Abstract
Membrane type-1 matrix metalloproteinase (MT1-MMP) is an activator of soluble MMP-2. The activity of both MMPs is regulated by their physiological inhibitor TIMP-2. An MT1-MMP/MMP-2/TIMP-2 axis plays a key role in the invasive behavior of many cell types. Despite its importance, epigenetic control of this pro-invasive axis is insufficiently studied, and, as a result, its modification in a rational and clinically beneficial manner is exceedingly difficult. Therefore, we performed an epigenetic analysis of the MT1-MMP, MMP-2, and TIMP-2 gene promoters in highly migratory glioblastoma cells and in low migratory breast carcinoma MCF-7 cells. We determined, for the first time, that the epigenetic control leading to the transcriptional silencing of both MMPs includes hypermethylation of the corresponding CpG regions and histone H3 lysine-27 trimethylation (H3K27me3). In turn, undermethylation of the CpG islands and low levels of histone H3 lysine-27 trimethylation are features of transcriptionally active MT1-MMP and MMP-2 genes in invasive cancer cells. Additional histone modifications we have analyzed, including H3ac and H3K4me2, are present in both transcriptionally active and inactive promoters of both MMPs. Histone H3 lysine-4 trimethylation is likely to play no significant role in regulating MT1-MMP and MMP-2. The pattern of epigenetic regulation of TIMP-2 was clearly distinct from that of MMPs and included the coordinated methylation and demethylation of the two CpG regions in the promoter. Our results suggest that the epigenetic control plays an important role in both the balanced regulation of the MT1-MMP/MMP-2/TIMP-2 axis and the invasive behavior in cancer cells.