〔Abstract〕 Objective To characterize MMP12 as a pan-cancer marker and assess its screening value as a tumor serum marker.Methods Bioinformatics tools such as GEPIA2,GSCA,cBioPortal,and GeneMANIA were used to analyze the pan-cancer features of MMP12 in TCGA datasets,including encompassing differential gene expression analysis,prognostic analysis,DNA methylation analysis,gene structural variation analysis and immune microenvironment analysis.Furthermore,serum samples we collected from patients with lung adenocarcinoma,breast invasive carcinoma,esophageal squamous cell carcinoma,stomach adenocarcinoma,liver hepatocellular carcinoma,and healthy individuals.ELISA was used to detect MMP12 expression in serum,and the screening performance was evaluated using the area under the ROC curve.Additionally,we followed up 28 ESCC patients and compared serum MMP12 levels between 19 patients with disease progression and 9 patients with stable disease.Results The pancancer feature analysis revealed a significant negative correlation between MMP12 mRNA expression and its promoter DNA methylation(P<0.05),as well as a positive correlation with gene copy number variations(P<0.05).MMP12 mRNA expression was up-regulated in 14 cancer tissues compared to normal tissues next to cancer(P<0.05) and was associated with poor prognosis of cancer patients(P<0.05).Immunocorrelation analysis showed that MMP12 was significantly associated with immunity,infiltration of stromal cells,tumor mutational burden(TMB) and microsatellite instability(MSI)(P<0.05).ROC curve analysis indicated that MMP12 could serve as a potential biomarker for screening lung adenocarcinoma,breast invasive carcinoma,esophageal squamous cell carcinoma,stomach adenocarcinoma,and liver hepatocellular carcinoma.In a 30-month follow-up study of esophageal squamous cell carcinoma patients,the expression of MMP12 was higher in the disease progression group than that in the stable group.Conclusion MMP12 serves as a potential prognostic and screening marker of pan-cancer.