Cancer Bio Exam 1
What are some ways in which RTKs can become oncogenes, and how do these changes make the resulting proteins oncogenic?
1. altered EGF receptor- make proteins oncogenic by the V-ErbB oncogene which is an EGF receptor without the ectodomain, allows for constitutive signaling 2. site specific mutation, truncation, or overexpression- mutations affecting structure cause ligand independent firing, overexpression causes frequent collision and spontaneous dimerization, both of these make receptor constitutively active which leads to oncogenesis
How does Wnt signaling contribute to cell proliferation? How does protein degradation vs. protein stability play a role in this pathway, and which protein is affected by this? Which component of the Wnt pathway is frequently mutated in colon cancer?
1. through beta catenin' s role as a transcription factor 2. without wnt signal, beta catenin degraded via APC containing degradation complex, TCF/Lef still intact. With Wnt signal, degradation complex inactivated, beta catenin goes to nucleus, activating Tcf/Lef through binding and displacing groucho repressor. Activates transcription protein stability/degradation affects whether transcription of proliferation genes is activated, beta catenin is affected because cannot go to nucleus without wnt activation 3. APC, resulting in high levels of beta catenin
How can miRNA's regulate gene expression?
1. transcription gives pre-miRNA as hairpin 2. drosha enzyme cuts each hairpin from mrna transcript 3. dicer enzyme turns the loop and single stranded ends from the hairpin and cuts 4. one strand of dsRNA is degraded, the miRNA strand forms a complex with other proteins (RISC) 5. the mirna in the complex can bind to any mRNA with at least 7 bases of the complementary sequence 6. if the mrna and mirna bases are complementary all along their length, the mrna is degraded, and if the match is less complete translation is blocked
What is alternative splicing? is it altered in cancer cells?
Alternative splicing is the ability of some genes to use various combinations of genes to create multiple proteins from one hnRNA transcript. This increase protein diversity and allows a species to maximize the number of proteins it can create from a limited number of genes. alternative splicing factors often upregulated in cancer cells, leading to alternative splicing and cellular transformation
JAK-STAT pathway
Cytokine signaling in hematopoietic system Example: Interferon signaling •Signal: IFN •Receptor: IFN-R •Jaks: Tyk2, Jak1, others •STATs: STAT1, STAT2, STAT3, others STAT3 constitutively active in many melanomas, breast cancers, head & neck cancers, lung cancers and gastric cancers
What does "BCR" stand for in the BCR-ABL fusion gene? What happens to the function of the kinase in the fusion protein?
BCR stands for breakpoint cluster region, the bcr-abl fusion creates a tyrosine kinase that is always on
Formation of the bcr-abl oncogene
Bcr: •Breakpoint Cluster Region•Normal BCR gene function is not clear. The protein has serine/threonine kinase activity .Abl: •Abelson murine leukemia viral oncogene•Normal Abl function: tyrosine kinase that responds to cytokines to proliferate .Bcr-Abl fusion: creates a tyrosine kinase that is always "on".
Diverse structural changes in proteins can lead to oncogene activation, including truncations
Example: epidermal growth factor receptor •Normally requires ligand binding to trigger growth •Oncogenic form: extracellular domain is lopped off, causing continual growth signal
How does gene fusion between Ros and Fig generate an oncogene?
Fig brings the Ros monomers together, this does not require a growth factor and allows constitutive activation
Focal adhesions are integrin-containing, multi-protein structures that form mechanical links between the cytoskeleton and the ECM
Focal adhesions are large, dynamic protein complexes through which the cytoskeleton of a cell connects to the ECM. •Contain integrins•Help to anchor the cell to the ECM•In motile cells, they are constantly assembled and disassembled •They also disassemble during the cell cycle Focal adhesions are integrin-containing, multi-protein structures that form mechanical links between the cytoskeleton and the ECM Actin fibers (green: -actin) Focal adhesions (orange: -vinculin
How do HMGA2 gene fusions sometimes alter gene expression?
Fusion gene regulation:•HMGA2 mRNA has a 3' UTR that is regulated by Let-7 miRNA •Various fusions with HMGA2 remove the 3'UTR, thus stabilizing the mRNA •More HMGA2 protein is then created HMGA2: •A non-histone chromosomal high-mobility group protein •Functions as architectural factors and are essential components of enhanceosomes
Overall, what is one of the most important signaling pathways that drives cancer when it is aberrantly activated? What is the component of this pathway that is most frequently activated by mutation into an oncogene?
GF-RTK-Ras-Raf-Mek-Erk, Ras is frequently activated by mutation into oncogene
Why do HER2/NEU and MYC generally become oncogenic via amplification instead of point mutation?
HER2/NEU and MYC are oncogenes, which are involved in cell growth and proliferation. Hence mere gene amplification of these genes are enough to cause uncontrolled cell proliferation. If they have a point mutation which mostly leads to loss of function then these genes will be silenced and the cells will no longer divide properly. In other words tumor suppressors should be switched off while oncogenes should be switched on to cause cancer. Amplification of tumor suppressors will result in growth arrest while amplification of oncogenes will result in tumor.
Describe the activation process of the NF-kB pathway, including IKK, IB and coactivators in your answer.
IKK complex phosphorylates IkB, IkB sequesters NF-kB in cytosol, at signal, IkB phosphorylated and degraded, NLS of NF-kB exposed, goes to nucleus and induces approx 5000 genes by binding to coactivator protein, constitutively active in many cancers involves negative feedback from IkB, can participate in enhanceosome formation
What would you expect to happen in cells with an aberrantly activated NF-kB pathway in which you've introduced an IkB with serine to alanine mutations within the degradation motif?
IKK recognizes motif and phosphorylates serines, phosphorylated IkB recognized by E3 ubiquitin ligases, ubiquitylated and targeted for proteasome degradation
IkBa super-repressor
IkBalpha "super-repressor" - serines mutated to alanines. Can no longer be degraded to allow NF-kB activation.Tested as an anti-cancer strategy for those cancers driven by activated NF-kB
In the Hedgehog pathway, what is the ligand, and what is the receptor? What does activation of the receptor do to transmit the signal? What is Gli and what happens to Gli in this pathway?
Ligand= hedgehog Receptor= patched The hedgehog (Hh) cell signaling pathway promotes cell growth and differentiation during embryonic development. Hh signaling is frequently aberrantly activated in cancer. The Hh signaling pathway may be activated by hedgehog ligands (sonic, desert, indian) binding to PTCH1 on the cell surface. In the absence of a hedgehog ligand, the Hh pathway is inhibited by PTCH1. PTCH1 inhibits the activation of SMO by maintaining SMO inside a vesicle within the cell. The binding of hedgehog ligands (sonic, desert, and indian) bind to PTCH1 releases PTCH1 from SMO and causes PTCH1 to be internalized and degraded. SMO migrates to the cell surface and initiates hedgehog signaling. The activation of SMO causes gene transcription and promotes normal embryonic development as well as cell growth and survival. Gli: a highly expressed protein in glioblastomas .•Up to 50% of sporadic basal cell carcinomas of the skin have oncogenic Smoothened or inactivated Patched alleles. (These cancers are usually benign.) •Inactivated Patched also found in medulloblastomas, meningiomas, and breast and esophageal carcinomas. gli is cleaved when hedgehog ligand not present and used as transcription co-activator when hedgehog ligand is present
What are 3 important signaling molecules that bind to activated Ras, and how do these signaling pathways lead to cancer?
PI3K, Raf, Ral-Gef The Raf (MAPKKK) pathway activates the MAP kinase cascade when Ras binds to GTP Raf (KKK)-MEK(KK)-Erk (K) leads to cancer by allowing genomic remodeling, protein synthesis, and gene transcription The MAP cascade also leads to phosphorylation of protein X and Y which change protein activity, and regulatory protein A and B which allow changes in gene expression The PI3K pathway activates PIP3 and AKT when Ras is activated, this turns on a bunch of downstream proteins which promote growth and block death AKT is activated through phosphorylation by PDK1 and mTOR Ral-GEF activates Ral A and Ral B which eventually activate Cdc42 which activates the filopodia for exploration and Rac which activates the lamellipodia for movement
What are some basic differences between Notch signaling vs. RTK signaling if you were to compare and contrast them?
RTK Ligand: GF Receptor: RTK Factor proteolyzed: NF1 needs ligand to activate activates Ras Notch Ligand: Delta Receptor: Notch most direct signaling to nucleus via cell cell contact receptor cleaved multiple times Factor proteolyzed: Notch receptor can't be used again activates transcriptional repressor Rbpsuh
The TGFb pathway halts cell growth in normal cells but promotes it in late stages of cancer
TGFb binds Type I and Type II receptor dimers •Smad 2 and/or Smad 3 is then phosphorylated •Trimeric complexes (Smad 2/2/4, 2/3/4 or 3/3/4) bind DNA weakly and association with neighboring factors to induce or repress gene transcription •Plays a role in many if not all carcinomas •Early stages of cancer: pathway prevents cell proliferation •Later stages: contributes to invasion
inducers of NF-kB pathway
TNF-alpha-produced by macrophages, induces local inflammation IL1-produced by macrophages, monocytes, fibroblasts, dendritic cells, induces inflammatory response
Can other signaling pathways contribute to integrin signaling? Describe.
Various signaling pathways can influence talin conformation, promoting interaction with integrins such as RTKs and GPCRs
What is one type of evidence that suggests that cancer is of monoclonal origin?
X-chromosome inactivation, only one x chromosome inactivated during development, and this inactivation retained in future generations
what is a karyotype, and what is the difference between euploidy and aneuploidy
a karyotype is the number and appearance of chromosomes in the nucleus euploidy is the presence of the normal number of chromosomes, 23 sets or 46 total aneuploidy is the presence of an abnormal number of chromosomes
What is the difference between a proto-oncogene and an oncogene, and what are some alternative methods by which proto-oncogenes can be converted into oncogenes?
a proto-oncogene is a normal gene, and an oncogene is a mutated, cancer causing gene. proto-oncogenes can be converted to oncogenes by a deletion or point mutation in the coding sequence, a regulatory mutation, gene amplification, and chromosome rearrangement
What are the two most common types of carcinoma and what is the difference between them?
adenocarcinoma- derived from epithelial cells that secrete into ducts squamous cell carcinoma- derived from epithelial cells that form protective layer
regulation of gene expression
approx 7% of genes in genome are transcription factors transcription factors, with dna bending proteins and activators help to recruit rna pol II to promoters tf's can be expressed in a tissue specific fashion, and thus different cell types express different proteins
What are two alternative roles that beta-catenin has in the cell?
b-catenin also helps connect cadherins to actin filaments inside the cell, connecting cytoskeletal networks across cells through adherens junction •Adherens junctions ensure structural integrity of epithelial sheets and block metastasis b-catenin is mostly localized to adherens junctions in epithelial cells, where it maintains cell-cell contacts •In some cancers that have lost E-cadherin expression, more nuclear b-catenin is observed leading to transcription of genes involved in cell proliferation
in addition to individual mutations that can be found by sequencing, cancer cells also show chromosome structure alterations visualized by microscopy
banding patterns of chromosomes first discovered on drosophila polytene chromosomes, condensed regions are dark
Why do fibroblasts derived from PDGF-R null mice not heal wounds in response to the addition of PDGF?
because PDGF needs to bind to the PDGF-R to activate and start wound healing
Why do so many leukemias have translocations?
because enzymes responsible for rearranging antibody gene sequences during development of immune system sometimes target non-specific sequences
Why do some tumors favor specific types of oncogenic Ras (H, K, and/or N)?
because their regulatory sequences show tissue specific expression
what is the difference in benign vs malignant tumors?
benign- local, not metastasized malignant- metastasized, spread to other tissues
How are RTKs generally activated?
by forming dimers and transphosphorylating each other, phosphorylate on tyrosines, form homodimers meaning two of the same receptor come together
How do RTKs signal to Ras?
by phosphorylating the SH2 domain of the adaptor protein Grb2, whose SH3 domain activates Ras-GEF, and then Ras-GEF activates Ras by exchanging GTP for GDP
Cancer Classification
carcinoma (80%)- epithelial cells sarcoma (1%)- connective tissue or muscle cells leukemias/lymphoma (7%)- hematopoietic cells nervous system (1.3%)- CNS cells other (10.7%)- various
What is the most common basic cancer classification group and why?
carcinoma, cancer of epithelial cells, because there are epithelial cells lining every organ
HSR's can occur upon amplification of transcriptionally active gene locus
caused by amplification of gene locus, if transcriptionally active, causes large white stretch in banding pattern, can be the result of double minute amplification
NF-kB functions
cell survival, cell cycle control, proliferation, invasion, metastasis/angiogenesis, EMT
What is the Philadelphia chromosome? How could one visualize whether a CML patient has this translocation?
chromosome translocation that occurs in leukemia cells of most CML patients, creates Bcr-Abl fusion protein that stimulates aberrant cell growth create karyotype and observe for translocation between chromosome 9 and 22
when using a fluorescent probe on a chromosome to find the location of a gene at metaphase, why does the probe usually hybridize in four locations?
chromosomes duplicate in metaphase
notch activation by proteolytic cleavage
cleavage 1- in golgi, forms heterodimer, transported to cell surface cleavage 2- extracellular, triggered by delta binding which exposes cleavage site ,to extracellular protease cleavage 3- intramembrane, mediated by gamma secretase complex
What are integrin receptors composed of, and what do they bind to? What is the functional role of integrin receptors?
composed of ECM protein, active integrin, alpha and beta subunit, (vinculin, talin, tensin = adhesion complex) and actin filament bind to the ECM protein and sense association between cell and ECM
Describe the structure and function of integrin receptors.
composed of large family of alpha and beta subunits 18 a, 8 b, and 24 heterodimer combinations receptor ectodomains bind specific ECM components, cations modulate binding, cytoplasmic domain of beta subunit linked by adapters to actin fibers, cytoplasmic domain connects to other signaling proteins upon activation tether ECM to cytoskeleton, bind to components of basal lamina outside cell, allow cell migration across ECM by rapid structural changes at both ends coupled together, important for wound healing, development, and metastasis
cancer develops progressively
continuum from normal to malignant, moves towards more and more aggressiveness and invasiveness
describe the components of the nucleosome
core contains histones H2A, H2B, H3, and H4 (in doubles) with H1 on outside the histone tails project out from the core and are highly modified by PTM's (methylation, phosphorylation, acetylation, ubiquitylation)
What two types of signals must normal epithelial cells respond to in order to grow and survive?
detect adequate growth factor levels and anchoring to ECM
gene expression inhibited by dna methylation
dna can be methylated on CpG (cytidine-guanosine) dinucleotides, methylation maintained at transcription by dna maintenance methyltransferase, turns transcription off
What are two of the biggest lifestyle changes one could make to try to avoid cancer?
don't smoke, eat healthy
What is dysplasia, and how do these cells look?
dysplasia is when cells do not have their normal appearance, instead have enlarged nuclei transition between benign and malignant, cells have not penetrated basement membrane
epithelial cells and basal lamina
epithelial cells- line the outer surface of organs and blood vessels, and inner surfaces of organ cavities basal lamina- layer of extracellular matrix secreted by epithelial cells on which the epithelium sits
How could one tell if an oncogene has been amplified, visually?
fish staining, each amplified gene will fluoresce a different color and will be in pairs since they are visualized in G1 not S phase
what are two ways that chromosomes in a karyotype are identified and how do they generally work?
fluorescence in situ hybridization (FISH)- chromosomes each stained with a different color fluorescent probe -labeling with fluorescent dye, denature and hybridize, hybridization pattern can identify chromosomes banding patterns
What is a major kinase that associates with focal adhesions? How is it that oncogenic Ras may trick cancer cells into thinking they are attached to the ECM, when they are actually not?
focal adhesion kinase, FAK FAK transphosphorylates itself which allows Src to bind it through its SH2 domain Src phosphorylates FAK which allows recruitment of other signaling molecules such as Grb2 and PI3K which initiate Ras and PI3K signaling Integrin and RTK signaling are very similar, activated ras serves as signal for attachment, oncogenic ras tricks cells into thinking they're attached to ECM
In what organism was it initially discovered that X-rays can mutate genes?
fruit flies
how do growth factors maintain tissue architecture?
growth factors govern normal cell proliferation, they are released by cells, travel through the extracellular space and signal to other cells within tissue to grow and divide, allows cell growth for good of tissue not individual cell
interstitial deletions can allow loss of tumor suppressor genes in cancer
growth inhibiting (tumor supressor) genes may be discarded and flanking regions joined, different cancer types have different alterations and deletions ex: neuroblastoma amplifications from chromosome 1 and 17
neoplasia
growths that invade underlying tissue, new type of tissue
what is H&E staining and how can it be used to determine whether or not tissues are cancerous?
hematoxylin and eosin staining is a double staining technique hematoxylin stains dna and histones blue to reveal nuclei by binding to the negatively charged phosphate backbone eosin stains ECM, cytoplasm and connective tissue pink by binding to positively charged proteins in cytoplasm and connective tissue this staining makes it easy to see tissues under the microscope and determine if they are cancerous, cancer cells have larger nuclei
What is hyperplasia and metaplasia, and are these early or late events in cancer progression?
hyperplasia- cells look normal but have divided too much, still assemble into proper functioning tissue metaplasia- normal epithelial layer replaced by cells of another type, cells still normal, often at epithelial junctions both are early in cancer progression
What is the relevance of autocrine signaling in cancer progression?
it allows cancer cells to respond to their own growth factors causing sustained proliferative signaling and aiding cancer progression
How is anoikis involved in the morphogenesis of ducts?
it hollows out the lumen of ducts and the expression of anti-apoptotic Bcl-XL allows cells to survive in the lumen resulting in DCIS
Why is FBS generally required for cells to grow in culture? How is it made, and what does it contain?
it is required for cells to grow in culture because it contains many different growth factors, it is made by extracting fetal blood from the cow fetus after the cow is slaughtered, it contains PDGF which helps with wound healing oncle a clot is formed
the location of the myc proto-oncogene is 8q24.2, what does this mean?
it means it is located on chromosome 8, on the q arm, band 24, sub band 2
How does a Kaplan-Meier survival plot work?
it plots disease free survival against months after diagnosis, the lines are jagged and each dip down indicates a death
Leukemia vs Lymphoma
leukemia- cancer of blood cells found in blood and bone marrow lymphoma- cancer that originates in lymph nodes, B and T cells form large masses
Ras pathway
ligand binds to rtk, which phosphorylates SH2 domain of adaptor protein, SH3 domain of adaptor phosphorylates Ras-GEF which activates Ras by exchanging GDP to GTP
How does the Ames test show whether a substance is mutagenic or not? What are the characteristics of the bacteria used in the assay? Why is liver extract used in the assay? What is the readout of the assay?
liver extract added to test compound used to mimic biochemical processing in live animal metabolically active compound added to mutant salmonella dependent on his for growth, have mutation in gene for histidine synthesis, susceptible to back mutation to wild type upon exposure to mutagen number of colonies grown depends on mutagen strength increased back mutation= carcinogens
glioblastoma multiforme
malignant brain tumor of immature glial cells composed of multiple cancerous cell types including astrocytes which are the non neuronal support cells of the brain
what stage of the cell cycle is analyzed during karyotyping and why?
metaphase of mitosis because it is where the chromosomes are the most condensed and it is easy to take pictures of them
malignant
metastasize to other body parts
Are all mutagens carcinogens, and all carcinogens mutagens? Explain.
more mutagenic= more carcinogenic all mutagens are carcinogens, but not all carcinogens are mutagens anything that damages dna will cause cancer, some carcinogens promote cancer thru methods other than dna damage
most mutations occur in junk dna and do not promote cancer
most of the junk dna is now known to have function and the mutations are neutral, meaning they have no effect, no reduction in ability to compete, allele stays in gene pool selective mutation causes a defective allele leads to defective phenotype, affected individual can't compete, loss of allele from gene pool
What are some proto-oncogenes that are frequently converted into oncogenes by chromosomal rearrangement?
myc, Abl
You have discovered an amplified gene in a cancer patient. Can you be sure that this gene amplification is driving the cancer? Why or why not?
no, because surrounding genes are also amplified
is most of the polymorphic diversity in the human gene pool found in the coding or non-coding regions and why?
non-coding regions because they are inherited like Mendelian alleles but can't be detected phenotypically
normal mammary gland vs invasive ductal breast carcinoma
normal- milk duct lined with epithelial cells, ducts surrounded by stroma made of fibroblasts, adipocytes, and collagen matrix invasive ductal breast carcinoma- cancer cells come from the epithelial cells that once lined the ducts, have abnormally large nuclei due to extra chromosomes, invaded stroma, duct gone
first test of whether substance is carcinogen
paint coal tar on rabbit ears, after few weeks developed skin carcinoma
Parenchyma vs. Stroma
parenchyma- the part of a tissue or organ that contains the cells that perform the functions stroma- the part of the tissue or organ that has a connective or structural role
What is some evidence that cancer risk is more affected by environment than heredity?
people from australia have a higher risk of melanoma than japan because of more time in the sun, and it is near hole in ozone when populations migrate, risk changes to fit new environment
What are some positive and negative feedback loops for the Ras pathway?
positive- degradation of NF1 through phosphorylation by PKC and ubiquitylation allows sustained Ras signaling, the NF1 gets remade later negative- Raf, MEK, Erk cascade activates sprouty which binds Grb2 and prevent further Ras activation, also inhibits RAF. Ras-GAP can also bind to inhibit Ras further
How does GTP binding activate Ras?
ras mutations prevent gtpase activity, amino acids Gly 12, and 61 often mutated in oncogenic ras, their close association with the gamma phosphate of gtp explains why mutation there can eliminate the normal ras proteins gtpase activity and lead to oncogenesis Ras binding to GTP causes conformational changes within Ras that allow substrate binding, switch 1 and switch 2 in ras change conformation when gtp binds which is needed for downstream ligand binding
double minutes allow overexpression of cancer causing genes
segment may be cleaved out of chromosome, replicated as an autonomous extrachromosomal entity, and generate many copies per nucleus double minutes- circular dna fragments with no centromere, small and can be replicated during future cell divisions, can cause gene amplifications, frequently have oncogenes and drug resistance genes
what is the difference between somatic and germline mutations?
somatic mutations occur in a single body cell and cannot be inherited, so only tissues derived from a mutated cell can be affected germline mutations occur in gametes and can be inherited so that every cell is affected
what are some different karyotype alterations that occur in cancer cells?
some chromosomes have inappropriate numbers, multiple chromosome translocations, chromosomal inversion due to radiation
what are the hallmarks and enabling characteristics of cancer according to hanahan and weinberg?
sustaining proliferative signaling, evading growth suppressors, avoiding immune destruction, enabling replicative immortality, tumor promoting inflammation, activating inflammation and metastasis, inducing angiogenesis, genome instability and mutation, resisting cell death, deregulating cellular energetics
Where is a frequent site of metastasis for colon cancer and why?
the liver because the portal vein draws blood from the colon into the liver
What happens if you inject human melanoma cells into a mouse through the tail vein? Can you think of a way that you could test potential chemotherapies for melanoma using this model?
the melanoma cells travel to the lungs because of how the cardiovascular system is set up, can inject chemotherapies through the tail vein after injecting melanoma and see if chemo kills them
What is the effect of HER2/NEU amplification for breast cancer patients in terms of "event-free" survival?
the more her2/neu is amplified, the shorter the event free survival aka relapse her2/neu amplified= poor prognosis
What is the Warburg effect? How do different isoforms of pyruvate kinase regulate this?
the warburg effect is the idea that cancer cells have altered metabolism, instead of converting pyruvate to glucose via glycolysis (oxphos), they convert it to lactate via fermentation (anaerobic glycolysis)- more glucose needed in normal glycolysis, pyruvate kinase isoform M1 regulates the targeting of pyruvate to the mitochondria in fermentation, pyruvate kinase isoform M2 prevents pyruvate from going to mitochondria
How many RAS genes do humans have, and what are the most common mutations that convert these genes into oncogenes? What is the effect of these mutations on Ras function?
there are 3 human ras genes, h ras, n ras, and k ras the most common mutations that convert ras genes into oncogenes are the G12V that makes them unable to hydrolyze bound GTP in all of the ras molecules, the mutations occur at amino acids 12, 13, and 61
How are integrin receptors activated?
through structural change inside-out activation: integrin holds ECM outside cell causing extracellular domain to unfold, disrupts alpha-beta linkage inside cell and allows beta subunit to bind to talin and bind to cytoskeleton outside in activation: talin binds to integrin beta subunit and uncouples alpha-beta linkage, making extracellular portion active and allowing binding to ECM
tissue sectioning for histology
tissue sliced into sections with a microtome to stain and visualize but it must be hardened first stabilize tissue with fixative like formaldehyde and embed in paraffin wax, or freeze and slice with cryostat tissue sections placed on glass slides to stain and visualize by microscopy
early strategy for oncogene detection
transfection technique developed in 1972 mouse fibroblasts grown in culture and treated with mutagen total dna isolated and transfected into non mutagenized fibroblasts each foci caused by one oncogenic mutation induced by original mutagen dna isolated from non transformed cells could not form foci cells from foci injected into mice could form tumors
Which domain is present in all tyrosine kinase receptors?
tyrosine kinase domain single transmembrane domain, both dimerize upon ligand binding signaling outcomes: change cell shape, growth, survival, motility around 60 human RTK's
What happens to epithelial cells that lose contact with the ECM?
undergo programmed cell death called anoikis, also a mechanism to prevent tumor metastasis
How was RAS discovered to be an oncogene?
via a gene overexpression assay ras mutated to oncogenic form in approx 30% of cancers ras is monomeric GTPase activated upon ligand binding to RTK's oncogenic ras mutations often prevent hydrolysis of bound gtp which means ras can't be turned off
What happens to MYC expression when it is driven by the IgH promoter?
when the IgH promoter is translocated in front of the myc gene, expression of the MYC protein is expressed at abnormally high levels and leads to uncontrolled cell growth
what are the writers and readers of the histone code, and how do they affect transcription?
writers- add or remove specific modifications to the code, such as methylating K9, 14, and 27 readers- turn transcription on or off depending on recruitment of other factors NURF: nucleosome remodeling factor, activates transcription H1 and Pc: trigger heterochromatin formation to repress transcription
The Notch pathway contributes to normal and cancerous cell growth
•Notch overexpression occurs in many cancers, including cervical and prostate carcinomas •60% of T-cell acute lymphocytic leukemias have constitutively active Notch oncogenes made up of just the intracellular domain •Contributions of Notch (pro vs. anti-cancer) are cell-type specific
