MMP2 and lung cancer: As early as 2002, Yu et al. discovered in their case–control research that MMP-2 rs243865 was associated with a higher lung cancer (LC) susceptibility (odds ratio (OR) = 2.15, 95% CI = 1.70–2.71, p < 0.05) in Asian populations (15); however, in 2019, Chen et al. reported in their case–control research in the Asian populations that MMP-2 rs243865 reduced LC susceptibility (OR = 0.54, 95% CI = 0.41–0.72, p < 0.05) (16).