CCN2 and neoplasm: Moreover, CCN2 has been shown to act as a co-mediator of TGFβ’s ability to promote type I collagen synthesis [18,25], suggesting that the decreased type I collagen gene expression observed in CCD-1068SK fibroblasts co-cultured with MDA-MB-231 tumour cells could occur as a result of the negative regulatory effect of increased Smad7 expression on CCN2 gene expression.