Dominant-negative transcription factor AP-2 augments SB-2 melanoma tumor growth in vivo

Abstract

We have previously demonstrated that the transition of melanoma to the metastatic phenotype is associated with a loss of expression of the transcription factor AP-2. To further investigate the role of AP-2 in the progression of human melanoma, we attempted to inactivate AP-2 in primary cutaneous SB-2 melanoma cells by using a dominant-negative AP-2, or AP-2B, gene. AP-2B is an alternatively spliced AP-2 variant capable of inhibiting AP-2 trans-activator function. Stable transfection of primary cutaneous melanoma SB-2 cells with the dominant-negative AP-2B gene was con®rmed by RT ± PCR and Northern blot analyses. Electromobility shift assay using nuclear extracts from these cell lines demonstrated decreased functional binding of AP-2B-transfected cells to the AP-2 consensus binding sequence compared with neo-transfected controls. In addition, CAT activity driven by a construct containing the AP-2 consensus binding sequence was downregulated in the AP-2B transfected cells, indicating AP-2 activity was quenched in the transfected cells. Orthotopic (subcutaneous) injection of the dominant-negative (AP-2B)-transfected cell lines into nude mice increased their tumorigenicity compared to control neo-transfected cells. The AP-2B-transfected cells displayed an increase in MMP-2 expression (by Northern blot) and MMP-2 activity (by zymography), which resulted in an increase in invasiveness through Matrigel-coated ®lters. The AP-2B-transfected tumors also displayed an increase in MMP-2 expression, microvessel density, and angiogenesis in vivo. These results demonstrate that inactivation of AP-2 contributes to the progression of melanoma, at least partially via deregulation of the MMP-2 gene.

Jak3- and JNK-dependent vascular endothelial growth factor expression in cutaneous T-cell lymphoma

“…28 AP-2 activity is also inversely correlated with the expression of matrix metalloproteinase-2 (MMP-2), and like VEGF production, MMP-2 expression increases with the progression of CTCL. 3,39 Hence, loss of AP-2 might not only contribute to the VEGF production, but could be important in several aspects of CTCL progression.…”

Transcription factor AP-2α triggers apoptosis in cardiac myocytes

“…AP-2a has also been suggested as a tumor suppressor gene in melanoma cells. 23 Various studies supported the hypothesis that chronic b-adrenergic stimulation of the cAMP-dependent signaling pathway by elevated plasma catecholamines contributes to the altered expression of functionally relevant cardiac genes in human failing heart. 24 b-adrenoceptor antagonists improve cardiac function and prognosis in patients suffering from heart failure due to IDC, 25 and restore expressional alterations of myocardial regulatory proteins.…”

Loss of AP-2α results in deregulation of E-cadherin and MMP-9 and an increase in tumorigenicity of colon cancer cells in vivo

“…This tumor-suppressor-like role of AP-2a in melanoma is directly linked to its ability to regulate the expression of genes involved in adhesion, survival and invasion. For example, loss of AP-2a in metastatic melanoma causes deregulated expression of c-Kit (Huang et al 1998), Melanoma Cellular Adhesion Molecule (MCAM/MUC18) (Jean et al, 1988), Thrombin Receptor (PAR-1) and Matrix Metalloproteinase-2 (MMP-2) (Gershenwald et al, 2001) genes, inducing resistance to apoptosis, adhesion to endothelial cells and increased angiogenesis and invasion, thus promoting the metastatic phenotype (Bar-Eli, 2001). Furthermore, transfection of highly metastatic melanoma cells with full-length AP-2a greatly reduces their tumorigenicity and metastatic potential in nude mice (Huang et al, 1998).…”