Apoptosis In Medulloblastoma Cells Research Articles

Abstract 5114: Deciphering the implications of THOC7 in medulloblastoma: Unraveling its role in tumor growth and progression

Abstract Background: Medulloblastoma (MB) is the most common malignant brain cancer in children. Despite the progress made in treating MB, the 5-year survival rate for high-risk tumors remains poor and risk of recurrence within 2 years of treatment is still high. Unfortunately, patients who do survive have reduced quality of life because of the highly toxic side effects of radiation and chemotherapy. Those facts underline the importance of identifying new drivers of MB and understanding the mechanism by which those drivers may promote MB. Using CRISPR-based dependency analysis, we discovered THO Complex Subunit 7 Homolog (THOC7) as one of the highly differentially expressed genes that may uniquely provide survival advantage to MB cells. THOC7 is a component of the THO subcomplex of the TREX complex, which is known to couple mRNA transcription, processing and nuclear export associated with spliced mRNA. Methods: To understand the role of THOC7 in MB, we silenced the expression of THOC7 using siRNAs in multiple MB cell lines. The knockdown efficiency was confirmed by western blot and qPCR. The effect of THOC7 silencing on the viability of MB cells was assessed by short-term viability and long-term colony formation assays. The effect of THOC7 silencing on MB cell proliferation was measured using an IncuCyte. To assess whether THOC7 may affect MB progression, we performed Transwell migration assay. To understand the mechanism by which THOC7 may play a role in medulloblastomogenesis, we measured the effect of THOC7 silencing on the cell cycle progression and apoptosis. As presence of cancer stem cells is linked to relapse and makes MB refractory to radiation therapy, we asked whether THOC7 may support MB stem cell proliferation using neurosphere assay. Results: Our analysis revealed that MB is highly addicted to THOC7. Importantly, higher expression of THOC7 is strongly correlated with lower overall survival of MB patients. We showed that depletion of THOC7 inhibited the short- and long-term viability as well as proliferation of MB cells. In addition, silencing of THOC7 inhibited migration/invasion of MB cells. THOC7 depletion led to cell cycle arrest and increased apoptosis of MB cells. Furthermore, our neurosphere assay demonstrated that silencing of THOC7 blocked the MB stem cell proliferation. Conclusion: Our results suggest that THOC7 may be a novel driver of MB growth and progression. Inhibition of MB stem cell proliferation in THOC7 depleted cells indicates that THOC7 inhibition may sensitize refractory MB to radiation therapy. Experiments are currently underway to understand the mechanism by which THOC7 may support MB growth and progression. In conclusion, our results showing no effect of THOC7 silencing on normal cell viability suggest that approaches aimed at silencing THOC7 may be a safe and viable approach for treating MB. Citation Format: Shahad M. Abdulsahib, Santosh Timilsina, Saif Nirzhor, Daisy Medina, Prabhakar V. Pitta, Panneerdoss Subbarayalu, Manjeet K. Rao. Deciphering the implications of THOC7 in medulloblastoma: Unraveling its role in tumor growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5114.

Abstract 4599: A novel small molecule inhibitor targeting MYC oncogenic signaling as an enhancer of HDAC inhibitors for the treatment of high-risk medulloblastoma

Abstract Background: Medulloblastoma (MB) is the most prevalent malignant childhood brain tumour. Although prognosis has improved over time, 95% of children with high-risk or relapsed MB eventually succumb to the disease. A key driver gene in high-risk MB is the c-MYC oncogene, for which there are currently no approved inhibitors. Histone deacetylases (HDACs) are transcriptional repressors that are dysregulated in many cancers, making them an attractive therapeutic target. Although several HDAC inhibitors have been FDA-approved for cancer treatment, they have been associated with high toxicity and limited efficacy as single agents. Therefore, simultaneously targeting c-MYC and HDACs may result in synergistic effects that could overcome drug resistance in high-risk MB. Methods and Results: We previously reported a novel pyrido-benzimidazole analogue, SE486-11, which enhanced the therapeutic effect of HDAC inhibitors in MYCN-driven cancers. We recently developed analogues (UNSW-SC compounds) with more potent activity (IC50: 0.017 to 3.70 µM). Here, we showed that these compounds significantly reduced cell viability and induced apoptosis in MB cells. MYC status was a key determinant of sensitivity of UNSW-SC compounds, with more than 3-fold higher cytotoxicity in high MYC compared to low MYC MB cells. The lead compound, UNSW-SC-22, was shown to reduce MYC protein expression and was found to be highly synergistic in enhancing the efficacy of HDAC inhibitors in MB cells. Most importantly, we demonstrated that UNSW-SC-22 was able to freely cross the blood brain barrier, reaching a concentration of 10.8 μM, with a half-life of 1.22 hours. UNSW-SC-22 directly bound to c-MYC and MYCN proteins at low micromolar equilibrium dissociation constant (KD) values which was demonstrated by surface plasmon resonance assay. In a MYCN-driven MB mouse model, we found that UNSW-SC-22 as a single agent at 90 mg/kg decreased tumor growth and prolonged survival. Through RNA-sequencing, we identified 512 differentially expressed genes after in vitro treatment with UNSW-SC-22. Importantly, GSEA analysis revealed MYC targets and cell cycle pathways as highly downregulated pathways, and upregulation in the p53 pathway. Several genes, such as MELK and USP1 were validated as down-stream targets of UNSW-SC-22. As UNSW-SC-22 is a first-in-class anticancer drug, which we are currently testing extensively in other MYC-driven MB mice models. Conclusion: Collectively, our data strongly suggest that c-Myc and MYCN are the molecular targets of UNSW-SC compounds, and these compounds have strong potential to serve as specific targeted therapy to treat subgroup 3 and 4 of MB patients with c-Myc and MYCN overexpression and amplification. Citation Format: Sin Wi Ng, Satyanarayana Gadde, Qian Wang, Belamy B. Cheung, Glenn M. Marshall. A novel small molecule inhibitor targeting MYC oncogenic signaling as an enhancer of HDAC inhibitors for the treatment of high-risk medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4599.

Abstract 6735: Identifying the role of novel driver TREX subcomplex in medulloblastoma growth and progression

Abstract Background: Medulloblastoma (MB) is the most common malignant brain cancer in children. Despite the progress made in treating MB, the 5-year survival rate for high-risk tumors remains poor and risk of recurrence within 2 years of treatment is still high. Almost all MB deaths are attributed to leptomeningeal dissemination (LMD) as MB spreads exclusively through cerebrospinal fluid (CSF) to spinal and intracranial leptomeninges. Unfortunately, patients who do survive have reduced quality of life because of the highly toxic side effects of radiation and chemotherapy. Those facts underline the importance of identifying new drivers of medulloblastoma and understanding the mechanism by which those drivers may promote medulloblastoma. Towards that goal, I aim to identify novel drivers of MB and characterize novel therapies for treating (LMD-MB). Using an unbiased genome-wide screen, we discovered THO complex as one of the highly differentially expressed genes that may provide survival advantage to MB cells. THO is a subcomplex of the TREX complex, is known to couple mRNA transcription, processing and nuclear export associated with spliced mRNA. Methods: Recent work in our lab utilizing various genomes and proteomics identified THO complex as a possible target. Transfection agents were used to knockdown part of the TREX subcomplex expression in several MB cells. Western blot and qPCR verified the knockdown. The cell viability was measured using Cell Titer Glo, and cell proliferation was evaluated with an IncuCyte. Cells were seeded at a low density and cultured until colonies formed then were fixed and stained with crystal violet. In addition, cells were seeded in a serum-free medium and allowed to migrate to complete media before being fixed and stained. Flow cytometry was used to examine cells for apoptosis and cell cycle. For apoptosis, cells were stained with propidium iodide (PI) and Annexin FTIC, and for the cell cycle, cells were stained and followed by PI. Results: The Cancer Dependency Map (Dep-Map) meta-analysis revealed that MB strongly depends on The TREX subcomplex. Significantly, increased THO complex expression was associated with a worse overall survival rate in MB patients. Our findings indicated that part of the TREX subcomplex depletion decreased MB cell survival in the short- and long-term proliferation, migration, and invasion. Furthermore, part of TREX subcomplex depletion promoted apoptosis in MB cells. I propose that THO complex may be a new driver of MB and that strategies aiming to reduce part of TREX subcomplex levels and activity might benefit MB patients. Conclusion: TREX subcomplex parts depletion has been demonstrated to reduce MB cells in vitro in various experiments. Future research, including CRISPR-CAS9-based knockout models, single-cell sequencing, and metabolomics, will further elucidate the mechanism(s) and utility of the TREX subcomplex axis in LMD-MB. Citation Format: Shahad M. Abdulsahib, Santosh Timilsina, Manjeet Rao. Identifying the role of novel driver TREX subcomplex in medulloblastoma growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6735.

T-Type Calcium Channel Inhibitors Induce Apoptosis in Medulloblastoma Cells Associated with Altered Metabolic Activity

Medulloblastoma (MB) is the most common malignant paediatric brain tumour. In our previous studies, we developed a novel 3D assay for MB cells that was used to screen a panel of plasma membrane calcium channel modulators for their effect on the 3D growth of D341 MB cells. These studies identified T-type (CaV3) channel inhibitors, mibefradil and NNC-55–0396 (NNC) as selective inhibitors of MB cell growth. Mibefradil was originally approved for the treatment of hypertension and angina pectoris, and recently successfully completed a phase I trial for recurrent high-grade glioma. NNC is an analogue of mibefradil with multiple advantages compared to mibefradil that makes it attractive for potential future clinical trials. T-type channels have a unique low voltage-dependent activation/inactivation, and many studies suggest that they have a direct regulatory role in controlling Ca2+ signalling in non-excitable tissues, including cancers. In our previous study, we also identified overexpression of CaV3.2 gene in MB tissues compared to normal brain tissues. In this study, we aimed to characterise the effect of mibefradil and NNC on MB cells and elucidate their mechanism of action. This study demonstrates that the induction of toxicity in MB cells is selective to T-type but not to L-type Ca2+ channel inhibitors. Addition of CaV3 inhibitors to vincristine sensitised MB cells to this MB chemotherapeutic agent, suggesting an additive effect. Furthermore, CaV3 inhibitors induced cell death in MB cells via apoptosis. Supported by proteomics data and cellular assays, apoptotic cell death was associated with reduced mitochondrial membrane potential and reduced ATP levels, which suggests that both compounds alter the metabolism of MB cells. This study offers new insights into the action of mibefradil and NNC and will pave the way to test these molecules or their analogues in pre-clinical MB models alone and in combination with vincristine to assess their suitability as a potential MB therapy.

Icariin Regulates Cell Cycle Related Proteins and Apoptosis Related Proteins and Affects Cell Cycle and Apoptosis of Medulloblastoma Cells

Icariin Regulates Cell Cycle Related Proteins and Apoptosis Related Proteins and Affects Cell Cycle and Apoptosis of Medulloblastoma Cells

Retraction.

Retraction: "Effects of microRNA-494 on proliferation, migration, invasion, and apoptosis of medulloblastoma cells by mediating c-myc through the p38 MAPK signaling pathway," by Xiao-Heng Xu, Si-Jin Zhang, Qi-Bo Hu, Xing-Yu Song, Wei Pan, J Cell Biochem. 2019; 2594-2606: The above article, published online on 10 October 2018 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/abs/10.1002/jcb.27559), has been retracted by agreement between the journal's Editor in Chief, Prof. Dr. Christian Behl, and Wiley Periodicals LLC. The retraction has been agreed following an investigation based on allegations raised by a third party. Several flaws and inconsistencies between results presented and experimental methods described were found. Thus, the editors consider the conclusions of this article to be invalid.

STAT3 inhibitor in combination with irradiation significantly inhibits cell viability, cell migration, invasion and tumorsphere growth of human medulloblastoma cells

ABSTRACT Persistent activation of signal transducer and activator of transcription 3 (STAT3) is frequently reported in cancers and plays important roles in tumor progression. Therefore, directly targeting persistent STAT3 signaling is an attractive cancer therapeutic strategy. The aim of this study is to test the inhibitory efficacy of novel STAT3 small molecule inhibitors, LLY17 and LLL12B, in combination with irradiation in human medulloblastoma cells. Both LLY17 and LLL12B inhibit the IL-6-induced and persistent STAT3 phosphorylation in human medulloblastoma cells. Irradiation using 4 Gy alone exhibits some inhibitory effects on medulloblastoma cell viability, and these effects are further enhanced by combining with either STAT3 inhibitor. Irradiation alone also shows certain inhibitory effects on medulloblastoma cell migration and invasion and the combination of LLY17 or LLL12B with irradiation further demonstrates greater inhibitory effects than monotherapy. STAT3 inhibitor alone or irradiation alone exhibits some suppression of medulloblastoma tumorsphere growth, and the combination of LLY17 or LLL12B and irradiation exhibits greater suppression of tumorsphere growth than monotherapy. Combining either STAT3 inhibitor with irradiation reduces the expression of STAT3 downstream targets, Cyclin D1 and Survivin, and induces apoptosis in medulloblastoma cells. These results support that combination of a potent STAT3 inhibitor such as LLY17 or LLL12B with irradiation is an effective and novel therapeutic approach for medulloblastoma.

CircSKA3 Modulates FOXM1 to Facilitate Cell Proliferation, Migration, and Invasion While Confine Apoptosis in Medulloblastoma via miR-383-5p.

BackgroundMedulloblastoma (MB) is the most common malignant brain tumor during childhood. Circular RNA (circSKA3) was identified to function as an oncogene in MB. However, the mechanism of circSKA3 in MB remains unclear.MethodsThe levels of circSKA3, microRNA-383-5p (miR-383-5p), and forkhead box M1 (FOXM1) in MB tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The cell viability and apoptotic rate were assessed via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry, respectively. The protein levels of B-cell lymphoma 2 (Bcl-2), C-Caspase3, and FOXM1 were detected via Western blot assay. Cell cycle was detected by flow cytometry. The migration and invasion abilities were monitored by Transwell assay. The dual-luciferase reporter assay was constructed to verify the interactions between miR-383-5p and circSKA3 or FOXM1. The mice model experiment was carried out to validate the effects of circSKA3 in vivo.ResultsThe levels of circSKA3 and FOXM1 were significantly elevated, while the level of miR-383-5p was notably declined in MB tissues. CircSKA3 was validated to sponge miR-383-5p, and FOXM1 was a candidate target of miR-383-5p. CircSKA3 silencing impeded cell proliferation, migration, and invasion while promoted apoptosis by targeting miR-383-5p in vitro and retarded xenograft tumor growth in vivo. miR-383-5p suppressed cell proliferation, migration, and invasion but promoted apoptosis in MB cells by regulating FOXM1. CircSKA3 depletion decreased FOXM1 expression via miR-383-5p in MB cells.ConclusionCircSKA3 augmented MB progression partly through miR-383-5p/FOXM1 axis.

NPI-0052 and \u03b3-radiation induce a synergistic apoptotic effect in medulloblastoma

Medulloblastoma (MB) is the most common malignant solid paediatric brain tumour. The standard treatment for MB is surgical resection of the tumour, radiation and chemotherapy. This therapy is associated with high morbidity and adverse side effects. Hence, more targeted and less toxic therapies are vitally needed to improve the quality of life of survivors. NPI-0052 is a novel proteasome inhibitor that irreversibly binds the 20S proteasome subunit. This compound has anti-tumour activity in metastatic solid tumours, glioblastoma and multiple myeloma with a good safety profile. Importantly, NPI-0052 has a lipophilic structure and can penetrate the blood–brain barrier, making it a suitable treatment for brain tumours. In the present study, we performed an in silico gene expression analysis to evaluate the proteasome subunit expression in MB. To evaluate the anticancer activity of NPI-0052, we used a range of MB patient-derived MB cells and cell lines. The synergistic cell death of NPI-0052 with γ-radiation was evaluated in tumour organoids derived from patient-derived MB cells. We show that high expression of proteasome subunits is a poor prognostic factor for MB patients. Also, our preclinical work demonstrated that NPI-0052 can inhibit proteasome activity and activate apoptosis in MB cells. Moreover, we observe that NPI-0052 has a synergistic apoptotic effect with γ-radiation, a component of the current MB therapy. Here, we present compelling preclinical evidence that NPI-0052 can be used as an adjuvant treatment for p53-family-expressing MB tumours.

NPI-0052 and gamma-radiation induce a synergistic apoptotic effect in the most aggressive medulloblastoma subgroup

Abstract Group 3 medulloblastoma (MB) is the most aggressive and least characterised of all MB subgroups. These tumours are highly metastatic and patients undergo aggressive treatments leaving survivors with severe side effects. The standard of care for these patients consists of surgical resection followed by gamma-radiation and chemotherapy. Whilst this conventional therapy is successful in the majority of cases, however, many survivors are left with lifelong severe neurocognitive and physical sequelae. Interestingly, the proteasome plays a vital role in the pathogenesis of different tumours, therefore proteasome inhibition can be used as a new strategy for treating MB. NPI-0052 is a proteasome inhibitor that can penetrate the blood-brain barrier with a good safety profile, making it an appealing treatment for brain tumors. In the present study, we evaluate the anticancer activity of NPI-0052 in a range of MB patient derived MB cells and cell lines. Our preclinical work demonstrated that NPI-0052 can inhibit proteasome activity and activate apoptosis in MB cells. We also show that the p53-family plays a substantial role in NPI-0052’s mechanism of action. Moreover, we observe that NPI-0052 has a synergistic apoptotic effect with gamma-radiation, a component of the current MB therapy, in both cells and tumour organoids. Our work underscores the use of NPI-0052 as a novel therapy for reducing the doses of gamma-radiation in G3-MB patients.

Casein kinase 2 inhibition sensitizes medulloblastoma to temozolomide

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Since surviving patients experience severe neurocognitive disabilities, better and more effective treatments are needed to enhance their quality of life. Casein kinase 2 (CK2) is known to regulate cell growth and survival in multiple cancers; however, the role of CK2 in MB is currently being studied. In this study, we verified the importance of CK2 in MB tumorigenesis and discovered that inhibition of CK2 using the small molecule inhibitor, CX-4945, can sensitize MB cells to a well-known and tolerated chemotherapeutic, temozolomide (TMZ). To study the role of CK2 in MB we modulated CK2 expression in multiple MB cells. Exogenous expression of CK2 enhanced cell growth and tumor growth in mice, while depletion or inhibition of CK2 expression decreased MB tumorigenesis. Treatment with CX-4945 reduced MB growth and increased apoptosis. We conducted a high-throughput screen where 4000 small molecule compounds were analyzed to identify compounds that increased the anti-tumorigenic properties of CX-4945. TMZ was found to work synergistically with CX-4945 to decrease cell survival and increase apoptosis in MB cells. O-6-methylguanine-DNA methyltransferase (MGMT) activity is directly correlated to TMZ sensitivity. We found that loss of CK2 activity reduced β-catenin expression, a known MGMT regulator, which in turn led to a decrease in MGMT expression and an increased sensitivity to TMZ. Our findings show that CK2 is important for MB maintenance and that treatment with CX-4945 can sensitize MB cells to TMZ treatment.

Downregulation of EIF5A2 by miR-221-3p inhibits cell proliferation, promotes cell cycle arrest and apoptosis in medulloblastoma cells.

Recently, miR-221-3p expression has been reported to be down-regulated in medulloblastoma (MB), but its functional effects remains unclear. In this study, quantitative real-time PCR (qRT-PCR) revealed significantly decreased miR-221-3p in MB cell lines. Transfection of miR-221-3p mimics reduced, or inhibitor increased cell proliferation in MB cells using MTT assay. Flow cytometry analysis indicated miR-221-3p overexpression promoted, while knockdown alleviated G0/G1 arrest and apoptosis. Luciferase reporter assay confirmed miR-221-3p directly targets the EIF5A2 gene. Moreover, restoration of EIF5A2 in the miR-221-3p-overexpressing DAOY cells significantly alleviated the suppressive effects of miR-221-3p on cell proliferation, cell cycle and apoptosis. Furthermore, miR-221-3p overexpression decreased CDK4, Cyclin D1 and Bcl-2 and increased Bad expression, which was reversed by EIF5A2 overexpression. These results uncovered the tumor suppressive role of miR-221-3p in MB cell proliferation at least in part via targeting EIF5A2, suggesting that miR-221-3p might be a potential candidate target for diagnosis and therapeutics of MB.

Retracted: Effects of microRNA-494 on proliferation, migration, invasion, and apoptosis of medulloblastoma cells by mediating c-myc through the p38 MAPK signaling pathway.

Medulloblastoma (MB) is the most prevalent brain tumor that occurs during childhood and originates from cerebellar granule cell precursors. Based on recent studies, the differential expression of several microRNAs is involved in MB, while the role of microRNA-494 (miR-494) in MB remains unclear. Therefore, we conducted this study to investigate the regulative role of miR-494 in MB cells via the p38 mitogen-activated protein kinase (MAPK) signaling pathway by mediating c-myc. In the current study, MB cells were collected and transfected with miR-494 mimic, miR-494 inhibitor, siRNA- c-myc, and miR-494 inhibitor + siRNA-c-myc. The expressions of miR-494, c-myc, p38 MAPK, B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), interleukin-6 (IL-6), metadherin (MTDH), phosphatase and tensin homolog (PTEN) and survivin were determined. Cell proliferation, cell-cycle distribution, apoptosis, migration, and invasion were evaluated. The results revealed that there was a poor expression of miR-494 and high expression of c-myc in MB tissues. C-myc was determined as the target gene of miR-494. In response to miR-494 mimic, MB cells were found to have increased Bax and PTEN expressions, as well as cell number in G1 phase and cell apoptosis and decreased c-myc, p38 MAPK, Bcl-2, MTDH, IL-6, and survivin expression and cell number count in the S phase, cell proliferation, migration, and invasion. In conclusion, the results demonstrated that the upregulation of miR-494 results in the suppression of cell proliferation, migration, and invasion, while it promotes apoptosis of MB cells through the negative mediation of c-myc, which in turn inactivates the p38 MAPK pathway.

Abstract A45: Tumor suppressor miR-584-5p regulates MYC and sensitizes MYC-amplified medulloblastoma to vincristine and ionizing radiation

Abstract Despite recent improvements in the overall survival of medulloblastoma (MB), only a modest percentage of patients survive high-risk disease. Furthermore, the toxicity associated with current therapies inflicts debilitating lifelong side effects on surviving MB patients. Using an unbiased microRNA screen, we identified miR-584-5p as a potent tumor suppressor that uniquely sensitizes MB to both ionizing radiation (IR) and vincristine (VCR), which are commonly used in combination to treat MB. Our studies revealed that miR-584-5p inhibited MB stem cell proliferation and consequently growth in vivo. Notably, we discovered that miR-584-5p imparts its tumor-suppressor and therapy-sensitizing effects by inhibiting histone deacetylase 1 (HDAC1), eukaryotic translation initiation factor 4e family member 3 (eIF4E3), and C-MYC. We demonstrated that miR-584-5p overexpression or the knockdown of its target genes including eIF4E3 and HDAC1 resulted in G2-M arrest, DNA damage, spindle defects, and apoptosis in MB cells. Meta-analysis of normal brain and MB tumor samples showed that while miR-584-5p is highly expressed in normal brain and cerebellum, it is highly downregulated across all MB subtypes. miR-584-5p targets, on the other hand, are highly overexpressed in MB tumors compared to normal cerebellum. Taken together, this study highlights a previously unidentified role for miR-584-5p, eIF4E3, and HDAC1 in regulating microtubule dynamics and DNA repair pathways. In addition, our study identifies novel targets that can affect the therapeutic efficacy of VCR and IR in MB and sets the stage for a new paradigm of treating medulloblastoma using microRNA-based therapeutics. Citation Format: Nourhan Abdelfattah, Subapriya Rajamanickam, Santosh Timilsina, Panneerdoss Subbarayalu, Benjamin Onyeagucha, Manjeet Rao. Tumor suppressor miR-584-5p regulates MYC and sensitizes MYC-amplified medulloblastoma to vincristine and ionizing radiation [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A45.

Abstract 889: Metformin treatment inhibits proliferation and induces apoptosis in medulloblastoma cells

Abstract Medulloblastoma is the most common malignant brain tumor in children that typically requires a patient specific combination of surgical resection, chemotherapy, and radiation. Up to 80% of medulloblastoma patients respond to treatment and survive long-term. However, survivors often suffer from severe long term sequelae secondary to treatment that affects their neurocognitive and growth potential. Therefore, there is an urgency to develop less toxic, more focused treatment strategies that target specific pathways or molecules involved in medulloblastoma development and progression. Metformin is a widely used non-toxic anti-diabetic drug that has mild, generally well-tolerated side effects. Studies have shown that it can reduce cancer risk and improve the prognosis of certain malignancies. However, the mechanism underlying its anti-cancer effect is still unclear and varies depending on the type of cancer. There are reports that metformin can target the specificity protein 1 (Sp1) transcription factor. Sp1 regulates the expression of a variety of proteins involved in regulation of cancer cell proliferation including survivin, an Inhibitor of Apoptosis Protein family member. Expression of survivin is increased in medulloblastoma cells and often correlates with poor prognosis. We studied the anti-cancer activity of metformin on medulloblastoma using DAOY and D283 cells. Metformin treatment resulted in a dose and time dependent reduction in cell proliferation in both cell lines. This growth inhibition was accompanied by the induction of apoptosis as determined by annexin-V staining, PARP cleavage, and activation of caspase3/7. Metformin also induced cell cycle arrest in G0/G1 phase. Western blot analysis using extracts from cells treated with metformin revealed that the anti-proliferative and apoptotic effects of metformin in medulloblastoma were accompanied by a reduction in the expression of survivin protein. Overexpression of survivin is reported to be associated with chemo- and radio-resistance. This study suggests the use of metformin as a novel anticancer agent in combination with standard therapy for the treatment of medulloblastoma. Citation Format: Kristen C. Payne, Abigail Hunter, W Paul Bowman, Jeffrey C. Murray, Riyaz Basha, Umesh T. Sankpal. Metformin treatment inhibits proliferation and induces apoptosis in medulloblastoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 889.

BKM120 induces apoptosis and inhibits tumor growth in medulloblastoma.

Medulloblastoma (MB) is the most common malignant brain tumor in children, accounting for nearly 20 percent of all childhood brain tumors. New treatment strategies are needed to improve patient survival outcomes and to reduce adverse effects of current therapy. The phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) intracellular signaling pathway plays a key role in cellular metabolism, proliferation, survival and angiogenesis, and is often constitutively activated in human cancers, providing unique opportunities for anticancer therapeutic intervention. The aim of this study was to evaluate the pre-clinical activity of BKM120, a selective pan-class I PI3K inhibitor, on MB cell lines and primary samples. IC50 values of BKM120 in the twelve MB cell lines tested ranged from 0.279 to 4.38 μM as determined by cell viability assay. IncuCyte ZOOM Live-Cell Imaging system was used for kinetic monitoring of cytotoxicity of BKM120 and apoptosis in MB cells. BKM120 exhibited cytotoxicity in MB cells in a dose and time-dependent manner by inhibiting activation of downstream signaling molecules AKT and mTOR, and activating caspase-mediated apoptotic pathways. Furthermore, BKM120 decreased cellular glycolytic metabolic activity in MB cell lines in a dose-dependent manner demonstrated by ATP level per cell. In MB xenograft mouse study, DAOY cells were implanted in the flank of nude mice and treated with vehicle, BKM120 at 30 mg/kg and 60 mg/kg via oral gavage daily. BKM120 significantly suppressed tumor growth and prolonged mouse survival. These findings help to establish a basis for clinical trials of BKM120, which could be a novel therapy for the treatment of medulloblastoma patients.

Inhibition of the CyclinD1 promoter in response to sonic hedgehog signaling pathway transduction is mediated by Gli1.

Medulloblastoma (MB) is the most common malignant tumor of the central nervous system in children. Accumulating evidence suggests a major role for the activation of the sonic hedgehog (SHH) signaling pathway in the development of MB cells; however, the mechanisms underlying the effect of this pathway on tumor survival and growth remain poorly understood. The Gli family zinc finger 1 (Gli1) transcription factor is considered as a mediator of the SHH signaling pathway in MB cells. Therefore, the present study investigated whether the SHH signaling pathway promotes the apoptosis of MB cells via downregulation of Gli1. GANT61, a novel Gli1 inhibitor, is known to have an in vitro activity against tumors. In the current study, Daoy cells were treated with different concentrations of GANT61 for 24 h, and the effect on cell proliferation was assayed by cell counting kit-8 assay. In addition, the cell cycle progression and apoptosis were assayed by flow cytometry analysis and hematoxylin-eosin (HE) staining. The effects of GANT61 treatment on SHH signaling pathway at the mRNA level were assayed by polymerase chain reaction (PCR). To further elucidate the inhibitory effects of GANT61 on the expression of Gli1 and CyclinD1, their protein levels were examined by western blot and immunofluorescence. The results indicated that GANT61 significantly inhibited the proliferation of Daoy cells in a dose-dependent manner, compared with the control group (P<0.05). HE staining revealed that cells had increasingly abnormal protuberance with increasing GANT61 concentration. Flow cytometry analysis also demonstrated that GANT61 induced G1/S arrest and apoptosis of Daoy cells in a dose-dependent manner (P<0.05). Gli1 and CyclinD1 mRNA expression levels were downregulated by GANT61 treatment (P<0.05); similarly, their protein levels were downregulated by GANT61 treatment in a dose-dependent manner (P<0.05). In conclusion, Gli1 expression was significantly associated with CyclinD1 expression in MB. These data demonstrated that Gli1 is an important mediator of the SHH pathway activity in MB, and may be a novel agent for use in combined chemotherapeutic regimens.

Blockade of Inhibitors of Apoptosis Proteins in Combination with Conventional Chemotherapy Leads to Synergistic Antitumor Activity in Medulloblastoma and Cancer Stem-Like Cells.

BackgroundMedulloblastoma (MB) is the most common pediatric primary malignant brain tumor. Approximately one-third of MB patients succumb to treatment failure and some survivors suffer detrimental side effects. Hence, the purpose of this study is to explore new therapeutic regimens to overcome chemotherapeutic agent resistance or reduce chemotherapy-induced toxicity.MethodsWe detected the expression of inhibitors of apoptosis proteins (IAPs) in MB and CD133+ MB cell lines and MB tissues using immunoblotting and immunohistochemical staining. The antitumor effects of inhibitors against IAPs on MB or CD133+ MB cells were evaluated by MTT assay, Annexin V/PI analysis, and caspase-3/7 activity. Autophagy was assessed by the conversion of light chain (LC) 3-I to LC3-II and Cyto-ID autophagy detection kit.ResultsMB cells showed higher expression of IAPs compared to normal astrocytes and normal brain tissues. Conventional chemotherapeutic agents combined with small-molecule IAP inhibitors (LCL161 or LBW242) showed a synergistic effect in MB cells. Combined treatments triggered apoptosis in MB cells through activation of caspase-3/7 and autophagic flux simultaneously. In addition, we found that CD133+ MB cells with features of cancer stem cells displayed higher levels of X-linked inhibitor of apoptosis (XIAP) and cellular inhibitor of apoptosis 1/2 (cIAP1/2), and were hypersensitive to treatment with IAP inhibitors.ConclusionsThese results shed light on the biological effects of combination therapy on MB cells and illustrate that IAP inhibitors are more effective for CD133+ stem-like MB cells.

Abstract 3197: BKM120 promotes apoptosis and suppresses tumor growth in medulloblastoma by targeting the phosphoinositide 3-kinase pathway

Abstract Background: Medulloblastoma (MB) is the most common malignant brain tumor in children with poor survival outcome. New treatment strategies are needed for control of MB. The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) intracellular signaling pathway plays a key role in cellular metabolism, proliferation, survival and angiogenesis. This pathway is often constitutively activated in human tumor cells, providing unique opportunities for anticancer therapeutic intervention. BKM120 (Buparlisib) is an oral pan-class I PI3K inhibitor that targets all 4 isoforms of class I PI3K. BKM120 is currently being clinically evaluated for the treatment of different adult cancers including breast cancer, glioblastoma, prostate cancer, advanced non-small cell lung cancer, and colorectal cancer. In this study, we screened our MB established and patient primary cell lines by genomic profiling analysis, and validated the targeted therapy both in vitro and in vivo in xenograft mouse model. Methods: RNA expression profiling analysis was performed with Affymetrix GeneChip U133 Plus 2.0 genome wide expression cDNA microarray. Analysis was done using R/Bioconductor packages and Partek Genomics Suite. Eleven MB cell lines were treated with increasing concentrations (0-4 μM) of BKM120 for 48 hours. CellTiter-Glo Luminescent Cell Viability Assay was used to determine cell viability. IC50 values were calculated with a four-parameter variable-slope dose response curve using GraphPad Prism v.5 software. IncuCyte ZOOM Live-Cell Imaging system was used for kinetic monitoring of cytotoxicity of BKM120 and apoptosis in MB cells. Western blot analysis was used to measure phospho-Akt, phospho-mTOR, and cleaved caspase 3 protein levels. ATP level per cell was measured using CyQuant fluorescent DNA assay combined with CellTiter-Glo luminescent cell viability assay. Xenograft study was performed with DAOY cells implanted in the flank of nude mice and treated with vehicle, BKM120 at 30 mg/kg and 60 mg/kg via oral gavage daily. Results: BKM120 exhibited cytotoxicity in MB cells in a dose-dependent manner by inhibiting activation of downstream signaling molecules Akt and mTOR, and activating apoptotic pathways and inducing cell death in the eleven cell lines tested. IC50s of BKM120 in the MB cell lines ranged from 0.456 to 2.9 μM determined by cell viability assay. Furthermore, BKM120 decreased cellular glycolytic metabolic activity in MB cell lines in a dose-dependent manner. In MB xenograft mouse study, BKM120 significantly suppressed tumor growth and prolonged mouse survival at 30 mg/kg and 60 mg/kg. Conclusion: This study indicates that BKM120 promotes apoptosis and suppresses medulloblastoma tumor growth both in vitro and in vivo. Additional investigation of BKM120 for the treatment of pediatric medulloblastoma is warranted. Citation Format: Ping Zhao, Jacob Hall, Austin Voydanoff, Mary Durston, Elizabeth VanSickle, Abhinav B. Nagulapally, Jeffery Bond, Giselle Saulnier Sholler. BKM120 promotes apoptosis and suppresses tumor growth in medulloblastoma by targeting the phosphoinositide 3-kinase pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3197.

Thymoquinone inhibits growth of human medulloblastoma cells by inducing oxidative stress and caspase-dependent apoptosis while suppressing NF-κB signaling and IL-8 expression.

Medulloblastoma (MB) is the most common malignant brain tumor of childhood. The transcription factor NF-κB is overexpressed in human MB and is a critical factor for MB tumor growth. NF-κB is known to regulate the expression of interleukin-8 (IL-8), the chemokine that enhances cancer cell growth and resistance to chemotherapy. We have recently shown that thymoquinone (TQ) suppresses growth of hepatocellular carcinoma cells in part by inhibiting NF-κB signaling. Here we sought to extend these studies in MB cells and show that TQ suppresses growth of MB cells in a dose- and time-dependent manner, causes G2M cell cycle arrest, and induces apoptosis. TQ significantly increased generation of reactive oxygen species (ROS), while pretreatment of MB cells with the ROS scavenger N-acetylcysteine (NAC) abrogated TQ-induced cell death and apoptosis, suggesting that TQ-induced cell death and apoptosis are oxidative stress-mediated. TQ inhibitory effects were associated with inhibition of NF-κB and altered expression of its downstream effectors IL-8 and its receptors, the anti-apoptotic Bcl-2, Bcl-xL, X-IAP, and FLIP, as well as the pro-apoptotic TRAIL-R1, caspase-8, caspase-9, Bcl-xS, and cytochrome c. TQ-triggered apoptosis was substantiated by up-regulation of the executioner caspase-3 and caspase-7, as well as cleavage of the death substrate poly(ADP-ribose)polymerase. Interestingly, pretreatment of MB cells with NAC or the pan-caspase inhibitor zVAD-fmk abrogated TQ-induced apoptosis, loss of cyclin B1 and NF-κB activity, suggesting that these TQ-mediated effects are oxidative stress- and caspase-dependent. These findings reveal that TQ induces both extrinsic and intrinsic pathways of apoptosis in MB cells, and suggest its potential usefulness in the treatment of MB.