ADAM22, expressed in normal brain but not in high-grade gliomas, inhibits cellular proliferation via the disintegrin domain

Objective: To study the expression and function of the brain-specific proteinase deficient disintegrins, ADAM11 and ADAM22 (a disintegrin and metalloproteinase).

Methods: Specimens of low- and high-grade gliomas and normal brain were analyzed for ADAM11 and ADAM22 expression using Western blotting. The effects of overexpression of ADAM11 and ADAM22 in glioma cells on growth were analyzed using bromodeoxyuridine incorporation linked to immunocytochemistry. Similarly analyzed were the effects on cell proliferation of bacterially expressed Glutathione S-transferase fusion proteins with the disintegrin domain of ADAM11 and ADAM22.

Results: ADAM22 is expressed in normal brain and some low-grade gliomas, but not in high-grade gliomas, whereas ADAM11 is expressed in all low- and high-grade gliomas. In vitro, ADAM22 inhibits cellular proliferation of glioma derived astrocytes. The growth inhibition appears to be mediated by interactions between the disintegrin domain of ADAM22 and specific integrins expressed on the cell surface. This growth inhibition can be avoided by over-expression of Integrin linked kinase.

Conclusion: ADAM22, a brain-specific cell surface protein, mediates growth inhibition using an Integrin dependent pathway. It is expressed in normal brain but not in high-grade gliomas. A related protein, ADAM11, has only a minor effect on cell growth, and its expression is unchanged in low- and high-grade gliomas.