Houston Methodist Neurological Institute researchers from the department of neurosurgery shrunk a deadly glioblastoma tumor by more than a third using a helmet generating a noninvasive oscillating magnetic field that the patient wore on his head while administering the therapy in his own home. The 53-year-old patient died from an unrelated injury about a month into the treatment, but during that short time, 31% of the tumor mass disappeared. The autopsy of his brain confirmed the rapid response to the treatment.
“Thanks to the courage of this patient and his family, we were able to test and verify the potential effectiveness of the first noninvasive therapy for glioblastoma in the world,” said David S. Baskin, M.D., FACS, FAANS, corresponding author and director of the Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment in the Department of Neurosurgery at Houston Methodist. “The family’s generous agreement to allow an autopsy after their loved ones’ untimely death made an invaluable contribution to the further study and development of this potentially powerful therapy.”
In a case study published in Frontiers in Oncology Baskin and his colleagues detailed the journey of their pioneering patient who suffered from end-stage recurrent glioblastoma, despite a radical surgical excision, chemoradiotherapy and experimental gene therapy.
Glioblastoma is the deadliest of brain cancers in adults, nearly always fatal, with a life expectancy of a few months to two years. When the patient’s glioblastoma recurred in August 2019, Baskin and his team, already working on the OMF treatment in mouse models, received FDA approval for compassionate use treatment of the patient with their newly invented Oncomagnetic Device under an Expanded Access Program (EAP). The protocol also was approved by the Houston Methodist Research Institute Institutional Review Board.
The treatment consisted of intermittent application of an oscillating magnetic field generated by rotating permanent magnets in a specific frequency profile and timing pattern. First administered for two hours under supervision in the Peak Clinic, ensuing treatments were given at home with help from the patient’s wife, with increasing treatment times up to a maximum of only six hours per day.
The Oncomagnetic Device looks deceptively simple: three oncoscillators securely attached to a helmet and connected to a microprocessor-based electronic controller operated by a rechargeable battery, an invention by case study co-author Dr. Santosh Helekar. During the patient’s five weeks of treatment, the magnetic therapy was well-tolerated and the tumor mass and volume shrunk by nearly a third, with shrinkage appearing to correlate with the treatment dose.
Co-authored by associate professor of neurosurgery Santosh Helekar, M.D., Ph.D., research professor Martyn A. Sharpe, Ph.D., and biomedical engineer Lisa Nguyen, the case study is entitled “Case Report: End-Stage Recurrent Glioblastoma Treated with a New Noninvasive Non-Contact Oncomagnetic Device.” The ongoing research is supported by the Translational Research Initiative of the Houston Methodist Research Institute, Donna and Kenneth Peak, the Kenneth R. Peak Foundation, the John S. Dunn Foundation, the Taub Foundation, the Blanche Green Fund of the Pauline Sterne Wolff Memorial Foundation, the Kelly Kicking Center Foundation, the Gary and Marlee Swarz Foundation, the Methodist Hospital Foundation and the Veralan Foundation.
“Imagine treating brain cancer without radiation therapy or chemotherapy,” said Baskin. “Our results in the laboratory and with this patient open a new world of non-invasive and nontoxic therapy for brain cancer, with many exciting possibilities for the future.”
The methylation changes also resulted in transcriptomic changes with 341 differentially expressed genes in CD4 tumor infiltrating T-cells compared to blood.
Analysis of specific genes involved in CD4 differentiation and function revealed differential methylation status of TBX21, GATA3, RORC, FOXP3, IL10 and IFNG in tumor CD4 T-cells.
Interestingly, the authors observed dysregulation of several ligands of T cell function genes in GBM tissue corresponding to the T-cell receptors that were dysregulated in tumor infiltrating CD4 T-cells.
These Oncotarget results suggest that GBM might induce epigenetic alterations in tumor infiltrating CD4 T-cells there by influencing anti-tumor immune response by manipulating differentiation and function of tumor infiltrating CD4 T-cells.
These Oncotarget results suggest that GBM might induce epigenetic alterations in tumor infiltrating CD4 T-cells
In the tumor microenvironment, lineage commitments of CD4 T cells reflect initiation of new programs of gene expression within tumor infiltrating naïve T cells.
The GBM tumor microenvironment is known to be extremely immunosuppressive, possessing multiple unique properties including:
Impaired cellular immunity no dearth of tumor infiltrating T cells
High levels of TGFβ secreted by resident as well as circulating microglia and
Expression of several inhibitory ligands, eliciting anergy and apoptosis of cytotoxic lymphocytes in the TME, immune checkpoints expression, and increased infiltration of immunosuppressive cells.
Genome wide methylation sequencing showed 13571 uniquely differentially methylated regions , mostly concentrated around the TSS, in the CD4 T cells from GBM patient tumor compared to blood.
Furthermore, combining transcriptomic data from RNAseq analysis with DNA methylation, we observed differential methylation of gene sets specific for CD4 T cells including Th1, Th2, Th17 and iTregs in GBM tumors, although with significant interpatient variability.
In conclusion, this data for the first time, report unique DNA methylation pattern and gene expression profiles in GBM associated tumor infiltrating CD4 T cells compared to CD4 T-cell from the blood of the same patient and some of their ligands on the GBM cells suggesting that CD4 T cells function and differentiation may be influenced by the GBM TME by way of epigenetic mechanisms such as, DNA methylation.
The Dey Research Team concluded in their OncotargetResearch Output, “in the present clinical corelative report, we demonstrated that differential DNA methylation pattern might influence gene expression in tumor infiltering CD4+ T cells as compared to circulating blood CD4+ T cells in GBM patients. Our findings provide evidence that GBM might be influencing the state of tumor infiltrating CD4+ T cells by epigenetic modification in the form of DNA methylation of key immune function regulating genes and influencing the fate of helper T cells in the GBM TME. Based on our observations we believe that perhaps epigenetic interaction between GBM and tumor infiltrating CD4+ T cells is responsible for the immunosuppressed state seen in the GBM patients. Our data convincingly show that there is significant inter-patient variability in the GBM tumor ligand expression of various T-cell modulating ligands and consequently striking differences in the methylation pattern and gene expression in tumor infiltrating CD4+ T-cells. This has a very strong implication for selecting future patients for immunotherapy trials who will have better likelihood of responding to immunotherapy than others based on their tumor immune signature. The findings from our corelative study needs to be further validated in the experimental setting.“
Reference: Bam M., Chintala S., Fetcko K., Williamsen B. Carmen, Siraj S., Liu S., Wan J., Xuei X., Liu Y., Leibold A. T., Dey M. Genome wide DNA methylation landscape reveals glioblastoma’s influence on epigenetic changes in tumor infiltrating CD4+ T cells. Oncotarget. 2021; 12: 967-981. Retrieved from https://www.oncotarget.com/article/27955/text/
Deleting the TFG-β receptor in NK cells overcame immune suppression and enabled anti-tumor activity in preclinical models
Preclinical research from The University of Texas MD Anderson Cancer Center finds that although glioblastoma stem cells (GSCs) can be targeted by natural killer (NK) cells, they are able to evade immune attack by releasing the TFG-β signaling protein, which blocks NK cell activity. Deleting the TFG-β receptor in NK cells, however, rendered them resistant to this immune suppression and enabled their anti-tumor activity.
The findings, published today in the Journal of Clinical Investigation, suggest that engineering NK cells to resist immune suppression may be a feasible path toward using NK cell-based immunotherapies for treating glioblastoma.
“There is tremendous interest in utilizing immunotherapy to improve treatments for patients with glioblastoma, but there has been limited success to date,” said senior author Katy Rezvani, M.D., Ph.D., professor of Stem Cell Transplantation & Cellular Therapy. “We were able to overcome the immunosuppressive environment in the brain by genetically engineering NK cells, which were then able to eliminate the tumor-regenerating GSCs. We are encouraged by these early results and hope to apply similar strategies to explore NK cell therapies in additional solid tumor types.”
Glioblastoma is the most common and aggressive form of primary brain tumor in adults. Current treatments are only effective for a short time, with recurrences driven largely by small populations of therapy-resistant GSCs. Therefore, developing new treatments that can effectively target GSCs is necessary.
Published data suggests that NK cells may be capable of targeting GCSs, but it was unclear whether the stem cells would indeed be susceptible to NK-cell killing, Rezvani explained. Therefore, her team designed the study to evaluate how effective NK cells may be against GSCs.
The researchers first confirmed that NK cells could target GSCs in vitro. Non-edited NK cells from healthy donors were able to eliminate patient-derived GSCs, whereas normal brain cells, called astrocytes, were unaffected.
To explore whether NK cells are able to cross the blood-brain barrier to infiltrate brain tumors, the team examined tumor samples removed during surgery. Glioblastoma samples contained high numbers of tumor-infiltrating NK (TI-NK) cells. However, isolated TI-NK cells were unable to kill GCSs in vitro, suggesting that NK cells were suppressed in the brain.
The researchers next profiled TI-NK cells to study their level of activity using protein markers and single-cell RNA sequencing. TI-NK cells displayed signals of inhibitory responses and immune suppression relative to NK cells isolated from the blood of healthy donors.
The single-cell analysis also revealed an activation of the TGF-β signaling pathway in TI-NK cells, identifying this as a potential mechanism of immune suppression. Indeed, blocking TGF-β signaling with various inhibitors prevented GSCs from activating this pathway in NK cells and suppressing NK cell activity.
The study went on to clarify that GSCs produce TGF-β in response to direct cell-cell contact with NK cells, a process regulated by αν integrin proteins. TGF-β released by GSCs activates its corresponding receptor on NK cells, TGFBR2, to block their anti-tumor activity.
Using an in vivo model of patient-derived GSCs, the researchers showed that combining donor-derived, or allogeneic, NK cells with inhibitors targeting either αν integrins or TGF-β receptors improved tumor control relative to untreated controls.
More impressive were the results using allogeneic NK cells with TGFBR2genetically removed. Treatment with these gene-edited NK cells resulted in a significant improvement in overall survival relative to untreated controls or treatment with unedited NK cells.
“These findings support a combinatorial approach of NK cell-based immunotherapy together with disruption of the TGF-β signaling axis to overcome the immune defenses of GSCs in the brain,” Rezvani said. “Based on these findings, we are working to launch a clinical trial evaluating this experimental approach as a novel treatment for glioblastoma.”
In addition to the Moon Shots Program, this research was supported by Ann and Clarence Cazalot Jr., the Dr. Marnie Rose Foundation, the Specialized Program of Research Excellence (SPORE) in Brain Cancer (P50CA127001) and the National Institutes of Health (NIH) (CA016672; CA120813; P30CA16672). A full list of collaborating authors and their disclosures can be found with the paper here.
Preclinical research uncovers new function of MCAD protein beyond cellular energy production
Researchers at The University of Texas MD Anderson Cancer Center have discovered a novel function for the metabolic enzyme medium-chain acyl-CoA dehydrogenase (MCAD) in glioblastoma (GBM). MCAD prevents toxic lipid buildup, in addition to its normal role in energy production, so targeting MCAD causes irreversible damage and cell death specifically in cancer cells.
The study was published today in Cancer Discovery, a journal of the American Association for Cancer Research. Preclinical findings reveal an important new understanding of metabolism in GBM and support the development of MCAD inhibitors as a novel treatment strategy. The researchers currently are working to develop targeted therapies against the enzyme.
“With altered metabolism being a key feature of glioblastoma, we wanted to better understand these processes and identify therapeutic targets that could have real impact for patients,” said lead author Francesca Puca, Ph.D., instructor of Genomic Medicine. “We discovered that glioblastoma cells rely on MCAD to detoxify and protect themselves from the accumulation of toxic byproducts of fatty acid metabolism. Inhibiting MCAD appears to be both potent and specific in killing glioblastoma cells.”
To uncover metabolic genes that are key to GBM survival, the research team performed a functional genomic screen in a unique preclinical model system that permitted an in vivo study using patient-derived GBM cells. After analyzing 330 metabolism genes in this model, they discovered that several enzymes involved in fatty acid metabolism were important for GBM cells.
The team focused on MCAD because it was identified in multiple GBM models and found at high levels in GBM cells relative to normal brain tissue. In-depth studies determined that blocking MCAD in GBM cells resulted in severe mitochondrial failure caused by the toxic buildup of fatty acids, which normally are degraded by MCAD.
This resulted in a catastrophic and irreversible cascade of events from which GBM cells could not recover, explained senior author Andrea Viale, M.D., assistant professor of Genomic Medicine.
“It appears that the downregulation of this enzyme triggers a series of events that are irreversible, and the cells are poisoned from the inside,” Viale said. “Usually, tumor cells are able to adapt to treatments over time, but, based on our observations, we think it would be very difficult for these cells to develop resistance to MCAD depletion.”
While blocking MCAD appears to be detrimental to the survival of GBM cells, the research team repeatedly found that normal cells in the brain were not affected by loss of the enzyme, suggesting that targeting MCAD could be selective in killing only cancer cells. Supporting this observation is the fact that children and animals born with an MCAD deficiency are able to live normally with an altered diet.
“It has become clear that MCAD is a key vulnerability unique to glioblastoma, providing us a novel therapeutic window that may eliminate cancer cells while sparing normal cells,” said senior author Giulio Draetta, M.D., Ph.D., chief scientific officer and professor of Genomic Medicine. “We are looking for discoveries that will have significant benefits to our patients, and so we are encouraged by the potential of these findings. We are actively working to develop targeted therapies that we hope will one day provide an effective option for patients.”
The research team has characterized the three-dimensional structure of the MCAD protein in a complex with novel small molecules designed to block the activity of the enzyme. As promising drug candidates are discovered, the researchers will work in collaboration with MD Anderson’s Therapeutics Discovery division to study these drugs and advance them toward clinical trials.
A full list of collaborating authors and their disclosures can be found here. The research was supported by the National Cancer Institute (NCI) (R01 CA218139 01 A1, R37CA237421, R01CA248160, R01CA244931, P30CA046592, 2P50CA127001, DK097153, CA16672, P30CA16672), the Sewell Family Chair in Genomic Medicine, the Cancer Prevention & Research Institute of Texas (CPRIT) (RP140672, RP150519, RP170067), the CPRIT Graduate Scholar Program, the American-Italian Cancer Foundation, MD Anderson’s Moon Shots Program®, the Broach Foundation for Brain Cancer Research, the Howard and Susan Elias Foundation, the Charles Woodson Clinical Research Fund and the University of Michigan Pediatric Brain Tumor Research Initiative.
Featured image: Fatty acids (red) accumulate to toxic levels in glioblastoma cells (blue) without the MCAD enzyme. Image courtesy Francesca Puca, Ph.D.
Researchers at Istituto Italiano di Tecnologia in collaboration with Stanford Medicine and the San Raffaele Hospital have demonstrated with preclinical studies the effectiveness of a new biomedical implant for the treatment of glioblastoma multiforme
A micro-sized polymeric net wrapping around brain tumors, just like a fishing net around a shoal of fish: this is the microMESH, a new nanomedicine device capable to conform around the surface of tumor masses and efficiently deliver drugs. It has been described by the researchers of the IIT – Istituto Italiano di Tecnologia (Italian Institute of Technology) in Nature Nanotechnology. The new biomedical implant has been validated in preclinical studies that demonstrate its effectiveness for the treatment of glioblastoma multiforme.
This work has been carried out by the group of Prof. Paolo Decuzzi, head of the IIT Laboratory of Nanotechnology for Precision Medicine, in collaboration with the Neural Stem Cell Biology Laboratory of Dr. Rossella Galli at the San Raffaele Hospital in Milan and the group of Prof. Gerald Grant at the Lucile Packard Children’s Hospital of Stanford University. The study was originated within the research activities conducted by Decuzzi in the context of projects supported by the European Research Council and the Marie Sk?odowska-Curie Action program.
Although they are quite rare, brain tumors are among the most aggressive and difficult to cure. In particular, glioblastoma multiforme is the tumor with the most severe prognosis: the average survival is just over 12 months and only 5% of the patients survive beyond 5 years. Glioblastoma multiforme typically affects men and women between 45 and 75 years of age. Furthermore, unlike other malignancies, there has been no significant diagnostic and therapeutic improvements for this malignancy over the past 30 years. In fact, both the incidence of new cases and the number of deaths has remained practically unchanged. The only therapeutic strategy currently used is based on surgery, which consists of removing a part of the tumor mass and reducing intracranial pressure, followed by radiotherapy and/or chemotherapy.
The biomedical system developed by IIT and its collaborators can play a very important role in the fight against the disease, representing a possible effective alternative to the few pharmacological treatments used to date.
The microMESH has the shape of a micrometric polymeric net, it is made with biodegradable materials and wraps around the tumor mass. In fact, the micrometric thick polymeric fibers are very flexible and are arranged to form regular openings, which are also micrometric, just like the size of cancer cells. This unique feature allows the microMESH to achieve a closer interaction with the tumor mass, increasing the therapeutic efficacy. Its structure consists of two separate compartments in which different drugs can be loaded which are released towards the tumor mass in an independent, precise, and prolonged fashion. The microMESH can ‘attack’ glioblastoma by combining different therapies: chemotherapy, nanomedicine, and immunotherapy.
Prof. Paolo Decuzzi and his collaborators, in particular Daniele Di Mascolo and Anna Lisa Palange, will continue to develop the microMESH by integrating different types of drugs and therapies to tackle other types of tumors. In the short term, their major objective will be to validate the technology on glioblastoma patients.
Reference: Di Mascolo, D., Palange, A.L., Primavera, R. et al. Conformable hierarchically engineered polymeric micromeshes enabling combinatorial therapies in brain tumours. Nat. Nanotechnol. (2021). https://doi.org/10.1038/s41565-021-00879-3
Study indicates timing of chemotherapy could improve treatment for deadly brain cancer
An aggressive type of brain cancer, glioblastoma has no cure. Patients survive an average of 15 months after diagnosis, with fewer than 10% of patients surviving longer than five years. While researchers are investigating potential new therapies via ongoing clinical trials, a new study from Washington University in St. Louis suggests that a minor adjustment to the current standard treatment — giving chemotherapy in the morning rather than the evening — could add a few months to patients’ survival.
Average overall survival for all patients in the study was about 15 months after diagnosis. Those receiving the chemotherapy drug temozolomide in the morning had an average overall survival of about 17 months post diagnosis, compared with an average overall survival of about 13½ months for those taking the drug in the evening, a statistically significant difference of about 3½ months.
“We are working hard to develop better treatments for this deadly cancer, but even so, the best we can do right now is prolong survival and try to preserve quality of life for our patients,” said co-senior author and neuro-oncologist Jian L. Campian, MD, PhD, an associate professor of medicine at the School of Medicine. “These results are exciting because they suggest we can extend survival simply by giving our standard chemotherapy in the morning.”
Co-senior authors Joshua B. Rubin, MD, PhD, a professor of pediatrics and of neuroscience at the School of Medicine, and Erik D. Herzog, PhD, the Viktor Hamburger Distinguished Professor and a professor of biology in Arts & Sciences, developed a collaboration to study circadian rhythms and their effect on glioblastoma. Rubin and Herzog published studies in which they analyzed mouse models of glioblastoma and found improved effectiveness for temozolomide when given in the morning.
“In my lab, we were studying daily rhythms in astrocytes, a cell type found in the healthy brain,” Herzog said. “We discovered some cellular events in healthy cells varied with time of day. Working with Dr. Rubin, we asked if glioblastoma cells also have daily rhythms. And if so, does this make them more sensitive to treatment at certain times? Very few clinical trials consider time of day even though they target a biological process that varies with time of day and with a drug that is rapidly cleared from the body. We will need clinical trials to verify this effect, but evidence so far suggests that the standard-of-care treatment for glioblastoma over the past 20 years could be improved simply by asking patients to take the approved drug in the morning.”
In the current study, the researchers — led by co-first authors Anna R. Damato, a graduate student in neuroscience in the Division of Biology & Biomedical Sciences, and Jingqin (Rosy) Luo, PhD, an associate professor of surgery in the Division of Public Health Sciences and co-director of Siteman Cancer Center Biostatistics Shared Resource — also observed that among a subset of patients with what are called MGMT methylated tumors, the improved survival with morning chemotherapy was more pronounced. Patients with this tumor type tend to respond better to temozolomide in general. For the 56 patients with MGMT methylated tumors, average overall survival was about 25½ months for those taking the drug in the morning and about 19½ months for those taking it in the evening, a difference of about six months, which was statistically significant.
“The six-month difference was quite impressive,” Campian said. “Temozolomide was approved to treat glioblastoma in 2005 based on a 10-week improvement in survival. So, any improvement in survival beyond two months is quite meaningful.”
In this retrospective study, the researchers analyzed data from 166 patients with glioblastoma who were treated at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine between January 2010 and December 2018. All patients received the standard of care for glioblastoma. They underwent surgery to remove as much of each tumor as possible and then received radiation therapy along with the chemotherapy drug temozolomide. After the radiation and temozolomide regimen was complete, patients continued taking a maintenance dose of temozolomide — taken as an oral capsule — either in the morning or evening, depending on the preference of their oncologists.
“Until now, we have never considered that the timing of temozolomide might be important, so it’s up to the treating physician to advise the patient on when to take it,” said Campian, who treats patients at the Brain Tumor Center at Siteman. “Many oncologists give it in the evening because patients tend to report fewer side effects then. We saw that in our study as well. But it could be that the increased side effects — which we can manage with other therapies — are a sign that the drug is working more effectively.”
Added Damato: “There have been screens of different drugs given to cells at different times of day, and huge percentages of these drugs are shown to have time-of-day dependent effects on cell survival. For example, how the drug is absorbed might change throughout the day. So, side effects could change throughout the day.”
Campian cautioned that this was a relatively small retrospective analysis. She and her colleagues are conducting a clinical trial in which newly diagnosed glioblastoma patients are randomly assigned to receive temozolomide in either the morning or evening. Such trials will be needed to establish whether treatment timing can truly improve survival for glioblastoma patients.
“There have been no new drugs approved for glioblastoma in over a decade,” Luo said. “That makes it necessary to think about other possible changes that make a drug more efficacious. Chronotherapy — or the timed delivery of drugs, based on circadian rhythms — is becoming a popular topic. It’s practical and realizable to implement chronotherapy to optimize existing drugs and treatments.”
Campian, Rubin, Herzog and Luo also are research members of Siteman Cancer Center.
This work was supported by the Alvin J. Siteman Cancer Center Siteman Investment Program through funding from The Foundation for Barnes-Jewish Hospital and the Barnard Trust; The Children’s Discovery Institute; and the National Cancer Institute (NCI) of the National Institutes of Health (NIH), grant numbers P30CA091842 and F31CA250161.
About Washington University School of Medicine: Washington University School of Medicine’s 1,500 faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s hospitals. The School of Medicine is a leader in medical research, teaching and patient care, consistently ranking among the top medical schools in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.
Inhibiting a key enzyme that controls a large network of proteins important in cell division and growth, paves the way for a new class of drugs that could stop glioblastoma, a deadly brain cancer, from growing.
Researchers at Princess Margaret Cancer Centre, the Hospital for Sick Children (SickKids) and University of Toronto (U of T), showed that chemically inhibiting the enzyme PRMT5 can suppress the growth of glioblastoma cells.
The inhibition of PRMT5 led to cell senescence, similar to what happens to cells during aging when cells lose the ability to divide and grow. Cellular senescence can also be a powerful tumour suppression mechanism, stopping the unrelenting division of cancer cells.
The results of the study are published in Nature Communications on February 12, by lead author, former Postdoctoral Fellow Dr. Patty Sachamitr, SickKids and U of T, and senior authors, Drs. Panagiotis Prinos, Senior Research Associate, Structural Genomics Consortium, U of T, Senior Scientist Cheryl Arrowsmith, the Princess Margaret, and Senior Scientist and Neurosurgeon Peter Dirks, SickKids.
The researchers are part of the Stand Up To Cancer Canada Dream Team that focuses on brain tumours that have the worst outcomes, such as glioblastomas. By combining wide and deep expertise in research, clinical strengths, and unique partnerships, the researchers hope to accelerate new cures for some of the hardest-to-treat cancers.
Currently, the prognosis for glioblastoma remains very poor, with fewer than 10 per cent of patients surviving beyond five years. Current therapies are severely limited.
While PRMT5 inhibition has been suggested previously 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.
“We used a different strategy to stop cancer cells from proliferating and seeding new tumours,” says Dr. Arrowsmith, who also leads the U of T site of the International Structural Genomics Consortium, a public-private partnership with labs around the world, accelerating the discovery of new medicines through open science.
“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 Dr. Dirks, who led the pan-Canadian 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 poor outcome of glioblastoma could be attributed, at least in part, to the presence of tumour-initiating cancer stem cells, which have been shown by the Dirks laboratory to drive tumour growth and resistance to therapy. Novel therapeutic strategies are urgently needed to target these cancer stem cells, in addition to bulk tumour cells.
In this study, researchers tested a group of new experimental small molecules designed to specifically inhibit key cellular enzymes being developed and studied by the Structural Genomics Consortium to see if any would stop the growth of glioblastoma brain tumour cells in the laboratory. The brain tumour cells were isolated from patients’ tumours and grown in the laboratory in a way that preserved the unique properties of cancer stem cells.
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.
But they also caution that actual treatments for patients are many years away, and require development and testing of clinically appropriate and safe versions of PRMT5 inhibitors that can access the brain.
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.
“Right now, we have too few medicines to choose from to make precision medicine a reality for many patients,” says Dr. 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.”
Research was supported by the Stand Up To Cancer Canada Cancer Stem Cell Dream Team: Targeting Brain Tumour Stem Cell Epigenetic and Molecular Networks, Genome Canada, the Canadian Institutes of Health Research, the Ontario Institute for Cancer Research, Princess Margaret Cancer Foundation, Hopeful Minds Foundation, the Structural Genomics Consortium, and SickKids Foundation.
Princess Margaret Cancer Centre has achieved an international reputation as a global leader in the fight against cancer and delivering personalized cancer medicine. The Princess Margaret, one of the top five international cancer research centres, is a member of the University Health Network, which also includes Toronto General Hospital, Toronto Western Hospital, Toronto Rehabilitation Institute and the Michener Institute for Education at UHN. All are research hospitals affiliated with the University of Toronto. For more information: www.theprincessmargaret.ca
About The Hospital for Sick Children (SickKids)
The Hospital for Sick Children (SickKids) is recognized as one of the world’s foremost paediatric health-care institutions and is Canada’s leading centre dedicated to advancing children’s health through the integration of patient care, research and education. Founded in 1875 and affiliated with the University of Toronto, SickKids is one of Canada’s most research-intensive hospitals and has generated discoveries that have helped children globally. Its mission is to provide the best in complex and specialized family-centred care; pioneer scientific and clinical advancements; share expertise; foster an academic environment that nurtures health-care professionals; and champion an accessible, comprehensive and sustainable child health system. SickKids is a founding member of Kids Health Alliance, a network of partners working to create a high quality, consistent and coordinated approach to paediatric health care that is centred around children, youth and their families. SickKids is proud of its vision for Healthier Children. A Better World.
About University of Toronto
Founded in 1827, the University of Toronto has evolved into Canada’s leading institution of learning, discovery and knowledge creation. We are proud to be one of the world’s top research-intensive universities, driven to invent and innovate. Our students have the opportunity to learn from and work with preeminent thought leaders through our multidisciplinary network of teaching and research faculty, alumni and partners. The ideas, innovations and actions of more than 590,000 graduates continue to have a positive impact on the world.
In a study of mice, researchers at the UCLA Jonsson Comprehensive Cancer Center have identified a new approach that combines an anti-psychotic drug, a statin used to lower high cholesterol levels, and radiation to improve the overall survival in mice with glioblastoma. Glioblastoma is one of the deadliest and most difficult-to-treat brain tumors. Researchers found the triple combination extended the median survival 4-fold compared to radiation alone.
Radiation therapy is part of the standard-of-care treatment regimen for glioblastoma, often helping prolong the survival of patients. However, survival times have not improved significantly over the past two decades and attempts to improve the efficacy of radiotherapy through the use of pharmaceuticals have been hampered by the normal tissue toxicity of the drugs and the inability to penetrate the blood-brain barrier.
UCLA researchers previously reported that the first-generation dopamine receptor antagonist trifluoperazine in combination with radiation prolonged survival in mouse models of glioblastoma, but ultimately, the mice become resistant to the therapy. To help overcome this resistance, the team used quetiapine, a second-generation dopamine receptor antagonist, which not only enhanced the efficacy of radiotherapy in glioblastoma but also generated a metabolic vulnerability in the lipid homeostasis. The discovery that the combination induced the cholesterol biosynthesis pathway allowed the team to target this process with statins.
The team tested the approach using patient-derived glioblastoma lines provided by the Biospecimen and Pathology Core of the UCLA SPORE in Brain Cancer. Quetiapine was identified in a screen of dopamine receptor antagonists for their ability to prevent phenotype conversion of non-tumorigenic glioblastoma cells into radiation-induced glioma initiating cells. Atorvastatin (Lipitor) was selected because of its known ability to cross the blood-brain-barrier.
While radiation alone prolongs survival of glioblastoma to some extent, attempts to enhance the treatment have not been successful. The results of the study provide evidence that using a dopamine receptor antagonist in combination with Atorvastatin and radiation may help extend the survival for people with glioblastoma. The combination therapy also includes FDA-approved drugs that can rapidly be translated into a clinical trial.
The senior author Dr. Frank Pajonk, is a professor of Radiation Oncology at the David Geffen School of Medicine at UCLA and a member of the Jonsson Cancer Center. The lead author is Dr. Kruttika Bhat, a project scientist in Pajonk’s laboratory. Other authors are Mohammad Saki, Fei Cheng, Ling He, Dr. Le Zhang, Angeliki Ioannidis, David Nathanson, Jonathan Tsang, Steven Bensinger, Dr. Phioang Leia Nghiemphu, Dr. Timothy Cloughesy, Dr. Linda Liau and Dr. Harley Kornblum, all of UCLA.
The work was funded in part by the National Cancer Institute and the National Institutes of Health’s Brain Specialized Programs of Research Excellence, or SPORE, at UCLA, which helps advance work in the prevention, detection and treatment of brain tumors.
Reference: Kruttika Bhat, Ph.D, Mohammad Saki, Ph.D, Fei Cheng, Ph.D, Ling He, DDS, Ph.D, Le Zhang, MD, Ph.D, Angeliki Ioannidis, David Nathanson, Ph.D, Jonathan Tsang, 2, Steven J Bensinger, V.M.D., Ph.D, Phioanh Leia Nghiemphu, MD, Timothy F Cloughesy, MD, Linda M Liau, MD, Ph.D, Harley I Kornblum, MD, Ph.D, Frank Pajonk, MD, Ph.D, Dopamine Receptor Antagonists, Radiation, and Cholesterol Biosynthesis in Mouse Models of Glioblastoma, JNCI: Journal of the National Cancer Institute, 2021;, djab018, https://doi.org/10.1093/jnci/djab018
A look at RNA tells us what our genes are telling our cells to do, and scientists say looking directly at the RNA of brain tumor cells appears to provide objective, efficient evidence to better classify a tumor and the most effective treatments.
Gliomas are the most common brain tumor type in adults, they have a wide range of possible outcomes and three subtypes, from the generally more treatable astrocytomas and oligodendrogliomas to the typically more lethal glioblastomas.
Medical College of Georgia scientists report in the journal Scientific Reports that their method, which produces what is termed a transcriptomic profile of the tumor is particularly adept at recognizing some of the most serious of these tumors, says Paul M.H. Tran, MD/PhD student.
Gliomas are currently classified through histology, primarily the shape, or morphology, pathologists see when they look at the cancerous cells under a microscope, as well as identification of known cancer-causing gene mutations present.
“We are adding a third method,” says Dr. Jin-Xiong She, director of the MCG Center for Biotechnology and Genomic Medicine, Georgia Research Alliance Eminent Scholar in Genomic Medicine and the study’s corresponding author. Tran, who is doing his PhD work in She’s lab, is first author.
While most patients have both the current classification methods performed, there are sometimes inconsistent findings between the two groups, like traditional pathology finding a cancer is a glioblastoma when the mutation study did not and vice versa, and even when two pathologists look at the same brain tumor cells under a microscope, the scientists say.
To more directly look at what a cancer cell is up to, they opted to look at relatively unexplored gene expression, more specifically the one-step downstream RNA, which indicates where the cell is headed. DNA expression equals RNA since DNA makes RNA, which makes proteins, which determine cell function. One way cancer thrives is by altering gene expression, turning some up and others way down or off.
They suspected the new approach would provide additional insight about the tumor, continue to assess the efficacy of existing classification methods and likely identify new treatment targets.
“RNA would be a snapshot of what is high and what is low currently in those glial cells as they are taken out of the body,” Tran says. “They are actually looking at how many copies of RNA relevant genes are making. Normally that gene expression determines everything from your hair color to how much you weigh,” She says. “The transcriptomic profile counts the number of copies of each gene you have in the cell.”
The glial cells, whose job is to support neurons, have a tightly regulated gene expression that enables them to do just that. With cancer, one of the first things that happens is how many RNA copies of each gene the cells are making changes and the important cell function changes with it. “You change gene expression to become something different,” She says.
Transcriptomic profiling starts like the other methods with a tumor sample from the surgeon, but then it goes through an automated process to extract RNA, which is put into an instrument that can read gene expression levels for the different genes. The massive amounts of data generated then is fed into a machine learning algorithm Tran developed, which computes the most likely glioma subtype and a prognosis associated with it.
They started with The Cancer Genome Atlas (TCGA) program and the Repository of Molecular Brain Neoplasia Data (REMBRANDT), two datasets that had already done the work of looking at RNA and also provided related clinical information, including outcomes on more than 1,400 patients with gliomas. Tran, She and their colleagues used their algorithm to discover patterns of gene expression and used those patterns to classify all glioma patients without any other input. They then compared the three major glioma subtypes that emerged with standard classification methods.
Their transcriptomic classification had about 90% agreement with the traditional approach looking at cells under a microscope and about 93% agreement with looking at genetic mutations, She says. They found about a 16% discrepancy between the two standard measures.
“All three methods don’t agree on about 10-15% of patients,” She says, but notes the most accurate analysis among the three should be theirs because their method is better than the others at predicting survival.
And the discrepancies they found between classification methods could be significant for some patients despite close percentages.
“We found our method may have some advantages because we found some patients actually had a worse prognosis that could be identified by our method, but not by the other approaches,” Tran says.
As an example, patients with a mutation in a gene called IDH, or isocitrate dehydrogenase, most typically have an astrocytoma or oligodendroglioma, which are generally more responsive to treatment and have better survival rates than glioblastomas. However they also found that even some lower-grade gliomas with this IDH mutation can progress to what’s called a secondary glioblastoma, something which may not be found by the other two methods. The IDH mutation is rare in primary glioblastomas, Tran notes.
Using the standard techniques, which look at a snapshot in time, these astrocytomas that progress to more lethal glioblastomas were classified as a less serious tumor in 27 patients. “That progression phenomenon is known but our technique is better at identifying those cases,” Tran says.
Further analysis also found that about 20% of the worse-prognosis patients had mutations in the promoter region of the TERT gene. The TERT gene is best known for making telomerases, enzymes that enable our chromosomes to stay a healthy length, a length known to decrease with age. TERT function is known to be hijacked by cancer to enable the endless cell proliferation that is a cancer hallmark. This mutation is not usually present in a glioma that starts out as a more aggressive glioblastoma, and implicates a mutation in the TERT promoter is important in glioma progression, they say.
“The implication would be that if we have inhibitors or something else that target the TERT gene, then you may be able to prevent some of those cases from having a worse prognosis,” Tran says.
These findings also point to strengths of the different classification methods, in this case suggesting that classification by mutation may not pick up these most aggressive brain tumors rather their new transcriptomic method, as well as the older approach of looking at the cancer cells under a microscope, are better at making this important distinction.
“It is known that a certain proportion of your lower-grade gliomas can progress to become a glioblastoma and those are some of the ones that can sometimes be misidentified by the original techniques,” Tran says. “Using our gene expression method, we found them even though some of them have the IDH mutation.”
All these variations have groups like the World Health Organization asking for better ways to determine poor prognosis IDH patients, they write. Other variations include some glioblastomas with the normal IDH gene carry one of the worse prognoses for gliomas, but there is a subgroup of glioblastomas that act more like astrocytes and tend to carry a better prognosis.
Now that the MCG team has a better indication of which patients will have a worse prognosis, next steps including finding out why and maybe what can be done.
In addition to accuracy of prognosis, a second way to assess a tumor classification method is whether it points you toward better treatment options, She says, which they are now moving toward. He notes that most drugs and many of our actions, like exercise and what we eat, alter RNA expression.
“Right now, if anyone gives us RNA expression data from patients anywhere in the world, we can quickly tell them which glioma subtype it most likely is,” Tran says. The fact that equipment that can examine RNA expression is becoming more widely available, should make transcriptomic profiling more widely available, they say.
Gliomas are tumors of glial cells — which include astrocytes, oligodendrocytes and microglial cells — brain cells which outnumber neurons and whose normal job is to surround and support neurons.
Identification of IDH gene mutations in the cells has already made standard glioma classification more systematic, the scientists say. The mutation can be identified by either staining the biopsy slide or by sequencing for it.
Much progress also has been made in using machine learning to automate and objectify cancer diagnosis and subtyping they write, including glioblastomas. Glioblastomas have been characterized using transcriptome-based analysis but not all gliomas, like the current study.
Like most genes, the IDH gene normally has many jobs in the body, including processing glucose and other metabolites for a variety of cell types. But when mutated, it can become destructive to cells, producing factors like reactive oxygen species, which damage the DNA and contribute to cancer and other diseases. These mutations can result with age and/or environmental exposures. IDH inhibitors are in clinical trials for a variety of cancers including gliomas.
Increasing insight also is emerging into the significant DNA methylation that occurs in cancer, which alters gene expression, resulting in changes like silencing tumor suppressor genes and producing additional cancer-causing genetic mutations.