Stem cell stories that caught our eye: screening for cancer drugs for kids, better CRISPR gene editing and funding for chimeras

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.

Stem cells screen drugs for kids’ rare tumor.  A team at Johns Hopkins University in Baltimore has transformed stem cells into a particularly nasty form of pediatric brain cancer, medulloblastoma. They then used those cells to figure out what drugs might defeat the tumor and found one existing drug, approved for advanced breast cancer, that seemed to be a good candidate.

While about two-thirds of medulloblastoma patients do well with standard therapy, those in a class called “group 3” often do not survive. But the rarity of that condition, meant the researcher could not use what has become a common route to determining effective drugs: comparing the genetic profile of the cancer with the genetic profile of banks of cancer cells that have already have been tested against existing cancer drugs. There are not enough Group 3 samples in the banks to take that route.

So, the Hopkins team used a two-step process for the drug search. They first inserted genes associated with the Group 3 cancers into stem cells and let the cells begin to transform into tumors. After making sure their stem cell tumors genetically looked and behaved like medulloblastoma the researchers compared genetic “signatures” from those cells with the signatures of cells in the large databases of other cancers.

eric raabe hopkins

Raabe

“We wanted to find whether the cells we created matched any of these existing signatures, because if they did, then we would have some idea of what kinds of drugs are more or most likely to kill these cells,” said Eric Raabe in a university release posted by ScienceDaily. “We didn’t have to do the laborious screening to test 100,000 compounds against our own cells.”

Raabe suggested this system might work to create a short cut to finding best therapies for other rare tumors as well.

 

Combining tricks from two critters.  This article does not address stem cells directly, but rather a widely popular gene editing technique many hope to use with stem cell therapies, the system known as CRISPR.  But before that can happen, researchers need to figure out how to eliminate or minimize pesky “off-target” gene editing, when the genetic scissor slices the DNA in a spot that was not intended.

CRISPR technology borrows from bacteria. About 40 percent of bacteria immune systems use CRISPR’s genetic elements to recognize foreign genes such as phages, the viruses that can kill or tag along in bacteria. Scientists generally pair CRISPR’s ability to recognize specific gene segments, with great specificity, with the nuclease, or genetic scissor, called CAS9. But that scissor is not quite as precise. So, a team at Kobe University in Japan borrowed an immune system trick from a second critter, a sea lamprey, sometimes incorrectly called an eel. The result was a much more precise gene editing tool.

Lamprey

The lamprey gene editing tool they borrowed is based on an enzyme called a deaminase. The lamprey uses the enzyme to create breaks in the genes for its immune system’s antibodies in order to have a more diverse immune system able to recognize more outside pathogens. That deaminase tool turns out to go a long way toward making CRISPR precise enough to be considered for use in a therapy.

The Japanese work published in the journal Science, marks the second time researchers have recently published a way to use a deaminase tool to improve CRISPR. The prior work came from the lab of Harvard’s George Church, who is quoted extensively in an article about the latest study in The Scientist. Be warned, Church likes detail and this is a pretty technical article unless you are a science nerd like us at The Stem Cellar.

 

Animals with bits of human get green light.  A flurry of stories came out a few months ago when a reporter realized that while the National Institutes of Health (NIH) had a moratorium on creating chimeras—animal embryos that are partly human—CIRM was still funding the work. Now, NIH has announced plans to lift that moratorium with several safeguards in place to make sure certain projects that raise ethical issues don’t get approved. We are glad to have company in funding this potentially life-saving research.

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Researchers working in the area have two main goals. They want to create better models of human disease, and they want to grow human organs in animals such as pigs to alleviate the current shortage of donor organs and help the thousands of patients who die each year waiting for a donor.

NPR aired a story that did a good job describing the safeguards and the types of projects that would not be allowed. It quoted Carrie Wolinetz, the NIH associate director for science policy:

 “At the end of the day, we want to make sure this research progresses because it’s very important to our understanding of disease. It’s important to our mission to improve human health. But we also want to make sure there’s an extra set of eyes on these projects because they do have this ethical set of concerns associated with them.”

Forbes posted a story online that took great liberty with comparisons to science fiction, but had fun with it and in the end valued the potential for the work. And the public does have a chance to weigh in on the ethical issues as NIH has published a call for comments in the Federal Register.

T cell fate and future immunotherapies rely on a tag team of genetic switches

Imagine if scientists could build microscopic smart missiles that specifically seek out and destroy deadly, hard-to-treat cancer cells in a patient’s body? Well, you don’t have to imagine it actually. With techniques such as chimeric antigen receptor (CAR) T therapy, a patient’s own T cells – immune system cells that fight off viruses and cancer cells – can be genetically modified to produce customized cell surface proteins to recognize and kill the specific cancer cells eluding the patient’s natural defenses. It is one of the most exciting and promising techniques currently in development for the treatment of cancer.

Human T Cell (Wikipedia)

Human T Cell (Wikipedia)

Although there have been several clinical trial success stories, it’s still early days for engineered T cell immunotherapies and much more work is needed to fine tune the approach as well as overcome potential dangerous side effects. Taking a step back and gaining a deeper understanding of how stem cells specialize into T cells in the first place could go a long way into increasing the efficiency and precision of this therapeutic strategy.

Enter the CIRM-funded work of Hao Yuan Kueh and others in Ellen Rothenberg’s lab at CalTech. Reporting yesterday in Nature Immunology, the Rothenberg team uncovered a time dependent array of genetic switches – some with an ON/OFF function, others with “volume” control – that together control the commitment of stem cells to become T cells.

Previous studies have shown that the protein encoded by the Bcl11b gene is the key master switch that when activated sets a “no going back” path toward a T cell fate. A group of other genes, including Runx1, TCF-1 and GATA-3 are known to play a role in activating Bcl11b. The dominant school of thought is that these proteins gradually accumulate at the Bcl11b gene and once a threshold level is achieved, the proteins combine to enable the Bcl11b activation switch to flip on. However, other studies suggest that some of these proteins may act as “pioneer” factors that loosen up the DNA structure and allow the other proteins to readily access and turn on the Bcl11b gene. Figuring out which mechanism is at play is critical to precisely manipulating T cell development through genetic engineering.

To tease out the answer, the CalTech team engineered mice such that cells with activated Bcl11b would glow which allows visualizing the fate of single cells. We reached out to Dr. Kueh on the rationale for this experimental approach:

Hao Yuan Kueh, CalTech

Hao Yuan Kueh, CalTech

“To fully understand how genes are controlled, we need to watch them turn on and off in single, living cells over time.  As cells in our body are unique and different from one another, standard measurement methods, which average over millions of cells, often do not tell us the entire picture.”

The team examined the impact of inhibiting the T cell specific proteins GATA-3 and TCF-1 at different stages in T cell development in single cells. When the production of these two proteins were blocked in very early T cell progenitor (ETPs) cells, activation of Bcl11b was dramatically reduced. But that’s not what they observed when the experiment was repeated in a later stage of T cell development. In this case, blocking GATA-3 and TCF-1 had a much weaker impact on Bcl11b. So GATA-3 and TCF-1 are important for turning on Bcl11b early in T cell development but are not necessary for maintaining Bcl11b activation at later stages.

Inhibition of Runx1, on the other hand, did lead to a reduction in Bcl11b in these later T cell development stages. Making Runx1 levels artificially high conversely led to elevated Bcl11b in these cells.

Together, these results point to GATA-3 and TCF-1 as the key factors for turning on Bcl11b to commit cells to a T cell fate and then they hand off their duties to Runx1 to keep Bcl11b on and maintaining the T cell identity. Dr. Kuhn sums up the results and their implications this way:

“Our work shows that control of gene expression is very much a team effort, where some proteins flip the gene’s master ON-OFF switch, and others set its expression levels after it turns on…These results will help us generate customized T-cells to fight cancer and other diseases.  As T-cells are specialized to recognize and fight foreign agents in our body, this therapy strategy holds much promise for diseases that are difficult to treat with standard drug-based methods.  Also, these intricate gene regulation mechanisms are likely to be in play in other cell types in our body, not just T-cells, and so we believe our results will be widely relevant.”

Circular RNAs: the Mind-Boggling Dark Matter of the Human Genome

We were just a few hours into the 2016 annual meeting of the International Society for Stem Cell Research (ISSCR) yesterday afternoon and my mind was already blown away. Pier Paolo Pandolfi of the Beth Israel Deaconess Medical Center at Harvard, spoke during the first plenary session about circular RNAs, which he dubbed, “the mind-boggling dark matter of the human genome” because their existence wasn’t confirmed until just four years ago.

To introduce the topic, Pandolfi compared human DNA to that of bacteria. Both species contain stretches of DNA sequence called genes that contain the instructions for making proteins which collectively form our bodies. Each gene is first transcribed into messenger RNA (mRNA) which in turn is translated into a protein.

Iceberg

Our DNA contains 20,000 genes. But that genetic material is just the tip of the iceberg.

But with the ability to sequence all the mRNA transcripts of an organism, or its transcriptome, came a startling fact about how differently our genetic structure is organized compared to bacteria. It turns out that 88% of DNA sequence in bacteria make up genes that code for proteins but only 2% of human DNA sequence directly codes for proteins. So what’s going with the other 98%? Scientist typically call this 98% chunk of the genome “regulatory DNA” because it contains sequences that act as control switches for turning genes on or off. But Pandolfi explained that more recent studies suggest that a whopping 70% of our genome (maybe even 95%) is transcribed into RNA but those RNA molecules just don’t get translated into protein.

 

One type of this “non-coding” RNA which we’ve blogged about plenty of times is called microRNA (miRNA). So far, about 5,000 human miRNAs have been identified compared to the 20,000 messenger RNAs that code for proteins. But by far the most abundant non-coding RNA in our transcriptome is the mysterious circular RNA (circRNA) with at least 100,000 different transcripts. circRNA was first observed as cellular structures in the 1980’s via electronic microscope images. Then in the 1990’s a scientist published DNA sequencing data suggesting the existence of circRNA. But the science community at that time panned the results, discrediting it as merely background noise of the experiments.

Pandolfi_2

Pier Paolo Pandolfi
Image: Beth Israel Deaconess Medical Center

But four years ago, the circRNAs were directly sequenced and their existence confirmed. The circRNAs are formed when messenger RNA goes through a well-described trimming process of its sequence. Some of the excised pieces of RNA form into the circular RNAs. It would seem that these circRNAs are just throw away debris but Pandolfi’s lab has found evidence that they directly play a role in cellular functions and even cancer.

His team studies a gene called Pokemon which, when genetically “knocked out” or removed from a mouse’s genome, leads to cancer. Now, it turns out this knockout not only removes the Pokemon protein but also a Pokemon circRNA (circPok). When the lab added back just the Pokemon gene, as you might expect, it acted to suppress cancer in the mice. But when just the circPok was added back, stunningly, it increased the formation of cancer in the mice. Given that genetic knockouts are one of the most pervasive techniques in biomedical science, a closer look at circRNAs that may have been overlooked in all of those results is clearly warranted.

Though this finding is somewhat scary in the fact that it’s a whole aspect of our genome that we’ve been unaware of, one fortunate aspect of circRNA is that they all carry a particular sequence which could be used as a target for a new class of drugs.

This data may extend to stem cells as well. We know that microRNAs have critical roles in regulating the maturation of stem cells into specialized cell types. Since circRNAs are thought to act by competing microRNA, it may not be long before we learn about circRNA’s role in stem cell function.

The other speakers at the first plenary session of the ISSCR annual meeting all gave high caliber talks. Luckily, Paul Knoepfler live blogged on two of those presentations. Here are the links:

 

Multi-Talented Stem Cells: The Many Ways to Use Them in the Clinic

CIRM kicked off the 2016 International Society for Stem Cell Research (ISSCR) Conference in San Francisco with a public stem cell event yesterday that brought scientists, patients, patient advocates and members of the general public together to discuss the many ways stem cells are being used in the clinic to develop treatments for patients with unmet medical needs.

Bruce Conklin, Gladstone Institutes & UCSF

Bruce Conklin, Gladstone Institutes & UCSF

Bruce Conklin, an Investigator at the Gladstone Institutes and UCSF Professor, moderated the panel of four scientists and three patient advocates. He immediately captured the audience’s attention by showing a stunning video of human heart cells, beating in synchrony in a petri dish. Conklin explained that scientists now have the skills and technology to generate human stem cell models of cardiomyopathy (heart disease) and many other diseases in a dish.

Conklin went on to highlight four main ways that stem cells are contributing to human therapy. First is using stem cells to model diseases whose causes are still largely unknown (like with Parkinson’s disease). Second, genome editing of stem cells is a new technology that has the potential to offer cures to patients with genetic disorders like sickle cell anemia. Third, stem cells are known to secrete healing factors, and transplanting them into humans could be beneficial. Lastly, stem cells can be engineered to attack cancer cells and overcome cancer’s normal way of evading the immune system.

Before introducing the other panelists, Conklin made the final point that stem cell models are powerful because scientists can use them to screen and develop new drugs for diseases that have no treatments or cures. His lab is already working on identifying new drugs for heart disease using human induced pluripotent stem cells derived from patients with cardiomyopathy.

Scientists and Patient Advocates Speak Out

Malin Parmar, Lund University

Malin Parmar, Lund University

The first scientist to speak was Malin Parmar, a Professor at Lund University. She discussed the history of stem cell development for clinical trials in Parkinson’s disease (PD). Her team is launching the first in-human trial for Parkinson’s using cells derived from human pluripotent stem cells in 2016. After Parmar’s talk, John Lipp, a PD patient advocate. He explained that while he might look normal standing in front of the crowd, his PD symptoms vary wildly throughout the day and make it hard for him to live a normal life. He believes in the work that scientists like Parmar are doing and confidently said, “In my lifetime, we will find a stem cell cure for Parkinson’s disease.”

Adrienne Shapiro, Patient Advocate

Adrienne Shapiro, Patient Advocate

The next scientist to speak was UCLA Professor Donald Kohn. He discussed his lab’s latest efforts to develop stem cell treatments for different blood disorder diseases. His team is using gene therapy to modify blood stem cells in bone marrow to treat and cure babies with SCID, also known as “bubble-boy disease”. Kohn also mentioned their work in sickle cell disease (SCD) and in chronic granulomatous disease, both of which are now in CIRM-funded clinical trials. He was followed by Adrienne Shapiro, a patient advocate and mother of a child with SCD. Adrienne gave a passionate and moving speech about her family history of SCD and her battle to help find a cure for her daughter. She said “nobody plans to be a patient advocate. It is a calling born of necessity and pain. I just wanted my daughter to outlive me.”

Henry Klassen (UC Irvine)

Henry Klassen, UC Irvine

Henry Klassen, a professor at UC Irvine, next spoke about blinding eye diseases, specifically retinitis pigmentosa (RP). This disease damages the photo receptors in the back of the eye and eventually causes blindness. There is no cure for RP, but Klassen and his team are testing the safety of transplanting human retinal progenitor cells in to the eyes of RP patients in a CIRM-funded Phase 1/2 clinical trial.

Kristen MacDonald, RP patient

Kristen MacDonald, RP patient

RP patient, Kristen MacDonald, was the trial’s first patient to be treated. She bravely spoke about her experience with losing her vision. She didn’t realize she was going blind until she had a series of accidents that left her with two broken arms. She had to reinvent herself both physically and emotionally, but now has hope that she might see again after participating in this clinical trial. She said that after the transplant she can now finally see light in her bad eye and her hope is that in her lifetime she can say, “One day, people used to go blind.”

Lastly, Catriona Jamieson, a professor and Alpha Stem Cell Clinic director at UCSD, discussed how she is trying to develop new treatments for blood cancers by eradicating cancer stem cells. Her team is conducting a Phase 1 CIRM-funded clinical trial that’s testing the safety of an antibody drug called Cirmtuzumab in patients with chronic lymphocytic leukemia (CLL).

Scientists and Patients need to work together

Don Kohn, Catriona Jamieson, Malin Parmar

Don Kohn, Catriona Jamieson, Malin Parmar

At the end of the night, the scientists and patient advocates took the stage to answer questions from the audience. A patient advocate in the audience asked, “How can we help scientists develop treatments for patients more quickly?”

The scientists responded that stem cell research needs more funding and that agencies like CIRM are making this possible. However, we need to keep the momentum going and to do that both the physicians, scientists and patient advocates need to work together to advocate for more support. The patient advocates in the panel couldn’t have agreed more and voiced their enthusiasm for working together with scientists and clinicians to make their hopes for cures a reality.

The CIRM public event was a huge success and brought in more than 150 people, many of whom stayed after the event to ask the panelists more questions. It was a great kick off for the ISSCR conference, which starts today. For coverage, you can follow the Stem Cellar Blog for updates on interesting stem cell stories that catch our eye.

CIRM Public Stem Cell Event

CIRM Public Stem Cell Event

Stem cell stories that caught our eye: a surprising benefit of fasting, faster way to make iPSCs, unlocking the secret of leukemia cancer cells

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.

Fasting

Is fasting the fountain of youth?

Among the many insults our bodies endure in old age is a weakened immune system which leaves the elderly more susceptible to infection. Chemotherapy patients also face the same predicament due to the immune suppressing effects of their toxic anticancer treatments. While many researchers aim to develop drugs or cell therapies to protect the immune system, a University of Southern California research report this week suggests an effective alternative intervention that’s startlingly straightforward: fasting for 72 hours.

The study published in Cell Stem Cell showed that cycles of prolonged fasting in older mice led to a decrease in white blood cells which in turn set off a regenerative burst of blood stem cells. This restart of the blood stem cells replenished the immune system with new white blood cells. In a pilot Phase 1 clinical trial, cancer patients who fasted 72 hours before receiving chemotherapy maintained normal levels of white blood cells.

A look at the molecular level of the process pointed to a decrease in the levels of a protein called PKA in stem cells during the fasting period. In a university press release carried by Science Daily, the study leader, Valter Longo, explained the significance of this finding:

“PKA is the key gene that needs to shut down in order for these stem cells to switch into regenerative mode. It gives the ‘okay’ for stem cells to go ahead and begin proliferating and rebuild the entire system. And the good news is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system.”

In additional to necessary follow up studies, the team is looking into whether fasting could benefit other organ systems besides the immune system. If the data holds up, it could be that regular fasting or direct targeting of PKA could put us on the road to a much more graceful and healthier aging process.

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Faster, cheaper, safer way to use iPS cells

Science, like traffic in any major city, never moves quite as quickly as you would like, but now Japanese researchers are teaming up to develop a faster, and cheaper way of using iPSC’s , pluripotent stem cells that are reprogrammed from adult cells, for transplants.

Part of the beauty of iPSCs is that because those cells came from the patient themselves, there is less risk of rejection. But there are problems with this method. Taking adult cells and turning them into enough cells to treat someone can take a long time. It’s expensive too.

But now researchers at Kyoto University and three other institutions in Japan have announced they are teaming up to change that. They want to create a stockpile of iPSCs that are resistant to immunological rejection, and are ready to be shipped out to researchers.

Having a stockpile of ready-to-use iPSCs on hand means researchers won’t have to wait months to develop their own, so they can speed up their work.

Shinya Yamanaka, who developed the technique to create iPSCs and won the Nobel prize for his efforts, say there’s another advantage with this collaboration. In a news article on Nikkei’s Asian Review he said these cells will have been screened to make sure they don’t carry any potentially cancer-causing mutations.

“We will take all possible measures to look into the safety in each case, and we’ll give the green light once we’ve determined they are sound scientifically. If there is any concern at all, we will put a stop to it.”

CIRM is already working towards a similar goal with our iPSC Initiative.

Unlocking the secrets of leukemia stem cells

the-walking-dead-season-6-zombies

Zombies: courtesy “The Walking Dead”

Any article that has an opening sentence that says “Cancer stem cells are like zombies” has to be worth reading. And a report in ScienceMag  that explains how pre-leukemia white blood cell precursors become leukemia cancer stem cells is definitely worth reading.

The article is about a study in the journal Cell Stem Cell by researchers at UC San Diego. The senior author is Catriona Jamieson:

“In this study, we showed that cancer stem cells co-opt an RNA editing system to clone themselves. What’s more, we found a method to dial it down.”

An enzyme called ADAR1 is known to spur cancer growth by manipulating small pieces of genetic material known as microRNA. Jamieson and her team wanted to track how that was done. They discovered it is a cascade of events, and that once the first step is taken a series of others quickly followed on.

They found that when white blood cells have a genetic mutation that is linked to leukemia, they are prone to inflammation. That inflammation then activates ADAR1, which in turn slows down a segment of microRNA called let-7 resulting in increased cell growth. The end result is that the white blood cells that began this cascade become leukemia stem cells and spread an aggressive and frequently treatment-resistant form of the blood cancer.

Having uncovered how ADAR1 works Jamieson and her team then tried to find a way to stop it. They discovered that by blocking the white blood cells susceptibility to inflammation, they could prevent the cascade from even starting. They also found that by using a compound called 8-Aza they could impede ADAR1’s ability to stimulate cell growth by around 40 percent.

Jamieson

Catriona Jamieson – definitely not a zombie

Jamieson says the findings open up all sorts of possibilities:

“Based on this research, we believe that detecting ADAR1 activity will be important for predicting cancer progression. In addition, inhibiting this enzyme represents a unique therapeutic vulnerability in cancer stem cells with active inflammatory signaling that may respond to pharmacologic inhibitors of inflammation sensitivity or selective ADAR1 inhibitors that are currently being developed.”

This wasn’t a CIRM-funded study but we have supported other projects by Dr. Jamieson that have led to clinical trials.

 

 

 

 

Shedding Light on a Path to Halting Deadly Pancreatic Cancers

Pancreatic cancer has a dismal prognosis: only a quarter of those diagnosed survive past one year and only about six percent live beyond five years. Its strong resistance to chemotherapy makes pancreatic cancer one of the most aggressive, deadly cancers and leaves doctors with few treatment options. New ways to study pancreatic cancer are desperately needed to find novel therapies.

Today, UCSD researchers, funded in part by CIRM, report in Nature on the development of a live imaging technique that enables precise tracking of drug resistant cancer stem cells within a pancreatic tumor. Using this method, they establish that the function of a gene called Musashi (Msi) is crucial for tumor growth, making it a promising target for chemotherapy drug development.

pancreatic_cancer_imaging

Activity of stem cell gene Musashi in human pancreatic cancer. Cancer cells are shown in green, Musashi expression in red and blue includes cells within the cancer microenvironment. Image courtesy of Dawn Jaquish, UC San Diego.

The Msi protein normally plays a role in the maintenance of stem cells but it’s also known to help sustain the growth of blood cancers. The UCSD team chose to investigate the role of Msi in pancreatic cancer as they found Msi was present in every human tumor sample they tested. To track Msi in a living animal, they genetically engineered mice that would emit fluorescence in cells where the Msi gene was activated.

Cells expressing the stem cell gene Musashi (green) are shown among other tumor cells (blue) and blood vessels (pink). Musashi-expressing cells preferentially drive tumor growth, drug resistance and lethality. UCSD

Those Msi mice were then bred with another strain of mice that mimic the pancreatic cancer seen in humans. In the resulting mice, cells with a strong fluorescent signal (indicating a high level of Msi) were found as a rare, distinct population in pancreatic cancer cells. It turns out that cancer stem cells, the cells thought to be responsible for cancerous growth and treatment relapse, are also known to make up a tiny portion of a tumor. So then, do Msi-positive cancer cells have cancer stem cell-like behavior? The answer appears to be “yes”. When the team transplanted the cancer cells with high levels of Msi from one mouse into the pancreas of healthy mice, every mouse tested died from very aggressive tumor growth. On the other hand, mice transplanted with cancer cells lacking the Msi fluorescent signal showed no evidence of disease.

These very promising results, along with the new imaging toolset, not only bode well for future treatments of pancreatic cancer but also for the cancer field as a whole. In a university press release, principal investigator Tannishtha Reya detailed this point:

pancreaticTannishtha Reya

Tannishtha Reya

“Because Msi reporter [fluorescence] activity can be visualized by live imaging, these models can be used to track cancer stem cells within the tumor microenvironment, providing a real-time view of cancer growth and metastasis, and serving as a platform to test new drugs that may be better able to eradicate resistant cells.”

Let’s hope that this research path leads to the day that a pancreatic cancer diagnosis isn’t an almost certain death sentence.

Outsmarting cancer’s deadly tricks

Cancer cells are devious monsters that kill people by sabotaging normal cell functions toward a path of uncontrolled cell growth. Without an effective treatment, aggressive cancers can crowd out healthy tissue and ultimately cause organ failure and death. This devastation by design makes it seem as though a cancer cell has a mind of its own but in reality it’s all due to mindless mutations in DNA. Gaining a deep understanding of those mutations provides scientists with insights into the molecular mechanisms of cancer which can help pinpoint targets for potential cancer treatments.

A team at The Scripps Research Institute (TSRI) followed the trail of such a mutation in a gene called POT1. Today in Cell Reports the researchers, funded in part by CIRM, describe their identification of a novel mechanism for cancer progression in cells carrying the POT1 mutation and they also speculate on the development on a unique therapeutic strategy.

Chromosomes go to pot without POT1
The POT1 protein is one component of shelterin, a multi-protein structure that binds to and protects telomeres, a region of DNA found at the ends of chromosomes. The team found that when POT1’s function is disrupted by mutation, the telomeres become vulnerable to damage which leads to chromosome instability. As a result, many regions of DNA on the chromosomes get rearranged leading to further gene mutations that in turn can accelerate the process of cancerous growth.

Telomere_caps

Human chromosomes (grey) capped by telomeres (white) Wikipedia

However, in the case of POT1 mutations, the DNA damage in the unstable chromosomes stimulates an enzyme called ATR that’s known to shut down cell division and initiate apoptosis, or programmed cell death. Now, unless I’m missing something, cells that have either stopped dividing or even died would seem to be the opposite of cancer progression. So why then are POT1 mutations found in a number of cancers such as leukemia, melanoma (skin cancer) and glioma (brain cancer)? As TSRI Associate Professor Eros Lazzerini Denchi, a co-leader on the publication, mentions in a press release, this conundrum presented an opportunity to better understand POT1 related cancers:

lazzerini_denchi

Eros Lazzerini Denchi

“Somehow those cells found a way to survive—and thrive. We thought that if we could understand how that happens, maybe we could find a way to kill those cells.”

 

Mutant POT1 and p53: diabolical partners in cancer progression
The team looked for answers by studying the POT1 mutation in the presence of a mutated form of the p53 tumor suppressor gene, found in over 50% of all human cancers. Mice bred with the POT1 mutation alone formed no cancers while those animals with the p53 mutation alone developed T cell lymphomas, a type of immune system cancer, by 20 weeks and survived 24 weeks. Mice with both mutations fared much worse with median survival times of just 17 weeks. So somehow the p53 mutation was bringing out the potential of the POT1 mutation to cause aggressive cancer growth.

Further experiments revealed that the p53 mutation quashed the ATR enyzme’s programmed cell death signal which the team had shown was stimulated by the POT1 mutation. As a result, the cells avoided programmed cell death. Because the cells had no mechanism to die, more cancer-causing mutations had the opportunity to develop from the chromosome instability caused by the POT1 mutation.

The bright side to this diabolical cooperation between mutant POT1 and p53 is that it presents a possible opening for new treatment strategies. It turns out that no cell, not even a cancerous one, can survive in the complete absence of ATF. Since cells with the POT1 mutations already have a reduced level of ATF, the authors suggest that delivery of low doses of ATF inhibitors, which have already been developed for the clinic, could kill cancer cells without affecting healthy cells. No doubt the team is eager to follow up on this hypothesis.

It’s comforting to know that there are crafty scientists out there who are closing in on ways to outsmart the sneaky tactics of cancer cells. And it wouldn’t be possible without this fundamental research, as Lazzerini Denchi points out:

“This study shows that by looking at basic biological questions, we can potentially find new ways to treat cancer.”

 

Stem cell stories that caught our eye: two-week old embryos in the lab, gene edited disease model, recipe for bone and cancer milestone

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.

Two-week embryos grabbed headlines. I have rarely seen as many online news outlets pick up a basic science story as happened this week with the news that an international team had nearly doubled the time it is possible to keep an embryo alive in a lab dish. While the research has tremendous potential to improve the chances couples can bring a new life into their families, the bulk of the coverage focused on the ethical issues surrounding the research embryo itself.

 

Imaris Snapshot

Molecular markers highlight various parts of a 12-day old embryo

After countless national and international confabs in the late 1970s and into the 1980s, research organizations around the world adopted the policy that no one would grow an embryo in the lab beyond 14 days. That is the point the “primitive streak” develops marking the first time cells within the embryo adopt individual identities. But the rule required no enforcement because no one knew how to coax an embryo into growing beyond nine days, and few could get them even to grow seven.

That changed this week, when the team led by Ali Brivanlou at Rockefeller University got embryos to grow to 13 days. They followed a procedure developed by a team colleague in Cambridge, UK, in mice reported earlier. They basically made the embryos feel more at home. They tested many different chemicals to add to the lab dish to optimize growth and gave the embryos a rigid structure more like a uterine wall.

They successfully mimicked implantation, the key step when the few-day-old embryo attaches to the uterus. Failure in this critical step is a key cause of infertility, but we have never been able to find out how it happens, and what little we do know suggests the mouse model for that step is not a good one for looking at human fertility.

 “This portion of human development was a complete black box,” said Brivanlou in a university press release picked up by many outlets including Bioscience Technology. She later added: “With this work, we can really appreciate the differences between human and mouse, and across all mammals. Because of the variations between species, what we learn in model systems is not necessarily relevant to our own development, and these results provide crucial information we couldn’t learn elsewhere.”

Because of that incredible potential value in this work, the journal Nature that published the research paper also ran a commentary about the current 14-day limit on growing embryos in the lab. It does not call for changing the policy at this time, but it does suggest the conversation–likely to be long–about whether the benefits of this work outweigh the ethical trip wires should begin soon.

The Washington Post wrote one of the most balanced pieces discussing both sides of the issue.

 

A mightier disease-in-a-dish model.  We frequently write about using iPS type stem cells to model diseases. Usually this involves getting a skin sample from a patient with a genetically-linked disease, converting it to stem cells and then growing the nerve or other tissue impacted by the disease. But you can also mimic the disease by genetically modifying normal stem cells to have specific mutations. This allows you to start to sorting out the role of individual genes in diseases linked to multiple genes.

 

Neurons from stem cells_TessierLavigne_neurons

Nerves grown from stem cells

One problem with the latter had been that gene editing techniques, particularly the wildly popular CRISPR-Cas9 method, usually edit both strands of DNA, but many disease mutations can do their damage with only a single incorrect gene, so-called heterozygous mutations. Now, another Rockefeller University team, this one led by the University’s president Marc Tessier-Lavigne, developed a way to make the CRISPR edit much more specific and only impact one strand of DNA.

HealthCanal picked up the university’s press release about the work published in Nature. The specific gene editing in this reports involved mutations linked to Alzheimer’s disease.

 

bone-scaffold Hopkins

Printed jaw

A better recipe for bone. Researchers trying to grow new tissue are finding the make-up of the scaffold you use can be more important than the stem cells you put on the structure. A Johns Hopkins team recently reported an improved recipe for making a scaffold for growing bone. Their formula: 30 percent pulverized natural bone and the remainder a special plastic with the mixture extruded using a 3D printer.

 “Bone powder contains structural proteins native to the body plus pro-bone growth factors that help immature stem cells mature into bone cells,” said Hopkins’ Warren Grayson. “It also adds roughness to the PCL (plastic), which helps the cells grip and reinforces the message of the growth factors.”

MDTmag posted the university press release about the research published in ACS Biomaterials Science & Engineering.

 

Licensing moved cancer therapy forward.  We at CIRM are always thrilled when one of our projects hurdles a milestone toward becoming a widely available therapy. One such critical move was announced last month and picked up this week by HealthCanal.

 Oncternal Therapeutics licensed the antibody drug named for our agency, Cirmtuzumab, for further testing of its ability to fight leukemia, and potentially other cancers. The antibody selectively targets a protein on cancer stem cells, ROR1, which has the unwieldy full name “receptor-tyrosine kinase-like orphan receptor 1.” The license also includes rights to other drugs that might be developed targeting ROR1.

University of California, San Diego, which developed Cirmtuzumab, has begun a clinical trial but has not got to a point where it can report results. We covered it in more detail in our series CIRM Fights Cancer.

Achilles’ Heel of Brain Cancer Identified in Tumor Stem Cells

Few words strike me with more dread than glioblastoma, the name for a very aggressive, incurable cancer of the brain. Although surgery and chemotherapy can help hold off or reverse a glioblastoma’s growth for a while, almost inevitably the tumor comes back along with a terrible prognosis: an average survival time of 12 to 15 months after diagnosis with a less than 5% survival rate beyond five years.

Screen Shot 2016-04-27 at 10.02.02 AM

MRI scans of glioblastoma in the brain of a 15 year-old boy.
Image: Wikipedia

Brain tumor stem cells (BTSCs) are thought to be the culprits behind the cancer’s reoccurrence because of their stem cell-like ability for limitless self-renewal. So the idea is that even a tiny number of BTSCs left behind after treatment will likely to lead to a tumor regrowth and treatment relapse. If researchers can better understand what makes the BTSCs tick, they could find ways to eliminate them and cure this dreadful disease.

glioblastoma

Brain tumor stem cells (BTSCs).
Image: Takrima Haque / Arezu Jahani-Asl Laboratory

This week researchers largely from The Ottawa Hospital Research Institute report on the identification of a key piece of BTSCs’ molecular machinery that provides a promising target for novel glioblastoma treatments. The study, published in Nature Neuroscience, focuses on the epidermal growth factor (EGF) cell signaling pathway. In normal cells, the EGF protein binds to the EGF receptor (EGFR) on a cell’s surface which triggers a cascade of protein interactions inside the cell that stimulate cell growth among other things.

EGFRvIII: a cancer stem cell gas pedal stuck to the floorboard
Eventually a given EGF signaling event subsides. But many BTSCs found in glioblastoma tissue samples have a mutant form of EGFR, called EGFRvIII, that permanently switches this signaling pathway into the “on position” even in the absence of EGF. It’s like the gas pedal of a car that gets stuck to the floorboard, causing the car to dangerously accelerate even though no one is pressing on the accelerator.

Previous studies had shown this always-on EGFRvIII growth signal causes abnormally high activation of a messenger protein, STAT3, which in turn hyper stimulates a network of genes that leads to cancerous growth of the tumor stem cells. But it wasn’t clear exactly how this protein carries out the uncontrolled cell division. Through a detailed genetic analysis of BTSCs from several glioblastoma patient samples, the team zeroed in on the oncostatin M receptor (OSMR) as a critical player. This analysis revealed that STAT3 was a natural activator of the OSMR gene and that high levels of both proteins in patient samples correlated to a poorer prognosis.

No OSMR = no tumors
To investigate further, human BTSCs genetically engineered to lack OSMR were injected under the skin of mice and showed an 80% reduction in tumor formation. Injection of similar cells directly into the brains of mice found no tumor formation when OSMR was absent. In an interview posted by Genetic Engineering News, senior author Michael Rudnicki recalled his team’s reaction to this finding:

“Being able to stop tumor formation entirely was a dramatic and stunning result. It means that this protein is a key piece of the puzzle, and could be a possible target for future treatments.”

Three proteins form a vicious cycle toward cancerous growth
Additional experiments testing the interactions between EGFRvIII, STAT3 and OSMR point out where those future treatments should act. Like the screeching audio feedback you hear when a microphone is held too close to a speaker, the team showed these three proteins create a self amplifying signal. In the tumor stem cells, EGFRvIII comes in direct physical contact with OSMR and together these two proteins act as co-receptors to activate STAT3 which, in turn, stimulates the production of OSMR which, in turn, stimulates even more STAT3 production. And so on and so on.

Co-senior author, Azad Bonni, explained how they intend to break up this vicious cycle while also acknowledging these are very early days for developing a treatment:

“The next step is to find small molecules or antibodies that can shut down the protein OSMR or stop it from interacting with EGFR. But any human treatment targeting this protein is years away.”

Watch this video to hear from the study’s first author, Arezu Jahani-Asl, now an assistant professor at McGill university:

 

Stem cell stories that caught our eye: fashionable stem cells, eliminating HIV, cellular Trojan horse fights cancer

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.

Stem cell fashion for a cause. Science and art are not mutually exclusive subjects. I know plenty of scientists who are talented painters or designers. But you don’t often see science being displayed in an artistic way or art being used to help explain complex scientific topics. I think that in the future, this will change as both subjects have a lot to offer one another.

Stem cell ties are in fashion!

Stem cell ties are in fashion!

Take this story from the University of Michigan for instance. Designer Dominic Pangborn has joined forces with the Heinz C. Prechter Bipolar Research Fund at the University of Michigan (UOM) to design fashionable scarves and ties featuring beautiful pictures of stem cells. The goal of the Prechter Fund scarf and tie project is to raise awareness for mental health research.

The scarves and ties feature pictures of brain stem cells taken by UOM scientists who are studying them to understand the mechanisms behind bipolar disorder. These stem cells were generated from induced pluripotent stem cells or iPS cells that were derived from donated skin biopsies of patients with bipolar disease. Studying these diseased brain cells in a dish revealed that the nerve cells from bipolar patients were misbehaving, sending out electrical signals more frequently compared to healthy nerve cells.

Dr. Melvin McInnis, the Prechter Fund research director, explained:

“By understanding the causes of bipolar disorder, we will be able to develop new treatments for the illness and most importantly, we’ll be able to prevent destructive mood episodes. Our ultimate goal is to allow people to live happy, normal lives.”

Pangborn is passionate about using art to reflect an important cause.

“I decided to add butterflies to the design because they signify metamorphosis. Our society is finally at a point where mental illness is openly talked about and research is taking a turn for the better.”

He plans to release his collection in time for National Mental Health Awareness month in May. All proceeds will go to the Prechter bipolar research projects at UOM.

Dr. Melvin McInnis, left, and Dominic Pangborn in the Pangborn Design Store in Ann Arbor. (UOM)

Dr. Melvin McInnis, left, and Dominic Pangborn in the Pangborn Design Store in Ann Arbor. (UOM)

New stem cell therapy could eliminate HIV for good

The stem cells therapies being developed to cure HIV are looking more promising every day. A few are already being tested in clinical trials, and CIRM is funding two of them (you can read more about them here). News came out this week about a new trial conducted at the City of Hope’s CIRM Alpha Stem Cell Clinic. They reported in a news release that they’ve treated their first patient. His name is Aaron Kim, and he’s had HIV since he was born. In 1983, he and his twin sister were born prematurely and due to a complication, Aaron had to get a blood transfusion that unfortunately gave him HIV.

Aaron Kim with nurse. (City of Hope)

Aaron Kim with nurse. (City of Hope)

Aaron thought he would live with this disease the rest of his life, but now he has a chance at being cured. In March, Aaron received a transplant of his own bone marrow stem cells that were genetically engineered to have a modified version of the CCR5 gene that makes his cells resistant to HIV infection. CCR5 is a is a protein receptor on the surface of blood cells that acts as a gateway for HIV entry. The hope is that his reengineered stem cells will populate his immune system with HIV-resistant cells that can eliminate the virus completely.

Dr. John Zaia who is the director the the City of Hope Alpha Clinic explained,

“The stem cell therapy Aaron received is one of more than 20 cure strategies for HIV. It may not cure him, but our goal is to reduce or even halt Aaron’s reliance on HIV drugs, potentially eliminating the virus completely.”

My favorite part of this story was that it acknowledged how importance it is for patients to participate in clinical trials testing promising new stem cell therapies where the outcomes aren’t always known. Brave patients such as Aaron make it possible for scientists to make progress and develop better and safer treatments for patients in the future.

Dr. Zaia commented, “It’s a wonderful and generous humanitarian gesture on Aaron’s part to participate in this trial.”

Stem cell Trojan horse fights cancer

Chemotherapy is great at killing cancer cells, but unfortunately, it’s also great at killing healthy cells too. To combat this issue, scientists are developing new delivery methods that can bring high doses of chemotherapy drugs to the cancer tumors and minimize exposure of healthy tissues.

Mesenchymal stem cells loaded with drug-containing microparticles. Credit: Jeff Karp and Oren Levy, Brigham and Women's Hospital

Mesenchymal stem cells loaded with drug-containing microparticles.
Credit: Jeff Karp and Oren Levy, Brigham and Women’s Hospital

A study published this week in Biomaterials, describes a new drug delivery method that has the potential to be an effective treatment for prostate cancer. Researchers from the Brigham and Women’s Hospital and Johns Hopkins University developed a drug delivery platform using mesenchymal stem cells. They packaged a non-active, prodrug version of a potent prostate cancer chemotherapy drug into microparticles that they loaded into MSCs. When the MSCs and prostate cancer cells were cultured together in a dish, the MSCs released their prodrug cargo, which was then internalized by the prostate cancer cells. The prodrug was then metabolized into its active, cancer-killing form and was very effective at killing the cancer cells.

In a news release picked up by Science Daily, one of the lead scientists on the study, Dr. Oren Levy, further explained the stem cell Trojan horse concept:

“Mesenchymal stem cells represent a potential vehicle that can be engineered to seek out tumors. Loading those cells with a potent chemotherapeutic drug is a promising cell-based Trojan horse approach to deliver drugs to sites of cancer.”

If all goes well, the teams plan to develop different versions of their stem cell-based drug delivery method that target different cancers and other diseases.