LNCaP, CWR22Rv1 and VCaP cells were obtained in 2001 from the American Type Culture Collection (ATCC, Manassas, VA) and were cultured in RPMI containing 10% complete FBS and penicillin/streptomycin. ATCC uses Short Tandem Repeat (STR) profiling for testing and authentication of cell lines. C4-2B cells were kindly provided and authenticated by Dr. Leland Chung, Cedars-Sinai Medical Center, Los Angeles, CA in 2006. All experiments with these cell lines were performed within 6 months of resuscitation after cryopreservation. LNCaP cells stably expressing NF-kappaB2/p52 were generated by stable transfection of LNCaP cells with plasmids expressing NF-kappaB2/p52 as described previously (21 (link)) and were not authenticated further. 22Rv1 and C4-2B cells resistant to enzalutamide (22Rv1-Enza-R and C4-2B-Enza-R) were generated by chronic culture of 22Rv1 and C4-2B cells in enzalutamide as described previously (22 (link), 23 (link)) and were not authenticated further. Antibodies against NF-kappaB2/p52 (K-27), AR (441; mouse monoclonal), HA, Tubulin, U2AF65 and ASF/SF2 were from Santa Cruz Biotechnologies. Antibodies against splicing factors hnRNPA1 (9H10) and hnRNPA2B1 (DP3B3) were from Sigma-Aldrich and AbCam respectively. Sso Fast™ Eva Green qPCR Supermix was from Bio-Rad. All other reagents were of analytical grade and obtained from local suppliers.