February 19, 2021

OICR-supported collaboration discovers new method to stunt the growth of brain cancers

Inhibiting a key enzyme could help stop the growth of glioblastoma

Fewer than 10 per cent of people diagnosed with glioblastoma will survive beyond five years. Despite advances in understanding this deadly brain cancer, therapy options for this disease are severely limited. In a study recently published in Nature Communications, researchers have discovered that inhibiting a key enzyme, PRMT5, can suppress the growth of glioblastoma cells. Their findings demonstrate a novel approach to treating the disease, paving the way for a new class of therapeutics.

Dr. Peter Dirks, co-leader of OICR’s Brain Cancer Translational Research Initiative.

A multidisciplinary team with expertise in cancer stem cells, protein structures, small molecule development and multi-omic analyses enabled this discovery. The group, was co-led by Dr. Peter Dirks, Senior Scientist and Neurosurgeon at the Hospital for Sick Children (SickKids) and co-leader of OICR’s Brain Cancer Translational Research Initiative along with researchers at the Princess Margaret Cancer Centre, the Structural Genomics Consortium (SGC) and the University of Toronto. Many of the researchers involved in the study are also part of the Stand Up To Cancer (SU2C) Canada Cancer Stem Cell Dream Team, which receives support from OICR.

Through the study, they showed that inhibiting PRMT5 affected a large network of proteins that are important in cell division and growth, triggering cell senescence, and stopping the unrelenting division of cancer cells.

While PRMT5 inhibition has been previously suggested as a way to target brain and other cancers, no one has tested this strategy in a large cohort of patient tumour-derived cells that have stem cell characteristics, cells that are at the roots of glioblastoma growth.

They found that specific molecules – precursors to actual therapeutic drugs – inhibited the same enzyme, PRMT5, stopping the growth of a large portion of these patient-derived cancer stem cells. Many current drugs do not eliminate cancer stem cells, which may be why many cancers regrow after treatment.

“We used a different strategy to stop cancer cells from proliferating and seeding new tumours,” says co-senior author, Dr. Cheryl Arrowsmith, Senior Scientist at the Princess Margaret Cancer Centre who leads the University of Toronto site of the SGC. “By inhibiting one protein, PRMT5, we were able to affect a cascade of proteins involved in cell division and growth. The traditional way of stopping cell division has been to block one protein. This gives us a new premise for future development of novel, more precise therapies.”

“This strategy also has the opportunity to overcome the genetic variability seen in these tumours,” says co-senior author, Dirks, who also leads the SU2C Canada Dream Team. “By targeting processes involved in every patient tumour, which are also essential for the tumour stem cell survival, we side-step the challenges of individual patient tumour variability to finding potentially more broadly applicable therapies.”

The researchers also examined the molecular features of the patient-derived glioblastoma cells by comparing those that responded well to those that did not respond as well. They found a different molecular signature for the tumour cells that responded. In the future, this could lead to specific tumour biomarkers, which could help in identifying those patients who will respond best to this new class of drugs.

The research group will continue testing PRMT5 inhibitors to develop new therapies for people with glioblastoma.

“Right now, we have too few medicines to choose from to make precision medicine a reality for many patients,” says Arrowsmith. “We need basic research to better understand the mechanism of action of drugs, particularly in the context of patient samples. This is what will help us develop the right drugs to give to the right patients to treat their specific tumours.”

The research group also included OICR-affiliated scientists and staff researchers, Drs. Trevor Pugh, Mathieu Lupien, Benjamin Haibe-Kains, and Ahmed Aman.

Adapted from a SickKids news release.

January 4, 2021

Brain cancer linked to tissue healing, study finds

A brain scan showing a top down view of a cross-section with a glioblastoma tumour highlighted in red. (Hellerhoff, Wikimedia Commons)

Researchers discover brain cancer may develop when tissue healing runs amok, uncovering new approaches to combat the deadly disease

The healing process that follows a brain injury, such as an infection or a stroke, could spur tumour growth when the new cells generated are derailed by mutations, Toronto scientists have found. This discovery could lead to new therapy for glioblastoma patients who currently have limited treatment options with an average lifespan of 15 months after diagnosis.

The findings, published today in Nature Cancer, were made by an interdisciplinary team of researchers from OICR, the University of Toronto’s Donnelly Centre for Cellular and Biomolecular Research, The Hospital for Sick Children (SickKids) and the Princess Margaret Cancer Centre who are also on the pan-Canadian Stand Up to Cancer (SU2C) Canada Dream Team that focuses on a common brain cancer known as glioblastoma.

“Our data suggest that the right mutational change in particular cells in the brain could be modified by injury to give rise to a tumour,” says Dr. Peter Dirks, senior author of the study, OICR-supported researcher, Dream Team co-leader, and Head of the Division of Neurosurgery and a Senior Scientist in the Developmental and Stem Cell Biology program at SickKids. “We’re excited about what this tells us about how cancer originates and grows and it opens up entirely new ideas about treatment by focusing on the injury and inflammation response.”

The research group, led in part by OICR and Princess Margaret’s Dr. Trevor Pugh, applied the latest single-cell RNA sequencing and machine learning technologies to map the molecular make-up of the glioblastoma stem cells (GSCs), which Dirks’ team previously showed are responsible for tumour initiation and recurrence after treatment.

Equipped with these single-cell analysis methods, the research group was able to accurately differentiate and study different types of tumour cells. Through analyzing 26 tumours and nearly 70,000 cells, they found new subpopulations of GSCs that bear the molecular hallmarks of inflammation.

This finding suggests that some glioblastomas may start to form when the normal tissue healing process is derailed by mutations, possibly even many years before patients become symptomatic, Dirks says. Once a mutant cell becomes engaged in wound healing, it cannot stop multiplying because the normal controls are broken and this spurs tumour growth, according to the study.

The study’s authors, including co-leading researcher, Dr. Gary Bader from the Donnelly Centre as well as graduate students including Owen Whitley and Laura Richards, are now working to develop tailored therapies target these different molecular subgroups.

“There’s a real opportunity here for precision medicine.” says Pugh, who is Director of Genomics at OICR and the Princess Margaret Cancer Centre. “To dissect patients’ tumours at the single cell level and design a drug cocktail that can take out more than one cancer stem cell subclone at the same time.”

In addition to funding from the Stand Up To Cancer Canada Cancer Stem Cell Dream Team: Targeting Brain Tumour Stem Cell Epigenetic and Molecular Networks, the research was also funded by Genome Canada, the Canadian Institutes for Health Research, the Ontario Institute for Cancer Research, Terry Fox Research Institute, the Canadian Cancer Society and SickKids Foundation.

May 25, 2020

Mapping the roots of brain cancer

Dr. Hayden Selvadurai, a lead researcher on the project to identify the origins of childhood brain cancer.

OICR-funded researchers pinpoint short-lived cells that give rise to childhood brain tumours

Childhood brain tumours are remarkably complex, but understanding their origins could help researchers develop drugs to eliminate them. Where can these cells be found? How early do they appear? How do they lead to tumours? For Dr. Hayden Selvadurai, these unresolved questions were a call to action.

In a recent study, published in Cell Reports, Selvadurai and collaborators at The Hospital for Sick Children (SickKids) discovered a rare type of stem cell that gives rise to medulloblastoma, the most common type of brain cancer in children. Their study shows that these cells arise early in brain development and exist for a brief period of time – a developmental window which scientists can now home in on.

“If we can’t eliminate the stem cells at the root of medulloblastoma, we can’t effectively treat the disease,” says Selvadurai, who was a Postdoctoral Fellow under the supervision of Dr. Peter Dirks while leading this study. Dirks is Head of the Division of Neurosurgery at SickKids, Principal Investigator at The Arthur and Sonia Labatt Brain Tumour Research Centre, Professor at the University of Toronto and Co-leader of OICR’s Brain Cancer Translational Research Initiative (TRI). “These problematic cells arise amid a complex and intricate process of fetal brain development and we were able to pinpoint exactly when that happens.”

The study builds on the research group’s previous publication in Cancer Cell that traced the origins of medulloblastoma growth back to a small group of cells that distinctively expressed the SOX2 gene. Using single-cell RNA sequencing, lineage tracing and advanced imaging techniques, the team showed that these stem cells were responsible for generating all other tumour cells and could give rise to new tumours if not fully eliminated.

“I’m proud of these findings because we were able to unify our knowledge of developmental neurobiology with cancer biology,” says Selvadurai. “We were able to build on our understanding of medulloblastoma growth while improving our experimental models of brain cancer. Together, this work could help the community develop new effective treatments for patients with the disease.”

Dirks’ research group plans to further investigate the genes involved in the early stages of medulloblastoma in collaboration with OICR’s Brain Cancer TRI team.

This study was supported in part by the Canadian Institutes of Health Research and OICR through the Stand Up to Cancer (SU2C) Canada Cancer Stem Cell Dream Team.

May 6, 2020

New treatment for recurrent pediatric brain cancer enters clinical testing

Dr. Michael Taylor
Dr. Michael Taylor

OICR-supported study helps move promising CAR-T cell therapy into a first-in-child clinical trial

Recurrent brain tumours are some of the most difficult cancers to treat, with no approved targeted therapies available and only a few potential therapies in clinical trials. Developing new drug treatments for these tumours is challenging in part because the drugs must overcome the blood-brain barrier and specifically target cancer cells while sparing the surrounding critical regions of the brain. Scientists at The Hospital for Sick Children (SickKids) have discovered a new solution.

In a study, recently published in Nature Medicine, a SickKids-led research team describes a novel treatment approach that delivers chimeric antigen receptor T (CAR-T) cell therapy directly into the cerebrospinal fluid that surrounds the tumour. Their findings show that the approach was effective in treating ependymoma and medulloblastoma, two common types of brain tumours, in experimental mouse models of human disease.

“The vast majority of children with recurrent metastatic medulloblastoma or ependymoma currently have a deadly prognosis, so it is very exciting to think we have identified a novel approach to treat this underserved patient population,” says senior author Dr. Michael Taylor, Neurosurgeon, Senior Scientist in the Developmental and Stem Cell Biology program and Garron Family Chair in Cancer Research at SickKids and Co-lead of OICR’s Brain Cancer Translational Research Initiative.

CAR-T cell therapies, which use genetically engineered immune cells to attack cancer cells, are remarkably effective in treating certain types of lymphomas and leukemias. Whereas CAR-T therapies are typically delivered through the blood stream, the research team discovered that delivering their engineered T cells directly into the cerebrospinal fluid provided a better chance for the therapy to reach and eliminate brain tumours.

The team performed in-depth molecular studies to design CAR-T cells that can recognize specific molecules on the surface of brain tumour cells. They also found that the use of a complementary approved cancer medication, azactyidine, boosts the efficacy of their approach.

Now, building on these findings, collaborators at Texas Children’s Hospital have launched a first-in-child clinical trial to test the safety and anti-tumour efficacy of their new strategy.

“This work was possible thanks to the concerted collaboration of our Pediatric Cancer Dream Team, which brought together scientists studying tumor genomics and tumor immunotherapy around the world to enable the design of more effective therapies for children with incurable and hard to treat cancers,” says corresponding author Dr. Nabil Ahmed, associate professor of pediatrics and immunology, section of hematology-oncology at Baylor and Texas Children’s Hospital.

This research was supported in part by OICR through OICR’s Brain Cancer Translational Research Intitiative and funding provided to the Stand Up to Cancer (SU2C) Canada Cancer Stem Cell Dream Team.

Read SickKids news release.

July 17, 2019

New research unfolds the DNA “origami” behind brain cancers

Collaborative research group maps the three-dimensional genomic structure of glioblastoma and discovers a new therapeutic strategy to eliminate cells at the roots of these brain tumours

Current treatment for glioblastoma – the most common type of malignant brain cancer in adults – is often palliative, but new research approaches have pointed to new promising therapeutic strategies.

A collaborative study, recently published in Genome Research, has mapped the three-dimensional configuration of the genome in glioblastoma and discovered a new way to target glioblastoma stem cells – the self-renewing cells that are thought to be the root cause of tumour recurrence.

The research group integrated three-dimensional genome maps of glioblastoma with other chromatin and transcriptional datasets to describe the mechanisms regulating gene expression and detail the mechanisms that are specific to glioblastoma stem cells. They are one of the first groups in the world to perform three-dimensional genomic analyses in patient-derived tumour samples.

Dr. Mathieu Lupien

“The 3D configuration of the genome has garnered much attention over the last decade as a complex, dynamic and crucial feature of gene regulation,” says Dr. Mathieu Lupien, Senior Scientist at the Princess Margaret Cancer Centre, OICR Investigator and co-author of the study. “Looking at how the genome is folded and sets contacts between regions tens to thousands of kilobases apart allowed us to find a new way to potentially tackle glioblastoma.”

Through their study, the group discovered that CD276 – a gene which is normally involved with repressing immune responses – has a very important role in maintaining stem-cell-like properties in glioblastoma stem cells. Further, they showed that targeting CD276 may be an effective new strategy to kill cancer stem cells in these tumours.

Lupien adds that advancements in three-dimensional genomics can only be made through collaborative efforts, like this initiative, which was enabled by OICR through Stand Up 2 Cancer Canada Cancer Stem Cell Dream Team, OICR’s Brain Cancer Translational Research Initiative and other funding initiatives.

“This research was fueled by an impressive community of scientists in the area who are committed to finding new solutions for patients with brain cancer,” Lupien says. “Our findings have emphasized the significance of three-dimensional architectures in genomic studies and the need to further develop related methodologies to make sense of this intricacies.”

Senior author of the study, Dr. Marco Gallo will continue to investigate CD276 as a potential therapeutic target for glioblastoma. He plans to further delineate the architecture of these cancer stem cells to identify more new strategies to tackle brain tumours.

Dr. Marco Gallo

“A key problem with current glioblastoma treatments is that they mostly kill proliferating cells, whereas we know that glioblastoma stem cells are slow-cycling, or dormant. Markers like CD276 can potentially be targeted with immunotherapy approaches, which could be an effective way of killing cancer stem cells, irrespective of how slowly they proliferate,” says Gallo, who is an Assistant Professor at the University of Calgary. “Being able to kill cancer stem cells in glioblastoma could have strong implications for our ability to prevent relapses.”

Read more about OICR’s Brain Cancer Translational Research Initiative on oicr.on.ca or read about the Initiative’s current findings on OICR News.

April 17, 2019

Unraveling the circuitry behind brain cancer

Collaborative research group identifies new cancer-driving mechanisms in brain cancer stem cells, describes novel ways to overcome the limited effectiveness of standard therapy

Dr. Graham MacLeod works at a lab bench at the University of Toronto.

Glioblastoma is the most common and the most deadly type of brain cancer found in adults, yet there have been no new advances in treating this disease for almost two decades. Recent research has provided a wealth of knowledge about the genomics – or the abnormal genetic code – of glioblastoma, but this has yet to translate into new treatments for patients. Understanding which genes drive glioblastoma can help uncover new ways to treat this incurable disease, and a pan-Canadian research group has set out to do just that.

Researchers from the University of Toronto, The Hospital for Sick Children and the University of Calgary have teamed up to identify genetic vulnerabilities in brain cancer stem cells – the cells that often resist treatment and cause the disease to return in patients after treatment. Their recent findings, which were published today in Cell Reports, uncovered new targets for glioblastoma and unraveled some of the complex mechanisms behind the disease.

Dr. Graham MacLeod

“We set out to understand which genes are important functionally,” says Dr. Graham MacLeod, co-primary author of the study and Research Associate in the lab of Dr. Stéphane Angers at the University of Toronto. “Connecting a gene to its function is a bit like connecting circuits on a very complex circuit board. If we can understand which genes are important, then we can find hints into where to unplug, plug in, stop and start mechanisms so that we can potentially stop the progression of the disease.”

The group used CRISPR-Cas9 gene editing tools, which Angers and MacLeod specialize in, to investigate all 20,000 genes within the genome and identify the key genes that are required for glioblastoma cells to survive and grow. In their study, they identified one gene in particular whose function is already targeted in leukemia treatments. Angers says this is promising “because it uncovered a biological process, not previously suspected to be implicated in glioblastoma, for which a small molecule drug already exists.”

As part of OICR’s Brain Cancer Translational Research Initiative, the next stage of their research will use the same gene editing approach to investigate tumour cells after therapy to find the genes or the genomic changes that help tumour cells evade treatment and recur in patients.

Read more about this research on University of Toronto News or learn more about the Stand Up To Cancer Canada Cancer Stem Cell Dream Team.

November 2, 2017

Novel approach yields four robust biomarkers for breast cancer drug response

Dr. Benjamin Haibe-Kains and Zhaleh Safikhani pose for a photo

Biomarkers that can help predict a patient’s response to a given drug are central to testing new therapies in clinical trials as well as selecting which drugs to use in the clinic. Some of the biomarkers in use today rely on the overall expression of a given gene to predict if a drug will be of benefit. While these types of biomarkers have aided cancer research and treatment, a group led by Dr. Benjamin Haibe-Kains recently published research that is ushering in a new class of biomarkers – those based on gene isoforms (the different expression of the same gene within an individual). This work opens the door to more precise biomarkers.

Continue reading – Novel approach yields four robust biomarkers for breast cancer drug response

August 30, 2017

Tracking glioblastoma as it develops

Dr. Peter Dirks

An international team of scientists have used an innovative barcode-like system to track the behaviour of individual glioblastoma cells, allowing them to see how the cells of this deadly form of brain cancer have successfully evaded treatment and how they spread.

Continue reading – Tracking glioblastoma as it develops

February 4, 2016

Stand Up To Cancer Canada Announces New Cancer Stem Cell Dream Team To Attack Brain Cancer in Children and Adults

Pan-Canadian Team of Researchers Will Receive CA $11.7 Million in Funding from Stand Up To Cancer Canada, Genome Canada, Canadian Institutes of Health Research, Cancer Stem Cell Consortium, and Ontario Institute for Cancer Research

February, 4, 2016—TORONTO—A team of top Canadian scientists, including leading pioneers of stem cell research, was named today to lead a new attack on brain cancers in children and adults, using genomic and molecular profiling technologies to focus on the cancer stem cells that drive the growth of tumours.

“Brain tumours are not as common as many other forms of cancer, but they are devastating, especially when they strike the very young,” said Phillip A. Sharp, PhD, Nobel laureate and institute professor at the Massachusetts Institute of Technology’s David H. Koch Institute for Integrative Cancer Research and co-chair of the Stand Up To Cancer (SU2C) Canada Scientific Advisory Committee (SAC). “The Dream Team will bring new insights to brain cancer research, which has been an underfunded area.”

Continue reading – Stand Up To Cancer Canada Announces New Cancer Stem Cell Dream Team To Attack Brain Cancer in Children and Adults

December 22, 2015

Stand Up to Cancer Canada announces breast cancer Dream Team

Dr. Tak Mek

The first Stand Up to Cancer (SU2C) Canadian Dream Team of researchers was announced September 30, with $9 million provided over four years to support Canadian research on aggressive types of breast cancer.

The team, led by Dr. Tak Mak at the Princess Margaret Cancer Centre, will be developing new therapies aimed at changes in the genomes of cancer cells that make breast cancer tumours unstable and vulnerable to attack – the so-called “Achilles’ heel” of aggressive breast tumours. The researchers will test three candidate drugs and hope to identify biomarkers that will help to better personalize treatment for patients.

Continue reading – Stand Up to Cancer Canada announces breast cancer Dream Team