Prognostic value and immune infiltration of a novel stromal/immune score-related P2RY12 in lung adenocarcinoma microenvironment

Abstract

Objective: Increasing evidence highlights the clinical implications of P2RY12 that belongs to the family of G-protein coupled receptors in carcinogenesis. Here, this study was designed to explore the associations between P2RY12 and tumor immune microenvironment of lung adenocarcinoma (LUAD).

Methods: Based on 352 LUAD samples from The Cancer Genome Atlas (TCGA), stromal and immune scores of each sample were estimated by ESTIMATE algorithm. Differential expression analysis was presented between stromal/immune high- and low-score groups. Protein-protein interaction (PPI) was then constructed by STRING database. Univariate and multivariate Cox regression analysis was utilized to screen prognosis-related factors. Co-expressed genes of P2RY12 were analyzed, followed by functional enrichment analysis. Furthermore, the correlation between P2RY12 and immune cell infiltrations was estimated using the TIMER database. P2RY12 expression was validated between 37 pairs of LUAD and normal tissues using RT-qPCR and immunohistochemistry. After overexpressing P2RY12, the proliferation and migration of A549 cells was detected by CCK-8 and scratch test.

Results: 145 up- and 102 down-regulated stromal- and immune-related mRNAs were identified for LUAD. Based on 145 up-regulated mRNAs, a PPI network was conducted, consisting of 95 nodes and 210 relationship pairs. Ten hub genes were then identified. Among them, CCR8, CNR2, CXCR5, GPR18, GPR31 and P2RY12 were in association with overall survival of patients with LUAD. After adjusting other variables, P2RY12 expression was an independent prognostic factor for LUAD. 288 co-expressed genes of P2RY12 were determined and these co-expressed genes were primarily involved in immune-related biological processes or pathways. Moreover, P2RY12 was significantly correlated with M2 macrophage and dendritic cell infiltration. After validation, P2RY12 expression was significantly decreased in LUAD than normal tissues. Its overexpression distinctly suppressed proliferation and migration of A549 cells.

Conclusion: Our findings suggest that P2RY12 is an immune infiltration-related prognostic marker for LUAD.

Keywords: Immune cells; Lung adenocarcinoma; P2RY12; Stromal cells; Tumor microenvironment.