Posts tagged brain tumors

More than two decades ago, Ryan Vincent had open brain surgery to remove a malignant brain tumor, resulting in a lengthy hospital stay and weeks of recovery at home. Recently, neurosurgeons at Houston Methodist Hospital removed a different lesion from Vincent’s brain through a tube inserted into a hole smaller than a dime and he went home the next day.

Gavin Britz, MBBCh, MPH, FAANS, chairman of neurosurgery at Houston Methodist Neurological Institute, used a minimally-invasive technique to remove a vascular lesion from deep within the 44-year-old patient’s brain, the first to use this technique in the region. Traditionally, vascular lesions or brain tumors that are located deep within the brain can cause damage just by surgical removal.

“With this new approach, we can navigate through millions of important brain fibers and tracts to access deep areas of the brain where these benign tumors or hemorrhages are located with minimal injury to normal brain,” said Britz. “Ryan’s surgery took less than an hour.”

Houston Methodist neurosurgeons Britz and David Baskin, M.D., director of the Kenneth R. Peak Brain & Pituitary Tumor Center, are using this “six-pillar approach” that encompasses the latest technology in minimally-invasive surgeries — mapping of the brain; navigating the brain like a GPS system; safely accessing the brain and tumor/lesion; using high-end optics for visualization; successfully removing the tumor without disrupting tissues around it; and directed therapy using tissue collected for evaluation that can then be used for personalized treatments.

The new surgical technique is used to remove cancerous and non-cancerous tumors, lesions and cysts deep inside the brain. This approach reduces risks of damage to speech, memory, muscle strength, balance, vision, coordination and other function areas of the brain.

(Source: newswise.com)

Gene regulation technology increases survival rates in mice with glioblastoma

(Source: northwestern.edu)

Working with mice, Johns Hopkins researchers have discovered that weeks of treatment with a repurposed FDA-approved drug halted the growth of — and ultimately left no detectable trace of — brain tumor cells taken from adult human patients.

The scientists targeted a mutation in the IDH1 gene first identified in human brain tumors called gliomas by a team of Johns Hopkins cancer researchers in 2008. This mutation was found in 70 to 80 percent of lower-grade and progressive forms of the brain cancer. The change occurs within a single spot along a string of thousands of genetic coding letters, and is disruptive enough to keep the seemingly innocuous protein from playing its role in converting glucose into energy. Instead, the mutation hijacks the protein to make a new molecule not normally found in the cell, which is apparently a linchpin in the process of forming and maintaining cancer cells.

Encouraged by the new findings, described online Sept. 16 in the open-access journal Oncotarget, the Johns Hopkins researchers say they want to work quickly to design a clinical trial to bring what they learned in mice to humans with gliomas. Despite the growing understanding of IDH1 mutant gliomas, the development of effective therapies has proven challenging, they say.

"Usually in the lab, we’re happy to see a drug slow down tumor growth," says Alexandra Borodovsky, a graduate student in the Cellular and Molecular Medicine Program at the Johns Hopkins University School of Medicine who performed the experiments. "We never expect tumors to regress, but that is exactly what happened here."

"This therapy has worked amazingly well in these mice," says study leader Gregory J. Riggins, M.D., Ph.D., a professor of neurosurgery and oncology at the Johns Hopkins University School of Medicine. "We have spoken with neurosurgeons here, and as soon as possible, we want to start discussing the parameters of a clinical trial to see if this will work in our patients as a follow-up to surgery."

The researchers caution that many treatments have cured cancers in mice, and then failed in humans.

The IDH1 gene, whose name stands for isocitrate dehydrogenase 1, produces an enzyme that regulates cell metabolism. Mutations, or changes in the DNA code, force the IDH1 gene to increase production of a flawed version of the enzyme. The flawed enzyme produces large amounts of an entirely new molecule, called 2-hydroxyglutarate. This molecule is believed to cause groups of atoms called methyl groups to latch onto the DNA strand.

Although methylation is a normal cellular process, when too many methyl groups glom onto the DNA, Riggins says, this can interfere with normal cell biology and eventually contribute to cancer formation and growth.

Borodovsky, Riggins and their colleagues — including Timothy A. Chan, M.D., Ph.D., of Memorial Sloan-Kettering Cancer Center in New York — thought that a drug that could strip those methyl groups might be able to reverse the cancer process in those cancers with IDH1 mutations. They chose 5-azacytidine, which is approved to treat a pre-leukemia condition called myelodysplastic syndrome and is being tested on lung and other cancers at Johns Hopkins and elsewhere.

Riggins notes that one of the difficulties in developing treatments for IDH1 mutant brain cancers is finding a model in which to study them. Cell lines containing the IDH1 mutation are difficult to grow in the laboratory, for example. Borodovsky worked with Johns Hopkins neurosurgeons to obtain tumor cells from glioma patients likely to have IDH1 mutations and injected them under the skins of mice. She did this for months, before finally getting the tumor cells to grow.

Once the tumors grew, the researchers injected the mice with 5-azacytidine for 14 weeks and saw a dramatic reduction in growth and what appeared to be complete regression. Then they withdrew therapy. Seven weeks later, the tumors had not regrown. The researchers, however, said they do expect the tumors to regrow at some point, and are still monitoring the mice.

The type of tumor targeted by the researchers eventually progresses to a subtype of glioblastoma multiform — the deadliest form of brain cancer — known as progressive or secondary glioblastoma. They arise as a lower-grade glioma and are initially treated with surgery alone, but eventually they progress to the more lethal form of tumor. Survival is longer than with glioblastoma, but it is found in younger patients, those under the age of 50. While both types of tumor look the same at the end, they look very different at the molecular level, Riggins says, leading researchers to believe they may have a better chance at targeting the progressive tumors, which are more likely to have the IDH1 mutation.

Chan’s team at Sloan-Kettering simultaneously published a paper in Oncotarget, along with Borodovsky and Riggins, which describes similar results in a different animal model using a similar drug. This is further evidence that the strategy is a sound one, Riggins says.

(Source: eurekalert.org)

Scientists at the University of Alabama at Birmingham have identified a molecular pathway that seems to contribute to the ability of malignant glioma cells in a brain tumor to spread and invade previously healthy brain tissue. Researchers said the findings, published Sept. 19, 2013, in the journal PLOS ONE, provide new drug-discovery targets to rein in the ability of these cells to move.

Gliomas account for about a third of brain tumors, and survival rates are poor; only about half of the 10,000 Americans diagnosed with malignant glioma survive the first year, and only about one quarter survive for two years.

“Malignant gliomas are notorious, not only because of their resistance to conventional chemotherapy and radiation therapy, but also for their ability to invade the surrounding brain, thus causing neurological impairment and death,” said Hassan Fathallah-Shaykh, M.D., Ph.D., associate professor in the UAB Department of Neurology. “Brain invasion, a hallmark of gliomas, also helps glioma cells evade therapeutic strategies.”

Fathallah-Shaykh said there is a great deal of interest among scientists in the idea that a low-oxygen environment induces glioma cells to react with aggressive movement, migration and brain invasion. A relatively new cancer strategy to shrink tumors is to cut off the tumor’s blood supply – and thus its oxygen source – through the use of anti-angiogenesis drugs. Angiogenesis is the process of making new blood vessels.

“Stop angiogenesis and you shut off a tumor’s blood and oxygen supply, denying it the components it needs to grow,” said Fathallah-Shaykh. “Drugs that stop angiogenesis are believed to create a kind of killing field. This study identified four glioma cell lines that dramatically increased their motility when subjected to a low-oxygen environment – in effect escaping the killing field to create a new colony elsewhere in the brain.”

Fathallah-Shaykh and his team then identified two proteins that form a pathway linking low oxygen, or hypoxia, to increased motility.

“We identified a signaling protein that is activated by hypoxia called Src,” said Fathallah-Shaykh. “We also identified a downstream protein called neural Wiskott-Aldrich syndrome protein (N-WASP), which is regulated by Src in the cell lines with increased motility.”

The researchers then used protein inhibitors to shut off Src and N-WASP. When either protein was inhibited, low oxygen lost its ability to augment cell movement.

“These findings indicate that Src, N-WASP and the linkage between them – which is something we don’t fully understand yet – are key targets for drugs that would interfere with the ability of a cell to move.” said Fathallah-Shaykh. “If we can stop them from moving, then techniques such as anti-angiogenesis should be much more effective. Anti-motility drugs could be a key component in treating gliomas in the years to come.”

(Source: uab.edu)

Researchers at UT Southwestern Medical Center have identified a cellular switch that potentially can be turned off and on to slow down, and eventually inhibit the growth of the most commonly diagnosed and aggressive malignant brain tumor.

Findings of their investigation show that the protein RIP1 acts as a mediator of brain tumor cell survival, either protecting or destroying cells. Researchers believe that the protein, found in most glioblastomas, can be targeted to develop a drug treatment for these highly malignant brain tumors. The study was published online Aug. 22 in Cell Reports.

"Our study identifies a new mechanism involving RIP1that regulates cell division and death in glioblastomas," said senior author Dr. Amyn Habib, associate professor of neurology and neurotherapeutics at UT Southwestern, and staff neurologist at VA North Texas Health Care System. "For individuals with glioblastomas, this finding identified a target for the development of a drug treatment option that currently does not exist."

In the study, researchers used animal models to examine the interactions of the cell receptor EGFRvIII and RIP1. Both are used to activate NFκB, a family of proteins that is important to the growth of cancerous tumor cells. When RIP1 is switched off in the experimental model, NFκB and the signaling that promotes tumor growth is also inhibited. Furthermore, the findings show that RIP1 can be activated to divert cancer cells into a death mode so that they self-destruct.

According to the American Cancer Society, about 30 percent of brain tumors are gliomas, a fast-growing, treatment-resistant type of tumor that includes glioblastomas, astrocytomas, oligodendrogliomas, and ependymomas. In many cases, survival is tied to novel clinical trial treatments and research that will lead to drug development.

(Source: eurekalert.org)

Researchers at UCLA’s Jonsson Comprehensive Cancer Center have developed a new drug delivery system using nanodiamonds (NDs) that allows for direct application of chemotherapy to brain tumors with fewer harmful side effects and better cancer-killing efficiency than existing treatments.

The study was a collaboration between Dean Ho, professor, division of oral biology and medicine, division of advanced prosthodontics, and department of bioengineering and co-director of the Weintraub Center for Reconstructive Biotechnology at UCLA School of Dentistry and colleagues from the Lurie Children’s Hospital of Chicago and Northwestern University Feinberg School of Medicine.

Glioblastoma is the most common and lethal type of brain tumor. Despite treatment with surgery, radiation and chemotherapy, median survival time of patients with glioblastoma is less than 1.5 years. This tumor is notoriously difficult to treat in part because chemotherapy drugs injected on their own often are unable to cross the blood-brain barrier, which is the system of protective blood vessels that surround the brain. Also, most drugs do not stay concentrated in the tumor tissue long enough to be effective.

The drug doxorubicin (DOX) is a common chemotherapy agent that is a promising treatment for a broad range of cancers, and served as a model drug for treatment of brain tumors when injected directly into the tumor. Ho’s team originally developed a strategy for strongly attaching DOX molecules to ND surfaces, creating a combined substance called ND-DOX.
Nanodiamonds can carry a broad range of drug compounds and prevent the ejection of drug molecules that are injected on their own by proteins found in cancer cells. Thus the ND-DOX stays in the tumor longer than DOX alone, exposing the tumor cells to the drug much longer without affecting the tissue surrounding the tumor.

Ho and colleagues hypothesized that glioblastoma might be efficiently treated with a nanodiamond-modified drug using a technique called convection enhanced delivery (CED), by which they injected ND-DOX directly into brain tumors in rodent models.

The researchers found that the ND-DOX levels in the tumor were retained for a duration far beyond that of DOX alone. The DOX was taken into the tumor and stayed in the tumor longer when attached to NDs. ND-DOX also increased programmed cell death (apoptosis) and decreased cell viability in glioma (brain cancer) cell lines.

Their results also showed for the first time that ND- DOX delivery limited the amount of DOX that was distributed outside the tumor and reduced toxic side effects while keeping the drug in the tumor longer and increasing tumor-killing efficiency for brain cancer treatment. Treatment was more effective and survival time increased significantly in rats treated with ND-DOX compared to those given unmodified DOX. Further research will expand the list of brain cancer chemotherapy drugs that can be attached to the ND surface to improve treatment and reduce side effects.

“Nanomaterials are promising vehicles for treating different types of cancer,” Ho said, “We’re looking for the drugs and situations where nanotechnology actually helps chemotherapy function better, making it easier on the patient and harder on the cancer.” Ho adds that a project of this scale has been successful due to the multi-disciplinary and proactive interactions between his team of bioengineers and outstanding clinical collaborators from Northwestern and Lurie Children’s Hospital.

Ho went on to say that the ND has many facets, almost like the surface of a soccer ball, and can bind to DOX very strongly and quickly. To have a nanoparticle that has translational significance it has to have as many benefits as possible engineered into one system as simply as possible. CED of ND-DOX offers a powerful treatment delivery system against these very difficult and deadly brain tumors.

The study appears in the advance online issue of the peer-reviewed journal Nanomedicine: Nanotechnology, Biology and Medicine.

(Source: newswise.com)

NIBIB-funded scientists and engineers are teaming up with neurosurgeons to develop technologies that enable less invasive, image-guided removal of hard-to-reach brain tumors. Their technologies combine novel imaging techniques that allow surgeons to see deep within the brain during surgery with robotic systems that enhance the precision of tissue removal.

A robot that worms its way in

The median survival rate for patients with glioblastomas, or high grade primary brain cancer, is less than two years. One factor contributing to this low rate is the fact that many deep-seated and pervasive tumors are not entirely accessible or even visible when using current neurosurgical tools and imaging techniques.

But several years ago, J. Marc Simard, M.D., a professor of neurosurgery at the University of Maryland School of Medicine in Baltimore (UMB), had an insight that he hoped might address this problem. At the time, he had been watching a TV show in which plastic surgeons were using sterile maggots to remove damaged or dead tissue from a patient.

“Here you had a natural system that recognized bad from good and good from bad,” said Simard. “In other words, the maggots removed all the bad stuff and left all the good stuff alone and they’re really small. I thought, if you had something equivalent to that to remove a brain tumor that would be an absolute home run.”

Image: Initial prototype for the minimally invasive neurosurgical intracranial robot. Image courtesy of University of Maryland.

And so Simard teamed up with Rao Gullapalli, Ph.D., professor of diagnostic radiology and nuclear medicine also at UMB, as well as Jaydev Desai, Ph.D., professor of mechanical engineering at the University of Maryland, College Park, to develop a small neurosurgical robot that could be used to remove deep-seated brain tumors.

Within four years, the team had designed, constructed, and tested their first prototype, a finger-like device with multiple joints, allowing it to move in many directions. At the tip of the robot is an electrocautery tool, which uses electricity to heat and ultimately destroy tumors, as well as a suction tube for removing debris.

“The idea was to have a device that’s small but that can do all the work a surgeon normally does,” said Simard. “You could place this small robotic device inside a tumor and have it work its way around from within, removing pieces of diseased tissue.”

A key component of the team’s device is its ability to be used while a patient is undergoing MRI. By replacing normal vision with continuously updated MRI, the surgeon is able to visualize deep-seated tumors and monitor the robot’s movement without having to create a large incision in the brain.

In addition to reducing incision size, Simard says the ability to view the brain under continuous MRI also helps surgeons keep track of tumor boundaries throughout an operation. “When we’re operating in a conventional way, we get an MRI on a patient before we do the surgery, and we use landmarks that can either be affixed to the scalp or are part of the skull to know where we are within the patient’s brain. But when the surgeon gets in there and starts to remove the tumor, the tissues shift around so that now the boundaries that were well-established when everything was in place don’t exist anymore, and you’re confronted once again with having to distinguish normal brain from tumor. This is very difficult for a surgeon using direct vision, but with MRI, the ability to discriminate tumor from non-tumor is much more powerful.”

Steve Krosnick, M.D., a program director at NIBIB, says real-time MRI guidance during brain tumor surgery would be a tremendous advantage. “Unlike pre-operative MRI or intermittent MRI, which requires interruption of the surgical procedure, real-time intra-operative MRI offers rapid delineation of normal tissue from tumor while accounting for brain shifts that occur during surgery.”

But designing a neurosurgical device that can be used inside an MRI magnet is no easy task. One of the first issues you have to consider, said Gullapalli, is a surgeon’s access to the brain. “When you scan a person’s brain during an MRI, he’s deep inside the machine’s tunnel. The problem is, how do you get your hands on the brain while the patient’s in the scanner?”

The team’s solution was to give the surgeon robotic control of the device in order to circumvent the need to access the brain directly. In other words, a surgeon can insert the robot into the brain while the patient is outside of the scanner. Then, when the patient moves into the scanner, the surgeon can sit in a different room and –while watching MRI images of the brain on a monitor—move the robot deep inside the brain and direct it to electrocauterize and aspirate the tissue.

Jaydev Desai, the team’s mechanical engineer, says the most challenging aspect of the project has been designing a robot that can be controlled inside the magnetic field of an MRI. While robots are often controlled via electromagnetic motors, this was not an option because, besides being magnetic, these motors create significant image distortion, making it impossible for the surgeon to perform the task. Other potential mechanisms such as hydraulic systems were off the table due to concerns about fluid leakage.

Instead, Desai decided to use shape memory alloy (SMA)—a material that alters its shape in response to changes in temperature—to control the robot’s movement. In the most recent prototype—developed by Desai and his team at the Robotics, Automation, and Medical Systems (RAMS) laboratory at the University of Maryland, College Park—a system of cables, pulleys and SMA springs are used. This cable and pulley system is an improvement from their previous prototype which caused some image distortion.

Image: The newest prototype for the minimally invasive neurosurgical intracranial robot uses a system of pulleys and springs to move the robot. Source: Jaydev Desai, University of Maryland

With continued support from NIBIB, Desai and colleagues are now working to further reduce image distortion and to test the safety and efficacy of their device in swine as well as in human cadavers. Though it will be several years before their device finds its way into the operating room, Simard is excited by the prospect. “Advancing brain surgery to this level where tiny machines or robots could navigate inside people’s heads while being directed by neurosurgeons with the help of MRI imaging…It’s beyond anything that most people dream of.”

Scoping the brain

On the opposite side of the country, a different group of engineers and neurosurgeons is also working to develop an image-guided, robotically-controlled neurosurgical tool. Lead by Eric Seibel, Ph.D., a professor of mechanical engineering at the University of Washington, the team is attempting to adapt a scanning fiber endoscope—a tool initially developed by Seibel to image inside the narrow bile ducts of the liver—so that it can be used to visualize the brain during surgery.

An endoscope is a thin, tube-like instrument with a video camera attached to its end that can be inserted through a small incision or natural opening in the body to produce real-time video during surgery. Endoscopes are an essential component of minimally invasive surgeries because they allow surgeons to view the inside of the body on a monitor without having to make a large incision.

However, there are many parts of the body such as small vessels and ducts as well as areas deep in the brain that are inaccessible to conventional endoscopes. Although ultrathin endoscopes have recently been developed, Seibel says these smaller scopes come with the price of greatly reduced image resolution.

“Right now, with the current state of the art ultrathin endoscopes, I calculate based on the field of view and their resolution that the person looking at that display would see so little as to be classified in the US as legally blind,” said Seibel.

Image: Microfabricated optical fiber scanner emitting red laser light, with scan amplitude of 1 mm peak-to-peak. Image courtesy of Eric Seibel, University of Washington

But with support from NIBIB over ten years ago, Seibel began working on a new type of endoscope that could fit into tiny crevices in the body while retaining high image quality. His end product was a new type of endoscope that, despite having the diameter of a toothpick, can provide doctors with microscopic views of the inside of the body.

Seibel retained image quality while significantly reducing the size of his scope by eschewing traditional endoscope models. Instead of a light source and a video camera, Seibel’s scope consists of a single optical fiber—approximately the size of a human hair—located in the middle of the scope. The fiber releases white laser light (a combination of green, red, and blue lasers) when vibrated at a particular frequency. By directing the laser light through a series of lenses in the scope, it can be reflected widely within the body, providing a 100 degree field of view. As the white laser light interacts with tissue, it picks up coloration and scatters it back to a ring of additional optical fibers which transmit this information to a monitor.

“It’s almost like putting your eyes inside the body so you can see with the wide field view of your human vision,” said Seibel.

In collaboration with three neurosurgeons and an electrical engineer, Seibel is now working to secure his novel endoscope to the tip of a robotically controlled micro-dissection neurosurgical tool.

As opposed to larger traditional endoscopes, Seibel say his scanning fiber endoscope is barely noticeable.

“It’ s like a piece of wet spaghetti,” said Seibel. “It’s even smaller then a piece of wet spaghetti in diameter, but it feels like that. So when it is actually at the tip of the surgeon’s tool, the surgeon wouldn’t feel it dragging behind her.”

One advantage of having the endoscope under robotic control is that the brain can be imaged at a higher magnification.

“A surgeon couldn’t hold a microscope steady in her hand while performing surgery, but the robot can,” said Seibel.

Microscopic detail is essential when trying to determine the border between healthy tissue—which if removed could lead to neurological deficits—and cancerous tissue—which if left in the brain could allow a tumor to return.

Krosnick says he’s excited by the combination of high-quality imaging and robotic enabled micro-neurosurgery. “It addresses a critical need, which is to discern tumor margins at high resolution while minimizing disruption to normal structures.”

Seibel believes this discrimination between cancerous and healthy tissue could be enhanced even further by taking advantage of the fact that his scanning endoscope is also able to detect fluorescence. One of the main focuses of his current research is a collaboration with Jim Olson, M.D., Ph.D. at the Fred Hutchinson Cancer Research Center, who is the inventor of a substance called “tumor paint”.

Tumor paint is a fluorescent probe that attaches to cancerous but not healthy cells when injected into the body. Seibel says the ultimate goal would be to give a patient an injection of tumor paint and then use his endoscope to create an image of the fluorescing cancer cells as well as a colored anatomic image of the brain. The two images could then be merged on a screen for the surgeon to view during an operation.“You would be able to see all the structure that a surgeon would see, but you’d also see those molecular pinpoints of light that are cancer cells…and from there the robot can be used to resect, or remove, these small cells of cancer, and it can do it very precisely because you don’t have the shaking of a human holding it.”

Image: Tumor paint is made of a compound extracted from scorpion venom that can travel through the blood brain barrier and bind specifically to tumor cells. Source: iStockphoto

Seibel concluded by saying, “There’s a real niche for video-quality, high-resolution, multi-modal imaging that’s in a tiny package so that it can be put on microscopic tools for minimally invasive medicine. I really feel it’s an enabling technology that could move the whole field forward.”

Krosnick is enthusiastic about the progress the two teams have made so far. “These are innovative technologies that, if effective, could significantly add to the brain surgery armamentarium. They’re still early in development, but I think both show considerable promise.” He concluded by emphasizing that, like all new devices, these technologies would need to undergo a series of clinical trials to ensure that they are safe and effective before making their way into an operating room.

(Source: nibib.nih.gov)

In a breakthrough that could have wide-ranging applications in molecular medicine, Stanford University researchers have created a bioengineered peptide that enables imaging of medulloblastomas, among the most devastating of malignant childhood brain tumors, in lab mice.

The researchers altered the amino acid sequence of a cystine knot peptide — or knottin — derived from the seeds of the squirting cucumber, a plant native to Europe, North Africa and parts of Asia. Peptides are short chains of amino acids that are integral to cellular processes; knottin peptides are notable for their stability and resistance to breakdown.

The team used their invention as a “molecular flashlight” to distinguish tumors from surrounding healthy tissue. After injecting their bioengineered knottin into the bloodstreams of mice with medulloblastomas, the researchers found that the peptide stuck tightly to the tumors and could be detected using a high-sensitivity digital camera.

The findings are described in a study published online Aug. 12 in the Proceedings of the National Academy of Sciences.

“Researchers have been interested in this class of peptides for some time,” said Jennifer Cochran, PhD, an associate professor of bioengineering and a senior author of the study. “They’re extremely stable. For example, you can boil some of these peptides or expose them to harsh chemicals, and they’ll remain intact.”

That makes them potentially valuable in molecular medicine. Knottins could be used to deliver drugs to specific sites in the body or, as Cochran and her colleagues have demonstrated, as a means of illuminating tumors.

For treatment purposes, it’s critical to obtain accurate images of medulloblastomas. In conjunction with chemotherapy and radiation therapy, the tumors are often treated by surgical resection, and it can be difficult to remove them while leaving healthy tissue intact because their margins are often indistinct.

“With brain tumors, you really need to get the entire tumor and leave as much unaffected tissue as possible,” Cochran said. “These tumors can come back very aggressively if not completely removed, and their location makes cognitive impairment a possibility if healthy tissue is taken.”

The researchers’ molecular flashlight works by recognizing a biomarker on human tumors. The bioengineered knottin is conjugated to a near-infrared imaging dye. When injected into the bloodstreams of a strain of mice that develop tumors similar to human medullublastomas, the peptide attaches to the brain tumors’ integrin receptors — sticky molecules that aid in adhesion to other cells.

But while the knottins stuck like glue to tumors, they were rapidly expelled from healthy tissue. “So the mouse brain tumors are readily apparent,” Cochran said. “They differentiate beautifully from the surrounding brain tissue.”

The new peptide represents a major advance in tumor-imaging technology, said Melanie Hayden Gephart, MD, neurosurgery chief resident at the Stanford Brain Tumor Center and a lead author of the paper.

"The most common technique to identify brain tumors relies on preoperative, intravenous injection of a contrast agent, enabling most tumors to be visualized on a magnetic resonance imaging scan," Gephart said. These MRI scans are used like in a computer program much like an intraoperative GPS system to locate and resect the tumors.

“But that has limitations,” she added. “When you’re using the contrast in an MRI scan to define the tumor margins, you’re basically working off a preoperative snapshot. The brain can sometimes shift during an operation, so there’s always the possibility you may not be as precise or accurate as you want to be. The great potential advantage of this new approach would be to illuminate the tumor in real time — you could see it directly under your microscope instead of relying on an image that was taken before surgery.”

Though the team’s research focused on medulloblastomas, Gephart said it’s likely the new knottins could prove useful in addressing other cancers.

“We know that integrins exist on many types of tumors,” she said. “The blood vessels that tumors develop to sustain themselves also contain integrins. So this has the potential for providing very detailed, real-time imaging for a wide variety of tumors.”

And imaging may not be the only application for the team’s engineered peptide.

“We’re very interested in related opportunities,” Cochran said. “We envision options we didn’t have before for getting molecules into the brain.” In other words, by substituting drugs for dye, the knottins might allow the delivery of therapeutic compounds directly to cranial tumors — something that has proved extremely difficult to date because of the blood/brain barrier, the mechanism that makes it difficult for pathogens, as well as medicines, to traverse from the bloodstream to the brain.

“We’re looking into it now,” Cochran said.

A little serendipity was involved in the peptide’s development, said Sarah Moore, a recently graduated bioengineering PhD student and another lead author of the study. Indeed, the propinquity of Cochran’s laboratory to co-author Matthew Scott’s lab at Stanford’s James H. Clark Center catalyzed the project. “Our labs are next to each other,” Moore said. “We had the peptide, and Matt had ideal models of pediatric brain tumors  —mice that develop tumors in a similar manner to human medulloblastomas. Our partnership grew out of that.”

Scott, PhD, professor of bioengineering and of developmental biology, credits the design of the Clark Center as a contributor to the project. The building is home to Stanford’s Bioengineering Department, a collaboration between the School of Engineering and the School of Medicine, and Stanford Bio-X, an initiative that encourages communication among researchers in diverse scientific disciplines.

“So in a very real sense, our project wasn’t an accident,” Scott said. “In fact, it’s exactly the kind of work the Clark Center was meant to foster. The lab spaces are wide and open, with very few walls and lots of glass. We have a restaurant that only has large tables — no tables for two, so people have to sit together. Everything is designed to increase the odds that people will meet and talk. It’s a form of social engineering that really works.”

Scott said he is gratified by the collaboration that led to the team’s breakthrough, and observed that the peptide has proved a direct boon to his own work. About 15 percent of Scott’s mice develop the tumors requisite for medulloblastoma research. The problem, he said, is that the cancers are cryptic in their early stages.

“By the time you know the mice have them, many of the things you want to study — the genesis and development of the tumors — are past,” Scott said. “We needed ways to detect these tumors early, and we needed methods for following the steps of tumor genesis.”

Ultimately, Scott concluded, the development of the new peptide can be attributed to Stanford’s long-established traditions of openness and relentless inquiry.

“You find not just a willingness, but an eagerness to exchange ideas and information here,” Scott said. “It transcends any competitive instinct, any impulse toward proprietary thinking. It is what makes Stanford — well, Stanford.”

(Source: med.stanford.edu)