Speak Friend and Enter: How Cells Let the Right Travelers through their Doors

For decades, it’s been a molecular mystery that scientists were seemingly unable to solve: how do large molecules pass through the cell and into the nucleus, while others half their size remain stranded outside?

These are nuclear pores imaged by atomic force microscopy, appearing as a craterlike landscape in which each crater corresponds to a pore of ~100 nm diameter. [Credit: UCL]

Nuclear pores imaged by atomic force microscopy, appearing as a crater-like landscape in which each crater corresponds to a pore of ~100 nm diameter. [Credit: UCL]

But as reported in the latest issue of Nature Nanotechnology, researchers now believe they may have cracked the case. By shedding light on this strange anomaly, University College London (UCL) scientists have opened the door for one day delivering gene therapies directly into the nucleus. With numerous research teams working on ways to merge stem cell therapy and gene therapy, this could be extremely valuable to our field.

Scientists already knew that the membrane that surrounds the cell’s nucleus is ‘punctured’ with millions of tiny holes, known as nuclear pores. Co-lead author Bart Hoogenboom likened the pores to a strange kind of sieve:

“The pores have been to known to act like a sieve that could hold back sugar while letting grains of rice fall through at the same time, but it was not clear how they were able to do that.”

In this study—which used cells taken from frog eggs—Hoogenboom, along with co-lead author Ariberto Fassati, harnessed atomic force microscopy (AFM) to give them a new understanding of how these pores work. Like a blind person moving their fingers to read braille, AFM uses a tiny needle to pass over the nuclear pores in order to measure their shape and structure.

“AFM can reveal far smaller structures than optical microscopes,” said Hoogenboom, “but it’s feeling more than seeing. The trick is to press hard enough to feel the shape and the hardness of the sample, but not so hard that you break it. [In this study], we used it to successfully probe the membrane…to reveal the structure of the pores.”

And what they found, adds Fassati, offered an explanation for how these pores worked:

“We found that the proteins in the center of the pores tangle together just tightly enough to form a barrier—like a clump of spaghetti. Large molecules can only pass through [the pores] when accompanied by chaperone molecules. These chaperones, called nuclear transport receptors, have the property of lubricating the [spaghetti] strands and relaxing the barrier, letting the larger molecules through.”

Astoundingly, Fassati said that this process happens upwards of several thousand times per second.

These results are exciting not only for solving a long-standing mystery, but also for pointing to new ways of delivering gene therapies.

As evidenced by recent clinical advances in conditions such as sickle cell disease and SCID (‘bubble baby’ disease), gene therapy represents a promising way to treat—and even cure—patients. Hoogenboom and Fassati are optimistic that their team’s discovery could lead further refinements to gene therapy techniques.

Said Fassati, “It may be possible to improve the design of current mechanisms for delivering gene therapy to better cross the nuclear pores and deliver their therapeutic genes into the nucleus.”

Shape-Shifting Cells Drive Bone Healing; Point to New Method of Correcting Bone Deformities

There’s a time to grow and a time to heal—and the cells that make up our bone and cartilage have impeccable timing. During childhood and adolescence, these cells work to grow the bones longer and stronger. Once we’ve reached adulthood, they shift focus to repair and healing.

New research may help doctors treat craniofacial abnormalities while the patient is still growing—rather than having to wait until adulthood.

New research may help doctors treat craniofacial abnormalities while the patient is still growing—rather than having to wait until adulthood.

This is part of why children with bone deformities are often forced to wait until adulthood—until their bones stop growing—before their condition can be corrected.

Another part of the reason behind the agonizing wait is that scientists still don’t know exactly how this transition in bone cells, from a focus on growing to a focus on healing, even happens.

But new research out of the University of Michigan (UM) is well on its way to changing that.

In findings published today in Nature Cell Biology, Noriaki Ono (a UM assistant professor of dentistry) and his team announce the discovery of a subset of cartilage-making cells that take on new duties during the transition from adolescence into adulthood.

Previously, scientists had thought that these cartilage-making cells, known as chondrocytes, die once the bones stopped growing. But these new findings by Ono and his team showed that is not the case—not all chondrocytes bite the dust. Instead, they literally transform themselves from growing bone, to healing it.

The fact that some chondrocytes persist through to adulthood may mean that they can be selectively targeted to correct bone deformities in younger patients. As Ono explained in more detail:

“Up until now, the cells that drive this bone growth have not been understood very well. As an orthodontist myself, I have special interest in this aspect, especially for finding a cure for severe bone deformities in the faces of children. If we can find a way to make bones that continue to grow alongside the child, maybe we should be able to put these pieces of growing bones back into children and make their faces look much better than they do.”

10 Years/10 Therapies: 10 Years after its Founding CIRM will have 10 Therapies Approved for Clinical Trials

In 2004, when 59 percent of California voters approved the creation of CIRM, our state embarked on an unprecedented experiment: providing concentrated funding to a new, promising area of research. The goal: accelerate the process of getting therapies to patients, especially those with unmet medical needs.

Having 10 potential treatments expected to be approved for clinical trials by the end of this year is no small feat. Indeed, it is viewed by many in the industry as a clear acceleration of the normal pace of discovery. Here are our first 10 treatments to be approved for testing in patients.

HIV/AIDS. The company Calimmune is genetically modifying patients’ own blood-forming stem cells so that they can produce immune cells—the ones normally destroyed by the virus—that cannot be infected by the virus. It is hoped this will allow the patients to clear their systems of the virus, effectively curing the disease.

Spinal cord injury patient advocate Katie Sharify is optimistic about the latest clinical trial led by Asterias Biotherapeutics.

Spinal cord injury patient advocate Katie Sharify is optimistic about the clinical trial led by Asterias Biotherapeutics.

Spinal Cord Injury. The company Asterias Biotherapeutics uses cells derived from embryonic stem cells to heal the spinal cord at the site of injury. They mature the stem cells into cells called oligodendrocyte precursor cells that are injected at the site of injury where it is hoped they can repair the insulating layer, called myelin, that normally protects the nerves in the spinal cord.

Heart Disease. The company Capricor is using donor cells derived from heart stem cells to treat patients developing heart failure after a heart attack. In early studies the cells appear to reduce scar tissue, promote blood vessel growth and improve heart function.

Solid Tumors. A team at the University of California, Los Angeles, has developed a drug that seeks out and destroys cancer stem cells, which are considered by many to be the reason cancers resist treatment and recur. It is believed that eliminating the cancer stem cells may lead to long-term cures.

Leukemia. A team at the University of California, San Diego, is using a protein called an antibody to target cancer stem cells. The antibody senses and attaches to a protein on the surface of cancer stem cells. That disables the protein, which slows the growth of the leukemia and makes it more vulnerable to other anti-cancer drugs.

Sickle Cell Anemia. A team at the University of California, Los Angeles, is genetically modifying a patient’s own blood stem cells so they will produce a correct version of hemoglobin, the oxygen carrying protein that is mutated in these patients, which causes an abnormal sickle-like shape to the red blood cells. These misshapen cells lead to dangerous blood clots and debilitating pain The genetically modified stem cells will be given back to the patient to create a new sickle cell-free blood supply.

Solid Tumors. A team at Stanford University is using a molecule known as an antibody to target cancer stem cells. This antibody can recognize a protein the cancer stem cells carry on their cell surface. The cancer cells use that protein to evade the component of our immune system that routinely destroys tumors. By disabling this protein the team hopes to empower the body’s own immune system to attack and destroy the cancer stem cells.

Diabetes. The company Viacyte is growing cells in a permeable pouch that when implanted under the skin can sense blood sugar and produce the levels of insulin needed to eliminate the symptoms of diabetes. They start with embryonic stem cells, mature them part way to becoming pancreas tissues and insert them into the permeable pouch. When transplanted in the patient, the cells fully develop into the cells needed for proper metabolism of sugar and restore it to a healthy level.

HIV/AIDS. A team at The City of Hope is genetically modifying patients’ own blood-forming stem cells so that they can produce immune cells—the ones normally destroyed by the virus—that cannot be infected by the virus. It is hoped this will allow the patients to clear their systems of the virus, effectively curing the disease

Blindness. A team at the University of Southern California is using cells derived from embryonic stem cell and a scaffold to replace cells damaged in Age-related Macular Degeneration (AMD), the leading cause of blindness in the elderly. The therapy starts with embryonic stem cells that have been matured into a type of cell lost in AMD and places them on a single layer synthetic scaffold. This sheet of cells is inserted surgically into the back of the eye to replace the damaged cells that are needed to maintain healthy photoreceptors in the retina.

Entrepreneurship and Education

Guest author Neil Littman is CIRM’s Business Development Officer.

CIRM works closely with UCSF on a number of initiatives, from providing funding to academic investigators to jointly hosting events such as the recent CIRM Showcase with J-Labs held at the Mission Bay campus.

Beyond our joint initiatives, UCSF also provides many other valuable resources and educational opportunities to the life sciences community in the Bay Area. For instance, I was a mentor in UCSF’s “Idea to IPO” class which focused on helping students translate concepts into a commercializable product and viable business.

Another opportunity that may be of interest to all you budding entrepreneurs is UCSF’s Lean LaunchPad course, which kicks off in January (application deadline is Nov 19th). The course teaches…

“scientists and clinicians how to assess whether the idea or technology they have can serve as the basis of a business. The focus is on the marketplace where you must validate that your idea has value in order to move into the commercial world.”

See more at: Lean Launchpad for Life Sciences & Healthcare.

The course is being run out of the Entrepreneurship Center at UCSF, which is a division of the UCSF Office of Innovation, Technology & Alliances (ITA).

Creating a Genetic Model for Autism, with a Little Help from the Tooth Fairy

One of the most complex aspects of autism is that it is not one disease—but many. Known more accurately as the autism spectrum disorder, or ASD, experts have long been trying to tease apart the various ways in which the condition manifests in children, with limited success.

But now, using the latest stem cell technology, scientists at the University of California, San Diego (UCSD) have identified a gene associated with Rett Syndrome—a rare form of autism almost exclusively seen in girls. And in so doing, the team has made the startling discovery that the many types of autism may be linked by common molecular pathways.

The research team, led by UCSD Professor and CIRM grantee Alysson Muotri, explained in a news release how induced pluripotent stem cell, or iPS cell, technology was used to pinpoint a gene associated with Rett Syndrome:

“One can take advantage of genomics to map all mutant genes in the patient and then use their own iPS cells to measure the impact of mutations in relevant cell types. Moreover, the study of brain cells derived from these iPS cells can reveal potential therapeutic drugs tailored to the individual. It is the rise of personalized medicine for mental and neurological disorder.”

iPS cell technology—a process by which scientists transform adult skin cells back into embryonic-like stem cells, after which they can be coaxed into maturing into virtually any type of cell—is a promising way to model diseases at the cellular level. But in order to truly understand what is happening in the brains of people with autism, Muotri and his team needed more samples from autistic individuals—on the order of hundreds or even thousands.

The Tooth Fairy Project allows scientists to gather large quantities of cells from autistic individuals for genomic analysis—simply asking parents to send in a discarded baby tooth.

The Tooth Fairy Project allows scientists to gather large quantities of cells from autistic individuals for genomic analysis—simply by asking parents to send in a discarded baby tooth.

Luckily, Muotri had a little help from the Tooth Fairy.

Or, more accurately, the Tooth Fairy Project, in which parents register for a “Fairy Tooth Kit” that lets them send a discarded baby tooth of their autistic child to researchers. Housed within each baby tooth are cells that can be transformed—with iPS cell technology—into neurons, thus giving the researchers a massive sample size with which to study.

Interestingly, the findings presented here come from the very first tooth to be sent to Muotri. Specifically, the team identified a mutation in the gene TRPC6 was present in children with autism. Additional experiments in animal models revealed that the TRPC6 mutation was indeed associated with abnormal brain cell development and function.

And for their next trick, the team found a way to reverse the mutation’s damaging effects.

By treating the cells with the chemical hyperforin, they were able to restore some normal function to the neurons—offering up a potential therapeutic strategy for treating ASD patients who harbor the TRPC6 mutation.

Drilling down even further, the team found that mutations in another gene called MeCP2, which causes Rett Syndrome, also set off a genetic domino effect that alters the normal function of the TRPC6 gene. Thus connecting this syndrome with other, non-syndromic types of autism.

“Taken together, these findings suggest that TRPC6 is a novel predisposing gene for ASD that may act in a multiple-hit model,” said Muotri. “This is the first study to use iPS cell-derived human neurons to model non-syndromic ASD and illustrate the potential of modeling genetically complex sporadic diseases using such cells.”

Find out more about how stem cell research could help solve the mysteries behind autism in our Autism Fact Sheet.

CIRM Scientists Discover Key to Blood Cells’ Building Blocks

Our bodies generate new blood cells—both red and white blood cells—each and every day. But reproducing that feat in a petri dish has proven far more difficult.

Pictured: sections from zebrafish embryos. Blood vessels are labeled in red, the protein complex that regulates inflammation green and cell nuclei in blue. The arrowhead indicates a potential HSC. The image at bottom right combines all channels. [Credit: UC San Diego School of Medicine]

Pictured: sections from zebrafish embryos. Blood vessels are labeled in red, the protein complex that regulates inflammation green and cell nuclei in blue. The arrowhead indicates a potential HSC. The image at bottom right combines all channels.
[Credit: UC San Diego School of Medicine]

But now, scientists have identified the missing ingredient to producing hematopoietic stem cells, or HSC’s—the type of stem cell that gives rise to all blood and immune cells in the body. The results, published last week in the journal Cell, describe how a newly discovered protein plays a key role in generating HSC’s in the developing embryo—giving scientists a more complete recipe to reproduce these cells in the lab.

The research, which was led by University of California, San Diego (UCSD) professor David Traver and supported by a grant from CIRM, offers renewed hope for the possibility of generating patient-specific blood or immune cells using induced pluripotent stem cell (iPS cell) technology.

As Traver explained in last week’s news release:

“The development of some mature cell lineages from iPS cells, such as cardiac or neural, has been reasonably straightforward, but not with HSCs. This is likely due, at least in part, to not fully understanding all the factors used by the embryo to generate HSCs.”

Indeed, the ability to generate HSCs has long challenged scientists, as outlined in a CIRM workshop from last year. But now, says Traver, they have found a crucial piece to the puzzle.

Specifically, the researchers investigated a signaling protein called tumor necrosis factor alpha—or TNFα for short— a protein known to be important for regulating inflammation and immunity. Previous research by this study’s first author, Raquel Espin-Palazon, and others also discovered it was related to the healthy function of blood vessels during embryonic development.

In this study, Traver, Espin-Palazon and the UCSD drilled down even further—and found that TNFα was required for the normal development of HSCs in the embryo. This surprised the research team, as the young embryo is generally considered to be sterile—with no need for a protein normally charged with regulating immune response to be switched on. Explained Traver:

“There was no expectation that pro-inflammatory signaling would be active at this time or in the blood-forming regions.”

While preliminary, establishing this relationship between TNFα and HSC formation will be a boon to researchers looking for new ways to generate large quantities of healthy, patient-specific red and white blood cells for those patients who so desperately need them.

Learn more about how stem cell technology could help treat blood diseases in our Thalassemia Fact Sheet.

Bringing out the Big Guns: Scientists Weigh in on How Best to Combat Deadly Diseases of the Brain

Despite our best efforts, diseases of the brain are on the rise. Neurodegenerative conditions such as Alzheimer’s and Parkinson’s diseases threaten not only to devastate our aging population, but also cripple our economy. Meanwhile, the causes of conditions such as autism remain largely unknown. And brain and spinal cord injuries continue to increase—leaving their victims with precious few options for improving their condition.

This special review issue of addresses some of the key challenges for translational neuroscience and the path from bench to beside. [Credit: Cell Press]

This special review issue of Neuron addresses some of the key challenges for translational neuroscience and the path from bench to beside. [Credit: Cell Press]

We need to do better.

The scientific community agrees. And in a special issue of the journal Neuron, the field’s leading researchers lay out how to accelerate much-needed therapies to the many millions who will be affected by brain disease or injury in the coming years.

The journal’s leadership argues that now is the time to renew efforts in this field. Especially worrying, say experts, is the difficulty in translating research breakthroughs into therapies.

But Neuron Editor Katja Brose is optimistic that the answers are out there—we just need to bring them to light:

“There is resounding agreement that we need new approaches and strategies, and there are active efforts, discussion and experimentation aimed at making the process of therapeutic development more efficient and effective.”

Below are three papers highlighted in the special journal, each giving an honest assessment of how far we’ve come, and what we need to do to take the next step.

Fast-tracking Drug Development. In this perspective, authors from the Institute of Medicine (IOM) and the Salk Institute—including CIRM grantee Fred Gage—discuss the main takeaways from an IOM-sponsored workshop aimed at finding new avenues for accelerating treatments for brain diseases to the clinic.

The main conclusion, according to the review’s lead author Steve Hyman, is a crucial cultural shift—various stakeholders in academia, government and industry must stop thinking of themselves as competitors, but instead as allies. Only then will the field be able to successfully shepherd a breakthrough from the lab bench and to the patient’s bedside.

Downsized Divisions’ Dangerous Effects. Next, an international team of neuroscientists focuses their perspective on the recent trend of pharmaceutical companies to cut back on funding for neuroscience research. The reasoning: neurological diseases are far more difficult than other conditions, and proving to be too costly and too time-consuming to be worth continued effort.

The solution, says author Dennis Choi of State University of New York Stonybrook, is a fundamental policy change in the way that market returns of neurological disease drug development are regulated. But Choi argues that such a shift cannot be achieved without a concerted effort by patient advocates and nonprofits to lead the charge. As he explains:

“The broader neuroscience community and patient stakeholders should advocate for the crafting and implementation of these policy changes. Scientific and patient group activism has been successful in keeping the development of therapies in other areas—such as HIV and cancer—appropriately on track, but this type of sector-wide activism would be a novel step for the neuroscience community.”

Indeed, here at CIRM we have long helped support the patient community—a wonderful collection of individuals and organizations advocating for advances in stem cell research. We are humbled and honored that so many patients and patient advocates have stepped forward as stem cell champions as we move towards the clinic.

The Road to Preclinical Diagnosis. Finally, we hear from Harvard University neuroscientists highlighting how far the research has come—even in the face of such extraordinary difficulty.

Specifically focused on Alzheimer’s disease, the authors touch on the discoveries of protein markers, such as amyloid-beta and tau, that serve as an indicator of neurodegeneration. They make the important point that because Alzheimer’s is almost certainly is present before the onset of physical symptoms, the ultimate goal of researchers should be to find a way to diagnose the disease before it has progressed too far.

“[Here we] highlight the remarkable advances in our ability to detect evidence of Alzheimer’s disease in the brain, prior to clinical symptoms of the disease, and to predict those at greatest risk for cognitive decline,” explained lead author Reisa Sperling.

The common thread between these perspectives, say Neuron editors in an accompanying editorial, is that “by leveraging shared resources, tools and knowledge and approaching these difficult problems collaboratively, we can achieve more together.”

A sentiment that we at CIRM fully support—and one that we will continue to foster as we push forward with our mission to accelerate stem cell-based therapies to patients in need.

Stem Cell Stories that Caught our Eye: Skin Cells to Brain Cells in One Fell Swoop, #WeAreResearch Goes Viral, and Genes Helps Stem Cells Fight Disease

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Building a Better Brain Cell. Thanks to advances in stem cell biology, scientists have found ways to turn adult cells, such as skin cells, back into cells that closely resemble embryonic stem cells. They can then coax them into becoming virtually any cell in the body.

But scientists have more recently begun to devise ways to change cells from one type into another without first having to go back to a stem cell-like state. And now, a team from Washington University in St. Louis has done exactly that.

As reported this week in New Scientist, researcher Andrew Yoo and his team used microRNAs—a type of ‘signaling molecule’—to reprogram adult human skin cells into medium spiny neurons(MSNs), the type of brain cell involved in the deadly neurodegenerative condition, Huntington’s disease.

“Within four weeks the skin cells had changed into MSNs. When put into the brains of mice, the cells survived for at least six months and made connections with the native tissue,” explained New Scientist’s Clare Wilson.

This process, called ‘transdifferentiation,’ has the potential to serve as a faster, potentially safer alternative to creating stem cells.

#WeAreResearch Puts a Face on Science. The latest research breakthroughs often focus on the science itself, and deservedly so. But exactly who performed that research, the close-knit team who spent many hours at the lab bench and together worked to solve a key scientific problem, can sometimes get lost in the shuffle.

#WeAreResearch submission from The Thomson Lab at the University of California, San Francisco. This lab uses optogenetics, and RNAseq to probe cell fate decisions.

#WeAreResearch submission from The Thomson Lab at the University of California, San Francisco. This lab uses optogenetics, and RNAseq to probe cell fate decisions.

Enter #WeAreResearch, a new campaign led by the American Society for Cell Biology (ASCB) that seeks to show off science’s more ‘human side.’

Many California-based stem cell teams have participated—including CIRM grantee Larry Goldstein and his lab!

Check out the entire collection of submissions and, if you’re a member of a lab, submit your own. Prizes await the best submissions—so now’s your chance to get creative.

New Genes Help Stem Cells Fight Infection. Finally, UCLA scientists have discovered how stem cells ‘team up’ with a newly discovered set of genes in order to stave off infection.

Reporting in the latest issue of the journal Current Biology, and summarized in a UCLA news release, Julian Martinez-Agosto and his team describe how two genes—adorably named Yorkie and Scalloped—set in motion a series of events, a molecular Rube Goldberg device, that transforms stem cells into a type of immune system cell.

Importantly, the team found that without these genes, the wrong kind of cell gets made—meaning that these genes play a central role in the body’s healthy immune response.

Mapping out the complex signaling patterns that exist between genes and cells is crucial as researchers try and find ways to, in this case, improve the body’s immune response by manipulating them.

From Stem Cells to Stomachs: Scientists Generate 3D, Functioning Human Stomach Tissue

The human stomach can be a delicate organ. For example, even the healthiest stomach can be compromised by H. pylori bacteria—a tiny but ruthless pathogen which has shown to be linked to both peptic ulcer disease and stomach cancer.

The best way to study how an H. pylori infection leads to conditions like cancer would be to recreate that exact environment, right down to the stomach itself, in the lab. But that task has proven far more difficult than originally imagined.

Part of a miniature stomach grown in the lab, stained to reveal various cells found in normal human stomachs [Credit: Kyle McCracken]

Part of a miniature stomach grown in the lab, stained to reveal various cells found in normal human stomachs [Credit: Kyle McCracken]

But now, scientists at the Cincinnati Children’s Hospital Medical Center and the University of Cincinnati College of Medicine have successfully grown functional, human stomach tissue in a dish—the first time such a feat has been accomplished.

Further, they were then able to test how human stomach tissue reacts to an invasion by H. pylori—a huge leap forward toward one day developing treatments for potentially deadly stomach disease.

Reporting in today’s issue of the journal Nature, senior author Jim Wells describes his team’s method of turning human pluripotent stem cells into stomach cells, known as gastric cells. Wells explained the importance of their breakthrough in a news release:

“Until this study, no one had generated gastric cells from human pluripotent stem cells. In addition, we discovered how to promote formation of three-dimensional gastric tissue with complex architecture and cellular composition.”

The team called this stomach tissue gastric organoids, a kind of ‘mini-stomach’ that mimicked the major cellular processes of a normal, functioning human stomach. Developing a human model of stomach development—and stomach disease—has long been a goal among scientists and clinicians, as animal models of the stomach did not accurately reflect what would be happening in a human stomach.

In this study, the research team identified the precise series of steps that can turn stem cells into gastric cells. And then they set these steps in motion.

Over the course of a month, the team coaxed the formation of gastric organoids that measured less than 1/10th of one inch in diameter. But even with this small size, the team could view the cellular processes that drive stomach formation—and discover precisely what happens when that process goes awry.

But what most intrigued the researchers, which also included first author University of Cincinnati’s Kyle McCracken, was how quickly an H. pylori infection impacted the health of the stomach tissue.

“Within 24 hours, the bacteria had triggered biochemical changes in the organ,” said McCracken.

According to McCracken, as the H. pylori infection spread from cell to cell, the researchers also recorded the activation of c-Met, a gene known to be linked to stomach cancer—further elucidating the relationship between H. pylori and this form of stomach disease.

Somewhat surprisingly, little was known about how gastric cells play a role in obesity-related diseases, such as type 2 diabetes. But thanks to Wells, McCracken and the entire Cincinnati Children’s research team—we are that much closer to shedding light on this process.

Wells also credits his team’s reliance on years of preliminary data performed in research labs around the world with helping them reach this landmark:

“This milestone would not have been possible if it hadn’t been for previous studies from many other basic researchers on understanding embryonic organ development.”

Scientists Develop Stem Cell ‘Special Forces’ in order to Target, Destroy Brain Tumors

Curing someone of cancer is, in theory, a piece of cake: all you have to do is kill the cancer cells while leaving the healthy cells intact.

But in practice, this solution is far more difficult. In fact, it remains one of the great unsolved problems in modern oncology: how do you find, target and destroy each individual cancer cell in the body—while minimizing damage to the surrounding cells.

Encapsulated toxin-producing stem cells (in blue) help kill brain tumor cells in the tumor resection cavity (in green). [Credit: Khalid Shah, MS, PhD]

Encapsulated toxin-producing stem cells (in blue) help kill brain tumor cells in the tumor resection cavity (in green). [Credit: Khalid Shah, MS, PhD]

But luckily, Harvard Stem Cell Institute scientists at Massachusetts General Hospital may have finally struck gold: they have designed special, toxin-secreting stem cells that can target and destroy brain tumors. Their findings, which were performed in laboratory mice and which appear in the latest issue of the journal STEM CELLS, offer up an entirely unique method for eradicating deadly cancers.

Harvard Neuroscientist Khalid Shah, who led the study, explained in last Friday’s news release that the idea of engineering stem cells to kill cancer cells is not new—but there was a key difference in scientists’ ability to target individual cells vs. difficult-to-reach tumors, which is often the case with brain cancer:

“Cancer-killing toxins have been used with great success in a variety of blood cancers, but they don’t work as well in solid tumors because the cancers aren’t as accessible and the toxins have a short half-life.”

The solution, Shah and his team argued, was stem cells. Previously, Shah and his team discovered that stem cells could be used to circumvent these problems. The fact that stem cells continuously renew meant that they could also be used to continually deliver toxins to brain tumors.

“But first, we needed to genetically engineer stem cells that could resist being killed themselves by the toxins,” said Shah.

In this study, the research team introduced a small genetic change, or mutation, into the stem cells so that they become impervious to the toxin’s harmful effects. They then introduced a second mutation that allowed the stem cells to maintain and produce and secrete toxins throughout the cells’ lifetime—effectively giving it an unlimited supply of ammunition to use once it encountered the brain tumor.

They then employed a common technique whereby the toxins were tagged so that they only sought out and infected cancer cells—leaving healthy cells unscathed.

“We tested these stem cells in a clinically relevant mouse model of brain cancer,” Shah described. “After doing all of the molecular analysis and imaging to track the inhibition of protein synthesis within brain tumors, we do see the toxins kill the cancer cells and eventually prolonging the survival in animal models.”

While preliminary, these results are encouraging. As the team continues to refine their method of development and delivery, they are optimistic that they can bring their methods to clinical trial within the next five years.