OP0243 AN APPROACH COMBINING TRANSCRIPTOMIC AND TOPOGRAPHIC ANALYSIS REVEALS A POTENTIAL ROLE OF PROTEASOME AND AUTOPHAGY DEREGULATION IN THE PATHOPHYSIOLOGY OF DERMATOMYOSITIS

Background:

Dermatomyositis (DM) is a rare autoimmune muscle disease characterized by an atrophy and a type-I interferon signature in perifascicular fibers. We recently showed that muscle mitochondrial dysfunction is also a characteristic of this disease that participates to both decrease exercise capacity and maintenance of inflammation (1). Pathophysiological mechanisms underlying these characteristics are unknown.

Objectives:

The objective of this study is to reveal the mechanisms underlying the modifications of perifascicular fibers during DM, taking advantage of a method combining transcriptomic and topographical information.

Methods:

Fourteen patients with recent (<6 months) untreated myositis (DM: n=7, other myositis: n=7) who underwent a biopsy of the deltoid muscle for diagnostic purposes were included. Seven other patients with suspected but not confirmed neuromuscular pathology (normal creatine kinase level, electromyogram and deltoid biopsy) were also included (no myopathy: n=7). Under the control of optical microscopy, perifascicular fibers (about 400 fibers) and endofascicular fibers (about 400 fibers) were microdissected by laser. The transcriptome of endofascicular fibers and perifascicular fibers in all three groups of patients were then obtained by massive sequencing of total messenger RNA. The DAVID database (2) (http://david.abcc.ncifcrf.gov) were used to determine the deregulated molecular pathways in the perifascicular fibers during DM.

Results:

482 transcripts were differently expressed in perifascicular fibers of patients with DM compared to perifascicular fibers of the 2 other groups (348 overexpressed and 134 underexpressed). The most overexpressed transcripts were involved in the type I interferon response while the most underexpressed transcripts were involved in mitochondria and in proteasome functioning. The study of the transcripts differentially expressed in perifasicular versus endofascicular fibers revealed that there is a physiological perifascicular signature: in patients without myopathy, 83 genes were overexpressed and 54 were underexpressed in perifascicular fibers compared to endofascicular fibers. This physiological perifascicular signature was abolished in patient with myositis (DM and other myositis). In the group of patients with DM (but not other myositis), a specific perifascicular signature (18 genes overexpressed and 10 genes underexpressed in perifascicular fibers compared to endofascicular fibers) was identified. The most deregulated transcripts in DM perifascicular fibers were involved in autophagy/mitophagy, mitochondria and proteasome pathways.

Conclusion:

In the physiological state, perifascicular fibers are characterized by a different transcriptomic profile from endofascicular fibers. During DM, this physiological perifascicular signature is abolished and replaced by a transcriptomic signature that reveal a potential role of proteasome and autophagy deregulation in the pathophysiology of DM.

References:

[1]Meyer et al. IFN-β-induced reactive oxygen species and mitochondrial damage contribute to muscle impairment and inflammation maintenance in dermatomyositis Acta Neuropathol. 2017;134:655-666.

[2]Huang, D. W. et al. The DAVID Gene Functional Classification Tool: a novel biological module-centric algorithm to functionally analyze large gene lists. Genome Biol 8, R183 (2007).

Disclosure of Interests:

None declared

HER2 status determined on pre operative biopsies and in operative specimens: concordance among immunohistochemistry (IHC) fluorescence in situ hybridization (FISH) and chromogenic in situ hybridization (CISH) techniques in the CRITHER study

Abstract #1089

Background: In breast cancer, HER2 status is generally assessed by IHC or FISH on operative tissue sample and in situ hybridization techniques are standard tools for determining equivocal IHC 2+ overexpression and deciding the correct treatment for HER2-positive breast cancer patients. For the management of their patients, oncologists or surgeons sometimes ask for assessment of HER2 status on per cutaneous core biopsy (CB).The primary objective of the CRITHER study was to investigate concordance between the results of CISH, FISH, and IHC techniques on pre-operative CB samples for HER2 status compared with HER2 status determined by FISH on surgical specimen from a population of previously untreated non-metastatic breast cancer patients in France. Methods: Analysis was performed on samples from 260 patients recruited at 24 pathology centers for the period 2003 to 2006 inclusive. Recruitment was made on the basis of IHC obtained from operative tissue samples in order to obtain around 50% HER2-positive (3+), 30% HER2-negative (0/1+), and 20% HER2-equivocal (2+) cases. CISH and IHC were performed in parallel on the pre-operative biopsy and matched surgical specimen in the participating laboratories, and FISH on both specimens in each of four reference pathology centers. IHC staining was analyzed according to different scoring systems. Results: The rate of discordance between pre-operative CISH and operative FISH was 1.8% with 1.5% false-positives and 2.2% false-negatives (k=0.963; p&lt;0.001); the corresponding rate for pre-operative IHC (excluding equivocal IHC 2+ cases) and operative FISH was 1.5% with 1.6% false-positives and 1.4% false-negatives (k=0.953; p&lt;0.001). Comparison of pre-operative and operative samples showed expected low rates of discordance for CISH (0.85%; k=0.982; p&lt;0.001) and FISH (0.45%; k=0.991; p&lt;0.001), with no false positives in either case. Results for the IHC scoring system analyses on concordance will be presented at the meeting. Discussion: As expected, concordance for both CISH and FISH between pre-operative and operative results was excellent. There was a high rate of concordance for pre-operative CISH and IHC HER2 status determination on CB (excluding equivocal IHC 2+ cases) compared with operative FISH results in patients with previously untreated non-metastatic breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1089.

Fluorescence in situ hybridization (FISH) technique by reference centers for HER2 status determination in metastatic breast cancer: quality assurance results of FISH 2002 study

Abstract #2069

Background: Concordance between IHC and FISH in local and regional centers was evaluated in the FISH 2002 Study. Primary metastatic breast cancer (MBC) tumor samples were tested by IHC for HER2 status according to in-house techniques at 18 regional (n=871) and 81 peripheral (n=670) centers in France between 2002 and 2006. All samples were tested by FISH at regional centers [Penault-Llorca et al. SABCS 2006]. This second part of the study comprises quality assurance evaluation of FISH techniques.&#x2028; Methods: 464 cases were selected according to the protocol and were either re-assessed using archived pictures or retested by 3 reference centers (Clermont-Ferrand, Strasbourg, Paris-Curie). 246 samples were re-assessed and 166 were retested.&#x2028; Results:Global discordance combining re-assessment and retesting results was 10.7% in the first half of the study and 5.1% in the second part (p=0.041).&#x2028; &#x2028; Discussion: Concordance was excellent for negative (100%) and IHC 2+ cases (97%). Among low amplification cases (≥6 and &lt;8 copies), 70% were concordant: discordant cases were mainly interpretation pitfalls of polysomic cases, emphasizing the importance of double-stained FISH analyses. These quality assurance results demonstrate that overall concordance and quality of HER2 status determined by FISH has improved significantly over time. This improvement is likely to be related to introduction of rigorous quality control procedures, training, and education, all of which should be continued.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2069.

[HER2 gene amplification assay: is CISH an alternative to FISH?]

The HER2 proto-oncogene encodes a transmembrane protein, which is considered to function as a growth factor receptor. Overexpression of this protein found by immunohistochemistry in about 20% of infiltrating breast carcinomas, has a predictive value of response to treatment by trastuzumab, an anti-HER2 humanized monoclonal antibody. Search for HER2 gene amplification is necessary to adapt the immunohistochemical technique quality and also in the cases of delicate analysis or weak overexpression. It is usually carried out by Fluorescence In Situ Hybridization (FISH). A more recent hybridization technique, named CISH because of its chromogenic revelation is an alternative method, which gives highly correlated results with FISH. We present details of this technique, which may be more familiar for the pathologists than FISH, because reading analysis is similar to that of immunohistochemical staining.

Sensitization of the striatal dopaminergic system induced by chronic administration of a glutamate antagonist in the rat

The aim of the present study was to assess in the rat the pharmacological, biochemical and molecular (including in situ hybridization) consequences in the striatum of a prolonged (50 days) treatment with dizocilpine maleate (MK-801), an N-methyl-D-aspartate (NMDA) antagonist. We observed a sensitization-like effect characterized by a behavioural hyperresponsiveness to an acute injection of haloperidol (0.25 mg/kg), a dopaminergic antagonist. In rats chronically treated with MK-801, this hyperresponsiveness was associated with an increased D2 receptor (D2R) density in the striatum. At the transcriptional level, the D2R mRNA was also enhanced in the striatum. Quantitative in situ hybridization studies revealed that the number of neurons expressing the D2R mRNA was significantly enhanced in treated rats, whereas the mean amount of message per cell was unchanged. These changes could represent the neurobiological substrate of the observed sensitization. These results suggest that the D2R gene is under glutamate control via NMDA receptor in striatal neurons.

kappa-Opioid receptor in humans: cDNA and genomic cloning, chromosomal assignment, functional expression, pharmacology, and expression pattern in the central nervous system

Using the mouse delta-opioid receptor cDNA as a probe, we have isolated genomic clones encoding the human mu- and kappa-opioid receptor genes. Their organization appears similar to that of the human delta receptor gene, with exon-intron boundaries located after putative transmembrane domains 1 and 4. The kappa gene was mapped at position q11-12 in human chromosome 8. A full-length cDNA encoding the human kappa-opioid receptor has been isolated. The cloned receptor expressed in COS cells presents a typical kappa 1 pharmacological profile and is negatively coupled to adenylate cyclase. The expression of kappa-opioid receptor mRNA in human brain, as estimated by reverse transcription-polymerase chain reaction, is consistent with the involvement of kappa-opioid receptors in pain perception, neuroendocrine physiology, affective behavior, and cognition. In situ hybridization studies performed on human fetal spinal cord demonstrate the presence of the transcript specifically in lamina II of the dorsal horn. Some divergences in structural, pharmacological, and anatomical properties are noted between the cloned human and rodent receptors.

Chronic treatment with dizocilpine maleate increases the number of striatal neurons expressing the D2 receptor gene

N-methyl-D-aspartate antagonists have been proposed as potential therapeutic agents in different neurological diseases, including Parkinson's disease. The effects of gene expression of a chronic treatment with the non-competitive N-methyl-D-aspartate antagonist, dizocilpine maleate (0.8 mg/kg day, per os for 50 days) were analysed in rat striata. Using quantitative in situ hybridization, we measured the messenger RNA expression of the genes encoding D1, D2 dopamine receptors, N-methyl-D-aspartate receptor 1 subunit of N-methyl-D-aspartate receptor, preproenkephalin A and substance P. Chronic treatment with dizocilpine maleate induced a moderate but significant increase in messenger RNA of the N-methyl-D-aspartate receptor 1 subunit in the striatum and the adjacent cortex, suggesting an action of dizocilpine maleate in these two regions. This treatment did not induce any change in D1 receptor, preproenkephalin A or substance P messenger RNA content in the striatum, whereas D2 receptor messenger RNA was increased in the striatum of treated rats. Microscopic analysis revealed that it was the number of medium-sized neurons expressing D2 receptor messenger RNA that was significantly enhanced, while the mean amount of message per cell remained unchanged. These results demonstrate that glutamate via N-methyl-D-aspartate receptors, regulates the D2 receptor gene in striatal neurons. A chronic treatment with dizocilpine maleate increases the number of striatal neurons expressing the D2 receptor gene, suggesting a recruiting phenomenon.

The human delta-opioid receptor: genomic organization, cDNA cloning, functional expression, and distribution in human brain

We have used the mouse delta-opioid receptor (mDOR) cDNA to isolate the mDOR gene and its human homologue. In both species the coding region is interrupted by two introns with conserved exon-intron boundaries located after transmembrane domains 1 and 4. Using the polymerase chain reaction and primers based on the sequence of the cloned human delta-opioid receptor (hDOR) gene, we have obtained a full length cDNA encoding the hDOR from SH-SY5Y neuroblastoma cells. The cDNA sequence is 100% identical to the cloned human genomic sequence and 94% identical to the mouse sequence at the protein level. When expressed in COS cells, hDOR displays nanomolar affinities for delta-selective ligands, whereas the affinities for mu- and kappa-selective ligands are in the micromolar range. The delta agonists [D-Ala2, D-Leu5]enkephalin, cyclic [D-penicillamine2,D-penicillamine5]enkephalin, and BW373U86 efficiently decrease forskolin-induced cAMP levels in hDOR-expressing COS cells, indicating functional coupling of the receptor. The distribution of hDOR mRNA in human brain was investigated using delta-selective reverse transcription-polymerase chain reaction amplification, followed by Southern hybridization with a delta-specific probe. The transcript is found in cortical areas, including olfactory bulb, hippocampus, and amygdala, as well as in basal ganglia and hypothalamus. No expression is detected in internal globus pallidus, thalamus, any investigated brainstem structure, or pituitary gland. Taken together, our results indicate similar structural, pharmacological, functional, and anatomical properties for the hDOR and the mDOR and therefore support the use of rodent models for the study of these receptors in opioid function.

[Anatomic-functional relationships between the motor systems and the sleep-wakefulness systems]

The present paper deals with relationships between neural systems which control motor behaviour (pyramidal and extrapyramidal) and sleep-wakefulness states (in particular the reticular formation). We examined successively their anatomical and neurochemical substrates, electrophysiological and functional motor alterations depending on ascending and descending influences from brain stem during the sleep-wakefulness cycle. These data suggest that sleep-wake states result from the modulation of excitability in neuronal pools and that each state results from the co-ordinated working of several functionally different neuronal pools. Thus, each state could be understood as a sum of behavioural events depending on a neural network. We hypothesized that abnormal motor events occurring specifically during a sleep state could result from motor structures abnormally recruited in neural networks specifically involved in this sleep state.

Chronic administration of NMDA antagonists induces D2 receptor synthesis in rat striatum

Dopamine D2 receptor gene expression was examined in rat striatum after chronic treatment with N-methyl-D-aspartate (NMDA) receptor antagonists (ketamine at 15 mg/kg/day or MK-801 at 0.1, 0.2 and 0.4 mg/kg/day per os, for 50 days). The long-isoform mRNA, as well as the total D2 mRNA expression were induced. No change was noticed in striatal dopamine release or turnover. D2 binding studies carried out in MK-801 chronically treated (0.3 mg/kg/day per os, for 50 days) and control rats revealed an increased receptor density in treated animals without a significant change in receptor affinity. These results suggest that the synthesis of both striatal D2 receptor isoforms is postsynaptically regulated at the transcriptional level, by events triggered by glutamate through the NMDA-type receptor.

Behavioural, pharmacological and biochemical effects of acute and chronic administration of ketamine in the rat

The effects of N-methyl-D-aspartate (NMDA) antagonist ketamine given acutely or chronically were investigated on dopamine-related motor functions. Acute administration (15, 22.5, 30 mg/kg, i.p.) reversed the catalepsy induced by a dopamine (DA) antagonist (haloperidol, 0.25 mg/kg, i.p.) in the rat. When given orally and chronically (15 mg/kg per day) during at least 60 days, no alteration of spontaneous motor behaviour was observed, but the responsiveness to a DA agonist (apomorphine, 0.125 or 0.25 mg/kg s.c.) and to haloperidol was enhanced, suggesting an hypersensitivity of the DA receptors following the chronic blockade of NMDA receptors. However, following prolonged administration of ketamine there were no alteration of DA levels and turnover. Taken together these results suggest that the mechanisms involved in this DA receptor hypersensitivity should be postsynaptic.

Lesions of noradrenergic neurons in rats with spontaneous generalized non-convulsive epilepsy

The role of noradrenergic neurons in the control of a spontaneous generalized non-convulsive epilepsy (GNCE) was investigated. In rats with genetic spontaneous absence seizures, we produced lesions using 2 neurotoxins: 6-hydroxydopamine (6-OHDA) and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). Lesions of noradrenergic neurons were made either in pups by neonatal 6-OHDA intraperitoneal (i.p.) injection (2 x 100 mg/kg) or in adult rats by i.p. administration of DSP4 (60 mg/kg) or bilateral microinjection of 6-OHDA in the locus coeruleus (LC) (4 micrograms/microliters, 2 microliters/side). Effectiveness of the lesions was controlled by measuring dopamine (DA) and noradrenaline (NA) contents in the brains. Neonatal 6-OHDA administration did not lead to any difference in seizures in adult animals, compared with control rats. DSP4 injections and LC lesions with local injections of 6-OHDA produced a transient increase of the seizures. Within one to two weeks, the seizure duration went back to prelesion levels. No seizure occurred when the same lesions were performed in non epileptic rats. These results suggest that NA is not involved in the genesis of this generalized non-convulsive epilepsy; they confirm that NA participates in the control of seizures in this model, but the rapid development of compensatory mechanisms shows that this control is not critical.

Local cerebral glucose utilization in rats with petit mal-like seizures

The quantitative 2-[14C]deoxyglucose autoradiographic method was applied to the measurement of local cerebral metabolic rates for glucose in a model of genetic petit mal-like seizures in a strain of Wistar rats. During the experimental period, epileptic rats exhibited synchronous spike-and-wave discharges recorded from the cerebral cortex, whereas the electroencephalographic pattern of control animals was normal. An overall consistent increase in local cerebral metabolic rates for glucose was observed in epileptic rats as compared to nonepileptic control rats. This increase was statistically significant in 52 of the 59 cerebral structures studied and concerned all cerebral functional systems. These results are in accordance with positron emission tomography measurements in humans with typical childhood absence epilepsy. There is a lack of anatomical correlation between areas demonstrating hypermetabolism and areas where spike-and-wave discharges are recorded. Thus, the diffuse increase in cerebral energy metabolism in epileptic rats as compared to controls is not directly related to the occurrence of spike and wave discharges.

Immediate effects of 14 non MAOI antidepressants in rats with spontaneous petit mal-like seizures

1. Wistar rats of a strain presenting spontaneous petit mal-like seizures were injected intraperitoneally with graded doses of 14 non-monoamine oxidase inhibitor antidepressants and the immediate effects on behavior and the EEG were recorded. 2. Amineptine and nomifensine, the two drugs interacting with dopaminergic neurotransmission, reduced the duration of spontaneous spike-wave discharges (SWD) and were thus potentially antiepileptic. 3. Trazodone increased SWD duration. 4. The antidepressants, imipramine-like (imipramine, chlorimipramine, desipramine, metapramine and amitriptyline) and non-imipraminic (minaprine, maprotiline, viloxazine, mianserin, fluvoxamine and indalpine), and the 3 noted above, had potentially convulsive effects.

Interhemispheric desynchronization of spontaneous spike-wave discharges by corpus callosum transection in rats with petit mal-like epilepsy

Wistar rats of a strain inbred for spontaneous generalized non-convulsive seizures present EEG spike-wave discharges (SWDs), 7-10 c/sec, occurring about once/min and lasting about 15 sec. They are bilateral and synchronous and can be recorded over the entire neocortex and in the lateral thalamic nuclei. After corpus callosum section, only a few bilateral SWDs persisted. Asymmetrical SWDs were most often recorded: bilateral SWDs starting asynchronously, or unilateral SWDs, which were also seen to alternate abruptly between hemispheres. The thalamic SWDs were always synchronized with the ipsilateral cortical pattern. These findings suggest that while the corpus callosum has a major role in bilateral synchronization of SWD in this model of epilepsy, occasional synchronization may still occur through other pathways after callosal transection.

Relationship between spike-wave discharges and vigilance levels in rats with spontaneous petit mal-like epilepsy

The relationship between states of vigilance and spike and wave discharges (SWD) was examined during 12 hours in 4 Wistar rats from a strain bred for spontaneous generalized non-convulsant seizures. On the basis of cortical and hippocampal EEG and EMG activity, wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (REM) were distinguished. Of the SWD 86% occurred during quiet W, 14% during the first minutes of SWS. No SWD occurred during active wakefulness and they were exceptional during REM. These results show that the states of quiet W and transitional states favour the SWD in rats with petit mal-like epilepsy, as in human petit mal.

Evidence that activation of GABA receptors in the substantia nigra suppresses spontaneous spike-and-wave discharges in the rat

The involvement of intranigral gamma-aminobutyric acid (GABA) receptors in the control of generalized non-convulsive epilepsy was investigated in a genetically determined model of petit mal epilepsy in the rat. Bilateral intranigral injection of muscimol (2 ng/0.2 microliter/side), a GABA agonist, significantly suppressed EEG-recorded spike-and-wave discharges for about 80 min, both at the cortical and thalamic levels. This suppressive effect was shown to be dose-dependent, reproduced by bilateral intranigral injections of 4,5,6,7-tetrahydro-isoxazolo [5,4-c]pyridin 3-ol (THIP), another GABA agonist, and reversed by a subsequent intranigral injection of bicuculline methiodide, a GABA antagonist. In addition, the anti-absence effects of bilateral intranigral injections of muscimol were well localized to the substantia nigra. Bilateral intranigral injections of GABA antagonists per se had no effects on the discharges. These results demonstrate that activation of GABA receptors in the substantia nigra suppresses the occurrence of spike-and-wave discharges in an animal model of generalized non-convulsive epilepsy. The results are compared to data obtained in models of generalized convulsive epilepsy and the hypothesis of nigral GABAergic mechanisms as a control system for generalized epilepsies is discussed.