Epigenetic regulation of proMMP-1 expression in the HT1080 human fibrosarcoma cell line

The matrix metalloproteinase (MMP) family members play an important role in various physiological and pathological processes. Although MMP-1 (collagenase-1) has been shown to be involved in tumor invasiveness, the regulation of its expression is still not fully elucidated and could implicate epigenetic mechanisms. The aim of this study was to analyze the effects of the Histone Deacetylase Inhibitor (HDI) trichostatin A (TSA) and the inhibitor of DNA methylation 5-aza-2'-deoxycytidine (5-azadC) on the proMMP-1 expression in the human HT1080 fibrosarcoma cell line. Real-time RT-PCR revealed that 5-azadC or 5-azadC + TSA but not TSA alone, despite global histone H4 hyperacetylation, increased proMMP-1 mRNA levels. This transcription activation was correlated with chromatin decondensation determined by nuclear texture image analysis technique. Western blot analysis of cell culture conditioned media revealed a significant increase in proMMP-1 secretion after 5-azadC or 5-azadC + TSA treatment compared to untreated cells. These results suggested that epigenetic mechanisms could be involved in proMMP-1 gene expression including chromatin supra-organization changes. Indeed, although the proMMP-1 gene promoter does not appear to contain CpG islands, its expression can be induced by the demethylating agent 5-azadC. Further experiments revealed that inhibition of protein neosynthesis by cycloheximide decreased 5-azadC-induced proMMP-1 mRNA, suggesting that epigenetically regulated intermediate molecules could be involved in proMMP-1 expression regulation in these cells.