Neuropeptide-inducible upregulation of proteasome activity precedes nuclear factor kappa B activation in androgen-independent prostate cancer cells
1 Department of Medicine, Institut Gustave Roussy, Villejuif, France
2 Department of Medical Oncology, University Hospital of Larissa, Larissa, Greece
3 Centre Pluridisciplinaire d’Oncologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
4 Department of Cytopathology, “Theagenio” Cancer Hospital, Thessaloniki, Greece
5 Institute of Molecular Biology, Genetics and Biotechnology, Biomedical Research Foundation, Academy of Athens, Athens, Greece
6 Howard Hughes Medical Institute and Department of Stem Cell and Regenerative Biology, Harvard University and Harvard Medical School, Cambridge, MA, USA
Cancer Cell International 2012, 12:31 doi:10.1186/1475-2867-12-31Published: 20 June 2012
Upregulation of nuclear factor kappa B (NFκB) activity and neuroendocrine differentiation are two mechanisms known to be involved in prostate cancer (PC) progression to castration resistance. We have observed that major components of these pathways, including NFκB, proteasome, neutral endopeptidase (NEP) and endothelin 1 (ET-1), exhibit an inverse and mirror image pattern in androgen-dependent (AD) and -independent (AI) states in vitro.
We have now investigated for evidence of a direct mechanistic connection between these pathways with the use of immunocytochemistry (ICC), western blot analysis, electrophoretic mobility shift assay (EMSA) and proteasome activity assessment.
Neuropeptide (NP) stimulation induced nuclear translocation of NFκB in a dose-dependent manner in AI cells, also evident as reduced total inhibitor κB (IκB) levels and increased DNA binding in EMSA. These effects were preceded by increased 20 S proteasome activity at lower doses and at earlier times and were at least partially reversed under conditions of NP deprivation induced by specific NP receptor inhibitors, as well as NFκB, IκB kinase (IKK) and proteasome inhibitors. AD cells showed no appreciable nuclear translocation upon NP stimulation, with less intense DNA binding signal on EMSA.
Our results support evidence for a direct mechanistic connection between the NPs and NFκB/proteasome signaling pathways, with a distinct NP-induced profile in the more aggressive AI cancer state.