003.Expression of secreted frizzled related protein-4 (sFRP-4) and associated Wnt signalling in cancer and apoptosis

Abstract

We examined the interplay between Wnt and secreted frizzled related protein-4 (sFRP4) in estradiol induced cell growth in breast cancer cells (MCF-7), and also determined the in vivo distribution of sFRP-4 in human breast cancer. MCF-7 cells were treated with estradiol, sFRP-4 conditioned media and a combination of the two. Real-time RT-PCR and Western blot analysis were used to determine the expression of the sFRP-4 and its associated Wnt signalling molecules following treatment. Immunohistochemistry was performed to examine sFRP-4 expression patterns in human breast cancers. Estradiol treatment up-regulated the expression of the Wnt signalling genes Wnt-10b, beta-catenin and fz-4 (P < 0.001 for all genes). This up-regulation was not associated with an increase in the Wnt signalling pathway as measured by the levels of active beta-catenin. sFRP-4 conditioned media reduced MCF-7 cell proliferation, down-regulated the Wnt signalling genes beta-catenin and fz-4 as well as down-regulating wnt signalling activity. sFRP-4 was able to reduce the proliferation of estradiol stimulated MCF-7 cells. Cytoplasmic sFRP-4 protein was expressed in all breast tumours examined, with intense staining evident in the lobular carcinoma in situ and the ductal carcinoma. These data demonstrate that sFRP-4 is a potent inhibitor of the Wnt signalling pathway in MCF-7 cells, acting not only to down-regulate the activity of the wnt signalling pathway, but also down-regulate the transcription of Wnt signalling genes. The results of these in vitro and immunohistochemical experiments warrant further investigation as to whether sFRP-4 expression can be indicative of prognosis in human breast cancer. In addition to breast cancer, we have also examined the role of sFRP-4 in other cancers such as ovarian and prostate.