Brain Cancer Archives | Alliance for Cancer Gene Therapy

Glioblastoma is the most common and aggressive type of primary brain tumor. Despite therapeutic advances over the past decade, the diagnosis of glioblastoma is associated with a median overall survival time of 8 months and a 5-year survival rate of less than 5%. Even if treatment with the current standard of care for glioma patients, which consists of surgery, temozolomide, and radiotherapy, is initially successful, nearly all malignant gliomas eventually recur. At the moment of recurrence, no treatment successfully cures the disease.

Naturally occurring or genetically modified viruses that selectively kill cancer cells are called oncolytic viruses.

In our laboratory, we have developed a platform of oncolytic viruses termed Delta-24. A new generation of this cancer-selective oncolytic adenovirus model, Delta-24-RGD, has arrived in the clinical arena and has been tested in patients with recurrent glioblastoma showing encouraging safety and efficacy results. Thus, 20% of patients treated with Delta-24-RGD as a single treatment survived more than 3 years after a single dose of this biological agent. Unfortunately, rapid clearance of the virus by the immune system prevents a response in a higher percentage of patients. In addition to other pre-clinical and clinical evidence, data from our clinical trial demonstrate that to improve the percentage of patients that respond to the therapy, we need to decrease the immune response against the virus, which in turn will increase the immune response against the tumor.

Therefore, this proposal aims to improve the response to virotherapy by attenuating the immune response against oncolytic adenovirus, with the goal of boosting the anti-tumor efficacy of this strategy. To this end, we propose two different strategies that can eventually be combined in a clinical trial. The first approach consists of making the virus less detectable by the immune system via substituting the most immunogenic viral protein with another viral protein for which the patients have not developed a pre-existing immune response. This new virus will persist longer in the tumor environment and thus maintain the window of opportunity to develop an anti-tumor immune response for a more prolonged time.

Our second approach involves the generation of tolerogenicity for the virus. To achieve this objective, we will target dendritic cells, which are in charge of the antigen presentation to the immune effector cells, using nano molecules to deliver viral antigens.

This strategy will diminish the response of the immune system against viral antigens, allowing the immune defenses to be focused on the tumor. If this highly innovative project is successful, we have the resources and infrastructure already in place to further translate these two strategies, as single approaches or in combination, to treat malignant brain tumors in the clinical scenario.

Children with diffuse midline gliomas (DMGs) – a type of brain cancer – continue to have a dismal prognosis, and most children die within one year of diagnosis. Recent studies have shown that the majority of these tumors carry a specific mutation referred to as H3.3K27M. Researchers have shown that this specific mutation is present in almost all DMG tumor cells but not in normal cells within the body, making this an attractive target for immunotherapy approaches that activate an immune response against the cancer cells. Immunotherapy has shown phenomenal improvements in the outcome of adults and children with specific types of cancers, such as melanoma and leukemia. However, we are just starting to implement such novel and promising approaches for DMGs in the clinic.

With this proposal, we will test the benefit of a specific immunotherapy approach referred to as adoptive T-cell transfer, which gives the patient a large number of killer T cells. More specifically, we will test an approach known as engineered T-cell receptor (TCR) therapy, in which killer T cells are engineered to be specific to a piece of protein on the surface of tumor cells.

We have been able to show in the laboratory that we can make T cells specifically recognizing DMG cells with the H3.3K27M – and that these specific T cells can kill tumor cells. Based on these exciting data, we propose to test this new therapy approach in the clinic. Participants who are newly diagnosed with an H3.3K27M DMG are eligible for this clinical trial. They will undergo collection of their own T cells, and these T cells will subsequently be engineered in the laboratory to recognize the specific H3.3K27M mutation. These modified T cells will then be given back to the participants once they have completed standard-of-care radiation therapy and a conditioning short chemotherapy course. We hypothesize that these modified T cells will now be able to kill the cancer cells carrying the specific H3.3K27M mutation.

Within this project, we will assess if such a therapy approach is feasible and safe. Precisely, we will test how many of these specifically modified T cells are able to be given back to participants without causing too many side effects. Further, we will perform specific tests from blood samples from trial participants to assess how long these modified T cells survive. To better understand responses, we will use advanced molecular technologies to assess the blood of participants. This information will help us to improve our ability to assign patients to the right therapies and make even more effective tumor-targeting T cells in the future.

This project has the potential to significantly impact the treatment approach for a disease for which we have not achieved any improvement for the last several decades and is the first of its kind for this devastating disease.

Malignant brain tumors carry a dismal prognosis despite surgery, chemotherapy, and radiation, hence new therapeutic approaches are needed. New strategies are being investigated using modified viruses (termed “vectors”) to infect cancer cells and deliver genes that serve as blueprints to make therapeutic proteins inside the cancer cells themselves.

Until recently, most researchers used viral vectors that could deliver therapeutic genes to the initially infected tumor cells but are rendered incapable of infecting any additional cells. However, such ‘non-replicating’ vectors were found to have limited benefit, because not enough tumor cells could be reached.

A newer approach is to use virus vectors that actively replicate themselves and can spread forth from the initially infected cancer cells within tumors, but not in normal tissues, thereby continuing to infect more cancer cells even as the cells continue to proliferate. These tumor-selectively spreading viruses are used to deliver a “suicide gene,” which converts a non-toxic ‘trigger’ compound (“prodrug”) into a DNA synthesis-blocking chemotherapy drug. Because this virus causes the chemotherapy drug to be generated selectively and directly within the infected tumor itself, there are few adverse side effects.

The first version of this type of therapeutic virus has shown highly promising results in early-stage clinical trials and is currently being tested in an international Phase 2B/3 trial for recurrent brain cancer.

We recently discovered that this approach can also activate the immune system to attack tumors. Hence, in this Alliance for Cancer Gene Therapy funded study, we examine whether brain tumors that show a high rate of new mutations, which can be recognized by the immune system, may be correlated with better responses to this treatment.

We also propose to develop a new tumor-selectively spreading virus vector that delivers a different “suicide gene” which cross-links DNA and thereby generates new mutations for the immune system to attack, and we further propose to combine this mutagenic DNA cross-linking suicide gene therapy with strategies to overcome immune blockade (“checkpoint”) mechanisms within tumors.

Finally, we will conduct preclinical studies to evaluate the safety of this new virus vector for use in a future clinical trial. If the proposed preclinical studies are successful in validating the safety, efficacy, and mechanism of action for this new immunogenic suicide gene therapy, combined with immune checkpoint inhibition, we anticipate that this approach can be rapidly translated to the clinic in collaboration with a biotech partner that is already testing our previously developed virus vector in clinical trials.

This Alliance for Cancer Gene Therapy Research Fellow is funded in part by Swim Across America.

Glioblastoma (GBM) is the most common malignant brain tumor in adults. It is incurable, with average patient survival of about 13 months even with an aggressive therapeutic regimen consisting of maximal tumor resection, and concomitant chemotherapy and radiotherapy. One of the reasons for therapeutic failure is the complex functional heterogeneity in this brain tumor. In fact, not all cells are functionally identical in GBM, but a small population has properties reminiscent of normal stem cells, whereby they are uniquely responsible for tumor growth and recurrence. We call these specialized cells “cancer stem cells,” or tumor-initiating cells.

Whereas current treatments are relatively successful at targeting the other cells in this tumor, cancer stem cells have ways of evading current therapeutic intervention. We have recently shown that one feature that distinguishes cancer stem cells from the other cells in GBM is the way DNA is packaged. Cancer stem cells have regions of highly compacted DNA, which is caused by low levels of a protein that binds the DNA and relaxes its architecture.

We have designed a protein that can change DNA architecture and can be directed by us to any site in the human genome. We will use this engineered protein to unravel the DNA structure that is specifically found in the cancer stem cells of GBM patients.

We will provide proof-of-principle that altering DNA architecture is an effective way of targeting cancer stem cells. We will do so by testing the efficacy of our approach in a collection of patient-derived cancer stem cell cultures. We will then test the pre-clinical implication of our findings by transplanting GBM cancer stem cells in mice and treat their resultant “human” tumors with our engineered protein. We will then assess the effects of our treatment on tumor growth and recurrence. Essentially, our technology will enable us to perform a new kind of gene therapy by directly targeting DNA structure which is the ultimate determinant of cancer stem cell behavior.

Effective brain cancer therapies remain a critically unmet need in human healthcare. Advances in surgical, radiation and chemotherapeutic treatments have done little to change patients’ outcomes in the past 30 years. Clearly, new approaches are needed if we are to control these diseases. Many groups worldwide have been exploring the use of viruses that can selectively replicate in and kill tumor cells without harming normal cells; these so called “Oncolytic Viruses” (OV) have shown some remarkable results in late-stage clinical trials.

Despite this clinical success most OVs are inherently neurotoxic and are not safe to use with brain cancer. Recently we have discovered a new OV variant (a Chimeric Maraba virus) that is non-neurotoxic when injected directly into the brain of mice and that is also effective in a rodent model of brain cancer in vivo and human glioblastoma tumor cells in vitro.

A current impediment to further clinical development of this virus therapy is the manufacturing capability to supply this virus at a scale and quality suitable for requisite small rodent and non-human primate safety/toxicity studies, and to provide the eventual clinical stock that will be used in our upcoming phase I clinical trial.

This Alliance for Cancer Gene Therapy funded grant will aid in the design and validation of a GMP-manufacturing process for this virus, and will provide the resources necessary to generate, characterize and validate the virus lots needed to supply the in vivo toxicity studies in support of our clinical trial application, and to conduct our clinical trial.

Brain cancer continues to be an unmet clinical need requiring novel treatments that are not merely palliative (surgery, radiation and chemotherapy) but potentially curative. A potent OV that can safely target the brain can potentially treat primary, metastatic and recurrent brain cancer improving quality of life and extending survival rates for patients suffering from this deadly disease.  

This Alliance for Cancer Gene Therapy Research Fellow is funded in part by Swim Across America.

Malignant brain cancers rank fourth in cancer deaths in the US and are second only to leukemia in children. Despite significant advances in neurosurgical techniques, radiation oncology, and numerous clinical trials, high-grade brain tumors, in particular Glioblastoma (GBM), remain incurable diseases. Understanding the molecular basis of the therapy refractoriness of GBM is one of the most important areas of glioma research.

In this proposal, we will define the role of a novel glioma oncoprotein, termed isocitrate dehydrogenase-1 (IDH1), in driving progression and therapy resistance of GBM. IDH1 is a critical enzyme of the citric acid cycle (CAC). The CAC is a master regulator of metabolism that controls cellular energy production, lipid biosynthesis and cytoprotective guard mechanisms counteracting therapy-induced tumor cell death. Building on our preliminary studies documenting robust overexpression of IDH1 in human GBM tumor specimens, and high-level induction of IDH1 by anti-glioma therapies, we will molecularly characterize the precise mechanism, by which IDH1 protects glioma cells from therapy-induced cell death using glioma cell and mouse models. To target IDH1 signaling in GBM, we will leverage these model systems and mechanistical knowledge to develop and preclinically characterize RNA interference RNAi-based nanomaterials. Here, we will generate RNAi-functionalized spherical nucleic acids (SNAs) that neutralize IDH1 expression in established gliomas. RNAi, the biological mechanism by which double-stranded RNA induces gene silencing by targeting complementary mRNA for degradation, was awarded a Nobel Prize in 2006. Early studies indicated that RNAi has the potential to silence expression of various cancer genes implicated in growth and cell death, and consequently has motivated myriad preclinical studies to assess the potential of RNAi as anti-cancer therapeutics. Due to the negative charge of the RNA backbone, however, siRNA oligonucleotides do not penetrate negatively charged membranes effectively, cannot silence gene expression robustly and persistently in tissue in vivo, exhibit rapid renal and hepatic clearance and degradation by nucleases, have significant cytotoxic side effects, trigger auto-immune responses, and cannot cross the blood-brain-barrier (BBB). In contrast, SNAs are able to transverse cellular membranes, do not require the use of toxic auxiliary reagents, and accumulate in cells and intracranial tumors very effectively. They also exhibit extraordinary stability in physiological environments, cross the BBB, are highly resistant to nuclease degradation, and thus, can move through biological fluids and avoid being destroyed as “foreign materials.” We propose to preclinically evaluate these IDH1-tageting nanoconjugates to provide a fundamentally novel treatment option of patients diagnosed with GBM and will aid in successfully implementing RNAi-based therapies into neuro-oncological practice.

Vaccine-strain measles virus is a promising platform for the development of genetically programmable anti-cancer therapies. Measles vaccine virus has a natural preference for binding and infecting many types of tumor cells. With an impeccable safety record from decades of clinical use, the measles vaccine virus has already entered clinical trials for several cancers.

Recently, genetic modifications to the measles vaccine virus that enhance its ability to replicate in cells have shown further improvements in tumor killing in preclinical testing. As this therapeutic virus platform is modified to be more lethal to cancer cells, however, it becomes important to be able to limit its replication to particular times and places in order retain its low toxicity to normal cells.

We propose to develop two mechanisms for improving measles vaccine virus control and specificity. The first mechanism allows administration of an orally available nontoxic drug to rapidly shut off virus protein production. The second mechanism renders virus protein production dependent on a specific molecular abnormality commonly found in cancer cells. Both will be based on encoding in the virus genome rationally engineered protein switches to control the function of viral replication proteins. In preliminary work, we have successfully created prototypical control elements for both mechanisms.

We propose to test the ability of these control elements to function in the context of the whole virus in order to control replication in time and by tumor type. If successful, the proposed work will establish a generalizable method by which replication of measles vaccine virus, and other RNA-based viruses, can be programmed for increased tumor specificity and safety.

Malignant glioblastomas have virtually defied all therapeutic modalities to date. Successful therapies will need novel strategies targeting the underlying pathogenesis which may ultimately offer an innovative approach for glioblastoma patients.

This proposal aims at using neural stem cells to deliver therapeutic drugs that can stop tumor cells to proliferate and simultaneously kill them while leaving the normal brain cells intact. This will be combined with novel in vivo imaging methods that will allow us to monitor the location and size of tumors and track the migration of neural stem cell delivery vehicles in experimental animal models.

There are four basic components of the proposed therapeutic system.

First, the “shell” of a virus, will be used to efficiently carry therapeutic and imaging genes into cells.
Second, neural stem cells will be employed as delivery vehicles as they have been found to home to tumor cells in the brain and can change themselves into normal cells of the nervous system.
Third, engineered apoptotic and anti-proliferative proteins that are released at the tumor destination by the delivery cells will be employed which will stop tumor cells to divide and selectively kill them while leaving the normal brain cells intact.
Fourth, fluorescent and bioluminescent markers will be incorporated into tumor cells and delivery cells such that we can monitor their fate in the brains in real time.

Although these studies are experimental, we can envision a therapeutic modality in which the main tumor mass in the brains of patients will be removed at the time of surgery and therapeutic neural stem cells will be introduced near the remaining tumor cells thus eliminating the risk of recurrence. This will have a major impact in developing more efficient means of eradicating gliomas and saving the lives of many brain cancer patients.

This Alliance for Cancer Gene Therapy Research Fellow is funded in part by Swim Across America.

Malignant gliomas are one of the most incurable forms of cancer, attacking the brains of children or adults and causing death, on average, by 1-2 years. We have been employing tumor-selective viruses that will specifically attack these cancers in the brain and will sensitize these cancers to the effect of chemotherapy by transferring the genes that activate such chemotherapy drugs.

The virus that we have tested in mice with brain tumors is named MGH2 and we now plan to perform preclinical toxicology studies requested by the FDA before proceeding to a human phase I clinical trial. A clinical trial in humans will involve injecting the brain tumor with MGH2 in combination with the two chemotherapy agents, cyclophosphamide and irinotecan, that are converted by the MGH2-transferred genes into the active anticancer agents. This multimodal viro- and gene-based therapy would thus provide the opportunity of attacking multiple vulnerabilities within the malignant brain tumor. 

Glioblastoma multiforme (GBM) represents the most common primary malignant tumor of the adult central nervous system. The median survival after surgical intervention alone is approximately six months and the addition of radio-/chemotherapy can extend this time up to fourteen months. Consequently, efforts aimed at developing new therapies have focused on treatment strategies that target the tumor environment but spare normal and healthy surrounding brain cells.

Oncolytic adenoviral therapy is a novel modality of anti-cancer treatment. Our group has created the oncolytic vector CRAd-Survivin-pk7 (CRAd-S-pk7) for the treatment of malignant gliomas. For transcriptional targeting in gliomas, we incorporated the survivin promoter upstream from viral gene E1A. The survivin promoter is highly active in gliomas but remains silent in the surrounding brain parenchyma. To enhance viral transduction into glioma cells, the capsid of this vector was modified to bind heparan sulfate proteoglycans expressed in these tumors.

In our extensive preclinical studies, CRAd-S-pk7 exhibits potent anti-tumoral activity in mice bearing intracranial human glioma xenografts, including the highly aggressive CD133+ glioma stem cell model. In addition, we have recently shown that this virus elicits a synergistic therapeutic effect when combined with low dose radiation and with the chemotherapeutic agent temozolomide, two therapies that constitute the standard of care for patients with malignant glioma.

Since one of the major limitations of virotherapy is poor spread following injection, we have recently shown that mesenchymal stem cells (MSC) can more effectively migrate and deliver an oncolytic adenovirus to intracranial glioma than local injection of the virus alone. This form of carrier mediated delivery leads to enhanced viral replication in the tumor and a much more potent anti-tumor response than local injection of the virus alone.

Moreover, our studies further suggest that MSC suppresses the anti-adenoviral immune response, further enhancing the efficacy of oncolytic virotherapy. In order to translate our work into the clinical setting, we now propose to develop a clinical trial in which this novel virus will be delivered via MSCs.

To achieve this goal, we would like to utilize Alliance for Cancer Gene Therapy funding to complete the following aims:

Aim 1: Validate the therapeutic efficacy of CRAd-S-pk7 loaded MSCs in vitro and in animal models of glioma.
Aim 2: Evaluate the therapeutic efficacy and safety monitoring with CRAd-S-pk7 loaded MSCs in the presence of temozolomide-based chemotherapy and radiotherapy.
Aim 3: Determine the migration, engraftment, and long-term fate of CRAd-S-pk7 loaded MSCs in vitro and in animal models of glioma with MRI.
Aim 4: Perform a toxicology/biodistribution study with MSC-loaded cGMP-grade clinical lot virus.
Aim 5: Conduct RAC and FDA meetings and assemble documents for filing an IND application for mesenchymal stem cell based.

The prognosis for brain tumor patients has not improved significantly despite many innovations in surgery and radiation therapy, and the introduction of many new drugs that work well for other types of cancer. There is an urgent need for new approaches to treat brain tumors. Here, we propose investigating a new approach to brain tumor therapy based on the genetic modification of normal brain cells to create an environment that prevents tumor growth.

Adeno-associated virus (AAV) vectors will be used as they are very efficient in introducing genes into normal brain cells. These AAV vectors will be used to introduce in normal brain cells or blood vessels a gene that makes a protein which can be released from modified normal cells and that is selectively active against tumor cells.

In these experiments we will investigate the efficiency of this therapy principle by modifying the brain surrounding the tumor by direct injection of AAV vectors into the brain or by modifying the blood vessels in the brain by injection of these vectors into the bloodstream. These approaches may lead to the creation of widespread anti-tumor networks capable of preventing brain tumors from growing or appearing again after surgery. 