Newly developed biosensor can target leukemic stem cells

Dr. Michael Milyavsky (left) and his research student Muhammad Yassin (right). Image courtesy of Tel Aviv University.

Every three minutes, one person in the United States is diagnosed with a blood cancer, which amounts to over 175,000 people every year. Every nine minutes, one person in the United States dies from a blood cancer, which is over 58,000 people every year. These eye opening statistics from the Leukemia & Lymphoma Society demonstrate why almost one in ten cancer deaths in 2018 were blood cancer related.

For those unfamiliar with the term, a blood cancer is any type of cancer that begins in blood forming tissue, such as those found in the bone marrow. One example of a blood cancer is leukemia, which results in the production of abnormal blood cells. Chemotherapy and radiation are used to wipe out these cells, but the blood cancer can sometimes return, something known as a relapse.

What enables the return of a blood cancer such as leukemia ? The answer lies in the properties of cancer stem cells, which have the ability to multiply and proliferate and can resist the effects of certain types of chemotherapy and radiation. Researchers at Tel Aviv University are looking to decrease the rate of relapse in blood cancer by targeting a specific type of cancer stem cell known as a leukemic stem cell, which are often found to be the most malignant.

Dr. Michael Milyavsky and his team at Tel Aviv University have developed a biosensor that is able to isolate, label, and target specific genes found in luekemic stem cells. Their findings were published on January 31, 2019 in Leukemia.

In a press release Dr. Milyavsky said:

“The major reason for the dismal survival rate in blood cancers is the inherent resistance of leukemic stem cells to therapy, but only a minor fraction of leukemic cells have high regenerative potential, and it is this regeneration that results in disease relapse. A lack of tools to specifically isolate leukemic stem cells has precluded the comprehensive study and specific targeting of these stem cells until now.”

In addition to isolating and labeling leukemic stem cells, Dr. Milyavsky and his team were able to demonstrate that the leukemic stem cells labeled by their biosensor were sensitive to an inexpensive cancer drug, highlighting the potential this technology has in creating more patient-specific treatment options.

In the article, Dr. Milyavsky said:

” Using this sensor, we can perform personalized medicine oriented to drug screens by barcoding a patient’s own leukemia cells to find the best combination of drugs that will be able to target both leukemia in bulk as well as leukemia stem cells inside it.”

The researchers are now investigating genes that are active in leukemic stem cells in the hope finding other druggable targets.

CIRM has funded two clinical trials that also use a more targeted approach for cancer treatment. One of these trials uses an antibody to treat chronic lymphocytic leukemia (CLL) and the other trial uses a different antibody to treat acute myeloid leukemia (AML).

Antibody effective in cure for rare blood disorders

3D illustration of an antibody binding to a designated target.
Illustration created by Audra Geras.

A variety of diseases can be traced to a simple root cause: problems in the bone marrow. The bone marrow contains specialized stem cells known as hematopoietic stem cells (HSCs) that give rise to different types of blood cells. As mentioned in a previous blog about Sickle Cell Disease (SCD), one problem that can occur is the production of “sickle like” red blood cells. In blood cancers like leukemia, there is an uncontrollable production of abnormal white blood cells. Another condition, known as myelodysplastic syndromes (MDS), are a group of cancers in which immature blood cells in the bone marrow do not mature and therefore do not become healthy blood cells.

For diseases that originate in the bone marrow, one treatment involves introducing healthy HSCs from a donor or gene therapy. However, before this type of treatment can take place, all of the problematic HSCs must be eliminated from the patient’s body. This process, known as pre-treatment, involves a combination of chemotherapy and radiation, which can be extremely toxic and life threatening. There are some patients whose condition has progressed to the point where their bodies are not strong enough to withstand pre-treatment. Additionally, there are long-term side effects that chemotherapy and radiation can have on infant children that are discussed in a previous blog about pediatric brain cancer.

Could there be a targeted, non-toxic approach to eliminating unwanted HSCs that can be used in combination with stem cell therapies? Researchers at Stanford say yes and have very promising results to back up their claim.

Dr. Judith Shizuru and her team at Stanford University have developed an antibody that can eliminate problematic blood forming stem cells safely and efficiently. The antibody is able to identify a protein on HSCs and bind to it. Once it is bound, the protein is unable to function, effectively removing the problematic blood forming stem cells.

Dr. Shizuru is the senior author of a study published online on February 11th, 2019 in Blood that was conducted in mice and focused on MDS. The results were very promising, demonstrating that the antibody successfully depleted human MDS cells and aided transplantation of normal human HSCs in the MDS mouse model.

This proof of concept holds promise for MDS as well as other disease conditions. In a public release from Stanford Medicine, Dr. Shizuru is quoted as saying, “A treatment that specifically targets only blood-forming stem cells would allow us to potentially cure people with diseases as varied as sickle cell disease, thalassemia, autoimmune disorders and other blood disorders…We are very hopeful that this body of research is going to have a positive impact on patients by allowing better depletion of diseased cells and engraftment of healthy cells.”

The research mentioned was partially funded by us at CIRM. Additionally, we recently awarded a $3.7 million dollar grant to use the same antibody in a human clinical trial for the so-called “bubble baby disease”, which is also known as severe combined immunodeficiency (SCID). You can read more about that award on a previous blog post linked here.

Mechanical forces are the key to speedy recovery after blood cancer treatment

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Mesenchymal stem cells grown on a surface with specialized mechanical properties. Image courtesy of Krystyn Van Vliet at MIT.

Blood cancers, such as leukemia and lymphoma, are projected to be responsible for 10% of all new cancer diagnoses this year. These types of cancers are often treated by killing the patient’s bone marrow (the site of blood cell manufacturing), with a treatment called irradiation. While effective for ridding the body of cancerous cells, this treatment also kills healthy blood cells. Therefore, for a time after the treatment, patients are particularly vulnerable to infections, because the cellular components of the immune system are down for the count.

Now scientists at MIT have devised a method to make blood cells regenerate faster and  minimize the window for opportunistic infections.

Using multipotent stem cells (stem cells that are able to become multiple cell types) grown on a new and specialized surface that mimics bone marrow, the investigators changed the stem cells into different types of blood cells. When transplanted into mice that had undergone irradiation, they found that the mice recovered much more quickly compared to mice given stem cells grown on a more traditional plastic surface that does not resemble bone marrow as well.

This finding, published in the journal Stem Cell Research and Therapy, is particularly revolutionary, because it is the first time researchers have observed that mechanical properties can affect how the cells differentiate and behave.

The lead author of the study attributes the decreased recovery time to the type of stem cell that was given to mice compared to what humans are normally given after irradiation. Humans are given a stem cell that is only able to become different types of blood cells. The mice in this study, however, were give a stem cell that can become many different types of cells such as muscle, bone and cartilage, suggesting that these cells somehow changed the bone marrow environment to promote a more efficient recovery. They attributed a large part of this phenomenon to a secreted protein call ostepontin, which has previously been describe in activating the cells of the immune system.

In a press release, Dr. Viola Vogel, a scientist not related to study, puts the significance of these findings in a larger context:

“Illustrating how mechanopriming of mesenchymal stem cells can be exploited to improve on hematopoietic recovery is of huge medical significance. It also sheds light onto how to utilize their approach to perhaps take advantage of other cell subpopulations for therapeutic applications in the future.”

Dr. Krystyn Van Vliet, explains the potential to expand these findings beyond the scope of just blood cancer treatment:

“You could imagine that by changing their culture environment, including their mechanical environment, MSCs could be used for administration to target several other diseases such as Parkinson’s disease, rheumatoid arthritis, and others.”

 

Support cells have different roles in blood stem cell maintenance before and after stress

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Expression of pleiotrophin (green) in bone marrow blood vessels (red) and stromal cells (white) in normal mice (left), and in mice 24 hours after irradiation (right). UCLA Broad Stem Cell Research Center/Cell Stem Cell

A new study published in the journal Cell Stem Cell, reveals how different types of cells in the bone marrow are responsible for supporting blood stem cell maintenance before and after injury.

It was already well known in the field that two different cell types, namely endothelial cells (which line blood vessels) and stromal cells (which make up connective tissue, or tissue that provides structural support for any organ), are responsible for maintaining the population of blood stem cells in the bone marrow. However, how these cells and the molecules they secrete impact blood stem cell development and maintenance is not well understood.

Hematopoietic stem cells are responsible for generating the multiple different types of cells found in blood, from our oxygen carrying red blood cells to the many different types of white blood cells that make up our immune system.

Dr. John Chute’s group at UCLA had previously discovered that a molecule called pleiotrophin, or PTN, is important for promoting self-renewal of the blood stem cell population. They did not, however, understand which cells secrete this molecule and when.

To answer this question, the scientists developed mouse models that did not produce PTN in different types of bone marrow cells, such as endothelial cells and stromal cells. Surprisingly, they saw that the inability of stromal cells to produce PTN decreased the blood stem cell population, but deletion of PTN in endothelial cells did not affect the blood stem cell niche.

Even more interestingly, the researchers found that in animals that were subjected to an environmental stressor, in this case, radiation, the result was reversed: endothelial cell PTN was necessary for blood stem cell renewal, whereas stromal cell PTN was not. While an important part of the knowledge base for blood stem cell biology, the reason for this switch in PTN secretion at times of homeostasis and disease is still unknown.

As Dr. Chute states in a press release, this result could have important implications for cancer treatments such as radiation:

“It may be possible to administer modified, recombinant versions of pleiotrophin to patients to accelerate blood cell regeneration. This strategy also may apply to patients undergoing bone marrow transplants.”

Another important consideration to take away from this work is that animal models developed in the laboratory should take into account the possibility that blood stem cell maintenance and regeneration is distinctly controlled under healthy and disease state. In other words, cellular function in one state is not always indicative of its role in another state.

This work was partially funded by a CIRM Leadership Award.

 

 

Blood stem cell expansion expands treatment options for cancer patients

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Image courtesy of the Stower’s Institute

Bone marrow transplants have been used for decades to treat various types of cancers such as leukemia and multiple myeloma, as well as other blood disorders such as anemia.

Our bone marrow is responsible for making hematopoietic stem cells (HSCs), which develop into mature blood cells, like white cells (which fight infection) and red cells (which carry oxygen throughout our body). In different types of blood disorders, blood cell production is either impaired or abnormal. In leukemia for example, the body produces abnormal white blood cells that survive better then outgrow the normal white cells, thus impairing the individual’s ability to fight infection. Bone marrow transplants, which involves replacing the diseased marrow with healthy marrow from a donor, can be incredibly effective for these types of disease. Survival from certain blood cancers increased from basically zero to around eighty-five percent after the advent of bone marrow transplant therapy.

While extremely effective when successful, bone marrow transplants do not work for everyone and finding a match can be difficult. For example, only 30% of patients are able to find a match in their families, because of the strict requirements that must be fulfilled be a bone marrow match. Stem cells from umbilical cord blood, on the other hand, are much more likely to match a patient, because of the generally less stringent requirements to be a match. The amount of cord blood (nearly two whole cords worth of blood) needed to satisfy an adult patient’s transplant requirements, however, are significant, and can be a limiting factor in the efficiency and effectiveness of this approach. New research from Lingheng Li’s lab at the Stower’s Institute for Medical Research at the University of Kansas has found a possible solution to this problem.

In a study published in Cell Research, Li’s group found a way to increase the number of adult stem cells isolated from cord blood, which could reduce the number of cords needed per treatment. By eliminating a protein called Ythdf2 in mice, they observed global expansion of HSCs. Normally, this protein is responsible for preventing expression of genes involved in promoting HSC expansion. Importantly, the researchers found that the HSC expansion stimulated by elimination of Ythdf2 did not lead to other abnormalities in the resulting HSCs and did not affect the ability of these HSCs to produce different types of blood stem cells down the road. Dr. Li believes that this type of approach can be applied to other types of stem cell treatments as well.

Dr. Joseph McGuirk, another professor at the University of Kansas who was not directly involved with this study, indicates the importance of this work:

“This work represents a path forward by demonstrating the ability to reliably expand adult stem cells from umbilical cord blood in the laboratory without terminally differentiating the cells into more mature and relatively short-lived blood cells. These findings represent a major advance in the field and have significant potential to improve the outcomes of thousands of children and adults who undergo umbilical cord blood transplantation every year.”

CIRM is funding work in this area too. We are supporting a late stage preclinical project with AngioCrine Biosciences which is using expanded cord blood stem cells. They hope to create an effective and, safe option for the treatment of debilitating blood diseases such as leukemia and lymphoma.

The Five Types of Stem Cells

When I give an “Intro to Stem Cells” presentation to, say, high school students or to a local Rotary Club, I begin by explaining that there are three main types of stem cells: (1) embryonic stem cells (ESCs) (2) adult stem cells and (3) induced pluripotent stem cells (iPSCs). Well, like most things in science, it’s actually not that simple.

To delve a little deeper into the details of characterizing stem cells, I recommend checking out a video animation produced by BioInformant, a stem cell market research company. The video is introduced in a blog, “Do you know the 5 types of stem cells?” by Cade Hildreth, BioInformant’s founder and president.

Stem-Cell-Types

Image credit: BioInformant

Hildreth’s list categorizes stem cells by the extent of each type’s shape-shifting abilities. So while we sometimes place ESCs and iPSCs in different buckets because the methods for obtaining them are very different, in this list, they both belong to the pluripotent stem cell type. Pluri (“many”) – potent (“potential”) refers to the ability of both stem cell types to specialize into all of the cell types in the body. They can’t, though, make the cells of the placenta and other extra-embryonic cells too. Those ultimate blank-slate stem cells are called toti (“total”) – potent (“potential”).

When it comes to describing adult stem cells in my talks, I often lump blood stem cells together with muscle stem cells because they are stem cells that are present within us throughout life. But based on their ability to mature into specialized cells, these two stem cell types fall into two different categories in Hildreth’s list:  blood stem cells which can specialize into closely related cell types – the various cell types found in the blood – are considered “oligopotent” while muscle stem cells are “unipotent” because the can only mature into one type of cell, a muscle cell.

For more details on the five types of stem cells based on their potential to specialize, head over to the BioInformant blog. And scroll to the very bottom for the video animation which can also viewed on FaceBook.

It’s World Kidney Day: Highlighting CIRM’s Investments in Treating Kidney Failure

WKD-Logo-HiToday is World Kidney Day. Hundreds of events across the globe are taking place “to raise awareness of the importance of our kidneys to our overall health and to reduce the frequency and impact of kidney disease and its associated health problems worldwide.” (Side note: in recognition that today is also International Women’s Day, World Kidney Day’s theme this year is “Kidney’s & Women: Include, Value, Empower.)

To honor this day, we’re highlighting how CIRM is playing its part in that mission. The infographic below provides big picture summaries of the four CIRM-funded clinical trials that are currently testing stem cell-based therapies for kidney failure, a condition that affects well over 600,000 Americans.

When a person’s kidneys fail, their body can no longer filter out waste products and extra fluid from the blood which leads to life-threatening complications. About 30% of those affected in the U.S. have organ transplants. Due to the limited availability of donor organs, the other 70% need dialysis, a blood filtration therapy, that requires several trips a week to a special clinic.

Both treatment options have serious limitations. Organ recipients have to take drugs that prevent organ rejections for the rest of their lives. Over time, these drugs are toxic and can increase a patient’s risk of infection, heart disease, cancer and diabetes. In the case of dialysis treatment, the current procedure uses a plastic tube called a shunt to connect to a patient’s vein. These shunts are far from ideal and can lead to infection, blood clots and can be rejected by the patient’s immune system. These complications probably play a role in the average life expectancy of 5-10 years for dialysis patients.

Four CIRM-funded clinical trials aim to circumvent these drawbacks. Humacyte has received over $24 million from the Agency to support two clinical trials that are testing an alternative to the plastic shunt used in dialysis treatment. The company has developed a bioengineered vessel that is implanted in the patient’s arm and over time is populated with the patient’s own stem cells which develop into a natural blood vessel. The trials will determine if the bioengineered vessel is superior to the shunt in remaining open for longer periods of time and with lower incidence of interventions due to blood clots and infections.

The other two CIRM-funded trials, one headed by Stanford University and the other by Medeor Therapeutics, aims to eliminate the need for long-life, anti-rejection medicine after kidney transplant. Both trials use a similar strategy: blood stem cells and immune cells from the organ donor are infused into the patient receiving the organ. If all goes as planned, those donor cells will engraft into and mix with the recipient’s immune system, making organ rejection less likely and ending the need for immune-system suppressing drugs.

For more details visit our Clinical Trial Dashboard.

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CIRM-Funded Scientist is Developing a Stem Cell Therapy that Could Cure HIV

Photo Illustration by the Daily Beast

This week, UCLA scientist Scott Kitchen made the news for his efforts to develop a CIRM-funded stem cell gene therapy that could potentially cure patients infected with HIV. Kitchen’s work was profiled in the Daily Beast, which argued that his “research could significantly up survival rates from the virus.”

Scott Kitchen, UCLA Medicine

Kitchen and a team of scientists at the UCLA David Geffen School of Medicine are genetically modifying blood-forming, hematopoietic stem cells (HSCs) to express chimeric antigen receptors (CARs) that target HIV-infected cells. CARs are protein complexes on the surface of cells that are designed to recognize specific types of cells and are being developed as powerful immunotherapies to fight cancer and HIV infection.

These CAR-expressing HSCs can be transplanted into patients where they develop into immune cells called T cells and natural killer (NK) cells that will destroy cells harboring HIV. This strategy also aims to make patients resistant to HIV because the engineered immune cells will stick around to prevent further HIV infection.

By engineering a patient’s own blood-forming stem cells to produce an unlimited supply of HIV-resistant immune cells that can also eradicate HIV in other cells, Kitchen and his team are creating the possibility for a life-long, functional cure.

Dr. Kelly Shepard, Senior Science Officer of Discovery and Translation Research at CIRM, reflected on significance of Kitchen’s research in an interview:

Kelly Shepard

“This unique approach represents a two-pronged strategy whereby a patient’s own stem cells are engineered not only to be protected from new HIV infection, but also to produce HIV-specific CAR T cells that will seek out and destroy existing and new pools of HIV infection in that patient, ideally leading to a lifelong cure.”

Kitchen and his team are currently testing this stem cell-based CAR-T therapy against HIV in a large-animal model. Their latest findings, which were published recently in the journal PLOS Pathogens, showed that stem cell-derived human CAR T cells were effective at reducing the amount of HIV virus (called the viral load) in their animal-model. They also saw that the CAR T cells survived for more than two years without causing any toxic side effects. This work was funded by an earlier CIRM award led by another CIRM grantee, Dr. Jerome Zack, who is research collaborator of Kitchen’s.

In December 2017, Kitchen received a $1.7 million CIRM Discovery Stage Quest award so that the team can continue to optimize their stem cell CAR T therapy in animal models. Ultimately, they hope to gain insights into how this treatment could be further developed to treat patients with HIV.

Currently, there is no widely available cure for HIV and standard antiretroviral therapies are expensive, difficult for patients to manage and have serious side effects that reduce life expectancy. CIRM has awarded almost $75 million in funding to California scientists focused on developing novel stem cell-based therapies for HIV to address this unmet medical need. Three of these awards support early stage clinical trials, while the rest support earlier stage research projects like Kitchen’s.

CIRM Communications Director, Kevin McCormack, was quoted at the end Daily Beast article explaining CIRM’s strategy for tackling HIV:

“There are a lot of researchers working on developing stem cell therapies for HIV. We fund different approaches because at this stage we don’t know which approach will be most effective, and it may turn out that it’s ultimately a combination of these approaches, or others, that works.”

CIRM-Funded Clinical Trials Targeting Blood and Immune Disorders

This blog is part of our Month of CIRM series, which features our Agency’s progress towards achieving our mission to accelerate stem cell treatments to patients with unmet medical needs.

This week, we’re highlighting CIRM-funded clinical trials to address the growing interest in our rapidly expanding clinical portfolio. Today we are featuring trials in our blood and immune disorders portfolio, specifically focusing on sickle cell disease, HIV/AIDS, severe combined immunodeficiency (SCID, also known as bubble baby disease) and rare disease called chronic granulomatous disease (CGD).

CIRM has funded a total of eight trials targeting these disease areas, all of which are currently active. Check out the infographic below for a list of those trials.

For more details about all CIRM-funded clinical trials, visit our clinical trials page and read our clinical trials brochure which provides brief overviews of each trial.

CIRM-Funded Clinical Trials Targeting Cancers

Welcome to the Month of CIRM!

As we mentioned in last Thursday’s blog, during the month of October we’ll be looking back at what CIRM has done since the agency was created by the people of California back in 2004. To start things off, we’ll be focusing on CIRM-funded clinical trials this week. Supporting clinical trials through our funding and partnership is a critical cornerstone to achieving our mission: to accelerate stem cell treatments to patients with unmet medical needs.

Over the next four days, we will post infographics that summarize CIRM-funded trials focused on therapies for cancer, neurologic disorders, heart and metabolic disease, and blood disorders. Today, we review the nine CIRM-funded clinical trial projects that target cancer. The therapeutic strategies are as varied as the types of cancers the researchers are trying to eradicate. But the common element is developing cutting edge methods to outsmart the cancer cell’s ability to evade standard treatment.

For more details about all CIRM-funded clinical trials, visit our clinical trials page and read our clinical trials brochure which provides brief overviews of each trial.