Access to ear and hearing care services in Cambodia: a qualitative enquiry into experiences of key informants

OBJECTIVE

In Cambodia, little is known about the state of ear and hearing care, or the roles providers or key stakeholders play in delivering services.

METHOD

This was an exploratory study using semi-structured qualitative interviews and a questionnaire addressed to key stakeholders to explore their perceptions and experiences in providing services to people suffering from ear disease or hearing loss in Cambodia.

RESULTS

Several challenges were described including a lack of hearing services to meet the demand, especially outside Phnom Penh in primary care and aural rehabilitation. Supply-side challenges include a shortage of trained professionals, facilities and resources, poor co-ordination between providers, unclear referral pathways, and long wait times.

CONCLUSION

Now is an opportune time to build on the positive trend in providing integrated care for non-communicable diseases in Cambodia, through the integration of effective ear and hearing care into primary care and strengthening the package of activities delivered at government facilities.

Characterization of Selective M5 Acetylcholine Muscarinic Receptor Modulators on Dopamine Signaling in the Striatum

The type-5 muscarinic acetylcholine receptor (mAChR, M5) is almost exclusively expressed in dopamine (DA) neurons of the ventral tegmental area and substantia nigra pars compacta; therefore, they are ideally located to modulate DA signaling and underlying behaviors. However, the role of M5 in shaping DA release is still poorly characterized. In this study, we first quantitatively mapped the expression of M5 in different neurons of the mouse midbrain, then used voltammetry in mouse striatum to evaluate the effect of M5-selective modulators on DA release. The M5 negative allosteric modulator ML375 significantly decreased electrically evoked DA release and blocked the effect of Oxotremorine-M (Oxo-M; nonselective mAChR agonist) on DA release in the presence of an acetylcholine nicotinic receptor blocker. Conversely, the M5 positive allosteric modulator VU 0365114 significantly increased electrically evoked DA release and the Oxo-M effect on DA release. We then assessed M5's impact on mesolimbic circuit function in vivo. Although psychostimulant-induced locomotor activity models in knockout mice have previously been used to characterize the role of M5 in DA transmission, the results of these studies conflict, leading us to select a different in vivo model, namely a cocaine self-administration paradigm. In contrast to a previous study that also used this model, in the current study, administration of ML375 did not decrease cocaine self-administration in rats (using fixed and progressive ratio). These conflicting results illustrate the complexity of M5 modulation and the need to further characterize its involvement in the regulation of dopamine signaling, central to multiple neuropsychiatric diseases. SIGNIFICANCE STATEMENT: This work describes the type-5 muscarinic receptor (M5) pattern of expression within the midbrain as well as its physiological modulation by selective compounds at the axon terminal level in the striatum, where M5 directly shapes dopamine transmission. It offers the first direct readout of mesolimbic dopamine release modulation by M5, highlighting its role in regulating neurocircuits implicated in the pathophysiology of neuropsychiatric disorders such as substance use disorders, major depressive disorder, and schizophrenia.

Validation of a diet-induced Macaca fascicularis model of non-alcoholic steatohepatitis with dietary and pioglitazone interventions

AIM

To develop an obese, insulin-resistant cynomolgus monkey model of non-alcoholic steatohepatitis (NASH) with fibrosis with a high fat/high cholesterol (HFHC) diet (with or without high fructose) and test its responsiveness to caloric restriction or pioglitazone.

METHODS

First, two groups of monkeys (n = 24/group) with histologically proven NASH and fibrosis were fed the HFHC diet for 17 weeks. The treatment group was subjected to a 40% caloric restriction (CR) and had their diet switched from the HFHC diet to a chow diet (DSCR). Paired liver biopsies were taken before and 17 weeks after DSCR. Subsets of monkeys (nine/group) had whole liver fat content assessed by MRI. Next, two groups of monkeys with histologically proven NASH and fibrosis were treated with vehicle (n = 9) or pioglitazone (n = 20) over 24 weeks.

RESULTS

The HFHC and DSCR groups lost 0.9% and 11.4% of body weight, respectively. After 17 weeks, non-alcoholic fatty liver disease activity score (NAS) improvement was observed in 66.7% of the DSCR group versus 12.5% of the HFHC group (P < .001). Hepatic fat was reduced to 5.2% in the DSCR group versus 23.0% in the HFHC group (P = .0001). After 24 weeks, NAS improvement was seen in 30% of the pioglitazone group versus 0% of the vehicle group (P = .08).

CONCLUSIONS

Both weight loss induced by DSCR and treatment with pioglitazone improve the histological features of NASH in a diet-induced cynomolgus monkey model. This model provides a translational preclinical model for testing novel NASH therapies.

Comprehensive BCMA Expression Profiling in Adult Normal Human Brain Suggests a Low Risk of On-target Neurotoxicity in BCMA-targeting Multiple Myeloma Therapy

B-cell maturation antigen (BCMA) is a target for the treatment of multiple myeloma with cytolytic therapies, such as chimeric antigen receptor T-cells or T-cell redirecting antibodies. To better understand the potential for "on-target/off-tumor" toxicity caused by BCMA-targeting cytolytic therapies in the brain, we investigated normal brain BCMA expression. An immunohistochemistry (IHC) assay using the E6D7B commercial monoclonal antibody was applied to 107 formalin-fixed, paraffin-embedded brain samples (cerebrum, basal ganglia, cerebellum, brainstem; 63 unique donors). Although immunoreactivity was observed in a small number of neurons in brain regions including the striatum, thalamus, midbrain, and medulla, this immunoreactivity was considered nonspecific and not reflective of BCMA expression because it was distinct from the membranous and Golgi-like pattern seen in positive control samples, was not replicated when a different IHC antibody (D6 clone) was used, and was not corroborated by in situ hybridization data. Analysis of RNA-sequencing data from 478 donors in the GTEx and Allen BrainSpan databases demonstrated low levels of BCMA RNA expression in the striatum of young donors with levels becoming negligible beyond 30 years of age. We concluded that BCMA protein is not present in normal adult human brain, and therefore on-target toxicity in the brain is unlikely.

Human ileal organoid model recapitulates clinical incidence of diarrhea associated with small molecule drugs

Drug-induced gastrointestinal toxicity (GIT) is a common treatment-emergent adverse event that can negatively impact dosing, thereby limiting efficacy and treatment options for patients. An in vitro assay of GIT is needed to address patient variability, mimic the microphysiology of the gut, and accurately predict drug-induced GIT. Primary human ileal organoids (termed 'enteroids') have proven useful for stimulating intestinal stem cell proliferation and differentiation to multiple cell types present in the gut epithelium. Enteroids have enabled characterization of gut biology and the signaling involved in the pathogenesis of disease. Here, enteroids were differentiated from four healthy human donors and assessed for culture duration-dependent differentiation status by immunostaining for gut epithelial markers lysozyme, chromogranin A, mucin, and sucrase isomaltase. Differentiated enteroids were evaluated with a reference set of 31 drugs exhibiting varying degrees of clinical incidence of diarrhea, a common manifestation of GIT that can be caused by drug-induced thinning of the gut epithelium. An assay examining enteroid viability in response to drug treatment demonstrated 90% accuracy for recapitulating the incidence of drug-induced diarrhea. The human enteroid viability assay developed here presents a promising in vitro model for evaluating drug-induced diarrhea.

Abstract A43: Spatial organization of pancreatic ductal adenocarcinoma (PDAC)–associated immune cells from the Adjuvant Pancreatic Adenocarcinoma Clinical Trial (APACT) study

Introduction: It is strikingly difficult to develop successful treatments for PDAC; even with curative resection, most patients die from early occult metastases. Prior studies identified the presence of tumor-infiltrating lymphocytes (TILs) in primary PDAC tumors as having prognostic significance in the PDAC adjuvant setting, sharpening the questions of what fraction of patients have immune-infiltrated tumors and what therapeutic strategies should be pursued in these patients vs. the non-infiltrated group. The phase 3 APACT trial evaluated the use of adjuvant nab-paclitaxel plus gemcitabine vs. gemcitabine in 866 patients with PDAC who had undergone primary tumor resection, with the primary endpoint of disease-free survival evaluated by independent review. We extended studies of the tumor microenvironment of PDAC to a large set of resected APACT primary tumors in an effort to further refine features of tumor or immune infiltrate that influence disease progression and to determine if chemotherapy regimen–specific predictive signatures are identifiable. Tissue analyses for a large subset of APACT samples included RNA-seq, DNA-seq, multiplexed immunohistochemistry (IHC), and proteomics.

Methods: We imaged and quantified markers for tumor cells, 7 different immune cells, and 2 immune checkpoint markers using bright-field chromogenic multiplexed IHC from pretreatment samples for more than 500 APACT primary tumor samples. We computationally defined the tumor, tumor margin, and distal stromal (&gt; 150 μm from tumor boundary) regions, and quantified densities and distributions of immune cells in these regions. As part of an initial analysis of more than 400 samples, we applied both unsupervised clustering and supervised classification to these IHC measurements to identify patient subgroups with similar spatial arrangements of immune cells relative to tumor regions.

Results: The preliminary analysis of normalized cell densities across all 3 tissue regions revealed 3 patient subgroups: one in which immune cells are mixed within the tumor regions; a second where immune cells approach the tumor boundary but are depleted within the tumor; and a third in which immune cells are depleted in both tumor and its margin, remaining at high densities only in the distal stromal regions. Within these latter subgroups, CD20+, CD4+, and CD8+ cells were more prevalently depleted from tumor and/or margin, whereas CD163+ and CD163+CMAF+ cells showed less of this arrangement. Nearly 85% of patients fell in the second or third patient group.

Conclusions: We are pursuing analyses of these data in conjunction with upcoming molecular and genetic profiling data to further elucidate the association of the immune cell populations and these subgroups with clinical outcomes. These data will provide an unprecedented opportunity for exploratory analysis and discovery of immune, molecular, and genetic biomarkers for PDAC patient stratification.

Citation Format: David J. Reiss, Thomas Lila, Suzana Couto, Sitharthan Kamalakaran, Yan Ren, Doug Bowman, Amber Ortiz, Maria Wang, Clifton Drew, Kao-Tai Tsai, Mathieu Marella, Brian Fox, Garth McGrath, Matthew Trotter, Fadi Towfic, Ian Cushman, Alexander Ratushny, Brian Lu, Daniel Pierce, Jim Cassidy. Spatial organization of pancreatic ductal adenocarcinoma (PDAC)–associated immune cells from the Adjuvant Pancreatic Adenocarcinoma Clinical Trial (APACT) study [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A43.

The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

Hyaluronan accumulation in the tumor microenvironment is associated with poor prognosis in several solid human cancers. To understand the role of stromal hyaluronan in tumor progression, we engineered 3T3HAS3, a hyaluronan-producing fibroblast cell line, by lentiviral transduction of Balb/c 3T3 cells with the human hyaluronan synthase 3(HAS3) gene. 3T3HAS3 cells significantly enhanced tumor growth when co-grafted with MDA-MB-468 cells in nude mice. Immunohistochemical analysis of the xenograft tumors showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of MDA-MB-468 + 3T3HAS3 co-grafts was greatly reduced upon hyaluronan degradation by lentiviral transduction of a human hyaluronidase gene in 3T3HAS3 cells, or by systemic administration of pegvorhyaluronidase alfa (PEGPH20). In contrast, the growth of the co-graft tumors was not inhibited when CD44 expression was reduced or ablated by small hairpin RNA-mediated CD44 knockdown in MDA-MB-468 cells, CD44 CRISPR knockout in 3T3HAS3 cells, or by grafting these cells in CD44 knockout nude mice. Collectively, these data demonstrate that tumor growth of an engineered xenograft breast cancer model with hyaluronan-accumulating stroma can be dependent on hyaluronan and independent of CD44.

KIAA1199 expression and hyaluronan degradation colocalize in multiple sclerosis lesions

Modification of hyaluronan (HA) accumulation has been shown to play a key role in regulating inflammatory processes linked to the progression of multiple sclerosis (MS). The aim of this study was to characterize the enzymatic activity involved in HA degradation observed within focal demyelinating lesions in the experimental autoimmune encephalomyelitis (EAE) animal model. EAE was induced in 3-month-old female C57BL/6J mice by immunization with myelin oligodendrocyte glycoprotein 33–35 (MOG33–35) peptide. The mice were monitored for 21 days. Formalin-fixed paraffin-embedded tissue from control and EAE mice were labeled with an immunoadhesin against HA, antibodies against KIAA1199 and glial fibrillary acidic protein, a marker for astrocytes. In situ hybridization was conducted using a KIAA1199 nucleic acid probe. In histologic sections of spinal cord from EAE mice, abnormal HA accumulation was observed in the close vicinity of the affected areas, whereas HA was totally degraded within the focal loci of damaged tissue. KIAA1199 immunoreactivity was exclusively associated with focal loci in damaged white columns of the spinal cord. KIAA1199 was mainly expressed by activated astrocytes that invaded damaged tissue. Similar findings were observed in tissue from an MS patient. Here, we show that KIAA1199, a protein that plays a role in a HA degradation pathway independent of the canonical hyaluronidases such as PH20, is specifically expressed in tissue lesions in which HA is degraded. KIAA1199 expression by activated astrocytes may explain the focal HA degradation observed during progression of MS and could represent a possible new therapeutic target.

UBE2G1 governs the destruction of cereblon neomorphic substrates

The cereblon modulating agents (CMs) including lenalidomide, pomalidomide and CC-220 repurpose the Cul4-RBX1-DDB1-CRBN (CRL4^CRBN) E3 ubiquitin ligase complex to induce the degradation of specific neomorphic substrates via polyubiquitination in conjunction with E2 ubiquitin-conjugating enzymes, which have until now remained elusive. Here we show that the ubiquitin-conjugating enzymes UBE2G1 and UBE2D3 cooperatively promote the K48-linked polyubiquitination of CRL4^CRBN neomorphic substrates via a sequential ubiquitination mechanism. Blockade of UBE2G1 diminishes the ubiquitination and degradation of neomorphic substrates, and consequent antitumor activities elicited by all tested CMs. For example, UBE2G1 inactivation significantly attenuated the degradation of myeloma survival factors IKZF1 and IKZF3 induced by lenalidomide and pomalidomide, hence conferring drug resistance. UBE2G1-deficient myeloma cells, however, remained sensitive to a more potent IKZF1/3 degrader CC-220. Collectively, it will be of fundamental interest to explore if loss of UBE2G1 activity is linked to clinical resistance to drugs that hijack the CRL4^CRBN to eliminate disease-driving proteins.

Abstract 2101: The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

The abnormal accumulation of hyaluronan in the solid tumor microenvironment is associated with poor prognosis in several human cancers. Hyaluronan often accumulates in the tumor stroma. To understand the role of hyaluronan-accumulating stroma in tumor progression, we engineered a hyaluronan-producing fibroblast cell line 3T3HAS3 by lentiviral transduction of the human hyaluronan synthase 3 gene into Balb/c 3T3 cells. The 3T3HAS3 cells produced significant amounts of hyaluronan in vitro, which bind to the cell surface of the human breast cancer cell line MDA-MB-468. When co-grafted with MDA-MB-468 cells in nude mice, 3T3HAS3 significantly enhanced tumor growth. Immunohistochemical analysis of tumor xenografts showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of this co-graft model required hyaluronan production from 3T3HAS3 cells, as demonstrated by the delayed tumor growth upon hyaluronan removal by expression of the human PH20 gene in 3T3HAS3 cells, or by systemic administration of PEGylated recombinant human PH20 (PEGPH20). In contrast, neither the expression of CD44, a well-characterized hyaluronan receptor, in tumor and stromal fibroblasts, nor the binding of hyaluronan to CD44 in MDA-MB-468 tumor cells was essential for tumor growth. Small scale screening of signaling changes in xenograft tumors suggested that the AMPK/mTOR pathway may respond to hyaluronan removal by PEGPH20. Collectively, these data demonstrate that the growth of an engineered breast cancer xenograft model with hyaluronan-accumulating stroma is dependent on hyaluronan, and that hyaluronan-CD44 interaction may not be the main mechanism through which hyaluronan promotes tumor progression in certain tumors.

Citation Format: Chunmei Zhao, Benjamin J. Thompson, Kelly Chen, Mathieu Marella, Susan Zimmerman, Trevor Kimbler, Barbara Blouw, Sheryl Garrovillo, Lei Huang, Adrian Radi, Zhongdong Huang, H. Michael Shepard, Sanna Rosengren, Christopher D. Thanos, Daniel C. Maneval. The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2101.

PH20 is not expressed in murine CNS and oligodendrocyte precursor cells

Objective

Expression of Spam1/PH20 and its modulation of high/low molecular weight hyaluronan substrate have been proposed to play an important role in murine oligodendrocyte precursor cell (OPC) maturation in vitro and in normal and demyelinated central nervous system (CNS). We reexamined this using highly purified PH20.

Methods

Steady‐state expression of mRNA in OPCs was evaluated by quantitative polymerase chain reaction; the role of PH20 in bovine testicular hyaluronidase (BTH) inhibition of OPC differentiation was explored by comparing BTH to a purified recombinant human PH20 (rHuPH20). Contaminants in commercial BTH were identified and their impact on OPC differentiation characterized. Spam1/PH20 expression in normal and demyelinated mouse CNS tissue was investigated using deep RNA sequencing and immunohistological methods with two antibodies directed against recombinant murine PH20.

Results

BTH, but not rHuPH20, inhibited OPC differentiation in vitro. Basic fibroblast growth factor (bFGF) was identified as a significant contaminant in BTH, and bFGF immunodepletion reversed the inhibitory effects of BTH on OPC differentiation. Spam1 mRNA was undetected in OPCs in vitro and in vivo; PH20 immunolabeling was undetected in normal and demyelinated CNS.

Interpretation

We were unable to detect Spam1/PH20 expression in OPCs or in normal or demyelinated CNS using the most sensitive methods currently available. Further, “BTH” effects on OPC differentiation are not due to PH20, but may be attributable to contaminating bFGF. Our data suggest that caution be exercised when using some commercially available hyaluronidases, and reports of Spam1/PH20 morphogenic activity in the CNS may be due to contaminants in reagents.

Abstract A46: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma

Hyaluronan (also known as hyaluronic acid or HA) is a megadalton sized glycosaminoglycan present in the extracellular matrix. The abnormal accumulation of HA in the solid tumor microenvironment (TME) of several human cancers, including pancreatic, breast, colon and prostate, has been well studied and is associated with poor prognosis. In certain breast cancer specimens with a HA-high status, HA is found to be significantly associated with the stromal compartment rather than with tumor cells. To understand the interaction between tumor cells and a HA containing stromal compartment, we engineered a HA-high stromal cell line by lentiviral transduction of the human HAS3 gene into Balb/c 3T3 fibroblast cells. The 3T3/HAS3 cells produced significant amounts of HA in vitro, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Immunohistochemical analysis of tumor xenograft samples showed that MDA-MB-468 cells were surrounded by HA-high stromal cells, closely resembling the tumor morphology observed in human breast cancer specimens. Tumor growth in this co-grafting model was highly dependent on the presence of 3T3/HAS3 cells, and required HA produced by 3T3/HAS3 cells. Ganciclovir blocked the growth of MDA-MB-468 co-inoculated with 3T3/HAS3/hsv-TK, as did HA removal either by the expression of the HA degrading enzyme PH20, directly in 3T3/HAS3 cells or by exogenous administration of PEGPH20, a pegylated version of PH20 engineered for extended half-life. Interestingly, the presence of 3T3/HAS3 cells was found to be most critical during early stages of tumor progression and was non-essential for tumor maintenance once tumors were fully established, as ganciclovir had little impact on tumor growth when tumor size was larger than 500 mm3 but prevented tumor growth when administered at inoculation and inhibited tumor growth when treatment started at a smaller tumor size (200 mm3, 90.4% TGI). We have developed a tumor xenograft model that mimics breast cancer with a HA-high status in the tumor stromal compartment. Further characterization of this model will provide insight into the mechanisms by which increased levels of HA and the associated changes in the TME promote disease progression in breast cancer.

Citation Format: Chunmei Zhao, Mathieu Marella, Lei Huang, Anne Kultti, Susan Zimmerman, Caroline EN Chou, Jesse Bahn, Adrian Radi, Zhongdong Huang, H Michael Shepard, Christopher D. Thanos. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A46.

Abstract 1472: Enzymatic depletion of adenosine by pegylated, engineered adenosine deaminase 2 (PEG-ADA2): A novel immunotherapeutic approach to treat solid tumors

Adenosine is an endogenous immunosuppressant that binds to adenosine receptor checkpoints and protects tissue from immune-mediated rejection. Abnormally high adenosine levels (up to 100-fold greater than other tissues) contribute to a highly immunosuppressive tumor microenvironment (TME). We hypothesized that adenosine deaminase 2 (ADA2), a human enzyme that catalyzes the deamination of adenosine, could be administered at therapeutic levels to deplete high levels of TME adenosine and stimulate anti-tumor immune activity. Recombinant wild-type ADA2 (wtADA2) was cleared extremely rapidly from circulation (t1/2 = 69 min, 7.5 mg/kg iv, n = 9 mice), rendering it unsuitable for therapeutic testing. Therefore, a series of variants was designed to attenuate the heparin binding properties of ADA2 to improve bio-distribution and conjugated with 20K PEG to improve pharmacokinetics (PK). The variant PEG-ADA2-K374D displayed 94% less binding to heparin compared to wtADA2, enzymatic activity comparable to wtADA2, and 33-fold improved PK (t1/2 = 2,256 min); and consistently induced at least 60% (p&lt;0.0001) tumor growth inhibition (TGI) of established subcutaneous syngeneic CT26 tumors (b.i.w., 0.3mg/kg, n = 8). Treatment with PEG-ADA2-K374D resulted in a 5-fold increase in tumor infiltrating CD3+ T-cells (p&lt;0.0001, 6 hours post dose), as assessed by histology. We hypothesized that CD73, which catalyzes the turnover of AMP to adenosine, could be used as a biomarker to identify tumors with elevated adenosine levels. Gene expression studies against a panel of syngeneic tumors revealed that lung KLN205 and pancreatic MH194/PSC4 tumors had high CD73 levels. PEG-ADA2-K374D inhibited the growth of established MH194/PSC4 and KLN205 tumors, with TGI reaching 47% (p&lt;0.0001) and 78% (p&lt;0.0001) after 2 weeks of treatment (b.i.w, 0.3 mg/kg, n = 8). A second series of variants was generated based on structure-based design to have significantly improved kcat/km for adenosine deaminase activity. ADA2-R222Q/S265N had the highest improvement, with a 15-fold greater kcat/km than wtADA2. After pegylation, the circulating half-life of PEG-ADA2-R222Q-S265N in mice was extended from 69 min to 2,790 min (&gt;40-fold increase). This variant induced a maximum TGI of 69% (p&lt;0.05) in the MH194/PSC4 model at 0.003 mg/kg, a 100-fold lower dose than PEG-ADA2-K374D (n = 8). A third variant, PEG-ADA2-E182T lacked detectable enzymatic activity and displayed no tumor growth inhibition, suggesting that ADA2 enzyme activity is required for efficacy. These data

suggest that engineered PEG-ADA2 variants induce significant tumor growth inhibition activity in several syngeneic solid tumor models, validating enzymatic depletion of high TME adenosine levels as novel immunotherapeutic approach to treat solid tumors.

Citation Format: Lin Wang, Jessica Cowell, Sanna Rosengren, Lei Huang, Xiaoming Li, Qiping Zhao, Jennifer Souratha, Mathieu Marella, Barbara Blouw, Keri Cannon, Chunmei Zhao, Kim Phan, Curtis Thompson, Michael Shepard, Christopher Thanos. Enzymatic depletion of adenosine by pegylated, engineered adenosine deaminase 2 (PEG-ADA2): A novel immunotherapeutic approach to treat solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1472.

Abstract 283: PEGylated recombinant hyaluronidase PH20 (PEGPH20) enhances pemetrexed antitumor efficacy in a human nonsquamous NSCLC xenograft model

Introduction: Hyaluronan (HA) is an extracellular matrix glycosaminoglycan that has been shown to accumulate at high levels in several cancers, including non-small cell lung cancer (NSCLC). The accumulation of HA in NSCLC is associated with a more aggressive phenotype and shortened overall survival. In a prevalence analysis using tissue microarrays of archival human specimens (N = 194) stained by affinity histochemistry, we demonstrated that 55% of adenocarcinomas, 74% of squamous cell carcinomas and 83% of large cell carcinomas accumulated HA. The engineered enzyme PEGylated recombinant human hyaluronidase PH20 (PEGPH20) removes HA from the tumor microenvironment. PEGPH20-based therapies are being evaluated in clinical studies of several solid tumors, including NSCLC (NCT02346370, NCT02563548). Herein, we evaluated the hypothesis that PEGPH20 combination therapy could enhance the efficacy of pemetrexed (PEM), a folate antimetabolite approved by FDA as a first-line treatment in combination with cisplatin, against locally advanced and metastatic NSCLC in patients with non-squamous histology.

Methods: We evaluated PEGPH20 plus PEM in a NSCLC xenograft model. First, the human NSCLC adenocarinoma cell line A549 was transduced with hyaluronan synthase-3 (HAS3) to generate the A549/HAS3 cell line. Next, A549/HAS3 cells were inoculated adjacent to the tibial periosteum of nude mice and tumor growth was monitored via ultrasonography. When tumors size reached ∼250 mm3, mice were staged into six groups: (1) vehicle; (2) PEGPH20, (3) PEM daily, (4) PEM weekly, (5) PEGPH20+PEM daily or (6) PEGPH20+PEM weekly. Vascular volume, hypoxia and tumor growth inhibition (TGI) were assessed using conventional methods. Affinity histochemical staining for HA was performed on formalin-fixed paraffin-embedded tissue sections after harvest.

Results: A549/HAS3 tumors grew faster than parental A549 tumors in vivo. PEGPH20 monotherapy significantly reduced tumoral HA, increased vascular volume and reduced hypoxia in tumors. Further, TGI with PEGPH20+PEM, weekly or daily, was 29.7 or 31.1%, respectively, whereas in either PEGPH20 alone or PEM alone, both were &lt;9%. Staining of A549/HAS3 tumors showed increased accumulation of HA as compared with the parental A549 xenografts.

Conclusion: These data suggest that addition of PEGPH20 to pemetrexed increases the efficacy of PEM and support further investigation of PEGPH20 plus PEM treatment in NSCLC tumors of non-squamous histology that accumulate HA.

Citation Format: Renee Clift, Jessica A. Cowell, Susan J. Zimmerman, Mathieu Marella, Ping Jiang, Arnold B. Gelb, Michael J. LaBarre, Daniel C. Maneval, Curtis B. Thompson, Xiaoming Li. PEGylated recombinant hyaluronidase PH20 (PEGPH20) enhances pemetrexed antitumor efficacy in a human nonsquamous NSCLC xenograft model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 283.

Assessment of hyaluronic acid in tumor microenvironment (TME) of intrahepatic cholangiocarcinoma (CCA)

248

Background: Improved understanding of TME in CCA may allow for development of novel therapeutics targeting stromal components. Hyaluronic acid (HA) is a polysaccharide that has been found in the TME of a number of solid tumors characterized by desmoplastic stroma, such as pancreatic cancer. Elevated HA levels were prognostic in these malignancies. HA prevalence and association with clinic-pathological features in CCA is unknown. Methods: A retrospective study was conducted using clinically annotated formalin-fixed paraffin embedded tissue from resected intrahepatic CCA samples. Specimens were analyzed for HA, scored using a positive pixel count algorithm (Aperio Imagescope) and positivity was calculated as % of total pixel count. Clinical variables were examined by chi-square or ANOVA F-test. Overall survival (OS) and progression-free survival (PFS) were estimated using Kaplan-Meier method and compared via log-rank test. Multivariate analysis was conducted using Cox proportional hazards regression models. Results: 142 patient samples were stained for HA. HA was identified in all samples (100%), with a range of HA positivity of 32.8 – 91.8%. Median HA value was 67.1% and 95% of patients had HA positivity ≥ 45%. Factors associated with higher than median HA ( > 67%) included perineural invasion (PNI) (40% vs. 21%, p = 0.011), necrosis (67% vs. 41%, p = 0.003), lymph node positivity (32% vs. 14%, p = 0.027), and small tumor size ( < 6.8 cm vs. > 8.4cm, p = 0.014). Stratification of HA staining by median positivity value was not an independent predictor of survival based on multivariate analysis. OS for patients with HA > 67% was 40.1 months (mo) vs 48.5 mo with HA ≤ 67%, p = 0.537. PFS for patients with HA > 67% was 14.4 mo vs. 25.7 mo with HA ≤ 67%, p = 0.177. Conclusions: Prevalence of HA staining in resected CCA is higher than seen in many solid tumors and is ubiquitous in our study. Absence of statistically significant association with OS and PFS might be attributable to ubiquitous prevalence, narrow signal range, and association with known negative prognostic factors. Further pre-clinical and clinical evaluation would be warranted.

Abstract 2392: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models

Hyaluronan (also known as hyaluronic acid or HA) is a nonsulfated glycosaminoglycan in the extracellular matrix. Elevated levels of HA in the tumor microenvironment have been associated with poor prognosis of several human cancers, including pancreatic, breast, colon and prostate. In many cases of breast cancer, HA is found to be associated with the stromal compartment. To understand the interaction between tumor cells and HA containing stromal compartment, we engineered a HA-high stromal cell line by overexpressing the human HAS3 gene in Balb/c 3T3 fibroblast cells. In vitro, the 3T3/HAS3 cells produced and secreted HA, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Furthermore, depletion of HA with PEGPH20 (a pegylated form of the recombinant human PH20 protein) significantly inhibited the growth of MDA-MB-468 cells co-grafted with 3T3/HAS3 cells, suggesting that the HA provided by 3T3/HAS3 cells is critical for the growth of MDA-MB-468 cells in vivo. Immunohistochemical analysis of tumor xenograft samples showed that HA-low MDA-MB-468 cells were surrounded by HA-high stromal cells, resembling the tumor morphology observed in certain breast cancer patients. To model for breast cancers with tumor cell-associated HA, we overexpressed the human HAS3 gene directly in MDA-MB-468 cells. The in vivo growth of MDA-MB-468 was significantly enhanced by HAS3 overexpression. Depletion of HA by PEGPH20 synergized with Abraxane and improved its anti-cancer efficacy in the MDA-MB-468/HAS3 xenograft model compared to PEGPH20 and Abraxane alone. Taken together, we have developed tumor xenograft models that mimic HA-high breast cancers and can be used to test the pharmacological activity of anticancer agents. Further characterization of these models will provide insights into the understanding of the mechanisms by which increased levels of HA and the associated changes in the tumor microenvironment promote the disease progression in breast cancer and how depletion of HA can interfere with this process and synergize with chemotherapies to inhibit tumor progression.

Citation Format: Chunmei Zhao, Mathieu Marella, Susan Zimmerman, Lei Huang, H. Michael Shepard, Zhongdong Huang. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2015-2392

Long-term evaluation of Leber's hereditary optic neuropathy-like symptoms in rotenone administered rats

Leber's hereditary optic neuropathy (LHON) is an inherited disorder affecting the retinal ganglion cells (RGCs) and their axons that lead to the loss of central vision. This study is aimed at evaluating the LHON symptoms in rats administered with rotenone microspheres into the superior colliculus (SC). Optical coherence tomography (OCT) analysis showed substantial loss of retinal nerve fiber layer (RNFL) thickness in rotenone injected rats. Optokinetic testing in rotenone treated rats showed decrease in head-tracking response. Electrophysiological mapping of the SC surface demonstrated attenuation of visually evoked responses; however, no changes were observed in the ERG data. The progressive pattern of disease manifestation in rotenone administered rats demonstrated several similarities with human disease symptoms. These rats with LHON-like symptoms can serve as a model for future investigators to design and implement reliable tests to assess the beneficial effects of therapeutic interventions for LHON disease.

Complex I inhibition in the visual pathway induces disorganization of the node of Ranvier

Mitochondrial defects can have significant consequences on many aspects of neuronal physiology. In particular, deficiencies in the first enzyme complex of the mitochondrial respiratory chain (complex I) are considered to be involved in a number of human neurodegenerative diseases. The current work highlights a tight correlation between the inhibition of complex I and the state of axonal myelination of the optic nerve. Exposing the visual pathway of rats to rotenone, a complex I inhibitor, resulted in disorganization of the node of Ranvier. The structure and function of the node depend on specific cell adhesion molecules, among others, CASPR (contactin associated protein) and contactin. CASPR and contactin are both on the axonal surfaces and need to be associated to be able to anchor their myelin counterpart. Here we show that inhibition of mitochondrial complex I by rotenone in rats induces reactive oxygen species, disrupts the interaction of CASPR and contactin couple, and thus damages the organization and function of the node of Ranvier. Demyelination of the optic nerve occurs as a consequence which is accompanied by a loss of vision. The physiological impairment could be reversed by introducing an alternative NADH dehydrogenase to the mitochondria of the visual system. The restoration of the nodal structure was specifically correlated with visual recovery in the treated animal.

A phenotypic model recapitulating the neuropathology of Parkinson's disease

This study was undertaken to develop a phenotypic model recapitulating the neuropathology of Parkinson's disease (PD). Such a model would show loss of dopamine in the basal ganglia, appearance of Lewy bodies, and the early stages of motor dysfunction. The model was developed by subcutaneously injecting biodegradable microspheres of rotenone, a complex I inhibitor in 8-9 month old, ovariectomized Long-Evans rats. Animals were observed for changes in body weight and motor activity. At the end of 11-12 weeks animals were euthanized and the brains examined for histopathological changes. Rotenone treated animals gain weight and appear normal and healthy as compared to controls but showed modest hypokinesia around 5-6 weeks posttreatment. Animals showed loss of dopaminergic (DA) neurons and the appearance of putative Lewy bodies in the substantia nigra. Neuroinflammation and oxidative stress were evidenced by the appearance of activated microglia, iron precipitates, and 8-oxo-2'-deoxyguanosine a major product of DNA oxidation. The dorsal striatum, the projection site of midbrain DA neurons, showed a significant reduction in tyrosine hydroxylase immunostaining, together with an increase in reactive astrocytes, an early sign of DA nerve terminal damage. Levels of vesicular monoamine transporter 2 (VMAT2) were significantly reduced in the dorsal striatum; however, there was an unexpected increase in dopamine transporter (DAT) levels. Old, ovariectomized females treated with rotenone microspheres present with normal weight gain and good health but a modest hypokinesia. Accompanying this behavioral phenotype are a constellation of neuropathologies characteristic of PD that include loss of DA neurons, microglia activation, oxidative damage to nuclear DNA, iron deposition, and appearance of putative Lewy bodies. This phenotypic model recapitulating the neuropathology of Parkinson's disease could provide insight into early mechanisms of pathogenesis and could aid in the identification of biomarkers to identify patients in early stage, PD.

No immune responses by the expression of the yeast Ndi1 protein in rats

Background

The rotenone-insensitive internal NADH-quinone oxidoreductase from yeast, Ndi1, has been shown to work as a replacement molecule for complex I in the respiratory chain of mammalian mitochondria. In the so-called transkingdom gene therapy, one major concern is the fact that the yeast protein is foreign in mammals. Long term expression of Ndi1 observed in rodents with no apparent damage to the target tissue was indicative of no action by the host's immune system.

Methodology/Principal Findings

In the present study, we examined rat skeletal muscles expressing Ndi1 for possible signs of inflammatory or immune response. In parallel, we carried out delivery of the GFP gene using the same viral vector that was used for the NDI1 gene. The tissues were subjected to H&E staining and immunohistochemical analyses using antibodies specific for markers, CD11b, CD3, CD4, and CD8. The data showed no detectable signs of an immune response with the tissues expressing Ndi1. In contrast, mild but distinctive positive reactions were observed in the tissues expressing GFP. This clear difference most likely comes from the difference in the location of the expressed protein. Ndi1 was localized to the mitochondria whereas GFP was in the cytosol.

Conclusions/Significance

We demonstrated that Ndi1 expression did not trigger any inflammatory or immune response in rats. These results push forward the Ndi1-based molecular therapy and also expand the possibility of using foreign proteins that are directed to subcellular organelle such as mitochondria.

Successful amelioration of mitochondrial optic neuropathy using the yeast NDI1 gene in a rat animal model

Background

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder with point mutations in mitochondrial DNA which result in loss of vision in young adults. The majority of mutations reported to date are within the genes encoding the subunits of the mitochondrial NADH-quinone oxidoreductase, complex I. Establishment of animal models of LHON should help elucidate mechanism of the disease and could be utilized for possible development of therapeutic strategies.

Methodology/Principal Findings

We established a rat model which involves injection of rotenone-loaded microspheres into the optic layer of the rat superior colliculus. The animals exhibited the most common features of LHON. Visual loss was observed within 2 weeks of rotenone administration with no apparent effect on retinal ganglion cells. Death of retinal ganglion cells occurred at a later stage. Using our rat model, we investigated the effect of the yeast alternative NADH dehydrogenase, Ndi1. We were able to achieve efficient expression of the Ndi1 protein in the mitochondria of all regions of retinal ganglion cells and axons by delivering the NDI1 gene into the optical layer of the superior colliculus. Remarkably, even after the vision of the rats was severely impaired, treatment of the animals with the NDI1 gene led to a complete restoration of the vision to the normal level. Control groups that received either empty vector or the GFP gene had no effects.

Conclusions/Significance

The present study reports successful manifestation of LHON-like symptoms in rats and demonstrates the potential of the NDI1 gene therapy on mitochondrial optic neuropathies. Our results indicate a window of opportunity for the gene therapy to be applied successfully after the onset of the disease symptoms.

Parkinson's disease and mitochondrial complex I: a perspective on the Ndi1 therapy

Mitochondrial impairment has been collecting more and more attention as a contributing factor to the etiology of Parkinson's disease. Above all, the NADH-quinone oxidoreductase, complex I, of the respiratory chain seems to be most culpable. Complex I dysfunction is translated to an increased production of reactive oxygen species and a decreased energy supply. In the brain, the dopaminergic neurons are one of the most susceptible cells. Their death is directly linked to the disease apparition. Developing an effective gene therapy is challenged by harmful actions of reactive oxygen species. To overcome this problem a therapeutic candidate must be able to restore the NADH-quinone oxidoreductase activity regardless of how complex I is impaired. Here we discuss the potency of the yeast alternative NADH dehydrogenase, the Ndi1 protein, to reinstate the mitochondrial respiratory chain compensating for disabled complex I and the benefit Ndi1 brings toward retardation of Parkinson's disease.

Protection by the NDI1 gene against neurodegeneration in a rotenone rat model of Parkinson's disease

It is widely recognized that mitochondrial dysfunction, most notably defects in the NADH-quinone oxidoreductase (complex I), is closely related to the etiology of sporadic Parkinson's disease (PD). In fact, rotenone, a complex I inhibitor, has been used for establishing PD models both in vitro and in vivo. A rat model with chronic rotenone exposure seems to reproduce pathophysiological conditions of PD more closely than acute mouse models as manifested by neuronal cell death in the substantia nigra and Lewy body-like cytosolic aggregations. Using the rotenone rat model, we investigated the protective effects of alternative NADH dehydrogenase (Ndi1) which we previously demonstrated to act as a replacement for complex I both in vitro and in vivo. A single, unilateral injection of recombinant adeno-associated virus carrying the NDI1 gene into the vicinity of the substantia nigra resulted in expression of the Ndi1 protein in the entire substantia nigra of that side. It was clear that the introduction of the Ndi1 protein in the substantia nigra rendered resistance to the deleterious effects caused by rotenone exposure as assessed by the levels of tyrosine hydroxylase and dopamine. The presence of the Ndi1 protein also prevented cell death and oxidative damage to DNA in dopaminergic neurons observed in rotenone-treated rats. Unilateral protection also led to uni-directional rotation of the rotenone-exposed rats in the behavioral test. The present study shows, for the first time, the powerful neuroprotective effect offered by the Ndi1 enzyme in a rotenone rat model of PD.

Nonpsychoactive cannabidiol prevents prion accumulation and protects neurons against prion toxicity

Prion diseases are transmissible neurodegenerative disorders characterized by the accumulation in the CNS of the protease-resistant prion protein (PrPres), a structurally misfolded isoform of its physiological counterpart PrPsen. Both neuropathogenesis and prion infectivity are related to PrPres formation. Here, we report that the nonpsychoactive cannabis constituent cannabidiol (CBD) inhibited PrPres accumulation in both mouse and sheep scrapie-infected cells, whereas other structurally related cannabinoid analogs were either weak inhibitors or noninhibitory. Moreover, after intraperitoneal infection with murine scrapie, peripheral injection of CBD limited cerebral accumulation of PrPres and significantly increased the survival time of infected mice. Mechanistically, CBD did not appear to inhibit PrPres accumulation via direct interactions with PrP, destabilization of PrPres aggregates, or alteration of the expression level or subcellular localization of PrPsen. However, CBD did inhibit the neurotoxic effects of PrPres and affected PrPres-induced microglial cell migration in a concentration-dependent manner. Our results suggest that CBD may protect neurons against the multiple molecular and cellular factors involved in the different steps of the neurodegenerative process, which takes place during prion infection. When combined with its ability to target the brain and its lack of toxic side effects, CBD may represent a promising new anti-prion drug.

Mechanism of cell death caused by complex I defects in a rat dopaminergic cell line

Defects in the proton-translocating NADH-quinone oxidoreductase (complex I) of mammalian mitochondria are linked to neurodegenerative disorders. The mechanism leading to cell death elicited by complex I deficiency remains elusive. We have shown that expression of a rotenone-insensitive yeast NADH-quinone oxidoreductase (Ndi1) can rescue mammalian cells from complex I dysfunction. By using the Ndi1 enzyme, we have investigated the key events in the process of cell death using a rat dopaminergic cell line, PC12. We found that complex I inhibition provokes the following events: 1) activation of specific kinase pathways; 2) release of mitochondrial proapoptotic factors, apoptosis inducing factor, and endonuclease G. AS601245, a kinase inhibitor, exhibited significant protection against these apoptotic events. The traditional caspase pathway does not seems to be involved because caspase 3 activation was not observed. Our data suggest that overproduction of reactive oxygen species (ROS) caused by complex I inhibition is responsible for triggering the kinase activation, for the release of the proapoptotic factors, and then for cell death. Nearly perfect prevention of apoptotic cell death by Ndi1 agrees with our earlier observation that the presence of Ndi1 diminishes rotenone-induced ROS generation from complex I. In fact, this study demonstrated that Ndi1 keeps the redox potential high even in the presence of rotenone. Under these conditions, ROS formation by complex I is known to be minimal. Possible use of our cellular model is discussed with regard to development of therapeutic strategies for neurodegenerative diseases caused by complex I defects.

The single subunit NADH dehydrogenase reduces generation of reactive oxygen species from complex I

Using rat dopaminergic and human neuroblastoma cell lines transduced with the NDI1 gene encoding the internal NADH dehydrogenase (Ndi1) from Saccharomyces cerevisiae, we investigated reactive oxygen species (ROS) generation caused by complex I inhibition. Incubation of non-transduced cells with rotenone elicited oxidative damage to mitochondrial DNA as well as lipid peroxidation. In contrast, oxidative stress was significantly decreased when the cells were transduced with NDI1. Furthermore, mitochondria from the NDI1-transduced cells showed a suppressed rate of ROS formation by the complex I inhibitors. We conclude that the Ndi1 enzyme is able to suppress ROS overproduction from defective complex I.

Can a Single Subunit Yeast NADH Dehydrogenase (Ndi1) Remedy Diseases Caused by Respiratory Complex I Defects?

The proton-translocating NADH-quinone oxidoreductase (complex I) is one of five enzyme complexes in the oxidative phosphorylation system in mammalian mitochondria. Complex I is composed of 46 different subunits, 7 of which are encoded by mitochondrial DNA. Defects of complex I are involved in many human mitochondrial diseases; therefore, the authors proposed to use the NDI1 gene encoding a single subunit NADH dehydrogenase of Saccharomyces cerevisiae for repair of respiratory activity. The yeast NDI1 gene was successfully introduced into 10 mammalian cell lines (two of which were complex I-deficient mutants). The expressed Ndi1 protein was correctly targeted to the matrix side of the inner mitochondrial membranes, was fully functional, and restored the NADH oxidase activity to the complex I-deficient cells. The NDI1-transduced cells were more resistant to complex I inhibitors and diminished production of reactive oxygen species. It was further shown that the Ndi1 protein can be functionally expressed in tissues such as skeletal muscles and brain of rodents. The Ndi1 expression scarcely induced an inflammatory response as assessed by hematoxylin and eosin (H&E) staining. The Ndi1 protein expressed in the substantia nigra (SN) elicited protective effects against neurodegeneration caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment. The Ndi1 protein has a great potential as a molecular remedy for complex I deficiencies.

Possibility of transkingdom gene therapy for Complex I diseases

Defects of complex I are involved in many human mitochondrial diseases, and therefore we have proposed to use the NDI1 gene encoding a single subunit NADH dehydrogenase of Saccharomyces cerevisiae for repair of respiratory activity. The yeast NDI1 gene was successfully introduced into mammalian cell lines. The expressed NDI1 protein was correctly targeted to the matrix side of the inner mitochondrial membranes, was fully functional and restored the NADH oxidase activity to the complex I-deficient cells. The NDI1-transduced cells were more resistant to complex I inhibitors and diminished production of reactive oxygen species induced by rotenone. It was further shown that the NDI1 protein can be functionally expressed in tissues such as skeletal muscles and the brain of rodents, which scarcely induced an inflammatory response. The use of NDI1 as a potential molecular therapy for complex I-deficient diseases is briefly discussed, including the proposed animal model.

Pathological Prion Protein Exposure Switches on Neuronal Mitogen-activated Protein Kinase Pathway Resulting in Microglia Recruitment

Transmissible spongiform encephalopathies are accompanied by the recruitment of microglial cells in the vicinity of amyloid aggregates of the pathological prion protein (PrPres). We previously showed that PrPres itself triggered the recruitment of microglia by interacting with neurons leading to the up-regulation of the expression level of chemokines, mainly RANTES (regulated on activation normal T cell expressed and secreted). The intracellular mechanisms underlying the PrPres-inducible expression of chemokines in this setting are not clear. Here we demonstrate that the mitogen-activated protein kinase pathway is switched on shortly after PrPres exposure to neurons leading to the expression of early growth response factor-1 (Egr-1), a transcription factor initially linked to differentiation and growth and to up-regulation of RANTES mRNA expression. PD98059, a selective inhibitor of extracellular signal-regulated kinase1/2 activation, resulted in a decrease of RANTES mRNA expression and as a consequence to the lowering of microglial cell migration. Neuronal overexpression of Nab2, a corepressor of Egr-1, produced similar effects. PrPres-induced chemoattraction is independent of the presence of PrPc and the laminin receptor on the neuronal cell surface. Our report is the first demonstration that PrPres exposure on neurons results in the activation of the MAP kinase signaling pathway that acts as a master switch to trigger neuronal expression of regulators of chemoattraction.

Neurons and astrocytes respond to prion infection by inducing microglia recruitment

The accumulation and activation of microglial cells at sites of amyloid prion deposits or plaques have been documented extensively. Here, we investigate the in vivo recruitment of microglial cells soon after intraocular injection of scrapie-infected cell homogenate (hgtsc+) using immunohistochemistry on retinal sections. A population of CD11b/CD45-positive microglia was specifically detected within the ganglion and internal plexiform retinal cell layers by 2 d after intravitreal injection of hgtsc+. Whereas no chemotactism properties were ascribed to hgtsc+ alone, a massive migration of microglial cells was observed by incubating primary cultured neurons and astrocytes with hgtsc+ in a time- and concentration-dependent manner. hgtsc+ triggered the recruitment of microglial cells by interacting with both neurons and astrocytes by upregulation of the expression levels of a broad spectrum of neuronal and glial chemokines. We show that, in vitro and in vivo, the microglia migration is at least partly under the control of chemokine receptor-5 (CCR-5) activation, because highly specific CCR-5 antagonist TAK-779 significantly reduced the migration rate of microglia. Activated microglia recruited in the vicinity of prion may, in turn, cause neuronal cell damage by inducing apoptosis. These findings provide insight into the understanding of the cell-cell communication that takes place during the development of prion diseases.

Specific inhibition of pathological prion protein accumulation by small interfering RNAs

Development of transmissible spongiform encephalopathies (TSEs) pathogenesis requires the presence of both the normal host prion protein (PrP-sen) and the abnormal pathological proteinase-K resistant isoform (PrP-res). PrP-res forms highly insoluble aggregates, with self-perpetuating properties, by binding and converting PrP-sen molecules into a likeness of themselves. In the present report, we show that small interfering RNA (siRNA) duplexes trigger specific Prnp gene silencing in scrapie-infected neuroblastoma cells. A non-passaged, scrapie-infected culture transfected with siRNA duplexes is depleted of PrP-sen and rapidly loses its PrP-res content. The use of different murine-adapted scrapie strains and host cells did not influence the siRNA-induced gene silencing efficiency. More than 80% of transfected cells were positive for the presence of fluorescein-labeled siRNA duplexes. No cytotoxicity associated with the use of siRNA was observed during the time course of these experiments. Despite a transient abrogation of PrP-res accumulation, our results suggest that the use of siRNA may provide a new and promising therapeutic approach against prion diseases.

Filipin prevents pathological prion protein accumulation by reducing endocytosis and inducing cellular PrP release

Conversion of the normal membrane-bound prion protein (PrP-sen) to its pathological isoform (PrP-res) is a key event in the pathogenesis of transmissible spongiform encephalopathies. Although the subcellular sites of conversion are poorly characterized, several lines of evidence have suggested the involvement of membrane lipid rafts in the conversion process. Here we report that copper stimulates the endocytosis of PrP-sen via a caveolin-dependent pathway in both microglia and neuroblastoma cells. We show that the polyene antibiotic filipin both limits endocytosis of PrP-sen and dramatically reduces the amount of membrane-bound PrP-sen. This reduction results from a rapid and massive release of full matured PrP-sen into the culture medium. Finally, we demonstrate that filipin is a potent inhibitor of PrP-res formation into chronically infected neuroblastoma cells. Our results reinforce the role of rafts in PrP trafficking and raise the possibility that the release of PrP-sen from the plasma membrane decreases the amount of available substrate PrP-sen at the conversion sites.