Role of Sprouty2 in prostate carcinogenesis

Abstract

Prostate cancer (PC) is the most common cancer in men. In the UK alone, there are over 30,000 men diagnosed with PC every year. Loss of SPRY2 and activation of receptor tyrosine kinases are common events in PC. However, the molecular basis of their interaction and clinical impact remains to be fully examined. SPRY2 loss may functionally synergise with aberrant cellular signalling to drive PC and to promote treatment resistant disease. Using a combination of in vitro, pre-clinical in vivo models and clinical PC, this thesis shows the impact of SPRY2 loss upon activation of the ErbB signalling system via a positive feedback regulation of the ErbB-PI3K/AKT cascade. Loss of SPRY2 resulted in hyper-activation of PI3K/AKT signalling to drive proliferation and invasion by enhanced internalisation of EGFR/HER2 and their sustained localisation and signalling at the early endosome in a PTEN-dependent manner. This involves activation of p38 MAPK by PI3K to facilitate clathrin-mediated ErbB receptor endocytosis. Furthermore, this thesis suggests a critical role of PI3K/AKT in PC whereby in vitro and in vivo inhibition of PI3K suppresses proliferation and invasion, supporting PI3K/AKT as a target for therapy particularly in patients with PTEN-haploinsufficiency, low SPRY2 and ErbB expressing tumours. In conclusion, SPRY2 is an important tumour suppressor in PC; its loss drives the PI3K/AKT pathway via functional interaction with the ErbB system