Targeted treatment for pediatric brain tumors shows promising results

Image of medulloblastoma

Imagine sitting in the doctor’s office and being told the heartbreaking news that your child has been diagnosed with a malignant brain tumor. As one might expect, the doctor states that the most effective treatment option is typically a combination of chemotherapy and radiation. However, the doctor reveals that there are additional risks to take into account that apply to children. Since children’s tiny bodies are still growing and developing, chemotherapy and radiation can cause long-term side effects such as intellectual disabilities. As a parent, it is painful enough to have to watch a child go through chemotherapy and radiation without adding permanent damage into the fold.

Sadly, this scenario is not unique. Medulloblastoma is the most prevalent form of a pediatric brain tumor with more than 350 children diagnosed with cancer each year. There are four distinct subtypes of medulloblastoma, with the deadliest being known as Group 3.

Researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) are trying to minimize the collateral damage by finding personalized treatments that reduce side effects while remaining effective. Scientists at SBP are working with an inhibitor known as LSD1 that specifically targets Group 3 medulloblastoma in a mouse model. The study, published in Nature Communications, showed that the drug dramatically decreased the size of tumors grown under the mouse’s skin by shrinking the cancer by more than 80 percent. This suggested that it could also be effective against patients’ tumors if it could be delivered to the brain. The LSD1 inhibitor has shown promise in clinical trials, where it has been tested for treating other types of cancer.

According to Robert Wechsler-Reya, Ph.D., senior author of the paper and director of the Tumor Initiation and Maintenance Program at SBP: “Our lab is working to understand the genetic pathways that drive medulloblastoma so we can find better ways to intervene and treat tumors. This study shows that a personalized treatment based upon a patient’s specific tumor type might be within our reach.”

Dr. Wechsler-Reya’s work on medulloblastoma was, in part, funded by the CIRM (LA1-01747) in the form of a Research Leadership Award for $5,226,049.

Stem cell stories that caught our eye: sexual identity of organs, upping the game of muscle stem cells, mini guts produce insulin

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.

A new sexual identity crisis—in our organs. With the transition from Mr. to Ms. Jenner and other transsexual news this year, it seems inevitable that a research paper would come out suggesting we may all have some mosaic sexual identity. A team in the U.K. found that the stem cells that develop our organs can have varying sexual identities and that can impact the function of the organ.

The organ in question in this case, intestines in fruit flies, is smaller in males than in females. By turning on and off certain genes the researchers at the Medical Research Council’s Clinical Science Centre found that making stem cells in the gut more masculine reduced their ability to multiply and produced smaller intestines. They also found that female intestines were more prone to tumors, just as many diseases are more common in one sex than the other.

In an interview with Medical News Today, Bruno Hudry, the first author on the paper, which is published in Nature, talked about the likelihood that we all have some adult cells in us with genes of the opposite sex.

 “This study shows that there is a wider spectrum than just two sexes. You can be chromosomally, hormonally or phenotypically female but still having some specific adult stem cells (here the stem cells of the intestine) acting like male. So it is hard to say if someone is “really” male or female. Some people are simply a mosaic of male and female cells within a phenotypically ‘male’ or ‘female’ body.”

Hurdry speculated that if the results are duplicated in humans it could provide a window into other sex-linked differences in diseases and could be a matching factor added to the standard protocol for blood and organ donations.

 

Reprogramming stomach to produce insulin.  The stem cells in our gut show an efficiency not seen in most of our organs. They produce a new lining for our stomach and intestine every few days. On the opposite end of the spectrum, the insulin-producing cells in our pancreas rank poorly in self renewal. So, what if you could get some of those vigorous gut stem cells to make insulin producing beta cells? Turns out you can and they can produce enough insulin to allow a diabetic mouse to survive.

mini stomach

A mini-gut with insulin-producing cells (red) and stem cells (green).

A team at the Harvard Stem Cell Institute manipulated three genes known to be associated with beta cell development and tested the ability of many different tissues—from tail to snout—to produce beta cells. A portion of the stomach near the intestine, which naturally produces other hormones, easily reprogrammed into insulin producing cells. More important, if the first batch of those cells was destroyed by the team, the remaining stem cells in the tissue quickly regenerated more beta cells. Since a misbehaving immune system causes type 1 diabetes, this renewal ability could be key to preventing a return of the disease after a transplant of these cells.

In the lab the researchers pushed the tissue from the pylorous region of the stomach to self-organize into mini-stomachs along with the three genetic factors that drive beta cell production.  When transplanted under the skin of mice that had previously had their beta cells destroyed, the mice survived. The genetic manipulations used in this research could not be used in people, but the team is working on a system that could.

 “What is potentially really great about this approach is that one can biopsy from an individual person, grow the cells in vitro and reprogram them to beta cells, and then transplant them to create a patient-specific therapy,” said Qiao Zhou, the senior author. “That’s what we’re working on now. We’re very excited.”

Medicalxpress ran a story about the work published in Cell Stem Cell.

 

muscle stem cells

Muscle stem cells generate new muscle (green) in a mouse.

Better way to build muscle.  Stem cells behave differently depending on what environment they find themselves in, but they are not passive about their environment. They can actively change it. A CIRM-funded team at Sanford Burnham Prebys Medical Discovery Institute (SBP) found that fetal muscle stem cells and adult muscle stem cells make very different changes in the micro-environment around them.

Fetal muscle stem cells become very good at generating large quantities of new muscle, while the adult stem cells take the role of maintaining themselves for emergencies. As a result, when major repair is needed like in muscular dystrophies and aging, they easily get overwhelmed. So the SBP team looked for ways to make the adult stem cells behave more like their fetal predecessors.

 “We found that fetal MuSCs remodel their microenvironment by secreting specific proteins, and then examined whether that same microenvironment can encourage adult MuSCs to more efficiently generate new muscle. It does, which means that how adult MuSCs normally support muscle growth is not an intrinsic characteristic, but can be changed,” said Matthew Tierney, first author of the study in an institute press release distributed by Newswise.

The results point to paths for developing therapies for a number of muscle wasting conditions.

Mesa talk a reminder the immune system is a two-way street

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The second day of the three-day Stem Cell Meeting on the Mesa in La Jolla always ends with a public lecture. This year that slot featured no-longer-rising-star, but rather risen star, Jennifer Elisseeff, of Johns Hopkins. She provided a powerful reminder of the power of interdisciplinary research teams. Her career has always mingled cell biology, chemistry and engineering, but the highlight of her talk required her to take a sabbatical and learn more about immunology.

Jennifer Elisseeff

Jennifer Elisseeff

As director of the Hopkins’ Translational Tissue Engineering Center she has worked on complex tissue replacements for several areas of the body, with extensive work in knee damage and in and around the eye. She concentrates on the interplay of nature and nurture at the cellular level. In essence she looks at the dynamics of what genes are turned on in a cell and the role of the surrounding materials. When this is at work in a tissue-engineered implant it involves the interplay between cells and some sort of scaffold to hold them in place. In addition she finds added nuance to this exchange when mixing synthetic and natural scaffold materials.

“We are learning how these material talk to each other in a dish, but we need to know how this relates to what happens in the body.”

What surprised her in her findings was the powerful role of immune cells summonsed to an implant. Often times, in cell therapies the immune system is cast as a bad actor just working to reject the foreign cells. She found that one type of immune cell in particular, the macrophage, has two modes of operation. It can have a damaging inflammatory response or a reparative response. The toggle that can switch the macrophages from one form to the other turns out to be another immune cell, a particular type of T cell called a CD4.

Elisseeff called for the research community to become active in a sub-discipline Regenerative Immunology. She said that if we can empower the immune system’s beneficial affects, we can dramatically improve the value of tissue implants. She briefly described a study in which she enlisted the right T cells in mice to direct the macrophages to a reparative response. The result: tissue implants produced a better muscle repair.

CIRM co-sponsors the Mesa meeting along with the Alliance for Regenerative Medicine and the Sanford Consortium for Regenerative Medicine. The latter hosted the public talk in the auditorium named in honor of Duane Roth, the former vice chair of our board who died in a tragic bike accident a few years ago. He would have been proud of the standing-room only crowd and of Elisseeff’s admonishment for various fields to work together early with an aim to accelerate getting products to patients.

Pushing, pulling and dragging stem cell research forward

Government agencies are known for many things, but generally speaking a willingness to do some voluntary, deep self-examination is not one of them. However, for the last few weeks CIRM has been doing a lot of introspection as we develop a new Strategic Plan, a kind of road map for where we are heading.

Patient Advocate meeting in Los Angeles: Photo courtesy Cristy Lytal USC

Patient Advocate meeting in Los Angeles:
Photo courtesy Cristy Lytal USC

But we haven’t been alone. We’ve gone to San Diego, Los Angeles and San Francisco to talk to Patient Advocates in each city, to get their thoughts on what we need to focus on for the future. Why Patient Advocates? Because they are the ones with most skin in the game. They are why we do this work so it’s important they have a say in how we do it.

As Chris Stiehl, a Patient Advocate for type 1 diabetes, said in San Diego: “Let the patient be in the room, let them be part of the conversation about these therapies. They are the ones in need, so let them help make decisions about them right from the start, not at the end.”

A Strategic Plan is, on the surface, a pretty straightforward thing to put together. You look at where you are, identify where you want to go, and figure out the best way to get from here to there. But as with many things, what seems simple on the surface often turns out to be a lot more complicated when looked at in more depth.

The second bit, figuring out where you want to go, is easy. We want to live up to our mission of accelerating the development of stem cells therapies to patients with unmet medical needs. We don’t want to be good at this. We want to be great at this.

Dr. C. Randal Mills talking to Patient Advocates in LA: Photo courtesy Cristy Lytal, USC

Dr. C. Randal Mills talking to Patient Advocates in LA: Photo courtesy Cristy Lytal, USC

The first part, seeing where you are, is a little tougher: it involves what our President and CEO, Dr. Randy Mills, “confronting some brutal facts”, being really honest in assessing where you are because without that honesty you can’t achieve anything.

So where are we as an agency? Well, we have close to one billion dollars left in the bank, we have 12 projects in clinical trials and more on the way, we have helped advance stem cells from a fledgling field to a science on the brink of what we hope will be some remarkable treatments, and we have a remarkable team ready to help drive the field still further.

But how do we do that, how do we identify the third part of the puzzle, getting from where we are to where we want to be? CIRM 2.0 is part of the answer – developing a process to fund research that is easier, faster and more responsive to the needs of the scientists and companies developing new therapies. But that’s just part of the answer.

Some of the Patient Advocates asked if we considered focusing on just a few diseases, such as the ten largest killers of Americans, and devoting our remaining resources to fixing them. And the answer is yes, we looked at every single option. But we quickly decided against that because, as Randy Mills said:

“This is not a popularity contest, you can’t judge need by numbers, deciding the worth of something by how many people have it. We are disease agnostic. What we do is find the best science, and fund it.”

Another necessary element is developing better ways to attract greater investment from big pharmaceutical companies and venture capital to really help move the most promising projects through clinical trials and into patients. That is starting to happen, not as fast as we would like, but as our blog yesterday shows things are moving in this direction.

And the third piece of the pie is getting these treatments through the regulatory process, getting the Food and Drug Administration (FDA) to approve therapies for clinical trials. And this last piece clearly hit a nerve.

Many Patient Advocates expressed frustration at the slow pace of approval for any therapy by the FDA, some saying it felt like they just kept piling up obstacles in the way.

Dr. Mills said the FDA is caught between a rock and a hard place; criticized if it approves too slowly and chastised if it approves too fast, green lighting a therapy that later proves to have problems. But he agreed that changes are needed:

“The regulatory framework works well for things like drugs and small molecules that can be taken in pills but it doesn’t work well for cellular therapies like stem cells. It needs to do better at that.”

One Advocate suggested a Boot Camp for researchers, drilling them in the skills they’ll need to get FDA approval. Others suggested applying political pressure from Patient Advocacy groups to push for change.

As always there are no easy answers, but the meeting certainly raised many great questions. Those are all helping us focus our thinking on what needs to be in the Strategic Plan.

Randy ended the Patient Advocate events by saying the stem cell agency “is in the time business. What we do is time sensitive.” For too many people that time is already running out. We have to do everything we can to change that.