Cancer

Cancers arise when cells escape normal controls on cellular proliferation. Cancer is not a single disease, rather the term encompasses a group of conditions that share the characteristic process of uncontrolled cellular proliferation of cells that are typicallly capable of local infiltration into other tissues (invasion). This propensity for invasion and migration is associated with the capacity to metastasize to sites distant from the point of origin. Benign tumors evidence as local overgrowth, but fortunately have minimal or no propensity for tissue infiltration and metastasis. Cancers originating in the same tissue/organ can vary considerably in degree of undifferentiation, sensitivity to chemotherapeutic agents, growth rate, invasiveness, and metastatic potential.

Alteration of a gene that normally controls cell growth can promote the uncontrolled growth characteristic of cancer. The normal forms of dominant genes that function in the various signal transduction cascades that regulate cell growth, proliferation and differentiation are termed proto-oncogenes, and the malignantly transformed genes are termed oncogenes.

For example, mutation in a proto-oncogene, such as a gene which encodes an intracellular signaling protein that is normally activated only by extracellular growth factors, converts the proto-oncogene into an oncogene. The malignantly transformed oncogene encodes an altered form of the signaling protein that now behaves as though activated even in the absence of growth factor binding. The malignant cell line has escaped normal gene regulation and cell cycle control mechanisms and exhibits unchecked proliferation.

A propensity for invasion and metastasis is a critical feature that distinguishes malignancies from benign tumors.

There are many excellent sites with information for those affected by cancer, so the purpose of this site, in conjunction with the companion sites, is an exploration of the cell and molecular biology of malignancy.

synonyms : cancer, tumor, malignancy, neoplasm; cancerous, tumorous, malignant, neoplastic; cancer, neoplasia, oncology.

¤¤ adenoviruses ¤ amplification ¤ carcinogenesis ¤ c-Fos ¤ c-Jun ¤ c-Myc ¤ c-Sis ¤ estrogen receptors ¤ gene amplification ¤ genetic predispositon ¤ HBV ¤ HIV ¤ HPV ¤ HTLV-I ¤ immune evasion ¤ irradiation ¤ malignant transformation ¤ metastasis ¤ mitogens ¤ mutagens ¤ MYC ¤ mutations ¤ neoplasia ¤ neoplastic mutations ¤ NF-κB ¤ non-mutagenic carcinogens ¤ oncogenes ¤ p53 ¤ proliferation ¤ proto-oncogenes ¤ radiation ¤ Ras ¤ Rb ¤ retroviral mechanisms of carcinogenesis ¤ retroviruses ¤ signaling molecules ¤ SRC genes ¤ T-antigens ¤ TP53 ¤ tumor antigens ¤ tumor suppressors ¤ tumorigenic viruses ¤ viral carcinogens ¤ v-Fos ¤ v-Sis ¤ v-Myc ¤

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tags [Cancer] [proto-oncogene] [mutation] [oncogene] [metastasis]

| 2 Guide-Glossary

metastasis

Metastasis is cell motility run amok.

Malignant tumors exhibit not only uncontrolled proliferation and local invasion, but the ability to set up distant colonies. Growth and survival of metastatic tumor cells depend upon angiogenesis and the ability of tumor cells to evade detection by the immune system.

Metastasizing cells escape normal cellular adhesion mechanisms and shed from the primary tumor. Local invasion can enable the 'escapee' cells to penetrate lymphatics and/or blood vessels. Local infiltration of lymph nodes is associated with an increased likelihood of metastasis, so determination of whether or not lymph nodes are involved is important in cancer staging.

Having been transported via circulation of lymph or blood, the malignant cells invade distant tissues where they establish focal colonies of proliferating cells (secondaries). Tumors originating in certain tissues often display a propensity for metastasis to specific tissues and organs.

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| 0 Guide-Glossary