SPP1 Might Be a Novel Prognostic Biomarker for Patients With Malignancy: a Meta-analysis and Sequential Verification Based on Bioinformatic Analysis

Abstract Background: Several studies have investigated the relationship between secreted phosphoprotein 1 (SPP1) expression level and prognosis of various tumors, but the results are far from conclusive. Therefore, we performed the present meta-analysis to investigate the prognostic value of SPP1 in pan-cancer. Furthermore, a followed confirmation based on The Cancer Genome Atlas (TCGA) database was also performed to verify our results. Methods: We performed a systematic search from PubMed, Embase, Web of Science, and Cochrane Library databases and 19 articles, including 3403 patients and 9 types of tumors, were pooled in our meta-analysis. Overall survival (OS) and disease-free survival (DFS), which correlated with SPP1 expression, were considered as the primary outcome. Subgroup analyses, sensitivity analysis, and publication bias were used to investigate heterogeneity and reliability of the results. Furthermore, we also explored the relationship between SPP1 expression and clinical parameters of tumor patients. Finally, the results were verified with TCGA database and we further explored the relationship between SPP1 expression and tumor immuno-microenvironment (TIME), DNA methylation, and enriched gene pathway. Results: Our meta-analysis showed that high-expressed SPP1 was significantly related to poor OS and DFS in various cancers, especially in liver hepatocellular carcinoma (LIHC). Furthermore, we also identified that the high expression level of SPP1 was significantly correlated with tumor grade. The expression level of SPP1 in the majority of tumor types were much higher than the corresponding normal tissues analyzed from databases. Besides, we also observed that high-expressed SPP1 was related to poor OS and DFS in LIHC, which supported the conclusion of meta-analysis. In addition, high-expressed SPP1 is related to 6 immune cells in TIME and DNA methylation regulatory genes. Ultimately, the results of Gene Set Enrichment Analysis (GSEA) suggested that tumor-related gene sets, such as hypoxia and lipid metabolism, were significantly enriched in high-expressed SPP1 group. Conclusions: SPP1 is high-expressed in various tumor tissues and correlated with poor prognosis. SPP1 might promote cancer invasion and metastasis by affecting tumor grade, TIME, DNA methylation, hypoxia, and lipid metabolism. SPP1 is expected to become a new clinical indicator for tumor detection and prognosis, and provide a new idea for tumor targeted therapy.