Exam I Flashcards
Cancer
A disease of disordered cell proliferation resulting in invasion and metastasis; A genetic disease, resulting from mutations
Probability of Developing Cancer
Men: 50%
Women: 33%
Cancer is the #2 killer in the US
Histology
The study of the microscopic anatomy of cells and tissues of plants and animals
Tumor
An abnormal mass of tissue formed by an abnormal growth of cells: benign and malignant; multicellular
Cancer
Malignant; Single cell or multicellular
Primary Tumor
The original tumor
Metastasis
Formed by cancer cells that have spread from other parts of the body
Benign
Tumor grows locally without invading adjacent tissues
Malignant
Tumor invades nearby tissues
Cancer Division
Carcinomas, [Sarcomas, Leukemia/Lymphoma, Neuroectodermal tumors] –> non-epithelial cancers, Others
Carcinomas Division
Squamous cell carcinomas, Adenocarcinomas
Cancer Occurrence
Carcinomas (80%), Sarcomas (1%), Leukemia/Lymphomas (7%), Neuroectodermal Tumors (2.5%), Others (5-10%)
Carcinomas
Derived from epithelial cells; Responsible for >80% of cancer-related deaths; 2 types: squamous cell carcinomas and adenocarcinomas
Squamous Cell Carcinomas
Form from the protective epithelial cells
Adenocarcinomas
Form from the secretory epithelial cells
Sarcomas
Derived from mesenchymal cells; Originate in stroma; Responsible for about 1% of tumors
Leukemia/Lymphomas
Derived from blood-forming (hematopoietic) cells; Responsible for about 7% of cancer-related deaths
Neuroectodermal Tumors
Derived from the nervous system; Responsible for about 2.5% of cancer-related deaths
How do Tumors Grow?
- Tumors develop progressively!!!!!
- Tumors are monoclonal growth
- Cancer cells exhibit an altered energy metabolism
- Specific physical, chemical, or viral agents induce cancers
- The great majority of the commonly occurring cancers are caused by environmental factors
Journey to Malignancy
Normal cell –> Hyperplastic/Metaplastic –> Dysplastic (transitioning stage) [STILL BENIGN] –> Neoplastic/Locally Invasive [NOW MALIGNANT] –> Metastatic
Normal Cells
Normal appearance, normal division, normal assembly
Hyperplastic Cells (Hyperplasia)
Normal appearance, abnormal division, normal assembly (BENIGN)
Metaplastic Cells (Metaplasia)
Normal appearance, normal division, abnormal assembly (BENIGN)
Dysplastic Cells (Dysplasia)
Abnormal appearance, abnormal division, abnormal assembly (TRANSITIONING STAGE; BENIGN)
Locally Invasive Tumors
Abnormal appearance, abnormal division, abnormal assembly, invasion of adjacent tissues
Metastatic Cancer (Metastases)
Abnormal appearance, abnormal division, abnormal assembly, invasion of adjacent tissues, spread to other organs
Hyperplastic milk ducts
Cells are protruding into the lumen of the milk duct
Monoclonal
All cells of a tumor come from a single mutated cell
Altered Energy Metabolism
Normal cells rely primarily on oxidative phosphorylation to generate energy; Cancer cells primarily rely on aerobic glycolysis to generate energy
Warburg Effect
The observation that most cancer cells obtain their energy from glycolysis, even in the presence of abundant oxygen; “Aerobic glycolysis”
Carcinogen
An agent involved in the promotion of cancer (Example: coal tar, a chemical agent); Composed of initiators (mutagens, 60%) and promoters (signal promotes cell division, 40%)
Mutagen
An agent that changes the genetic information (Examples: X-ray; WWII chemical agents)
Induction of Cancer
First successful induction of cancer by treatment of rabbit ears with coal tars by Katsusaburo Yamagiwain
Cancer-Causing Agents
Chemical Agents, Physical Agents, and Viral Agents
Ames Test
Test for mutations; Treat bacteria with substance; Try to grow bacteria in condition under which it should NOT be able to live; Those that survive mutated
Mutagenic and Carcinogenic Potency
Mutagenicity and Carcinogenicity are directly correlated
Carcinogens vs. Mutagens
All mutagens (mutating DNA) are carcinogens (promoting cancer), but not all carcinogens (promoting cancer) are mutagens (mutating DNA).
Factors that Contribute to Cancer Development
1) Heredity 2) Environment (most common cancers are caused by environmental factors)
Incidence Rates
The rates with which the disease is diagnosed; Cancer incidence rates are dramatically different among different populations
Viruses
Human cells are 10-30 micrometers; Bacteria 2 micrometers; VIRUSES 10-300 nanometers; Viruses need bacteria, plant, or animal cell to grow and reproduce; Consist of a genome (DNA or RNA) wrapped in a protein coat (capsid); Can be virulent or temperate
Virulent vs. Temperate Viruses
Virulent means the cell is lysing and spreading the virus; Temperate means the cell continues living; ALL CANCER VIRUSES ARE TEMPERATE
Peyton Rous
Took chicken with sarcoma in breast muscle; removed sarcoma and broke it up into small chunks of tissue; Ground up the sarcoma with sand; Collected the filtrate that passed through a fine-pore filter; Injected the filtrate into young chickens; Observed sarcoma in injected chickens
Howard Temin
Transformed chicken embryo fibroblasts using robs Sarcoma Virus (RSV); Normal cells had contact inhibition, elongated shape, and were non-refractile (dark); RSV-Transformed Cells had no contact inhibition; rounded shape, and were refractile (white)
Focus (Plural: Foci)
Cell clusters
Monolayer
One-cell thick layer of cells
Contact Inhibition
A natural process of arresting cell growth when two or more cells come into contact with each other
Transformation
Conversion of a normal cell into a tumor cell
Anchorage-Independent Growth Assay
Agarose prevents cell attachment…incubate…all cells except transformed cells will die
Acid Test
A generically critical test that gives a definitive answer
Tumorigenicity
The ability of cultured cells to give rise to either benign or malignant progressively growing tumors in immunologically non-responsive animals
Provirus
The DNA version of the viral genome
Retrovirus
A single-stranded positive-sense (pairs with mRNA) RNA virus with a DNA intermediate in the host cells
Genes of RSV
[gag (core proteins), pol (reverse transcriptase), env (virus surface proteins)] –> Required for Replication, [src (presumably causes transformation)] –> Required for Transformation
RSV Production
RSV is a side-product of avian leukosis virus (ALV) production; On occasion, the c-src gene will be transcribed with the ALV provirus, making v-src, making RSV (EXTREMELY RARE)
Oncogene
A gene capable of transforming a normal cell into a tumor cell (causes cancer); v-src
Proto-Oncogene
The precursor of an active oncogene (could cause cancer); c-src
Concept of Proto-Oncogene
1) Implied that the genomes of normal cells carry genes that have the potential to induce cancer
2) Implied that other tumor viruses may convert other porto-oncogenes into oncogenes using a similar mechanism
3) Implied that porto-oncogenes can be activated by other mechanisms than viruses, such as mutation
4) Implied there might be many more proto-oncogenes
ALV Causing Cancer
When B-cell lymphomas caused by ALV where analyzed, it was found that ALV always inserted into DNA segment containing c-myc (proto-oncogene); As an oncogene, c-myc would cause uncontrolled cell growth
Insertional Mutagenesis
Activation of cellular proto-oncogene by inserting provirus near the proto-oncogene; Almost ALL retroviruses have the potential to induce cancer
Human T-Cell Leukemia Virus (HTLV-I)
A retrovirus that carries its own endogenous viral oncogene, tax; tax is an intrinsic HTLV-I viral gene whose product stimulates expression of cellular GF
3 Types of Retroviruses that Induce Cancer
1) Carry no oncogenes (ALV) (weeks to months due to random insertion)
2) Carry acquired oncogenes (RSV) (days to weeks due to presence of oncogene)
3) Carry endogenous viral oncogenes (HTLV-I) (days to weeks due to presence of oncogene)
DNA Viruses
Do NOT generally insert into host chromosome
Common Causes of Viral Cancer in US
Papillomavirus and Hepatitis
Viral Cancer Incidence
Responsible for about 20% of all cancers
Transfection of DNA as Strategy to Detect Oncogenes
Provides evidence that a cellular gene can be mutated by a chemical or physical agent to cause cancer
Transfection
A technique of introducing foreign genetic material into eukaryotic cells
6 Molecular Mechanisms of Porto-Oncogene Activation
1) Point Mutation
2) Gene Amplification
3) Chromosomal Translocation
4) Translocations liberating an mRNA from miRNA inhibition
5) Deregulated firing of GF-R
6) Formation of oncogene through reciprocal chromosomal translocations
ras
Molecular switch; On (active) or off
myc
Transcription factors increase the amount of DNA, driving cell proliferation
HMGA2
Causes cancer when expressed in large amounts
EGF-R
Tyrosine-kinase receptor: divide or not
bcr-abl
Tyrosine-kinase receptor: divide or not
ras Point Mutation
Nearly all mutations occur at AA residue 12, some at 13, few at 61; ras oncogenes are involved in >20% of human tumors
Gene Amplification
The production of multiple copies of a particular gene or genes
Amplicon
The region of chromosome DNA that undergoes amplification; Homogeneously Staining Region (HSR)…end-to-end linear arrays of amplified segments; Double Minutes…the region carrying the amplified segments breaks away from the chromosome, forming extrachromosomal particles
Amplicon might be visible in metaphase.
Gene amplification doesn’t always equal over-expression (not always more protein)
myc Amplification
N-myc is amplified to 10-150 copies, responsible for 40% of advanced pediatric neuroblastomas; Chromosomes are BIGGER in cancer cells
Kaplan-Meier Plot
The percentage of patients surviving is plotted as a function of time after initial diagnosis or treatment
Chromosomal Translocations in Burkitt’s Lymphoma
B-Cell Lymphoma; Malaria and Epstein-Barr Virus (EBV) are cofactors to Burkitt’s Lymphoma; Normal chromosome 8 has myc and 14 has IgH; Burkitt’s Lymphoma has t(8;14) causing 8 to have IgH and 14 to have myc; Also can have t(8;22) or t(8;2)
-c-myc is placed under the control of the IgH promoter sequence, causing A LOT of protein to be produced
HMGA2 Proto-Oncogene Activation
HMGA2 is expressed when cells are dividing; Normally, miRNA controls translation of HMGA2 by degradation based on physiological conditions…if the 3’ UTR region is replaced by gene X, lost binding site for miRNA, no control
Growth Factors
Naturally occurring proteins capable of stimulating cellular growth, proliferation, and cellular differentiation
EGF
Epidermal growth factors
EGF-R
Epidermal growth factor receptors
Deregulated Firing of GF-R
The tyrosine kinase receptor can have the extracellular domain removed (truncated genetically) so that a signal to grow is CONSTANTLY emitted
bcr-abl Oncogene Formation
Chromosome break and recombination forms a FUSION ONCOPROTEIN, a hyperactive, completely new protein
3 Ways for myc to Cause Cancer
Gene amplification, viral promoters, strong cellular gene promotor
3 Phosphorylated AA
Threonine (Threonine Kinase), Serine (Serine Kinase), [Tyrosine (Tyrosine Kinase)] –> CRITICAL role in cell proliferation
- 99.9% of kinases are T or S
- 0.1% of kinases are Y
src is a Tyrosine Kinase
src (the first oncogene discovered) makes a cell express many proteins (confirmed by Western Blot) which are phosphorylated by tyrosine kinase, indicating that src is a tyrosine kinase
EGF-R
3 Functional Domains: Ectodomain (621 AA), Transmembrane Domain (23 AA), and Cytoplasmic Domain (542 AA)
-The cytoplasmic domain shows homology (similar in sequence and structure) with src, so EGF-R is a tyrosine kinase receptor
Tyrosine Kinase Receptors
Consist of 3 domains, all of which are diverse except the highly conserved tyrosine kinase domain; A favorable target for treating/curing ailments/cancer
Tyrosine Kinase Receptor Function
1) Based highly upon the Fluid Mosaic Model
2) If GF is added, the receptor becomes a stable dimer (without GF, the receptor is a monomer)
3) Dimer is essential for transphosphorylation
Making EGF-R (or any tyrosine kinase receptor) Oncogenic
Essentially making the receptor LIGAND INDEPENDENT
1) Truncation by deleting the ectodomain
2) Point Mutation requiring no GF
3) Overexpression due to ligand-independent firing
4) Genome Instability causing gene fusion, forcing the dimerization of receptors and continuous firing
Simian Sarcoma Virus (v-sis)
Normal Cells Do NOT Produce Their Own Ligands; Epithelial cells have EGF-R and Mesenchymal cells have PDGF-R (platelet-derived growth factor receptor); Epithelial cells produce PDGF and Mesenchymal cells produce TGF (transforming growth factor); v-sis is very similar to PDGF, not affecting Epithelial cells but transforming Mesenchymal cells (AUTOCRINE signaling)
Signaling Molecules
The great majority of signaling molecules in the cell are PROTEINS
Signaling Cascade
Ordered sequence of biochemical reactions inside the cell with HIGH specificity and HIGH speed
Fruit Fly Eye
Ommatidia: light-sensing unit of fruit fly eye
- Each ommatidium is formed by seven cells
- Sevenless gene (one cell missing in ommatidium) encodes a homolog of the FGF-R (fibroblast growth factor receptor)
Son of Sevenless (Sos)
Functions downstream of the Sevenless and activates Ras; Sos in fly = GEF (guanine nucleotide exchange factors in yeast); GEF activates Ras proteins…Ras is a molecular switch, switching GDP to GTP (active form)
Localization Model
Receptor Tyrosine Kinases (RTKs) affect the physical location of downstream components without necessarily changing their intrinsic activity by 1) Attracting molecules to their location after activation and 2) src can be recruited to cytoplasmic domain of tyrosine receptors
Src Protein
Contains 3 Domains: SH1 (catalytic domain; kinase domain; phosphorylates using ATP), SH2 (binding to pY-containing peptide), SH3 (binding to proline-rich sequence domain)
SH2 Groups
Typical SH2 domain is composed of 100 AA; One binding site binds to pY with great affinity while the other binds nearby AA on C-terminus side
- SH2 functions as modular plug
- Human genome encodes at least 120 types of SH2 groups
- Certain AA sequences after pY determine the specificity for substrates
- Substrates binding intracellularly are responsible for the response after ligand binding
Ras in Signal Cascades
- Ras is a protein that is ALWAYS attached to the inner surface of the plasma membrane
- Ras is a G-protein
- Ras is inactive when bound with GDP
- Ras is active when bound with GTP
- RTK –> Grb2 –> Sos –> Ras
- RTK –> Shc –> Grb2 –> Sos –> Ras
Ras Effector Loop
The effector loop interacts with 3 important downstream effectors of Ras; Mutations can prevent GTP –> GDP, causing unchecked activation of Ras
- Bound to GDP; effector loop cannot bind to downstream molecules (Raf, PI3K, Ral-GEF)
- Bound to GTP; conformational change of effector loop increases affinity for Raf, PI3K, Ral-GEF
3 Important Downstream Signaling Pathways of Ras
1) MAPK Pathway
2) PI3K Pathway
3) Ral-GEF Pathway
MAPK Pathway
Mitogen-Activated Protein Kinase (MAPK) Pathway; GTP-Ras attracts Raf, binding of both leads to conformational change of Raf; Raf phosphorylates MEK; MEK phosphorylates both Y and S/T kinases; Erk 1 or 2 phosphorylates and activates TFs (ex: cyclin D1) and other proteins
-Deregulation can increase kinase activity, causing increased cell proliferation
PI3K Pathway
Ras activates PI3K (phosphatidylinositol 3-kinase); PI3K synthesizes PIP3 (phosphatidylinositol (3,4,5) triphosphate); PIP3 is a special type of phospholipid; PIP3 attracts Akt/PKB (very powerful kinase) and Rho-GEFS
Akt/PKB form PI3K Pathway
Causes:
- Bad inhibits apoptosis
- mTOR stimulates protein synthesis (cell growth)
- GSK-3beta stimulates cell proliferation
Phosphatidylinositol (PI) and its Phosphorylation
- PI is part of the inside of the plasma membrane
- PI is composed of two fatty acids with long H-C tails, glycerol, and inositol
- PI, PI (4,5)-diphosphate (PIP2), and PI (3,4,5)-triphosphate (PIP3) are tethered to plasma membrane
PIP3 Synthesis
- PIP3 formation is controlled by PI3K and PTEN
- PIP3 serves as docking site for Akt/PKB
- Once bound to PIP3, Akt/PKB becomes phosphorylated and activated
- PTEN is a phosphatase, converting PIP3 to PIP2 (important for tumor suppression)
