Altklausuren Flashcards

Question

Onkolytische Viren in der anti-Tumor Therapie. Nennen sie die zwei grundlegenden Prinzipien

Answer 1

Das Prinzip der Virotherapie: Onkolytische Viren dringen über spezifische Rezeptoren in eine Tumorzelle ein, vermehren sich darin und zerstören sie innerhalb von Stunden oder Tagen. Dabei wird eine neue Generation von Viren frei, die andere Tumorzellen in der Nachbarschaft befällt. Erneut nutzen die therapeutischen Viren Tumorzellen als Basis für die eigene Replikation. Da aus jeder infizierten Zelle bis zu 10 000 neue Erreger entstehen, entwickelt sich ein tumorzerstörendes »Schneeballsystem«, bei dem immer schneller immer mehr Tumorzellen aufgelöst werden. Mithilfe der onkolytischen Viren wird der Tumor zu einer Art pharmazeutischer Produktionsstätte. Im Idealfall führt der virale Dominoeffekt dazu, dass eine einmalige Gabe (zwischen zehn Millionen und einer Milliarde Mikroorganismen) ausreicht, damit von einem hühnereigroßen Tumor binnen kurzer Zeit nur noch Zellmüll übrig bleibt, der von Makrophagen beseitigt werden kann. Onkolytische Viren machen also im Prinzip dasselbe wie Masern- und Mumpsviren sowie andere virale Erreger in gesunden Zellen, nur zielgerichteter und effektiver. Wenn keine neu zu infizierende Krebszelle mehr vorhanden ist, können keine Viren mehr gebildet werden und die Virusvermehrung kommt von alleine vollständig und dauerhaft zum Erliegen. Neben dieser „direkten“ Onkolyse gibt es den noch wichtigeren Prozess der „indirekten“ Virus-vermittelten Onkolyse: wenn eine Virus-infizierte Krebszelle zerplatzt, setzt sie quasi wie bei einer „stellaren Supernova“ auf einen Schlag massenhaft Virus- Antigene gemeinsam mit Tumorzell- spezifischen Antigenen frei. Bis dato war die Präsentation dieser Tumorzell- spezifischen Antigene für das Immun- system nicht ausreichend, um dagegen genügend aktiv zu werden. Nun aber wird in dem durch das Virus induzierte Entzündungsmilieu das Immunsystem so stark stimuliert, dass gleichzeitig – quasi im Huckepack – auch eine effek- tive antitumorale Immunantwort gegen Tumorzell-spezifische Antigene indu- ziert wird. Einmal ausreichend stimu- liert, erkennen unsere Immunzellen von da ab sämtliche Krebszellen als fremd und zwar unabhängig davon, ob sie Virus-infiziert sind oder nicht. Auf diese Weise kann nun jede einzelne Krebs- zelle überall im Körper der betroffenen Patienten durch unsere Immunzellen aufgespürt und vernichtet werden. So- mit stellt die Virotherapie eine beson- dere Form der Immuntherapie dar.

Answer 2

MCPyV ist eines von sieben beim Menschen bekannten Onkoviren. Es soll die Mehrzahl aller Fälle von Merkelzellkarzinomen verursachen, einer seltenen, aber aggressiven Hautkrebsform. Bei ca. 80 % der Merkelzellkarzinome (MCC) wurden Infektionen mit MCPyV gefunden. Antikörper gegen das MCPyV (die einen Kontakt mit dem Virus anzeigen) können bei gesunden Personen je nach Altersgruppe bei bis zu 80 % der Probanden nachgewiesen werden, wobei diese Seroprävalenz bei Kindern unter 15 Jahren bereits 50 % beträgt. Da es auch in Bronchialsekreten gefunden wurde, ist eine Übertragung über die Atemwege anzunehmen. Diese Isolate bei gesunden Virusträgern entsprechen dem nichtmutierten Wildtyp. Die meisten aus MCC-Tumoren isolierten Virusgenome unterliegen allerdings mindestens zwei Mutationen, die sie nichtübertragbar machen: Erstens ist das Virus klonal in das Wirtsgenom integriert, und zweitens ist das virale T-Antigen durch eine Mutation verkürzt, sodass es die zur Vermehrung des viralen Genoms notwendige zelluläre DNA-Replikation nicht mehr anstoßen kann. Dass MCPyV die Ursache der damit infizierten MCC-Tumoren ist, wurde in Studien durch Hemmung der Virus-Onkoproteine belegt. Wenn man diese Virusproteine unterdrückt, sterben die Zellen von MCPyV-positiven Merkelzellkarzinomen ab, im Gegensatz zu den Zellen aus Tumoren, die das Virus nicht tragen.[8] Die viruspositiven Tumorzellen sind also auf MCPyV angewiesen. Es bleibt völlig offen, warum 20 % der Merkelzellkarzinome virusnegativ sind. Man spekuliert unter anderem, beim Merkelzellkarzinom könnte es sich in Wirklichkeit um zwei oder mehr eng verwandte Krebsarten handeln, nur eine davon mit MCPyV-Infektion. Fehldiagnosen der schwierigen Krebsentität könnten für einige der negativen Resultate verantwortlich sein.

Answer 3

- components of ribonucleoprotein complexes - miRNAs bind to complementary target mRNAs in the 3' UTR Die Transkription von miRNAs ist zum Teil zelltyp- sowie gewebespezifisch und eng mit benachbarten Genen organisiert. Zellen geben einen Teil der intrazellulär gebildeten miRNAs in Form von extrazellulären Vesikeln (Mikrovesikeln, Exosomen) sowie an Proteinkomplexe (z. B. HDL) gebunden in ihre Umgebung ab. Dies ermöglicht die Detektion von miRNA im Blut und in anderen Körperflüssigkeiten.

Answer 4

Es gibt mehrere Apoptosesignalwege mit folgenden Signalschritten: Erstens einen Signalweg mit Todesrezeptoraktivierung, DISC-Bildung, Caspasenkaskade und Spaltung zellulärer Substrate (in Typ-I-Zellen) - Die Inhibition der Apoptose ist auf den mitochondrialen Weg der Apoptose beschränkt. Läuft die Apoptose allein über Aktivierung von Caspase-8 und Caspase-3 ab, so findet keine Inhibition statt. - BH3-Proteine sind an wahrscheinlich fast allen Fällen der Apoptoseinduktion beteiligt. Ein umfassender Abbau dieser Proteine erklärt den praktisch vollständigen Schutz infizierter Zellen gegen experimentelle Apoptoseinduktion. Runterregulieren der Rezeptoren der TNF-Rezeptorfamilie (z.B. CD95 oder TRAIL) wie beispielsweise TNF oder Zytokine, die von T-Lymphozyten abgesondert werden wie FADD (Fas-assoziierte Protein mit Todesdomäne) und Caspase 8. Oder mehr Kontakt zur extrazellulären Matrix.

Answer 5

Tumorstammzellen sollen durch Selektion über Chemoresistenz angereichert und über Fluoreszenzmarkierung von Kandidatenmarkern oder durch Verpaarung mit Mauslinien mit fluoreszierenden intestinalen Stammzellen markiert und mittels Durchflusssortierung isoliert werden. Mit Hilfe von Tumorstammzellmarkern isolierte Tumorzellpopulationen werden in vitro und in vivo auf Stammzellverhalten überprüft (sphere formation, Tumorbildung). Durch Transkriptomanalysen von Tumorstammzellen sollen Zielstrukturen und Signalwege identifiziert werden, die eine Tumorstammzell-wirksame therapeutische Intervention erlauben.

Answer 6

Mdm2 controls the p53 level through TAD occlusion and degradative ubiquitination. Mdm2: N-terminal region with p53 binding - nuclear export and import signals, nuclear-cytoplasmic shuttling - acidic, phosphorylation site, regulation of Mdm2 function - Zn finger - C-terminal region with RING, E3 ligase activity Control of p53 lvel through negative feedback loop: 1. Formation of p53 tetramers (active transcription factor) 2. Transactivation of various genes including the mdm2 gene 3. Production of Mdm2 protein 4. Mdm2 binds p53 in the nucleus (TAD occlusion, inactive p53) 5. Export to the cytoplasm and Mdm2-mediated ubiquitination of p53 6. p53 degradation No binding of Mdm2 (due to inhibition) leads to p53 stabilization and activation.

Answer 7

- das Phospholipid-bindende Protein Annexin V haftet an Phospholipid-Resten, die bei der Apoptose exponiert werden - in frühen Apoptosestadien verlieren apostolische Zellen ihre Phospholipidasymmetrie und exponieren PS auf die Außenseite ihrer Plasmamembran

Answer 8

- Caspase-activated DNase (CAD): spaltet an internukleosomalen gekennzeichneten Regionen (linker region) und produziert 180-185 bp Fragmente -> degradation of chromosomal (ds) DNA into nucleosomal and oligonucleosomal fragments (DNA laddering) -> Type I DNases TUNEL = "terminal desoxynucleotidyl transferase dUTP nick-end labeling" Im Rahmen der Apoptose findet die Fragmentierung der DNA durch die Caspasen-aktivierte DNase statt. Diese Endonuklease spaltet die freiliegende DNA zwischen den Nukleosomen. Somit entstehen in regelmäßigen Abständen (Vielfaches von 180–200 Basenpaaren) Einzelstrangbrüche. An diesen sogenannten nicked-ends befindet sich eine freie 3'-OH-Gruppe. An diesen Hydroxygruppen werden die Bruchstellen mittels Fluoreszenzfarbstoff- oder Enzym-konjugiertem Desoxyuridintriphosphat (dUTP) markiert. Die kovalente Bindung wird durch die terminale Desoxynucleotidyl-Transferase (TdT) katalysiert. Ein Nachweis der Bindung von dUTP an nicked-ends ist danach z.B. mittels Fluoreszenzmikroskopie möglich. Die markierten Zellen werden als TUNEL-positiv bezeichnet.

Answer 9

Normoxie: wird konstitutiv exprimiert -> Proline hydroxylation -> VHL conjugation -> ubiquitination -> targeting to proteasome -> proteasomal degradation Hypoxie: ubiquitously expressed -> gelangt in den Zellkern -> bindet HIF beta -> Erythropoesis/Metabolism/Angiogenese Chronische Entzündungen und Tumore beeinflussen ihre lokale Umgebung hinsichtlich der Expression von Transkriptionsfaktoren (insbesondere NF-kB) und Zytokinen, was letztlich zu einer verstärkten HIF-Expression führt. HIF selbst beeinflusst wiederum die Entzündung und den Tumor positiv, zum Beispiel durch eine verstärkte Angiogenese. Bei der Behandlung von Krebs und chronischen Entzündungen könnte die Blockade von HIF eine Therapieoption darstellen.

Answer 10

Routine evaluation of the HER2 status by FDA-approved assays -> immunohistochemistry and fluorescence in site hybridization (FISH) Lapatinib (Tyverb) -> small-molecule, reversible tyrosine kinase inhibitor - binds to the ATP-binding pocket of HER1 and HER2 - prevents phosphorylation of the kinase domain - prevents downstream tumorigenic signaling leading to cell cycle arrest and apoptosis Major side effect: affect liver function

Answer 11

- specific cells undergo apoptosis during the normal differentiation process - identified and characterized genes controlling cell death -> these products interact with each other and corresponding genes exist in humans 1) simple organism but many similarities with higher animals 2) shares many genes and molecular pathways with higher animals 3) easy to handle 4) transparent body (microscopy) 5) the development is invariant 6) constant number of cells (eutely) 7) the lineage of each cell is known 8) short life cycle (3 days) 9) short life span (2-3 weeks) 10) generation of homozygote progenies (hermaphrodite)

Answer 12

Protooncogenes: code for proteins that stimulate the cell cycle and promote cell growth and proliferation Tumor suppressor genes: code for proteins that repress cell cycle progression and promote apoptosis An important difference between oncogenes and tumor suppressor genes: - oncogenes result form the activation (turning on) of proto-oncogenes - tumor suppressor genes cause cancer when they are inactivated (turned off) Onkogene = wachstumsfördernden Einfluss und kontrollieren den Zellzyklus, Mutation von einem der beiden Allele ausreichend für Aktivierung als Onkogen Tumorsuppressormutation =im Normalzustand wachstumshemmenden Einfluss auf Zellen, Two-Hit-Hypothese -> beide Allele müssen mutiert sein

Answer 13

Granzyme A, a serine protease in the cytotoxic granules of natural killer cells and cytotoxic T lymphocytes, induces caspase-independent cell death when introduced into target cells by perforin. Granzyme A induces single-stranded DNA damage as well as rapid loss of cell membrane integrity and mitochondrial transmembrane potential through unknown mechanisms. Granzyme A destroys the nuclear envelope by targeting lamins and opens up DNA for degradation by targeting histones. A special target of the granzyme A cell death pathway is an endoplasmic reticulum-associated complex, called the SET complex, which contains three granzyme A substrates, the nucleosome assembly protein SET, the DNA bending protein HMG-2, and the base excision repair endonuclease Ape1. The SET complex also contains the tumor suppressor protein pp32 and the granzyme A-activated DNase NM23-H1, which is inhibited by SET. Granzyme A cleavage of SET releases the inhibition and unleashes NM23-H1. Cleavage of Ape1 by granzyme A interferes with the ability of the target cell to repair itself. The novel cell death pathway initiated by granzyme A provides a parallel pathway for apoptosis, important in destroying targets that overexpress bcl-2 or are otherwise invulnerable to the caspases.

Answer 14

- Rauchen - Solariennutzung - Asbestkontakt - ionisierende Strahlung (Röntgenaufnahmen)

Answer 15

a) 1) lack density-dependent inhibition of proliferation 2) reduced requirements for growth factors 3) less regulated cell-cell, cell-matrix (less adhesive) 4) not sensitive to contact inhibition 5), 6) secrete proteases for invasion, growth factors for angiogenesis 7) don't differentiate normally, stay undifferentiated 8), 9) not undergo apoptosis, even after DNA damage 10) unlimited DNA replication, (over) express telomerase b) Neoplasia = the growth of new tissue -> autonome, pathologische Gewebevermehrung

Answer 16

a) Parental inheritance (predisposition) 5-10 % Environmental factors 90-95 % b) Lifestyle choices (nutrition, tobacco usage, alcohol, obesity, physical activity), naturally occurring exposures (ultraviolet light), air pollution (car exhaust gases, industrial emission)

Answer 17

a) - widespread consensus that the vast majority of human tumors are monoclonal growths descended from single progenitor cells - cells in the tumor mass become heterogenous during tumor progression 1) genetic level (different mutations, epigenetic changes, chromosomal instability) 2) morphological level (e.g. cell size, nucleus size, marker proteins) 3) functional level (proliferation rate, tumorigenic potential)

Answer 18

Fraction with a small number of cells - behave like stem cells - self-renewal - unlimited proliferative potential - production of a large number of progeny which are in different state of differentiation (different surface markers) and with limited proliferative potential b) Stem cell niche -> tumor microenvironment

Answer 19

Genotoxic carcinogens: initiate tumor formation by DNA damage and mutagenesis (e.g. by DNA adduct formation) Non-genotoxic carcinogens: promote tumor formation by pathways other than DNA damage (e.g. cell proliferation, cytotoxicity, hormonal effects) -> lead to increase in cell proliferation (inhibition of apoptosis) - direct mitogens (mimic growth factors) - cytotoxic compound (regenerative cell proliferation) - hormone or hormone mimetics (high concentrations or with similar receptor affinity) - compounds affecting the immune system (pro- and anti-inflammatory factors) b) Berenblum fand heraus, dass die krebserzeugende Wirkung von Steinkohleteer auf der Haut von Mäusen wesentlich gesteigert wurde, wenn die Tiere nachfolgend mit Phorbolester behandelt wurden. Aus diesem Experiment leitete Berenblum ab, dass es Initiatoren geben müsse (heute würden wir sagen gentoxische oder primäre Kanzerogene) und Promotern (heute würden wir diese Gruppe als sekundäre Kanzerogene bezeichnen). Es gelang Berenbaum, an der Rückenhaut der Maus als Modell auf besonders elegante Weise, in einem einfachen Protokoll mit dem Reizstoff Crotonöl Kanzerogenese zu erzielen. Sie läuft in zwei operational definierten Stufen ab. Er nannte diese Stufen "Tumorinitiation" und "Tumorpromotion". Man spricht von Berenblum-Experiment auch als dem "initiations-/Promotions-Protokoll" (I/P-Protokoll) an der Mäusehaut, oder dem Zweistufenmodell der Kanzerogenese. Die beiden Stufen des Protokolls können oft sinngemäß durch eine dritte Stufe "Tumorprogression" ergänzt werden, so dass ein Dreistufenmodell für den Gesamtprozess der Kanzerogenese vorliegt. Mit Crotonöl war zum ersten Mal ein "tumorpromovierender" Krebsrisikofaktor entdeckt, den man sinngemäß auch als "Konditionalkanzerogen" bezeichnen kann.

Answer 20

- Micronucleus test - Chromosome aberrations - Comet assay

Answer 21

a) - can become an oncogene due to mutations or increased expression, a loss of regulation - Increased gene expression caused by: an increase of protein expression (through misregulation), an increase of protein (mRNA) stability, prolonging its existence and thus its activity in the cell, genome instability (gene duplication), resulting in an increased amount of protein in the cell - Chromosomal translocation: increase gene expression, formation of hybrid genes and fusion proteins e.g. Philadelphia chromosome -> chronic myeloid leukemia b) over expression leads to strong and constant proliferative signaling c) through FDA-approved assays d) Pitfalls: HER2 somatic mutations in HER2 gene amplification negative breast cancer

Answer 22

a) Tumor suppressor proteins: inhibit pathways stimulated by products of oncogenes, code for proteins that repress cell cycle progression and promote apoptosis, cause cancer when they are inactivated ("turned off") Proto-oncogenes: code for proteins that stimulate the cell cycle and promote cell growth and proliferation, have to be "turned-on" in order to become oncogenes b) 1. genetic mutation 2. viral inactivation 3. phosphorylation 4. degradation c) ist ein Cyclin-abhängiger Kinase-Inhibitor -> hemmt CDK4 und CDK6 und führt dazu zu einer verringerten Zellproliferation während des Übergangs von Phase G1 zu S des Zellzyklus -> nicht für Patienten mit HER2-Mutation geeignet

Answer 23

- Hypoxia inducible factor (HIF) transcription factor - dimeric transcription factor composed of an oxygen-dependent subunit (alpha) and an oxygen-independent subunit (beta) - 3 subtypes: HIF-1 -> ubiquitously expressed and best investigated 1. Proline Hydroxylation 2. VHL Conjugation 3. Ubiquitination 4. Targeting to Proteasome 5. Proteasomal Degradation 6. Peptides

Answer 24

a) cancer needs blood supply, "feed"tumor with nutrients and oxygen > tumor growth b) MMP17, MMP13

Answer 25

a) Cancer cells usually grow quickly, multiplying at a fast rate, which takes a lot of energy. This means they need lots of glucose. b) Glycolytic enzymes such as GLUT1, lactate dehydrogenase, pyruvate kinase and the lactate exporter

Answer 26

a) penetration (non enveloped viruses) or fusion with cellular membranes (enveloped viruses) -> food and water, skin lesions, dog biting , sexual contact b) - viral integration events in the germ line may contribute to shaping the host genome and may provide selective advantages for the host and by that contribute to species evolution - but may also lead to alteration of expression of pre-existing gene c) cervical cancer is highly correlated with chronic HPV infections -> cervical screening programs or widespread good quality cytology can reduce cervical cancer incidence and mortality (z.B. Pap test, HPV DNA testing) d) Hodgkin's lymphoma -> Epstein-Barr Virus (EBV) Hepatocellular carcinoma -> Hepatitis B virus (HBV) Merkel tumors -> Merkel cell polyomavirus (MCPV)

Answer 27

a) Ionizing radiation carries sufficient energy to detach electrons from atoms or molecules, thereby ionizing them by that damaging the DNA of cells leading to cellular death - radiation hits water molecules and other organic molecules in the cell -> production of free radicals like hydroxyl (HO) and superoxide (O2-) - short lived and rapidly interact with biomolecules - most important ROS are generated in 2 nm distance from DNA b) - Alkylating agents -> G1 phase - Antimetabolites -> S phase - Topoisomerase inhibitors -> S phase - Antimicrotubule agents -> M phase

Answer 28

a) Imatinib ist ein Tyrosinkinase-Inhibitor und wirkt somit der self suffinecy in growth signals entgegen b) Telomerase inhibitors c) Inhibition of poly(ADP-ribose) polymerase (PARP) activity induces synthetic lethality in mutated BRCA1/2 cancers by selectively targeting tumor cells that fail to repair DNA double strand breaks (DSBs). d) As part of its normal function, the immune system detects and destroys abnormal cells and most likely prevents or curbs the growth of many cancers. For instance, immune cells are sometimes found in and around tumors. These cells, called tumor-infiltrating lymphocytes or TILs, are a sign that the immune system is responding to the tumor. People whose tumors contain TILs often do better than people whose tumors don’t contain them. Even though the immune system can prevent or slow cancer growth, cancer cells have ways to avoid destruction by the immune system. For example, cancer cells may: Have genetic changes that make them less visible to the immune system. Have proteins on their surface that turn off immune cells. Change the normal cells around the tumor so they interfere with how the immune system responds to the cancer cells. Immunotherapy helps the immune system to better act against cancer.

Answer 29

a) Biomarkers are measured as an indicator of normal biological processes, pathogenic processes or responses to an exposure or intervention, including therapeutic interventions. b) Prognostic, diagnostic, predictive, Pharmacodynamics, recurrence

Answer 30

LOADING OF THE MIRNA DUPLEX - composed of one of the four human Argonauten proteins (AGO1-4), Dicer, and a dsRNA binding protein (e.g. TRBP, or PACT) - loading of miRNA duplex onto Argonauten SELECTION of the mature miRNA strand - pre-RISC consist of a Argonaute and a miRNA duplex - removal of the passenger strand leads to the formation of an activated RISC - the active RISC (miRISC) contains a single stranded miRNA (guide strand) which directs the complex to the target mRNA for post transcriptional gene silencing

Answer 31

Chronic myeloid leukemia - chromosomal translocation -> increased gene expression -> formation of hybrid genes and fusion proteins e.g. Philadelphia chromosome

Answer 32

- encode viral structural components - encodes regulators of viral replication - viral evasion of immunosurveillance - regulator of viral transcription - manipulation of various cellular processes

Answer 33

- Human papilloma virus - Eppstein-Barr Virus - Human T-lymphotropic virus - Kaposi's sarcoma-associated herpes virus - Merkel cell Polyoma virus - Hepatitis B virus - Hepatitis C virus

Answer 34

- not cause human cancer, important model - small genome sizes - replicates in permissive host - transforms non-permissive host (inactivates Rb) Early region encodes proteins (small and large T antigens) Proteins stimulate host cell gene expression, DNA synthesis

Answer 35

Degradation of chromosomal (ds) DNA into nucleosomal and oligonucleosomal fragements -> DNA fragmentation

Answer 36

N-terminus: Prodomain - cleavage site - large subunit with catalytic cysteine - cleavage site - small subunit - C-terminus Unter Procaspasen versteht man inaktive Vorstufen von Caspasen. Sie bestehen aus einer N-terminalen Prodomäne, einer p10- sowie einer p20-Domäne. Aktivierte Caspasen können hydrolytisch hinter Asparaginsäure Aminosäureketten spalten Caspasen werden durch proteolytische Spaltung zwischen der p10-Domäne und der p20-Domäne aktiviert. In dieser Form bilden Caspasen ein Heterotetramer aus zwei p10/p20-Heterodimeren.

Answer 37

Drosha-dependent Transcription of intergenic and intronic miRNA genes: - Long pro-mRNA with 5' cap and poly(A) Processing of pro-mRNAs into pre-miRNAs: Microprocessor: nuclear heterotrimeric protein complex consisting of: - Drosha a Range III endonuclease - Two DGCR8 (dsRNA-binding protein) Export: - The Exportin-5/Ran-GTP complex recognizes the RNA stem together with the short 2 nucleotides 3' overhang of the pre-miRNA - Transportation of the pre-miRNA from the nucleus to the cytoplasm

Answer 38

- first tumor suppressor gene found was retinoblastoma, inherited childhood eye tumor - about 50% of children of affected parent develop retinoblastoma: inherited as dominant autosomal susceptibility to tumor development - need somatic mutation of other copy Retinoblastoma requires loss of both functional copies of tumor susceptibility gene (Rb gene); - people inherit one mutated gene, later other mutates Noninherited retinoblastoma is very rare: needs two independent somatic mutations in cell

Answer 39

- recombinant, humanized monoclonal antibody directed against the extracellular domain of the HER2 protein - activation of an immune response (ADCC (antibody -dependent cell-mediated cytotoxicity) by NK cells) other possible mechanisms of action - increasing the rate of degradation of HER2 - prevents downstream tumorigenic signaling leading to cell cycle arrest and apoptosis Major side effect: cardiac dysregulation

Answer 40

APC IS A TUMOR SUPPRESSOR PROTEIN 1. Inactivating mutations in hereditary and sporadic colon cancers 2. Multiple biological (normal) roles: proliferation, differentiation, apoptosis, adhesion, cell migration, development APC IS A GATEKEEPER PROTEIN 1. Loss of APC function leads to the appearance of unregulated dividing cells 2. Transition from normal epithelial cells to hyperplastic cells Binding of beta-catenin promotes beta-catenin degradation APC is component of Wnt/Frizzled signaling pw -> is critical for the regulation of crypt stem cell renewal and tissue homeostasis

Answer 41

APC IS A TUMOR SUPPRESSOR PROTEIN 1. Inactivating mutations in hereditary and sporadic colon cancers 2. Multiple biological (normal) roles: proliferation, differentiation, apoptosis, adhesion, cell migration, development APC IS A GATEKEEPER PROTEIN 1. Loss of APC function leads to the appearance of unregulated dividing cells 2. Transition from normal epithelial cells to hyperplastic cells Binding of beta-catenin promotes beta-catenin degradation APC is component of Wnt/Frizzled signaling pw -> is critical for the regulation of crypt stem cell renewal and tissue homeostasis

Answer 42

1. The general apoptosis machinery consist of an activator (CED-4) and a protease (CED-3) (recruitment and auto activation) 2. In healthy cells, the inhibitor CED-9 blocks the function of the activator CED-4 3. In dying cells, EGL-1 binds to and inhibits CED-9 activity 4. The activity of EGL-1 is regulated at the transcriptional level. Depending on the cell type, transcription factors can be activators or repressors

Answer 43

- self-renewing - long-lived - high potency - low division rate - asymmetric division - very rare

Answer 44

EGL-1 - Inhibitor - pro-apoptotic (BH3-only) - binding and inhibition of CED-9 - release of CED-4 CED-9 - Inhibitor - anti-apoptotic (BH1-4 domain) - binding and inhibition of CED-4 CED-4 - activator (Apaf-1 like) - oligomerization, binding and activation of CED-3 proenzyme CED-3 - protease (Caspase) - substrate cleavage and death

Answer 45

Pro-apoptotic proteins of the BCL-2 family - inhibiting Anti-apoptotic proteins of the BCL-2 family - inhibiting Activator Apaf-1 - activating Proteases Caspases - substrate cleavage and cell death

Answer 46

Papillome sind gutartige Wucherungen von Hautzellen, welche manchmal durch Viren verursacht werden. Sie treten einzeln oder auch nebeneinander auf, können eine breite Basis aufweisen und flach an der Haut liegen, oder auf einer dünnen Basis langgestreckt imponieren. - Small DNA containing virus with a circular double-stranded genome (8 kb). - HPV have been isolated from many species including humans - Infect epithelial cells and cause the formation of benign epithelial lesions including squamous warts.

Answer 47

- is a Topoisomerase II inhibitor - form a ternary complex with DNA and tops enzyme by forming hydrogen bonds - prevent DNA re-ligation and therefore causes DNA damage resulting in apoptosis - cancer cells rely on too enzymes more than healthy cells -> rapid replication

Answer 48

- Traditionally, treatment strategies have been decided by where cancers arise in the body and how tumors look under the microscope - cancers developing in the same part of the body can vary greatly in their genetic make up - but also: cancers developing in different parts of the body can share a similar genetic make up (e.g. vemurafenib (Zelboraf) is effective in melanomas with specific mutation in BRAF gene; hairy-cell leukemia and some forms of thyroid cancer) How to choose a drug in personalized medicine: Circulating tumor cells, mouse avatar, 3D cell culture

Answer 49

1) Survival despite of DNA damages & cell-cycle dysregulation 2) Survival despite several stresses (e.g. limitations of oxygens, growth factors, and nutrients) 3) Survival despite immune response (e.g. CTL attack) 4) Survival despite absence of tissue anchorage 5) Survival despite lack of the right growth factors 6) Resistance to chemotherapy & radiotherapy

Answer 50

-> is a specialized microenvironment that protects stem cells and regulates their behavior The stem cell niche can act on a stem cell by various mechanisms: - Direct contact between the stem cell and the niche cells - Releasing of soluble factors by the niche - Intermediate cells "communicate" between the niche and the stem cell

Answer 51

Fraction with a small number of cells - behave like stem cells - self-renewal - unlimited proliferative potential - production of a large number of progeny which are in different state of differentiation (different surface markers) and with limited proliferative potential

Answer 52

- p53 normally functions as a heterotetrameric transcription factor - missense mutation in the DNA binding domain results in the expression of altered proteins which can form tetramers but cannot bind to DNA - all tetramers with one or ore mutant p53 subunits are defective in their function as transcription factor and are more stable than wild type p53

Answer 53

- provide direct access to blood vessels (e.g. by a central venous catheter) - place a special pump that is used to deliver chemotherapy drugs CURATIVE CHEMOTHERAPY: aims to eliminaste all cancer cells from the body to achieve a permanent cure PALLIATIVE CHEMOTHERAPY: to relieve certain symptoms, to slow down the progress of the disease or to stop it temporarily NEOADJUVANT CHEMOTHERAPY: is done before surgery to shrink the tumor size and to allow less invasive surgery ADJUVANT CHEMOTHERPAY: aims at cancer cells that might be left in the body after surgery and is performed to prevent recurrences - Alkylating agents: Cisplatin - Antimetabolites: Hypoxanthine - Topoisomerase inhibitors: Etoposide

Answer 54

Pro-apoptotic BH1-3 multidomain proteins - high concentration -> induction of apoptosis, but only after their activation BH-3 only proteins - interaction with anti-apoptotic BH1-4 multi domain proteins (e.g. BCL-1) -> inhibition or induction of apoptosis - binding to and activation of pro-apoptotic BH1-3 multi domain proteins (e.g. BAX, BAK) -> induction of apoptosis

Answer 55

- Helicard - Caspase-activated DNase (CAD)

Answer 56

- Transactivation - Nuclear export signals - Proline rich - Sequence-specific DNA binding - Nuclear-localization signals - Oligomerization -> Die meisten Mutationen in der Sequence-specific DNA Binding region

Answer 57

- uncontrolled proliferation - inhibition of differentiation

Answer 58

- wird unter Normoxia inhibiert 1) Proline Hydroxylation 2) VHL Conjugation 3) Ubiquitination 4) Targeting to Proteasome 5) Proteasomal Degradation

Answer 59

Mdm2 controls the p53 level through TAD occlusion and degradative ubiquitination.

Answer 60

NORMAL CELL - Cell proliferation: Controlled - Number of cell divisions: Limited, ca 50 cycles (Hayflick limit), mortal - Contact inhibition: Yes, monolayer culture - Dependent on growth factors: Yes - Tumor formation: No TRANSFORMED CELL - Cell proliferation: Uncontrolled - Number of cell divisions: Unlimited (Immortal) - Contact inhibition: No, multilayer culture - Dependent on growth factors: No - Tumor Formation: Yes, tumorigenic in laboratory animals

Answer 61

inhibits microtubule assembly -> no M phase

Answer 62

DNA damage -> activation -> CEP-1 (Transcriptional activator) -> EGL-1 (pro-apoptotic protein (BH3-only) -> Initiation of Apoptosis

Answer 63

- EMT program is a spectrum of transitional stages between the epithelial and mesenchymal phenotypes - In context of metastasis: -> Epithelial cell marker: E-cadherin, cytokeratin -> Mesenchymal cell marker: N-cadherin, vimentin - Signaling pathways induce EMT-transcription factors (EMT-TFs) such as Twist E-cadherins are transmembrane proteins and are important for the formation of adherents junctions

Answer 64

- Formation of the octameric CED-4 complex - Recruiting of two monomeric CED-3 zymogens - Binding in the hutch of the funnel-like CED-4 apoptosome - Close proximity results in -> dimerization of CED-3 proenzymes -> autoproteolytic activation of CED-3 -> formation of an active CED-3 enzyme (tetramer) - the activated CED-3 enzyme remains bound to the apoptosome to form the active holoenzyme

Answer 65

1. Heterodimerization of anti- and pro-multi domain proteins - BCL-2, BCL-XL with BAX - MCL-1, BCL-XL with BAK 2. Sequestering of BH3. only activators (BID, BIM) by anti-apoptotic proteins (BCL-2, BCL-XL) (no activation of pro-apoptotic BH1-3 proteins)

Answer 66

TNM STAGING SYSTEM (TUMOR, NODES, METASTASES) - Description of the size of the primary tumor and extension of spreading (tissue infiltration) - involvement of lymph nodes - spreading to distant organs (metastasis) GRADING - determination of cell anaplasia (loss of differentiation) in tumor tissue in comparison to the normal tissue - degree of tumor aggressiveness - pathology: variability in size, shape and staining of cells and their nuclei - nucleus upregulated to cytoplasm down regulated ratio - mitotic activity upregulated - atypical mitoses upregulated Aims: help to plan treatment and give an indication of prognosis

Answer 67

TNM STAGING SYSTEM (TUMOR, NODES, METASTASES) - Description of the size of the primary tumor and extension of spreading (tissue infiltration) - involvement of lymph nodes - spreading to distant organs (metastasis) GRADING - determination of cell anaplasia (loss of differentiation) in tumor tissue in comparison to the normal tissue - degree of tumor aggressiveness - pathology: variability in size, shape and staining of cells and their nuclei - nucleus upregulated to cytoplasm down regulated ratio - mitotic activity upregulated - atypical mitoses upregulated Aims: help to plan treatment and give an indication of prognosis

Answer 68

Loss of Heterozygosity

Answer 69

- Transactivation domains (TAD1 and TAD2): Transcriptional activation of p53 target genes - Proline rich domain (PRD): Structural function and protein-protein interaction - DNA-binding domain: Sequence-specific binding to p53 response elements in the promoter regions - Tetreamerization domain (Tet): p53 binds to its DNA response elements as tetramer -> Note: only the p53 tetramer can efficiently bind to the DNA helix - Lysine rich domain (Basic) (regulator domain): Non-sequence-specific DNA binding (modulates the sequence-specific binding) a) Mdm2 bindet an TAD1 b) Mdm2 controls the p53 level through TAD occlusion and degradative ubiquitination

Answer 70

a) Frameshift and nonsense mutations -> Germline and somatic mutations b) Formation of truncated APC proteins, loss of beta-catenin binding site, uncontrolled proliferation c) + d) 1. Loss of the beta-catenin binding domain: Activation of beta-catenin/TCF transcription -> activation of proliferation and inhibition of differentiation 2. Loss of the microtubule binding domain -> induction of spindle dysfunctions -> induction of chromosomal instability

Answer 71

1. Two nucleotides 3' overhang 2. The 5' phosphate ends and 3' hydroxyl ends are characteristic RNase III cleavage products -> RNase III endonuclease

Answer 72

Functional studies: Altering endogenous level of miRNAs in cells 1) Transfection of synthetic Dicer substrate dsRNA (27-30 nts) which enter the pathway of endogenous miRNAs and increase their activity -> Gain of miRNA function 2) Transfection of synthetic antisense oligonucleotides which reduce the endogenous miRNA activity -> Loss of miRNA function

Answer 73

- introduce an additional skipping - Reading Frame restored - shortened but functional dystrophin produced

Answer 74

The Wnt signaling pathway is critical for the regulation of crypt stem cell renewal and tissue homeostasis Deregulated apoptosis: 1. Too little cell death: Autoimmune diseases, cancers 2. Too much cell death: Neurodegenerative diseases, AIDS

Answer 75

- X-linked marker - some human females are heterozygous for G6PD (mosaic) - the two allelic forms of G6PD show different heat sensitivity Dark spots: heat-resistant isoform, active enzyme Light grey spots: heat-sensitive isoform, inactive enzyme - The two allelic isoforms of G6PD differ in their gel electrophoretic mobility -> the tumor cells originate from a single cell (monoclonal)

Answer 76

Driver mutation: - causally implicated in oncogenesis - confer growth advantage on the cancer cells Passenger mutations: - without functional consequences for oncogenesis - no growth advantage on the cancer cell

Answer 77

1. Isolation of cancer cells from fresh human biopsy samples 2. Optimize dissociation to preserve cell viability and marker integrity 3. Staining with fluorophore-conjugated antibodies against surface protein markers 4. Cell sorting by FACS into small and large cell pool 5. Injection in mice -> Tumors arose from the injected minority cells are also composed of the minority and majority cell population! ASSESSMENT OF TUMORIGENICITY 1. In vivo: Xenotransplantation (immunocompromised mice) 2. In vitro: 3D culture assay

Answer 78

miRNA = microRNA - ss non coding RNA - silences transcription of certain genes - RNA interferiere - post transcriptional gene silencing - part of RISC complex - partial complementary to target mRNA siRNA = small interfering RNA - short ds RNA - regulation of gene expression - can transiently silence genes - part of RISC complex - full complementary to target mRNA

Answer 79

- is an Chemotherapy - Antimetabolite - interferes with normal cellular metabolism of nucleic acids - MoA: disrupts DNA/RNA metabolism/production; S-phase of cell cycle

Answer 80

Beim intrinsischen Signalweg der Apoptose kommt es zur Freisetzung von Cytochrom c aus den Mitochondrien, welches daraufhin zusammen mit dATP an Apaf-1 bindet und dieses aktiviert. Es kommt zu einer Oligomerisierung von Apaf-1 zu einem radförmigen Heptamer, dem sogenannten Apoptosom.

Answer 81

Indirect activation of pro-apoptotic BH1-3 proteins - Binding of BH3-only sensitizers (BAD, BMF) to anti-apoptotic BH1-4 proteins (BCL2, BLC-XL) displaces the bound BH3- only activators (BID, BIM) - The released activators bind transiently to pro-apoptotic multi domain proteins -> activation and homooligomerization of BAX, BAK - binding of BH3-only proteins to anti-apoptotic BH1-4 proteins (BCL2, BLC-XL) displace bound pro-apoptotic BH1-3 proteins which can be activated by BH3-only activators and inhibit anti-apoptotic BH1-4 proteins

Answer 82

= Cysteine Aspartate-specific Proteases (cysteine aspartases) Activated initiator caspase -> Effector caspases are proteolytically activated through initiator caspases -> different caspases are capable to activate each other (positive feedback) - Caspases are cysteine proteases that cleave their substrates after aspartate residues - cleavage specificity is determined by a recognition motif consisting of 4 amino acid residues - caspases are synthesized as inactive proenzymes which are composed of a prodomain and a large and small subunits - effector caspases are cleaved and activated by initiator caspases - active caspases are tetramers formed from two heterodimers All caspases have a pro domain - large subunit - small subunit -> initiator caspase: long prodomain -> effector caspase: short prodomain -> cytokine maturation: inflammasome