Researchers at the Perelman School of Medicine at the University of Pennsylvania have for the first time used lab-grown organoids created from tumors of individuals with glioblastoma (GBM) to accurately model a patient’s response to chimeric antigen receptor (CAR)-T cell therapy in real time. The researchers created organoids from the tumors of patients with recurrent glioblastoma who underwent surgery as part of a Phase I clinical trial for a dual-target CAR-T cell therapy. They then treated the glioblastoma organoids (GBOs) in parallel with patient therapy.
The study results confirmed that the organoid’s response to therapy mirrored the response of the actual tumor in the patient’s brain, so if the tumor-derived organoid shrank after treatment, so did the patient’s actual tumor.
“It’s hard to measure how a patient with GBM responds to treatment because we can’t regularly biopsy the brain, and it can be difficult to discern tumor growth from treatment-related inflammation on MRI imaging,” said Hongjun Song, PhD, the Perelman Professor of Neuroscience. “These organoids reflect what is happening in an individual’s brain with great accuracy, and we hope that they can be used in the future to ‘get to know’ each patient’s distinctly complicated tumor and quickly determine which therapies would be most effective for them for personalized medicine.”
Song is co-senior author of the team’s published paper in Cell Stem Cell, titled “Patient-derived glioblastoma organoids as real-time avatars for assessing responses to clinical CAR-T cell therapy,” in which the authors wrote, “To the best of our knowledge, this is the first clinical trial with a unique design to perform patient-matched organoid correlative studies in real time with patient treatment … These data provide a foundation for the future application of GBOs as avatars for testing treatment response in real time to stratify patients for clinical trials and to prioritize potential personalized treatment options.”
GBM is the most common, and most aggressive type of cancerous brain tumor in adults. Individuals with GBM usually can expect to live just 12–18 months following their diagnosis. Despite decades of research there is no known cure for GBM, and approved treatments such as surgery, radiation, and chemotherapy have limited effect in prolonging life expectancy.
“One of the reasons why GBM is so difficult to treat is because the tumors are incredibly complicated, made up of several different types of cancer cells, immune cells, blood vessels, and other tissue,” said study co-senior author, Guo-li Ming, MD, PhD, the Perelman Professor of Neuroscience and Associate Director of Institute for Regenerative Medicine.
CAR-T cell therapy reprograms a patient’s T cells to find and destroy a specific type of cancer cell in the body. While this therapy is FDA approved to fight several blood cancers, researchers have struggled to engineer cells to successfully seek out and kill solid tumors, such as GBM. Recent research suggests that CAR-T cell therapy that targets two brain tumor-associated proteins—rather than one—may be a promising strategy for reducing solid tumor growth in patients with recurrent glioblastoma.
The authors noted, “Immunotherapy, particularly CAR-T cell therapy targeting solid tumors like GBM, has encountered significant challenges due to tissue heterogeneity and a complex and immunosuppressive tumor microenvironment. Our ability to overcome these challenges has been limited by a lack of experimental models that faithfully replicate the in vivo microenvironment.”
Patient tumor-derived organoids are increasingly recognized as an important tool for cancer research, providing a more accurate and physiological representation of patient tumors compared with cell line or xenograft models, the author explained. However, they pointed out, “… while options for tumor organoid models exist, these organoids have not yet been used in the clinical setting in real time to aid with interpretation of treatment responses, particularly for central nervous system (CNS) tumors.” Rather, they commented, tumor organoids have been primarily used in retrospective studies, “… without direct application to temporally matched patient treatments.”
The first line of treatment for GBM is surgery to remove as much of the tumor as possible. For their newly reported study the researchers created organoids from the tumors of six patients with recurrent glioblastoma participating in a Phase I clinical trial for a dual-target CAR T cell therapy. And while it can take months to grow enough cancer cells in the lab on which to test treatments, an organoid can be generated in 2–3 weeks while the individuals recover from surgery and before they can begin CAR T cell therapy.
The team further pointed out, “Our previous detailed characterizations have shown that patient-derived GBOs ex vivo resemble many features of patient GBMs in vivo, including intertumoral heterogeneity, cell state diversity, landscape of the transcriptome and genomic mutations, and importantly, the tumor microenvironment.” Ming also noted, “By growing the organoid from tiny pieces of a patient’s actual tumor rather than one type of cancer cell, we can mirror how the tumor exists in the patient, as well as the ‘micro-environment’ in which it grows, a major limitation of other models of GBM.”
As part of the clinical trial patients received CAR-T cell therapy 2-4 weeks following their surgery. The CAR-T cell treatment was administered to the patients ‘organoids at the same time. “We designed a unique paradigm of a clinical trial with parallel treatment with autologous CAR-T cells in patients and in GBOs derived from the same patients ex vivo,” the investigators explained.
They found that the treatment response in the organoids correlated with the response of the tumors in the patient. When a patient’s organoid demonstrated cancer cell destruction by T cells, the patient also exhibited a reduced tumor size via MRI imaging and increased presence of CAR-positive T cells in their cerebrospinal fluid, indicating that the therapy met its targets.
A common concern with CAR T cell therapy for GBM is neurotoxicity, which occurs when a toxic substance alters the activity of the nervous system and can disrupt or kill brain cells. The researchers in addition found that there were similar levels of immune cytokines, which indicate toxicity, in both the organoids and the patients’ cerebrospinal fluid (CSF). Both levels decreased a week after treatment ended, suggesting that the organoid can also accurately model a patient’s risk of neurotoxicity, and help clinicians determine what size dose of CAR T to use.
“Our study showed exceptional correlation of various parameters, including the degree of temporally matched GBO cytolysis ex vivo and CAR-T cell engraftment in vivo, and the time course of cytokine release ex vivo and in patient CSF,” the authors wrote. “More importantly, our real-time analysis of GBOs ex vivo provides additional and critical insights into patient treatment responses.”
Co-senior study author Donald M. O’Rourke, MD, the John Templeton, Jr., MD, professor in neurosurgery and director of the Glioblastoma Translational Center of Excellence at the Abramson Cancer Center, stated, “This research shows that our GBM organoids are a powerful and accurate tool for understanding what exactly happens when we treat a brain tumor with CAR T cell therapy … Our hope is that not only to bring these to clinic to personalize patient treatment, but also to use the organoids to deepen our understanding of how to outsmart and destroy this complex and deadly cancer.”
In their paper the team concluded, “Together, our proof-of-principle study with a novel clinical trial design showed preliminary success in correlating ex vivo GBO responses with in vivo patient responses.” They suggest that their results could springboard future applications of GBOs for testing how patients will respond to treatments and help select the most appropriate personalized therapy, and to stratify patients for clinical trials. “For example, it may be possible in the future to select an optimal CAR-T cell therapy from a portfolio of options or select from several candidate drugs,” they noted. “Given the short survival period after diagnosis for GBM and rGBM patients, such an approach could be critical to move the needle in treating this devastating disease.”