Glioblastoma (GBM) is a malignant brain tumor with nearly universal recurrence. GBM cancer stem cells (CSCs), a subpopulation of radio- and chemo-resistant cancer cells capable of self-renewal, contribute to the high rate of recurrence. The anti-cancer agent, CBL0137, inhibits the FACT (facilitates chromatin transcription) complex leading to cancer cell specific cytotoxicity. Here, we show that CBL0137 sensitized GBM CSCs to radiotherapy using both in vitro and in vivo models. Treatment of CBL0137 combined with radiotherapy led to increased DNA damage in GBM patient specimens and failure to resolve the damage led to decreased cell viability. Using clonogenic assays, we confirmed that CBL0137 radiosensitized the CSCs. To validate that combination therapy impacted CSCs, we used an in vivo subcutaneous model and showed a decrease in the frequency of cancer stem cells present in tumors as well as decreased tumor volume. Using an orthotopic model of GBM, we confirmed that treatment with CBL0137 followed by radiotherapy led to significantly increased survival compared to either treatment alone. Radiotherapy remains a critical component of patient care for GBM, even though there exists a resistant subpopulation. Radio-sensitizing agents, including CBL0137, pose an exciting treatment paradigm to increase the efficacy of irradiation, especially by inclusively targeting CSCs.
Glioblastoma (GBM) has a particularly high rate of recurrence with a 5-year overall survival rate of approximately 5%. This is in part due to a sub-population of cancer stem cells (CSC), which are both radioresistant and chemotherapeutically resistant to conventional treatments. Here we investigated CBL0137, a small molecule form of curaxin, in combination with radiotherapy as a means to radiosensitize CSCs. CBL0137 sequesters FACT (facilitates chromatin transcription) complex to chromatin, which leads to activation of p53 and inhibition of NF-κB. This sequestering of FACT results in cytotoxicity especially within tumor cells and prevents FACT from performing its primary role as a histone chaperone, as well as inhibits its part in the DNA damage response pathway. We show that when combined with radiotherapy, CBL0137 administration limited the ability of CSCs to identify and repair damaged DNA. CSCs treated in vitro with CBL0137 and irradiation showed an increased inhibition of cancer cell growth and decreased viability compared to irradiation or drug alone. Combination therapy also showed more DNA damage in the CSCs than with either agent alone. Based on our in vitro evidence for the efficacy of combination therapy to target CSCs, we moved forward to test the treatment in vivo. Using a subcutaneous model, we show that the amount of CD133+ cells (a marker for GMB CSCs) was reduced in irradiation plus CBL0137 compared to either treatment alone. Survival studies demonstrated that irradiation plus CBL0137 compared to irradiation alone or CBL0137 alone increase lifespan. Here we show the ability of CBL0137, in combination with irradiation, to target patient GBM CSCs both in vitro and in vivo. This work establishes a new treatment paradigm for GBM that inclusively targets CSCs and may ultimately reduce tumor recurrence.
INTRODUCTION:Pre-clinical interventions to the CNS require direct cranial administration of drugs for relevant therapeutic concentrations since the efficacy of systemic administration is hindered by the blood-brain barrier (BBB). We used MR-guided Focused Ultrasound (MRgFUS) to deliver primary-patient derived mesenchymal stem cells (hMSCs) for the first time, with sub-millimeter precision, in preselected areas. This method is a revolutionary way to deliver cellular therapy to delicate or inoperable regions obviating the need for invasive surgical intervention. METHOD: MRgFUS mediates BBB opening when low intensity FUS is applied to brain vasculature containing circulating microbubbles. This causes high intensity oscillation leading to a pore formation in BBB. hMSCs were injected intracardially in mice as a proof-of-principal delivery system. Under guidance of MRI, 0.4-1MPa in situpressures at 1 MHz, 1ms bursts and 1Hz pulse repetition frequency for 120 seconds were administered on the left hemisphere. Each animal's contralateral brain served as its own control RESULTS: We demonstrate that MRgFUS augments permeability of BBB. Each animal (n=3) received 3 cavitation parameters ranging from .4-1MPa in situ pressures at time points 2, 6 and 24hrs. Immunohistochemistry identified hMSC localization on sonicated points. Further analysis showed blood cell extravasation and capillary damage due to higher pressures and increased shear force from microbubble stream. The consequence is a cavitation pore larger than intended, necessitating further optimization. There were no observed behavioral complications after sonication and no hMSCs localization in non-pulsed regions demonstrating precise localization and no off-target delivery. CONCLUSION: The global hurdle of systemic therapy due to the BBB makes access of cellular therapy to the brain parenchyma, nearly impossible. This study investigates for the first time the utility of FUS to non-destructively permeabilize the BBB by creating a transient pore big enough for hMSC access.
Glioblastoma (GBM) is a fatal and incurable brain tumor, with an average life expectancy after diagnosis of only 12-15 months. A main reason for the lethality of GBM is inevitable recurrence, caused by a small population of the tumor cells, called cancer stem cells (CSCs). These cells are aggressive, infiltrative, and resistant to current GBM treatments of chemotherapy and radiotherapy. We use a small molecule drug, CBL0137, which inhibits the FACT (facilitates chromatin transcription) complex leading to cancer cell specific cytotoxicity. Here, we show that CBL0137 sensitized GBM CSCs to radiotherapy and hence lead to increased CSC death and prolonged survival in preclinical models. Clonogenic assays were used to show that CSCs were radiosensitized after CBL0137 treatment. We saw increased DNA damage when GBM CSCs were treated with CBL0137, as well as a decrease in foci resolution over time, when CBL0137 was combined with irradiation. In order to elucidate if the increase in DNA damage was directly due to the inhibition of the FACT complex, we depleted the level of FACT in our GBM CSCs. FACT depletion also led to increased DNA damage, and even more so when combined with irradiation. To validate whether combination therapy sensitized CSCs to radiotherapy in vivo, we used a subcutaneous mouse model and showed combination treatment decreased CSCs frequency in these tumors as well as decreased tumor volume. With an orthotopic model of GBM, we showed that CBL0137 treatment followed by radiotherapy significantly increased survival of mice bearing tumors over either treatment alone. Together, this work establishes a new treatment paradigm for GBM, which sensitizes radio-resistant GBM CSCs to irradiation, a critical component of patient care. Radio-sensitizing agents, including CBL0137, pose an exciting new therapeutic capable of increasing the efficacy of irradiation, by inclusively targeting CSCs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.