Inhibition of histone deacetylase activity promotes invasion of human cancer cells through activation of urokinase plasminogen activator.

Histone acetylation plays an important role in chromatin remodeling and gene expression. The molecular mechanisms involved in differential regulation of urokinase plasminogen activator (uPA) gene expression are not fully understood. In this study, we investigated whether histone deacetylation was involved in repression of uPA expression in human cancer cells. Induction of uPA expression by histone deacetylase (HDAC) inhibitors trichostatin A (TSA), sodium butyrate, and scriptaid was observed in all three different types of human cancer cells examined. Chromatin immunoprecipitation assays showed that the induction of uPA expression by TSA was accompanied by a remarkable increase of acetylation of histones H3 and H4, which are associated with the uPA promoter region in human cancer cells. These results were further substantiated by the findings of a restriction enzyme accessibility assay and TSA-stimulated uPA promoter activity through the inhibition of HDAC activity. In vitro Matrigel invasion assays showed that induction of uPA expression by HDAC inhibitors in human cancer cells resulted in a significant increase of cancer cell invasion. Furthermore, HDAC1 knockdown by small interference RNA stimulated uPA expression and cancer cell invasion. In conclusion, this study demonstrates the important role of histone modifications in regulating uPA gene expression and raises a possibility that the use of HDAC inhibitors in patients as cancer therapy may paradoxically establish metastasis through up-regulation or reactivation of uPA.