Regulation of matrix metalloproteinases following cellular transformation

During progression towards malignancy, many tumor cells display changes in their repertoire of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). The recent finding that many members of the MMPs are regulated by protooncogenes may explain the frequent observation of changes in MMP gene expression during progression of many tumor types. While studies involving enzymatic assays of MMPs are usually confined to one or a few MMPs, reverse transcription-PCR (RT-PCR) permitted the analysis of seven members of the MMP family and two members of the TIMP family in several normal and transformed cell lines. RT-PCR permitted us to confirm the observation that MMP-9 is activated following transformation and also to observe the previously unreported activation of MMP-7 in SV₄₀-transformed cells. It has previously been found that MMP-1, -2, -3, -8, and -9 are upregulated by phorbol esters; we have found that MMP-10 is also upregulated by phorbol esters. The phorbol ester upregulation of MMP-1, -3, and -10 was found to be abolished in cells transformed by SV₄₀ virus. Several studies have shown that MMP-1 is upregulated by an integrin-mediated signal transduction pathway. This study demonstrates that MMP-3 and MMP-10 are also regulated by integrin-mediated signal transduction and that upregulation by this pathway is abolished following SV₄₀ transformation. In summary, the more global view of MMP expression afforded by RT-PCR indicates that MMP-1, -3, and -10 are regulated by both integrin-mediated signal transduction and phorbol esters. While fibroblasts and transformed bone cells express several members of the MMP gene family, several other cell types do not express MMPs.