Examination of CXCL12 RNA transcript levels and protein expression of CXCL12 in prostate cancer cell lines in which SLUG was knocked down by shRNA. (A, B) RNA transcript analysis of CXCL12. RNA was extracted from PC3 and DU-145 prostate cancer cell lines stably expressing Slug shRNA (Sh1 and Sh2) or control shRNA (ShRNA Ctr), and subjected to cDNA synthesis. RNA transcript level of CXCL12 and SLUG in these cell lines was analyzed by qPCR (left panel) and RT-PCR (right panel). CXCL12 expression was significantly downregulated in PC3 and DU145 cells expressing Slug shRNAs at RNA transcript level. (C) ELISA analysis of CXC12 protein level in PC3 cells expressing Slug shRNAs. Conditioned cell culture medium was collected from cell culture environments of PC3 cells infected with lentiviruses expressing control shRNA (ShRNA Ctr) and Slug-specific shRNA (Slug Sh1 and Slug Sh2), and then analyzed by ELISA. CXCL12 protein level was great significantly downregulated in PC3 cells expressing Slug shRNA.