LncRNA ZFAS1 contributes to osteosarcoma progression via miR-520b and miR-520e-mediated inhibition of RHOC signaling

OBJECTIVES

We examined the expression of Lnc-ZFAS1 in osteosarcoma and comprehensively evaluated its effects on osteosarcoma in vitro and vivo. Moreover, we revealed the regulatory mechanism between Lnc-ZFAS1 and miR-520b/miR-520e-mediated RHOC and provided a novel clue for ameliorating osteosarcoma.

METHOD

The expression of Long non-coding RNA Zinc Finger Antisense 1 (LncRNA ZFAS1) osteosarcoma tissues and normal tissues in the TCGA database was analyzed. Then, LncRNA ZFAS1 expression was further verified in clinical samples and osteosarcoma cell lines (U2OS and KHOS), as well as the human osteoblast cell line hFOB1.19 by qRT-PCR. Thereafter, LncRNA ZFAS1 was overexpressed or silenced to explore its effects on cell proliferation, apoptosis, migration, invasion, and Epithelial-Mesenchymal Transition (EMT). The fundamental mechanism through which Lnc-ZFAS1 affects osteosarcoma progression was further investigated and verified.

RESULTS

We found that LncRNA ZFAS1 was upregulated in osteosarcoma, and Lnc-ZFAS1 overexpression facilitated osteosarcoma cells proliferation, migration, invasion and EMT, while Lnc-ZFAS1 silence exerted reverse influence. Mechanistically, Lnc-ZFAS1 functionally acted as a sponger of microRNA-520b (miR-520b) and microRNA-520e (miR-520e) to up-regulate Ras Homologue C (RHOC). In addition, depleted Lnc-ZFAS1 restrained osteosarcoma cells proliferation, migration, and invasion, which could be rescued by RHOC overexpression. Lnc-ZFAS1 was upregulated in osteosarcoma and Lnc-ZFAS1 could exert promoted impact upon osteosarcoma cells proliferation, migration, invasion, and EMT in vitro.

CONCLUSIONS

Lnc-ZFAS1 acted sponger of miR-520b and miR-520e to promote RHOC, indicating that Lnc-ZFAS1/miR-520b/RHOC and Lnc-ZFAS1/miR-520e/RHOC axes might serve as potential therapeutic strategies against osteosarcoma.

Phosphorylation of guanosine monophosphate reductase triggers a GTP-dependent switch from pro- to anti-oncogenic function of EPHA4

Signal transduction pathways post-translationally regulating nucleotide metabolism remain largely unknown. Guanosine monophosphate reductase (GMPR) is a nucleotide metabolism enzyme that decreases GTP pools by converting GMP to IMP. We observed that phosphorylation of GMPR at Tyr267 is critical for its activity and found that this phosphorylation by ephrin receptor tyrosine kinase EPHA4 decreases GTP pools in cell protrusions and levels of GTP-bound RAC1. EPHs possess oncogenic and tumor-suppressor activities, although the mechanisms underlying switches between these two modes are poorly understood. We demonstrated that GMPR plays a key role in EPHA4-mediated RAC1 suppression. This supersedes GMPR-independent activation of RAC1 by EPHA4, resulting in a negative overall effect on melanoma cell invasion and tumorigenicity. Accordingly, EPHA4 levels increase during melanoma progression and inversely correlate with GMPR levels in individual melanoma tumors. Therefore, phosphorylation of GMPR at Tyr267 is a metabolic signal transduction switch controlling GTP biosynthesis and transformed phenotypes.

Role of RHO family interacting cell polarization regulators (RIPORs) in health and disease: Recent advances and prospects

The RHO GTPase family has been suggested to play critical roles in cell growth, migration, and polarization. Regulators and effectors of RHO GTPases have been extensively explored in recent years. However, little attention has been given to RHO family interacting cell polarization regulators (RIPORs), a recently discovered protein family of RHO regulators. RIPOR proteins, namely, RIPOR1-3, bind directly to RHO proteins (A, B and C) via a RHO-binding motif and exert suppressive effects on RHO activity, thereby negatively influencing RHO-regulated cellular functions. In addition, RIPORs are phosphorylated by upstream protein kinases under chemokine stimulation, and this phosphorylation affects not only their subcellular localization but also their interaction with RHO proteins, altering the activation of RHO downstream targets and ultimately impacting cell polarity and migration. In this review, we provide an overview of recent studies on the function of RIPOR proteins in regulating RHO-dependent directional movement in immune responses and other pathophysiological functions.

RNF168 promotes RHOC degradation by ubiquitination to restrain gastric cancer progression via decreasing HDAC1 expression

Gastric cancer (GC) is the most common cancer worldwide. Although advances in the treatments, the oncogenic mechanisms are still largely unknown. RNF168 (ring-finger nuclear factor 168) is an important regulator of DNA double-strand break (DSB) repair, and its defects have been involved in the pathogenesis of a number of human diseases including cancer. However, its effects on GC are still unclear. In the study, we demonstrated that RNF168 expression was remarkably down-regulated in human GC tissues, and its low expression showed worse overall survival rate in GC patients. Importantly, we here reported that RNF168 directly interacted with Ras homolog gene family member C (RHOC) and induced its ubiquitination to promote RHOC degradation. RHOC exhibited higher expression in human GC tissues, and its knockdown significantly restrained cell proliferation, migration and invasion in GC cell lines. Moreover, RHOC knockdown led to a significant reduction in GC tumor growth in a xenograft mouse model. Additionally, histone deacetylase 1 (HDAC1) was found to be markedly decreased in GC cells with RHOC knockdown. Intriguingly, RHOC suppression-ameliorated proliferative and migratory ability in GC cells were significantly diminished by HDAC1 over-expression. Our in vivo studies finally confirmed that RHOC inhibition dramatically reduced the lung metastasis in nude mice. Collectively, all our results demonstrated that RNF168 directly interacted with RHOC to induce its degradation via promoting its ubiquitination, contributing to the inhibition of cell proliferation and metastasis in GC through decreasing HDAC1. Thus, targeting RNF168/RHOC/HDAC1 axis might be promising to develop effective therapies for GC treatment.

[miR-455 Inhibits HepG2 Cell Proliferation and Promotes Apoptosis by Targeting RhoC]

Hepatocellular carcinoma (HCC) is a common malignancy worldwide with poor prognosis and high mortality. The aberrant expression or alteration of microRNAs (miRNAs) contributes to the development and progression of cancer. Studies have shown that miR-455 plays a regulatory role in the development of HCC. Therefore, in the present study, the role of miR-455 was analyzed in HepG2 cells proliferation and apoptosis using MTT and flow cytometry methods. Binding sites were predicted by bioinformatics and luciferase assay was used to verify the target relationship between miR-455 and RhoC-encoding gene RHOC. After that, the effects of miR-455 on RHOC and its product RhoC, were explored by qPCR and Western blotting. As PTEN is a key tumor suppressor gene in HCC, and Bcl-2 and Caspase 3 are important indication of apoptosis, expression levels of PTEN, Bcl2 and Caspase 3 proteins were determined in cells overexpressing RhoC. We show that miR-455 promotes HepG2 cells apoptosis and inhibits proliferation. Bioinformatics analysis and luciferase assay indicate that specific recognition sites for miR-455 are within the RhoC 3'-UTR. Luciferase activity was significantly lower in the cells co-transfected with miR-455 mimics and RhoC-WT (p < 0.01) as compared to that in control cells, pointing that RHOC gene is, indeed, targeted by miR-455. RHOC mRNA was significantly reduced after miR-455 transfection in HepG2 cells. In addition, we show that RhoC could activate the HCC cells proliferation ability and inhibit apoptosis rate (p < 0.01), and decrease expression of PTEN and Caspase 3 (p < 0.01), while upregulating levels of Bcl2. In conclusion, our study indicates that miR-455 plays a suppressive role in HCC development by targeting RhoC-encoding mRNA.

Expression And Biological Interaction Network Of RHOC For Hepatic Carcinoma With Metastasis In PBMC Samples

Objectives

Hepatic carcinoma with metastasis remains incurable, and clinical diagnostic methods lacked adequate sensitivity and specificity. Therefore, seeking effectively diagnostic biomarkers is still essential for it. RHOC was reported to be linked to metastasis of hepatic carcinoma. However, almost all of the studies used tissues as detection samples, which was not ideal for clinical course minoring. Therefore, here, it was aimed to use PBMC samples that were not only easily accessible but also minimally invasive to determine the expression and biological interaction network of RHOC for hepatic carcinoma with metastasis.

Methods

PBMC samples were isolated. Then, RNA-seq was performed to identify the DEGs between hepatic carcinoma with metastasis and hepatic carcinoma with solitary tumor. Subsequently, q-RT-PCR was used to verify the expression level of RHOC. Finally, bioinformatic analysis was used to present the biological interaction network of RHOC for hepatic carcinoma with metastasis in PBMC samples.

Results

The results of both RNA-seq and q-RT-PCR showed that the expression level of RHOC was significantly higher in the PBMC samples of hepatic carcinoma with metastasis than in those of hepatic carcinoma with solitary tumor. By using variety of bioinformatic analysis platforms, in PBMCs, 18 co-expression genes with RHOC were identified and their interaction network showed that MYL9 and RHOC had the highest edge evidence, and were involved in some cell migration-related pathways.

Conclusion

Our results indicated that RHOC in PBMCs could be potentially minimally invasive indicators for the diagnosis and clinical course supervision of hepatic carcinoma with metastasis, and its biological interaction network determined based on bioinformatic methods would lay a foundation for further study of the role of RHOC in tumor invasion and metastasis.

MicroRNA-138 Inhibits Osteogenic Differentiation and Mineralization of Human Dedifferentiated Chondrocytes by Regulating RhoC and the Actin Cytoskeleton

MicroRNAs (miRNAs) are known to play critical roles in many cellular processes including those regulating skeletal development and homeostasis. A previous study from our group identified differentially expressed miRNAs in the developing human growth plate. Among those more highly expressed in hypertrophic chondrocytes compared to progenitor chondrocytes was miR‐138, therefore suggesting a possible role for this miRNA in regulating chondrogenesis and/or endochondral ossification. The goal of this study was to determine the function of miR‐ 138 in regulating osteogenesis by using human osteoarthritic dedifferentiated chondrocytes (DDCs) as source of inducible cells. We show that over‐expression of miR‐138 inhibited osteogenic differentiation of DDCs in vitro. Moreover, cell shape was altered and cell proliferation and possibly migration was also suppressed by miR‐138. Given alterations in cell shape, closer analysis revealed that F‐actin polymerization was also inhibited by miR‐138. Computational approaches showed that the small GTPase, RhoC, is a potential miR‐138 target gene. We pursued RhoC further given its function in regulating cell proliferation and migration in cancer cells. Indeed, miR‐138 over‐expression in DDCs resulted in decreased RhoC protein levels. A series of rescue experiments showed that RhoC over‐expression could attenuate the inhibitory actions of miR‐138 on DDC proliferation, F‐actin polymerization and osteogenic differentiation. Bone formation was also found to be enhanced within human demineralized bone scaffolds seeded with DDCs expressing both miR‐138 and RhoC. In conclusion, we have discovered a new mechanism in DDCs whereby miR‐138 functions to suppress RhoC which subsequently inhibits proliferation, F‐actin polymerization and osteogenic differentiation. To date, there are no published reports on the importance of RhoC in regulating osteogenesis. This opens up new avenues of research involving miR‐138 and RhoC pathways to better understand mechanisms regulating bone formation in addition to the potential use of DDCs as a cell source for bone tissue engineering. © 2018 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

RHOC: a key gene for endometriosis

Considerable efforts have been invested in elucidating the potential mechanisms involved in the physiopathology of endometriosis. The aims of our study were to investigate whether RHOC expression is differentially altered in the endometrium and in endometriotic lesions. A total of 40 patients diagnosed with endometriosis and 15 healthy fertile women were selected for the study. Paired biopsies of endometrial tissue (eutopic endometrium) and endometriotic lesions (ectopic endometrium) were obtained from the patients with endometriosis. Endometrium from women without endometriosis was used as a control. Expression of the RHOC gene was analyzed by real-time polymerase chain reaction in autologous endometrial tissues of women with endometriosis and in the endometrium of control women. Increased RHOC expression was detected in endometriotic lesions compared to the eutopic endometrium of women with endometriosis and control women. RHOC changes may be among the key elements involved in the origin and the maintenance of endometriosis.