RESUMO
Kaposi's sarcoma-associated herpesvirus (KSHV) vGPCR is a constitutively active G protein-coupled receptor that subverts proliferative and inflammatory signaling pathways to induce cell transformation in Kaposi's sarcoma. Cyclooxygenase-2 (COX-2) is an inflammatory mediator that plays a key regulatory role in the activation of tumor angiogenesis. Using two different transformed mouse models and tumorigenic full KSHV genome-bearing cells, including KSHV-Bac16 based mutant system with a vGPCR deletion, we demostrate that vGPCR upregulates COX-2 expression and activity, signaling through selective MAPK cascades. We show that vGPCR expression triggers signaling pathways that upregulate COX-2 levels due to a dual effect upon both its gene promoter region and, in mature mRNA, the 3'UTR region that control mRNA stability. Both events are mediated by signaling through ERK1/2 MAPK pathway. Inhibition of COX-2 in vGPCR-transformed cells impairs vGPCR-driven angiogenesis and treatment with the COX-2-selective inhibitory drug Celecoxib produces a significant decrease in tumor growth, pointing to COX-2 activity as critical for vGPCR oncogenicity in vivo and indicating that COX-2-mediated angiogenesis could play a role in KS tumorigenesis. These results, along with the overexpression of COX-2 in KS lesions, define COX-2 as a potential target for the prevention and treatment of KSHV-oncogenesis.
Assuntos
Herpesvirus Humano 8/metabolismo , Metaloproteinase 2 da Matriz/biossíntese , Receptores Acoplados a Proteínas G/metabolismo , Sarcoma de Kaposi/irrigação sanguínea , Animais , Carcinogênese , Transformação Celular Neoplásica/genética , Células Endoteliais/metabolismo , Proteínas de Ligação ao GTP/genética , Herpesvirus Humano 8/genética , Sistema de Sinalização das MAP Quinases , Metaloproteinase 2 da Matriz/genética , Metaloproteinase 2 da Matriz/metabolismo , Camundongos , Camundongos Nus , Células NIH 3T3 , Neovascularização Patológica/metabolismo , Neovascularização Patológica/patologia , Neovascularização Patológica/virologia , Oncogenes , Receptores Acoplados a Proteínas G/genética , Sarcoma de Kaposi/metabolismo , Sarcoma de Kaposi/patologia , Sarcoma de Kaposi/virologia , Transdução de Sinais , Ativação TranscricionalRESUMO
ABSTRACT The replacement of natural grassland by cultivated areas might favor the increase in abundance of some root-feeding species such as the white grubs, which may become a constraint for field crop production. This research aimed to assay the population density and geographical distribution of white grubs pest and other species in natural grassland and cultivated areas throughout the Brazilian Pampa biome. White grubs were sampled in 18 locations in both landscape use types and identified. Population density (number of larvae m-2) was calculated for each recorded species and sorted within two groups (pest species and other species), compared between natural grasslands and cultivated areas, as well as among locations. A dendrogram to evaluate species similarity among locations was built based on combined data obtained from both landscape use types throughout the region. In total, 31 species were found in the Brazilian Pampa, and four of them are considered as crop pests: Diloboderus abderus (Sturm, 1826), Euetheola humilis (Burmeister, 1847), Lyogenys fusca (Blanchard, 1830), and Phyllophaga triticophaga Morón & Salvadori, 1998. The average population density of pest species in cultivated areas was less than five larvae m-2, at most of locations. Some species had a wide geographical distribution (e.g. D. abderus and Cyclocephala modesta Burmeister), while other melolontids occurred at only one location. The knowledge of which white grub species are present in a field and its population densities assist farmers to take proper management decisions.
RESUMO
Kaposi's sarcoma (KS), a multifocal vascular neoplasm linked to human herpesvirus-8 (HHV-8/KS-associated herpesvirus [KSHV]) infection, is the most common AIDS-associated malignancy. Clinical management of KS has proven to be challenging because of its prevalence in immunosuppressed patients and its unique vascular and inflammatory nature that is sustained by viral and host-derived paracrine-acting factors primarily released under hypoxic conditions. We show that interactions between the regulatory lectin galectin-1 (Gal-1) and specific target N-glycans link tumor hypoxia to neovascularization as part of the pathogenesis of KS. Expression of Gal-1 is found to be a hallmark of human KS but not other vascular pathologies and is directly induced by both KSHV and hypoxia. Interestingly, hypoxia induced Gal-1 through mechanisms that are independent of hypoxia-inducible factor (HIF) 1α and HIF-2α but involved reactive oxygen species-dependent activation of the transcription factor nuclear factor κB. Targeted disruption of Gal-1-N-glycan interactions eliminated hypoxia-driven angiogenesis and suppressed tumorigenesis in vivo. Therapeutic administration of a Gal-1-specific neutralizing mAb attenuated abnormal angiogenesis and promoted tumor regression in mice bearing established KS tumors. Given the active search for HIF-independent mechanisms that serve to couple tumor hypoxia to pathological angiogenesis, our findings provide novel opportunities not only for treating KS patients but also for understanding and managing a variety of solid tumors.
Assuntos
Galectina 1/metabolismo , Neovascularização Patológica/metabolismo , Polissacarídeos/metabolismo , Sarcoma de Kaposi/metabolismo , Animais , Anticorpos Monoclonais/farmacologia , Anticorpos Neutralizantes/farmacologia , Hipóxia Celular , Linhagem Celular Tumoral , Células Cultivadas , Galectina 1/genética , Galectina 1/imunologia , Regulação Neoplásica da Expressão Gênica , Células HEK293 , Herpesvirus Humano 8/fisiologia , Interações Hospedeiro-Patógeno , Humanos , Hipóxia , Immunoblotting , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Nus , Neovascularização Patológica/genética , Neovascularização Patológica/prevenção & controle , Ligação Proteica/efeitos dos fármacos , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sarcoma de Kaposi/tratamento farmacológico , Sarcoma de Kaposi/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Giardia lamblia is a medically important protozoan parasite with a basal position in the eukaryotic lineage and is an interesting model to explain the evolution of biochemical events in eukaryotic cells. G. lamblia trophozoites undergo significant changes in order to survive outside the intestine of their host by differentiating into infective cysts. In the present study, we characterize the previously identified Orf-C4 (G. lamblia open reading frame C4) gene, which is considered to be specific to G. lamblia. It encodes a 22 kDa protein that assembles into high-molecular-mass complexes during the entire life cycle of the parasite. ORF-C4 localizes to the cytoplasm of trophozoites and cysts, and forms large spherical aggregates when overexpressed. ORF-C4 overexpression and down-regulation do not affect trophozoite viability; however, differentiation into cysts is slightly delayed when the expression of ORF-C4 is down-regulated. In addition, ORF-C4 protein expression is modified under specific stress-inducing conditions. Neither orthologous proteins nor conserved domains are found in databases by conventional sequence analysis of the predicted protein. However, ORF-C4 contains a region which is similar structurally to the alpha-crystallin domain of sHsps (small heat-shock proteins). In the present study, we show the potential role of ORF-C4 as a small chaperone which is involved in the response to stress (including encystation) in G. lamblia.