Identification of cadherin-11 down-regulation as a common response of astrocytoma cells to transforming growth factor-α


Transforming growth factor-α (TGF-α) and its receptor are frequently co-expressed in high-grade astrocytomas, suggesting a role for TGF-α autocrine/paracrine loops in the malignant progression of astrocytomas. To identify genes that may be critical in mediating TGF-α impact on the malignant progression of astrocytomas, we have used cDNA arrays to investigate TGF-α effects on the gene expression profile of U-373 MG glioblastoma cells. We found that in these cells ∼50% of the TGF-α regulated genes code for cell motility/invasion-related proteins. TGF-α action on the expression of four of these proteins, α-catenin, IQGAP1, RhoA, and cadherin-11, was further investigated by immunoblotting in four astrocytoma cell lines and in normal astrocytes. The results demonstrate that the effects of TGF-α on IQGAP1, α-catenin, and RhoA expression are cell-line dependent. On the other hand, under TGF-α treatment, cadherin-11 expression is consistently decreased in all astrocytoma cell lines tested but is increased in normal astrocytes. In addition, we found that cadherin-11 is consistently down-regulated in astrocytomas versus normal brain tissues. Altogether, these results suggest that the down-regulation of cadherin-11 is a frequent molecular event in the neoplastic transformation of astrocytes and that this down-regulation may be initiated and/or amplified by TGF-α autocrine/paracrine loops during tumor progression.

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