Foundations 2 Week 4 part 2

• A Koilocyte is a squamous epithelial cell that has undergone a number of structural changes, which occur as a result of infection of the cell by human papillomavirus (HPV).
• Koilocytes may have the following cellular changes:
• Nuclear enlargement (two to three times normal size)
• Irregularity of the nuclear  membrane contour
• A darker than normal staining pattern in the nucleus, known as Hyperchromasia
• A clear area around the nucleus, known as a perinuclear halo.

• Sensitivity (TP/ TP+FN): 47%
• Specificity (TN/TN+FP): 95%

• Both are non-infectious and contain no viral DNA. Contains viral protein L1 that assembles into a virus like particle.
• Bivalent: Contains L1/VLPs for types 16, 18. It is 93-100% effective against types 16, 18 precancers.
• Quadrivalent: Contains l1/VLPs for types 6, 11, 16, 18. 99% effective against types 6, 11 genital warts, 93-100% effective against types 16, 18 precancers.

• When should it be given? When the patient chooses. Ages 11-12 recommended.  The second dose is given 2 months later, the 3rd dose is given 6 months after the first (4 months after the second). If a dose is missed, give next dose as soon as possible at least 12 weeks after the previous dose.
• It is available for females and males, ages 9-26. Only prevents types not already acquired. Do not give to pregnant women (no data) or to patients with yeast/vaccine allergies.

• Mutations involving an intron can be signified with a + or -, indicating the number of positions away from the exon.  “ins” is used to indicate an insertion (eg, 6154insC).
• A mutation is any change, especially when function is decreased to less than 50% of normal.

• Depurination: A purine (A or G) is randomly kicked out of the sequence.  It may be replaced with a different nucleotide.
• Deamination of Cytosine: Cytosine may lose an amine, which can be replaced with an oxygen to produce Uracil. Uracil then pairs with Adenine (instead of Guanine), introducing an error.
• ROS: ROS (from mitochondria) can react with DNA causing Guanine→8-oxoguanine. 8-Oxoguanine can pair with adenine or cytosine, introducing errors.
• UV: UVB and UVC can cause thymine dimers (two adjacent thymines bond together).  This can be corrected by nucleotide excision repair.
• Alkylation and cross linking: Alkylating agents can add an alkyl group to position 6 of guanine.
• Replication machinery errors: Replication slippage in microsatellites causing deletions or insertions. Triple repeat nucleotides (trinucleotide repeat mutations, eg CGG-CGG-CGG) have the same problem, causing anticipation (the disease worsens in successive generations).
• Fragile X syndrome: Triple repeats on the long arm of the X chromosome (Xq27.3, exhibiting an X-linked inheritance pattern) causes a prominent jaw, retardation, large ears, and large testes. It enlarges when passed from a MOTHER to child, not father to child.

• Due to repairs, a cell can replicate about 50 times before dying, with 3.2 nucleotide errors with each division.
• Base Excision Repair: Excises a bad nucleotide, repairing depurination and cytosine deamination errors.
• Nucleotide Excision Repair: Repair thymine dimers and large chemical adducts (ie, polycyclic carbons, etc)
• Mismatch Repair: MLH1, MSH2, MSH6, PMS2 correct mismatched pairs.
• DNA RecQ Helicase family: Prevents mutations by suppressing recombination. Bloom syndrome can occur from a defect.
• PARP1: PARP1 enzyme causes ssDNA repair
• Double stranded break repair: Occurs through non-homologous end joining (NHEJ), microhomology-mediated end joining (MMEJ), and homologous recombination

• Microtubules are elongated polymeric structures composed of rings of 13 polar α-tubulin + ß-tubulin dimers.  They are aligned head to tail, with ß-tubulin connecting to the next α-tubulin (think legos!).  Microtubules grow on the ß side of the chain by attaching more α-tubulin/ß-tubulin complexes, with the α side of the chain usually attached to the Microtubule Organizing Center (MTOC).
• These subunits can be polymerized or depolymerized (allowing them to polymerize in other locations). Depolymerization is caused by low temperature or high pressure, polymerization is encouraged by high temperatures or low pressure.  MAPs (microtubule associated proteins) can also modify the speed of polymerization/depolymerization and anchor the microtubules to specific organelles.

Microtubules are constantly growing or shrinking until they find an acceptable target (a MAP protein?) on the growing end. This is known as dynamic instability.  Binding to MAPs stabilizes the microtubule.

• Intracellular vesicular transport (e.g., movement of secretory vesicles, endosomes, and lysosomes),
• Movement of cilia and flagella,
• Attachment of chromosomes to the mitotic spindle and their movement during mitosis and meiosis,
• Cell elongation and movement (migration)
• Maintenance of cell shape, particularly its asymmetry.

• ATP-powered molecular motor proteins that use microtubules like train tracks to move transport vesicles, mitochondria, and lysosomes.
• Dyneins move toward the minus end (toward the MTOC)
• Kinesins move toward the plus end (toward the periphery)

• Dynein is responsible for causing cilia movements.  
• A defect can cause Kartagener’s syndrome, presenting dysfunction of microtubules and sperm motility.

• Drugs (like paclitaxel, aka taxol) can stabilize microtubules, arresting development in various stages.
• Other drugs (like vinblastine and vincristine, aka oncovin) can destabilize microtubules, preventing mitosis.

• Free actin molecules in the cytoplasm are called G-actin. Polarized filament actin is called F-actin.  Filaments have a fast growing plus (barbed) end and a slow growing minus (pointed) end.
• Actin-Binding Proteins (ABPs) interact with G-actin to prevent or enhance polymerization.

• Fascin and fimbrin: Cross-link (bundle) actin filaments into parallel arrays (actin filament bundles)
• Gelsolin: An actin filament-severing protein. It cuts long actin filaments into short fragments at high [Ca2+].
• Tropomodulin: Actin-capping protein. It binds to the active end of actin myofilaments to prevent further additions.
• Spectrin: An actin cross-linking protein. It cross links actin filaments with each other.
• Myosin I and II: Actin motor proteins. Myosin II forms thick filaments in muscle cells. Myosin I provides motor functions in specialized non-muscle cells/

• Intermediate filaments are nonpolar ropelike filaments with a diameter between that of microtubules and actin filaments.  They have a long rod-shaped domain and globular domains at either end.
• The rod-shaped domains twist together to form dimers (like two wires placed side by side and then twisted together). The dimers combine into tetramers and then are staggered and stacked into a coil of 8 tetramers.
• Intermediate filaments are cytoskeletal components.

Simple epithelia, stratified epithelia, and structural keratins (aka, hard keratins, found in hair and nails).

Many cell types, including all mesoderm derived cell types, muscle cells, and nerve cells.

Also called neurofilaments, they are expressed in the axons of nerve cells.

Lamins are found in the nucleoplasm of almost all differentiated cells, and is associated with the nuclear envelope.

Alzheimer’s disease (neurofibrillary tangles), Alexander disease (mutation in the GFAP gene, resulting in cytoplasmic inclusions in astrocytes).

• The MTOC contains centrioles and an amorphous pericentriolar matrix of more than 200 proteins, including γ-tubulin that is organized in ring-shaped structures. Each γ-tubulin ring serves as the starting point (nucleation site) for the growth of one microtubule that is assembled from tubulin dimers; α- and ß-tubulin dimers are added with specific orientation to the -tubulin ring.
• The minus end of the microtubule remains attached to the MTOC, and the plus end represents the growing end directed toward the plasma membrane.
• 

Centrioles provide basal bodies for cilia and flagella and align the mitotic spindle during cell division.

Centrioles consist of nine fused triplets of microtubules.

Increased receptors or stronger binding will strengthen signals to proliferate.

Activation of these proteins causes proliferation.

PTEN and MTOR inhibit PI3 activity, so loss of function of PTEN or mTOR results in increased cell proliferation.

RB and TP53 are both tumor suppressors. RB responds to signals from within, but mostly from without the cell (ie, extracellular signals).  TP53 responds to signals and stress only from within the cell.

• Cells in contact can suppress tumor growth in one another as demonstrated in chimeric mice missing RB proteins in chimeric clusters of cells.  Nearby cells with the NF2 gene produce Merlin proteins which couple cell-surface adhesion molecules together. LKB1 is also involved in contact inhibition.
• The loss of contact inhibition therefore promotes cancer.

• The extrinsic apoptotic program: Receives and processes extracellular death-inducing signals, e.g. Fas ligand/Fas receptor
• The intrinsic apoptotic program: Receives death-inducing signals from inside the cell.  Considered a more important barrier to cancer pathogenesis

Mitochondria release cytochrome C, which induces cell death.  Mitochondria also have an BAK surface receptor that inhibits cytochrome C release.

• They use several strategies, including...
• The loss of TP53 tumor suppressor
• By increasing the expression of antiapoptotic regulators (eg, Bcl-2, Bcl-xL) or survival signals (lgf1/2)
• by downregulating proapoptotic factors (Bax, Bim, Puma)
• by short-circuiting the extrinsic ligand-induced death pathway.

Autophagy and apoptosis are often signalled together.  For example, the signaling pathway involving the PI3-kinase, AKT, and mTOR kinases, which is stimulated by survival signals to block apoptosis, similarly inhibits autophagy.  Beclin-1 triggers either autophagy or apoptosis, depending on the cell’s status.

Necrotic cell death releases proinflammatory signals into the surrounding tissue, causing inflammatory cells and growth factors to be released.  This causes angiogenesis and tumorigenesis.

Telomerase is expressed much more in immortal cells, preventing telomeres from shortening. Telomeres protect the ends of chromosomal DNA from end-to-end fusions, so shortening telomeres limits the life of a cell.

VEGF-A, FGF

hypoxia, oncogenic signaling

• TSP-1
• fragments of plasmin (angiostatin)
• type 18 collagen (endostatin)

Pericytes, a variety of bone-marrow derived cells (macrophages, neutrophils, mast cells, myeloid progenitors, vascular progenitor cells)

Epithelial-mesenchymal transition is a process by which epithelial cells lose their cell polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal cells.  EMT has been shown to occur in wound healing and in the initiation of metastasis for cancer progression.

• stromal cells are connective tissue cells of any organ.
• Stromal cells adjacent to the epidermis release growth factors that promote cell division. This keeps the epidermis regenerating from the bottom while the top layer of cells on the epidermis are constantly being "sloughed" off of the body. Certain types of skin cancers (basal cell carcinomas) cannot spread throughout the body because the cancer cells require nearby stromal cells to continue their division.
• Stroma provides an extracellular matrix on which tumors can grow.

• Inflammation results in...
• Growth factors for proliferation
• Survival factors to limit cell death
• Pro-angiogenic factors to promote angiogenesis
• Matrix modifying/ digesting enzymes to facilitate angiogenesis, invasion, and metastasis
• Inductive signals for activation of EMT

Cancer cells upregulate Glut1, a glucose transporter.

Hypoxia increases the levels of the HIF1α and HIF2α transcription factors, which in turn upregulate glycolysis.

• The Warburg effect is the observation that most cancer cells predominantly produce energy by a high rate of glycolysis followed by lactic acid fermentation in the cytosol, rather than by a comparatively low rate of glycolysis followed by oxidation of pyruvate in mitochondria.
• Malignant cells typically have glycolytic rates up to 200 times higher than those of their normal tissues of origin.
• This occurs even if oxygen is plentiful.
• PET scans use this principle and monitor uptake of 2-18F-2-deoxyglucose (FDG)

• Tumor cells…
• Paralyze infilterating NK and Tc cells by secreting immunosuppressive factors (TGF-b)
• Recruit anti-inflammatory cells that are actively immunosuppressive (Tregs and MDSCs)

• Stromal cells cause angiogenesis
• Nearby lymphatics serve as a key to seeding
• Pericytes-poor pericyte coverage allows for cancer cell invasion
• Immune cells actually help the tumor grow, release EGF (tumor growth factor), VEGF, FGF2, MMPs/ Myeloid cells suppress CTL and NK activity (MDSCs)
• Fibroblasts and myofibroblasts-secrete ECM, enhance cell proliferation and angiogenesis
• Heterotypic signaling (cross talk between cancer and normal cells) allows cancerous cells to stimulate cells to produce necessary growth/angiogenic factors.

• Descriptive epidemiology: The study of cancer’s distribution in human populations through surveillance.
• Analytic epidemiology: The study of cancer’s determinants in human population.

• Molecular epidemiology: The examination of biological markers of exposure, disease, and points in between.  Biomarkers include cytokines, acute phase proteins, SNPs, Fatty acid in blood, tumor histology, prostate-specific antigen (PSA) test, breast density, etc.
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• Keratinized stratified squamous epithelium is found in the skin.
• Non-keratinized stratified squamous epithelium is found in the oral cavity including the tongue and lips, cornea, true vocal cords, esophagus; vagina; cervix, and anus