Establishment and validation of lncRNA-related prognostic signatures in cholangiocarcinoma

Background: The prognosis of CCA is extremely poor, making it one of the most lethal cancers. Therefore, there is a need to elucidate the pathogenic mechanisms of CCA. In this study, we aimed at identifying lncRNA-related prognostic signatures for CCA through bioinformatics analysis and further validated their functions in CCA tumorigenesis and progression. Methods: The RNA-seq data of CCA were downloaded from public databases. Differentially expressed lncRNAs (DElncRNAs) were screened. Then, candidate OS- and DFS-related DElncRNAs were selected through Kaplan-Meier survival analysis. Furthermore, LASSO regression was performed to establish the OS and DFS signatures, respectively. Multivariate COX models and nomograms for overall survival (OS) and disease-free survival (DFS) were established based on OS/DFS signature and clinical data. Hub lncRNAs were identified and enrichment analyses were performed to explore their potential functions. Finally, in vitro and in vivo models were used to validate the effects of the hub lncRNAs in CCA tumorigenesis and progression. Results: A total of 925 DElncRNAs were selected, of which six candidate OS-related lncRNAs and 15 candidate DFS-related lncRNAs were identified. The OS and DFS signatures were then established using four lncRNAs, respectively. We found that the OS signature and vascular invasion were independent risk factors for the OS of CCA, while the DFS signature, vascular invasion, and CA19-9 were independent risk factors for the DFS of CCA. Then, nomograms were established to achieve personalized CCA recurrence and death prediction. Furthermore, our study uncovered that MIR4435-2HG and GAPLINC might play crucial roles in CCA progression and be selected as hub lncRNAs. GO and KEGG enrichment analyses revealed that the two hub lncRNAs were closely related to CCA tumorigenesis. Finally, we demonstrated that MIR4435-2HG and GAPLINC can stimulate CCA proliferation and migration in vitro and in vivo. Conclusions: The established OS and DFS signatures are independent risk factors for OS and DFS of CCA patients, respectively. MIR4435-2HG and GAPLINC were identified as hub lncRNAs. In vitro and in vivo models revealed that MIR4435-2HG and GAPLINC can prompt CCA progression, which might be novel prognostic biomarkers and therapeutic targets for CCA.