New developments in prostate cancer from UCLA

Today we’re bringing you a research update from a CIRM-funded team at UCLA that’s dedicated to finding a cure for prostate cancer. The team is led by Dr. Owen Witte, the director of the UCLA Broad Stem Cell Research Center and a Howard Hughes Investigator. Dr. Witte is well known for his work in leukemia and epithelial cancer stem cells. His interests have also expanded into prostate cancer and identifying new therapeutic targets for the most aggressive types of prostate tumors.

His team’s latest efforts, which were published in Cancer Cell last week, have unearthed a possible target for late-stage neuroendocrine prostate cancer treatment. This is a particularly nasty form of prostate cancer that is resistant to standard cancer treatments and is the cause of approximately a quarter of prostate cancer related deaths.

Myc-ing prostate cells cancerous

To study how neuroendocrine prostate cancer (NEPC) develops into uncontrollable tumors, Witte and his team developed a novel human stem cell model. They knew that patients with NEPC had abnormally high levels of a protein called N-Myc in their tumors. Witte had a hunch that maybe N-Myc was the “bad guy” that was transforming normal human prostate cells into deadly, aggressive cancer cells. So the team went on an adventure to find some answers.

Normal prostate cells (left) and neuroendocrine prostate cancer cells (right). (UCLA news release)

Normal prostate cells (left) and neuroendocrine prostate cancer cells (right). (UCLA news release)

They took normal human prostate cells from healthy donors and added the MYCN gene which then produced large amounts of N-Myc protein. After receiving an N-Myc boost, the normal basal cells developed into aggressive tumor cells. When these transformed cells were transplanted into mice, they generated NEPC tumors.

Naturally, Witte didn’t stop there. He was interested in understanding what was going on at the cellular level to transform normal prostate cells into cancer. Witte explained in a UCLA press release:

“Identifying the cellular changes that happen in cancer cells is key to the development of drugs that inhibit those changes and thereby stop the progression of the disease.”

 

Finding drugs that target prostate cancer

Further experiments revealed that N-Myc was required for maintaining the deadly nature of the NEPC tumors. If N-Myc expression was disrupted, then the tumors in the mice actually shrank. After establishing N-Myc as a therapeutic target, they went on a hunt for drugs that could block its tumor amplifying activity.

They tested a drug that originally was designed to treat childhood brain cancers that also had an N-Myc related cause. The drug, CD532, acts on a protein called Aurora A kinase. The kinase physically interacts with N-Myc and is required to keep N-Myc stable and able to do its job. When mice with NEPC tumors were treated with CD532, the effects were dramatic – their tumors shrank by as much as 80%.

Witte believes that some of the cellular mechanisms behind the growth of different cancers are conserved. He explained,

Owen Witte and first author John Lee (UCLA).

Owen Witte and first author John Lee (UCLA).

“Kinase activity is known to be implicated in many types of cancers, including chronic myelogenous leukemia, which is no longer fatal for many people due to the success of Gleevec. I believe we can accomplish this same result for people with neuroendocrine prostate cancer.”

According to Witte, the next chapter in this story will be to find other drugs that can treat NEPC possibly by targeting N-Myc. Testing CD532 in clinical trials is also an option. Thus far, the drug has only been tested in preclinical experiments and hasn’t progressed into clinical trials for safety and efficacy testing in humans.


Related links:

Scientists use human stem cell models to target deadly brain cancer

Malignant brain cancer is a devastating disease and it’s estimated that more than 16,000 patients will die of it this year. One of the most aggressive forms of brain cancer is gliomas, which originate from the support cells in the brain or spine that keep nerve cells happy and functioning. Unfortunately, there is no cure for gliomas and common treatments involving surgery, radiation and chemotherapy are not effective in fully eradicating these tumors.

3e2c6-glioma

Brain CT scan of human glioma.

In hopes of finding a cure, scientists have turned to animal models and human cell models derived from tumor biopsies or fetal tissue, to gain understanding of how gliomas form and what makes these type of tumors so deadly and resistant to normal cancer treatments.  These models have their limitations, and scientists continue to develop more relevant models in hopes of identifying new potential treatments for brain cancer.

Speaking of which, a CIRM-funded research team from the Salk Institute recently reported a new human stem cell-based model for studying gliomas in Nature Communications. The team figured out how to transform human induced pluripotent stem cells (iPS cells) into glioma tumor-initiating cells (GTICs) that they used to model how gliomas develop and to screen for drugs that specifically target this deadly form of cancer.

Making the Model

One theory for how gliomas form is that neural progenitor cells (brain stem cells) can transform and take on new properties that turn them into glioma tumor-initiating cells or GTICs, which are a subpopulation of cancer stem cells that are really good at staying alive and reproducing themselves into nasty tumors.

The Salk team created a stem cell model for glioma by generating GTICs in a dish from human iPS cells. They genetically manipulated brain progenitor cells (which they called induced neural progenitor cells or iNPCs) derived from human iPS cells to look and behave like GTICs. Building off of previous studies reporting that a majority of human gliomas have genetic mutations in the p53 and Src-family kinase (SFK) genes, they developed different iNPC lines that either turned off expression of p53, a potent tumor suppressor, or that ramped up expression of SFKs, whose abnormal expression are associated with tumor expansion.

The team then compared the transformed iNPC lines to primary GTICs isolated from human glioma tissue. They found that the transformed iNPCs shared many similar characteristics to primary GTICs including the surface markers they expressed, the genes they expressed, and their metabolic profiles.

Their final test of their stem cell model determined whether transformed iNPCs could make gliomas in an animal model. They transplanted normal and transformed iNPC lines into the brains of mice and saw aggressive tumors develop only in mice that received transformed cells. When they dissected the gliomas, they found a mixture of GTICs, more mature brain cells produced from GTICs, and areas of dead cells. This cellular makeup was very similar to that of advanced grade IV primary glioblastomas.

Screening for drugs that target glioma initiating cells

Now comes the applied part of this study. After developing a new and relevant stem cell model for glioma, the team screened their transformed iNPC lines with a panel of 101 FDA-approved anti-cancer drugs to see if any of them were effective at stopping the growth and expansion of GTICs. They identified three compounds that were able to target and kill both transformed iNPCs and primary GTICs in a dish. They also tested these compounds on living brain slices that were injected with GTICs to form tumors and saw that the drugs worked well at reducing tumor size.

The authors concluded that their transformed iNPCs are appropriate for modeling certain features of how GTICs develop into adult gliomas. Their hope is that this model will be useful for developing new targeted therapies for aggressive forms of brain cancer.

“Our results highlight the potential of hiPSCs for studying human tumourigenesis. Similar to conventional disease modeling strategies based on the use of hiPSCs, the establishment of hiPSC cancer models might facilitate the future development of novel therapeutics.”


Related Links:

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.

Breast Cancer Tumors Recruit Immune Cells to the Dark Side

We rely on our immune system to stave off all classes of disease—but what happens when the very system responsible for keeping us healthy turns to the dark side? In new research published today, scientists uncover new evidence that reveals how breast cancer tumors can actually recruit immune cells to spur the spread of disease.

Some forms of breast cancer tumors can actually turn the body's own immune system against itself.

Some forms of breast cancer tumors can actually turn the body’s own immune system against itself.

Breast cancer is one of the most common cancers, and if caught early, is highly treatable. In fact, the majority of deaths from breast cancer occur because the disease has been caught too late, having already spread to other parts of the body, a process called ‘metastasis.’ Recently, scientists discovered that women who have a heightened number of a particular type of immune cells, called ‘neutrophils,’ in their blood stream have a higher chance of their breast cancer metastasizing to other tissues. But they couldn’t figure out why.

Enter Karin de Visser, and her team at the Netherlands Cancer Institute, who announce today in the journal Nature the precise link between neutrophil immune cells and breast cancer metastasis.

They found that some types of breast tumors are particularly nefarious, sending out signals to the person’s immune system to speed up their production of neutrophils. And then they instruct these newly activated neutrophils to go rogue.

Rather than attack the tumor, these neutrophils turn on the immune system. They especially focus their efforts at blocking T cells—the type of immune cells whose job is normally to target and attack cancer cells. Further examination in mouse models of breast cancer revealed a particular protein, called interleukin 17 (or IL17) played a key role in this process. As Visser explained in today’s news release:

“We saw in our experiments that IL17 is crucial for the increased production of neutrophils. And not only that, it turns out that this is also the molecule that changes the behavior of the neutrophils, causing them to become T cell inhibitory.”

The solution then, was clear: block the connection, or pathway, between IL17 and neutrophils, and you can thwart the tumor’s efforts. And when Visser and her team, including first author and postdoctoral researcher Seth Coffelt, did this they saw a significant improvement. When the IL17-neutrophil pathway was blocked in the mouse models, the tumors failed to spread at the same rate.

“What’s notable is that blocking the IL17-neutrophil route prevented the development of metastases, but did not affect the primary tumor,” Visser added. “So this could be a promising strategy to prevent the tumor from spreading.”

The researchers are cautious about focusing their efforts on blocking neutrophils, however, as these cells are in and of themselves important to stave off infections. A breast cancer patient with neutrophil levels that were too low would be at risk for developing a whole host of infections from dangerous pathogens. As such, the research team argues that focusing on ways to block IL17 is the best option.

Just last month, the FDA approved an anti-IL17 based therapy to treat psoriasis. This therapy, or others like it, could be harnessed to treat aggressive breast cancers. Says Visser:

“It would be very interesting to investigate whether these already existing drugs are beneficial for breast cancer patients. It may be possible to turn these traitors of the immune system back towards the good side and prevent their ability to promote breast cancer metastasis.”

Combination Cancer Therapy Gives Cells a Knockout Punch

For some forms of cancer, there really is no way to truly eradicate it. Even the most advanced chemotherapy treatments leave behind some straggler cells that can fuel a relapse.

By hitting breast cancer cells with a targeted therapeutic immediately after chemotherapy, researchers were able to target cancer cells during a transitional stage when they were most vulnerable. [Credit: Aaron Goldman]

By hitting breast cancer cells with a targeted therapeutic immediately after chemotherapy, researchers were able to target cancer cells during a transitional stage when they were most vulnerable.
[Credit: Aaron Goldman]

But now, scientists have devised a unique strategy, something they are calling a ‘one-two punch’ that can more effectively wipe out dangerous tumors, and lower the risk of them ever returning for a round two.

Reporting in the latest issue of the journal Nature Communications, bioengineers at Brigham and Women’s Hospital (BWH) in Boston describe how treating breast cancer cells with a targeted drug immediately after chemotherapy was effective at killing the cancer cells and preventing a recurrence. According to lead scientist Shiladitya Sengupta, these findings were wholly unexpected:

“We were studying the fundamentals of how [drug] resistance develops and looking to understand what drives [cancer] relapse. What we found is a new paradigm for thinking about chemotherapy.”

In recent years, many scientists have suggested cancer stem cells are one of the biggest hurdles to curing cancer. Cancer stem cells are proposed to be a subpopulation of cancer cells that are resistant to chemotherapy. As a result, they can propagate the cancer after treatment, leading to a relapse.

In this work, Sengupta and his colleagues treated breast cancer cells with chemotherapy. And here is where things started getting interesting.

After chemotherapy, the breast cancer cells began to morph into cells that bore a close resemblance to cancer stem cells. For a brief period of time after treatment, these cells were neither fully cancer cells, nor fully stem cells. They were in transition.

The team then realized that because these cells were in transition, they may be more vulnerable to attack. Testing this hypothesis in mouse models of breast cancer, the team first zapped the tumors with chemotherapy. And, once the cells began to morph, they then blasted them with a different type of drug. The tumors never grew back, and the mice survived.

Interestingly, the team did not have similar success when they altered the timing of when they administered the therapy. Treating the mice with both types of drugs simultaneously didn’t have the same effect. Neither did increasing the time between treatments. In order to successfully treat the tumor they had a very slim window of opportunity.

“By treating with chemotherapy, we’re driving cells through a transition state and creating vulnerabilities,” said Aaron Goldman, the study’s first author. “This opens up the door: we can then try out different combinations and regimens to find the most effective way to kill the cells and inhibit tumor growth.”

In order to test these combinations, the researchers developed an ‘explant,’ a mini-tumor derived from a patient’s biopsy that can be grown in an environment that closely mimics its natural surroundings. The ultimate goal, says Goldman, is to map the precise order and timing of this treatment regimen in order to move toward clinical trials:

“Our goal is to build a regimen that will be [effective] for clinical trials. Once we’ve understood specific timing, sequence of drug delivery and dosage better, it will be easier to translate these findings clinically.”

Scientists identify gene that causes good protein to turn bad

shutterstock_200363513

There exists a protein that, most of the time, helps keep the growth of cancer cells in check. But every so often it does the opposite—with potentially deadly consequences.

But now, researchers have discovered precisely why this protein, known as TGF-beta, can perform such an abrupt about-face. The results, published today in the journal Science Signaling, shed light on potential therapies that can succeed where others have failed—and attack the most aggressive forms of cancer.

TGF-beta is a type of tumor suppressor, a protein that normally keeps cells from growing, dividing and multiplying too quickly, which is how most tumors originate. But scientists have long observed that in many forms of cancer, TGF-beta has switched sides: it becomes a tumor promoter fostering the out-of-control growth of cells.

In this study, scientists at the University of Michigan Comprehensive Cancer Center have figured out that a gene called Bub1 seems to be pulling the strings—essentially flipping the switch on TGF-beta. The finding that Bub1 played such an important role in regulating TGF-beta caught the team completely off guard. According to the paper’s senior author Alnawaz Rehemtulla:

“Bub1 is well-known for its role in cell division. But this is the first study that links it to TGF-beta. We think this may explain the paradox of TGF-beta as a tumor promoter and a tumor suppressor.”

The team reached this conclusion by screening gene candidates against lung cancer and breast cancer cells. After screening over 700 genes, they narrowed down the potential gene to Bub1.

Further experiments revealed that Bub1 physically binds to TGF-beta, turning it to a tumor promoter in the process. And when the team prevented Bub1 from binding to TFG-beta, essentially blocking it, TGF-beta never turned sides.

These initial results have left the research team optimistic, in large part because Bub1 is known to be active, or ‘expressed,’ in so many forms of cancer. So, if they can find a way to block Bub1 in one type of cancer, they may be able to do so with other types.

Even at this early stage, the team has developed a compound that could block Bub1. Initial lab tests show that this so-called Bub1 ‘inhibitor’ could shut off the gene without affecting surrounding regions. Said Rehemtulla:

“When you look at gene expression in cancer, Bub1 is in the top five…. But we never knew why. Now that we have that link, we’re a step closer to shutting down this cycle.”

A Tumor’s Trojan Horse: CIRM Researchers Build Nanoparticles to Infiltrate Hard-to-Reach Tumors

Some tumors are hard to find, while others are hard to destroy. Fortunately, a new research study from the University of California, Davis, has developed a new type of nanoparticle that could one day do both.

UC Davis scientists have developed a new type of nanoparticle to target tumor cells.

UC Davis scientists have developed a new type of nanoparticle to target tumor cells.

Reporting in the latest issue of Nature Communications, researchers in the laboratory of UC Davis’ Dr. Kit Lam describe a type of ‘dynamic nanoparticle’ that they created, which not only lights up tumors during an MRI or PET scan, but which may also serve as a microscopic transport vehicle, carrying chemotherapy drugs through the blood stream—and releasing them upon reaching the tumor.

This is not the first time scientists have attempted to develop nanoparticles for medicinal purposes, but is perhaps one of the more successful. As Yuanpei Li, one of the study’s co-first authors stated in a news release:

“These are amazingly useful particles. As a contrast agent, they make tumors easier to see on MRI and other scans. We can also use them as vehicles to deliver chemotherapy directly to tumors.”

Nanoparticles can be constructed out of virtually any material—but the material used often determines for what purpose they can be used. Nanoparticles made of gold-based materials, for example, may be strong for diagnostic purposes, but have been shown to have issues with safety and toxicity. On the flip side, nanoparticles made from biological materials are safer, but inherently lack imaging ability. What would be great, the team reasoned, was a new type of nanoparticle that had the best qualities of both.

In this study, which was funded in part by CIRM, Lam and the UC Davis team devised a new type of nanoparticle that was ‘just right,’—simple to make, safe and able to perform the desired task, in this case: attack tumors.

Built of organic porphyrin and cholic acid polymers and coated with the amino acid cysteine, the 32 nanometer-wide particles developed in this study offer a number of advantages over other models. They are small enough to pass into tumors, can be filled with a chemo agent and with a specially designed cysteine coating, and don’t accidentally release their payload before reaching their destination.

And this is where the truly ingenious part kicks in. With a simple flash of light, the researchers could direct the particles to drop their payload—at just the right time, offering some intriguing possibilities for new ways to deliver chemotherapy drugs.

But wait, there’s more. The fact that these new particles, which the team are calling cysteine nanoparticles, or CNP’s, appear to congregate inside tumors means that they also end up being easy to spot on an MRI.

Continued Li in the same release:

“These particles can combine imaging and therapeutics. We could potentially use them to simultaneously deliver treatment and monitor treatment efficacy. This is the first nanoparticle to perform so many different jobs. From delivering chemo, photodynamic and photothermal therapies to enhancing diagnostic imaging. It’s the complete package.”

And while the team cautions that these results are preliminary, they open the door to an entirely new and far more exact method of drug delivery to tumors—no matter how well-hidden in the body they may be.