Lack of radiosensitization of M443 on normal brain cells.

PDF - 1060KB, Sorafenib suppresses JNK-dependent apoptosis as assessed by cleaved caspase 3.

PDF - 69KB, In-vitro kinase assays were performed against sorafenib with a staurosporine positive control across a concentration range of 0.5 nM to 10 μM). Blank values are those for which no significant inhibition occurred over the entire concentration range.

Glioblastoma (GBM) is the most common primary malignant brain cancer in adults. A hallmark of GBM is aggressive invasion of tumor cells into the surrounding normal brain. The current standard of care therapy, as well as targeted therapies, has largely failed to specifically address this issue. Therefore, identifying key regulators of GBM cell migration and invasion is of particular interest. The leukemia-associated Rho guanine nucleotide exchange factor (LARG) has previously been implicated in cell invasion in other tumor types; however, the role of LARG in GBM pathobiology remains undefined. Herein, we report that the expression level of LARG, RhoC, and RhoA increases with glial tumor grade and is highest in GBM. LARG and RhoC protein expression is more prominent in the invading cells, whereas RhoA expression is largely restricted to cells in the tumor core. Knockdown of LARG by siRNA inhibits GBM cell migration in vitro and invasion ex vivo in organotypic brain slices. Moreover, siRNA-mediated silencing of RhoC suppresses GBM cell migration in vitro and invasion ex vivo, whereas depletion of RhoA enhances GBM cell migration and invasion, supporting a role for LARG and RhoC in GBM cell migration and invasion. Depletion of LARG increases the sensitivity of GBM cells to temozolomide treatment. Collectively, these results suggest that LARG and RhoC may represent unappreciated targets to inhibit glioma invasion.

Glioblastoma (GBM) is the most common primary malignant brain cancer in adults. A hallmark of GBM is aggressive invasion of tumor cells into the surrounding normal brain. Both the current standard of care and targeted therapies have largely failed to specifically address this issue. Therefore, identifying key regulators of GBM cell migration and invasion is important. The leukemia-associated Rho guanine nucleotide exchange factor (LARG) has previously been implicated in cell invasion in other tumor types; however, its role in GBM pathobiology remains undefined. Herein, we report that the expression levels of LARG and ras homolog family members C (RhoC), and A (RhoA) increase with glial tumor grade and are highest in GBM. LARG and RhoC protein expression is more prominent in invading cells, whereas RhoA expression is largely restricted to cells in the tumor core. Knockdown of LARG by siRNA inhibits GBM cell migration in vitro and invasion ex vivo in organotypic brain slices. Moreover, siRNA-mediated silencing of RhoC suppresses GBM cell migration in vitro and invasion ex vivo, whereas depletion of RhoA enhances GBM cell migration and invasion, supporting a role for LARG and RhoC in GBM cell migration and invasion. Depletion of LARG increases the sensitivity of GBM cells to temozolomide treatment. Collectively, these results suggest that LARG and RhoC may represent unappreciated targets to inhibit glioma invasion.

Abstract BACKGROUND Glioblastomas show marked intra- and inter-tumor heterogeneity and are strongly resistant to both radio- and chemo-therapy, which are standard therapeutic modalities for this tumor. MicroRNAs (miRNAs) have the potential to serve as effective therapeutics for glioblastoma as they modulate the activity of multiple signaling pathways. METHODS Glioblastoma cultures were transfected with miR-34a or control miRNA mimics to assess biological function and therapeutic potential in vitro. miR-34a was packaged into bacterially-derived nanocells and administered intravenously for delivery to orthotopic patient-derived glioblastoma xenografts in mice. RESULTS Overexpression of miR-34a strongly reduced the activation status of the three core signaling networks that have been found to be deregulated in the vast majority of glioblastoma tumors, the receptor tyrosine kinase, p53 and Rb networks. miR-34a transfection also inhibited the survival of multiple established glioblastoma cell lines as well as primary patient-derived xenograft cultures representing the proneural, mesenchymal and classical subtypes. Transfection of miR-34a synergized with temozolomide (TMZ) in in vitro cultures of glioblastoma cells with primary TMZ sensitivity, primary TMZ resistance and acquired TMZ resistance. Intravenous administration of bacterially-derived nanocells carrying miR-34a strongly enhanced TMZ sensitivity in an orthotopic patient-derived xenograft mouse model of glioblastoma. CONCLUSIONS miR-34a strongly sensitizes a wide range of glioblastoma cell cultures to TMZ, suggesting that combination therapy of TMZ with miR-34a may serve as a novel therapeutic approach for the treatment of glioblastoma tumors. Bacterially-derived nanocells are an effective vehicle for the delivery of miR-34a to glioblastoma tumors.

Abstract Therapeutic resistance stemming from inter and intra-tumoral heterogeneity is a significant impediment towards development of effective therapeutics for glioblastoma. We hypothesized that microRNAs can potentially counteract resistance emanating from such heterogeneity as they simultaneously modulate the expression of multiple proteins. We identified microRNA-34a as a unique microRNA which modulates multiple oncoproteins in GBM using two different in silico approaches. We investigated the therapeutic effects of microRNA-34a in three primary patient-derived xenografts (PDX) representing classical (GBM6), proneural (GBM118) and mesenchymal (GBM118) subtypes; four established cell lines (T98G, U251, A172, LN229) and two cell lines with acquired resistance to temozolomide (A172-TR, LN229-TR) in vitro. Glioblastoma cell cultures showed variable responses to temozolomide but microRNA-34a inhibited proliferation in all cell cultures. Furthermore, microRNA-34a also sensitized all tested cell lines to temozolomide (combination index < 0.8, p=.03) and radiation treatment (dose enhancement factor 1.7–2.2, p=0.02). Mechanistically, microRNA 34a down-regulates at least six distinct therapeutic resistance proteins. Importantly, these resistance proteins are expressed in distinct spatial niches and are prognostic for patient survival based on our analysis of the cancer genome atlas (TCGA) data. For in vivo delivery of microRNA-34a, we utilized nanocells which are derived from genetically modified bacteria, loaded with microRNA-34a and tagged with a bispecific antibody targeting EGFR. Nanocells were injected intravenously while temozolomide was administered by oral gavage in an orthotopic PDX model. We confirmed delivery of microRNA-34a to tumor by observing down-regulation of cMet and phosphorylated Akt in treated mice. Importantly, microRNA-34a nanocells resulted in significant reduction in tumor growth (p=0.021), increased survival (p<0.001) with microRNA-34a monotherapy and synergy in combination with temozolomide in vivo. Taken together, our results suggest that delivery of miR-34a may be a powerful new adjuvant for the treatment of glioblastoma in combination with temozolomide that can mitigate both inter- and intra-tumor heterogeneity.

Glioblastoma multiforme (GBM) is the most common type of malignant brain tumors in adults and has a dismal prognosis. The highly aggressive invasion of malignant cells into the normal brain parenchyma renders complete surgical resection of GBM tumors impossible, increases resistance to therapeutic treatment, and leads to near-universal tumor recurrence. We have previously demonstrated that TROY (TNFRSF19) plays an important role in glioblastoma cell invasion and therapeutic resistance. However, the potential downstream effectors of TROY signaling have not been fully characterized. Here, we identified PDZ-RhoGEF as a binding partner for TROY that potentiated TROY-induced nuclear factor kappa B activation which is necessary for both cell invasion and survival. In addition, PDZ-RhoGEF also interacts with Pyk2, indicating that PDZ-RhoGEF is a component of a signalsome that includes TROY and Pyk2. PDZ-RhoGEF is overexpressed in glioblastoma tumors and stimulates glioma cell invasion via Rho activation. Increased PDZ-RhoGEF expression enhanced TROY-induced glioma cell migration. Conversely, silencing PDZ-RhoGEF expression inhibited TROY-induced glioma cell migration, increased sensitivity to temozolomide treatment, and extended survival of orthotopic xenograft mice. Furthermore, depletion of RhoC or RhoA inhibited TROY- and PDZ-RhoGEF–induced cell migration. Mechanistically, increased TROY expression stimulated Rho activation, and depletion of PDZ-RhoGEF expression reduced this activation. Taken together, these data suggest that PDZ-RhoGEF plays an important role in TROY signaling and provides insights into a potential node of vulnerability to limit GBM cell invasion and decrease therapeutic resistance.

microRNA-34a could serve as a novel therapeutic agent since it is under-expressed in Glioblastoma and modulates the expression of multiple genes in the deregulated p53, Rb and receptor tyrosine kinase networks which confer selective growth advantage and represent significant intra-tumoral heterogeneity, a major cause of therapeutic resistance. We studied the effects of microRNA-34a transfection in three primary patient-derived lines (GBM 6, GBM118 and GBM 126, respectively belonging to classical, mesenchymal and proneural subtypes), four established cell lines (T98G, U251, A172, LN229; where T98G and U251 show primary resistance to treatment while A172 and LN229 are sensitive) and two cell lines with acquired resistance to temozolomide (A172TR, LN229TR). microRNA-34a reduced proliferation and sensitized to temozolomide (Combination Index< 0.2–0.6) and radiation (dose enhancement factor 1.7–2.2) treatment, regardless of baseline treatment resistance in all studied cell lines. We identified broadly conserved microRNA-34a binding sites in the 3’UTR of multiple mRNAs in the Glioblastoma deregulated networks and genes known to confer therapeutic resistance and validated the direct downregulation of Bcl-2 protein as a major contributor to temozolomide sensitization. Nanocells (400nm diameter), termed EDV, were derived from genetically modified bacteria, provided with a bispecific antibody targeting EGFR and loaded with microRNA-34a. EDVs were injected intravenously while temozolomide was administered by oral gavage in GBM6 orthotopic mouse model. We observed significant increases in miR-34a expression, downregulation of oncogenes and reduction in tumor growth in mice treated with microRNA-34a EDV relative to control EDV(p=0.021). Further, microRNA-34a EDV significantly improved survival and synergized with temozolomide therapy [p<0.001, median survival of control EDV, microRNA-34a EDV, control EDV with temozolomide and microRNA-34a EDV with temozolomide was 44, 48, 86 and 165+ days respectively]. In conclusion, microRNA-34a EDV counteracts therapeutic resistance and intra-tumor heterogeneity.

microRNA-34a could serve as a novel therapeutic agent as it is under-expressed in Glioblastoma and modulates the expression of multiple genes in the deregulated p53, Rb and receptor tyrosine kinase networks which confer selective growth advantage and represent significant intra-tumoral heterogeneity, a major cause of therapeutic resistance. We studied the effects of microRNA-34a transfection in three primary patient-derived lines (GBM 6, GBM118 and GBM 126, respectively belonging to classical, mesenchymal and proneural subtypes), four established cell lines (T98G, U251, A172, LN229; where T98G and U251 show primary resistance to treatment while A172 and LN229 are sensitive) and two cell lines with acquired resistance to temozolomide (A172-TR, LN229-TR). Transfection with microRNA-34a mimics significantly reduced proliferation and sensitized to temozolomide (Combination Index< 0.2–0.6) and radiation (dose enhancement factor 1.7–2.2) treatment, regardless of baseline treatment resistance in all studied cell lines. We identified broadly conserved binding sites in the 3’UTR of multiple mRNAs in the Glioblastoma deregulated networks and genes known to confer therapeutic resistance and validated the direct downregulation of Bcl-2 protein as a major contributor to temozolomide sensitization. For in vivo delivery, nanocells (400 nm diameter), termed EDV, were derived from genetically modified bacteria, provided with a bispecific antibody targeting EGFR and loaded with microRNA-34a. EDVs were injected intravenously while temozolomide was administered by oral gavage in GBM6 orthotopic mouse model. We observed a significant reduction in tumor growth in mice treated with microRNA-34a EDV relative to control EDV-treated mice (p=0.021). Further, microRNA-34a EDV significantly improved survival and synergized with temozolomide therapy [p<0.001, median survival of control EDV, microRNA-34a EDV, control EDV with temozolomide and microRNA-34a EDV with temozolomide was 44, 48, 86 and 147+ days respectively]. In conclusion, microRNA-34a EDV is a promising novel therapeutic that inhibits Glioblastoma tumor growth and counteracts therapeutic resistance and intra-tumor heterogeneity.

The microtubule inhibitor vincristine is currently used to treat a variety of brain tumors, including low-grade glioma and anaplastic oligodendroglioma. Vincristine, however, does not penetrate well into brain tumor tissue, and moreover, it displays dose-limiting toxicities, including peripheral neuropathy. Mebendazole, a Food and Drug Administration-approved anthelmintic drug with a favorable safety profile, has recently been shown to display strong therapeutic efficacy in animal models of both glioma and medulloblastoma. Importantly, appropriate formulations of mebendazole yield therapeutically effective concentrations in the brain. Mebendazole has been shown to inhibit microtubule formation, but it is not known whether its potency against tumor cells is mediated by this inhibitory effect. To investigate this, we examined the effects of mebendazole on GL261 glioblastoma cell viability, microtubule polymerization and metaphase arrest, and found that the effective concentrations to inhibit these functions are very similar. In addition, using mebendazole as a seed for the National Cancer Institute (NCI) COMPARE program revealed that the top-scoring drugs were highly enriched in microtubule-targeting drugs. Taken together, these results indicate that the cell toxicity of mebendazole is indeed caused by inhibiting microtubule formation. We also compared the therapeutic efficacy of mebendazole and vincristine against GL261 orthotopic tumors. We found that mebendazole showed a significant increase in animal survival time, whereas vincristine, even at a dose close to its maximum tolerated dose, failed to show any efficacy. In conclusion, our results strongly support the clinical use of mebendazole as a replacement for vincristine for the treatment of brain tumors.

Group-3 Medulloblastomas (MBL) has the worst prognosis due to its resistance to radiation and chemotherapy with a 5-year survival of 30%. Thus, there is an urgent need to elucidate targets that can sensitize Group-3 tumors to conventional treatments. We identified PRDX1 as a candidate therapeutic target for therapy sensitization in group-3 tumors. PRDX1 catalyzes the conversion of hydrogen peroxide to water and oxygen. We hypothesized that inhibiting PRDX1 would lead to oxidative stress and increase susceptibility to ionizing radiation via extensive DNA damage. Accordingly, when PRDX1 was targeted using Adenanthin (specific chemical inhibitor) or RNAi, Group-3 MBL (D425-MED) cells were rendered hypersensitive to radiation. Mechanistically, targeting PRDX1 resulted in an increase in reactive oxygen species, extensive oxidative DNA damage and an induction of the apoptotic pathway. Similarly, overexpression of PRDX1 in MBL cells susceptible to radiation (DAOY, UW-228) resulted in radiation resistance. However targeting PRDX1 in normal astrocytes did not have any sensitization effects. The in-vitro results were validated in-vivo using flank tumors (Adenanthin) and an orthotopic murine model (both RNAi and Adenanthin) using Group-3 MBL cells (D425-MED) and patient derived xenografts (MB3W1). Briefly, mice bearing Group-3 MBL tumors (D425-MED / MB3W1) when subjected to treatment with Adenanthin combined with radiation achieved a synergistic increase in survival. To fully evaluate the therapeutic potential of PRDX1 across all groups of MBL, we determined the expression of PRDX1 in a validated MBL tumor micro-array (TMA) by immunohistochemistry and correlated it with patient characteristics, therapeutic response and clinical outcomes. We also evaluated the role of PRDX1 in Group-3 MBL stem cells with respect to radiation resistance, invasion and migration. The results from these experiments will be presented in the meeting. Our data suggest that PRDX1 is a therapeutic target in Group-3 MBL and Adenanthin as a small molecule inhibitor of PRDX1.

Group-3 medulloblastoma (MBL) is highly resistant to radiation (IR) and chemotherapy and has the worst prognosis. Hence, there is an urgent need to elucidate targets that sensitize these tumors to chemotherapy and IR. Employing standard assays for viability and sensitization to IR, we identified PRDX1 as a therapeutic target in Group-3 MBL. Specifically, targeting PRDX1 by RNAi or inhibition by Adenanthin led to specific killing and sensitization to IR of Group-3 MBL cells. We rescued sensitization of Daoy and UW228 cells by hypermorphic expression of PRDX1. PRDX1 knockdown caused oxidative DNA damage and induced apoptosis. We correlated PRDX1 expression to patient outcomes in a validated MBL tumor-microarray. Whole genome sequencing identified pathways/genes that were dysregulated with PRDX1 inhibition or silencing. Our in vivo studies in mice employing flank/orthotopic tumors from patient derived xenografts/Group-3 MBL cells confirmed in vitro observations. Animals with tumors in which PRDX1 was targeted by RNAi or Adenanthin (using mini osmotic pumps) showed decreased tumor burden and increased survival when compared to controls. Since, Adenanthin does not cross the blood brain barrier (BBB) we used HAV6 peptide to transiently disrupt the BBB and deliver Adenanthin to the tumor. Immunohistochemistry confirmed that targeting PRDX1 resulted in increased oxidative DNA damage, apoptosis and decreased proliferation. In summary, we have validated PRDX1 as a therapeutic target in group-3 MBL, identified Adenanthin as a potent chemical inhibitor of PRDX1 and confirmed the role of HAV peptide (in the transient modulation of BBB permeability) in an orthotopic model of group-3 MBL.

Medulloblastoma is the most common malignant pediatric brain tumor that comprises at least 4 subgroups based on molecular characterization: WNT, SHH, group 3 and 4. Group 3 medulloblastoma is the most aggressive subtype with the worst prognosis due to its propensity to metastasize and resistance to therapy. Disulfiram (DSF) is a drug used in the treatment of chronic alcoholism that has been shown to have antineoplastic effects in a number of different cancers including glioblastoma. Its potency has been shown to be enhanced by copper. We tested two established medulloblastoma cell lines, UW228 and D425MED group 3 cells, and two primary cultures, IMB187 WNT and IMB226 SHH cells, for their sensitivity to DSF/Cu using the WST in vitro assay. We found that, whereas DSF on its own has little effect on medulloblastoma cells, in combination with a low concentration (350 nM) of Cu, which on its own has no effect, DSF strongly inhibited the viability of all tested medulloblastoma cells. The IC50 for DSF ranges between 60 nM and 230 nM, with UW228 cells being the most sensitive and the D425MED the least sensitive. DSF/Cu also has been shown to sensitize tumor cells to chemotherapy in a number of different settings. Studies to examine the therapeutic efficacy of DSF/Cu in the D425MED orthotopic animal model of medulloblastoma, both as monotherapy and in combination with the chemotherapeutic cisplatin, are in progress.

Medulloblastoma is the most common pediatric central nervous system cancer, and despite an overall favorable prognosis with intensive multimodal treatment, children are especially at risk for significant negative effects of these treatments. There is a need for treatments that are less toxic with fewer negative long-term sequelae. Curcumin, the active component of the dietary spice turmeric, has shown promising anti-cancer effects in vitro and in preclinical models of many types of cancer, including medulloblastoma. Along with its potent anti-cancer effects, low toxicity and a wide therapeutic window make curcumin an ideal candidate as a novel therapeutic for pediatric cancer. A major barrier to achieving curcumin’s potential is poor bioavailability. To address this challenge we are focusing on two approaches: Meriva and TRB-N0224. Meriva is a curcumin-phosphatidylcholine complex shown to have 18-fold higher absorption than unformulated curcumin, while TRB-N0224 is a chemically modified curcumin. Our objective is to demonstrate therapeutic efficacy in an animal model of medulloblastoma. In vitro studies were conducted using the primary cell lines IMB226 sonic hedgehog-type cells (SHH) and D425MED group 3 medulloblastoma cells. Animal studies were performed using 2 models: a D425MED orthotopic xenograft model in immunocompromised mice and an orthotopic transplant model of group 3 medulloblastoma (Myc + DN-p53) in syngeneic C57BL/6 mice. We have demonstrated in vitro efficacy of both Meriva and TRB-N0224 against SHH and group 3 medulloblastoma cells. The D425MED animal model revealed negligible efficacy of Meriva using either oral or intraperitoneal administration. A pilot study with the Myc + DN-p53 model revealed a dose-dependent trend toward therapeutic efficacy of both Meriva and TRB-N0224 which point to a possible immunomodulatory role of curcumin in the control of tumor growth. Experiments with larger cohorts are in progress.

Glioblastoma (GBM) is the most common type of primary brain tumor. Despite maximum primary treatment with gross total tumor resection followed by fractionated radiotherapy to 60 Gy concomitant with temozolomide, the prognosis is poor with a median survival of only 14.6 mo.1 The tumors are highly invasive and inherently resistant to radiation. Thus, gliomas inevitably recur and the few patients with long-term survival suffer from radiation-induced cognitive deficits.2 As radiation therapy is the single most effective treatment, efforts to improve radiation therapy is of utmost importance. The beneficial effect of radiation may be enhanced in combination with drugs. Neuroprotectors would decrease complication rates, and they even may allow for increased treatment doses, whereas tumor-selective radiosensitizers would allow for lower treatment doses without compromising the antitumor effect. Wouldn’t it be good to have a drug that does both? Small molecule inhibitors of colony stimulating factor-1 receptor (CSF-1R) may fit the bill. The neuroprotective role of one such CSF-1R inhibitor (PLX5622) was demonstrated in a recent study by Acharya et al.3 They studied the effect of the PLX5622 on microglia activation and the role of microglia in the response of the brain to radiotherapy. Radiation-induced injury has been linked to persistent microglial activation. Microglia are the principle immune cells in the brain that eliminate accumulated debris, thereby serving a neuroprotective role. Microglia are dependent on the CSF-1R for their growth and survival. Targeted inhibition of CSF-1R leads to rapid and virtually complete elimination of microglia, while cessation of drug treatment led to rapid repopulation of the microglia within a few days. Acharya et al3 compared whole brain irradiation (9 Gy) of healthy tumor free mice with sham-irradiated mice in the absence and presence of PLX5622 administered in the diet 30 min after irradiation and for 6 wk. The mice were then tested for cognitive behavior. Irradiation of animals receiving normal diet caused severe cognitive deficits in 3 different tests (novel object recognition, object in place, and fear conditioning) and increased microglial activation. Notably, cognition remained intact and microglia were not activated in either irradiated or sham-irradiated mice receiving PLX5622. Thus, elimination of microglia through CSF-1R inhibition ameliorates the radiation-induced cognitive deficits seen in whole brain-irradiated mice, without having serious side effects as monotherapy. The potential of CSF-1R inhibitors to act as radiosensitizers was shown by Stafford et al4 using a human GBM xenograft model. The CSF-1R inhibitor PLX3397 reduced the number of CD11b+ myeloid cells that accumulate in irradiated GBM tumors and gave rise to immune-suppressive tumor-associated macrophages. Importantly, PLX3397 synergized with radiation to increase survival in mice bearing GBM tumors, but had no effect as monotherapy. It is, therefore, not surprising that a recent phase II clinical study5 investigating the effect of PLX3397 in patients with recurrent GBM in the absence of radiation did not show improvement in progression-free survival. The drug was, however, well tolerated and demonstrated to readily cross the blood–brain barrier. Radiation therapy has been shown to enhance the invasiveness of glioma cells6 and microglia play a critical role in glioma cell invasion. Indeed, the CSF-1R inhibitor PLX3397 has been shown to potently inhibit glioma spread in an orthotopic murine model of glioma.7 Thus, CSF-1R inhibitors may act by a third mechanism to improve radiation therapy that is by inhibiting radiation-induced GBM invasiveness. Interestingly, the CSF-1R inhibitor PLX647 has been shown to sensitize tumors to T cell checkpoint blockade in a mouse model of melanoma.8 PLX647 monotherapy blocked tumor-infiltrating myeloid-derived suppressor cells and enhanced the antitumor T cell responses, resulting in delayed tumor growth with a modest benefit on survival. However, in combination with T cell checkpoint blockade (α-CTLA4 and α-PD1), PLX647 resulted in significantly prolonged survival compared to either treatment alone. These results suggest that CSF-1R inhibitors also may enhance the beneficial radiation-induced immune response directed towards the tumor, thereby improving radiation therapy by yet another mechanism. In summary, CSF-1R inhibitors may act on 4 different levels to enhance the therapeutic effects of radiation on brain tumors and mitigate radiation-induced side effects. These inhibitors are well tolerated, and importantly, cross the blood–brain barrier. Thus, future clinical trials combining radiation therapy with CSF-1R inhibitors are warranted to evaluate these 4 potential mechanisms in GBM patients. CSF-1R inhibitors in combination with radiation may be a powerful approach to improve the dismal prognosis and reduce the devastating neurotoxicity associated with GBM treatment today.

Group-3 medulloblastoma (MBL), one of the most common malignant pediatric brain tumors, is highly resistant to radiation and chemotherapy and have the worst prognosis. Hence, there is an urgent need to elucidate targets that can sensitize these tumors to conventional chemotherapy and radiation. We identified PRDX1 as therapeutic candidate in Group-3 MBL. Inhibition of PRDX1 using Adenanthin or RNAi led to radiation sensitization in D425-med cells when compared to controls. Over expression of PRDX1 in SHH- group (Daoy cells) resulted in radiation resistance. Targeting PRDX1 resulted in extensive oxidative DNA damage and induction of apoptosis. Nude mice with Group-3 MBL flank tumors when treated with Adenanthin had significant decrease in tumor volume and survived longer. Mice bearing orthotopic tumors from patient derived xenografts / Group-3 MBL cells with diminished PRDX1 expression or PRDX1 inhibition by Adenanthin survived longer when compared to controls. We also correlated PRDX1 expression to patient outcomes in a validated Medulloblastoma tumor microarray (TMA). We performed next generation whole genome sequencing to identify pathways that are affected with PRDX1 inhibition or silencing. The results from these experiments will be presented. Our results suggest that PRDX1 is a therapeutic target in all sub-groups of medulloblastoma and Adenanthin could be used as a radio-sensitizer in the treatment of Group-3 MBLs.