Molecular biology of gliomas
Molecular biology of gliomas is complicated, and a small portion of complex mechanisms has been elucidated
though the ongoing intensive studies. Mostly studied groups are astrocytomas and oligodendrogliomas.
Astrocytoma may arise “de novo” as primary glioblastomas or may progress from lower grade tumors. IDH1
mutations are most commonly seen in this progression form low grade to high grade gliomas. p53 tumor
supressor gene mutations are common events in secondary gliomas followed by chromosome 7 gains and
platelet derived growth factor disorders and dysregulation of cell cycle. Cell cycle disorders with CDKN2A
deletions, chromosome 19q loss and PTEN loss are seen during malignant transformation. Primary
glioblastomas show EGFR disorders and loss of PTEN or chromosome 10. Loss of 1p/19q is typical for
oligodendroglial tumors. The cell of origin for glial tumors are still debatable. Disorders of genetic structure and
signal transduciton pathways are described in gliomas. Ras/MAPK and PTEN regulated PI3K/Akt pathways,
which are located downstream of EGFR are frequently affected. Moreover, angiogenesis and invasion are
regulated by growth factors such as EGFR and VEGF as well as proteases and integrins. Recently described
IDH1 and 2 mutations in glioma pathogenesis are more commonly use in clinical settings as prognostic factors.
In conclusion, better understanding of complex molecular mechanisms of proliferation, angiogenesis and
invasion of gliomas may lead to new avenues in targeted treatment of these tumors.
Paneller / Panels
39
Panel 6:
Beyin tümörlerinin moleküler biyolojisi
Molecular biology of brain tumors
Beyin Tümörlerinde ETS bölgesi transkripsiyon faktörlerinin rolü
Işıl Aksan-Kurnaz
Yeditepe Üniversitesi, Mühendislik ve Mimarlık Fakültesi, Genetik ve Biyomühendislik Bölümü, İstanbul
Yeditepe University, Faculty of Engineering and Architecture, Department of Genetics and Bioengineering, Istanbul, Turkey
AMAÇ : ETS bölgesi proteinlerinden Elk-1 genellikle mitojen üzerine aktif hale geçen ve MAPK yolağı tarafından
fosforlandıktan sonra c-fos gibi ilk-öncü genlerin transkripsiyonunda rol alan bir protein olarak
tanımlanmaktadır. Ancak beyin tümörlerinde aşırı anlatılan ve aşırı fosforlanan bu proteinin mitozun değişik
safhalarında nasıl davrandığı veya lokalizasyonu bilinmemektedir.
GEREÇ ve YÖNTEM : Bu çalışma sırasında hücre döngüsü ve özellikle mitozun değişik aşamalarında Elk-1
proteininin çeşitli fosfo-formlarının lokalizasyonu ve protein-protein etkileşimleri immünfloresan ve
immünçökeltme gibi yöntemlerle incelenmiştir.
BULGULAR : İlk defa bu çalışmada bir transaktivatör proteinin mitotik iğ iplikçiklerindeki hareketliliği
gösterilmiş ve bu hareketliliğin özellikle S383 fosforlanmasından kaynaklandığı bulunmuştur. Ayrıca daha once
hiç tanımlanmamış olan mitotic kinaz etkileşimleri de ilk defa bizim çalışmamızda gösterilmektedir.
SONUÇ : Çalışmamızın bulgularından yola çıkarak, Elk-1 proteininin mitoz sırasındaki hareketliliği ve DNA
dışındaki lokalizasyonları göz önüne alınarak, bu proteinin non-transkripsiyonel bazı görevleri de olabileceği
çıkarımında bulunmaktayız. Özellikle kromozom yolcu kompleksi ile muhtemel ilişkisi dikkat çekicidir.
Anahtar Kelimeler : Elk-1, Mitotik mikrotübül, Mitotik kinaz
TÜBİTAK 106S247 ve 109S230 projeleri ile Türk Kanser Araştırmaları Derneği tarafından desteklenmiş olup, IAK
TÜBA GEBİP ödülü tarafından desteklenmiştir.
The role of ETS transcription factor Elk-1 in brain tumors
OBJECTIVES: ETS domain transcription factor Elk-1 is commonly described as a protein that is activated in
response to mitogenic stimuli, get phosphorylated by the MAPK signaling pathway and play a role in
transcription of immediate-early genes such as c-fos. However the localization and function of Elk-1 in brain
tumors, where it is overexpressed and over-phosphorylated, is not known.
MATERIALS & METHODS: In this study we have analyzed the localization and protein-protein interactions of
various phosphor-forms of Elk-1 in the cell cycle and in particular in various phases of mitosis using different
methods including immunofluorescence and immunoprecipitation.
RESULTS: This study has shown for the first time the mobility of a transactivator protein on mitotic spindles
and that this mobility is partly due to Serine 383 phosphorylation. We have also shown for the first time
interactions with mitotic kinases.
CONCLUSION: Based on our observations on peculiar localization and mobility of Elk-1 on mitotic spindles we
conclude that this protein may indeed have a non-transcriptional role during mitosis. It is particularly
noteworthy to mention a putative interaction with chromosome passenger complex.
Keywords: Elk-1, Mitotic microtubule, Mitotic kinase
Paneller / Panels
40
Panel 6:
Beyin tümörlerinin moleküler biyolojisi
Molecular biology of brain tumors
Tümörün ilerlemesinde anjiyogenezin etkisi ve tedavi için fikirler
Rana Sanyal
Boğaziçi Üniversitesi, Kimya Bölümü, İstanbul
Boğaziçi University, Department of Chemistry, Istanbul, Turkey
Anjiyogenez, var olan damarlardan yeni damar oluşumudur. Normal şartlarda anjiyogenez yara iyileşmesinde
gerekli bir süreçtir, ancak düzensiz anjiyogenez tümör büyümesinde ve metastazında çok önemli bir rol oynar.
Büyüyen tümör oksijen ve besine ihtiyaç duyar, bu nedenle vasküler endotel büyüme faktörü (VEGF) gibi
büyüme faktörlerini salgılayarak yeni damarların oluşmasını kolaylaştırır. Gereken besinleri taşımaya yarayan bu
dengesiz ve düzensiz damarlar tümörün çapının 2mm’den daha fazla büyümesini mümkün kılar. Yani tümörün
büyümek için anjiyogenezi kullanması kaçınılmazdır. Bu kavram klinikte ilk olarak monoklonal antikor Avastin
(bevasicumab), daha sonra ise küçük organik moleküller olan Iressa (Gefitinib), Nexavar (Sorafenib), Sutent
(Sunitinib) ve Tarceva (Erlotinib) ile kanıtlanmıştır. Bu tebliğde, hem tümörde birikim gösterebilen hem de
tümör damarlanmasına etki edebilen yeni jenerasyon makromoleküler ajanlar tartışılacaktır.
Angiogenesis in tumor progression: effect and ideas for treatment
Angiogenesis is a term used for formation of new blood vessels from pre-existing vessels. Normally,
angiogenesis process is essential for wound healing yet, unregulated angiogenesis plays pivotal role in tumor
growth and metastasis. Growing tumor is in need of excess oxygen and nutrients, therefore secreting a variety
of growth factors like vascular endothelial growth factor (VEGF), it facilitates formation of new blood vessels.
This uneven and usually very disorganized blood vessels carrying the necessary nutrition, enable the tumor to
grow over 2mm in diameter. Thus it is essential for the tumor to use “angiogenesis” to grow. There has been
proof of this concept reaching clinic, first with a monoclonal antibody Avastin (bevasicumab), followed by small
molecule agents such as Iressa (Gefitinib), Nexavar (Sorafenib), Sutent (Sunitinib) and Tarceva (Erlotinib). In
this communication, newer generation of macromolecular agents that can accumulate in the tumor as well as
affect the tumor vasculature will be discussed.
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41
Panel 7:
Beyin osilasyonları ve klinik uygulamaları
Brain oscillations and their clinical applications
Event related oscillations and event related coherence in healthy subjects
Bahar Güntekin
Istanbul Kultur University, Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul, Turkey
OBJECTIVES: In this study, the long-distance intra-hemispheric event related coherence (auditory oddball
paradigm) and evoked coherence (simple sound) of healthy subjects were compared in order to evaluate the
effects of cognitive tasks on the long-distance coherences of healthy subjects.
MATERIALS & METHODS: 17 healthy subjects (8 female, 9 male) were included in the study. Simple auditory
stimuli and auditory oddball paradigm were used as stimuli. The coherence was analyzed for delta (1-3.5 Hz),
theta (4-7.5 Hz) and alpha (8-13 Hz) frequency ranges for (F
3-
P
3
, F
4-
P
4
, F
3-
T
7
, F
4-
T
8
, F
3-
O
1,
F
4-
O
2
) electrode pairs.
RESULTS: Target delta coherences were significantly higher than the non-target and simple auditory
stimulation delta coherences (p<0.0001). Furthermore left target theta coherences were significantly higher
than the left non-target theta coherences (p<0.005). The highest coherences were found at fronto-temporal
locations for all frequency bands (delta, theta, alpha) (p<0.05). Furthermore, fronto-parietal coherences were
higher than the fronto-occipital coherences for all frequency bands (delta, theta, alpha) (p<0.05). Alpha
response coherence values revealed no significant differences between target, non-target and simple auditory
stimulation.
CONCLUSION: These results show that the fronto-temporal and fronto-parietal connections are most relevant
for the identification of the target signal triggering focused attention and increase working memory. These
results may, in turn, serve in future to accomplish a more differentiated use for analysis in neuropsychiatric
patients.
Keywords: Event related coherence, Delta, Theta, Oddball paradigm
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42
Panel 7:
Beyin osilasyonları ve klinik uygulamaları
Brain oscillations and their clinical applications
Event related oscillations and event related coherence in euthymic patients
with bipolar disorder
Ayşegül Özerdem
1,2,3
1
Dokuz Eylul University, Faculty of Medicine, Department of Psychiatry, Izmir, Turkey
2
Dokuz Eylul University, Health Sciences Institute, Department of Neuroscience, Izmir, Turkey
3
Dokuz Eylul University, Multidisciplinary Brain Dynamics Research Center, Izmir, Turkey
OBJECTIVES: EEG coherence represents the brain’s functional connectivity. Synchronous neural gamma
oscillations are critical for cortico-cortical communication and large-scale integration of distributed sets of
neurons. The present study aims to analyze long distance gamma (28-48 Hz) coherence in drug-free euthymic
bipolar disorder.
MATERIALS & METHODS: Sensory evoked (EP) and event related (ER) coherence for the gamma frequency
band during simple light stimulation and visual odd-ball paradigm was assessed in 20 drug-free euthymic
bipolar patients in comparison to healthy controls. Groups were compared for the left (F
3-
T
3
, F
3-
TP
7
, F
3-
P
3
, F
3-
O
1
)
and right (F
4-
T
4
, F
4-
TP
8
, F
4-
P
4
, F
4-
O
2
) intra-hemispheric locations by means of a repeated measure analysis of
variance (ANOVA) and t-tests.
RESULTS: Patients showed significantly lower gamma coherence values in comparison to healthy subjects in
response to target stimuli at left (40.50% decrease, p
F3T7
:0.012) and right (28.85% decrease, p
F4T8
:0.034)
fronto-temporal, left (34.69% decrease; p
F3TP7
:0.007) and right (32.41% decrease; p
F4TP8
:0.016) fronto-
temporo-parietal locations. Coherence values for the non-target stimuli were significantly lower in the patients
at the right (43.10 % decrease, p
F4T8
: 0.004) and left (44.44% decrease, p
F3TP7
: 0.004) fronto-temporo-parietal
locations; EP coherence values did not differ significantly between the groups.
CONCLUSIONS: Bipolar patients present long distance functional connectivity disturbance during a cognitive
paradigm requiring attention and immediate recall. The finding corresponds to the underlying neurobiology of
cognitive impairments in bipolar disorder and raises the question of whether gamma coherence reduction may
be a candidate biomarker for bipolar disorder.
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43
Panel 7:
Beyin osilasyonları ve klinik uygulamaları
Brain oscillations and their clinical applications
Event related oscillations and event related coherence in patients with
alzheimer’s disease
Görsev G.Yener
1, 2, 3
1
Dokuz Eylul University, Brain Dynamics and Multidisciplinary Research Center, Izmir, Turkey
2
Dokuz Eylul University, Department of Neurosciences, Izmir, Turkey
3
Dokuz Eylul University, Department of Neurology, Izmir, Turkey
OBJECTIVES: In previous studies on Alzheimer’s patients it was shown that in frontal and parietal locations
delta and theta responses of AD patients have been highly reduced. The present study aims to analyze
coherence functions especially in these highly affected frontal and parietal areas.
MATERIALS & METHODS: Visual sensory and event related coherences of patients with Alzheimer type
dementia (AD) were comparatively analyzed. A total of 38 mild, probable AD subjects (19 untreated, 19 treated
with cholinesterase inhibitors) were compared with a group of 19 healthy controls. The sensory Evoked
Coherence and event related target coherences were analyzed for delta (1-3.5 Hz), theta (4-7 Hz), alpha (8-13
Hz), beta (15-30 Hz) and gamma (28-48 Hz) frequency ranges for long-range intra-hemispheric (F
3
-P
3
, F
4
-P
4
,
F
3
-T
5
, F
4
-T
6
, F
3
-O
1,
F
4
-O
2
) electrode pairs.
RESULTS: The healthy control group showed significantly higher values of Event Related Coherence in “delta”,
“theta” and “alpha” bands in comparison to the de novo and medicated AD groups (p<0.01 for the delta, theta
and alpha) upon application of a target stimuli. In contrast, almost no changes in event related coherences
were observed in beta and gamma frequency bands. Furthermore, no differences were recorded between
healthy and AD groups upon application of simple light stimuli. Besides this, coherence values upon application
of target stimuli were higher than sensory Evoked Coherence in all groups and in all frequency bands (p<0.01).
CONCLUSION: The cognitive networks of AD patients were highly impaired in comparison to networks
activated by sensory stimulation, thus showing separate activation of sensory and cognitive networks.
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44
Panel 7:
Beyin osilasyonları ve klinik uygulamaları
Brain oscillations and their clinical applications
Selective gamma activation in alzheimer’s disease, bipolar disorder and
schizophrenia
Erol Başar
1
, Canan Başar-Eroğlu
2
, Bahar Güntekin
1
, Ayşegül Özerdem
1,3,4,5
, Görsev G. Yener
1,3,4,6
1
Istanbul Kultur University, Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul, Turkey
2
University of Bremen, Institute of Psychology & Cognition Research, Bremen, Germany
3
Dokuz Eylul University, Health Sciences Institute, Department of Neuroscience, Izmir, Turkey
4
Dokuz Eylul University, Brain Dynamics and Multidisciplinary Research Center, Izmir, Turkey
5
Dokuz Eylul University, Faculty of Medicine, Department of Psychiatry, Izmir, Turkey;
6
Dokuz Eylul University, Faculty of Medicine, Department of Neurology, Izmir, Turkey
OBJECTIVES: For understanding significance of gamma activity in cognitive impairment three studies in
euthymic bipolar, schizophrenic and Alzheimer patients were undertaken. There are a wide range of hypotheses
and controversies on the functionality of the gamma activity. Is a multifold analysis of gamma activation open a
new neurophysiological understanding?
MATERIALS & METHODS: Applied methods have been the analysis of event related oscillations and
coherences.
RESULTS: (1) The long-distance event related coherences of all locations in 20 Alzheimer patients did not show
any change in comparison to healthy subjects (N=20) by application of visual targets during an oddball
paradigm. The coherences stayed around 0.60 in healthy and Alzheimer subjects. (Başar et al. Brain Res.
2010;1357: 79-90.).
(2) Contrarily, in euthymic bipolar patient’s event related fronto-temporal gamma coherences are significantly
reduced (approx. 40%). (Özerdem et al., Biol Psychiatry. 2010; (6):861-5).
(3) Başar-Eroğlu et al. (Int. J. Psychophysiol. 2007; 64 (1), 39–45.) investigated the modulation of event-
related gamma responses in tasks varying the WM load in patients with schizophrenia (N=10) and in healthy
controls (N=10). Gamma amplitude values were obtained for a simple choice reaction task, a low WM demand
task, and a high WM demand task. A gradual increase of gamma amplitudes upon stimulation was associated
with increase of WM load in controls. In contrast, high amplitude gamma oscillations remained constant in
patients, regardless of task difficulty.
CONCLUSION: The gamma activity studied in the three different diseases implies that a significant
differentiation by gamma band activation in cognitive impairment is evident. This may, in future, open the way
to consider the gamma activation selectivity as biomarker and also enable new physiological interpretation of
the gamma activity as universal operator in the brain.
Keywords: Event related oscillations, Event related coherence, Gamma, Pathology
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45
Panel 8:
Epilepside aktarımsal sinirbilim
Translational neuroscience in epilepsy
Altered information processing in dendrites in epilepsy
Christophe Bernard
Inserm U 751, 27 Bd Jean Moulin, 13385 Marseille Cedex 05, France
Information processing at the single cell level depends upon a complex interplay between synaptic inputs and
ionic channels. The distribution of many ionic channels is heterogeneous along the somato-dendritic axis of
hippocampal CA1 pyramidal cells. Using Kv4.2 K
+
and HCN1 (I
h
) as model channels, I’ll first show the
physiological impact of such heterogeneous distribution. I’ll then use the mechanisms underlying memory and
learning, to show that the distribution and activity of these channels can be modified dynamically, thus
modifying information processing in the dendritic tree. The distribution and properties of these channels is
modified in pathological conditions, such as epilepsy. Temporal lobe epilepsy (TLE), the most common form of
epilepsy in adults, is associated with acquired channelopathies affecting Kv4.2 and HCN1. I’ll show the
functional outcome of these modifications, and suggest how they can be related to memory deficits found in
experimental TLE. Finally, I’ll describe the epigenetic mechanism of the HCN1channelopathy and how it opens
the way to new therapeutic approaches.
Paneller / Panels
46
Panel 8:
Epilepside aktarımsal sinirbilim
Translational neuroscience in epilepsy
Talamus’un epileptik network’de rolü
Safiye Çavdar
Marmara Üniversitesi, Tıp Fakültesi, Anatomi Anabilim Dalı, İstanbul
Marmara University, Faculty of Medicine, Departmet of Anatomy, Istanbul, Turkey
Talamus, 3. ventrikül’ün iki yanında yer alır, oval şekilli gri cevher kitlesidir. Lamina medullaris interna yoluyla
farklı fonksiyon ile ilgili çeşitli nukleus gruplarına ayrılmıştır. Her bir nukleus aldığı spesifik uyarıları korteks’in
spesifik bölgesine iletir.
Son yıllarda çeşitli epilepsi tipleri ile yapılan çalışmalar talamus’un epilepsi mekanizmaları içinde yer aldığı
yolunda önemli ipuçları elde edilmiştir. Epilepsi sınıflamalarından generalize tipi epilepsilerden absans epilepsi
ve parsiyel kompleks tipi epilepsilerden mesiotemporal lob epilepsi (MTLE) ya da limbik epilepsi ile talamus
ilişkisi ele alınmıştır.
Absans Epilepsi ile talamus ilişkisi:
Absans epilepsi mekanizmasındaki primer network’de, korteks (kortikotalamik) ile talamus (talamokortikal)
nukleusları arasındaki resiprokal bağlantılar ve bu bağlantıları düzenleyen talmik retiküler nukleusun (TRN)
görevi rol oynar. TRN GABAerjik nöronlardan oluşur ve efferentleri sadece talamus nukleuslarıdır. Talamus
nukleuslarının toplam nöronlarının % 75 -85 iletici (relay) ve % 15 - 25’i ara nöronlardan oluşmakta
(interneuron). Talamus’un relay nöronları tonik ve burst mod’da ateşleme yapabilmekte
Tonik mod’da ateşleme eksitatuvardır ve linear bilginin transferi gerçekleşir ve uyanıklık durumudur. Burst mod
ise inhibituvardır ve non-linear bilginin transfer gerçekleşir, bu durum uyku ve epileptik dejarjlardaki durumdur.
TRN, talamus relay nöronlarını hangi fazda ateşleme yapacakları konusunda önemli görev alır.
Mesiotemporal lob epilepsi (MTLE) ya da limbik epilepsi ile talamus ilişkisi:
MTLE nöbetlerin temporal lob yapılarından başladığı gözlenmiştir. Ancak, yapılan çalışmalar nöbetlerin
başlaması, çoğalması ve yayılmasında amigdala, entorinal korteks, peririnal korteks, neokorteks ve talamus gibi
yapılarında önemli rol oynadığı gösterilmiştir.
MTLE nöbet döngüsünde özelikle orta hat (midline) talamik nukleuslarının görev aldığı gösterilmiştir. Bazı limbik
yapılar birbirleriyle aynı zamanda midline talamus ile resiprokal bağlantıdadırlar. Talamus, subkortikal yapıların
senkronizasyonunu yaparak nöbetlerin başlangış döngüsünde görev alır. Komşu neokortikal yapılara dağılımı ile
nöbet jeneralize olur.
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