Researchers at the University of Toronto are one step closer to achieving a life-saving treatment for brain cancer by using gold nanoparticles to make radiation therapy more effective and less toxic for patients.
In their battle against glioblastoma multiforme (GBM), a rare, fast-growing cancer that begins in the brain, the multidisciplinary team found that nanoparticles can keep radiation tightly focused on the tumor, shrink its size and prevent damage elsewhere in the body .
Only a handful of researchers in the world focus on finding radiolabeled nanoparticles for brain tumors.
Anchoring of radioisotopes in the brain
In animal studies, the use of gold nanoparticles in radiation resulted in tumors that were no longer detectable by MRI four weeks after treatment. The researchers also found evidence of prolonged survival – and a potential cure – after the 150-day trial.
“There is a small group of scientists working on radiation nanomedicine globally – and an even smaller group studying the therapeutic use of radiolabeled gold nanoparticles,” says Raymond Reilly, a renowned radiopharmaceutical specialist and professor at the Leslie Dan School of Pharmacy who oversees the team.
“To my knowledge, we are one of the few groups in the world to have studied the local infusion of radiolabeled gold nanoparticles for the treatment of brain tumors.”
“We use gold nanoparticles to hold the radiation, or radioisotope, where we inject it into the brain,” explains Constantin Georgiou, a graduate student in the Department of Pharmaceutical Studies who works with Reilly.
“Without the gold nanoparticle, the radiation leaves the brain tumor, rendering it ineffective.”
The radiation also effectively obliterated tumor cells without causing any apparent damage to the brain or other body tissues – traveling no more than two millimeters from the injection site. In other words, there does not appear to be any toxicity associated with the treatment.
To assess the therapy’s effectiveness, Georgiou used innovative imaging techniques such as single-photon emission tomography (SPECT), a type of nuclear medicine imaging that allows researchers to visualize where nanoparticles are located. gold in the brain, and bioluminescence and MRI imaging to track tumor growth.
The project was first developed under Noor Al-Saden, one of 10 U of T trainees who participated in the inaugural 2019 PRiME Fellowship Awards – a program to propel high-risk, high-reward multidisciplinary research in precision medicine. PRiME is a U of T Institutional Strategic Initiative (ISI) that connects scientists, engineers, and other innovators from different disciplines to accelerate drug discovery, diagnosis, and understanding disease biology.
Preliminary results from Al-Saden’s PRiME research and a seed grant from the Brain Tumor Foundation of Canada helped Reilly’s group secure a $200,000 innovation grant from the Canadian Cancer Society.
The development of nanomedicine by radiation requires a multidisciplinary approach.
At U of T, the research would not have been possible without the expertise of a world-renowned polymer chemist Mitch Winnik, professor in the chemistry department of the Faculty of Arts and Sciences. This is because the radioisotope – in this case, lutetium-177 – is attached to the gold nanoparticles by a polymer synthesized by Winnik’s group, a substance composed of large molecules with various metal-binding sites.
The team’s next phase of research will take place in a new space at the U of T: the Leslie Dan School of Pharmacy’s Good Manufacturing Practices (GMP) facility. Made possible by a $1.3 million grant awarded to Reilly by the Canada Foundation for Innovation and the Ontario Research Fund, the facility was launched earlier this year to create radiopharmaceuticals for clinical trials.
Georgiou and Reilly are currently studying radiation nanomedicine combined with immunotherapy to provide a longer-lasting tumor response to treat GBM. The group also plans to study the effectiveness of other radioisotopes attached to gold nanoparticles, which could achieve even greater precision in erasing cancer cells.
A better understanding of energy metabolism in brain disorders by making ‘mini brains’
Reilly and Georgiou’s research isn’t the only innovative brain-focused project supported by PRiME.
Search by Angela DuongU of T alumnus and 2019 PRiME Fellow, developed 2D and 3D brain models of patients to better understand the role mitochondrial function plays in neuronal activity, particularly in patients with bipolar disorder.
Work alongside Ana Cristina Andreazza – a professor in the departments of pharmacology and toxicology and psychiatry at Temerty Medical School, with a cross-appointment at the Center for Addiction and Mental Health – Duong built 3D in vitro cultures of brain cells, also called brain organoids, to identify biological targets that can be used to guide the development of therapeutics. In doing so, Duong overcame longstanding hurdles in understanding the biology of patients with psychiatric disorders, as researchers previously relied on two limited avenues of investigation: post-mortem brain samples, which are rare , and brain imaging technologies which are expensive and may require radioactive exposure. .
Duong describes his brain organoids as “mini brains” that store patients’ genetic histories, allowing researchers to study human-specific processes that could be linked to patients’ clinical diagnosis. She says this tool is useful for disease modeling compared to brain samples from animals that don’t carry the complex human genes that cause psychiatric disorders.
“In the brain, 20% of our body’s total energy budget is used to support neurotransmission. It’s a very energy-intensive process that allows brain cells to communicate with each other, Duong says. “So if there is metabolic dysfunction in the brain, the neurotransmission process is also affected, which we believe is related to the symptoms and mood changes that we commonly see in patients with psychiatric disorders. .”
“By developing ‘mini-brains’ to function as disease models, we can learn what metabolic changes occur in the brains of real patients with brain diseases without invasive brain biopsies or studying the brains of mice or rats.”
To do this, Duong took blood samples from patients with and without bipolar disorder and isolated their white blood cells. The cells were then reprogrammed into induced pluripotent stem cells (iPSCs), a stem cell that can be generated directly from a somatic cell, any cell in a living organism other than reproductive ones. Using these iPSCs, Duong then created 2D and 3D brain cells, or organoids.
Duong’s project was among the first to fully characterize the mitochondrial health of the brain, from white blood cells to iPSCs to brain organoids. This, in turn, validated whether the mitochondria remain healthy throughout the process of reprogramming and differentiation. This study provides important foundations for the creation of more sophisticated 2D and 3D brain cells for disease modeling and the study of mitochondrial dysfunction in a wide range of brain diseases.
The realization required the multidisciplinary collaboration of three different laboratories of the U of T.
In addition to Andreazza’s lab, the PRiME project called on the expertise of two professors from Temerty’s medical school to work on the 3D engineered organoids: Liliana Attisanoprofessor of biochemistry at the Temerty School of Medicine and the Donnelly Center for Cellular and Biomolecular Research, and Martin BeaulieuAssociate Professor in the Department of Pharmacology and Toxicology at Temerty Medical School.
Build self-developed brain cells
The production of organoids relies on the self-organizing properties of the cell to develop the required cell types.
The goal of Attisano’s lab was to develop protocols to produce brain organoids that were all the same size and shape to decrease variability, making it easier for researchers to find the answers to their questions. To do this, the researchers added growth factors or inhibitors that moved the cells down a neural line. After that, the cells divided and grew for about a month, just as they would in a human brain. The line can also be modified to make organoids for other parts of the body, such as the liver.
The Beaulieu laboratory, for its part, provided equipment and resources to characterize the electroactivity of neurons within organoids.
Duong’s technological model is now being used by Andreazza to further develop brain organoids to further study a range of psychiatric conditions.
Meanwhile, Attisano is making brain organoids available to researchers in Toronto through an organoid production platform called Applied Organoid Core (ApOC), funded by the Brain Canada Foundation’s 2019 Platform Support Grant and the University of Toronto’s Medicine by Design strategic initiative. The ApOC is a grant of $1,425,000. Through this project, Attisano is collaborating with other researchers who want to use brain organoids to map human brain development and disorders such as epilepsy.
“At the end of the day, brain disorders are just a kind of alteration in the molecular components that lead to altered behavior. It’s no different than a mutation that makes you susceptible to cancer. But we never had the ability to study that,” says Attisano.
“Brain organoids give us this potential.”