title: Inhibition of Egr-1 by siRNA in prostate carcinoma cell lines is associated with decreased expression of AP-1 and NF-κB.
abstract: Previous studies suggest that the effects of Egr-1 on tumorigenesis are critically dependent on the levels of Egr-1 and the cellular context. For this reason, we examined the effects of blocking the Egr-1 activity by a short interfering RNA (siRNA) against Egr-1 on the expression of nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) signaling in the PC-3 and LNCaP prostate carcinoma cell lines. We observed that the reduction in expression of Egr-1 in PC-3 and LNCaP cells by effects of the siRNA vector resulted in lower cell viability and increased apoptosis at 24 and 120 h after transfection. This reduced cell viability correlated well with a reduced activity of the NF-κB and AP-1 factors. We analyzed the expression and activity of these factors and found that p65 and IκB but not p50 were reduced in the siRNA-treated cells. Similarly, we found that c-Fos but not c-Jun was reduced in the siRNA treated cells. These effects were translated to reduced transcriptional activity of NF-κB over cellular inhibitor of apoptosis (cIAP) and p21 genes, as assayed by RT-PCR and of AP-1 over a luciferase reporter activated by AP-1 response elements. Egr-1 was also found to interact directly with p65 and IκB members of the NF-κB family, thereby was able to regulate directly their activity by post-transcriptional effects. These results suggest that Egr-1 may promote prostate cancer development by modulating the activity of factors NF-κB and AP-1, which are involved in cell proliferation and apoptosis.
authors: Biomedical Experimental Laboratory, Sciences Faculty, University of Tarapaca, Arica, Chile. eparra@uta.cl
authors: Eduardo
authors: E
authors: Parra
authors: Jorge
authors: J
authors: Ferreira
authors: Leonardo
authors: L
authors: Saenz
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051766:Early Growth Response Protein 1; D016328:NF-kappa B; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1