For the meta-analysis of two-category variables, there were six articles, which assessed the correlation between Ang-2 expression and NSCLC [28, 31, 41–44], our results demonstrated that Ang-2 expressions in NSCLC tissues were significantly higher than normal lung tissues (pooled OR = 5.09, 95 % CI: 3.10–8.36, p = 0.000 and I2 = 0 %; Fig. 2a). The gene discussed is ANGPT2; the disease is non-small cell lung carcinoma.