tumorigenesis

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

• overexpression of growth factors
  • IL3 (IGH) by translocation t(5;14)(q31;q32) in B-lineage acute lymphoblastic leukemia with eosinophilia

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

Localization

 digestive tumorigenesis
 endocrine tumorigenesis

• neuroendocrine tumorigenesis
• thyroid tumorigenesis

 gliomagenesis (tumorigenesis of glioma )
 mammary tumorigenesis

See also

 multistep tumorigenesis

References

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