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Sunday 13 July 2003

carcinogenesis, oncogenesis, tumoral transformation ; tumorigenicity

Definition: Tumorigenesis is a collection of complex genetic diseases characterized by multiple defects in the homeostatic mechanisms that regulate cell growth, proliferation and differentiation.

Cancer is caused by uncontrolled proliferation and the inappropriate survival of damaged cells, which results in tumour formation. Cells have developed several safeguards to ensure that cell division, differentiation and death occur correctly and in a coordinated fashion, both during development and in the adult body.

Many regulatory factors switch on or off genes that direct cellular proliferation and differentiation. Damage to these genes, which are referred to as tumour-suppressor genes and oncogenes, is selected for in cancer.

Most tumour-suppressor genes and oncogenes are first transcribed from DNA into RNA, and are then translated into protein to exert their effects. Recent evidence indicates that small non-protein-coding RNA molecules, called microRNAs (miRNAs), might also function as tumour suppressors and oncogenes.

Mechanisms (Examples)

- activation of oncogenes

- sequential inactivation of tumor suppressor genes
- tumoral pathways
- tumoral epigenetics
- inflammatory-mediated tumorigenesis


- digestive tumorigenesis
- endocrine tumorigenesis

- gliomagenesis (tumorigenesis of glioma )
- mammary tumorigenesis

See also

- multistep tumorigenesis


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