Background

Kidney renal clear cell carcinoma (KIRC) is the most common and aggressive malignant subtype of renal cell carcinoma that has a poor prognosis and high mortality in an advanced stage due to the lack of useful biomarkers and treatments [1]. Currently, there is a multitude of established treatments for KIRC, such as surgical resection, nonspecific immune approach, targeted therapy against vascular endothelial growth factor, and novel immunotherapy agents. Despite these treatments, about 50% of KIRC patients develop metastases, and the 5-year survival rate of these patients is still lower than 10% [2]. At present, the commonly used clinical prognostic markers of KIRC include the pathological grade system and tumor node metastasis (TNM) stage, microvascular invasion, tumor necrosis, and invasion of the collecting system [3]. These clinicopathological risk factors exhibit valuable but insufficient prediction of prognosis and estimation for subsets of KIRC patients. Previous researches have established some prognostic models and nomograms that incorporate necrosis, blood tests such as lactate dehydrogenase, hemoglobin, platelets, and calcium levels, prior nephrectomy, symptoms, and performance status [https://www.gencodegenes.org/). Then, the gene symbols were annotated based on the Homo_sapiens.GRCh38.84.chr.gtf file, which was downloaded from the Ensembl database (https://asia.ensembl.org/index.html).

Identification of differentially expressed genes (DEGs)

We compared the KIRC samples and adjacent normal samples to identify DEGs by using DESeq 2 R package (Version 1.27.19; http://www.bioconductor.org/packages/devel/bioc/html/DESeq2.html) with a rigorous threshold as |log2-fold change (FC)| > 2.0 and FDR < 0.01 [21]. Then a heat map and volcano plot were drawn by using the heatmap R package (Version 1.0.1; https://www.rdocumentation.org/packages/pheatmap) and ggpubr R package (Version 0.2.4; https://www.rdocumentation.org/packages/ggpubr) in R software (Version 3.6.0; https://www.r-project.org/), to visualize the hierarchical clustering analysis of the identified DEGs.

Construction of the ceRNA network

The lncATLAS database (http://lncatlas.crg.eu/) was used to identify the DElncRNAs located in the cytoplasm [22]. Then the DEmiRNAs which potentially interacted with DElncRNAs located in the cytoplasm were predicted using the miRcode (http://www.mircode.org/), a comprehensive searchable map of putative microRNA target sites in the long noncoding transcriptome [23]. Subsequently, the target DEmRNAs of DEmiRNA were predicted using miRDB (http://mirdb.org/), miRTarBase (http://mirtarbase.mbc.nctu.edu.tw/php/index.php) and TargetScan (http://www.targetscan.org/vert_72/) databases [24,25,26]. After that, Cytoscape software (Version 3.7.2; http://www.cytoscape.org/) was utilized to visualize and construct the ceRNA network [27].

Functional enrichment analysis

The pathway and functional enrichment analysis were carried out by utilizing KO-Based Annotation System (KOBAS) (Version 3.0; http://kobas.cbi.pku.edu.cn/) and the Database for Annotation, Visualization and Integrated Discovery (DAVID) (Version: 6.8; https://david.ncifcrf.gov/), to investigate the potential biological implications of the ceRNA network [

Conclusions

In conclusion, we successfully constructed a novel ceRNA regulatory network, which narrowed the scope of predicting prognostic biomarkers and therapeutic targets for KIRC. Besides, we identified and validated an LPM which is based on three lncRNAs involved in the ceRNA network, and it has independent and great prognostic value for KIRC patients.