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.

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.