iNOS is a key mediator of anti-PD-1 melanoma therapy response.
Inducible nitric oxide synthase (iNOS) and its product nitric oxide (NO) were historically linked to poor melanoma outcomes, yet recent evidence shows NO supports anti-tumor immunity. This study examines how iNOS shapes anti-PD-1 efficacy, particularly through interferon signaling.
B16-D5 melanoma tumors were implanted in wild-type (WT) and iNOS knockout (KO) mice to compare tumor growth and response to anti-PD-1 therapy. Flow cytometry, apoptosis assays, and RNA sequencing assessed NO production, PD-L1 expression, and interferon-related gene activation. In vitro, melanoma cells were treated with NO donors (DETA NONOate, SNAP) to assess proliferation and apoptosis. Peripheral blood mononuclear cells from 27 melanoma patients receiving anti-PD-1 therapy were analyzed with multiparameter flow cytometry to correlate NO-associated immune subsets with progression-free survival (PFS).
Tumors grew significantly faster in iNOS KO mice, and anti-PD-1 therapy had no effect, demonstrating that iNOS-derived NO contributes to treatment efficacy. NO donors inhibited melanoma proliferation and induced apoptosis in vitro. Transcriptomic analysis showed anti-PD-1 upregulated interferon pathway genes (STAT1, IRF1, IFNB1) in WT but not iNOS KO mice. In patients, a NO-producing dendritic-cell subset (DAF-FM+CD11c+) was associated with improved PFS (hazard ratio 0.453; 95% CI = 0.270-0.992; p=0.048), indicating a NO-dependent enhancement of interferon-driven immune activity.
iNOS-derived NO is necessary for effective anti-PD-1 immunotherapy in melanoma, promoting interferon signaling and immune activation. Loss of iNOS impairs tumor control and immune responsiveness, supporting NO as a potential biomarker and therapeutic adjunct to be explored while challenging assumptions about its deleterious role in melanoma.
B16-D5 melanoma tumors were implanted in wild-type (WT) and iNOS knockout (KO) mice to compare tumor growth and response to anti-PD-1 therapy. Flow cytometry, apoptosis assays, and RNA sequencing assessed NO production, PD-L1 expression, and interferon-related gene activation. In vitro, melanoma cells were treated with NO donors (DETA NONOate, SNAP) to assess proliferation and apoptosis. Peripheral blood mononuclear cells from 27 melanoma patients receiving anti-PD-1 therapy were analyzed with multiparameter flow cytometry to correlate NO-associated immune subsets with progression-free survival (PFS).
Tumors grew significantly faster in iNOS KO mice, and anti-PD-1 therapy had no effect, demonstrating that iNOS-derived NO contributes to treatment efficacy. NO donors inhibited melanoma proliferation and induced apoptosis in vitro. Transcriptomic analysis showed anti-PD-1 upregulated interferon pathway genes (STAT1, IRF1, IFNB1) in WT but not iNOS KO mice. In patients, a NO-producing dendritic-cell subset (DAF-FM+CD11c+) was associated with improved PFS (hazard ratio 0.453; 95% CI = 0.270-0.992; p=0.048), indicating a NO-dependent enhancement of interferon-driven immune activity.
iNOS-derived NO is necessary for effective anti-PD-1 immunotherapy in melanoma, promoting interferon signaling and immune activation. Loss of iNOS impairs tumor control and immune responsiveness, supporting NO as a potential biomarker and therapeutic adjunct to be explored while challenging assumptions about its deleterious role in melanoma.
Authors
Nguyen Nguyen, Kim Kim, Le Le, Garg Garg, Balkaran Balkaran, Bhathivi Bhathivi, Chamizo Chamizo, Dukes Dukes, Ward Ward, Brohl Brohl, Karapetyan Karapetyan, Khushalani Khushalani, Eroglu Eroglu, Tarhini Tarhini, Mulé Mulé, Markowitz Markowitz
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