Chapter 14: Moving out- Invasion and metastasis

What is meant by metastatic tropism? Postulate molecular mechanisms that could account for such tropisms.

- In some cases, a tumors tendency to spawn metastasis in one or another tissue, reflects the abilities of the cancer cells from the primary tumor to adapt to the microenvironment of distance tissues. This likely explains the strong tendencies of prostate and breast cancers to generate metastasis in the bone marrow. In other cases, the layout of the circulation me strongly influenced the side of metastasis. For example, the high proportion of liver metastasis deriving from primary colon cancers likely reflects the drainage via the portal vein of blood from the colon directly into the liver. - The ability to colonize a certain organ, represents an acquired specialization. Another factor that affects these dynamics are that different types of cancer cells, acquire the ability to colonize a given tissue more or less readily. Thus, the ability of metastasizing prostate cancer cells to colonize. The bone marrow seems to be far more readily acquired than their ability to colonize the liver or the pancreas. They have more limited access to other organs, such as the liver or pancreas, because of their need to undergo more complex adaptations in order to successfully colonize those particular organs.

III. Epithelial to mesenchymal transition (EMT)

- Layer of epithelial cells with a basement membrane underneath. - Become more invasive through the expression of MMPS that are proteins that dissolve the extracellular matrix. The cells that are invading express new proteins. - The formerly tightly packed cells now have decreased cohesion/attachment to each other. Loss of adherens junctions and desmosomes. - Small groups of cells break off from the pile of cells that started forming. Increased motility or incomplete epithelial mesenchymal transition. Go out of the capillary. From epithelial—> mesenchymal.

V. Metastatic tropisms

- Tendency for certain tumors to go to specific places. Ex: prostate cancer Common place it goes to are brain, lungs, liver, and bone marrow. Breast: lungs, liver, & bone marrow Pancreas: lungs and liver Colon: Liver and bone marrow *** Not absolute

IV. Cells, GF, and transcription factors

- Tumor cells stimulate macrophage cells. - Macrophage cells produce proteinases. - Macrophages produce growth factors. - Growth factors stimulate cancer cells. - EMT inducing transcription factors make epithelial cells into stem cells.

What is the evidence that macrophages produce the extra cellular proteins that facilitate the invasion?

A variety of experiments indicate that macrophages are the major source of epidermal growth, factor and breast cancers. EGF is known to be able to stimulate epithelal cancer cells to prolifrate and invade through extra cellular matrix. In addition, EGF exposure causes breast cancer cells to release CSF-1, which allows them to recruit macrophages and stimulates production by the macrophages of more EGF, resulting in a positive feedback loop between these two cell types.

An early step in the metastatic cascade is invasion. What kind of cells do the invasion? Through what do the cell invade? Into what do the cells invade?

Carcinoma cells. They invade the blood and lymphatic vessels. Basement membrane.

What is the epithelial to mesenchymal transition? What are the differences between epithelial and mesenchymal cells? What other cells facilitate the transition?

In order to acquire, motility and invasiveness, carcinoma cells, must shed many of their epithelial phenotypes, detach from epithelial sheets, and undergo a drastic alteration, which is the epithelial mesenchymal transition. Recalled that an EMT involves shedding by epithelial cells of their characteristic morphology and gene expression, and the assumption of a cheap and transcription program characteristic of mesenchymal cells. - Well-differentiated epithelial Morphology: Apical/Basolateral Polarity Physical Characteristics: Cell adhesion & contact inhibition Intercellular Junctions: Adherens, Tight junctions, Gap, Desmosomes Molecular markers: E-cadherin, cytokeratin Cytoskeletal organization: Longitudinal micro tubules & circumferential actin. Invasive mesenchymal Morphology: Leading/Teailing edge symmetry Physical Characteristics: Cell motility and invasiveness Intercellular J: Focal Adhesions & Transient gap junctions Molecular markers: N-cadherin, vlmentin, SMA, & MMP Cytoskeletal organization: Astral microtubules & filepocial stress fibers - The replacement of E-cadherin to N-cadherin during the EMT. E-cadherin enables the epithelial cells to adhere to one another. suppressing the expression of the E-cadherin protein, cells acquire a mesenchymal, morphology and increased motility. - Hepatocyte growth factor (HGF) promotes the E- to N-cadherin switch in cultured epi-blast cells. It induces an EMT and enables emigration of muscle and dermal precursor cells.

What extra cellular proteins are produced to facilitate the invasion?

In some tumors, invading carcinoma cells, make their own proteases, such as MMP-2 and MMP-9, while, and others, a variety of stromal cells are co-opted and induced to release these enzymes, often leading flocks of carcinoma cells behind them. - Macrophages release EGF THAT STIMULATES THE CANCER CELLS TO INVADE. INITIAL STUDIES INDICATE THAT MANY BREAST CANCERS, AND POSSIBLY OTHER CARCINOMAS HAVE A TRIAD OF THREE DISTINCT CELL TYPES. CARCINOMA CELLS MACROPHAGES, AND ENDOTHELIAL CELLS ASSEMBLE TO ENABLE THE CANCER CELLS TO INVADE THROUGH THE ENDOTHELIAL WALLS, INTO THE LUMINA OF THE CAPILLARIES.

I. What is metastasis? The metastatic cascade

Metastasis: A malignant tumor, derived from a primary tumor located at second site from the site of the primary tumor. - Metastasis is responsible for 90% of deaths of cancer patients. Ex: - in a CT Scan you see the blue gray - In a PET scan you see the yellow, density and metabolism of the tissue. - Both could look for disseminated tumors. The metastatic cascade: 1. Primary tumor formation 2. Localized invasion (invade blood vessels) 3. Intravasation( interaction with platelets, lymphocytes, and other blood components). 4. Transport through circulation 5. Arrest in micro vessels of various organs 6. Extravasation(come out of blood vessels through enzymes) 7. Formation of micrometastasis 8. Colonization- formation of macrometastasis - Metastatic cancer is the same cancer as the primary tumor.

II. Invasion and Extravasation

Number 2 of metastatic cascade - Invasion of the basement membrane - Two types: non-invasive (breast intraepithelial neoplasia). Invasive( squamous cell carcinoma). The basement membrane: An extracellular matrix of proteins. Extravasation - Not all cancer cells survive going through circulation. Some do. - Those that do go through vessels and inhabit the organs and grow. Cancer cell attach the endothelial cell and invade the layer through the basement membrane. They multiply and get through the membrane by digesting through it and form micro metastasis.

Metastasis requires that normal cells require many new functions. What is the evidence that transcription factors determine some of these new functions?

TGF-B results in the progressive loss of epithelial morphology in the reduction of epithelial markers, including cytokeratins and E-cadherins. Studies suggested that TGF-B signaling can conspire with a ras-oncogene to cause a epithelial cancer cell to undergo an EMT. TGF-B may often be produced in abundance by the tumor associated stroma.TGF-B contribute to cancer cell invasiveness - TNF-a also acts in concert with TGF-B in inducing an EMT. Early in tumor progression, TNF-a is often produced by inflammatory cells, such as macrophages. It can then function via is receptor to activate the NF-kB pathway in epithelial cells. - TGF-B and TNF-a may contribute to the long-term maintenance of active Nf-kB signaling. This signaling seems to be critical for the induction and maintenance of an EMT, since inhibition of Nf-kB signaling prevents expression of the EMT program.

After the cancer cells invade, what do they do?

They form micrometastases- small clumps of disseminated cancer cells, some of which are able to expand to clinically detectable masses. This growth of microscopic into microscopic metastasis is often termed colonization.

Well-differentiated epithelial vs. Invasive mesenchymal

Well-differentiated epithelial Morphology: Apical/Basolateral Polarity Physical Characteristics: Cell adhesion & contact inhibition Intercellular Junctions: Adherens, Tight junctions, Gap, Desmosomes Molecular markers: E-cadherin, cytokeratin Cytoskeletal organization: Longitudinal micro tubules & circumferential actin. Invasive mesenchymal Morphology: Leading/Teailing edge symmetry Physical Characteristics: Cell motility and invasiveness Intercellular J: Focal Adhesions & Transient gap junctions Molecular markers: N-cadherin, vlmentin, SMA, & MMP Cytoskeletal organization: Astral microtubules & filepocial stress fibers