LAUSR

Purpose- BIN1 is in deleted in ~5% of all prostate cancer (PC) patients and interestingly is highly enriched in the Speckle-type POZ protein (SPOP) mutant subclass (15%) of PC. BIN1 was originally identified as a repressor of cMYC activity and our lab has shown that patients with SPOPmut;MYChigh PC have worse clinical outcomes. Our observation of BIN1 deletion in the SPOP mutant subclass leads us to hypothesize that BIN1 deletion leads to enhanced AR signaling and more aggressive PC. Experimental Procedures- We analyzed baseline protein and mRNA levels of BIN1 in 13 PC cell lines via quantitative polymerase chain reaction (qPCR) and immunoblot. To understand the role of BIN1 in PC cells, we overexpressed BIN1 and evaluated changes in cell proliferation, migration, and AR target gene expression. To elucidate the role of BIN1 in vivo prostate development, we also generated a prostate-specific knockout of BIN1 and investigated changes in prostate development and AR signaling axis over time in this mouse model. Results- Our results show that none of the 13 PC cell lines analyzed had strong protein expression at baseline, but all had detectable mRNA levels. Interestingly, the three cell lines with the highest mRNA expression were AR negative (DU-145), AR independent (LN95) or castration resistant (MDVR). We also saw a decrease in downstream AR target genes (KLK3 and NKX3.1) measured using qPCR after BIN1 overexpression in 22Rv1 cells. We further corroborated this finding by measuring KLK3 expression using a KLK3-luc reporter assay after BIN1 overexpression. BIN1 overexpression also reduced invasive activity of 22Rv1 measured using a Matrigel invasion assay system. Since BIN1 deletion was enriched in SPOP mutant PC clinical data, we evaluated changes in cell proliferation in the wildtype and mutant SPOP cell lines with and without BIN1OE and found that BIN1OEhindered growth of SPOP mutant PC cells. Analysis of the TCGA primary PC dataset illustrate that PC patients harboring BIN1 deletion had higher AR activity compared to PC patients expressing wildtype BIN1. Importantly, mice with prostate specific BIN1 deletion had larger prostate mass at 2 months of age compared to age matched controls and several mice at the 6&9 month had severely enlarged prostates. Conclusion- Our findings show for the first time that BIN1 functions as an inhibitor of the AR signaling axis and deletion of BIN1 leads to higher levels of AR signaling. We also show that BIN1 deletion in mice affects prostate development and leads to enlarged prostates. These novel findings illustrate the clinical significance of BIN1 deletion in PC patients and highlights the AR-signaling axis as a potential target for PC patients with BIN1 deletion Citation Format: Collin McColl, Darlene Skapura, Elisa Echartea, Jenny Deng, Cristian Coarfa, Salma Kaochar, Brian Simons, Aleksandra Rusin. Elucidating the effects of the Alzheimer's disease associated gene BIN1 on cancer tumorigenesis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A008.