Accumulating evidence indicates that circular RNAs (circRNAs) are abundant in the human transcriptome. However, their involvement in biological processes, including pluripotency, remains mostly undescribed. We identified a subset of circRNAs that are enriched in undifferentiated human embryonic stem cells (hESCs) and demonstrated that two, circBIRC6 and circCORO1C, are functionally associated with the pluripotent state. Mechanistically, we found that circBIRC6 is enriched in the AGO2 complex and directly interacts with microRNAs, miR-34a, and miR-145, which are known to modulate target genes that maintain pluripotency. Correspondingly, circBIRC6 attenuates the downregulation of these target genes and suppresses hESC differentiation. We further identified hESC-enriched splicing factors (SFs) and demonstrated that circBIRC6 biogenesis in hESCs is promoted by the SF ESRP1, whose expression is controlled by the core pluripotency-associated factors, OCT4 and NANOG. Collectively, our data suggest that circRNA serves as a microRNA “sponge” to regulate the molecular circuitry, which modulates human pluripotency and differentiation.

Human induced pluripotent stem cells (hiPSCs) generated by de-differentiation of adult somatic cells offer potential solutions for the ethical issues surrounding human embryonic stem cells (hESCs), as well as their immunologic rejection after cellular transplantation. However, although hiPSCs have been described as “embryonic stem cell-like”, these cells have a distinct gene expression pattern compared to hESCs, making incomplete reprogramming a potential pitfall. It is unclear to what degree the difference in tissue of origin may contribute to these gene expression differences. To answer these important questions, a careful transcriptional profiling analysis is necessary to investigate the exact reprogramming state of hiPSCs, as well as analysis of the impression, if any, of the tissue of origin on the resulting hiPSCs. In this study, we compare the gene profiles of hiPSCs derived from fetal fibroblasts, neonatal fibroblasts, adipose stem cells, and keratinocytes to their corresponding donor cells and hESCs. Our analysis elucidates the overall degree of reprogramming within each hiPSC line, as well as the “distance” between each hiPSC line and its donor cell. We further identify genes that have a similar mode of regulation in hiPSCs and their corresponding donor cells compared to hESCs, allowing us to specify core sets of donor genes that continue to be expressed in each hiPSC line. We report that residual gene expression of the donor cell type contributes significantly to the differences among hiPSCs and hESCs, and adds to the incompleteness in reprogramming. Specifically, our analysis reveals that fetal fibroblast-derived hiPSCs are closer to hESCs, followed by adipose, neonatal fibroblast, and keratinocyte-derived hiPSCs.

NRP1 is a cancer invasion and angiogenesis enhancer. NRP1 expression is an independent predictor of cancer relapse and poor survival in NSCLC patients. NRP1 plays a critical role in tumorigenesis, cancer invasion, and angiogenesis through VEGF, PI3K, and Akt pathways. NRP1 may have potential as a new therapeutic target in NSCLC.

CLDN1 is a cancer invasion/metastasis suppressor. CLDN1 is also a useful prognostic predictor and potential drug treatment target for patients with lung adenocarcinoma.

Trop-2, a cell surface glycoprotein, contains both extracellular epidermal growth factor-like and thyroglobulin type-1 repeat domains. Low TROP2 expression was observed in lung adenocarcinoma tissues as compared with their normal counterparts. The lack of expression could be due to either the loss of heterozygosity (LOH) or hypermethylation of the CpG island DNA of TROP2 upstream promoter region as confirmed by bisulphite sequencing and methylation-specific (MS) polymerase chain reaction (PCR). 5-Aza-2′-deoxycytidine treatment on lung cancer cell (CL) lines, CL1-5 and A549, reversed the hypermethylation status and elevated both TROP2 mRNA and protein expression levels. Enforced expression of TROP2 in the lung CL line H1299 reduced AKT as well as ERK activation and suppressed cell proliferation and colony formation. Conversely, silencing TROP2 with shRNA transfection in the less efficiently tumour-forming cell line H322M enhanced AKT activation and increased tumour growth. Trop-2 could attenuate IGF-1R signalling-mediated AKT/β-catenin and ERK activation through a direct binding of IGF1. In conclusion, inactivation of TROP2 due to LOH or by DNA methylation may play an important role in lung cancer tumourigenicity through losing its suppressive effect on IGF-1R signalling and tumour growth.

Metastasis is a predominant cause of death in patients with cancer. It is a complex multistep process that needs to be better understood if we are to develop new approaches to managing tumor metastasis. Tumor cell invasion of the local stroma is suppressed by collapsin response mediator protein-1 (CRMP-1). Recently, we identified a long isoform of CRMP-1 (LCRMP-1), expression of which correlates with cancer cell invasiveness and poor clinical outcome in patients with non-small-cell lung cancer (NSCLC).Here, we report that LCRMP-1 overexpression in noninvasive human cell lines enhanced filopodia formation, cancer cell migration, and invasion via stabilization of actin. This effect required a highly conserved N-terminal region of LCRMP-1 as well as the WASP family verprolin-homologous protein-1/actin nucleation pathway (WAVE-1/actin nucleation pathway). Furthermore, LCRMP-1 appeared to act downstream of Cdc42, a Rho family protein known to be involved in actin rearrangement. In addition, LCRMP-1 associated with CRMP-1, which downregulated cancer cell metastasis by interrupting the association of LCRMP-1 and WAVE-1. Finally, we found that high-level expression of LCRMP-1 and low-level expression of CRMP-1 were associated with lymph node metastasis and poor survival in patients with NSCLC. In sum, we show that LCRMP-1 and CRMP-1 have opposing functions in regulating cancer cell invasion and metastasis and propose that this pathway may serve as a potential anticancer target. IntroductionCancer metastasis, which is the major cause of treatment failure in cancer patients, is a complex process that involves basement membrane degradation, cell migration, stromal (local) invasion, angiogenesis, intravasation into the circulatory system, adhesion, extravasation into the parenchyma of distant tissues, and colonization (1-3). These processes are regulated by numerous metastasis-promoting and -suppressing genes (4). Thus, identifying novel metastatic genes and their action mechanisms may provide new insights into the pathogenesis and management of cancer metastasis.We previously identified collapsin response mediator protein-1 (CRMP-1) as a novel invasion suppressor and showed that CRMP-1 expression is negatively associated with cell invasiveness and positively associated with better clinical outcomes in patients with non-small-cell lung cancer (NSCLC) (5). Recent studies (6, 7) have shown that CRMP-1 is functionally involved in connective tissue growth factor-mediated inhibition of invasion and metastasis in human lung adenocarcinoma.The CRMPs comprise a family of 5 cytosolic phosphoproteins that inhibit extension of the axonal growth cone during neuronal development (8-11). The members of the CRMP family are closely related 60- to 66-kDa proteins that share 50%-70% amino acid sequence homology and are capable of forming heterotetramers (8,(11)(12)(13)(14). These proteins are distributed mainly in the lamellipodia and filopodia of a neuron's axonal growth cone (14, 15), in which they mediate the signaling pathways that contr...

Signal peptide-CUB-EGF-like domain-containing protein 3 (SCUBE3) is a secreted glycoprotein that is overexpressed in lung cancer tumor tissues and is correlated with the invasive ability in a lung cancer cell line model. These observations suggest that SCUBE3 may have a role in lung cancer progression. By exogenous SCUBE3 treatment or knockdown of SCUBE3 expression, we found that SCUBE3 could promote lung cancer cell mobility and invasiveness. Knockdown of SCUBE3 expression also suppressed tumorigenesis and cancer metastasis in vivo. The secreted SCUBE3 proteins were cleaved by gelatinases (matrix metalloprotease-2 (MMP-2) and MMP-9) in media to release two major fragments: the N-terminal epidermal growth factor-like repeats and the C-terminal complement proteins C1r/C1s, Uegf and Bmp1 (CUB) domain. Both the purified SCUBE3 protein and the C-terminal CUB domain fragment, bound to transforming growth factor-b (TGF-b) type II receptor through the C-terminal CUB domain, activated TGF-b signaling and triggered the epithelial-mesenchymal transition (EMT). This process includes the induction of Smad2/3 phosphorylation, the increase of Smad2/3 transcriptional activity and the upregulation of the expression of target genes involved in EMT and cancer progression (such as TGF-b1, MMP-2, MMP-9, plasminogen activator inhibitor type-1, vascular endothelial growth factor, Snail and Slug), thus promoting cancer cell mobility and invasion. In conclusion, in lung cancer cells, SCUBE3 could serve as an endogenous autocrine and paracrine ligand of TGF-b type II receptor, which could regulate TGF-b receptor signaling and modulate EMT and cancer progression.

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