lnc-PKD2-2-3, identified by long non-coding RNA expression profiling, is associated with pejorative tumor features and poor prognosis, enhances cancer stemness and may serve as cancer stem-cell marker in cholangiocarcinoma.

The present study aimed to explore the long non‑coding RNA (lncRNA) expression profiles and correlation of lnc‑PKD2‑2‑3 with tumor features and prognosis, and to investigate its effect on regulating cancer‑cell stemness and its potential as a cancer stem cell (CSC) marker in cholangiocarcinoma (CCA). lncRNA expression profiles were determined in 3 pairs of CCA tumors and adjacent tissues by microarray analysis, and lnc‑PKD2‑2‑3 expression was then validated in 60 paired samples by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Expression of common CSC markers [(CD44, CD133 and octamer‑binding transcription factor 4 (OCT4)], CD44+CD133+ cell proportions, sphere formation efficiency and drug resistance to 5‑fluorouracil (5‑FU) were measured following ectopic overexpression of lnc‑PKD2‑2‑3 or silencing via small hairpin RNA lentivirus transfection into the TFK‑1 and Huh‑28 CCA cell lines. Finally, lnc‑PKD2‑2‑3 expression was measured in CCA stem‑like cells and normal CCA cells. The results from the microarray analysis identified a total of 4,223 upregulated and 4,596 downregulated lncRNAs between CCA tumor tissue and paired adjacent tissue, which were enriched in regulating cancer‑associated pathways. RT‑qPCR validation revealed that lnc‑PKD2‑2‑3 was upregulated in CCA and associated with a higher Eastern Cooperative Oncology Group performance score, poor differentiation, advanced TNM stage, increased carcinoembryonic antigen and poor overall survival in CCA patients. In vitro, lnc‑PKD2‑2‑3 increased CD44, CD133 and OCT4 expression as well as the CD44+CD133+ cell proportion, raised the sphere formation efficiency and enhanced drug resistance to 5‑FU in TFK‑1 and Huh‑28 cells. In addition, lnc‑PKD2‑2‑3 was positively correlated with CSC markers in CCA tumor tissues and was markedly upregulated in CCA stem‑like cells compared with that in normal CCA cells. In conclusion, lnc‑PKD2‑2‑3, selected by lncRNA expression profiling, was associated with pejorative tumor features and poor prognosis, enhanced cancer stemness and may serve as a CSC marker in CCA.