Connective tissue growth factor (CTGF) is a member of an emerging CCN gene family that is implicated in various diseases associated with fibro-proliferative disorder including scleroderma and atherosclerosis. The function of CTGF in human cancer is largely unknown. We now show that CTGF induces apoptosis in the human breast cancer cell line MCF-7. CTGF mRNA was completely absent in MCF-7 but strongly induced by treatment with transforming growth factor †(TGF-â€). TGF-†by itself induced apoptosis in MCF-7, and this effect was reversed by co-treatment with CTGF antisense oligonucleotide. Overexpression of CTGF gene in transiently transfected MCF-7 cells significantly augmented apoptosis. Moreover, recombinant CTGF protein significantly enhanced apoptosis in MCF-7 cells as evaluated by DNA fragmentation, Tdt-mediated dUTP biotin nick end-labeling staining, flow cytometry analysis, and nuclear staining using Hoechst 33258. Finally, recombinant CTGF showed no effect on Bax protein expression but significantly reduced Bcl2 protein expression. Taken together, these results suggest that CTGF is a major inducer of apoptosis in the human breast cancer cell line MCF-7 and that TGF-â€-induced apoptosis in MCF-7 cells is mediated, in part, by CTGF.
Connective tissue growth factor (CTGF)1 is a member of an emerging gene family known as the CCN family (1), which includes CTGF (also known as fisp-12), CYR61(cysteine-rich 61/CEF10), Nov (nephroblastoma overexpressed) and the newly discovered WISP1/elm1, WISP2/rCop1, and WISP3 (2-5). CTGF was originally identified in conditioned medium of human umbilical vein endothelial cells (6) and plays a role in various human diseases including systemic scleroderma (7), atherosclerosis (8), renal diseases (9), hepatic fibrosis in biliary atresia (10), and malignant melanoma (11). A common finding in most of these diseases was a high level expression of CTGF in fibro-proliferative areas of affected tissues. In most cases, a direct correlation between high level CTGF expression and high levels of transforming growth factor-†(TGF-â€) expression could be established. In fact, CTGF gene expression has been shown to be regulated by TGF-†(2).TGF-†is a pleiotropic growth modulator with a wide variety of activities on different cell types. TGF-†stimulates proliferation of mesenchymal cells but inhibits that of endothelial (12) and epithelial cells (13). TGF-†is also known to inhibit the proliferation of a variety of cancer cell lines including the human breast cancer cell line 15). In fact, the anticancer effect of tamoxifen has been attributed to indirect activation of TGF-†pathway and induction of apoptosis by TGF-†(16). Because CTGF is thought to be a mediator of TGF-†action, it is conceivable that CTGF may also inhibit cancer cell proliferation by inducing apoptosis in these cells. In the present study, we utilized antisense technology, transient overexpression techniques, and recombinant CTGF protein to gain insight into the biological function of CTGF in the MCF-7 breast cancer cell line...