RESUMEN
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.
Asunto(s)
Herpesvirus Humano 8/metabolismo , Metaloproteinasa 2 de la Matriz/biosíntesis , Receptores Acoplados a Proteínas G/metabolismo , Sarcoma de Kaposi/irrigación sanguínea , Animales , Carcinogénesis , Transformación Celular Neoplásica/genética , Células Endoteliales/metabolismo , Proteínas de Unión al GTP/genética , Herpesvirus Humano 8/genética , Sistema de Señalización de MAP Quinasas , Metaloproteinasa 2 de la Matriz/genética , Metaloproteinasa 2 de la Matriz/metabolismo , Ratones , Ratones Desnudos , Células 3T3 NIH , Neovascularización Patológica/metabolismo , Neovascularización Patológica/patología , Neovascularización Patológica/virología , Oncogenes , Receptores Acoplados a Proteínas G/genética , Sarcoma de Kaposi/metabolismo , Sarcoma de Kaposi/patología , Sarcoma de Kaposi/virología , Transducción de Señal , Activación TranscripcionalRESUMEN
Regional lymph nodes are important in the generation of tumor-directed immune responses. The relationship between nitric oxide synthase (NOS) expression and the biological behavior of tumor-draining lymph node (TDLNs) cells in vivo was determined using a spontaneously arising BALB/c mammary adenocarcinoma S13. We first demonstrated a reduction of tumor size and tumor-induced angiogenesis by blocking NOS activity in vivo. TDLNs harvested from tumor-bearing mice (TBM) on day 16 after tumor implant, showed enhanced NOS activity and NOS expression compared to control nodes. Identification of the NOS isoforms present in TDLNs resulted in expression of neuronal NOS (nNOS), endothelial NOS (eNOS) and absence of inducible NOS (iNOS). TDLN cells admixed with tumor cells and inoculated into normal mice (Winn assay) induced a reduction of tumor growth although, when inoculated alone, were able to induce the formation of new blood vessels (angiogenesis). Our data indicate that the in vivo antitumor activity of TDLN cells is modulated by a balance between angiogenesis and antitumor effectors. In our model, when trafficking of leukocytes is obviated, the control of tumor growth by TDLN cells can be explained in part by an antitumor activity great enough to exceed the angiogenic component elicited by the same cells, leading to a reduction of tumor size.