In a systematic review and meta-analysis of 14 studies encompassing a total of 1,758 patients with solid tumours, increased iNOS expression was found to be associated with significantly worse OS [hazard ratio (HR) = 1.89; 95% confidence interval (CI): 1.57–2.28; P ≤ 0.001], cancer-specific survival (HR = 3.13; 95% CI: 1.88–5.20; P ≤ 0.001) and recurrence free survival (HR = 2.16; 95% CI: 1.29–3.62; P = 0.003). The gene discussed is NOS2; the disease is cancer.