mTORC2 Regulates Amino Acid Metabolism in Cancer by Phosphorylation of the Cystine-Glutamate Antiporter xCT.

Mutations in cancer reprogram amino acid metabolism to drive tumor growth, but the molecular mechanisms are not well understood. Using an unbiased proteomic screen, we identified mTORC2 as a critical regulator of amino acid metabolism in cancer via phosphorylation of the cystine-glutamate antiporter xCT. mTORC2 phosphorylates serine 26 at the cytosolic N terminus of xCT, inhibiting its activity. Genetic inhibition of mTORC2, or pharmacologic inhibition of the mammalian target of rapamycin (mTOR) kinase, promotes glutamate secretion, cystine uptake, and incorporation into glutathione, linking growth factor receptor signaling with amino acid uptake and utilization. These results identify an unanticipated mechanism regulating amino acid metabolism in cancer, enabling tumor cells to adapt to changing environmental conditions.

Glioblastoma cellular cross-talk converges on NF-κB to attenuate EGFR inhibitor sensitivity.

In glioblastoma (GBM), heterogeneous expression of amplified and mutated epidermal growth factor receptor (EGFR) presents a substantial challenge for the effective use of EGFR-directed therapeutics. Here we demonstrate that heterogeneous expression of the wild-type receptor and its constitutively active mutant form, EGFRvIII, limits sensitivity to these therapies through an interclonal communication mechanism mediated by interleukin-6 (IL-6) cytokine secreted from EGFRvIII-positive tumor cells. IL-6 activates a NF-κB signaling axis in a paracrine and autocrine manner, leading to bromodomain protein 4 (BRD4)-dependent expression of the prosurvival protein survivin (BIRC5) and attenuation of sensitivity to EGFR tyrosine kinase inhibitors (TKIs). NF-κB and survivin are coordinately up-regulated in GBM patient tumors, and functional inhibition of either protein or BRD4 in in vitro and in vivo models restores sensitivity to EGFR TKIs. These results provide a rationale for improving anti-EGFR therapeutic efficacy through pharmacological uncoupling of a convergence point of NF-κB-mediated survival that is leveraged by an interclonal circuitry mechanism established by intratumoral mutational heterogeneity.

EGFR Mutation Promotes Glioblastoma through Epigenome and Transcription Factor Network Remodeling.

Epidermal growth factor receptor (EGFR) gene amplification and mutations are the most common oncogenic events in glioblastoma (GBM), but the mechanisms by which they promote aggressive tumor growth are not well understood. Here, through integrated epigenome and transcriptome analyses of cell lines, genotyped clinical samples, and TCGA data, we show that EGFR mutations remodel the activated enhancer landscape of GBM, promoting tumorigenesis through a SOX9 and FOXG1-dependent transcriptional regulatory network in vitro and in vivo. The most common EGFR mutation, EGFRvIII, sensitizes GBM cells to the BET-bromodomain inhibitor JQ1 in a SOX9, FOXG1-dependent manner. These results identify the role of transcriptional/epigenetic remodeling in EGFR-dependent pathogenesis and suggest a mechanistic basis for epigenetic therapy.

mTORC2 links growth factor signaling with epigenetic regulation of iron metabolism in glioblastoma.

In cancer, aberrant growth factor receptor signaling reprograms cellular metabolism and global gene transcription to drive aggressive growth, but the underlying mechanisms are not well-understood. Here we show that in the highly lethal brain tumor glioblastoma (GBM), mTOR complex 2 (mTORC2), a critical core component of the growth factor signaling system, couples acetyl-CoA production with nuclear translocation of histone-modifying enzymes including pyruvate dehydrogenase and class IIa histone deacetylases to globally alter histone acetylation. Integrated analyses in orthotopic mouse models and in clinical GBM samples reveal that mTORC2 controls iron metabolisms via histone H3 acetylation of the iron-related gene promoter, promoting tumor cell survival. These results nominate mTORC2 as a critical epigenetic regulator of iron metabolism in cancer.

Eighty percent survival rate at 15 years for 1p/19q co-deleted oligodendroglioma treated with upfront chemotherapy irrespective of tumor grade.

INTRODUCTION: Chromosomes 1p/19q co-deletion is a robust molecular marker for the diagnosis of oligodendroglial tumors, and has been included in the 2016 WHO modified classification. Although treatment for oligodendroglioma is controversial, upfront chemotherapy is regarded as one of the treatment option for low-grade tumor. We have treated all the 1p/19q co-deleted oligodendrogliomas, both grades II and III, with upfront chemotherapy without conventional radiotherapy for 20 years. The clinical experience from this trial may be suggestive for understanding of the biological features of oligodendroglioma with 1p/19q co-deletion toward precision medicine. METHODS: This is a long-term retrospective data of the non-selected patients with 1p/19q co-deleted oligodendrogliomas uniformly treated with up-front chemotherapy. Seventy consecutive patients (48 with grade II and 22 with grade III tumors) were included. RESULTS: The median follow-up period was 13 years. The 5-, 10-, and 15-year progression-free survival (PFS) rates were 85.7%, 54.8%, and 31.5%, respectively, and the median PFS was 146 months. In most cases, tumor recurrence was remained local and could be controlled by salvage surgery and/or chemotherapy. The 5-, 10-, and 15-year overall survival (OS) rates were 96.8%, 88.7%, and 80.0%, respectively, and the median OS was not reached. These survival data compared favorably with previous large clinical studies employing radiotherapy. Tumor grades based on World Health Organization classification, extent of surgery, and age affected neither PFS nor OS. Most patients were able to return to their premorbid social life. CONCLUSIONS: The long-term results drawn from 20-years of single institution experience show that the patients with 1p/19q co-deleted oligodendrogliomas can be successfully treated with up-front chemotherapy alone without compromising OS.

Glucose-dependent acetylation of Rictor promotes targeted cancer therapy resistance.

Cancer cells adapt their signaling in response to nutrient availability. To uncover the mechanisms regulating this process and its functional consequences, we interrogated cell lines, mouse tumor models, and clinical samples of glioblastoma (GBM), the highly lethal brain cancer. We discovered that glucose or acetate is required for epidermal growth factor receptor vIII (EGFRvIII), the most common growth factor receptor mutation in GBM, to activate mechanistic target of rapamycin complex 2 (mTORC2) and promote tumor growth. Glucose or acetate promoted growth factor receptor signaling through acetyl-CoA-dependent acetylation of Rictor, a core component of the mTORC2 signaling complex. Remarkably, in the presence of elevated glucose levels, Rictor acetylation is maintained to form an autoactivation loop of mTORC2 even when the upstream components of the growth factor receptor signaling pathway are no longer active, thus rendering GBMs resistant to EGFR-, PI3K (phosphoinositide 3-kinase)-, or AKT (v-akt murine thymoma viral oncogene homolog)-targeted therapies. These results demonstrate that elevated nutrient levels can drive resistance to targeted cancer treatments and nominate mTORC2 as a central node for integrating growth factor signaling with nutrient availability in GBM.

IDH1 mutation is prognostic for diffuse astrocytoma but not low-grade oligodendrogliomas in patients not treated with early radiotherapy.

Despite accumulating knowledge regarding molecular backgrounds, the optimal management strategy for low-grade gliomas remains controversial. One reason is the marked heterogeneity in the clinical course. To establish an accurate subclassification of low-grade gliomas, we retrospectively evaluated isocitrate dehydrogenase-1 (IDH1) mutation in clinical specimens of diffuse astrocytomas (DA) and oligodendroglial tumors separately. No patients were treated with early radiotherapy, and modified PCV chemotherapy was used for postoperative residual tumors or recurrence in oligodendroglial tumors. Immunohistochemical evaluation of IDH status, p53 status, O(6)-methylguanine methyltransferase expression, and the MIB-1 index were performed. The 1p and 19q status was analyzed with fluorescence in situ hybridization. Ninety-four patients were followed for a median period of 8.5 years. For DAs, p53 was prognostic for progression- free survival (PFS) and IDH1 was significant for overall survival (OS) with multivariate analysis. In contrast, for oligodendroglial tumors, none of the parameters was significant for PFS or OS. Thus, the significance of IDH1 mutation is not clear in oligodendroglial tumors that are homogeneously indolent and chemosensitive. In contrast, DAs are heterogeneous tumors including some potentially malignant tumors that can be predicted by examining the IDH1 mutation status.

Non-deep-seated primary CNS lymphoma: therapeutic responses and a molecular signature.

The survival of patients with primary CNS lymphoma (PCNSL) has been improved by high-dose methotrexate (HD-MTX). Since the combination therapy of HD-MTX and whole-brain radiotherapy (WBRT) carries a significant risk for delayed neurotoxicity, it is important to know the therapeutic potential and prognostic factors for HD-MTX without WBRT. We retrospectively reviewed 46 consecutive patients with PCNSL treated with a HD-MTX (3.5 g/m(2)) and deferred WBRT. Patients who achieved complete response or partial response after three courses of HD-MTX were cautiously followed-up without additional treatment. Patients who had either stable disease, progressive disease, or disease relapse were offered salvage therapy. The median progression-free survival period was 10 months and the median overall survival period was 52 months, with a 5-year survival rate of 39 %. Nineteen patients (49 % of the evaluable patients) achieved a complete response at the initial response assessment. Involvement of deep structures of the brain (corpus callosum, basal ganglia and brainstem) was significantly associated with the worse progression-free survivals (p = 0.0058) and overall survivals (p = 0.0177). Gene expression profiling analysis by microarray was compared in eight patients between PCNSLs located in the deep structures of the brain and non-deep-seated tumors. The result showed that up-regulation of signal transduction-related genes and down-regulation of catalytic activity-related genes in the non-deep-seated PCNSL compared with the deep-seated tumors. The present study shows that PCNSL located in non-deep structures of the brain responds better to HD-MTX alone than those involved deep-structures.

Activin plays a key role in the maintenance of long-term memory and late-LTP.

A recent study has revealed that fear memory may be vulnerable following retrieval, and is then reconsolidated in a protein synthesis-dependent manner. However, little is known about the molecular mechanisms of these processes. Activin betaA, a member of the TGF-beta superfamily, is increased in activated neuronal circuits and regulates dendritic spine morphology. To clarify the role of activin in the synaptic plasticity of the adult brain, we examined the effect of inhibiting or enhancing activin function on hippocampal long-term potentiation (LTP). We found that follistatin, a specific inhibitor of activin, blocked the maintenance of late LTP (L-LTP) in the hippocampus. In contrast, administration of activin facilitated the maintenance of early LTP (E-LTP). We generated forebrain-specific activin- or follistatin-transgenic mice in which transgene expression is under the control of the Tet-OFF system. Maintenance of hippocampal L-LTP was blocked in the follistatin-transgenic mice. In the contextual fear-conditioning test, we found that follistatin blocked the formation of long-term memory (LTM) without affecting short-term memory (STM). Furthermore, consolidated memory was selectively weakened by the expression of follistatin during retrieval, but not during the maintenance phase. On the other hand, the maintenance of memory was also influenced by activin overexpression during the retrieval phase. Thus, the level of activin in the brain during the retrieval phase plays a key role in the maintenance of long-term memory.

Predicting Potential of Rapid Tumor Growth in Small to Medium Vestibular Schwannomas on the Basis of Sway Assessed Using Posturography.

OBJECTIVE: The relationship between quantitative posturography results and growth of vestibular schwannomas (VSs) during conservative management has not been studied. We aimed to clarify the relationship between the presence of disequilibrium based on posturographic measurement and VS growth. METHODS: This retrospective, single-center study included 53 patients with VSs (Koos stage I or II) managed conservatively after initial diagnosis. Radiographic progression was considered present if 20% volumetric growth was observed over the imaging interval. Posturography was performed at initial diagnosis, and sway velocity (SV) and sway area were calculated. Tumor growth-free survival was estimated using the Kaplan-Meier method. RESULTS: Mean follow-up period was 2.87 ± 2.58 years, up to tumor growth detection or last follow-up magnetic resonance imaging. Tumor growth incidence was 40.8% and 61.2% at 2 and 5 years, respectively. Cerebellopontine angle extension and SV with eyes open were related to tumor growth. Tumor growth-free survival of patients with cerebellopontine angle extension and patients with intracanalicular tumor at 2 years was 37.3% and 76.4%, respectively. Tumor growth-free survival of patients with SV >2.06 cm/second and patients with SV ≤2.06 cm/second at 2 years was 30.8% and 68.9%, respectively. The Cox hazard model demonstrated a significant risk for future tumor growth with SV >2.06 cm/second (relative risk, 2.475; 95% confidence interval, 1.11-5.37, P = 0.027). CONCLUSIONS: We demonstrated a positive correlation between SV with eyes open and future tumor growth. Posturographic data are objective and quantitative; thus, SV may be a potential predictor of future growth of VSs.

Metastasis of Renal Cell Carcinoma to Spinal Hemangioblastoma in a Patient with von Hippel-Lindau Disease: A Case Report.

von Hippel-Lindau (VHL) disease is characterized by neoplastic and cystic lesions, such as central nervous system (CNS) hemangioblastoma and clear cell renal cell carcinoma (RCC), arising in multiple organs. Here, we report a case of an RCC that metastasized to a spinal hemangioblastoma in a patient diagnosed with VHL disease. This is a unique case study because visceral neoplasms rarely metastasize to the CNS. The patient had undergone posterior fossa surgery for the removal of hemangioblastomas in the right cerebellar hemisphere as a child. He was diagnosed with RCC at the age of 20 years, and he underwent partial nephrectomy at the age of 35 years. The patient underwent surgical removal of a spinal tumor from Th8, which was also diagnosed as a hemangioblastoma at the age of 40. However, the residual spinal tumor rapidly regrew within 1.5 years. A second surgery was performed due to progressive leg motor weakness. The resected tumor from the second surgery had two distinct components between the tumor center and the margin. Immunohistochemistry of CD10, PAX 8, and inhibin A demonstrated the predominant region of the tumor was RCC. Pathological findings confirmed tumor-to-tumor metastasis of the RCC migrating into residual spinal hemangioblastoma. It can be challenging to distinguish hemangioblastoma from RCC in neuroimaging. We suggest that tumor-to-tumor metastasis should be considered as a differential diagnosis if benign tumors grow rapidly, even if the pathological diagnosis does not initially confirm malignancy. The biological mechanisms of RCC migrating into residual hemangioblastoma are discussed.

Postoperative Cerebellar Cyst with Pseudomeningocele After Tumor Removal at the Craniovertebral Junction.

BACKGROUND: Cerebellar cyst formation after surgery is uncommon, and few cases of this condition have been previously reported. These cases had an intraparenchymal cyst in the cerebellar hemisphere that required surgical fenestration of the cyst. We herein present a rare case of a postoperative cerebellar cyst with pseudomeningocele and magnetic resonance images indicating a fistula between the cyst and pseudomeningocele. CASE DESCRIPTION: A patient presented with an intraparenchymal cyst and surrounding edema in the cerebellar hemisphere that developed after a C1 laminectomy and a small suboccipital craniectomy for the removal of an accessory nerve neurinoma at the craniovertebral junction. Fast imaging employing steady-state acquisition images identified the fistula connecting the cyst and extradural cerebrospinal fluid retention. Conservative management with administration of dexamethasone induced spontaneous regression of the cyst, and no recurrence had occurred by the 1-year follow-up. CONCLUSIONS: Watertight dural closure is important for the prevention of this rare complication after posterior fossa surgery. However, an arachnoid tear on the cerebellar fissure and adjacent dural defect are necessary antecedents for this rare condition. High-resolution fast imaging employing steady-state acquisition images could provide additional information for the etiology of postoperative cerebellar cyst.

Mechanism of Corpus Callosum Infarction Associated with Acute Hydrocephalus: Clinical, Surgical, and Radiological Evaluations for Pathophysiology.

BACKGROUND: Corpus callosum (CC) infarction has been reported to be rare because of the rich blood supply in the CC. The pathophysiology of CC infarction associated with acute hydrocephalus is unknown. The aim of the present study was to clarify the characteristics and mechanism of CC infarction associated with acute noncommunicating hydrocephalus (ANCH). METHODS: We reviewed clinical the data from all patients who had undergone surgical intervention for ANCH at Chiba University Hospital from January 2008 to March 2018. Patients with vascular lesions, a history of hydrocephalus, and lacking magnetic resonance imaging studies were excluded. The clinical, surgical, and radiological parameters were obtained retrospectively for pathophysiological analysis. RESULTS: A total of 23 patients with ANCH who had undergone surgical intervention and had met the inclusion criteria were included in the present study. Of the 23 patients, 6 (23%) had developed CC infarction. All CC infarctions were located in the splenium. Although no clinical or surgical features were associated with splenial infarction, the radiological parameters of lateral ventricle enlargement and a narrower callosal angle at the posterior commissure and the foramen of Monro were significantly associated with splenial infarction. CONCLUSION: The present study has presented evidence that increased intraventricular pressure by ANCH applied transversely in the splenium will directly induce compression of the superior branch of the posterior callosal artery and pericallosal pial plexus, resulting in splenium-specific infarction in patients with ANCH.

Unilateral Occipital Transtentorial Approach with Multimodal Assistance for Resection of Large Supracerebellar Hemangioblastomas: Preliminary Experience of 2 Cases.

BACKGROUND: The surgical resection of large supracerebellar hemangioblastomas (SHBs) is exceptionally challenging due to their vascularity and deep anatomic location and is associated with a high risk of postoperative complications and mortality. Access to the posterior incisural space can be achieved by either an infratentorial supracerebellar approach or occipital transtentorial approach (OTA). However, the optimal surgical strategy has not yet been established. Here, we report 2 cases of large SHBs that were successfully and safely resected via a unilateral OTA with multimodal assistance. CASE DESCRIPTION: Two patients presented to our hospital with ataxia due to large, solid SHBs. After preoperative embolization, gross total resection of the SHBs was achieved via an OTA. Furthermore, endoscopic assistance was used to resect the remnant portion of the tumor in the second patient. Both patients experienced transient ataxia but were discharged from the hospital without serious complications. CONCLUSIONS: The combination of an OTA with preoperative embolization and endoscopic assistance may reduce the intraoperative risk and contribute to improved outcome in patients with such clinically challenging tumors.

Photo-immune therapy with liposomally formulated phospholipid-conjugated indocyanine green induces specific antitumor responses with heat shock protein-70 expression in a glioblastoma model.

Glioblastoma (GBM) is the most common malignant brain tumor, and infiltrates into the surrounding normal brain tissue. Induction of a tumor-specific immune response is one of the best methods to obtain tumor-specific cytotoxicity. Photodynamic therapy (PDT) is known to effectively induce an antitumor immune response. We have developed a clinically translatable nanoparticle, liposomally formulated phospholipid-conjugated indocyanine green (LP-iDOPE), applicable for PDT. This nanoparticle accumulates in tumor tissues by the enhanced permeability and retention effect, and releases heat and singlet oxygen to injure cancer cells when activated by near infrared (NIR) light. We assessed the effectiveness of the LP-iDOPE system in brain using the rat 9L glioblastoma model. Treatment with LP-iDOPE and NIR irradiation resulted in significant tumor growth suppression and prolongation of survival. Histopathological examination showed induction of both apoptosis and necrosis and accumulation of CD8+ T-cells and macrophages/microglia accompanied by marked expressions of heat shock protein-70 (HSP70), which was not induced by mild hyperthermia alone at 45° C or an interleukin-2-mediated immune reaction. Notably, the efficacy was lost in immunocompromised nude rats. These results collectively show that the novel nanoparticle LP-iDOPE in combination with NIR irradiation can efficiently induce a tumor-specific immune reaction for malignant gliomas possibly by inducing HSP70 expression which is known to activate antigen-presenting cells through toll-like receptor signaling.

Oncogene Amplification in Growth Factor Signaling Pathways Renders Cancers Dependent on Membrane Lipid Remodeling.

Advances in DNA sequencing technologies have reshaped our understanding of the molecular basis of cancer, providing a precise genomic view of tumors. Complementary biochemical and biophysical perspectives of cancer point toward profound shifts in nutrient uptake and utilization that propel tumor growth and major changes in the structure of the plasma membrane of tumor cells. The molecular mechanisms that bridge these fundamental aspects of tumor biology remain poorly understood. Here, we show that the lysophosphatidylcholine acyltransferase LPCAT1 functionally links specific genetic alterations in cancer with aberrant metabolism and plasma membrane remodeling to drive tumor growth. Growth factor receptor-driven cancers are found to depend on LPCAT1 to shape plasma membrane composition through enhanced saturated phosphatidylcholine content that is, in turn, required for the transduction of oncogenic signals. These results point to a genotype-informed strategy that prioritizes lipid remodeling pathways as therapeutic targets for diverse cancers.

Tau phosphorylation in the mouse brain during aversive conditioning.

Stress response is intimately involved in memory formation. Stress has been shown to cause reversible Alzheimer-like tau phosphorylation in the brain of experimental animals, but it is not known whether tau phoshorylation takes place during memory acquisition. As an initial investigation we chose contextual fear conditioning paradigm involving electric shocks, and studied tau phosphorylation in the hippocampus and a neighboring limbic region of the mouse brain. Quantitative immunoblot analyses of tissue extracts rapidly prepared from animals undergoing the conditioning showed statistically significant increases in the phosphorylation level at Thr231/Ser235 of tau in both tissues. The reaction reached statistical significance after 10 but not 3 shocks of 0.8mA. Ten shocks of 0.2mA were ineffective. Concurrent increases in phosphorylation of protein kinase TPKI/GSK3beta at Ser9 and of CaMKIIalpha at Thr286 were observed. These results suggest involvement of tau and TPKI/GSK3beta phosphorylation in an early phase of memory formation in the hippocampus and amygdala, raising a possibility that a dysregulation of tau phosphorylation may underlie memory impairment in incipient Alzheimer's disease.

Functional analysis of basic transcription element binding protein by gene targeting technology.

Basic transcription element binding protein (BTEB) is a transcription factor with a characteristic zinc finger motif and is most remarkably enhanced by thyroid hormone T(3) treatment (R. J. Denver et al., J. Biol. Chem. 272:8179-8188, 1997). To investigate the function of BTEB per se and to touch on the effects of T(3) (3,5,3'-triiodothyronine) on mouse development, we generated BTEB-deficient mice by gene knockout technology. Homologous BTEB(-/-) mutant mice were bred according to apparently normal Mendelian genetics, matured normally, and were fertile. Mutant mice could survive for at least 2 years without evident pathological defects. From the expression of lacZ, which was inserted into the reading frame of the BTEB gene, BTEB showed a characteristic tissue-specific expression profile during the developmental process of brain and bone. Dramatically increased expression of BTEB was observed in Purkinje cells of the cerebellum and pyramidal cell layers of the hippocampus at P7 when synapses start to form in the brain. Although general behavioral activities such as locomotion, rearing, and speed of movement were not so much affected in the BTEB(-/-) mutant mice, they showed clearly reduced activity levels in rotorod and contextual fear-conditioning tests; this finding was probably due to defective functions of the cerebellum, hippocampus, and amygdala.

Novel use of cross-linked poly(N-isopropylacrylamide) gel for organic reactions in aqueous media.

A poly(N-isopropylacrylamide) (PNIPAAm) gel cross-linked with quaternized aminoalkyls was designed. A novel recyclable system based on the external solvent-responsive oil-absorption/elution transition ability of the PNIPAAm gel matrix was then developed.

Reduced pain sensitivity in mice lacking latexin, an inhibitor of metallocarboxypeptidases.

Latexin, the endogenous protein inhibitor of the A/B subfamily of metallocarboxypeptidases, is expressed in small nociceptive neurons in sensory ganglia and in a subset of neurons in the telencephalon. In this study, we generated latexin-deficient mice that exhibited increased tail-flick latency compared to wild-type animals upon noxious heat stimulation. The reduced pain sensitivity in the mutants was rescued by the systemic administration of a plant carboxypeptidase inhibitor that inhibits the A/B subfamily of metallocarboxypeptidases. These findings suggest that latexin is involved in the transmission of pain.