Induction of endothelial nitric oxide synthase expression by melanoma sensitizes endothelial cells to tumor necrosis factor-driven cytotoxicity.
OBJECTIVE
The cascade of molecular events leading to tumor necrosis factor (TNF)-mediated tumor regression is still incompletely elucidated. We investigated the role of endothelial nitric oxide synthase in determining the tumor-selective activity of TNF.


METHODS
Using quantitative real-time PCR, endothelial nitric oxide synthase gene levels were measured in melanoma metastases of the skin and normal skin biopsies obtained from 12 patients before undergoing TNF-based therapy. In vitro, the ability of melanoma cells supernatant to affect endothelial nitric oxide synthase transcription by endothelial cells and the influence of nitric oxide synthase inhibition on TNF cytotoxicity toward endothelial cells was evaluated.


RESULTS
Endothelial nitric oxide synthase transcript abundance resulted significantly greater in tumor samples rather than in normal skin samples and in patients showing complete response to TNF-based treatment rather than in those showing partial/minimal response. In vitro, melanoma cells' supernatant induced endothelial nitric oxide synthase gene expression by endothelial cells. Nitric oxide synthase inhibition slowed endothelial cells proliferation and, if induced before TNF administration, decreased the cytokine-mediated cytotoxicity on endothelial cells.


CONCLUSIONS
Taken together, these findings support the hypothesis that high expression of endothelial nitric oxide synthase in the tumor microenvironment might increase or be a marker for endothelial cells sensitivity to TNF. These observations may have important prognostic and/or therapeutic implications in the clinical setting.
Mocellin
Simone
S
Department of Oncological and Surgical Sciences, University of Padova, Padova, Italy. mocellins@hotmail.com
Provenzano
Maurizio
M
Rossi
Carlo Riccardo
CR
Pilati
Pierluigi
P
Scalerta
Romano
R
Lise
Mario
M
Nitti
Donato
D
D001706:Biopsy; D018929:Cell Culture Techniques; D042783:Endothelial Cells; D020869:Gene Expression Profiling; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D009362:Neoplasm Metastasis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052250:Nitric Oxide Synthase Type III; D016133:Polymerase Chain Reaction; D011379:Prognosis; D012878:Skin Neoplasms / Q000235:genetics / Q000473:pathology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D014409:Tumor Necrosis Factor-alpha; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III