Alternatively, inflammation-induced activation of the pro-tumor cytokine family causes epigenetic modifications. A persistent inflammatory response in individuals with ulcerative colitis and inflammatory bowel disease causing oxidative stress and activation of TNF-α and NF-ҡB (tumor promoting cytokines) has been suggested as a major cause for colorectal cancer (Kraus et al., 2009). Activation of cytokines like STAT3 and NF-ҡB can also induce stem cell-like phenotype and stem cell expansion in progenitor tumor cells resulting in larger undifferentiated cell populations as potential targets for environmental mutagens (Grivennikov et al., 2010).
Deactivation of repair enzymes by chronic inflammation, resulting in loss of tumor suppressors has …show more content…
Tumor metastasis involves a series of sequential events, specifically controlled by molecular pathways. Epithelial-mesenchymal transition (EMT) is the first event in this series. EMT is a biologic process involving loss of polarization of epithelial cells that normally interact with basement membrane through its basal surface. These cells endure biochemical changes and transform into mesenchymal phenotypes (Kalluri and Weinberg, 1997). This transformation imparts increased migratory potential, invasiveness and renders the cells resistant to apoptosis. The completion of EMT is involved in disruption of basement membrane through which these mesenchymal cells migrate to underlying tissues (Kalluri and Weinberg, 1997). A second event involves a localized increase in tumor size and induction of angiogenesis to support the tumor growth. This is followed by detachment of cells from the site. Detachment is facilitated by cytoskeletal remodeling and breakage of cell-cell and cell-stroma adhesions; cells migration begins towards the basement membrane. The disruption of the basement membrane is initiated by active secretion of proteolytic enzymes (matrix metalloproteinase); cells enter the systemic circulation through bloodstream or lymphatic system, resulting in spread to distant organs where they proliferate and form secondary tumors (Rucci and Teti,
Deactivation of repair enzymes by chronic inflammation, resulting in loss of tumor suppressors has …show more content…
Tumor metastasis involves a series of sequential events, specifically controlled by molecular pathways. Epithelial-mesenchymal transition (EMT) is the first event in this series. EMT is a biologic process involving loss of polarization of epithelial cells that normally interact with basement membrane through its basal surface. These cells endure biochemical changes and transform into mesenchymal phenotypes (Kalluri and Weinberg, 1997). This transformation imparts increased migratory potential, invasiveness and renders the cells resistant to apoptosis. The completion of EMT is involved in disruption of basement membrane through which these mesenchymal cells migrate to underlying tissues (Kalluri and Weinberg, 1997). A second event involves a localized increase in tumor size and induction of angiogenesis to support the tumor growth. This is followed by detachment of cells from the site. Detachment is facilitated by cytoskeletal remodeling and breakage of cell-cell and cell-stroma adhesions; cells migration begins towards the basement membrane. The disruption of the basement membrane is initiated by active secretion of proteolytic enzymes (matrix metalloproteinase); cells enter the systemic circulation through bloodstream or lymphatic system, resulting in spread to distant organs where they proliferate and form secondary tumors (Rucci and Teti,