RESUMO
Peroxiredoxin 1 (Prx1) is an antioxidant and molecular chaperone that can be secreted from tumor cells. Prx1 is overexpressed in many cancers, and elevation of Prx1 is associated with poor clinical outcome. In the current study, we demonstrate that incubation of Prx1 with thioglycollate-elicited murine macrophages or immature bone marrow-derived dendritic cells resulted in TLR4-dependent secretion of TNF-alpha and IL-6 and dendritic cell maturation. Optimal secretion of cytokines in response to Prx1 was dependent upon serum and required CD14 and MD2. Binding of Prx1 to thioglycollate macrophages occurred within minutes and resulted in TLR4 endocytosis. Prx1 interaction with TLR4 was independent of its peroxidase activity and appeared to be dependent on its chaperone activity and ability to form decamers. Cytokine expression occurred via the TLR-MyD88 signaling pathway, which resulted in nuclear translocation and activation of NF-kappaB. These findings suggest that Prx1 may act as danger signal similar to other TLR4-binding chaperone molecules such as HSP72.
Assuntos
Citocinas/metabolismo , Mediadores da Inflamação/metabolismo , Peroxirredoxinas/fisiologia , Receptor 4 Toll-Like/metabolismo , Animais , Células Cultivadas , Células Dendríticas/metabolismo , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos , Chaperonas Moleculares , NF-kappa B/metabolismo , Peroxirredoxinas/imunologia , Peroxirredoxinas/metabolismo , Ligação Proteica , Multimerização Proteica , Transdução de SinaisRESUMO
Chronic inflammation leads to the formation of a pro-tumorigenic microenvironment that can promote tumor development, growth and differentiation through augmentation of tumor angiogenesis. Prostate cancer (CaP) risk and prognosis are adversely correlated with a number of inflammatory and angiogenic mediators, including Toll-like receptors (TLRs), NF-κB and vascular endothelial growth factor (VEGF). Peroxiredoxin 1 (Prx1) was recently identified as an endogenous ligand for TLR4 that is secreted from CaP cells and promotes inflammation. Inhibition of Prx1 by CaP cells resulted in reduced expression of VEGF, diminished tumor vasculature and retarded tumor growth. The mechanism by which Prx1 regulates VEGF expression in normoxic conditions was investigated in the current study. Our results show that incubation of mouse vascular endothelial cells with recombinant Prx1 caused increases in VEGF expression that was dependent upon TLR4 and required hypoxia inducible factor-1 (HIF-1) interaction with the VEGF promoter. The induction of VEGF was also dependent upon NF-κB; however, NF-κB interaction with the VEGF promoter was not required for Prx1 induction of VEGF suggesting that NF-κB was acting indirectly to induce VEGF expression. The results presented here show that Prx1 stimulation increased NF-κB interaction with the HIF-1α promoter, leading to enhanced promoter activity and increases in HIF-1α mRNA levels, as well as augmented HIF-1 activity that resulted in VEGF expression. Prx1 induced HIF-1 also promoted NF-κB activity, suggesting the presence of a positive feedback loop that has the potential to perpetuate Prx1 induction of angiogenesis. Strikingly, inhibition of Prx1 expression in CaP was accompanied with reduced expression of HIF-1α. The combined findings of the current study and our previous study suggest that Prx1 interaction with TLR4 promotes CaP growth potentially through chronic activation of tumor angiogenesis.
Assuntos
Endotélio Vascular/metabolismo , Proteínas de Homeodomínio/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , NF-kappa B/genética , Neoplasias da Próstata/irrigação sanguínea , Receptor 4 Toll-Like/genética , Fator A de Crescimento do Endotélio Vascular/genética , Animais , Linhagem Celular Tumoral , Endotélio Vascular/imunologia , Endotélio Vascular/patologia , Regulação da Expressão Gênica , Proteínas de Homeodomínio/antagonistas & inibidores , Proteínas de Homeodomínio/imunologia , Proteínas de Homeodomínio/farmacologia , Células Endoteliais da Veia Umbilical Humana , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/imunologia , Masculino , Camundongos , Camundongos SCID , NF-kappa B/imunologia , Transplante de Neoplasias , Neovascularização Patológica , Regiões Promotoras Genéticas , Neoplasias da Próstata/genética , Neoplasias da Próstata/imunologia , Neoplasias da Próstata/patologia , Ligação Proteica , RNA Interferente Pequeno/genética , Transdução de Sinais , Receptor 4 Toll-Like/imunologia , Fator A de Crescimento do Endotélio Vascular/imunologiaRESUMO
In recent years a number of studies have implicated chronic inflammation in prostate carcinogenesis. However, mitigating factors of inflammation in the prostate are virtually unknown. Toll-like receptor 4 (TLR4) activity is associated with inflammation and is correlated with progression risk in prostate cancer (CaP). TLR4 ligands include bacterial cell wall proteins, danger signaling proteins, and intracellular proteins such as heat shock proteins and peroxiredoxin 1 (Prx1). Here we show that Prx1 is overexpressed in human CaP specimens and that it regulates prostate tumor growth through TLR4-dependent regulation of prostate tumor vasculature. Inhibiting Prx1 expression in prostate tumor cells reduced tumor vascular formation and function. Furthermore, Prx1 inhibition reduced levels of angiogenic proteins such as VEGF within the tumor microenvironment. Lastly, Prx1-stimulated endothelial cell proliferation, migration, and differentiation in a TLR4- and VEGF-dependent manner. Taken together, these results implicate Prx1 as a tumor-derived inducer of inflammation, providing a mechanistic link between inflammation and TLR4 in prostate carcinogenesis. Our findings implicate Prx1 as a novel therapeutic target for CaP.