Regulation of cancer cell growth involves activation of genes (oncogenes) that promote cell division and survival, and the inactivation of other genes (tumour suppressors) that negatively regulate these critical cellular processes. The major focus of this project is to evaluate the role of tumour suppressor known as PTEN in the induction of breast cancer. The first specific objective is to investigate whether activation of signalling molecules that are inhibited by PTEN will accelerate tumour progression. The second objective is to directly establish whether these PTEN coupled pathways are involved in conferring resistance to therapeutic antibodies. The results of these studies will have an important impact in understanding the molecular basis of this poorly understood and prevalent disease.