Comprehensive characterization of circular RNAs in osteosarcoma cell lines

Circular RNA (circRNA) is a looped noncoding RNA with a stable structure and tissue-specific expression and widely reported to regulate cancer initiation and progression. However, the circRNA expression patterns and their roles in osteosarcoma initiation and progression are still poorly understood. In this study, we characterized the landscape of circRNAs in osteosarcoma (OS) cell lines, and calculated the epithelial-mesenchymal transition (EMT) scores for OS cell lines. The differential expression analysis revealed that the EMT-related genes were significantly upregulated in the OS cell lines with higher metastatic potentials, and some inflammation-related pathways and pathways involved in cell-cell communications were enriched by these upregulated genes. Furthermore, we constructed a circRNA-based competing endogenous RNA (ceRNA) network, which consisted of 5 circRNAs, 17 miRNAs, and 73 mRNAs. Particularly, hsa_circ_0085360, which had the highest correlation with TRPS1, were characterized by some cancer-related pathways, and TRPS1 and its target gene FGFR3 were closely associated with both event-free survival and overall survival of OS, indicating that hsa_circ_0085360 might have the potential to predict the OS prognosis. In summary, we profiled the circRNA expression patterns in OS, predicted their functionality, and explored the underlying mechanism and prognostic values, which might provide some evidences for OS-related circRNA researches.     

TGFβ mediated LINC00273 upregulation sponges mir200a-3p and promotes invasion and metastasis by activating ZEB1

Transforming growth factor β (TGFβ) is a prominent cytokine that promotes tumor progression by activating epithelial-to-mesenchymal transition (EMT). This study indicated that TGFβ exerted metastasis by inducing zinc finger E-box binding homeobox 1 (ZEB1) and a long noncoding RNA, LINC00273, expressions in A549 cells. Knocking down LINC00273 diminished TGFβ induced ZEB1 expression as well as metastasis. Mechanistically, LINC00273 acted as a molecular sponge of microRNA (miR)-200a-3p which liberate ZEB1 to perform its prometastatic functions. LINC00273 knockdown and miR200a3p mimic transfection of A549 cells were used for validating the link between TGFβ and LINC00273 induced metastasis. RNA pulldown and luciferase assay were performed to establish mir200a-3p-LINC00273 interaction. High expressions of LINC00273, TGFβ, and ZEB1 with concurrent low miR200a-3p expression had been verified in vivo and in patient samples. Overall, LINC00273 promoted TGFβ-induced lung cancer EMT through miR-200a-3p/ZEB1 feedback loop and may serve as a potential target for therapeutic intervention in lung cancer metastasis.     

LncRNA DLX6-AS1 promotes tumor proliferation and metastasis in osteosarcoma through modulating miR-641/HOXA9 signaling pathway

Osteosarcoma (OS) is the most common primary malignant bone tumor. Recently, increasing evidence has shown that the long noncoding RNA (lncRNA) DLX6-AS1 (distal-less homeobox 6 antisense 1) plays significant roles in various types of cancers. However, the functions and underlying mechanisms of DLX6-AS1 have not been explored in OS yet. In this study, we assessed the expression of DLX6-AS1 in OS tissues and cell lines and explored the underlying molecular mechanisms. DLX6-AS1 was found to be significantly upregulated in OS tissues and OS cell lines. High expression of DLX6-AS1 was significantly correlated with advanced TNM stage, high tumor grade, and distant metastasis of patients with OS. Knockdown of DLX6-AS1 suppressed OS cell proliferation, invasion, and migration, and induced cell apoptosis. Knockdown of DLX6-AS1 also suppressed in vivo tumor growth. Bioinformatics and luciferase assay analysis showed that DLX6-AS1 functioned as a competing endogenous RNA (ceRNA) to negatively regulate miR-641 expression. Furthermore, miR-641 was found to target the 3′ untranslated region of homeobox protein Hox-A9 (HOXA9) and suppressed the expression of HOXA9. Mechanistic studies showed that DLX6-AS1 regulated OS cell proliferation, invasion, and migration via regulating HOXA9 by acting as a ceRNA for miR-641. Our results suggested that DLX6-AS1 functions as a ceRNA by targeting miR-641/HOXA9 signal pathway to suppress OS cell proliferation and metastasis. Our study may provide novel insights into understanding pathogenesis and development of OS.     

miR-17-5p promotes proliferation and epithelial-mesenchymal transition in human osteosarcoma cells by targeting SRC kinase signaling inhibitor 1

MicroRNA-17-5p (miR-17-5p) and epithelial-mesenchymal transition (EMT) have been reported to participate in the development and progression of multiple cancers. However, the relationship between the miR-17-5p and EMT in osteosarcoma (OS) is still poorly understood. This study was to investigate the effects of the miR-17-5p and its potential mechanism in regulating proliferation, apoptosis, and EMT of human OS. Quantitative real-time PCR was used to detect the miR-17-5p and SRC kinase signaling inhibitor 1 (SRCIN1) messenger RNA expression in OS specimens and cell lines. After transfection with miR-17-5p inhibitors, proliferation, apoptosis, migration, and invasion of OS cells were assessed by using the Cell Counting Kit-8, the annexin V-FITC apoptosis, wound-healing, and transwell assays. The SRCIN1 was validated as a target of the miR-17-5p through bioinformatics algorithms and luciferase reporter assay. Moreover, the expression of EMT markers, E-cadherin, N-cadherin, and Snail was identified by the Western blot analysis. MiR-17-5p was significantly upregulated in OS tumor samples and cell lines. It inhibited proliferation and EMT, and promoted apoptosis in OS. The SRCIN1 was identified as a direct target of the miR-17-5p. Silenced miR-17-5p could change the expression of EMT markers, such as upregulating the expression of E-cadherin, and downregulating the expression of N-cadherin and Snail through targeting the antioncogenic SRCIN1. These findings suggest that the miR-17-5p promotes cell proliferation, and EMT in human OS by directly targeting the SRCIN1, and reveal a branch of the miR-17-5p/SRCIN1/EMT signaling pathway involved in the progression of OS.     

Retracted: miR-145 modulates epithelial-mesenchymal transition and invasion by targeting ZEB2 in non–small cell lung cancer cell lines

Lung cancer is the leading cause of cancer-related deaths worldwide. Epithelial-mesenchymal transition (EMT) is a major event that drives cancer progression. Here we aim to investigate the role of microRNA, miR-145, in regulating EMT of the highly invasive non–small cell lung cancer (NSCLC). Quantitative real-time polymerase chain reaction analysis indicated that miR-145 was downregulated in cancer tissue compared with that in adjacent normal tissue. NSCLC cell lines, namely H1299, PC7, and SPCA-1, also demonstrated miR-145 downregulation, which is correlated well with their invasive ability, assessed by the Matrigel invasion assay. miR-145 overexpression resulted in downregulation of N-cadherin, and downregulation of vimentin and E-cadherin, suggesting a decreased EMT activity. TargetScan analysis predicted that a binding site exists between miR-145 and an oncogene, ZEB2, which was verified using the dual-luciferase assay. Alteration of miR-145 expression also induced inverse effects on ZEB2 expression, and a negative correlation exists between ZEB2 and miR-145 in human tissues. ZEB2 and miR-145 also exerted antagonizing effects on the invasion of NSCLC cells. Therefore, miR-145 is an important molecule in NSCLC that regulates cancer EMT through targeting ZEB2.     

Over-expression of FoxM1 leads to epithelial-mesenchymal transition and cancer stem cell phenotype in pancreatic cancer cells

FoxM1 is known to play important role in the development and progression of many malignancies including pancreatic cancer. Studies have shown that the acquisition of epithelial-to-mesenchymal transition (EMT) phenotype and induction of cancer stem cell (CSC) or cancer stem-like cell phenotypes are highly inter-related, and contributes to drug resistance, tumor recurrence, and metastasis. The molecular mechanism(s) by which FoxM1 contributes to the acquisition of EMT phenotype and induction of CSC self-renewal capacity is poorly understood. Therefore, we established FoxM1 over-expressing pancreatic cancer (AsPC-1) cells, which showed increased cell growth, clonogenicity, and cell migration. Moreover, over-expression of FoxM1 led to the acquisition of EMT phenotype by activation of mesenchymal cell markers, ZEB1, ZEB2, Snail2, E-cadherin, and vimentin, which is consistent with increased sphere-forming (pancreatospheres) capacity and expression of CSC surface markers (CD44 and EpCAM). We also found that over-expression of FoxM1 led to decreased expression of miRNAs (let-7a, let-7b, let-7c, miR-200b, and miR-200c); however, re-expression of miR-200b inhibited the expression of ZEB1, ZEB2, vimentin as well as FoxM1, and induced the expression of E-cadherin, leading to the reversal of EMT phenotype. Finally, we found that genistein, a natural chemo-preventive agent, inhibited cell growth, clonogenicity, cell migration and invasion, EMT phenotype, and formation of pancreatospheres consistent with reduced expression of CD44 and EpCAM. These results suggest, for the first time, that FoxM1 over-expression is responsible for the acquisition of EMT and CSC phenotype, which is in part mediated through the regulation of miR-200b and these processes, could be easily attenuated by genistein.     

Long noncoding RNA AC073284.4 suppresses epithelial–mesenchymal transition by sponging miR-18b-5p in paclitaxel-resistant breast cancer cells

Breast cancer (BC) is the most prevalent malignant cancer in the world, is the leading cause of cancer-related death female. Recently, there is accumulating evidence that long noncoding RNAs (lncRNAs) might as an important role in the progression of BC. (epithelial-mesenchymal transition (EMT) is considered to play a vital role in tumor cells migration and invasion. Nevertheless, the entire biological mechanisms and functions of lncRNAs in tumor migration, invasion, and EMT remain uncertain. In the present research, we observed that the expression of lncRNA AC073284.4 was downregulated in BC paclitaxel-resistant (PR) cells (MCF-7/PR) and tissues. Bioinformatics analysis predicted that miR-18b-5p was a direct target of AC073284.4, which has been validated by dual-luciferase reporter gene assay. We further proved that AC073284.4 could directly bind to miR-18b-5p and relieve the suppression for dedicator of cytokinesis protein 4 (DOCK4). Furthermore, the underlying functional experiments demonstrated that AC073284.4 might sponge miR-18b-5p to attenuate the invasion, metastasis, and EMT of BC cell through upregulating DOCK4 expression. In summary, AC073284.4 might serve as a competing endogenous RNA (ceRNA) in BC progression via modulating miR-18b-5p/DOCK4 axis, which weakens EMT and migration of BC. These results suggesting that AC073284.4 might function as a potential novel diagnostic biomarker in the progression of BC.     

LncRNA TTN-AS1 drives invasion and migration of lung adenocarcinoma cells via modulation of miR-4677-3p/ZEB1 axis

Lung adenocarcinoma is the most prevalent type of lung cancer with a high incidence and mortality worldwide. Metastasis is the major cause of high death rate in lung cancer and the potential mechanism of lung adenocarcinoma metastasis remains indistinct. Emerging investigations have demonstrated that long noncoding RNA is a kind of non–protein coding RNA and plays a critical role in cancer progression and metastasis. TTN antisense RNA 1 (TTN-AS1) has been reported to promote cell growth and metastasis in cancer. However, the function of TTN-AS1 in lung adenocarcinoma is still to be illustrated. In this study, we observed that TTN-AS1 was upregulated in tissues and cells of lung adenocarcinoma and associated with poor overall survival. TTN-AS1 promoted cell proliferation, migration, invasion, and epithelial-mesenchymal transition in lung cancer. TTN-AS1 directly bound with miR-4677-3p and negatively regulated miR-4677-3p. MiR-4677-3p rescued the inhibitive impacts of TTN-AS1 knockdown on lung adenocarcinoma. Furthermore, zinc finger E-box binding homeobox 1 (ZEB1) was the target of miR-4677-3p, and TTN-AS1 modulated ZEB1 by competing for miR-4677-3p. TTN-AS1 drove the invasion and migration of lung adenocarcinoma cells by targeting the miR-4677-3p/ZEB1 axis. To sum up, our study offers insights into the mechanism of TTN-AS1 in lung adenocarcinoma metastasis and targeting the TTN-AS1/miR-4677-3p/ZEB1 axis may be the potential innovate therapeutic strategy for the patients with lung adenocarcinoma.     

HIF-1α Promotes Epithelial-Mesenchymal Transition and Metastasis through Direct Regulation of ZEB1 in Colorectal Cancer

It is well recognized that hypoxia-inducible factor 1 alpha (HIF-1α) is involved in cancer metastasis, chemotherapy and poor prognosis. We previously found that deferoxamine, a hypoxia-mimetic agent, induces epithelial-mesenchymal transition (EMT) in colorectal cancer. Therefore, here we explored a new molecular mechanism for HIF-1α contributing to EMT and cancer metastasis through binding to ZEB1. In this study, we showed that overexpression of HIF-1α with adenovirus infection promoted EMT, cell invasion and migration in vitro and in vivo. On a molecular level, HIF-1α directly binding to the proximal promoter of ZEB1 via hypoxia response element (HRE) sites thus increasing the transactivity and expression of ZEB1. In addition, inhibition of ZEB1 was able to abrogate the HIF-1α-induced EMT and cell invasion. HIF-1α expression was highly correlated with the expression of ZEB1 in normal colorectal epithelium, primary and metastatic CRC tissues. Interestingly, both HIF-1α and ZEB1 were positively associated with Vimentin, an important mesenchymal marker of EMT, whereas negatively associated with E-cadherin expression. These findings suggest that HIF-1α enhances EMT and cancer metastasis by binding to ZEB1 promoter in CRC. HIF-1α and ZEB1 are both widely considered as tumor-initiating factors, but our results demonstrate that ZEB1 is a direct downstream of HIF-1α, suggesting a novel molecular mechanism for HIF-1α-inducing EMT and cancer metastasis.