03Ph.D. certainly hadn’t. However, several summers ago, the Notre Dame chemistry grad student found himself on a flight to the tiny South Pacific volcanic island near Okinawa, dispatched there by his adviser, Professor Paul Helquist, to gather as many specimens as possible of the sea slug Eudistoma cf. rigida, which lives on coral reefs around the island.
When he got there, Kane enlisted local divers to harvest the slugs, which look like lumps of tar. He spent the remainder of his time slicing and dicing the creatures they brought him, treating them with a variety of solvents, filtering and purifying the liquid. From 45 pounds of slugs he returned to Notre Dame with 1/3,000 of an ounce of a curious chemical brew of four related compounds known collectively as iejimalides (pronounced ee-ay-jeema-lides), after the island.
The rare substances are part of a broad category of naturally occurring compounds known as macrolides, which have been a source of antibiotics and anti-cancer drugs. The iejimalides were discovered in the late 1980s by a Japanese chemist who had worked out their gross chemical structure and reported the compounds’ potency against a few cancer-cell lines. There had been little follow-up until Helquist, who has had a research interest in macrolides for years, decided to investigate them more closely.
With the rare samples safely back at Notre Dame, work began in earnest to understand the intricacies of the compounds’ chemical structure and whether they might be a potential anti-cancer drug. Testing the compounds against various cancer cell lines, researchers found them incredibly potent, with just one-billionth of an ounce enough to stop cell growth. “Cells don’t aggregate any more when they come in contact with iejimalides; they just float freely and stop growing and dividing,” Helquist notes. Within dose ranges typically used for cancer drugs, he adds, the compounds have not been toxic to mice.
Still more positive news: The sea-slug compounds have shown some level of activity against more than 60 different cancer-cell lines, but for some reason seem most potent against colon-cancer cells. On that score, one of the leading cancer drug researchers in the country, Professor George Pettit of Arizona State University, after examining a sample provided by Helquist, wrote the Notre Dame biochemist and said, “Good news. This compound is a winner."
As encouraging as that assessment may be, the compounds still remain a long way from becoming a drug, if ever. Many more studies are needed to thoroughly characterize the compounds: Do they work in an organism as well as a cell culture? What dose is required? What happens when the compound gets into the organism? How is it broken down and excreted? Once those questions are answered for mice, they need to be replicated in other organisms, working up the ladder to humans.
The main thing hampering progress on the iejimalides at this point, however, is their rarity. Researchers can’t get their hands on enough of the stuff. As a result of the Notre Dame work, for instance, the National Cancer Institute became interested in the compounds and requested larger quantities for its own studies. Remedying the dearth in supply is now a focus of the Helquist lab on two fronts.
After years of work, especially by Kane and researcher Dirk Schweitzer, the Notre Dame group is on the verge of completing the first total synthesis of the substance. That should do a lot to alleviate the shortage. Meanwhile, attacking the same problem from a different direction, members of the lab returned this past summer to gather iejima slugs a fifth time. They were not interested in the slugs themselves but any microrganism that may co-exist with them and may be the actual source of the active compound.
“The real source may not be the slug,” Helquist says. “There are many cases where very potent compounds actually are produced by a symbiotic creature—something that co-exists with the main organism, perhaps a bacterial species, fungus or algae. So if there is some microorganism responsible and we can isolate it and grow it back here in the lab, we could have an ongoing supply of the active compound.” Scientific progress often requires chasing down such “ifs."
Meanwhile, a vote of confidence and a hopeful sign: This past May, three drug companies inquired into the Helquist lab’s iejimalide work. Could a sea slug actually become a weapon against colon cancer? Maybe, just maybe.
John Monczunski is an associate editor of this magazine.