The effects of reactive species on the tumorigenic phenotype of human head and neck squamous cell carcinoma (HNSCC) cells.

Sustained inflammation up-regulates the reactive species (RS) generating enzymes inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). While clinical data show that levels of iNOS and COX-2 are increased in epithelium during the transformation of dysplasia to overt head and neck squamous cell carcinoma (HNSCC), the mechanisms by which their overexpression contributes to HNSCC development have not been completely delineated. This study assessed the effects of RS on parameters associated with the HNSCC tumorigenic phenotype inclusive of activation of NF-kappaB (in situ immunostaining and reporter assay) and production of proinflammatory and proangiogenic proteins (ELISA analyses). Our data, which show both reactive oxygen and nitrogen species activated NF-kappaB, and that all RS donors evaluated increased HNSCC cellular production of vascular endothelial growth factor, IL-8 and epidermal growth factor receptor proteins, imply inflammation associated RS promote HNSCC by their abilities to modulate intracellular signaling and affect gene expression.

Implications for oxidative and nitrative stress in the pathogenesis of AIDS-related Kaposi's sarcoma.

AIDS-related Kaposi's sarcoma (AIDS-KS), which is the most prevalent AIDS related cancer, arises in a unique environment characterized by profound immunosuppression in conjunction with sustained immunostimulation. Persistent inflammation and the accompanying increased production of reactive species can promote carcinogenesis by numerous routes including sustained cell proliferation, initiation of nuclear and mitochondrial DNA mutations and induction of a proangiogenic environment. Furthermore, during conditions of continuous inflammation, protein nitration can result in irreversible inactivation of enzymes including the cytoprotective and reactive species degrading enzyme, mitochondrial superoxide dismutase (MnSOD). Because MnSOD serves as a putative tumor suppressor gene in addition to its reactive species inactivating capacities, the loss of MnSOD's cytoprotective functions could markedly facilitate malignant transformation. The purpose of this study was to investigate biochemical and molecular pathways by which reactive species facilitate AIDS-KS pathogenesis. Immunohistochemical studies of AIDS-KS tumors showed intense AIDS-KS lesional cell staining for MnSOD, inducible nitric oxide synthase (NOS 2) and the presence of a cellular 'fingerprint' of nitrative stress, 3-nitrotyrosine. Collectively, these results that imply reactive species stress occurs in situ. Similarly, cultured AIDS-KS cells derived from the AIDS-KS tumors contained both MnSOD protein and the 'high output' isoform, NOS 2. Co-localization studies established that the mitochondria are a primary site for 3-nitrotyrosine localization and immunoprecipitation/immunoblotting experiments confirmed that MnSOD tyrosine nitration occurs in AIDS-KS cells. Functional SOD assays showed that AIDS-KS cells possess significantly lower MnSOD activity relative to matched control cells; findings which correspond with ongoing MnSOD tyrosine nitration and subsequent inactivation within AIDS-KS cells. These results, which show in situ evidence of reactive species stress within AIDS-KS tumors and functional deficits attributable to nitrative stress in tumor-derived AIDS-KS lesional cells, imply that reactive species are intimately associated with AIDS-KS pathogenesis and provide insights for development of novel strategies for AIDS-KS clinical treatments.

AIDS-related Kaposi's sarcoma cells rapidly internalize endostatin, which co-localizes to tropomysin microfilaments and inhibits cytokine-mediated migration and invasion.

AIDS-related Kaposi's sarcoma (KS) is the most common HIV-related malignancy. In some respects, KS is analogous to other angioproliferative diseases, in that KS lesions are highly vascularized and promoted by inflammatory cytokines. However, unlike other cancers or inflammatory mediated vascular diseases, KS is unique in that the KS lesional cells both express and respond to the complete angiogenic cytokines vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Therefore, the angiogenic phenotype, which is crucial for cancer progression, is inherent to KS tumor cells. Due to the recognized importance of angiogenesis in cancer progression, numerous angiostatic agents are being investigated as potential therapeutic agents. One such agent is endostatin, which is a 20-kDa carboxyl-terminal fragment of collagen XVIII that has demonstrated potent angiostatic activities at both the in vivo and in vitro levels. Since endostatin is recognized as a potent angiostatic agent, the majority of in vitro endostatin studies have evaluated its effects on endothelial cells. Although KS cells are speculated to arise from endothelial cell precursors and KS lesions are highly vascularized, no previous studies have investigated endostatin-KS cell interactions. This present study evaluated endostatin's effects on KS tumor cell: (i) signal transduction (endostatin internalization and transcription factor activation), and (ii) migration and invasion (functional activity assays and tropomysin co-localization). Our results show that KS cells rapidly internalize endostatin and that endostatin initiates activation of the transcription activating factors nuclear factor-kappaB (NF-kappaB) and activating protein 1 (AP-1). Our data also show that internalized endostatin co-localizes to tropomysin microfilaments and acts to inhibit KS cell migration and invasion in response to the clinically relevant angiogenic cytokines VEGF and bFGF. As a consequence of its combined angiostatic and antitumorigenic activities, endostatin could provide dual therapeutic benefits for patients with mucocutaneous KS.