Prostate Specific Membrane Antigen (PSMA) associates with Filamin A, beta1 integrin, pp130CAS and pSrc thus regulating the activation of beta1 integrin and the survival of prostate cancer cells.

Prostate cancer (PCa) is the second cause of cancer-related death in males of developed countries. Up-regulated PSMA expression in aggressive prostate tumors implies a selective advantage for expressing cells and therefore a role for PSMA in cancer cell growth and progression. Previous and herein shown results demonstrate that the PSMA clustering with specific mAb at the cell surface of human prostate carcinoma LNCaP cell line activates beta1 integrin (HUTS-21 epitope), AKT/mTOR/BAD pathway and p38 and ERK1/2 MAPKs, thus promoting cell growth and cell rescue from apoptosis induced by serum deprivation. This occurs thanks to the assembly of a transduction complex including Filamin A (FLNa), beta1 integrin (beta1), phospho-p130CAS and phospho-Src, as demonstrated by cross-immuneprecipitation experiments performed by using either anti PSMA or anti beta1 mAbs. The common location of these molecules in the same Detergent Resistant Membranes (DRMs) is likely to favor their association. Immunoblottings, FACS analysis and 3D cultures demonstrated that PSMA-induced kinase activation and rescue were hampered or abrogated if FLNa or beta1 or p130CAS were silenced, or if Src was inhibited with SU6656 or PP1 drugs. It has been previously demonstrated that beta1 associates with Epidermal Growth Factor Receptor (EGFR) thereby regulating its activation state. Based on this, we questioned whether EGFR may be recruited in the signaling complex induced by PSMA activation. Our preliminary results have put into evidence EGFR in the same DRMs as PSMA and beta1. Moreover, immunoblotting of IPs prepared from cell lysate of LNCaP cells after PSMA activation, showed that PSMA and FLNa could be pulled down from EGFR IPs. In all, our results demonstrate for the first time that PSMA expression gives a remarkable advantage to PCa cells by recruiting a signaling complex, including FLNa, beta1, p130CAS, Src and EGFR, and thereby supporting the activation of antiapototic and pro-proliferative signaling pathways.