Chapter 31

Neoplasia of the Gastrointestinal Tract

Ofer Margalit

Ofer Margalit

Biodesign Institute, Arizona State University, Tempe, AZ, USA

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Raymond N. DuBois

Raymond N. DuBois

Biodesign Institute, Arizona State University, Tempe, AZ, USA

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First published: 27 November 2015

Summary

Factors that increase the rate of acquired genetic alterations in gastrointestinal (GI) malignancies are either extrinsic, including exposure to chemicals (e.g., tobacco), viruses, or bacteria, or intrinsic, such as dietary habits. Both genetic and epigenetic alterations ultimately lead to abnormal gene expression of at least three distinct types of genes, namely oncogenes, DNA repair genes, and tumor suppressor genes (TSGs), which cooperatively drive carcinogenesis. In order to sustain proliferation, apart from gaining constitutive proproliferative signaling, cancer cells must disable the counteracting programs that are aimed at inhibiting proliferation. The three main TSG pathways involved in GI malignancies are the p53, retinoblastoma (RB), and transforming growth factor-β (TGF-β) pathways. Telomeres affect two critical hallmarks of cancer, namely cell cycle control and genetic instability. Tumor cells may reactivate or overexpress telomerase through a variety of mechanisms. Intense efforts had been directed to development of therapeutic agents targeting telomerase.

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