Long Noncoding RNA AP000695.2 as a Novel Prognostic Biomarker for Gastric Cancer

Background: Long non-coding RNA (lncRNA) AP000695.2 (ENSG00000248538) expresses abnormally in various malignancies, what shows its role as oncogene. However, it has not been extensively studied in gastric cancer. The aim of the current study was to explore the clinical value of AP000695.2 to prognose gastric cancer. Methods: The cancer genome atlas (TCGA) and the gene expression profiling interactive analysis (GEPIA) online tool were used to analyze AP000695.2 expression pattern, diagnostic and prognostic role in gastric cancer. Kaplan-Meier and Cox regression analyses were used to assess survival in patients with gastric cancer. Receiver operating curve (ROC) analysis was used to assess AP000695.2 diagnostic capacity. Nomograms were created to predict overall survival (OS) and progression free survival (PFS). Results: LncRNA AP000695.2 was abnormally upregulated in 19 types of malignancy, including gastric cancer. Survival anal-ysis indicated that high expression of AP000695.2 was associated with poor survival of gastric cancer. Multivariate Cox re-gression analysis verified the independent prognostic value of AP000695.2 to predict OS (HR (hazard ratio): 1.104, 95% CI (confidence interval): 1.035-1.178, p = 0.003) and PFS (HR: 1.170, 95% CI: 1.090-1.256, p < 0.001). ROC analysis indicated a favorable AP000695.2 diagnostic capacity (area under the curve (AUC) = 0.890). Nomograms were also constructed for OS and PFS based on AP000695.2 expression-related risk score. Additionally, AP000695.2 was found to be positively associated with tumor-infiltrating immune cells, including classically activated (M1) macrophages, neutrophils, alternatively activated (M2) macrophages, and natural killer (NK) cells. Conclusions: It was observed that AP000695.2 can be used as a novel biomarker to diagnose or predict survival of gastric patient.