Identification of SPP1 as a promising biomarker to predict clinical outcome of lung adenocarcinoma individuals.

We identified and investigated the prognostic value of secreted phosphoprotein 1 (SPP1) in lung adenocarcinoma (LUAD) patients and evaluate the relationship between the SPP1 expression level and clinical characteristics. First, SPP1 was identified through four LUAD datasets in GEO database and validated by the TCGA database. Then a total of 149 lung adenocarcinoma patients were included, as well as their clinicopathological characteristics collected in the study. The expression levels of SPP1 and adjacent normal tissues were assessed by immunohistochemistry. The association between SPP1 and its prognostic value was systematically evaluated. Results showed high SPP1 level predicted poorer LUAD survival by univariate Cox analysis (P = 0.017), and the multivariate result was also significant (P = 0.021). Subgroup analysis suggested the prognostic value of SPP1 was significant in stage T1 (log rank P = 0.011), stage N0 (log rank P = 0.046) and stage N1 (log rank P = 0.009) patients. After including these markers into a nomogram, the Harrell's C-index of the nomogram was 0.694. In summary, our findings suggest that SPP1 is an independent biomarker with prognostic significance in LUAD.