Integrative analysis of the lncRNA-miRNA-mRNA interactions in smooth muscle cell phenotypic transitions

Objectives: We previously found that the pluripotency factor OCT4 is reactivated in smooth muscle cells (SMC) in human and mouse atherosclerotic plaques and plays an atheroprotective role. Loss of OCT4 in SMC in vitro was associated with decreases in SMC migration. However, molecular mechanisms responsible for atheroprotective SMC-OCT4-dependent effects remain unknown. Methods: Since studies in embryonic stem cells demonstrated that OCT4 regulates long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), making them candidates for OCT4 effect mediators, we applied an in vitro approach to investigate the interactions between OCT4-regulated lncRNAs, mRNAs, and miRNAs in SMC. We used OCT4 deficient mouse aortic SMC (MASMC) treated with the pro-atherogenic oxidized phospholipid POVPC, which, as we previously demonstrated, suppresses SMC contractile markers and induces SMC migration. Differential expression of lncRNAs, mRNAs, and miRNAs was obtained by lncRNA/mRNA expression array and small-RNA microarray. Long non-coding RNA to mRNA associations were predicted based on their genomic proximity and association with vascular diseases. Given a recently discovered crosstalk between miRNA and lncRNA, we also investigated the association of miRNAs with upregulated/downregulated lncRNA-mRNA pairs. Results: POVPC treatment in SMC resulted in upregulating genes related to the axon guidance and focal adhesion pathways. Knockdown of Oct4 resulted in differential regulation of pathways associated with phagocytosis. Importantly, these results were consistent with our data showing that OCT4 deficiency attenuated POVPC-induced SMC migration and led to increased phagocytosis. Next, we identified several up- or downregulated lncRNA associated with upregulation of the specific mRNA unique for the OCT4 deficient SMC, including upregulation of ENSMUST00000140952-Hoxb5/6 and ENSMUST00000155531-Zfp652 along with downregulation of ENSMUST00000173605-Parp9 and, ENSMUST00000137236-Zmym1. Finally, we found that many of the downregulated miRNAs were associated with cell migration, including miR-196a-1 and miR-10a, targets of upregulated ENSMUST00000140952, and miR-155 and miR-122, targets of upregulated ENSMUST00000155531. Oppositely, the upregulated miRNAs were anti-migratory and pro-phagocytic, such as miR-10a/b and miR-15a/b, targets of downregulated ENSMUST00000173605, and miR-146a/b and miR-15b targets of ENSMUST00000137236. Conclusion: Our integrative analyses of the lncRNA-miRNA-mRNA interactions in SMC indicated novel potential OCT4-dependent mechanisms that may play a role in SMC phenotypic transitions.

ZIC2 promotes cancer stem cell traits via up-regulating OCT4 expression in lung adenocarcinoma cells

Background: Accumulating evidence has revealed the importance of cancer stem cells (CSCs) in self-renewal and chemoresistance. Previous studies reported high expression of ZIC2 was closely associated with tumorigenesis and CSC traits. However, the role of ZIC2 as a crucial factor for regulating CSC properties in lung adenocarcinoma (LAC) remains elusive. Methods: RT-PCR and WB assay were employed to assess ZIC2 expression in 20 LAC tumor tissues and the matched non-cancerous tissues. The role of ZIC2 in LAC CSC were analyzed by evaluation of CSC-related markers expression and spheroid formation in vitro. Cisplatin and paclitaxel resistance capacities were evaluated by CCK8 assay, colony formation assay, and flow cytometry analysis. Subcutaneous NOD/SCID mice models were generated to assess in vivo CSC features. Results: High expression of ZIC2 was found in LAC tumor tissues and indicated a poor overall survival in LAC patients. ZIC2 upregulated an array of CSCs-related genes, including EpCAM, OCT4, SOX2, NANOG, C-Myc and Bmi-1. Knockdown of ZIC2 inhibited sphere-forming capacity and decreased cisplatin and paclitaxel resistance. However, overexpression of ZIC2 achieved opposite effects. Mechanically, ZIC2 acts upstream of OCT4 to promote its expression, resulting in enhancement of CSC traits in LAC. Conclusion: Our results demonstrated that ZIC2 was crucial for promoting CSC traits in LAC cells, and served as a potential biomarker for predicting prognosis. The ZIC2-OCT4 network will facilitate the evaluation of the potential therapeutic efficacy of chemotherapy and predict patient sensitivity to treatment.