Cell adhesion

Tumour invasion and metastasis is also characterized by alterations in both cell-to-cell and cell-to-matrix adhesion. Cellular adhesion both to adjacent cells and surrounding extracellular matrix is mediated by a variety of molecules including:

Cadherins

Transmembrane glycoproteins involved in cell adenomatous polypo-sis coli (APC) gene product. The most important cadherin in relation to tumour invasion is E-cadherin whose expression is downregulated in various types of malignant tumour; loss of E-cadherin frequently appears to correlate with tumour invasion and metastasis.

Integrins

Transmembrane proteins involved in cell to matrix adhesion. Individual integrins are receptors for a variety of matrix proteins including specific types of collagen, fibronectin, and vitronectin. Cell signalling pathways and expression of MMPs is also partially regulated by integrins. Altered regulation (often downregulation) and expression of integrins contributes to tumour cell invasion.

CD44

A cell surface glycoprotein that functions as an adhesion molecule. CD44 variants can be expressed on the surface of a variety of tumour cells. Specific splice variants of CD44 are associated with increased tumour invasion.

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