Structural proteins such as collagen, fibronectin and lam inin make up a large proportion of the ECM. However, an other group of proteins selleck chem known as matricellular proteins are also found associated with the ECM. Matricellular proteins do not play a direct role in maintaining physical structure but are rather involved in modulating and co mediating cel lular responses through interactions with cell surface recep tors, growth factors, cytokines and matrix proteins. Connective tissue growth factor or CCN2 is a member of the CCN family of matricellular proteins and mainly acts through interactions with cell adhesion recep tors such as integrins and heparin sulfate proteoglycans. CCN2 expression is regulated mainly at the transcriptional level and one of the most potent in ducers of CCN2 gene expression in fibroblasts, but not in epithelial cells, is transforming growth factor beta.

Regulation of CCN2 gene expression by TGFB in volves the association of a Smad3Smad4 complex with a Smad binding element on the CCN2 promoter. The CCN2 promoter also has a TGFB response element which appears to be important for the regula tion of basal CCN2 gene expression in fibroblasts, and is therefore also called the Inhibitors,Modulators,Libraries basal Inhibitors,Modulators,Libraries control element. Other signalling pathways that are involved in basal and TGFB mediated CCN2 up regulation include the Ras MEKERK and protein kinase C pathways. CCN2 is thought to act mainly as a co mediator of TGF Bs ability to promote type I collagen synthesis, as ccn2 embryonic fibroblasts were unable to induce type I collagen synthesis in response to TGFB.

An important relationship therefore exists between TGFB, CCN2 and type I collagen, and in aged human skin the expression of all three of these proteins is co ordinately reduced when compared to levels in younger skin samples. Current knowledge of the role tumour Inhibitors,Modulators,Libraries cells play in regu lating the expression of various components of the ECM in the tumour environment is limited. Inhibitors,Modulators,Libraries In this study we inves tigated this further by using microarray technology to measure changes in the expression of ECM components and adhesion molecules in human fibroblasts that were co cultured with human breast tumour cells. We show that MDA MB 231 breast tumour cells negatively regulate CCN2 and type I collagen gene expression in CCD 1068SK fibroblasts in a Smad7 dependent manner through decreased activation of the MEKERK signalling pathway. This effect was only observed in CCD 1068SK fibroblasts that were directly co cultured with MDA MB 231 tumour cells, suggesting Inhibitors,Modulators,Libraries that breast tumour cells require close con tact with fibroblasts in the tumour microenvironment to influence the expression of ECM 20S proteasome inhibitor components.