Dominant-negative CREB inhibits heparanase functionality and melanoma cell invasion.

Heparanase (HPSE-1) is an endo-beta-D-glucuronidase involved in the degradation of cell-surface/extracellular matrix heparan sulfate (HS) in normal and neoplastic tissues. HPSE-1 represents the first example of purification and cloning of a mammalian HS-degradative enzyme. Elevated HPSE-1 levels are known to be associated with metastatic cancers, directly implicating HPSE-1 in metastatic events. The purpose of this study was to determine the role of cAMP response element-binding protein (CREB) in modulating HPSE-1-mediated effects on human melanoma cell invasion. Highly invasive, brain-metastatic melanoma cells (70W) were transfected with the dominant-negative CREB (KCREB) and subsequently analyzed for changes in their HPSE-1 content, functionality, and cell invasive properties. KCREB-transfected cells showed a decrease in HPSE-1 mRNA expression and activity. This correlated with a significantly decreased invasion of these cells through Matrigel-coated filters. Furthermore, adenoviral vectors containing the full-length human HPSE-1 cDNA in sense orientation (Ad-S/hep) were constructed to investigate CREB effects on HPSE-1. Restoration of HPSE-1 expression and functionality following Ad-S/hep infection of KCREB-transfected 70W cells recovered melanoma cell invasiveness. These results demonstrate that KCREB inhibits HPSE-1 and suggest that one of the roles CREB plays in the acquisition of melanoma cells metastatic phenotype is affecting HPSE-1 activity.