HIF1A and cancer: Notably, as NO signaling activation was previously shown to prevent hypoxia-induced accumulation of HIF-1α (Barsoum et al., 2011), treatment with the NO donor glyceryl tri-nitrate prevented the hypoxia-induced expression of PDL1 in murine melanoma cancer cells and diminished the cells' resistance to CTL-mediated lysis, indicating the potential use of NO donors as immunotherapeutic drugs against hypoxic tumor cells.