Pseudogene CHIAP2 inhibits proliferation and invasion of lung adenocarcinoma cells by means of the WNT pathway.

Recently, pseudogenes have emerged as critical regulators in the onset of human neoplasia. Here, we present a comprehensive analysis of pseudogene alterations at transcriptional levels in lung adenocarcinoma (LUAD) from The Cancer Genome Atlas. By combinations of differential expression analysis, survival analysis, and univariate and multivariable Cox proportional hazards regression models, we identified four dysregulated pseudogenes, whose expression level was closely related to LUAD patients' prognosis and the four pseudogene signature could act as an independent prognostic indicator for LUAD patients. We further characterized CHIAP2, one of those four pseudogenes, whose expression level was the most closely linked to LUAD patients' prognosis. Consistent with our analysis, the expression of CHIAP2 was abnormally downregulated in LUAD tissues compared with that in normal tissues in our 50 pairs of clinical samples. Functional assays demonstrated that upregulation of CHIAP2 significantly impaired cell proliferation and invasion. After performing RNA sequencing (RNA-seq) and small RNA-seq between CHIAP2 overexpression and negative control LUAD cell lines, we identified differentially expressed messenger RNAs and microRNAs (miRNAs), among which six miRNAs were downregulated. Target genes of six downregulated miRNAs were predicted with online miRNA target prediction tools and significant pathways including the WNT signal pathway were identified with Gene Set Enrichment Analysis. By combining predictor genes of six downregulated miRNAs and dysregulated genes of the WNT pathway, we inferred that overexpression of CHAP2 may inhibit LUAD cell proliferation and invasion via modulation of NFATC2 or GSK3B (WNT signal pathway) targeted by miR-3614-5p or miR-873-3p.