Induction of protective T-helper 1 immune responses against Echinococcus granulosus in mice by a multi-T-cell epitope antigen based on five proteins

In this study, we designed an experiment to predict a potential immunodominant T-cell epitope and evaluate the protectivity of this antigen in immunised mice. The T-cell epitopes of the candidate proteins (EgGST, EgA31, Eg95, EgTrp and P14-3-3) were detected using available web-based databases. The synthesised DNA was subcloned into the pET41a+ vector and expressed in Escherichia coli as a fusion to glutathione-S-transferase protein (GST). The resulting chimeric protein was then purified by affinity chromatography. Twenty female C57BL/6 mice were immunised with the antigen emulsified in Freund's adjuvant. Mouse splenocytes were then cultured in Dulbecco's Modified Eagle's Medium in the presence of the antigen. The production of interferon-γ was significantly higher in the immunised mice than in the control mice (> 1,300 pg/mL), but interleukin (IL)-10 and IL-4 production was not statistically different between the two groups. In a challenge study in which mice were infected with 500 live protoscolices, a high protectivity level (99.6%) was demonstrated in immunised BALB/C mice compared to the findings in the control groups [GST and adjuvant (Adj) ]. These results demonstrate the successful application of the predicted T-cell epitope in designing a vaccine against Echinococcus granulosus in a mouse model.

A dynamic view of hepatitis C virus replication complexes.

Hepatitis C virus (HCV) replicates its genome in a membrane-associated replication complex (RC). Specific membrane alterations, designated membranous webs, represent predominant sites of HCV RNA replication. The principles governing HCV RC and membranous web formation are poorly understood. Here, we used replicons harboring a green fluorescent protein (GFP) insertion in nonstructural protein 5A (NS5A) to study HCV RCs in live cells. Two distinct patterns of NS5A-GFP were observed. (i) Large structures, representing membranous webs, showed restricted motility, were stable over many hours, were partitioned among daughter cells during cell division, and displayed a static internal architecture without detectable exchange of NS5A-GFP. (ii) In contrast, small structures, presumably representing small RCs, showed fast, saltatory movements over long distances. Both populations were associated with endoplasmic reticulum (ER) tubules, but only small RCs showed ER-independent, microtubule (MT)-dependent transport. We suggest that this MT-dependent transport sustains two distinct RC populations, which are both required during the HCV life cycle.

Discontinuation of enfuvirtide in heavily pretreated HIV-infected individuals.

BACKGROUND: Enfuvirtide was shown to be highly effective in treatment- experienced patients. Data on discontinuation of enfuvirtide and switch to new antiretroviral drugs are scarce. We aimed to evaluate the efficacy and the impact of discontinuing and/or switching enfuvirtide on virologic and clinical parameters in clinical practice. METHODS: All HIV-infected individuals participating in the Swiss HIV Cohort Study who were treated with enfuvirtide for at least 4 weeks in combination with an optimized background antiretroviral regimen were included in this study. RESULTS: A total of 151 patients were analyzed. The median baseline CD4 cell count was 108 cells/microL (interquartile range [IQR] 50-206) and HIV RNA was 4.7 log10 copies/mL (IQR 4.1-5.2). Virologic suppression, defined as a viral load below 50 copies/mL at 12 months, was achieved by 57.6% of patients. Overall, a median CD4 cell increase of 121 cells/microL (IQR 50-189) from baseline was noted. Up to 50% of patients discontinued enfuvirtide within the first year of treatment, mainly because of the patient's choice. After discontinuation of enfuvirtide, high rates of virologic failure and clinical progression were observed, notably when CD4 cell count at stopping enfuvirtide was below 100 cells/microL and no switch to new potent antiretroviral drugs such as darunavir, maraviroc, or raltegravir was performed. CONCLUSIONS: Enfuvirtide provides high virologic and immunologic response in treatment-experienced patients in the setting of clinical practice. Enfuvirtide should not be discontinued but should be replaced by new potent antiretrovirals, particularly in case of severe immunosuppression.

Phosphorylation of the Na,K-ATPase alpha-subunit by protein kinase A and C in vitro and in intact cells. Identification of a novel motif for PKC-mediated phosphorylation.

Na,K-ATPase is a potential target for regulatory phosphorylation by protein kinase A and C (PKA and PKC). To identify the phosphorylation sites, we have mutated the alpha 1-subunit of Bufo marinus in a highly conservative PKA and in 20 different PKC consensus sequences. The mutants were expressed in Xenopus oocytes and their phosphorylation capacity tested in homogenates upon stimulation of PKA or PKC. While serine 943 (Ser-943) was identified as a unique target site for PKA, none of the PKC consensus serine or threonine residues are implicated in PKC phosphorylation. Controlled trypsinolysis of phosphorylated alpha-subunits of various purified enzyme preparations and of alpha/beta complexes from oocyte homogenates revealed that PKC phosphorylation was exclusively associated with the N terminus. A fusion protein containing the first 32 amino acids of the Bufo alpha-subunit was phosphorylated in vitro and serine and threonine residues (Thr-15 and Ser-16) in this region were identified by site-directed mutagenesis as the PKC phosphorylation sites. Finally, the Bufo alpha-subunit was phosphorylated by protein kinases in transfected COS-7 cells. In intact cells, PKA stimulation induced phosphorylation exclusively on Ser-943 and PKC stimulation mainly on Thr-15 and Ser-16, which are contained in a novel PKC phosphorylation motif.

Antiviral activity of a small-molecule inhibitor of arenavirus glycoprotein processing by the cellular site 1 protease.

Arenaviruses merit interest as clinically important human pathogens and include several causative agents, chiefly Lassa virus (LASV), of hemorrhagic fever disease in humans. There are no licensed LASV vaccines, and current antiarenavirus therapy is limited to the use of ribavirin, which is only partially effective and is associated with significant side effects. The arenavirus glycoprotein (GP) precursor GPC is processed by the cellular site 1 protease (S1P) to generate the peripheral virion attachment protein GP1 and the fusion-active transmembrane protein GP2, which is critical for production of infectious progeny and virus propagation. Therefore, S1P-mediated processing of arenavirus GPC is a promising target for therapeutic intervention. To this end, we have evaluated the antiarenaviral activity of PF-429242, a recently described small-molecule inhibitor of S1P. PF-429242 efficiently prevented the processing of GPC from the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) and LASV, which correlated with the compound's potent antiviral activity against LCMV and LASV in cultured cells. In contrast, a recombinant LCMV expressing a GPC whose processing into GP1 and GP2 was mediated by furin, instead of S1P, was highly resistant to PF-429242 treatment. PF-429242 did not affect virus RNA replication or budding but had a modest effect on virus cell entry, indicating that the antiarenaviral activity of PF-429242 was mostly related to its ability to inhibit S1P-mediated processing of arenavirus GPC. Our findings support the feasibility of using small-molecule inhibitors of S1P-mediated processing of arenavirus GPC as a novel antiviral strategy.

Expression of mitofusin 2(R94Q) in a transgenic mouse leads to Charcot-Marie-Tooth neuropathy type 2A.

Charcot-Marie-Tooth disease type 2A is an autosomal dominant axonal form of peripheral neuropathy caused by mutations in the mitofusin 2 gene. Mitofusin 2 encodes a mitochondrial outer membrane protein that participates in mitochondrial fusion in mammalian cells. How mutations in this protein lead to Charcot-Marie-Tooth disease type 2A pathophysiology remains unclear. We have generated a transgenic mouse expressing either a mutated (R94Q) or wild-type form of human mitofusin 2 in neurons to evaluate whether the R94Q mutation was sufficient for inducing a Charcot-Marie-Tooth disease type 2A phenotype. Only mice expressing mitofusin 2(R94Q) developed locomotor impairments and gait defects thus mimicking the Charcot-Marie-Tooth disease type 2A neuropathy. In these animals, the number of mitochondria per axon was significantly increased in the distal part of the sciatic nerve axons with a diameter smaller than 3.5 microm. Importantly, the analysis of R94Q transgenic animals also revealed an age-related shift in the size of myelinated axons leading to an over-representation of axons smaller than 3.5 microm. Together these data suggest a link between an increased number of mitochondria in axons and a shift in axonal size distribution in mitofusin 2(R94Q) transgenic animals that may contribute to their neurological phenotype.

An autoregulatory loop controlling CYP1A1 gene expression: role of H(2)O(2) and NFI.

Cytochrome P450 1A1 (CYP1A1), like many monooxygenases, can produce reactive oxygen species during its catalytic cycle. Apart from the well-characterized xenobiotic-elicited induction, the regulatory mechanisms involved in the control of the steady-state activity of CYP1A1 have not been elucidated. We show here that reactive oxygen species generated from the activity of CYP1A1 limit the levels of induced CYP1A1 mRNAs. The mechanism involves the repression of the CYP1A1 gene promoter activity in a negative-feedback autoregulatory loop. Indeed, increasing the CYP1A1 activity by transfecting CYP1A1 expression vectors into hepatoma cells elicited an oxidative stress and led to the repression of a reporter gene driven by the CYP1A1 gene promoter. This negative autoregulation is abolished by ellipticine (an inhibitor of CYP1A1) and by catalase (which catalyzes H(2)O(2) catabolism), thus implying that H(2)O(2) is an intermediate. Down-regulation is also abolished by the mutation of the proximal nuclear factor I (NFI) site in the promoter. The transactivating domain of NFI/CTF was found to act in synergy with the arylhydrocarbon receptor pathway during the induction of CYP1A1 by 2,3,7,8-tetrachloro-p-dibenzodioxin. Using an NFI/CTF-Gal4 fusion, we show that NFI/CTF transactivating function is decreased by a high activity of CYP1A1. This regulation is also abolished by catalase or ellipticine. Consistently, the transactivating function of NFI/CTF is repressed in cells treated with H(2)O(2), a novel finding indicating that the transactivating domain of a transcription factor can be targeted by oxidative stress. In conclusion, an autoregulatory loop leads to the fine tuning of the CYP1A1 gene expression through the down-regulation of NFI activity by CYP1A1-based H(2)O(2) production. This mechanism allows a limitation of the potentially toxic CYP1A1 activity within the cell.

iNKT/CD1d-antitumor immunotherapy significantly increases the efficacy of therapeutic CpG/peptide-based cancer vaccine.

BACKGROUND: Therapeutic cancer vaccines aim to boost the natural immunity against transformed cancer cells, and a series of adjuvants and co-stimulatory molecules have been proposed to enhance the immune response against weak self-antigens expressed on cancer cells. For instance, a peptide/CpG-based cancer vaccine has been evaluated in several clinical trials and was shown in pre-clinical studies to favor the expansion of effector T versus Tregs cells, resulting in a potent antitumor activity, as compared to other TLR ligands. Alternatively, the adjuvant activity of CD1d-restricted invariant NKT cells (iNKT) on the innate and adaptive immunity is well demonstrated, and several CD1d glycolipid ligands are under pre-clinical and clinical evaluation. Importantly, additive or even synergistic effects have been shown upon combined CD1d/NKT agonists and TLR ligands. The aim of the present study is to combine the activation and tumor targeting of activated iNKT, NK and T cells. METHODS: Activation and tumor targeting of iNKT cells via recombinant α-galactosylceramide (αGC)-loaded CD1d-anti-HER2 fusion protein (CD1d-antitumor) is combined or not with OVA peptide/CpG vaccine. Circulating and intratumoral NK and H-2Kb/OVA-specific CD8 responses are monitored, as well as the state of activation of dendritic cells (DC) with regard to activation markers and IL-12 secretion. The resulting antitumor therapy is tested against established tumor grafts of B16 melanoma cells expressing human HER2 and ovalbumin. RESULTS: The combined CD1d/iNKT antitumor therapy and CpG/peptide-based immunization leads to optimized expansion of NK and OVA-specific CD8 T cells (CTLs), likely resulting from the maturation of highly pro-inflammatory DCs as seen by a synergistic increase in serum IL-12. The enhanced innate and adaptive immune responses result in higher tumor inhibition that correlates with increased numbers of OVA-specific CTLs at the tumor site. Antibody-mediated depletion experiments further demonstrate that in this context, CTLs rather than NK cells are essential for the enhanced tumor inhibition. CONCLUSIONS: Altogether, our study in mice demonstrates that αGC/CD1d-antitumor fusion protein greatly increases the efficacy of a therapeutic CpG-based cancer vaccine, first as an adjuvant during T cell priming and second, as a therapeutic agent to redirect immune responses to the tumor site.

Purification and characterization of two enantioselective alpha-ketoglutarate-dependent dioxygenases, RdpA and SdpA, from Sphingomonas herbicidovorans MH.

Alpha-ketoglutarate-dependent (R)-dichlorprop dioxygenase (RdpA) and alpha-ketoglutarate-dependent (S)-dichlorprop dioxygenase (SdpA), which are involved in the degradation of phenoxyalkanoic acid herbicides in Sphingomonas herbicidovorans MH, were expressed and purified as His6-tagged fusion proteins from Escherichia coli BL21(DE3)(pLysS). RdpA and SdpA belong to subgroup II of the alpha-ketoglutarate-dependent dioxygenases and share the specific motif HXDX(24)TX(131)HX(10)R. Amino acids His-111, Asp-113, and His-270 and amino acids His-102, Asp-104, and His 257 comprise the 2-His-1-carboxylate facial triads and were predicted to be involved in iron binding in RdpA and SdpA, respectively. RdpA exclusively transformed the (R) enantiomers of mecoprop [2-(4-chloro-2-methylphenoxy)propanoic acid] and dichlorprop [2-(2,4-dichlorophenoxy)propanoic acid], whereas SdpA was specific for the (S) enantiomers. The apparent Km values were 99 microM for (R)-mecoprop, 164 microM for (R)-dichlorprop, and 3 microM for alpha-ketoglutarate for RdpA and 132 microM for (S)-mecoprop, 495 microM for (S)-dichlorprop, and 20 microM for alpha-ketoglutarate for SdpA. Both enzymes had high apparent Km values for oxygen; these values were 159 microM for SdpA and >230 microM for RdpA, whose activity was linearly dependent on oxygen at the concentration range measured. Both enzymes had narrow cosubstrate specificity; only 2-oxoadipate was able to replace alpha-ketoglutarate, and the rates were substantially diminished. Ferrous iron was necessary for activity of the enzymes, and other divalent cations could not replace it. Although the results of growth experiments suggest that strain MH harbors a specific 2,4-dichlorophenoxyacetic acid-converting enzyme, tfdA-, tfdAalpha-, or cadAB-like genes were not discovered in a screening analysis in which heterologous hybridization and PCR were used.

Impact of Balanced or Unbalanced Karyotype At Diagnosis On Prognosis of CML: Long-Term Observation From 1346 Patients of the Randomized CML Study IV

Introduction: Acquired genetic instability in chronic myeloid leukemia (CML) as a consequence of the translocation t(9;22)(q34;q11) and the resulting BCR-ABL fusion causes the continuous acquisition of additional chromosomal aberrations and mutations and thereby progression to accelerated phase (AP) and blast crisis (BC). At least 10% of patients in chronic phase (CP) CML show additional alterations at diagnosis. This proportion rises during the course of the disease up to 80% in BC. Acquisition of chromosomal changes during treatment is considered as a poor prognostic indicator, whereas the impact of chromosomal aberrations at diagnosis depends on their type. Patients with major route additional chromosomal alterations (major ACA: +8, i(17)(q10), +19, +der(22)t(9;22)(q34;q11) have a worse outcome whereas patients with minor route ACA show no difference in overall survival (OS) and progression-free survival (PFS) compared to patients with the standard translocation, a variant translocation or the loss of the Y chromosome (Fabarius et al., Blood 2011). However, the impact of balanced vs. unbalanced (gains or losses of chromosomes or chromosomal material) karyotypes at diagnosis on prognosis of CML is not clear yet. Patients and methods: Clinical and cytogenetic data of 1346 evaluable out of 1544 patients with Philadelphia and BCR-ABL positive CP CML randomized until December 2011 to the German CML-Study IV, a randomized 5-arm trial to optimize imatinib therapy by combination, or dose escalation and stem cell transplantation were investigated. There were 540 females (40%) and 806 males (60%). Median age was 53 years (range, 16-88). The impact of additional cytogenetic aberrations in combination with an unbalanced or balanced karyotype at diagnosis on time to complete cytogenetic and major molecular remission (CCR, MMR), PFS and OS was investigated. Results: At diagnosis 1174/1346 patients (87%) had the standard t(9;22)(q34;q11) only and 75 patients (6%) had a variant t(v;22). In 64 of 75 patients with t(v;22), only one further chromosome was involved in the translocation; In 8 patients two, in 2 patients three, and in one patient four further chromosomes were involved. Ninety seven patients (7%) had additional cytogenetic aberrations. Of these, 44 patients (3%) lacked the Y chromosome (-Y) and 53 patients (4%) had major or minor ACA. Thirty six of the 53 patients (2.7%) had an unbalanced karyotype (including all patients with major route ACA and patients with other unbalanced alterations like -X, del(1)(q21), del(5)(q11q14), +10, t(15;17)(p10;p10), -21), and 17 (1.3%) a balanced karyotype with reciprocal translocations [e.g. t(1;21); t(2;16); t(3;12); t(4;6); t(5;8); t(15;20)]. After a median observation time of 5.6 years for patients with t(9;22), t(v;22), -Y, balanced and unbalanced karyotype with ACA median times to CCR were 1.05, 1.05, 1.03, 2.58 and 1.51 years, to MMR 1.31, 1.51, 1.65, 2.97 and 2.07 years. Time to CCR and MMR was longer in patients with balanced karyotypes (data statistically not significant). 5-year PFS was 89%, 78%, 87%, 94% and 69% and 5-year OS 91%, 87%, 89%, 100% and 73%, respectively. In CML patients with unbalanced karyotype PFS (p<0.001) and OS (p<0.001) were shorter than in patients with standard translocation (or balanced karyotype; p<0.04 and p<0.07, respectively). Conclusion: We conclude that the prognostic impact of additional cytogenetic alterations at diagnosis of CML is heterogeneous and consideration of their types may be important. Not only patients with major route ACA at diagnosis of CML but also patients with unbalanced karyotypes identify a group of patients with shorter PFS and OS as compared to all other patients. Therefore, different therapeutic options such as intensive therapy with the most potent tyrosine kinase inhibitors or stem cell transplantation are required.

Weighted Shape-based Averaging with Neighborhood Prior Model for Multiple Atlas Fusion-based Medical Image Segmentation

In medical imaging, merging automated segmentations obtained from multiple atlases has become a standard practice for improving the accuracy. In this letter, we propose two new fusion methods: "Global Weighted Shape-Based Averaging" (GWSBA) and "Local Weighted Shape-Based Averaging" (LWSBA). These methods extend the well known Shape-Based Averaging (SBA) by additionally incorporating the similarity information between the reference (i.e., atlas) images and the target image to be segmented. We also propose a new spatially-varying similarity-weighted neighborhood prior model, and an edge-preserving smoothness term that can be used with many of the existing fusion methods. We first present our new Markov Random Field (MRF) based fusion framework that models the above mentioned information. The proposed methods are evaluated in the context of segmentation of lymph nodes in the head and neck 3D CT images, and they resulted in more accurate segmentations compared to the existing SBA.

Overcoming the heterologous bias: an in vivo functional analysis of multidrug efflux transporter, CgCdr1p in matched pair clinical isolates of Candida glabrata.

We have taken advantage of the natural milieu of matched pair of azole sensitive (AS) and azole resistant (AR) clinical isolates of Candida glabrata for expressing its major ABC multidrug transporter, CgCdr1p for structure and functional analysis. This was accomplished by tagging a green fluorescent protein (GFP) downstream of ORF of CgCDR1 and integrating the resultant fusion protein at its native chromosomal locus in AS and AR backgrounds. The characterization confirmed that in comparison to AS isolate, CgCdr1p-GFP was over-expressed in AR isolates due to its hyperactive native promoter and the GFP tag did not affect its functionality in either construct. We observed that in addition to Rhodamine 6 G (R6G) and Fluconazole (FLC), a recently identified fluorescent substrate of multidrug transporters Nile Red (NR) could also be expelled by CgCdr1p. Competition assays with these substrates revealed the presence of overlapping multiple drug binding sites in CgCdr1p. Point mutations employing site directed mutagenesis confirmed that the role played by unique amino acid residues critical to ATP catalysis and localization of ABC drug transporter proteins are well conserved in C. glabrata as in other yeasts. This study demonstrates a first in vivo novel system where over-expression of GFP tagged MDR transporter protein can be driven by its own hyperactive promoter of AR isolates. Taken together, this in vivo system can be exploited for the structure and functional analysis of CgCdr1p and similar proteins wherein the artefactual concerns encountered in using heterologous systems are totally excluded.

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

Differential scanning calorimetry (DSC) was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis (EGA) has led to the identification of four dehydrogenation processes arising from polymeric chains (A), SiH groups at the surfaces of internal voids (A'), SiH groups at interfaces (B), and in the bulk (C). All of them are slightly exothermic with enthalpies below 50 meV/H atoms , indicating that, after dissociation of any SiH group, most dangling bonds recombine. The kinetics of the three low-temperature processes [with DSC peak temperatures at around 320 (A),360 (A'), and 430°C (B)] exhibit a kinetic-compensation effect characterized by a linea relationship between the activation entropy and enthalpy, which constitutes their signature. Their Si-H bond-dissociation energies have been determined to be E (Si-H)0=3.14 (A), 3.19 (A'), and 3.28 eV (B). In these cases it was possible to extract the formation energy E(DB) of the dangling bonds that recombine after Si-H bond breaking [0.97 (A), 1.05 (A'), and 1.12 (B)]. It is concluded that E(DB) increases with the degree of confinement and that E(DB)>1.10 eV for the isolated dangling bond in the bulk. After Si-H dissociation and for the low-temperature processes, hydrogen is transported in molecular form and a low relaxation of the silicon network is promoted. This is in contrast to the high-temperature process for which the diffusion of H in atomic form induces a substantial lattice relaxation that, for the conventional amorphous sample, releases energy of around 600 meV per H atom. It is argued that the density of sites in the Si network for H trapping diminishes during atomic diffusion

Influence of anatomical variations on lumbar foraminal stenosis pathogenesis.

INTRODUCTION: Symptomatic foraminal stenosis has been observed in patients with degenerative disc disease, scoliosis, asymmetrical disc degeneration and spondylolisthesis. Nevertheless not all patients with the above pathologies will develop symptomatic foraminal stenosis. We hypothesised that symptomatic patients have anatomical predisposition to foraminal stenosis, namely a larger pedicle height (PH) to vertebral body height (VH) ratio, leaving less room below the pedicle for the exiting nerve root compared to asymptomatic patients. PATIENT SAMPLE: 66 Patients were divided in two groups. The surgical group consisted of 37 patients (average age of 61 years) who presented with severe radicular symptoms resisting to conservative measures and requiring decompression and transforaminal lumbar interbody fusion (TLIF). The control group consisted of 29 patients (average age of 51 years) presenting with low back pain (LBP) but with no radicular symptoms and who were treated conservatively. METHODS: We measured VH at the level of the posterior wall as well as PH on parasagittal images (CT or MRI) on all lumbar levels (L1 to L5). Statistical analysis was performed using Student's t test. RESULTS: No difference in PH was found between the two groups for L1 to L4 levels. By contrast, there was a highly statistically significant difference in VH between the two groups from L1 to L4 level. In the surgical group, the VH was smaller (p < 0.001). CONCLUSIONS: Symptomatic patients with foraminal stenosis have smaller VH leading to lesser space beneath the pedicle and putting the exiting nerve root at risk in cases of spondylolisthesis or disc degeneration.

CD44 attenuates activation of the hippo signaling pathway and is a prime therapeutic target for glioblastoma.

Glioblastoma multiforme (GBM) is the most aggressive brain tumor that, by virtue of its resistance to chemotherapy and radiotherapy, is currently incurable. Identification of molecules whose targeting may eliminate GBM cells and/or sensitize glioblastoma cells to cytotoxic drugs is therefore urgently needed. CD44 is a major cell surface hyaluronan receptor and cancer stem cell marker that has been implicated in the progression of a variety of cancer types. However, the major downstream signaling pathways that mediate its protumor effects and the role of CD44 in the progression and chemoresponse of GBM have not been established. Here we show that CD44 is upregulated in GBM and that its depletion blocks GBM growth and sensitizes GBM cells to cytotoxic drugs in vivo. Consistent with this observation, CD44 antagonists potently inhibit glioma growth in preclinical mouse models. We provide the first evidence that CD44 functions upstream of the mammalian Hippo signaling pathway and that CD44 promotes tumor cell resistance to reactive oxygen species-induced and cytotoxic agent-induced stress by attenuating activation of the Hippo signaling pathway. Together, our results identify CD44 as a prime therapeutic target for GBM, establish potent antiglioma efficacy of CD44 antagonists, uncover a novel CD44 signaling pathway, and provide a first mechanistic explanation as to how upregulation of CD44 may constitute a key event in leading to cancer cell resistance to stresses of different origins. Finally, our results provide a rational explanation for the observation that functional inhibition of CD44 augments the efficacy of chemotherapy and radiation therapy.