SEMINAR: Secreted Frizzled-Related Protein 4: An Angiogenesis Inhibitor

The Speaker: Professor Arun Dharmarajan is a Winthrop Professor and Associate Dean (South Asia Research Initiatives) and has the responsibility of teaching and research in the School of Anatomy and Human Biology. As Associate Dean for South Asia Research Initiative, Professor Dharmarajan’s primary role is to establish strong research links with Universities and Research Institutes in India. He has already established excellent research links with many universities and research institutes throughout India. Prior to his appointment with UWA, Professor Dharmarajan was at Johns Hopkins University, Baltimore, USA (1986-1994). Professor Dharmarajan has conducted an active research program in the area of apoptosis and cell signalling since taking up a position in the department (now School) of Anatomy and Human Biology. His international standing as a scientist is evidenced by his publication record, his experience as a student supervisor and mentor, his extensive collaborations both overseas and within Australia, and his invited attendance at over 75 international/national meetings. Professor Dharmarajan and has published over refereed 100 papers/reviews and book chapters. He has supervised more than 80 Hons, M.Sc and PhD students. In addition to his studies on apoptosis of the corpus luteum, which included studies of ceramide and sphingosine signalling in TNF-alpha-induced apoptosis, his research more recently has focussed on cancer biology. He and his colleagues were the first to show a role for secreted frizzled related protein-4 (sFRP4) in ovarian, breast, prostate and mesothelioma cancers and proposed an application for this protein as an early diagnostic. Preliminary research has been carried out into its effects on endothelial cell function, migration and in vitro wound healing. Methods are currently being devised to identify the active fragment of sFRP4, together with its signalling pathway, to develop a tumour-specific regimen for sFRP4 either acting alone or in combination with other anti-tumour drugs in an in vivo setting. More recently he has discovered a novel anti-angiogenic protein which also has important clinical implications in cancer diagnosis and treatment (Am J Pathology; March Issue). Australia, US and India patents have been approved based on this discovery. He has also in the past few years expanded his interests to include placental apoptosis.

The Seminar: Wnt signalling is involved in developmental processes, cell proliferation and cell migration. We have previously shown anti-proliferative and pro-apoptotic roles for the secreted frizzled protein 4 (sFRP4), a Wnt antagonist, during normal homeostasis in tissues such as ovary, corpus luteum, placenta and mammary gland as well as pathological states such as mesothelioma and colorectal carcinoma. To date there is no published data demonstrating the involvement of sFRP4 in angiogenesis. We utilized a variety of in vitro assays to examine the role of sFRP4 on endothelial cell functions such as cell migration, cell proliferation and tube formation. We also investigated the role of reactive oxygen species as a possible mediator for the apoptotic effect of sFRP4 on endothelial cells. Finally, we investigated the action of sFRP4 in vivo using the Chorioallantoic membrane and subdermal implant assays. We also investigated the effect of sFRP4 action in tumour-associated angiogenesis using a nude mouse model. Results from these studies demonstrated that endothelial cell migration, ring formation and ring stability are inhibited by antagonizing both the canonical Wnt/beta-catenin and non-canonical Wnt signalling pathways. sFRP4 also induces apoptotic events in endothelial cells in vitro by increasing cellular levels of reactive oxygen species, while tumour cells are unaffected. Furthermore, the addition of LiCl did not affect the ability of sFRP4 to antagonize endothelial cell migration in vitro. Importantly, sFRP4 restricts tumour growth in vivo by specifically interfering with endothelial cell function and markedly reducing the degree of angiogenesis to 40% of control levels. These novel findings identify sFRP4 as a, so far unexplored, potent angiogenesis inhibitor which deserves further investigation.