HighlightsSelected long non-coding RNA are aberrantly expressed in hepatocellular cancers.linc-ROR is a highly upregulated lncRNA that is expressed in response to TGFβ.linc-ROR contributes to chemoresistance of HCC cells.Intercellular transfer of linc-ROR occurs within extracellular vesicles.

Hepatocellular cancer (HCC) is a highly treatment refractory cancer and is also highly resistant to adverse cellular stress. While cell behavior can be modulated by non-coding RNAs (ncRNAs) within extracellular vesicles (EVs), the contributions of long non-coding RNAs (lncRNAs) are largely unknown. To this end, the involvement and functional roles of lncRNAs contained within EVs during chemotherapeutic stress in human HCC were determined. Expression profiling identified a subset of lncRNAs that were enriched in tumor cell derived vesicles released from two different cell lines. Of these, lincRNA-VLDLR (linc-VLDLR) was significantly up-regulated in malignant hepatocytes. Exposure of HCC cells to diverse anti-cancer agents such as sorafenib, camptothecin, and doxorubicin increased linc-VLDLR expression in cells as well as within EVs released from these cells. Incubation with EVs reduced chemotherapy-induced cell death and also increased linc-VLDLR expression in recipient cells. RNAi-mediated knockdown of linc-VLDLR decreased cell viability and abrogated cell cycle progression. Moreover, knockdown of VLDLR reduced expression of ABCG2 (ATP-binding cassette, sub-family G member 2), whereas over-expression of this protein reduced the effects of VLDLR knockdown on sorafenib-induced cell death. Here, linc-VLDLR is identified as an extracellular vesicle enriched lncRNA that contributes to cellular stress responses. Implications These findings provide new insight into the role of extracellular vesicles and demonstrate the capacity of lncRNAs to mediate chemotherapeutic stress response in HCC.

Resistance to adverse environmental conditions, such as hypoxia, contributes to the reduced efficacy of anticancer therapies and tumor progression. Although deregulated expression of many long noncoding RNA (lncRNA) occurs in human cancers, the contribution of such RNA to tumor responses to hypoxia are unknown. RNA expression profiling identified several hypoxiaresponsive lncRNAs, including the long intergenic noncoding RNA, regulator of reprogramming (linc-RoR), which is also increased in expression in malignant liver cancer cells. Linc-RoR expression was increased in hypoxic regions within tumor cell xenografts in vivo. Tumor cell viability during hypoxia was reduced by small interfering RNA (siRNA) to linc-RoR. Compared with controls, siRNA to linc-RoR decreased phosphorylation of p70S6K1 (RPS6KB1), PDK1 and HIF-1a protein expression and increased expression of the linc-RoR target microRNA-145 (miR-145). LincRoR was highly expressed in extracellular RNA released by hepatocellular cancer (HCC) cells during hypoxia. Incubation with extracellular vesicle preparations containing extracellular RNA increased linc-RoR, HIF-1a expression and cell survival in recipient cells. These studies show that linc-RoR is a hypoxia-responsive lncRNA that is functionally linked to hypoxia signaling in HCC through a miR-145-HIF-1a signaling module. Furthermore, this work identifies a mechanistic role for the extracellular transfer of linc-RoR in intercellular signaling to promote cell survival during hypoxic stress.

The identification of the presence of large RNA transcripts that do not code proteins but that may have biological functions has provided an important new perspective in gene regulation. These long non-coding RNAs (lncRNAs) are being increasingly recognized to contribute to many biological processes through diverse mechanisms. The roles of these emerging genes are being recognized across kingdoms. These findings are profoundly altering our understanding of disease pathobiology and leading to the emergence of new biological concepts underlying human diseases. Strategies for the discovery and characterization of lncRNAs are highlighted. Several lncRNAs have been described in liver disease, and in liver cancers in particular. Their molecular mechanisms of action, function and contributions to disease pathophysiology are reviewed. LncRNA genes associated with liver diseases have potential roles as biomarkers of disease diagnosis, prognosis, or therapeutic response as well as direct targets for therapeutic intervention. Conclusion: The emerging knowledge in this rapidly advancing field offers promise for new fundamental knowledge and clinical applications that will be relevant for human liver diseases.