Stem cell stories that caught our eye: watching tumors grow, faster creation of stem cells, reducing spinal cord damage, mini organs

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.

Video shows tumors growing. A team at the University of Iowa used video to capture breast cancer cells recruiting normal cells to the dark side where they help tumors grow.

Led by David Soll, the team reports that cancer cells secrete a cable that can reach out and actively grab other cells. Once the cable reaches another cell, it pulls it in forming a larger tumor.

 “There’s nothing but tumorigenic cells in the bridge (between cells),” Soll said in a story in SciCasts, “and that’s the discovery. The tumorigenic cells know what they’re doing. They make tumors.”

They published their work in the American Journal of Cancer Research, and in a press release they suggested the results could provide an alternative to the theory that cancer stem cells are the engine of tumor growth.  I would guess that before too long, someone will find a way to merge the two theories into one, more cohesive story of how cancer grows.

 

3-D home creates stem cells quicker. Using a 3-D gel to grow the cells, a Swiss team reprogrammed skin cells into iPS-type stem cells in half the time that it takes in a flat petri dish. Since these induced Pluripotent Stem cells have tremendous value now in research and potentially in the future treating of patients, this major improvement in a process that has been notoriously slow and inefficient is great news.

The senior researcher Matthias Lutoff from Polytechnique Federale explained that the 3-D environment gave the cells a home closer to the environment where they would grow in someone’s body. In an article in Healthline, he described the common method used today:

 “What we currently have available is this two dimensional plastic surface that many, many stem cells really don’t like at all.”

At CIRM our goal is to get this research done as quickly as possible and to find ways to scale up any therapy so that it becomes practical to make it available to all patients who need it. Healthline quoted our CIRM scientist colleague Kevin Whittlesey on how the work would be a boon for stem cells scientists with its ability to shave months off the process of creating iPS cells.

 

Help for recent spinal cord injury.  A team at Case Western Reserve University in Cleveland used the offspring of stem cells that they are calling multi-potent adult progenitor cells (MAPCs) to modulate the immune response after spinal cord injury. They wanted to preserve some of the role of the immune system in clearing debris after an injury but prevent any overly rambunctious activity that would result in additional damage to healthy tissue and scarring.

a6353-spinalcord

They published their work in Scientific Reports and at the web portal MD the senior researcher Jerry Silver described the project as targeting a specific immune cell, the macrophage, in the early days following stroke in mice:

 

 “These were kinder, gentler macrophages. They do the job, but they pick and choose what they consume. The end result is spared tissue.”

The team injected the MAPCs into the mice one day after injury. Those cells were observed to go mostly to the spleen, which is know to be a reservoir for macrophages, and from their the MAPCs seemed to modulate the immune response.

 “There was this remarkable neuroprotection with the friendlier macrophages,” Silver explained. “The spinal cord was just bigger, healthier, with much less tissue damage.”

 

Rundown on all the mini-organs.  Regular readers of The Stem Cellar know researchers have made tremendous strides toward growing replacement organs from stem cells. You also know that with a few exceptions, like bladders and the esophagus, these are not ready for transplant into people.

Live Science web site does a fun rundown of progress with 11 different organs. They hit the more advanced esophagus and cover the early work on the reproductive tract, with items on fallopian tubes, vaginas and the penis. But most of the piece covers the early stage research that results in mini-organs, or as some have dubbed them, organoids. The author includes brain, heart, kidney, lung, stomach and liver. They also throw it the recent full ear grown on a scaffold.

Each short item comes with a photograph, mostly beautiful fluorescent microscopic images of cells forming the complex structures that become rudimentary organs.

3D printed human ear.

3D printed human ear.

Mini-stomachs.

Mini-stomachs.

This past summer we wrote about an article on work at the University of Wisconsin on the many hurdles that have to be leapt to get actual replacement organs. Progress is happening faster that most of us expected, but we still have a quite a way to go.

New drug kicks the cancer stem cell addiction

Did you know that cancer stem cells have an addiction problem? This might sound bizarre, but the science checks out.

Cancer stem cells are found in many different types of cancer tumors. They have the uncanny ability to survive even the most aggressive forms of treatment. After weathering the storm, cancer stem cells are able to divide and repopulate an entire tumor and even take road trips to create tumors in other areas of the body.

How cancer stem cells are able to survive and thrive is a question that is being actively pursued by scientists who aim to develop new strategies that target these cells.

Cancer stem cells have a Wnt addiction

To understand why a cancer stem cell is so good at staying alive and creating new tumors, you need to get down to the protein signaling level, which is basically a cascade of protein interactions that begin at the cell surface and instruct certain activities inside the cell. During embryonic development, one of the signaling pathways that’s activated is the Wnt pathway. It’s responsible for keeping embryonic stem cells in a pluripotent state where they maintain the ability to become any cell type.

As embryonic stem cells mature into adult cells, Wnt signaling plays different roles. It helps stem cells differentiate or change into cells of various tissues and helps maintain the health and integrity of those tissues. Because Wnt signaling has varying functions depending on the developmental stage of the cells, it’s important for cells to properly regulate this pathway.

It turns out that cancer stem cells don’t do this. Typically cells need to receive certain biochemical signals to activate the Wnt pathway, but cancer stem cells acquire genetic mutations and evolve such that this pathway is constantly activated. They ramp up their Wnt signaling and never turn it off. This “Wnt addiction” allows them to stay alive and flourish in a cancerous stem cell state.

Kicking the Wnt Addiction

A team at the Max Delbruck Center (MDC) in Germany decided to kick this Wnt addiction and make cancer stem cells go cold turkey. They published their results in the journal Cancer Research this week.

Their strategy involved targeting proteins called transcription factors, the activators of genes, that are turned on during aberrant Wnt signaling in cancer stem cells. The transcription factor they focused on is called TCF4. In normal cells, biochemical signals are required to activate the Wnt cascade and a protein called beta-catenin, which transmits signals to transcription factors like TCF4 that then turn on genes. In cancer stem cells, this signal isn’t required because the Wnt pathway is permanently switched on leaving TCF4 free to activate genes that promote tumor cell survival and growth.

The researchers thought that if they could break up the partnership between beta-catenin and TCF4, that they might be able to block Wnt signaling and kill the life-line of the cancer stem cells. They screened a library of drugs and identified a small molecule called LF3 that was able to block the interaction between beta-catenin and TCF4.

A new drug kills that cancer stem cells. The image on the left shows beta catenin (red) in cell nuclei indicating that these are cancer stem cells. The image on the right shows that the new substance sucessfully removed beta catenin from the nuclei. Picture by Liang Fang for the MDC

Cancer stem cells express beta-catenin shown in red on the left. On the right, drug treatment blocks Wnt signaling and removes beta-catenin from the cancer stem cells. (Image: Liang Fang for the MDC)

The scientists tested the LF3 molecule in mice with tumors derived from human colon cancer stem cells. Senior author on the study, Walter Birchmeier, explained in an MDC press release:

Walter

Walter Birchmeier

“We observed a strong reduction of tumor growth. What remained of the tumors seemed to be devoid of cancer stem cells – LF3 seemed to be powerfully triggering these cells to differentiate into benign tissue. At the same time, no signaling systems other than Wnt were disturbed. All of these factors make LF3 very promising to further develop as a lead compound, aiming for therapies that target human tumors whose growth and survival depend on Wnt signaling.”

Upon further analysis, they found that LF3 prevented cancer stem cells from dividing into more stem cells and migrating to other tissues. Instead, they differentiated into non-cancerous tissues. Importantly, the drug did not negatively affect the function of healthy cells nearby. This is a logical concern as Wnt signaling is activated in healthy adult tissue, just in a different way than in stem cells.

This study offers a new angle for cancer treatment. Not only does LF3 force cancer stem cells to kick their “Wnt addiction”, it also spares healthy cells and tissues. This drug sounds like a promising option for patients who suffer from aggressive, recurring tumors caused by cancer stem cells.


 

Related Links:

 

Stem cell stories that caught our eye: colon cancer relapse and using age, electricity and a “mattress” to grow better hearts

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 yield markers for relapse in colon cancer. Some colon cancer patients do fine after surgery without any chemotherapy, but it has been hard to predict which ones. A CIRM-funded team at the University of California, San Diego, with collaborators at Stanford and Columbia Universities, found a predictor for the need for chemotherapy by looking at the patients’ cancer stem cells.

colon cancer stem cells

Patients whose colon cancer stem cells tested positive for CDX2 (brown) had a better prognosis.

Previously researchers have looked for markers in the tumors themselves for differences between those who require chemotherapy and those who don’t. Those efforts generally come up empty handed. The current team instead looked for differences in the patient’s cancer stem cells. They found that patients whose stem cells lacked one protein marker called CDX2 did poorer with surgery alone and were candidates for follow-up chemotherapy.

The team published its work in this week’s New England Journal of Medicine and it got wide pickup by online news outlets, but that coverage varied somewhat depending on which group the reporters called. Medical News Today provides the Columbia angle. Newswise distributed a press release with the San Diego voice and BlackDoctor.org used quotes from Stanford as well as the American Cancer Society. The latter lets Stanford’s Michael Clark remind readers that this was a retrospective look back at prior cancer patients and the conclusions need confirmatory studies.

 “The data is extremely strong, but you need a prospective analysis to be 100 percent sure. It should be validated in a prospective trial.”

 

Three studies aim for better heart cells. While researchers have been turning stem cells into heart muscle in lab dishes for several years, getting them to function like normal heart cells either in the dish or when transplanted into animals has been tough. Three research groups published studies this week showing different approaches to making better heart muscle.

normal heart cells

Normal heart muscle cells, courtesy Kyoto University

Age matters

 Biologists at Japan’s Kyoto University found a sweet spot in the age of new muscle cells when they were most likely to engraft and survive when transplanted in animals. They first created reprogrammed iPS-type stem cells and then matured them toward becoming heart muscle for four, eight, 20 and 30 days. The 20-day cells proved the most able to engraft in the mouse hearts and improve their function as seen by echocardiography.

The Kyoto team published its results in Scientific Reports and BiotechDaily wrote an article on the work.

Give them a jolt. 

A group of physician engineers at Columbia University found that exposing lab grown heart muscle cells to electrical stimulation that mimicked the signals the cells would receive in a fetus resulted in stronger, more synchronized heart muscle. They started by engineering the heart muscle cells to grow in three dimensions and then added the electrical signals.

 “We applied electrical stimulation to mature these cells, regulate their contractile function, and improve their ability to connect with each other. In fact, we trained the cell to adopt the beating pattern of the heart, improved the organization of important cardiac proteins, and helped the cells to become more adult-like,” said Gordana Vunjak-Novakovic, the lead author on the paper published in Nature Communications.

 NewsMedical picked up the university’s press release.

Give them a mattress. 

 A team at Vanderbilt University in Tennessee found that growing the heart muscle cells on a commonly used lab gel called Matrigel resulted in cells with a shape and contractile function that matched normal heart tissue. The Matrigel formed a cushiony substrate that one team member referred to as a “mattress” for the cells to grow on that is more like the living environment in an animal than the usual lab dish.

ScienceDaily ran the university’s press release about the study published in Circulation Research. In the release, the team speculated that the matrigel worked through a combination of the flexibility of the gel and unknown growth factors released by the gel itself.

With heart disease still a leading cause of death, learning how to make better repair tissue could lead to major improvements in quality and length of lives. Of the 600-plus stem cell clinical trails currently active around the world, at least 70 target heart disease, but very few are striving to provide new tissue to repair damaged heart muscle. Generally, they are using stem cells that secrete various factors that help the heart heal itself. CIRM funds one of those trials being conducted by Capricor.

HIV/AIDS: Progress and Promise of Stem Cell Research

Our friends at Americans for Cures and Youreka Science have done it again. They’ve produced another whiteboard video about the progress and promise of stem cell research that’s so inspiring that it would probably make Darth Vader consider coming back to the light side. This time they tackled HIV.

If you haven’t watched one of these videos already, let me bring you up to speed. Americans for Cures is a non-profit organization, the legacy of the passing of Proposition 71, that supports patient advocates in the fight for stem cell research and cures. They’ve partnered with Youreka Science to produce eye-catching and informative videos to teach patients and the general public about the current state of stem cell research and the quest for cures for major diseases.

Stem cell cure for HIV?

Their latest video is on HIV, a well-known and deadly virus that attacks and disables the human immune system. Currently, 37 million people globally are living with HIV and only a few have been cured.

The video begins with the story of Timothy Brown, also known as the Berlin patient. In 2008 at the age of 40, he was dying of a blood cancer called acute myeloid leukemia and needed a bone marrow stem cell transplant to survive. Timothy was also HIV positive, so his doctor decided to use a bone marrow donor who happened to be naturally resistant to HIV infection. The transplanted donor stem cells were not only successful in curing Timothy of his cancer, but they also “rebooted his immune system” and cured his HIV.

Screen Shot 2015-12-23 at 2.21.18 PMSo why haven’t all HIV patients received this treatment? The video goes on to explain that bone marrow transplants are dangerous and only used in cancer patients who’ve run out of options. Additionally, only a small percentage of the world’s population is resistant to HIV and the chances that one of these individuals is a bone marrow donor match to a patient is very low.

This is where science comes to the rescue. Three research groups in California, all currently supported by CIRM funding, have proposed alternative solutions: they are attempting to make a patient’s own immune system resistant to HIV instead of relying on donor stem cells. Using gene therapy, they are modifying blood stem cells from HIV patients to be HIV resistant, and then transplanting the modified stem cells back into the same patient to rebuild a new immune system that can block HIV infection.

Screen Shot 2015-12-23 at 4.47.17 PM

All three groups have proven their stem cell technology works in animals; two of them are now testing their approach in early phase clinical trials in humans, and one is getting ready to do so. If these trials are successful, there is good reason to hope for an HIV cure and maybe even cures for other immune diseases.

My thoughts…

What I liked most about this video was the very end. It concludes by saying that these accomplishments were made possible not just by funding promising scientific research, but also by the hard work of HIV patients and patient advocate communities, who’ve brought awareness to the disease and influenced policy changes. Ultimately, a cure for HIV will depend on researchers and patient advocates working together to push the pace and to tackle any obstacles that will likely appear with testing stem cell therapies in human clinical trials.

I couldn’t say it any better than the final line of the video:

“We must remember that human trials will celebrate successes, but barriers will surface along with complications and challenges. So patience and understanding of the scientific process are essential.”

UCLA scientists find new targets for late-stage prostate cancer

Prostate cancer, which currently affects 3 million men in the United States, is no longer a death sentence if caught early. The five-year survival rate is very high (~98%) because of effective treatments like hormone therapy, chemotherapy, surgery, and radiation—and for many men with slow progressing tumors, the wait-and-watch approach offers an alternative to treatment.

However, for those patients who have more aggressive forms of prostate cancer, where the tumors spread to other organs and tissues, the five-year survival rate is much lower (~28%) and standard therapies only work temporarily until the tumors become resistant to them. Thus there is a need for finding new therapeutic targets that would lead to more effective and longer-lasting treatments.

Kinases are ABL to cause cancer

We recently wrote a blog about prostate cancer featuring the work of a pioneer in cancer research, Dr. Owen Witte from the UCLA Broad Stem Cell Research Center. Dr. Witte is well known for his work on understanding the biology of blood cancers (leukemias) and the role of cancer stem cells. One of his key discoveries was that the cancer-causing BCR-ABL gene produces an overactive protein kinase that causes chronic myelogenous leukemia (CML).

Protein kinases are enzymes that turn on important cell processes like growth, signaling, and metabolism, but they also can be involved in causing several different forms of cancer. This has made some kinases a prime target for developing cancer drugs that block their cancer-causing activity.

New targets for late-stage prostate cancer

Recently, Dr. Witte’s interests have turned to understanding and finding new treatments for aggressive prostate cancers. He has been on the hunt for new targets, and this week, Witte and his group published a CIRM-funded study in the journal PNAS showing that a specific set of kinases are involved in causing advanced stage prostate cancer that spreads to bones.

They selected a group of 125 kinases that are known to be active in aggressive forms of human cancers. From this pool, they found that 20 of these kinases caused metastasis, or the spreading of cancer cells from the starting tumor to different areas of the body, when activated in mouse prostate cancer cells that were injected into the tail veins of mice.

To narrow down the pool further, they activated each of the 20 kinases in human prostate cancer cells and injected these cells into the tails of mice. They found that five of the kinases caused the cancer cells to leave the tail and metastasize into the bones. When they compared the activity of these five kinases in the late-stage and early-stage prostate cancer cells as well as normal prostate cells, they only saw activity of these kinases in the late-stage cancer cells.

Microscopic view of a hip bone (left) and a magnified view of the bone showing the metastasized prostate cancer tumor (T), healthy bone marrow (M) and bone (B). Image courtesy of the UCLA Broad Stem Cell Research Center.

Microscopic view of a hip bone (left) and a magnified view of the bone showing the metastasized prostate cancer tumor (T), healthy bone marrow (M) and bone (B). Image courtesy of the UCLA Broad Stem Cell Research Center.

New treatment option?

Witte and his colleagues concluded that these five kinases can cause prostate tumor cells to spread and metastasize into bones, and that targeting kinase activity could be a new therapeutic strategy for late-stage prostate cancer patients that have exhausted normal treatment options.

In a UCLA press release, Claire Faltermeier, the study’s first author and a medical and doctoral student in Witte’s lab commented:

Our findings show that non-mutated protein kinases can drive prostate cancer bone metastasis. Now we can investigate if therapeutic targeting of these kinases can block or inhibit the growth of prostate cancer bone metastasis.

 

Dr. Witte followed up by mentioning the promise of targeting kinase activity for late-stage prostate cancer:

Cancer-causing kinase activity has been successfully targeted and inhibited before. As a result, chronic myelogenous leukemia is no longer fatal for many people. I believe we can accomplish this same result with advanced stages of prostate cancer with a fundamental understanding of the cellular nature of the disease.

UCLA scientists Owen Witte and

UCLA scientists Owen Witte and Claire Faltermeier


Related Links:

Smoking out Leukemia Cells to Prevent Cancer Relapse

Ninety-five percent of all patients with chronic myeloid leukemia (CML), carry a Frankenstein-like gene, called BCR-ABL, created from an abnormal fusion of two genes normally found on two separate chromosomes. Like a water faucet without a shutoff valve, the resulting mutant protein is stuck in an “on” position and leads to uncontrolled cell division and eventually to CML as well as other blood cancers.

104350_web

An oversized bone marrow cell, typical of chronic myeloid leukemia. Credit:  Difu Wu

Gleevec, a revolutionary, targeted cancer drug that specifically blocks the BCR-ABL protein was approved by the FDA in 2001 and doubled 5-year survival rates for CML patients (31 to 59%) over that decade. Still, some patients who are responsive to the Gleevec class of drugs, become resistant to the treatment and suffer a relapse. Up until now, research studies pointed to an accumulation of additional DNA mutations as the driving force behind a rebound of the cancer cells.

But on Monday, a CIRM-funded UC San Diego team reported in PNAS that a reduction in just one protein, called MBNL3, in CML cancer cells activates a cascade of genes normally responsible for the unlimited self-renewing capacity of embryonic stem cells. Much like a researcher can reprogram a skin cell back into an embryonic like state via the induced pluripotent stem cell (iPSC) technique, this finding suggests that CML enhances its ability to spread by exploiting the same cellular reprogramming machinery.

CML is a slowly progressing cancer that initially begins with a chronic phase. At this stage, the cancerous cells, called blast cells, make up less than five percent of cells in the bone marrow. The phase usually lasts several years and is well controlled by drug treatment. A blast crisis phase follows when the blast cells make up 20 to 30% of the blood or bone marrow. At this stage, the patient’s condition deteriorates as symptoms like anemia and frequent infections worsen.

The UCSD team, led by Catriona Jamieson, director of Stem Cell Research at Moores Cancer Center, did a comparative analysis of CML patient samples and found that a reduction of MBNL3, a RNA binding protein, corresponded with CML progression from the chronic to blast phase. If you took intro biology in high school or college, you may recall that RNA acts as a messenger molecule critical to the translation of DNA’s genetic code into proteins. Some splicing and trimming of the RNA molecule occurs to prep it for this translation process. It turns out the decrease in MBNL3 in blast phase cells frees up stretches of RNA that leads to alternate splicing and, in turn, alternate forms of a given protein.

The study showed that in response to the decrease of MBNL3, an alternate form of the protein CD44, aptly named CD44 variant 3 (CD44v3), is increased in CML blast phase cells compared with chronic phase cells. Artificially over producing CD44v3 increased the activity of SOX2 and OCT4, two genes that are critical for maintaining the properties of embryonic stem cells. Genes involved with homing blood cells to the bone marrow were also upregulated.

Put together, these data suggest that this alternate RNA splicing not only helps CML blast phase cells preserve stem cell-like qualities, but it also helps sequester them in the bone marrow. Other studies have shown that the BCR-ABL protein inhibitor drugs are not effective in eradicating blast phase cells in the bone marrow, perhaps the reason behind relapse in some CML patients.

To try to smoke out these hiding blast phase cells in mouse CML studies, the team tested a combination treatment of a CD44 inhibitor along with the BCR-ABL inhibitor. While either treatment alone effectively removed the CML blast phase cells from the spleen and blood, only the combination significantly reduced survival of the cells in the bone marrow.

This tantalizing result has motivated the Jamieson team to pursue the clinical development of a CD44 blocking antibody with combination with the existing BCR-ABL inhibitors. As reported by Bradley Fikes in a San Diego Union Tribune story, the CD44 blocking antibody was not stable so more work is still needed to generate a new antibody.

But the goal remains the same as Jamieson mentions in a UCSD press release:

“If we target embryonic versions of proteins that are re-expressed by cancer, like CD44 variant 3, with specific antibodies together with tyrosine kinase [for example, BCR-ABL] inhibitors, we may be able to circumvent cancer relapse – a leading cause of cancer-related mortality.”

 

 

 

 

 

Meet the proteins that tell stem cells where to move and how

 

Protein word art

Word cloud art work which shows all the proteins identified by the researchers

The environment you grow up in can have a huge influence on how you turn out. That applies to people, and to stem cells too. Now a new study has identified 60 proteins that can have a big impact on how cells react to the world around them, and how they communicate with each other.

Just as it is easier for us to move across firm ground than it is to slosh our way through a soggy, muddy field, it’s easier for stem cells to move smoothly and quickly over a solid surface than over a soft, giving surface. This is particularly true for tumor cells, which move much faster on a hard surface than any other kind.

It’s not just speed that is affected by the kind of surface you place stem cells on. For example certain stem cells placed on a hard surface will specialize and turn into bone, whereas if you place those same cells on a very soft surface they will turn into nerve cells.

The problem is we didn’t know much about why that was the case, we didn’t understand the mechanism at play that caused those cells to behave that way.

Now we do.

A team at the University of Manchester in England tackled this problem by researching integrins; these are receptors that are responsible for cell-to-cell communication, cell growth and function. Integrins are typically found at the surfaces and edges of cells and provide proteins with a convenient place to hang out when they interact with the world around them.

The researchers looked at 2400 examples of these integrin-protein clusters and, using mass spectrometry, narrowed their search down to 60 proteins that they identified as being essential in linking information from the integrins to the rest of the cellular world.

The work was published in Nature Cell Biology. In an accompanying news release Dr. Jon Humphries, one of the lead researchers, talked about the significance of the work:

“Understanding how cells sense their environment is an important step in understanding how, for example, cancer cells move or how stem cells take on different jobs.”

His colleague, Professor Martin Humphries, says understanding how cells sense where they are and how to behave gives us new insights into how we can use that knowledge to better control their movement:

“Our findings on how cells sense their environment have unlocked an important key to understanding how we can persuade cells to form different tissues and how we might stop cell movement in diseases such as cancer.”

 

 

A Fishy Tale: A gene that blocks regeneration in fish blocks cancer in humans

Evolution is a fascinating thing. Over time, the human race has evolved from cavemen to a bustling civilization fueled by technology, science, and economics. While we’ve gained many abilities that separate us from other mammals and our closest ancestors, the apes, we’ve also lost a number of skills along the way.

One of them is the ability to regenerate. Some animals such as lizards, fish, and frogs, have a robust capacity to regenerate entire limbs and organs while humans can only partially regenerate some tissues and organs on a much smaller scale. Why did we lose this advantageous trait?

A human gene that stops cancer also blocks regeneration

Image courtesy of Flickr.

Zebrafish. (Image courtesy of Flickr)

Scientists from UCSF have found a new piece to this evolutionary puzzle in a paper published today in eLife. They found that a gene responsible for preventing cells from growing uncontrollably into deadly cancers in humans is also able to block tissue regeneration in zebrafish.

Detailed in a UCSF news release, professor and senior author on the study, Jason Pomerantz, was always intrigued by why humans can’t regenerate limbs like salamanders. To answer these questions, he turned to model organisms like fish and amphibians:

Jason Pomerantz, UCSF

Jason Pomerantz, UCSF

In the last 10 to 15 years, as regenerative organisms like zebrafish have become genetically tractable to study in the lab, I became convinced that these animals might be able to teach us what is possible for human regeneration. Why can these vertebrates regenerate highly complex structures, while we can’t?

 

Like other scientists, Pomerantz was curious to know if humans “grew out of” their regenerative abilities in order to acquire systems that block cancer growth. Humans and other mammals have genes called tumor-suppressors that are important for regulating tissue differentiation during development and for preventing excessive cell growth and tumor formation after birth and beyond. Many of these tumor suppressor genes are conserved across a wide range of species, but Pomerantz knew of one that wasn’t shared between humans and regenerative animals, a gene called ARF.

Pomerantz and his team decided to see what happened when they added the human Arf gene into the genome of a highly regenerative animal, the zebrafish. While the addition of ARF did not affect zebrafish development, it did almost fully block their ability to regrow their tail fins after the tips were removed.

Normal zebrafish can regrow their tail fins after they are clipped, but fish that have the ARF gene cannot. (eLife)

Normal zebrafish can regrow their tail fins after they are clipped (top) , but fish that have the human ARF gene cannot (bottom). (Image from eLife)

Pomerantz explained ARF’s anti-regenerative role in the fish:

“It’s like the gene is mistaking the regenerating fin cells for aspiring cancer cells. And so it [ARF] springs into action to block it.”

Is Wolverine our future?

Wolverine. (Courtesy of wired.com)

Marvel’s Wolverine has regenerative powers. (Courtesy of wired.com)

Knowing that ARF suppresses tissue regeneration in fish, the obvious question that arises from this study is whether blocking the Arf gene in humans would promote tissue regeneration. Would doing this mean we could all be regenerative super heroes like Wolverine one day?

Pomerantz explained further in the UCSF new release that boosting regeneration in humans that need new organs or limbs could be possible but would require a careful balance to avoid setting off rampant tumor growth:

Future efforts to promote regeneration in humans will likely require carefully balanced suppression of this anti-tumor system. The same pathway in humans theoretically could be blocked to enhance researchers’ ability to grow model organs from stem cells in a laboratory dish, to enhance patients’ recovery from injury. Since tumor suppressors are thought to play a role in aging by limiting the rejuvenating potential of stem cells, blocking this pathway could even be a part of future anti-aging therapies.

Scientists will likely have to weigh the risks and benefits for human tissue regeneration on a case by case basis. Pomerantz concluded with this admission:

The ratio of risk and benefit has to be appropriate. For instance, there are certain congenital diseases that cause craniofacial deformities so severe that the risks of such a treatment might be clinically reasonable.

 

Stem cell stories that caught our eye: cancer fighting virus, lab-grown guts work in dogs, stem cell trial to cure HIV

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.

Cancer fighting virus approved for melanoma

(Disclaimer: While this isn’t a story about stem cells, it’s pretty cool so I had to include it.)

The term “virus” generally carries a negative connotation, but in some cases, viruses can be the good guys. This was the case on Tuesday when our drug approval agency, the US Food and Drug Administration (FDA), approved the use of a cancer fighting virus for the treatment of advanced stage melanoma (skin cancer).

The virus, called T-VEC, is a modified version of the herpesvirus, which causes a number of diseases and symptoms including painful blisters and sores in the mouth. Scientists engineered this virus to specifically infect cancer cells and not healthy cells. Once inside cancer cells, T-VEC does what a virus normally does and wreaks havoc by attacking and killing the tumor.

The beauty of this T-VEC is that in the process of killing cancer cells, it causes the release of a factor called GM-CSF from the cancer cells. This factor signals the human immune system that other cancer cells are nearby and they should be attacked and killed by the soldiers of the immune system known as T-cells. The reason why cancers are so deadly is because they can trick the immune system into not recognizing them as bad guys. T-VEC rips off their usual disguise and makes them vulnerable again to attack.

T-VEC recruits immune cells (orange) to attack cancer cells (pink) credit Dr. Andrejs Liepins/SPL

T-VEC recruits immune cells (orange) to attack cancer cells (pink). Photo credit Dr. Andrejs Liepins/SPL.

This is exciting news for cancer patients and was covered in many news outlets. Nature News wrote a great article, which included the history of how we came to use viruses as tools to attack cancer. The piece also discussed options for improving current T-VEC therapy. Currently, the virus is injected directly into the cancer tumor, but scientists hope that one day, it could be delivered intravenously, or through the bloodstream, so that it can kill hard to reach tumors or ones that have spread to other parts of the body. The article suggested combining T-VEC with other cancer immunotherapies (therapies that help the immune system recognize cancer cells) or delivering a personalized “menu” of cancer-killing viruses to treat patients with different types of cancers.

As a side note, CIRM is also interested in fighting advanced stage melanoma and recently awarded $17.7 million to Caladrius Biosciences to conduct a Phase 3 clinical trial with their melanoma killing vaccine. For more, check out our recent blog.

Lab-grown guts work in mice and dogs

If you ask what’s trending right now in stem cell research, one of the topics that surely would pop up is 3D organoids. Also known as “mini-organs”, organoids are tiny models of human organs generated from human stem cells in a dish. To make them, scientists have developed detailed protocols that sometimes involve the use of biological scaffolds (structures on which cells can attach and grow).

A study published in Regenerative Medicine and picked up by Science described the generation of “lab-grown gut” organoids using intestine-shaped scaffolds. Scientists from Johns Hopkins figured out how to grow intestinal lining that had the correct anatomy and functioned properly when transplanted into mice and dogs. Previous studies in this area used flat scaffolds or dishes to grow gut organoids, which weren’t able to form proper functional gut lining.

Lab-grown guts could help humans with gut disorders. (Shaffiey et al., 2015)

Lab-grown guts could help humans with gut disorders. (Shaffiey et al., 2015)

What was their secret recipe? The scientists took stem cells from the intestines of human infants or mice and poured a sticky solution of them onto a scaffold made of suture-like material. The stem cells then grew into healthy gut tissue over the next few weeks and formed tube structures that were similar to real intestines.

They tested whether their mini-guts worked by transplanting them into mice and dogs. To their excitement, the human and mouse lab-grown guts were well tolerated and worked properly in mice, and in dogs that had a portion of their intestine removed. Even more exciting was an observation made by senior author David Hackham:

“The scaffold was well tolerated and promoted healing by recruiting stem cells. [The dogs] had a perfectly normal lining after 8 weeks.”

The obvious question about this study is whether these lab-grown guts will one day help humans with debilitating intestinal diseases like Crohn’s and IBS (inflammatory bowel disorder). Hackam said that while they are still a long way from taking their technology to the clinic, “in the future, scaffolds could be custom-designed for individual human patients to replace a portion of an intestine or the entire organ.”

Clinical trial using umbilical cord stem cells to treat HIV

This week, the first clinical trial using human umbilical cord stem cells to treat HIV patients was announced in Spain. The motivation of this trial is the previous success of the Berlin Patient, Timothy Brown.

The Berlin patient can be described as the holy grail of HIV research. He is an American man who suffered from leukemia, a type of blood cancer, but was also HIV-positive. When his doctor in Berlin treated his leukemia with a stem cell transplant from a bone-marrow donor, he chose a special donor whose stem cells had an inherited mutation in their DNA that made them resistant to infection by the HIV virus. Surprisingly, after the procedure, Timothy was cured of both his cancer AND his HIV infection.

Berlin patient Timothy Brown. Photo credit: Griffin Boyce/Flickr.

Berlin patient Timothy Brown. Photo credit: Griffin Boyce/Flickr.

The National Organization of Transplants (ONT) in Spain references this discovery as its impetus to conduct a stem cell clinical trial to treat patients with HIV and hopefully cure them of this deadly virus. The trial will use umbilical cord blood stem cells instead of bone-marrow stem cells from 157 blood donors that have the special HIV-resistance genetic mutation.

In coverage from Tech Times, the president of the Spanish Society of Hematology and Hemotherapy, Jose Moraleda, was quoted saying:

“This project can put us at the cutting edge of this field within the world of science. It will allow us to gain more knowledge about HIV and parallel offer us a potential option for curing a poorly diagnosed malignant hematological disease.”

The announcement for the clinical trial was made at the Haematology conference in Valencia, and ONT hopes to treat its first patient in December or January.

Stem cells and prostate cancer are more similar than we thought

Prostate cancer is a scary word for men, no matter how macho or healthy they are. These days however, prostate cancer is no longer a death sentence for them. In fact, many men survive this disease if diagnosed early. However, for those unlucky ones who have more advanced stages of prostate cancer (where the tumor has metastasized and spread to other organs), the typical treatments used to fight the tumors don’t work effectively because advanced tumors become resistant to these therapies.

To help those afflicted with late stage prostate cancer, scientists are trying to understand the nature of prostate cancer cells and what makes them so “deadly”. By understanding the biology behind these tumor cells, they hope to develop better therapies to treat the late-stage forms of this disease.

UCLA scientists Bryan Smith and Owen Witte. (Image credit: UCLA Broad Stem Cell Research Center)

UCLA scientists Bryan Smith and Owen Witte. (Image credit: UCLA Broad Stem Cell Research Center)

But don’t worry, help is already on its way. Two groups from the University of California, Los Angeles and the University of California, Santa Cruz published a breakthrough discovery yesterday on the similarity between prostate cancer cells and prostate stem cells. The study was published in the journal PNAS and was led by senior author and director of the UCLA Broad Stem Cell Research Center, Dr. Owen Witte.

Using bioinformatics, Witte and his team compared the gene expression profiles of late-stage, metastatic prostate cancer cells sourced from tumor biopsies of living patients to healthy cell types in the male prostate. Epithelial cells are one of the main cell types in the prostate (they form the prostate glands) and they come in two forms: basal and luminal. When they compared the gene expression profiles of the prostate cancer cells to healthy prostate epithelial cells, they found that the cancer cells had a similar profile to normal prostate epithelial basal stem cells.

Image of a prostate cancer tumor. Green and red represent different stem cell traits and the yellow areas show where two stem cell traits are expressed together. (Image credit: UCLA Broad Stem Cell Research Center)

Image of a prostate cancer tumor. Green and red represent different stem cell traits and the yellow areas show where two stem cell traits are expressed together. (Image credit: UCLA Broad Stem Cell Research Center)

In fact, they discovered a 91-gene signature specific to the basal stem cells in the prostate. This profile included genes important for stem cell signaling and invasiveness. That meant that the metastatic prostate cancer cells also expressed “stem-like” genes.

First author Bryan Smith explained how their results support similar findings for other types of cancers. “Evidence from cancer research suggests that aggressive cancers have stem–cell-like traits. We now know this to be true for the most aggressive form of prostate cancer.”

So what does this study mean for prostate cancer patients? I’ll let Dr. Witte answer this one…

Treatments for early stage prostate cancer are often successful, but therapies that target the more aggressive and late-stage forms of the disease are urgently needed. I believe this research gives us important insight into the cellular nature of aggressive prostate cancer. Pinpointing the cellular traits of cancer — what makes those cells grow and spread — is crucial because then we can possibly target those traits to reverse or stop cancer’s progression. Our findings will inform our work as we strive to find treatments for aggressive prostate cancer.


Related links: