Driver Mutations Dictate the Immunologic Landscape and Response to Checkpoint Immunotherapy of Glioblastoma

The composition of the tumor immune microenvironment (TIME) is considered a key determinant of patients' response to immunotherapy. The mechanisms underlying TIME formation and development over time are poorly understood. Glioblastoma (GBM) is a lethal primary brain cancer for which there are no curative treatments. GBMs are immunologically heterogeneous and impervious to checkpoint blockade immunotherapies. Utilizing clinically relevant genetic mouse models of GBM, we identified distinct immune landscapes associated with expression of EGFR wild-type and mutant EGFRvIII cancer driver mutations. Over time, accumulation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) was more pronounced in EGFRvIII-driven GBMs and was correlated with resistance to PD-1 and CTLA-4 combination checkpoint blockade immunotherapy. We determined that GBM-secreted CXCL1/2/3 and PMN-MDSC-expressed CXCR2 formed an axis regulating output of PMN-MDSCs from the bone marrow leading to systemic increase in these cells in the spleen and GBM tumor-draining lymph nodes. Pharmacologic targeting of this axis induced a systemic decrease in the numbers of PMN-MDSC, facilitated responses to PD-1 and CTLA-4 combination checkpoint blocking immunotherapy, and prolonged survival in mice bearing EGFRvIII-driven GBM. Our results uncover a relationship between cancer driver mutations, TIME composition, and sensitivity to checkpoint blockade in GBM and support the stratification of patients with GBM for checkpoint blockade therapy based on integrated genotypic and immunologic profiles.

Intracranial Metastasis of Extracranial Chondrosarcoma: Systematic Review With Illustrative Case

BACKGROUND

Cerebral chondrosarcoma metastases are rare and aggressive neoplasms. The rarity of presentation has precluded rigorous analysis of diagnosis, risk factors, treatment, and survival. We analyzed every reported case through exhaustive literature review. We further present the first case with Maffucci syndrome.

METHODS

Three databases, PubMed, Embase, and Google Scholar, and crossed references were queried for cerebral chondrosarcoma metastases. Extracted variables included demographics, risk factors, tumor characteristics, interventions, and outcomes. Univariate and multivariate analyses were performed.

RESULTS

Fifty-six patients were included from 1,489 literature results. The average age at brain metastasis was 46.6±17.6 years and occurred at a median of 24±2.8 months from primary diagnosis. Primary tumor histology (dedifferentiated 5.0±1.5 months, mesenchymal 24±3.0 months, conventional 41±7.4 months, p<0.05) and grade (low grade 54±16.7 months vs. high-grade 10±6.4 months, p<0.001) correlated with time interval until brain metastasis. A multiple enchondromatosis syndrome occurred in 13.2% of cases. At time of brain metastases diagnosis, extracranial metastases were identified in 76.2% of cases. Median survival after the development of brain metastasis was 2.0±0.78 months with a 1-year survival of 10.0%. On regression analysis, surgery reduced brain metastasis mortality risk and radiation trended towards reduced mortality risk (surgery: hazard ratio [HR] 0.22, 95% confidence interval [CI] 0.064-0.763, p=0.017; radiation: HR 0.31, 95% CI 0.091-1.072, p=0.064).

CONCLUSION

We present a systematic review of cerebral chondrosarcoma metastases. Primary tumor histology and grade correlate with time until cerebral metastasis. Following cerebral metastasis, these tumors have poor prognosis and modestly benefit from surgery.

Inhibition of the epigenetically activated miR-483-5p/IGF-2 pathway results in rapid loss of meningioma tumor cell viability

PURPOSE

Meningioma is the most common primary central nervous system tumor often causing serious complications, and presently no medical treatment is available. The goal of this study was to discover miRNAs dysregulated in meningioma, and explore miRNA-associated pathways amenable for therapeutic interventions.

METHODS

Small RNA sequencing was performed on meningioma tumor samples to study grade-dependent changes in microRNA expression. Gene expression was analyzed by chromatin marks, qRT-PCR and western blot. miRNA modulation, anti-IGF-2 neutralizing antibodies, and inhibitors against IGF1R were evaluated in a tumor-derived primary cultures of meningioma cells.

RESULTS

Meningioma tumor samples showed high, grade-dependent expression of miR-483-5p, associated with high mRNA and protein expression of its host gene IGF-2. Inhibition of miR-483-5p reduced the growth of cultured meningioma cells, whereas a miR-483 mimic increased cell proliferation. Similarly, inhibition of this pathway with anti-IGF-2 neutralizing antibodies reduced meningioma cell proliferation. Small molecule tyrosine kinase inhibitor blockade of the IGF-2 receptor (IGF1R) resulted in rapid loss of viability of cultured meningioma tumor-derived cells, suggesting that autocrine IGF-2 feedback is obligatory for meningioma tumor cell survival and growth. The observed IGF1R-inhibitory IC50 for GSK1838705A and ceritinib in cell-based assays along with the available pharmacokinetics data predicted that effective drug concentration could be achieved in vivo as a new medical treatment of meningioma.

CONCLUSION

Meningioma cell growth is critically dependent on autocrine miR-483/IGF-2 stimulation and the IGF-2 pathway provides a feasible meningioma treatment target.

Cytogenetic and Molecular Characterization of IDH-Wildtype Glioblastomas and Grade 4 IDH-Mutant Astrocytomas with Unusual Histology

Glioblastoma (GBM) is a highly heterogenous tumor. Though several well-defined histological patterns of GBMs are known, these are infrequent, and the molecular correlates of several of these histological patterns are not well understood. We identified 31 adult-type infiltrating grade 4 gliomas with unusual histology in our institutional archives from 2016 to 2020, including tumors with a preponderant component of giant cell (n = 15), gemistocytes (n = 6), spindle cells (n = 5), small cells (n = 3), and ependymoma-like features (n = 2). We performed molecular and cytogenetic profiles of IDH-wildtype GBMs with unusual histology and compared to 48 tumors with conventional histology. We found that the majority (85%) of giant cell GBM had increased numbers of whole chromosome loss and genomic haploidization compared to conventional GBMs and other variants. Furthermore, we identified a genetically confirmed GBM with prominent ependymal features, indicating that glial tumors with ependymal features should be considered in the differential diagnosis of GBM. We also identified 6 IDH-mutant grade 4 astrocytomas with unusual histology and similar molecular and cytogenetic profiles to conventional appearing grade 4 IDH-mutant astrocytomas. These findings emphasize the role of molecular/cytogenetic analyses in the diagnostic clarification of GBMs with unusual histological patterns, refine the classification of unusual GBMs, and potentially pave the way for personalized therapies.

Cerebral Metastases in Appendiceal Cancer: Comprehensive Review and Report of Rare Medullary Carcinoma Histology

Appendiceal cancer is an extremely rare malignancy, and its metastatic spread to the brain is even more unusual. We describe a 47-year-old female who presented with a rare cerebral appendiceal carcinoma metastasis, a case that is further remarkable for representing the first histologic diagnosis of primary medullary carcinoma in the appendix. Based on a comprehensive review of the English literature using PubMed, Embase, and Google Scholar, only six other cases of cerebral appendiceal metastases have been described.

Primary Central Nervous System Anaplastic Large Cell Lymphoma, ALK Positive

OBJECTIVES

Primary central nervous system anaplastic large cell lymphoma, anaplastic lymphoma kinase positive (primary CNS ALCL, ALK+) is a rare CNS lymphoma whose description is limited to case reports. These tumors have a variable clinical course, and prognosis is primarily determined by age. We present the largest case series to date of primary CNS ALCL, ALK+, with observational data.

METHODS

A retrospective search of multiple academic centers was performed to identify cases of primary CNS ALCL, ALK+. We also performed a review of published cases of primary CNS ALCL, ALK+. Clinical history, radiography, pathology, and genetic testing data were obtained to determine the prognostic implications in the context of clinical course.

RESULTS

We identified three cases of primary CNS ALCL, ALK+ from our databases. A literature review identified 30 published reports of 31 individual cases. Clinical features for the combined 34 cases included a median age of 18.5 years, with a male to female ratio of 4.7:1, and the most common symptom was headache. Genetic studies demonstrated an ALK rearrangement by fluorescence in situ hybridization, and a gene fusion assay confirmed an NPM1-ALK gene fusion in one case.

CONCLUSIONS

We present the largest case series to date of a rare primary CNS lymphoma with additional diagnostic and clinical information.

Tumor-Derived Cell Culture Model for the Investigation of Meningioma Biology

Meningioma is the most common primary central nervous system tumor. Although mostly nonmalignant, meningioma can cause serious complications by mass effect and vasogenic edema. While surgery and radiation improve outcomes, not all cases can be treated due to eloquent location. Presently no medical treatment is available to slow meningioma growth owing to incomplete understanding of the underlying pathology, which in turn is due to the lack of high-fidelity tissue culture and animal models. We propose a simple and rapid method for the establishment of meningioma tumor-derived primary cultures. These cells can be maintained in culture for a limited time in serum-free media as spheres and form adherent cultures in the presence of 4% fetal calf serum. Many of the tissue samples show expression of the lineage marker PDG2S, which is typically retained in matched cultured cells, suggesting the presence of cells of arachnoid origin. Furthermore, nonarachnoid cells including vascular endothelial cells are also present in the cultures in addition to arachnoid cells, potentially providing a more accurate tumor cell microenvironment, and thus making the model more relevant for meningioma research and high-throughput drug screening.

Progressive Multifocal Leukoencephalopathy After Chimeric Antigen Receptor T-Cell Therapy for Recurrent Non-Hodgkin Lymphoma

Chimeric antigen receptor (CAR) T-cell therapy targeting cluster of differentiation (CD)19 has had a transformative impact on patient outcomes in a subset of patients with relapsed/refractory non-Hodgkin lymphoma. We present a patient with refractory large B-cell lymphoma in complete remission for 2 years following treatment with CD19-targeted CAR T-cell therapy, who presented with 2 weeks of progressive aphasia. Imaging revealed a left occipital brain lesion and biopsy demonstrated features diagnostic of progressive multifocal leukoencephalopathy. Further evaluation revealed severe hypogammaglobulinemia and a low CD4 count. She was treated with pembrolizumab and intravenous immunoglobulin resulting in decreased cerebrospinal fluid viral load without clinical improvement and died 8 weeks after presentation. This case highlights that there is potential for severe opportunistic infections after CAR T-cell therapy, including fatal progressive multifocal leukoencephalopathy. Strategies to enhance post-treatment immune reconstitution are essential to further harness the unique potency of CAR T-cell therapy.

Prognostic factors in Tumefactive demyelinating lesions: A retrospective study

INTRODUCTION

Demyelinating lesions occasionally present as mass-like lesions on imaging, raising concern for malignancy. The disease course of such tumefactive demyelinating lesions (TDLs) is still being defined.

METHODS

We retrospectively analyzed 21 patients with new-onset neurologic symptoms and mass-like lesions on brain magnetic resonance imaging (MRI), which resulted in biopsy-proven diagnoses of demyelination. 18 patients had a median follow-up of 52 months. The clinical, radiologic and histologic features were associated with disease course.

RESULTS

An aggressive disease course (ADC) was noted in 33% of the patients and was associated with an initial largest lesion size ≥35 mm (p = 0.0007), mass effect (p = 0.01) and perilesional edema (p = 0.01) on MRI. Age 30 years and older, at presentation (p = 0.05), as well as the absence of a prior tonsillectomy (p = 0.0128) were also associated with an ADC.

CONCLUSIONS

We identified several factors, including initial larger lesion size, mass effect and perilesional edema on MRI, presentation after 30 years of age and the absence of a prior tonsillectomy, that predict an ADC in patients presenting with TDLs. These predictors of disease course can help guide patient follow-up and stratification for intervention.

Green Discoloration of Human Postmortem Brains: Etiologies and Mechanisms of Discoloration

ABSTRACT

A variety of gross discolorations of human postmortem brains is occasionally encountered and can have diagnostic implications. We describe 3 cases of green discoloration of the human brain observed on postmortem examination. Two patients who succumbed shortly after administration of methylene blue (MB) showed diffuse green discoloration that was detectable as early as 24 hours and was seen for at least 48 hours after MB administration. Green discoloration was largely in cortical and deep gray matter structures with relative sparing of the white matter. In contrast, a patient with severe hyperbilirubinemia who died after intracerebral hemorrhage showed localized bright green bile stained brain parenchyma in the areas surrounding the hemorrhage. We highlight the distinct patterns of discoloration in different causes of green brain discoloration, including MB, bile staining, and hydrogen sulfide poisoning. Recognition of these patterns by practicing pathologists can be used to differentiate between these etiologies and allow correct interpretation in both the medical and forensic autopsy settings.

Neuroglial heterotopia of the middle ear: A case series and systematic literature review

Background

The differential diagnosis for mass forming lesions of the middle ear is broad. While uncommon, neuroglial heterotopias can occur in the middle ear and can be a source of diagnostic confusion for clinician, radiologist, and pathologist alike.

Methods

We identified three cases of neuroglial heterotopia of the middle ear in our institutional archives from 2000 to 2020 and performed extensive histological and immunohistochemical characterization of the three lesions. We conducted a systematic literature review to identify 27 cases published in the English literature between the years 1980 and 2020. Only cases with histological verification of neuroglial heterotopia specifically involving the middle ear were included. We compiled the clinical, radiological, and histopathological findings for all 30 cases.

Results

Patients most frequently presented with chronic otitis media (40%), hearing loss (40%), or prior history of ear surgery or trauma (13%). The median age at surgery was 49 years with a male predominance (M:F 2:1); however, a bimodal age distribution was noted with an earlier onset (11 years or younger) in a subset of patients. Immunohistochemical characterization showed mature neuronal and reactive glial populations with low Ki67 proliferation index and chronic inflammatory infiltrates. There was no neuronal dysplasia or glial atypia, consistent with benign, nonneoplastic, mature glioneuronal tissue.

Conclusion

Immunohistochemical characterization of these lesions and clinical follow-up confirms their benign natural history. Potential etiologies include developmental misplacement, trauma, and chronic inflammation/ reactive changes resulting in sequestered encephalocele.

A case of statin-associated immune-mediated necrotizing myopathy with atypical biopsy features

Statin-associated immune-mediated necrotizing myopathy (IMNM) is a rare presentation of a statin-associated myopathy. Patients usually present with muscle weakness and pain in the setting of statin use with elevated creatine kinase (CK) levels and a positive anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody. Muscle biopsies typically show necrosis, CD68+ macrophages, and minimal lymphocytes. We present a case of a 67-year-old woman who had 2 months of progressive weakness and bilateral lower extremity pain after initiating atorvastatin therapy with symptoms persisting after statin cessation. She was found to have high anti-HMGCR antibody titers, and the biopsy of the rectus femoris muscle showed a prominent endomysial inflammatory cell infiltrate with necrotic and regenerative fibers and an atypical extensive inflammatory infiltrate composed of both CD4+ helper T cells and CD8+ cytotoxic T cells. She showed symptom resolution and normalization of CK levels and inflammatory markers with treatment involving a prolonged prednisone taper and a brief course of azathioprine, which was stopped because of the adverse effects.

GCB-type is a favorable prognostic factor in primary CNS diffuse large B-cell lymphomas

Primary CNS lymphomas (PCNSLs) are aggressive diffuse large B-cell lymphomas (DLBCLs) limited to the CNS that generally have a poor prognosis. Classification of DLBCL into germinal center B-cell (GCB) and activated B-cell (non-GCB) subtypes has prognostic value in systemic DLBCL, with GCB-type having a better prognosis. The aim of this study was to determine whether GCB versus non-GCB classification in PCNSLs has similar prognostic value. We analyzed clinical, radiological and histologic data from 24 patients with biopsy confirmed DLBCL of the CNS with classification into GCB versus non-GCB subtypes. We found that after a median follow-up of 15 months, only 39% of patients with non-GCB-type PCNS DLBCL were alive, whereas all patients with GCB-type were alive. Non-GCB-type had a median survival of 11 months, whereas all GCB-type patients were alive after a median follow-up of 22 months. As previously reported, we also found that patients younger than 70 years had longer survival (median 29 months) compared to older patients (median 8.8 months). There was no statistically significant difference between the ages, gender, focality, size or location of lesions, or treatment of non-GCB and GCB-type patients. Our findings suggest that classifying PCNSLs into GCB versus non-GCB subtype using the Hans algorithm may help stratify patients into two groups with different prognosis.

Multiple Whole Chromosomal Gains Define Angiomatous Meningiomas and Are Absent From the Tumor Vasculature

Angiomatous meningioma is a variant with prominent vascularity that can mimic other highly vascularized tumors and present diagnostic challenges. Unlike most meningioma variants, where NF2 gene loss on chromosome 22 is the most common genetic abnormality, angiomatous meningiomas are unique in having multiple whole chromosome gains (polysomies). We analyzed 38 meningiomas, 9 angiomatous (including 2 atypical and 1 anaplastic), and 29 nonangiomatous meningiomas, using array comparative genomic hybridization (aCGH). Angiomatous meningiomas showed multiple chromosomal alterations including polysomies and copy neutral loss of heterozygosity in comparison to nonangiomatous variants. The most frequent gains were of chromosomes 5 and 20 (100% and 89% of cases, respectively); none showed chromosome 22 loss. Furthermore, using fluorescence in situ hybridization we show that the vasculature lacked chromosomal polysomy. While generally benign, we present 2 grade II and the first cytogenetically confirmed grade III angiomatous meningioma, demonstrating their potentially aggressive behavior. Thus, multiple polysomies define angiomatous meningioma and aCGH can distinguish this variant from nonangiomatous meningiomas and other histological mimics in diagnostically challenging cases. Furthermore, the prominent vasculature is not neoplastic and likely induced by angiogenic factors. Together, these findings suggest a distinct tumorigenic pathway in angiomatous meningiomas.

Chronic Hydrocephalus Following Mumps Encephalitis: Neuropathological Correlates and Review

Hydrocephalus is a rare and devastating complication of mumps encephalitis. The histopathological correlates of mumps infection in central nervous system tissues are not well-characterized. We present the case of a 54-year-old patient who suffered long-term neuropsychiatric sequelae and hydrocephalus as a consequence of a childhood mumps infection. Brain autopsy revealed significant dilation of the lateral and third ventricles. Aqueductal stenosis was not observed on premortem imaging or on gross examination. Histology revealed loss of ependymal epithelium throughout the aqueduct and ventricular system. Macrophage conglomerates were identified within the cerebral aqueduct at the level of the pons in addition to subjacent periaqueductal gliosis and scattered Rosenthal fibers. Together, these findings support primary ependymal injury as a pathophysiological mechanism in the development of chronic hydrocephalus following mumps infection. Finally, we review the existing literature and discuss potential mechanisms of disease.

Intracranial Dural Parafalcine Chondroma: Case Report and Systematic Review of the Literature

Intracranial chondromas are rare, benign neoplasms representing only 0.2%-0.3% of neoplastic intracranial lesions. They commonly originate from the skull base but can infrequently arise from the falx, convexity dura, or ventricular ependyma. Diagnosis requires histopathologic confirmation, as patients present with nonspecific symptoms related to mass effect, and imaging characteristics often resemble meningiomas, oligodendrogliomas, and vascular malformations. We describe the case of a patient harboring a parafalcine dural chondroma that was discovered incidentally and was managed surgically at our institution. We also provide a systematic review of the literature to elucidate incidence, origin, imaging findings, surgical management approaches, and prognosis of this rare tumor.

Whole exome sequencing identifies a homozygous POLG2 missense variant in an infant with fulminant hepatic failure and mitochondrial DNA depletion

Mitochondrial DNA (mtDNA) depletion syndrome manifests as diverse early-onset diseases that affect skeletal muscle, brain and liver function. Mutations in several nuclear DNA-encoded genes cause mtDNA depletion. We report on a patient, a 3-month-old boy who presented with hepatic failure, and was found to have severe mtDNA depletion in liver and muscle. Whole-exome sequencing identified a homozygous missense variant (c.544C > T, p.R182W) in the accessory subunit of mitochondrial DNA polymerase gamma (POLG2), which is required for mitochondrial DNA replication. This variant is predicted to disrupt a critical region needed for homodimerization of the POLG2 protein and cause loss of processive DNA synthesis. Both parents were phenotypically normal and heterozygous for this variant. Heterozygous mutations in POLG2 were previously associated with progressive external ophthalmoplegia and mtDNA deletions. This is the first report of a patient with a homozygous mutation in POLG2 and with a clinical presentation of severe hepatic failure and mitochondrial depletion.

Atypical pleomorphic neoplasms of the pineal gland: Case report and review of the literature

Background:

Pineal region tumors are rare and diverse. Among them exist reports of pleomorphic xanthroastrocytoma (PXA) and pleomorphic granular cell astrocytoma (PGCA) of the pineal gland. These related tumors are remarkably similar sharing pleomorphic histologic features with only minor immunohistochemical and ultrastructural differences.

Case Description:

We present a case of a 42-year old right-handed woman presented with a longstanding history of migraine headaches which had worsened over the two months leading up to her hospitalization. MRI revealed a 1.7 × 1.3 × 1.6 cm intensely enhancing lesion originating in the pineal gland. The tumor closely resembled PGCA but did not strictly fit the diagnostic requirements of either PGCA or PXA.

Conclusion:

The present case highlights the exotic nature of pineal region tumors with pleomorphic cell histology. Given the diverse range of tumors encountered in the pineal region, pathological confirmation is mandatory. Favorable clinical outcomes demonstrate that surgical resection alone can yield excellent long-term results for tumors falling within the spectrum of pleomorphic lesions of the pineal gland.

Identification of a small molecule that induces ATG5-and-cathepsin-l-dependent cell death and modulates polyglutamine toxicity

Non-apoptotic cell death mechanisms are largely uncharacterized despite their importance in physiology and disease [1]. Here we sought to systematically identify non-apoptotic cell death pathways in mammalian cells. We screened 69,612 compounds for those that induce non-canonical cell death by counter screening in the presence of inhibitors of apoptosis and necrosis. We further selected compounds that require active protein synthesis for inducing cell death. Using this tiered approach, we identified NID-1 (Novel Inducer of Death-1), a small molecule that induces an active, energy-dependent cell death in diverse mammalian cell lines. NID-1-induced death required components of the autophagic machinery, including ATG5, and the lysosomal hydrolase cathepsin L, but was distinct from classical macroautophagy. Since macroautophagy can prevent cell death in several contexts, we tested and found that NID-1 suppressed cell death in a cell-based model of Huntington's disease, suggesting that NID-1 activates a specific pathway. Thus the discovery of NID-1 identifies a previously unexplored cell death pathway, and modulating this pathway may have therapeutic applications. Furthermore, these findings provide a proof-of-principle for using chemical screening to identify novel cell death paradigms.

Drug screening for Huntington's disease and other neurodegenerative disorders

Devising therapies for neurodegenerative diseases remains a major challenge due to the complex etiology, prolonged disease course and the paucity of validated targets. These factors make it difficult to model neurodegenerative diseases in a manner amenable to large-scale screening. However recent developments in automation, combinatorial chemistry and high-throughput phenotypic assays have presented new opportunities for discovering small molecule therapeutics for neurodegenerative diseases. This review focuses on novel in vitro and phenotypic screens for Huntington's disease and a few other neurodegenerative diseases. The lessons learned from these screens and the potential of the small molecules identified as therapeutic leads are discussed.

Mutant huntingtin alters cell fate in response to microtubule depolymerization via the GEF-H1-RhoA-ERK pathway

Cellular responses to drug treatment show tremendous variations. Elucidating mechanisms underlying these variations is critical for predicting therapeutic responses and developing personalized therapeutics. Using a small molecule screening approach, we discovered how a disease causing allele leads to opposing cell fates upon pharmacological perturbation. Diverse microtubule-depolymerizing agents protected mutant huntingtin-expressing cells from cell death, while being toxic to cells lacking mutant huntingtin or those expressing wild-type huntingtin. Additional neuronal cell lines and primary neurons from Huntington disease mice also showed altered survival upon microtubule depolymerization. Transcription profiling revealed that microtubule depolymerization induced the autocrine growth factor connective tissue growth factor and activated ERK survival signaling. The genotype-selective rescue was dependent upon increased RhoA protein levels in mutant huntingtin-expressing cells, because inhibition of RhoA, its downstream effector, Rho-associated kinase (ROCK), or a microtubule-associated RhoA activator, guanine nucleotide exchange factor-H1 (GEF-H1), all attenuated the rescue. Conversely, RhoA overexpression in cells lacking mutant huntingtin conferred resistance to microtubule-depolymerizer toxicity. This study elucidates a novel pathway linking microtubule stability to cell survival and provides insight into how genetic context can dramatically alter cellular responses to pharmacological interventions.

High throughput screening for neurodegeneration and complex disease phenotypes

High throughput screening (HTS) for complex diseases is challenging. This stems from the fact that complex phenotypes are difficult to adapt to rapid, high throughput assays. We describe the recent development of high throughput and high-content screens (HCS) for neurodegenerative diseases, with a focus on inherited neurodegenerative disorders, such as Huntington's disease. We describe, among others, HTS assays based on protein aggregation, neuronal death, caspase activation and mutant protein clearance. Furthermore, we describe high-content screens that are being used to prioritize hits identified in such HTS assays. These assays and screening approaches should accelerate drug discovery for neurodegenerative disorders and guide the development of screening approaches for other complex disease phenotypes.

Functional ablation of pRb activates Cdk2 and causes antiestrogen resistance in human breast cancer cells

Estrogens are required for the proliferation of hormone dependent breast cancer cells, making estrogen receptor (ER) positive tumors amenable to endocrine therapies such as antiestrogens. However, resistance to these agents remains a significant cause of treatment failure. We previously demonstrated that inactivation of the retinoblastoma protein (pRb) family tumor suppressors causes antiestrogen resistance in MCF-7 cells, a widely studied model of estrogen responsive human breast cancers. In this study, we investigate the mechanism by which pRb inactivation leads to antiestrogen resistance. Cdk4 and cdk2 are two key cell cycle regulators that can phosphorylate and inactivate pRb, therefore we tested whether these kinases are required in cells lacking pRb function. pRb family members were inactivated in MCF-7 cells by expressing polyomavirus large tumor antigen (PyLT), and cdk activity was inhibited using the cdk inhibitors p16^INK4A and p21^Waf1/Cip1. Cdk4 activity was no longer required in cells lacking functional pRb, while cdk2 activity was required for proliferation in both the presence and absence of pRb function. Using inducible PyLT cell lines, we further demonstrated that pRb inactivation leads to increased cyclin A expression, cdk2 activation and proliferation in antiestrogen arrested cells. These results demonstrate that antiestrogens do not inhibit cdk2 activity or proliferation of MCF-7 cells in the absence of pRb family function, and suggest that antiestrogen resistant breast cancer cells resulting from pRb pathway inactivation would be susceptible to therapies that target cdk2.

Inhibitors of metabolism rescue cell death in Huntington's disease models

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder. HD is caused by polyglutamine expansions in the huntingtin (htt) protein that result in neuronal loss and contribute to HD pathology. The mechanisms of neuronal loss in HD are elusive, and there is no therapy to alleviate HD. To find small molecules that slow neuronal loss in HD, we screened 1,040 biologically active molecules to identify suppressors of cell death in a neuronal cell culture model of HD. We found that inhibitors of mitochondrial function or glycolysis rescued cell death in this cell culture and in in vivo HD models. These inhibitors prevented cell death by activating prosurvival ERK and AKT signaling but without altering cellular ATP levels. ERK and AKT inhibition through the use of specific chemical inhibitors abrogated the rescue, whereas their activation through the use of growth factors rescued cell death, suggesting that this activation could explain the protective effect of metabolic inhibitors. Both ERK and AKT signaling are disrupted in HD, and activating these pathways is protective in several HD models. Our results reveal a mechanism for activating prosurvival signaling that could be exploited for treating HD and possibly other neurodegenerative disorders.

Identification of potential therapeutic drugs for huntington's disease using Caenorhabditis elegans

Background

The prolonged time course of Huntington's disease (HD) neurodegeneration increases both the time and cost of testing potential therapeutic compounds in mammalian models. An alternative is to initially assess the efficacy of compounds in invertebrate models, reducing time of testing from months to days.

Methodology/Principal Findings

We screened candidate therapeutic compounds that were identified previously in cell culture/animal studies in a C. elegans HD model and found that two FDA approved drugs, lithium chloride and mithramycin, independently and in combination suppressed HD neurotoxicity. Aging is a critical contributor to late onset neurodegenerative diseases. Using a genetic strategy and a novel assay, we demonstrate that lithium chloride and mithramycin remain neuroprotective independent of activity of the forkhead transcription factor DAF-16, which mediates the effects of the insulin-like signaling pathway on aging.

Conclusions/Significance

These results suggest that pathways involved in polyglutamine-induced degeneration are distinct from specific aging pathways. The assays presented here will be useful for rapid and inexpensive testing of other potential HD drugs and elucidating pathways of drug action. Additionally, the neuroprotection conferred by lithium chloride and mithramycin suggests that these drugs may be useful for polyglutamine disease therapy.

Selective inhibitors of death in mutant huntingtin cells

Huntington disease (HD) is an inherited neurodegenerative disorder with unclear pathophysiology. We developed a high-throughput assay in a neuronal cell culture model of HD, screened 43,685 compounds and identified 29 novel selective inhibitors of cell death in mutant huntingtin-expressing cells. Four compounds were active in diverse HD models, which suggests a role for cell death in HD; these compounds are mechanistic probes and potential drug leads for HD.

Antiestrogen ICI 182,780 decreases proliferation of insulin-like growth factor I (IGF-I)-treated MCF-7 cells without inhibiting IGF-I signaling

Previous studies have suggested that antiestrogens inhibit MCF-7 cell proliferation by alteringthe expression or activity of components of the insulin-like growth factor I (IGF-I) signaling pathway, including IGF-I receptor, insulin receptor substrate 1, and phosphatidylinositol 3-kinase. In this report, we examine the effects of the pure antiestrogen ICI 182,780 (ICI) on various targets of IGF-I signaling in MCF-7 cells. ICI treatment led to decreases in the absolute levels of cyclin D1 and cyclin A expression, retinoblastoma protein phosphorylation, and DNA synthesis in IGF-I-treated cells. However, IGF-I retained the ability to induce these events in the presence of ICI, suggesting that ICI treatment did not completely block IGF-I signaling. Consistent with this suggestion, IGF-I-induced phosphorylation of extracellular signal-regulated kinase, AKT, and insulin receptor substrate 1 was unaffected by ICI treatment. Finally, transient expression of either constitutively active phosphatidylinositol 3-kinase or AKT was unable to induce proliferation in ICI-treated MCF-7 cells. Together, these results indicate that ICI can inhibit proliferation without blocking IGF-I signaling and suggest a model in which both estrogen receptor and IGF-I signaling regulate cell cycle components and are required for MCF-7 cell proliferation.

A draft sequence of the rice genome (Oryza sativa L. ssp. japonica)

The genome of the japonica subspecies of rice, an important cereal and model monocot, was sequenced and assembled by whole-genome shotgun sequencing. The assembled sequence covers 93% of the 420-megabase genome. Gene predictions on the assembled sequence suggest that the genome contains 32,000 to 50,000 genes. Homologs of 98% of the known maize, wheat, and barley proteins are found in rice. Synteny and gene homology between rice and the other cereal genomes are extensive, whereas synteny with Arabidopsis is limited. Assignment of candidate rice orthologs to Arabidopsis genes is possible in many cases. The rice genome sequence provides a foundation for the improvement of cereals, our most important crops.

A draft sequence of the rice genome (Oryza sativa L. ssp. japonica)

The genome of the japonica subspecies of rice, an important cereal and model monocot, was sequenced and assembled by whole-genome shotgun sequencing. The assembled sequence covers 93% of the 420-megabase genome. Gene predictions on the assembled sequence suggest that the genome contains 32,000 to 50,000 genes. Homologs of 98% of the known maize, wheat, and barley proteins are found in rice. Synteny and gene homology between rice and the other cereal genomes are extensive, whereas synteny with Arabidopsis is limited. Assignment of candidate rice orthologs to Arabidopsis genes is possible in many cases. The rice genome sequence provides a foundation for the improvement of cereals, our most important crops.

Reversal of an antiestrogen-mediated cell cycle arrest of MCF-7 cells by viral tumor antigens requires the retinoblastoma protein-binding domain

Proliferation of MCF-7 cells is estrogen dependent and antiestrogen sensitive. In the absence of estrogens or presence of antiestrogens MCF-7 cells arrest in the G1 phase of the cell cycle, and this arrest is associated with an accumulation of the active, hypophosphorylated form of the retinoblastoma protein (pRb). Because active pRb negatively regulates passage from G1 to S phase, this suggests that pRb is a crucial target of estrogen action, and that its inactivation might lead to antiestrogen resistance. We tested this hypothesis by expressing viral tumor antigens (T antigens), which bind and inactivate pRb, in MCF-7 cells, and determining the effects on cell proliferation in the presence of antiestrogens. The results of these experiments demonstrate that T antigen expression confers antiestrogen resistance to MCF-7 cells. Using a panel of mutant T antigens, we further demonstrate that the pRb-binding, but not the p53 binding domain is required to confer antiestrogen resistance. Thus, pRb is an important target of estrogen action, and its inactivation can contribute to the development of antiestrogen resistance.

Strain in the medial collateral ligament of the human knee under single and combined loads

Strain within the medial collateral ligament (MCL) was measured in 13 human knee specimens to determine both the single and combined external loads most likely to cause injury. Using a load application system which allowed six degrees of freedom with flexion angle being fixed, both single loads of anterior/posterior force, medial/lateral force, varus/valgus torque, and internal/external axial torque and all pairs of these loads were applied at flexion angles of 0 degrees and 30 degrees. Liquid mercury strain gages were used to measure strain at four sites in the MCL. Two of the sites were the anterior fibers superior and inferior to the joint line and the other two were posterior of the two anterior sites. A factorial analysis revealed a significant interaction between the site experiencing the greatest strain and flexion angle. The posterior superior site experienced significantly greater strain at 0 degree flexion whereas strains was significantly greater at the anterior superior site at 30 degree flexion. Of the single moments, external axial was more damaging than valgus in that the strain developed at equivalent load was significantly greater. None of the moment-moment combinations was identified as being significantly more damaging. A similar result held for the force-moment combinations.

Goniometric measurement of hip motion in cycling while standing

The purpose of this study was to develop an instrument for quantifying the motion of the hip relative to the bicycle while cycling in the standing position. Because of the need to measure hip motion on the road as well as in the laboratory, a goniometer which locates the hip using spherical coordinates was designed. The goniometer is presented first, followed by the development of the equations that enable the distance from the joint center to the pedal spindle to be determined. The orientation of this line segment is specified by calculating two angles referenced to the frame. Also outlined are the procedures used to both calibrate the goniometer and perform an accuracy check. The results of this check indicate that the attachment point of the goniometer to the rider can be located to within 2.5 mm of the true position. The goniometer was used to record the hip movement patterns of six subjects who cycled in the standing position on a treadmill. Representative results from one test subject who cycled at 6% grade and 25 km h-1 are presented. Results indicate that the bicycle is leaned from side to side with the frequency of leaning equal to the frequency of pedalling. Extreme lean angles are +/- 6 degrees. The distance from the hip to the pedal varies approximately sinusoidally with frequency equal to pedalling rate and amplitude somewhat less than crank arm length. The absolute elevation of the hip, however, exhibits two cycles for each crank cycle. Asymmetry in the plot of elevation over a single crank cycle indicates that the pelvis rocks from side to side and that the elevation of the pelvis midpoint changes. Extreme values of the pelvis rocking angle are +/- 12 degrees. Highest pelvis midpoint elevations, however, do not occur at the same crank angles as those angles at which the pelvis rocking is extreme. It appears that the vertical motion of the hips affects pedalling mechanics when cycling in the standing position.