Analysis of cell signalling pathways involved in stromal expression of metalloproteinases and their inhibitors in cancer

Kostas Lazaridis and Clara Sampieri

Dysregulated expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) is associated with pathogenesis of cancer. Malignant tumours are characterized by elevated expression of several MMPs and TIMPs, and frequently this represents induced expression in recruited host stromal cells such as fibroblasts, inflammatory cells, myofibroblasts, macrophages and endothelial cells, rather than the tumour cells themselves, indicating the importance of tumour-stromal interactions. Additionally some MMPs/TIMPs are predominantly expressed by cancer cells or are restricted to certain cancers. Our interests lie in dissecting the signalling pathways involved in the regulation of MMP and TIMP expression in fibroblastic cells.

TGF-ß is a major regulator of MMP and TIMP expression, and aberrant TGF-ß signalling is involved in pathological conditions such as cancer and fibrosis in a variety of tissues. We have used TaqMan technology (quantitative real-time PCR) to profile MMP and TIMP expression, and determine their responsiveness to TGF-ß and PMA (a potent tumour promoter). Further characterisation has showed that different genes require differential input from the Smad and MAPK pathways following TGF-ß stimulation. Moreover, data using a broad spectre of proteins synthesis inhibitors such as anisomycin, emetine, cycloheximide and puromycin revealed a varied requirement for protein synthesis in response to PMA.

The crosstalk between the various signalling cascades and the use of different signal transducers, allows for fine tuning of gene expression by external stimuli and the elucidation of the pathways involved is essential. Future studies will focus on the characterisation of the role the different members of the MAPK family play in controlling MMP and TIMP expression, especially in the context of tumour-stromal interactions.