"Altering tumor cell scaffolding: Looking for cytoskeleton-

damaging agents"

Consolato Maria Sergi, MSc, MD, PhDDepartment of Laboratory Medicine and Pathology

University of Alberta

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Technology and The Future of Medicine

Outlines

Eukaryotic Cells contain many organelles and a complex cytoskeleton. Cytoskeleton as scaffolding of a cell. Actin cytoskeleton is organized into bundles and networks of filaments. Intermediate filaments are dynamic polymeric in the cell. Role of signal-transduction pathways in cell locomotion and the organization

of the cytoskeleton. Intermediate filaments in disease. Possible anti-cancer therapy.

Cytoskeleton

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Microtubules

Located in the cytoplasm of all eukaryotic cells 25 nm in diameter ( the thickest fiber type) Built up of Tubulin (β-tubulin & α-tubulin) Movements tracks Separation of the chromosomes Compression resistance

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Microtubules: Centrosomes & Centrrioles

Where the microtubules are initiated

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Microtubules: Cell and cell’s organelles movements

Cilia & Flagella:• protrude from cell surface • cilia: abundant number with 0.25μm in length• flagella: usually 1 – few per cell with 2-20 μmin length • “9+2” patterns

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Microtubules: Cell and cell’s organelles movements

Beating patterns in cilia and flagella

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Microtubules: Cell and cell’s organelles movements

Motor proteins: when the motor protein attaches to organelle, it has the ability to move the organelle along microtubule.

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Microfilaments (Actin filaments)

Built from actin molecules Mechanical support 3D Structural networks inside

plasma membrane Cell motility: contractility

of muscle cells Actin & Myosin: the

contractile engine

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Actin & Myosin: the contractile engine

Myosin : Motor protein

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Actin filaments

Actin cytoskeleton is organized into bundles and networks of filaments

Plasma membrane support

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Actin filaments

Bundles: actin filaments are closely packed in parallel arrays

Networks: actin filaments are crisscross and loosely packed. 3D structure = gel-like cytosol

The filaments of the bundles and networks are connected by actin-cross-linking proteins

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Actin filaments: actin-cross-linking proteins

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The formation of the bundles or networks are highly depended on the flexibility of the cross-linking protein

Actin bundles: e.g. fimbrin & α-actinin

Actin networks: e.g. filamin & spectrin

Intermediate filaments (Ifs)

Diameter: microtubules>intermediat filament> microfilaments

More permanent fixtures of cells

Keratins

Don not have a role in cell motility

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Intermediate filaments are dynamic polymeric in the cell

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3D reconstruction of a cytoskeleton

It is highly useful tool to fully understand the structural and mechanical properties of the cytoskeleton

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Extraction of the graph structure from a detailed section of a secondary electron tomogram. (a) Detail of a tomogram after thresholding.(b) Skeleton of the foreground phase. (c) Extracted network graph after all processing steps, cross-links highlighted by spheres.

Journal of Microscopy, Vol. 239, Pt 1 2010, pp. 1–16

IF network in a detergent-extracted Panc 1 cell visualized at a magnification of 50,000. Filaments in some depth are clearly visible at good contrast in the secondary electron tomogram. The graph extracted from the tomogram exhibits a genuinely 3D structure. (a) SEM image at 0◦ tilt. (b) Horizontal cut through an SEM tomogram. (c) Vertical cut through an SEM tomogram. (d) Tomogram after binarisation (top view). (e) Network graph extracted from the tomogram, top view (left), rotated by 40◦ around central axis (right).

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Journal of Microscopy, Vol. 239, Pt 1 2010, pp. 1–16

3D reconstruction of a cytoskeleton

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Reconstructed 3D cytoskeleton structure visualized by isosurface method.

electron microscope stereo images (400]400 in pixels) of cell cytoskeleton taken at$103 of tilt angles

Journal of Biomechanics 33 (2000) 105}113

Role of signal-transduction pathways in cell locomotion and the organization of the cytoskeleton

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Cont’d

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Hedgehog (Hh) signaling in cancer

Examples: Basal cell carcinomas Medulloblastomas

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http://www.med.umich.edu/derm/research/res_embryonic.shtml

Inhibition of Hh-Gli-1signaling in cancers

Inhibition of human prostate cancer cell proliferation by cyclopamine and GLI1 RNA interference. Cyclopamine inhibits the proliferation of primary in situ prostate tumors (A) and of metastatic prostate cancer cell lines (C), as measured by BrdU incorporation, and inhibits expression of GLI1 (B). Similarly, GLI1 small interfering RNAs (siRNAs) decrease GLI1 and PTCH1 expression (D,F) and inhibit the proliferation of prostate cancer cells (E). The cell line DU145 is not sensitive to cyclopamine while it is sensitive to GLI1 RNAi, suggesting activation of the pathway downstream of SMOH. The efficiency of GLI1 siRNAs in PC3 cells is low due to the low siRNA transfection efficiency.

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Madame Curie Bioscience Database [Internet]. Austin (TX): Landes Bioscience; 2000-.

Thank you