CD4 and neoplasm: Based on the TIMER algorithm (Fig. 7A), we found that MMP12 expression was significantly negatively correlated with tumor purity (ρ < 0, p < 0.001) and that upregulation of MMP12 expression was associated with increased infiltration levels of five immune cell types (except CD4+ T cells) (ρ > 0, p < 0.05).