Transcriptional up-regulation of RhoE by hypoxia-inducible factor (HIF)-1 promotes epithelial to mesenchymal transition of gastric cancer cells during hypoxia

The potential roles of HIF-1α in epithelial-mesenchymal transition and ferroptosis in tumor cells

In tumors, the rapid proliferation of cells and the imperfect blood supply system lead to hypoxia, which can regulate the adaptation of tumor cells to the hypoxic environment through hypoxia-inducible factor-1α (HIF-1α) and promote tumor development in multiple ways. Recent studies have found that epithelial-mesenchymal transition (EMT) and ferroptosis play important roles in the progression of tumor cells. The activation of HIF-1α is considered a key factor in inducing EMT in tumor cells. When HIF-1α is activated, it can regulate EMT-related genes, causing tumor cells to gradually lose their epithelial characteristics and acquire more invasive mesenchymal traits. The occurrence of EMT allows tumor cells to better adapt to changes in the surrounding tissue, enhancing their migratory and invasive capabilities, thus promoting tumor progression. At the same time, HIF-1α also plays a crucial regulatory role in ferroptosis in tumor cells. In a hypoxic environment, HIF-1α may affect processes such as iron metabolism and oxidative stress responses, inducing ferroptosis in tumor cells. This article briefly reviews the dual role of HIF-1α in EMT and ferroptosis in tumor cells, helping to gain a deeper understanding of the regulatory pathways of HIF-1α in the development of tumor cells, providing a new perspective for understanding the pathogenesis of tumors. The regulation of HIF-1α may become an important strategy for future tumor therapy.

RND3 Potentiates Proinflammatory Activation through NOTCH Signaling in Activated Macrophages

Macrophage activation is a complex process with multiple control elements that ensures an adequate response to the aggressor pathogens and, on the other hand, avoids an excess of inflammatory activity that could cause tissue damage. In this study, we have identified RND3, a small GTP-binding protein, as a new element in the complex signaling process that leads to macrophage activation. We show that RND3 expression is transiently induced in macrophages activated through Toll receptors and potentiated by IFN-γ. We also demonstrate that RND3 increases NOTCH signaling in macrophages by favoring NOTCH1 expression and its nuclear activity; however, Rnd3 expression seems to be inhibited by NOTCH signaling, setting up a negative regulatory feedback loop. Moreover, increased RND3 protein levels seem to potentiate NFκB and STAT1 transcriptional activity resulting in increased expression of proinflammatory genes, such as Tnf-α, Irf-1, or Cxcl-10. Altogether, our results indicate that RND3 seems to be a new regulatory element which could control the activation of macrophages, able to fine tune the inflammatory response through NOTCH.

Molecular basis and current insights of atypical Rho small GTPase in cancer

Atypical Rho GTPases are a subtype of the Rho GTPase family that are involved in diverse cellular processes. The typical Rho GTPases, led by RhoA, Rac1 and Cdc42, have been well studied, while relative studies on atypical Rho GTPases are relatively still limited and have great exploration potential. With the increase in studies, current evidence suggests that atypical Rho GTPases regulate multiple biological processes and play important roles in the occurrence and development of human cancers. Therefore, this review mainly discusses the molecular basis of atypical Rho GTPases and their roles in cancer. We summarize the sequence characteristics, subcellular localization and biological functions of each atypical Rho GTPase. Moreover, we review the recent advances and potential mechanisms of atypical Rho GTPases in the development of multiple cancers. A comprehensive understanding and extensive exploration of the biological functions of atypical Rho GTPases and their molecular mechanisms in tumors will provide important insights into the pathophysiology of tumors and the development of cancer therapeutic strategies.

Signaling pathways and therapeutic interventions in gastric cancer

Gastric cancer (GC) ranks fifth in global cancer diagnosis and fourth in cancer-related death. Despite tremendous progress in diagnosis and therapeutic strategies and significant improvements in patient survival, the low malignancy stage is relatively asymptomatic and many GC cases are diagnosed at advanced stages, which leads to unsatisfactory prognosis and high recurrence rates. With the recent advances in genome analysis, biomarkers have been identified that have clinical importance for GC diagnosis, treatment, and prognosis. Modern molecular classifications have uncovered the vital roles that signaling pathways, including EGFR/HER2, p53, PI3K, immune checkpoint pathways, and cell adhesion signaling molecules, play in GC tumorigenesis, progression, metastasis, and therapeutic responsiveness. These biomarkers and molecular classifications open the way for more precise diagnoses and treatments for GC patients. Nevertheless, the relative significance, temporal activation, interaction with GC risk factors, and crosstalk between these signaling pathways in GC are not well understood. Here, we review the regulatory roles of signaling pathways in GC potential biomarkers, and therapeutic targets with an emphasis on recent discoveries. Current therapies, including signaling-based and immunotherapies exploited in the past decade, and the development of treatment for GC, particularly the challenges in developing precision medications, are discussed. These advances provide a direction for the integration of clinical, molecular, and genomic profiles to improve GC diagnosis and treatments.

HIF in Gastric Cancer: Regulation and Therapeutic Target

HIF means hypoxia-inducible factor gene family, and it could regulate various biological processes, including tumor development. In 2021, the FDA approved the new drug Welireg for targeting HIF-2a, and it is mainly used to treat von Hippel-Lindau syndrome, which demonstrated its good prospects in tumor therapy. As the fourth deadliest cancer worldwide, gastric cancer endangers the health of people all across the world. Currently, there are various treatment methods for patients with gastric cancer, but the five-year survival rate of patients with advanced gastric cancer is still not high. Therefore, here we reviewed the regulatory role and target role of HIF in gastric cancer, and provided some references for the treatment of gastric cancer.

Effect of RhoE expression on the migration and invasion of tongue squamous cell carcinoma

OBJECTIVES

This study aims to investigate the effect of RhoE expression on the migration and invasion of tongue squamous cell carcinoma (TSCC).

METHODS

Forty-eight TSCC cases were selected from the Maxillofacial Surgery Center of Qingdao Municipal Hospital from 2017 to 2019. The expression of RhoE in the specimens (TSCC and adjacent tissues) was detected by immunohistochemistry, and RhoE mRNA and protein were extracted to further detect the expression of RhoE. SCC-4 and CAL-27 cells were selected for in vitro experiments. Transient transfection was used to overexpress RhoE. Real-time fluorescence quantitative PCR (qRT-PCR) and Western blot analyses were conducted to detect the overexpression efficiency. Scratch test and Transwell cell invasion tests were used to detect the migration and invasion ability of TSCC, respectively. The expression levels of Rho-associated coiled-coil-containing protein kinase 1 (ROCK1), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-9 (MMP-9) were detected by Western blot. Experimental data were analyzed by Graphpad prism 8.2.1 software.

RESULTS

The expression level of RhoE in TSCC was significantly lower than that in adjacent tissues (P<0.05). The migration and invasion abilities of TSCC were significantly lower than those in the control group (P<0.05). The Western blot showed significantly lower expression levels of ROCK1, MMP-2, and MMP-9 in the experimental group than in the control group (P<0.05).

CONCLUSIONS

RhoE expression is low in TSCC. Over expression RhoE in TSCC can significantly decrease its migration and invasion abilities. Hence, RhoE may play an important role in regulating the metastasis and invasion of TSCC and provide a new target for gene therapy.

Pathophysiological functions of Rnd proteins

Rnd proteins constitute a subfamily of Rho GTPases represented in mammals by Rnd1, Rnd2 and Rnd3. Despite their GTPase structure, their specific feature is the inability to hydrolyse GTP-bound nucleotide. This aspect makes them atypical among Rho GTPases. Rnds are regulated for their expression at the transcriptional or post-transcriptional levels and they are activated through post-translational modifications and interactions with other proteins. Rnd proteins are mainly involved in the regulation of the actin cytoskeleton and cell proliferation. Whereas Rnd3 is ubiquitously expressed, Rnd1 and 2 are tissue-specific. Increasing data has described their important role during development and diseases. Herein, we describe their involvement in physiological and pathological conditions with a focus on the neuronal and vascular systems, and summarize their implications in tumorigenesis.

Ingenuity pathway analysis of differentially expressed genes involved in signaling pathways and molecular networks in RhoE gene‑edited cardiomyocytes

RhoE/Rnd3 is an atypical member of the Rho superfamily of proteins, However, the global biological function profile of this protein remains unsolved. In the present study, a RhoE‑knockout H9C2 cardiomyocyte cell line was established using CRISPR/Cas9 technology, following which differentially expressed genes (DEGs) between the knockout and wild‑type cell lines were screened using whole genome expression gene chips. A total of 829 DEGs, including 417 upregulated and 412 downregulated, were identified using the threshold of fold changes ≥1.2 and P<0.05. Using the ingenuity pathways analysis system with a threshold of ‑Log (P‑value)>2, 67 canonical pathways were found to be enriched. Many of the detected signaling pathways, including that of oncostatin M signaling, were found to be associated with the inflammatory response. Subsequent disease and function analysis indicated that apart from cardiovascular disease and development function, RhoE may also be involved in other diseases and function, including organismal survival, cancer, organismal injury and abnormalities, cell‑to‑cell signaling and interaction, and molecular transport. In addition, 885 upstream regulators were enriched, including 59 molecules that were predicated to be strongly activated (Z‑score >2) and 60 molecules that were predicated to be significantly inhibited (Z‑scores <‑2). In particular, 33 regulatory effects and 25 networks were revealed to be associated with the DEGs. Among them, the most significant regulatory effects were 'adhesion of endothelial cells' and 'recruitment of myeloid cells' and the top network was 'neurological disease', 'hereditary disorder, organismal injury and abnormalities'. In conclusion, the present study successfully edited the RhoE gene in H9C2 cells using CRISPR/Cas9 technology and subsequently analyzed the enriched DEGs along with their associated canonical signaling pathways, diseases and functions classification, upstream regulatory molecules, regulatory effects and interaction networks. The results of the present study should facilitate the discovery of the global biological and functional properties of RhoE and provide new insights into role of RhoE in human diseases, especially those in the cardiovascular system.

Dysregulation of Rho GTPases in Human Cancers

Rho GTPases play central roles in numerous cellular processes, including cell motility, cell polarity, and cell cycle progression, by regulating actin cytoskeletal dynamics and cell adhesion. Dysregulation of Rho GTPase signaling is observed in a broad range of human cancers, and is associated with cancer development and malignant phenotypes, including metastasis and chemoresistance. Rho GTPase activity is precisely controlled by guanine nucleotide exchange factors, GTPase-activating proteins, and guanine nucleotide dissociation inhibitors. Recent evidence demonstrates that it is also regulated by post-translational modifications, such as phosphorylation, ubiquitination, and sumoylation. Here, we review the current knowledge on the role of Rho GTPases, and the precise mechanisms controlling their activity in the regulation of cancer progression. In addition, we discuss targeting strategies for the development of new drugs to improve cancer therapy.

Shedding New Light on Cancer Metabolism: A Metabolic Tightrope Between Life and Death

Since the earliest findings of Otto Warburg, who discovered the first metabolic differences between lactate production of cancer cells and non-malignant tissues in the 1920s, much time has passed. He explained the increased lactate levels with dysfunctional mitochondria and aerobic glycolysis despite adequate oxygenation. Meanwhile, we came to know that mitochondria remain instead functional in cancer cells; hence, metabolic drift, rather than being linked to dysfunctional mitochondria, was found to be an active act of direct response of cancer cells to cell proliferation and survival signals. This metabolic drift begins with the use of sugars and the full oxidative phosphorylation via the mitochondrial respiratory chain to form CO₂, and it then leads to the formation of lactic acid via partial oxidation. In addition to oncogene-driven metabolic reprogramming, the oncometabolites themselves alter cell signaling and are responsible for differentiation and metastasis of cancer cells. The aberrant metabolism is now considered a major characteristic of cancer within the past 15 years. However, the proliferating anabolic growth of a tumor and its spread to distal sites of the body is not explainable by altered glucose metabolism alone. Since a tumor consists of malignant cells and its tumor microenvironment, it was important for us to understand the bilateral interactions between the primary tumor and its microenvironment and the processes underlying its successful metastasis. We here describe the main metabolic pathways and their implications in tumor progression and metastasis. We also portray that metabolic flexibility determines the fate of the cancer cell and ultimately the patient. This flexibility must be taken into account when deciding on a therapy, since singular cancer therapies only shift the metabolism to a different alternative path and create resistance to the medication used. As with Otto Warburg in his days, we primarily focused on the metabolism of mitochondria when dealing with this scientific question.

Copper promotes migration of adipose-derived stem cells by enhancing vimentin-Ser39 phosphorylation

Mesenchymal stem cells (MSCs) are widely studied for their application in cell therapy. A noticed drawback of these cells in response to tissue injury is the low efficiency of homing. The present study was undertaken to explore a possible approach to promote the migration of MSCs. Primary cultures of rat adipose-derived stem cells (rADSCs) were cultured in standard L-DMEM media supplemented with or without copper (Cu) at its final concentration of 20 μM in cultures. The analyses of transwell and wound-healing assay revealed that Cu supplementation significantly promotes the migration of rADSCs in cultures. Further analysis found that Cu stimulated the phosphorylation of vimentin Ser39. Point mutation of vimentin Ser39 by substituting Ser with Ala prevented Cu-promoted migration of rADSCs. This study thus demonstrates that Cu promotes migration of rADSCs in cultures through at least in part Cu stimulation of vimentin Ser39 phosphorylation.

The Rho GTPase RND3 regulates adipocyte lipolysis

BACKGROUND

Adipose tissue plays a crucial role in diet- and obesity-related insulin resistance, with implications for several metabolic diseases. Identification of novel target genes and mechanisms that regulate adipocyte function could lead to improved treatment strategies. RND3 (RhoE/Rho8), a Rho-related GTP-binding protein that inhibits Rho kinase (ROCK) signaling, has been linked to diverse diseases such as apoptotic cardiomyopathy, heart failure, cancer and type 2 diabetes, in part by regulating cytoskeleton dynamics and insulin-mediated glucose uptake.

RESULTS

We here investigated the expression of RND3 in adipose tissue in human obesity, and discovered a role for RND3 in regulating adipocyte metabolism. In cross-sectional and prospective studies, we observed 5-fold increased adipocyte levels of RND3 mRNA in obesity, reduced levels after surgery-induced weight loss, and positive correlations of RND3 mRNA with adipocyte size and surrogate measures of insulin resistance (HOMA2-IR and circulating triglyceride/high-density lipoprotein cholesterol (TAG/HDL-C) ratio). By screening for RND3-dependent gene expression following siRNA-mediated RND3 knockdown in differentiating human adipocytes, we found downregulation of inflammatory genes and upregulation of genes related to adipocyte ipolysis and insulin signaling. Treatment of adipocytes with tumor necrosis factor alpha (TNFα), lipopolysaccharide (LPS), hypoxia or cAMP analogs increased RND3 mRNA levels 1.5-2-fold. Functional assays in primary human adipocytes confirmed that RND3 knockdown reduces cAMP- and isoproterenol-induced lipolysis, which were mimicked by treating cells with ROCK inhibitor. This effect could partly be explained by reduced protein expression of adipose triglyceride lipase (ATGL) and phosphorylated hormone-sensitive lipase (HSL).

CONCLUSION

We here uncovered a novel differential expression of adipose RND3 in obesity and insulin resistance, which may at least partly depend on a causal effect of RND3 on adipocyte lipolysis.

Knockdown of RhoE Expression Enhances TGF-β-Induced EMT (epithelial-to-mesenchymal transition) in Cervical Cancer HeLa Cells

Cervical cancer with early metastasis of the primary tumor is associated with poor prognosis and poor therapeutic outcomes. Since epithelial-to-mesenchymal transition (EMT) plays a role in acquisition of the ability to invade the pelvic lymph nodes and surrounding tissue, it is important to clarify the molecular mechanism underlying EMT in cervical cancer. RhoE, also known as Rnd3, is a member of the Rnd subfamily of Rho GTPases. While previous reports have suggested that RhoE may act as either a positive or a negative regulator of cancer metastasis and EMT, the role of RhoE during EMT in cervical cancer cells remains unclear. The present study revealed that RhoE expression was upregulated during transforming growth factor-β (TGF-β)-mediated EMT in human cervical cancer HeLa cells. Furthermore, reduced RhoE expression enhanced TGF-β-mediated EMT and migration of HeLa cells. In addition, we demonstrated that RhoE knockdown elevated RhoA activity and a ROCK inhibitor partially suppressed the acceleration of TGF-β-mediated EMT by RhoE knockdown. These results indicate that RhoE suppresses TGF-β-mediated EMT, partially via RhoA/ROCK signaling in cervical cancer HeLa cells.

Copper promotes the migration of bone marrow mesenchymal stem cells via Rnd3-dependent cytoskeleton remodeling

The motility of mesenchymal stem cells (MSCs) is highly related to their homing in vivo, a critical issue in regenerative medicine. Our previous study indicated copper (Cu) might promote the recruitment of endogenous MSCs in canine esophagus defect model. In this study, we investigated the effect of Cu on the motility of bone marrow mesenchymal stem cells (BMSCs) and the underlying mechanism in vitro. Cu supplementation could enhance the motility of BMSCs, and upregulate the expression of hypoxia-inducible factor 1α (Hif1α) at the protein level, and upregulate the expression of rho family GTPase 3 (Rnd3) at messenger RNA and protein level. When Hif1α was silenced by small interfering RNA (siRNA), Cu-induced Rnd3 upregulation was blocked. When Rnd3 was silenced by siRNA, the motility of BMSCs was decreased with or without Cu supplementation, and Cu-induced cytoskeleton remodeling was neutralized. Furthermore, overexpression of Rnd3 also increased the motility of BMSCs and induced cytoskeleton remodeling. Overall, our results demonstrated that Cu enhanced BMSCs migration through, at least in part, cytoskeleton remodeling via Hif1α-dependent upregulation of Rnd3. This study provided an insight into the mechanism of the effect of Cu on the motility of BMSCs, and a theoretical foundation of applying Cu to improve the recruitment of BMSCs in tissue engineering and cytotherapy.

Mechanisms of Metastasis and Cell Mobility - The Role of Metabolism

Tumour metastasis is responsible for more than 90% of tumour-associated mortality. About one third of breast cancer patients in the early stage develop metastases. The transformation in tumour development referred to as the "metastatic cascade" or "metastatic cycle" is a complex and multi-stage event. While it is generally recognised that epithelial-mesenchymal transformation (EMT) plays a crucial role in cancer progression and metastasis, the metabolic events in this process have received little attention to date. We would therefore like to provide a brief overview here of the influence of the metabolism on the progression and metastasis of tumours.

Hypoxia induces actin cytoskeleton remodeling by regulating the binding of CAPZA1 to F-actin via PIP2 to drive EMT in hepatocellular carcinoma

Studies have shown that hypoxia can induce cytoskeletal injury and remodeling through the activation of the RhoA/ROCK signaling pathway by hypoxia-inducible factor-1α (HIF-1α). Our previous study confirmed that CAPZA1 can modulate EMT by regulating actin cytoskeleton remodeling. However, the relationship between HIF-1α and CAPZA1 has not been illustrated. Therefore, this study aimed to investigate the mechanism by which hypoxia induces the remodeling of the actin cytoskeleton by regulating CAPZA1 in hepatocellular carcinoma (HCC) cells. In the present study, we showed that the low expression of CAPZA1 promotes HCC cell invasion and migration in vitro and in vivo by regulating actin cytoskeleton remodeling to drive EMT. Furthermore, we found that the combination of PIP2 and CAPZA1 enables CAPZA1 to be released from the barbed end of F-actin, which in turn drives the remodeling of the actin cytoskeleton. Finally, we confirmed that hypoxia increases PIP2 levels and its binding to CAPZA1 in HCC cells via the HIF-1α/RhoA/ROCK1 pathway. Thus, CAPZA1 and PIP2 could be therapeutic targets to inhibit the invasion and migration promoted by hypoxia in HCC cells.

New insight into the role of long non-coding RNAs in the pathogenesis of preeclampsia

OBJECTIVE

Dysregulation of lncRNAs and the absence of coordination between them could affect the normal placentation, uteroplacental circulation, and endothelial cell function. All these misfunctions can finally lead to preeclampsia.

METHODS

 In the present review, we discuss current literature (till May 2018) about lncRNAs expression and function in the placenta, trophoblast cells, and decidua.

RESULTS AND CONCLUSION

It is explained how altered expression of the lncRNAs and abnormal regulation of them affect the risk of preeclampsia. However, the interaction between various lncRNAs and coordinate regulation of them in health and failure of such coordinative mechanisms in diseases such as preeclampsia need to be elucidated.

LDH-Apromotes epithelial-mesenchymal transition by upregulating ZEB2 in intestinal-type gastric cancer

Introduction

Epithelial-mesenchymal transition (EMT) is regarded as a crucial process of invasion and metastasis, which contribute greatly to cancer-related relapse and death. Based on research results that hypoxia can trigger gastric cancer EMT and decreasing lactate production can selectively kill hypoxic cancer cells, we infer that lactate dehydrogenase A (LDH-A) transforming pyruvate into lactate is at least in part responsible for poor prognosis of gastric cancer.

Materials and methods

We used siRNA to knock down LDH-A in intestinal-type gastric cancer (ITGC) cell lines SGC7901 and BGC823. Western blot and RT-PCR were applied to detect mRNA and protein expression of EMT-related genes, respectively. Transwell invasion assay and migration assay were applied to study invasive and migratory abilities, respectively. Survival analysis was used to evaluate prognostic values.

Results and conclusion

The results of in vitro experiment demonstrated that LDH-A facilitates ITGC cells’ invasion and migration by upregulating ZEB2. The positive correlation between LDH-A and ZEB2 was verified in 371 ITGC specimens. Survival analysis indicated that co-expression of LDH-A/ZEB2 had synergetic power to predict overall survival. Thus, we conclude that the close relationship between LDH-A and ZEB2 may offer a potential therapeutic strategy for ITGC.

Novel metastatic models of esophageal adenocarcinoma derived from FLO-1 cells highlight the importance of E-cadherin in cancer metastasis

There is currently a paucity of preclinical models available to study the metastatic process in esophageal cancer. Here we report FLO-1, and its isogenic derivative FLO-1LM, as two spontaneously metastatic cell line models of human esophageal adenocarcinoma. We show that FLO-1 has undergone epithelial-mesenchymal transition and metastasizes following subcutaneous injection in mice. FLO-1LM, derived from a FLO-1 liver metastasis, has markedly enhanced proliferative, clonogenic, anti-apoptotic, invasive, immune-tolerant and metastatic potential. Genome-wide RNAseq profiling revealed a significant enrichment of metastasis-related pathways in FLO-1LM cells. Moreover, CDH1, which encodes the adhesion molecule E-cadherin, was the most significantly downregulated gene in FLO-1LM compared to FLO-1. Consistent with this, repression of E-cadherin expression in FLO-1 cells resulted in increased metastatic activity. Importantly, reduced E-cadherin expression is commonly reported in esophageal adenocarcinoma and independently predicts poor patient survival. Collectively, these findings highlight the biological importance of E-cadherin activity in the pathogenesis of metastatic esophageal adenocarcinoma and validate the utility of FLO-1 parental and FLO-1LM cells as preclinical models of metastasis in this disease.

Targeting hypoxic response for cancer therapy

Hypoxic tumor microenvironment (HTM) is considered to promote metabolic changes, oncogene activation and epithelial mesenchymal transition, and resistance to chemo- and radio-therapy, all of which are hallmarks of aggressive tumor behavior. Cancer cells within the HTM acquire phenotypic properties that allow them to overcome the lack of energy and nutrients supply within this niche. These phenotypic properties include activation of genes regulating glycolysis, glucose transport, acidosis regulators, angiogenesis, all of which are orchestrated through the activation of the transcription factor, HIF1A, which is an independent marker of poor prognosis. Moreover, during the adaptation to a HTM cancer cells undergo deep changes in mitochondrial functions such as “Warburg effect” and the “reverse Warburg effect”.

This review aims to provide an overview of the characteristics of the HTM, with particular focus on novel therapeutic strategies currently in clinical trials, targeting the adaptive response to hypoxia of cancer cells.

Epithelial–mesenchymal transition and gastric cancer stem cell

Gastric cancer remains a big health problem in China. Gastric cancer cells contain a small subpopulation of cells that exhibit capabilities of differentiation and tumorigenicity. A putative explanation for ineffective therapy is the presence of cancer stem-like cells. Side population cells, which have cancer stem-like cells’ property, are characterized by the high efflux ability of Hoechst 33342 dye. Side population cells have been isolated from gastric cancer cell lines in previous studies. The epithelial–mesenchymal transition is very important in the invasion and metastasis of epithelial-derived cancers. More and more studies showed that gastric cancer stem-like cells possess high invasive ability and epithelial–mesenchymal transition property. A brief overview of the recent advancements in gastric cancer stem-like cells and epithelial–mesenchymal transition will be helpful for providing novel insight into gastric cancer treatment.

Potential Coagulation Factor-Driven Pro-Inflammatory Responses in Ovarian Cancer Tissues Associated with Insufficient O₂ and Plasma Supply

Tissue factor (TF) is a cell surface receptor for coagulation factor VII (fVII). The TF-activated fVII (fVIIa) complex is an essential initiator of the extrinsic blood coagulation process. Interactions between cancer cells and immune cells via coagulation factors and adhesion molecules can promote progression of cancer, including epithelial ovarian cancer (EOC). This process is not necessarily advantageous, as tumor tissues generally undergo hypoxia due to aberrant vasculature, followed by reduced access to plasma components such as coagulation factors. However, hypoxia can activate TF expression. Expression of fVII, intercellular adhesion molecule-1 (ICAM-1), and multiple pro-inflammatory cytokines can be synergistically induced in EOC cells in response to hypoxia along with serum deprivation. Thus, pro-inflammatory responses associated with the TF-fVIIa-ICAM-1 interaction are expected within hypoxic tissues. Tumor tissue consists of multiple components such as stromal cells, interstitial fluid, albumin, and other micro-factors such as proton and metal ions. These factors, together with metabolism reprogramming in response to hypoxia and followed by functional modification of TF, may contribute to coagulation factor-driven inflammatory responses in EOC tissues. The aim of this review was to describe potential coagulation factor-driven inflammatory responses in hypoxic EOC tissues. Arguments were extended to clinical issues targeting this characteristic tumor environment.

Chaperone-mediated autophagy regulates proliferation by targeting RND3 in gastric cancer

LAMP2A is the key protein of chaperone-mediated autophagy (CMA), downregulation of LAMP2A leads to CMA blockade. CMA activation has been implicated in cancer growth, but the exact mechanisms are unclear. Elevated expression of LAMP2A was found in 8 kinds of tumors (n=747), suggesting that LAMP2A may have an important role in cancer progression. Unsurprisingly, LAMP2A knockdown in gastric cancer (GC) cells hindered proliferation, accompanied with altered expression of cell cycle-related proteins and accumulation of RND3/RhoE. Interactomic and KEGG analysis revealed that RND3 was a putative CMA substrate. Further study demonstrated that RND3 silencing could partly rescue the proliferation arrest induced by LAMP2A knockdown; RND3 was increased upon lysosome inhibition via both chemicals and LAMP2A-shRNA; Furthermore, RND3 could interact with CMA components HSPA8 and LAMP2A, and be engulfed by isolated lysosomes. Thus, constant degradation of RND3 by CMA is required to sustain rapid proliferation of GC cells. At last, the clinical significance of LAMP2A was explored in 593 gastric noncancerous lesions and 173 GC tissues, the results revealed that LAMP2A is a promising biomarker for GC early warning and prognosis of female GC patients.

Ethanol extract of Lophatheri Herba exhibits anti-cancer activity in human cancer cells by suppression of metastatic and angiogenic potential

Lophatheri Herba (LH), dried leaf of Lophatherum gracile Brongn, has long been used to reduce thirst and treat fever and inflammation in Chinese medicine. Recent studies have shown that LH has anti-viral, anti-bacterial, anti-cancer, anti-oxidant, diuretic, and hyperglycemic properties. However, the effects of an ethanol extract of L. herba (ELH), at non-cytotoxic doses, on the metastatic and angiogenic abilities of malignant tumor cells have not been reported. We found that ELH significantly suppressed p38, JNK, and NF-κB activation and proteolytic activities under phorbol 12-myristate 13-acetate (PMA) stimulation, thus leading to a decrease in metastatic potential, including migration and invasion. In addition, ELH suppressed tumor-induced angiogenesis, including migration and tube formation in human umbilical vein endothelial cells (HUVECs) and microvessel sprouting from aortic rings via decreasing the pro-angiogenic factors in tumors. Interestingly, in ovo xenografts ELH-treated HT1080 cells did not increase in volume and eventually disappeared, owing to a lack of angiogenesis. Daily oral administration of ELH at 50 and 100 mg/kg markedly inhibited metastatic colonization of B16F10 cells in the lungs of C57BL/6J mice and caused no apparent side effects. These data collectively indicate that ELH is safe and may be useful for managing metastasis and growth of malignant cancers.

Rnd3 in Cancer: A Review of the Evidence for Tumor Promoter or Suppressor

Rho-GTPases are members of the Ras superfamily of small GTPases and are general modulators of important cellular processes in tumor biology such as migration and proliferation. Among these proteins, Rnd3/RhoE, an atypical Rho-GTPase devoid of GTP hydrolytic activity, has recently been studied for its putative role in tumorigenesis. Indeed, Rnd3 is implicated in processes, such as proliferation and migration, whose deregulation is linked to cancer development and metastasis. The aim of this review is to provide an overview of the data surrounding Rnd3 deregulation in cancers, its origin, and consequences. Presented here is a comprehensive account of the expression status and biological output obtained in prostate, liver, stomach, colon, lung, and brain cancers as well as in melanoma and squamous cell carcinoma. Although there appears to be no general consensus about Rnd3 expression in cancers as this protein is differently altered according to the tumor context, these alterations overwhelmingly favor a protumorigenic role. Thus, depending on the tumor type, it may behave either as a tumor suppressor or as a tumor promoter. Importantly, the deregulation of Rnd3, in most cases, is linked to patient poor outcome.

IMPLICATIONS

Rnd3 has prognostic marker potential as exemplified in lung cancers and Rnd3 or Rnd3-associated signaling pathways may represent a new putative therapeutic target. Mol Cancer Res; 14(11); 1033-44. ©2016 AACR.

Deregulation of Rho GTPases in cancer

In vitro and in vivo studies and evidence from human tumors have long implicated Rho GTPase signaling in the formation and dissemination of a range of cancers. Recently next generation sequencing has identified direct mutations of Rho GTPases in human cancers. Moreover, the effects of ablating genes encoding Rho GTPases and their regulators in mouse models, or through pharmacological inhibition, strongly suggests that targeting Rho GTPase signaling could constitute an effective treatment. In this review we will explore the various ways in which Rho signaling can be deregulated in human cancers.

RhoE is required for contact inhibition and negatively regulates tumor initiation and progression

RhoE is a small GTPase involved in the regulation of actin cytoskeleton dynamics, cell cycle and apoptosis. The role of RhoE in cancer is currently controversial, with reports of both oncogenic and tumor-suppressive functions for RhoE. Using RhoE-deficient mice, we show here that the absence of RhoE blunts contact-inhibition of growth by inhibiting p27Kip1 nuclear translocation and cooperates in oncogenic transformation of mouse primary fibroblasts. Heterozygous RhoE+/gt mice are more susceptible to chemically induced skin tumors and RhoE knock-down results in increased metastatic potential of cancer cells. These results indicate that RhoE plays a role in suppressing tumor initiation and progression.

Pathophysiological Functions of Rnd3/RhoE

Rnd3, also known as RhoE, belongs to the Rnd subclass of the Rho family of small guanosine triphosphate (GTP)-binding proteins. Rnd proteins are unique due to their inability to switch from a GTP-bound to GDP-bound conformation. Even though studies of the biological function of Rnd3 are far from being concluded, information is available regarding its expression pattern, cellular localization, and its activity, which can be altered depending on the conditions. The compiled data from these studies implies that Rnd3 may not be a traditional small GTPase. The basic role of Rnd3 is to report as an endogenous antagonist of RhoA signaling-mediated actin cytoskeleton dynamics, which specifically contributes to cell migration and neuron polarity. In addition, Rnd3 also plays a critical role in arresting cell cycle distribution, inhibiting cell growth, and inducing apoptosis and differentiation. Increasing data have shown that aberrant Rnd3 expression may be the leading cause of some systemic diseases; particularly highlighted in apoptotic cardiomyopathy, developmental arrhythmogenesis and heart failure, hydrocephalus, as well as tumor metastasis and chemotherapy resistance. Therefore, a better understanding of the function of Rnd3 under different physiological and pathological conditions, through the use of suitable models, would provide a novel insight into the origin and treatment of multiple human diseases.

Identification of CEACAM5 as a Biomarker for Prewarning and Prognosis in Gastric Cancer

MGd1, a monoclonal antibody raised against gastric cancer cells, possesses a high degree of specificity for gastric cancer (GC). Here we identified that the antigen of MGd1 is CEACAM5, and used MGd1 to investigate the expression of CEACAM5 in non-GC and GC tissues (N=643), as a biomarker for prewarning and prognosis. The expression of CEACAM5 was detected by immunohistochemistry in numerous tissues; its clinicopathological correlation was statistically analyzed. CEACAM5 expression was increased progressively from normal gastric mucosa to chronic atrophic gastritis, intestinal metaplasia, dysplasia and finally to GC (p<0.05). In gastric precancerous lesions (intestinal metaplasia and dysplasia), CEACAM5-positive patients had a higher risk of developing GC as compared with CEACAM5-negative patients (OR = 12.68, p<0.001). Besides, CEACAM5 was found positively correlated with invasion depth of gastric adenocarcinoma (p<0.001). In survival analysis, CEACAM5 was demonstrated to be an independent prognostic predictor for patients with GC of clinical stage IIIA/IV (p=0.033). Our results demonstrate that CEACAM5 is a promising biomarker for GC prewarning and prognostic evaluation.

MicroRNA-338 inhibits migration and proliferation by targeting hypoxia-induced factor 1α in nasopharyngeal carcinoma

Nasopharyngeal cancer (NPC) is an endemic type of head and neck cancer with a high rate of cervical lymph node metastasis. An increasing number of studies have shown that microRNAs (miRNAs) play a key role in the development and progression of NPC. miR-338-3p has been demonstrated as an anti-oncogene in different solid tumors. The aim of the present study was to investigate the potential role of miR‑338-3p in the development and progression of NPC. Compared with normal samples, our data showed that miR-338-3p were downregulated in NPC tissues and cells. The luciferase assay demonstrated that HIF-1α was a direct target of miR-338-3p. We also found that miR-338-3p regulated the expression levels of HIF-1α, respectively. Overexpression of miR-338-3p in NPC cells significantly inhibited cell proliferation, and migration. Conversely, miR-338-3p knockdown in cells with lower endogenous expression levels significantly reduced antitumor behavior. Furthermore, enforced expression of miR-338-3p led to a decline in ERK phosphorylation as well as inhibited the hypoxia induced epithelial to mesenchymal transition. Cells pre-transfected with miR-338-3p can overcome hypoxia-mediated cisplatin resistance. Taken together, we found that miR-338-3p directly targeted HIF-1α, and we provide insight into NPC initiation and progression, possibly representing a novel therapeutic target.

MIR210 as a potential molecular target to block invasion and metastasis of gastric cancer

The epithelial-mesenchymal transition (EMT) is a process driving invasion, recurrence, and metastasis of gastric cancer, and EMT is triggered by specific physiological factors that arise during tumorigenesis, such as hypoxia. Identifying the molecular mechanisms underlying EMT will potentially yield insight into the pathways fueling cancer recurrence and metastasis and thus, lead to novel molecular targets that will improve treatment of the disease. The microRNA210 (MIR210) is such a candidate molecule mediating EMT in gastric cancer based on a number of observations. First, MIR210 is often highly overexpressed in gastric cancer. Second, MIR210 is a hypoxia-specific miRNA, and its expression is significantly increased in hypoxic environments where EMT develops. Third, MIR210 is regulated by hypoxia inducible factor 1α (HIF-1α), a key transcription factor mediating important tumor associated processes such as EMT and angiogenesis in response to hypoxia during tumorigenesis. Finally, MIR210 has been intriguingly associated with Helicobacterpylori infection, which typically develops in an anaerobic environment and is known to have a causal role in the development of gastric cancer. Although studies have shown that MIR210 is often highly expressed in gastric cancer and associated with specific pathological conditions, functional experiments have not yet been performed to determine the role of MIR210 and downstream mediators in the development and progression of gastric cancer. Here, MIR210 is proposed as a viable molecular target in the treatment of gastric cancer, specifically for the inhibition of invasion and metastasis.

Function and regulation of Rnd proteins in cortical projection neuron migration

The mammalian cerebral cortex contains a high variety of neuronal subtypes that acquire precise spatial locations and form long or short-range connections to establish functional neuronal circuits. During embryonic development, cortical projection neurons are generated in the areas lining the lateral ventricles and they subsequently undergo radial migration to reach the position of their final maturation within the cortical plate. The control of the neuroblast migratory behavior and the coordination of the migration process with other neurogenic events such as cell cycle exit, differentiation and final maturation are crucial to normal brain development. Among the key regulators of cortical neuron migration, the small GTP binding proteins of the Rho family and the atypical Rnd members play important roles in integrating intracellular signaling pathways into changes in cytoskeletal dynamics and motility behavior. Here we review the role of Rnd proteins during cortical neuronal migration and we discuss both the upstream mechanisms that regulate Rnd protein activity and the downstream molecular pathways that mediate Rnd effects on cell cytoskeleton.

Hypoxic Microenvironment Induces EMT and Upgrades Stem-Like Properties of Gastric Cancer Cells

Hypoxia microenvironment, as a major feature of solid tumors, increases tumors progression and metastasis. To research whether hypoxia influences the epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) of gastric cancer cells and their cell biological behaviors. Human gastric cancer cell lines BGC823 and SGC7901 were cultivated in different oxygen tensions for proliferation, colony formation, soft agar formation, migration, and invasion analyses. Markers of EMT (E-cadherin, N-cadherin, Vimentin, and Snail) and markers of CSCs (Sox2, Oct4, and Bmi1) were investigated by real-time polymerase chain reaction, Western blotting, and immunofluorescent analysis. Cultivated at hypoxic condition, BGC823 and SGC7901 cells morphology began to change significantly. The cells pretreated under hypoxia grew faster than those cells always cultivated in normoxia. Meanwhile, hypoxia pretreatment dramatically promoted cell proliferation, migration and invasion, and increased capability of colony and soft agar colony formation. Furthermore, under hypoxia, E-cadherin decreased and N-cadherin, Vimentin, Snail, Sox2, Oct4, and Bmi1 increased both on the level of messenger RNA and protein. We drew a conclusion that the hypoxic microenvironment induced EMT, upgraded stem-like properties of gastric cancer cells, promoted invasion and metastasis, and behaved more malignantly.

Rho/ROCK signaling in motility and metastasis of gastric cancer

Gastric cancer is one of the most frequent and lethal malignancies worldwide because of high frequency of metastasis. Tumor cell motility and invasion play fundamental roles in cancer metastasis. Recent studies have revealed that the Rho/Rho-associated protein kinases (ROCK) pathway plays a critical role in the regulation of cancer cell motility and invasion. In addition, the Rho/ROCK pathway plays important roles in invasion and metastasis on the basis of its predominant function of cell cytoskeletal regulation in gastric cancer. According to the current understanding of tumor motility, there are two modes of tumor cell movement: mesenchymal and amoeboid. In addition, cancer cell movement can be interchangeable between the mesenchymal and amoeboid movements under certain conditions. Control of cell motility through the actin cytoskeleton creates the potential for regulating tumor cell metastasis. In this review we discuss Rho GTPases and ROCK signaling and describe the mechanisms of Rho/ROCK activity with regard to motility and metastasis in gastric cancer. In addition, we provide an insight of the therapeutic potential of targeting the Rho/ROCK pathway.

Reduction of TIP30 in esophageal squamous cell carcinoma cells involves promoter methylation and microRNA-10b

TIP30 is a putative tumor suppressor that can promote apoptosis and inhibit angiogenesis. However, the role of TIP30 in esophageal squamous cell carcinoma (ESCC) biology has not been investigated. Immunohistochemistry was used to investigate the expression of TIP30 in 70 ESCC. Hypermethylation of TIP30 was evaluated by the methylation specific PCR (MSP) method in ESCC (tumor and paired adjacent non-tumor tissues). Lost expression of TIP30 was observed in 50 of 70 (71.4%) ESCC. 61.4% (43 of 70) of primary tumors analyzed displayed TIP30 hypermethylation, indicating that this aberrant characteristic is common in ESCC. Moreover, a statistically significant inverse association was found between TIP30 methylation status and expression of the TIP30 protein in tumor tissues (p=0.001). We also found that microRNA-10b (miR-10b) targets a homologous DNA region in the 3'untranslated region of the TIP30 gene and represses its expression at the transcriptional level. Reporter assay with 3'UTR of TIP30 cloned downstream of the luciferase gene showed reduced luciferase activity in the presence of miR-10b, providing strong evidence that miR-10b is a direct regulator of TIP30. These results suggest that TIP30 expression is regulated by promoter methylation and miR-10b in ESCC.

Overexpression of Oct4 suppresses the metastatic potential of breast cancer cells via Rnd1 downregulation

Although Oct4 is known as a critical transcription factor involved in maintaining "stemness", its role in tumor metastasis is still controversial. Herein, we overexpressed and silenced Oct4 expression in two breast cancer cell lines, MDA-MB-231 and 4T1, separately. Our data showed that ectopic overexpression of Oct4 suppressed cell migration and invasion in vitro and the formation of metastatic lung nodules in vivo. Conversely, Oct4 downregulation increased the metastatic potential of breast cancer cells both in vitro and in vivo. Furthermore, we identified Rnd1 as the downstream target of Oct4 by ribonucleic acid sequencing (RNA-seq) analysis, which was significantly downregulated upon Oct4 overexpression. Chromatin immunoprecipitation assays revealed the binding of Oct4 to the promoter region of Rnd1 by ectopic overexpression of Oct4. Dual luciferase assays indicated that Oct4 overexpression suppressed transcriptional activity of the Rnd1 promoter. Moreover, overexpression of Rnd1 partially rescued the inhibitory effects of Oct4 on the migration and invasion of breast cancer cells. Overexpression of Rnd1 counteracted the influence of Oct4 on the formation of cell adhesion and lamellipodia, which implied a potential underlying mechanism involving Rnd1. In addition, we also found that overexpression of Oct4 led to an elevation of E-cadherin expression, even in 4T1 cells that possess a relatively high basal level of E-cadherin. Rnd1 overexpression impaired the promoting effects of Oct4 on E-cadherin expression in MDA-MB-231 cells. These results suggest that Oct4 affects the metastatic potential of breast cancer cells through Rnd1-mediated effects that influence cell motility and E-cadherin expression.

Small Rho GTPases in the control of cell shape and mobility

Rho GTPases are a class of evolutionarily conserved proteins comprising 20 members, which are predominantly known for their role in regulating the actin cytoskeleton. They are primarily regulated by binding of GTP/GDP, which is again controlled by regulators like GEFs, GAPs, and RhoGDIs. Rho GTPases are thus far well known for their role in the regulation of actin cytoskeleton and migration. Here we present an overview on the role of Rho GTPases in regulating cell shape and plasticity of cell migration. Finally, we discuss the emerging roles of ubiquitination and sumoylation in regulating Rho GTPases and cell migration.

RhoE promotes metastasis in gastric cancer through a mechanism dependent on enhanced expression of CXCR4

RhoE, a novel member of the Rho protein family, is a key regulator of the cytoskeleton and cell migration. Our group has previously shown that RhoE as a direct target for HIF-1α and mediates hypoxia-induced epithelial to mesenchymal transition in gastric cancer cells. Therefore, we assumed that RhoE might play an important role in gastric cancer metastasis. In the present study, we have explored the role of RhoE expression in gastric cancer, cell invasion and metastasis, and the influence of RhoE on regulating the potential expression of down-stream genes. RhoE expression was elevated in gastric cancer tissues as compared with normal gastric tissues. We also found a close correlation between the histological grade and the diagnosis of the patient. Up-regulation of RhoE significantly enhanced the migratory and invasive abilities of gastric cancer cells both in vitro and in vivo. Moreover, down-regulation of RhoE diminished the metastatic potential of cancer cells. PCR array and subsequent transwell assay showed that the regulation of gastric cancer metastasis by RhoE was partially mediated by CXCR4. This observation suggested that CXCR4 might be a downstream effector for RhoE. In summary, our study identified RhoE as a novel prognostic biomarker and metastatic-promoting gene of gastric cancer.

Overexpression of the HIF hydroxylase PHD3 is a favorable prognosticator for gastric cancer

Hypoxia-induced factors (HIFs) play a central role in the adaptive mechanisms of cancer cells to survive under conditions of hypoxia. HIFs are regulated by prolyl hydroxylases (PHDs) among which PHD3 is implicated as a tumor suppressor. We aimed to correlate PHD3 expression with clinicopathologic parameters and to evaluate its prognostic significance in gastric cancer. The 101 tissue samples were collected from 83 resected stages I–IV gastric cancer patients, which were grouped as non-cancerous mucosa (n=18) and primary carcinoma (n=83). PHD3 expression was evaluated by immunohistochemistry. We adopted Pearson chi-square test, univariate analysis, multivariate analysis and Kaplan–Meier method. The positive frequency of PHD3 in cancer cells was 42.2%, whereas non-cancerous mucosa had no detectable PHD3. The expression of PHD3 increased significantly from non-cancerous mucosa to cancer. A significant difference was observed between PHD3 expression and tumor differentiation (P=0.007). The overexpression of PHD3 was associated with well differentiation. In univariate analyses, American Joint Committee on Cancer (AJCC) stage (P<0.0001), pT classification (P<0.0001), pN classification (P<0.0001), differentiation (P=0.0121), peritoneal metastasis (P=0.0006) and gross features (P=0.0104) were significantly associated with survival except PHD3 (P=0.2228) (Table 3). In multivariate analysis, AJCC stage was prognostically independent [hazard ratio (HR), 3.078; 95% confidence interval (CI), 2.228–4.252; P<0.0001]. Overexpression of PHD3 is a favorable prognosticator for gastric cancer. AJCC stage is an independent prognostic factor of gastric cancer.

Hypoxia-induced invadopodia formation: a role for β-PIX

During tumour progression, oxygen tension in the microenvironment surrounding tumour cells is reduced, resulting in hypoxia. It is well established that cancer cells resist the negative effects of hypoxia by inducing angiogenesis predominantly via the activity of transcription factor hypoxia-inducible factor-1 (HIF-1). However, more recently HIF-1α has also been linked to increased invasive potential, although the molecular mechanisms remain to be defined. Invasive cancer cells are thought to employ membrane protrusions, termed invadopodia, to achieve matrix degradation. While many invadopodia components have been identified, signalling pathways that link extracellular stimuli to invadopodia formation remain largely unknown. Indeed, the relationship between invadopodia formation and HIF-1α has not been explored. We now report that HIF-1α is a driver of invadopodia formation. Furthermore, we have identified an important, direct and novel link between the Rho family activator β-PIX, HIF-1α and invadopodia formation. Indeed, we find that β-PIX expression is essential for invadopodia formation. In conclusion, we identify a new HIF-1α mechanistic pathway and suggest that β-PIX is a novel downstream signalling mediator during invadopodia formation.

Wnt/β-catenin signaling enhances hypoxia-induced epithelial-mesenchymal transition in hepatocellular carcinoma via crosstalk with hif-1α signaling

Epithelial-mesenchymal transition (EMT) is a critical process for tumor invasion and metastasis. Hypoxia may induce EMT, and upregulated β-catenin expression has been found in various tumors. In this study, we investigate the role of β-catenin in hypoxia-induced EMT in hepatocellular carcinoma (HCC). Induction of EMT in HCC cell lines by hypoxia was confirmed by altered morphology, expression change of EMT-associated markers and enhanced invasion capacity. We showed that hypoxia-induced EMT could be enhanced by addition of recombinant Wnt3a while it was repressed by β-catenin small interfering RNA. An interaction between β-catenin and hypoxia-induced factor-1α (hif-1α) was found, and an underlying competition for β-catenin between hif-1α and T-cell factor-4 was implied. Notably, increased hif-1α activity was accompanied with more significant EMT features. We also showed that the pro-EMT effect of β-catenin in hypoxia was deprived in the absence of hif-1α. Moreover, β-catenin was found to be responsible for the maintenance of viability and proliferation for tumor cells undergoing hypoxia. We further showed a correlation between hif-1α and β-catenin expression, and corresponding expression of EMT-associated markers in human HCC tissues. Our results suggest that Wnt/β-catenin signaling enhances hypoxia-induced EMT in HCC by increasing the EMT-associated activity of hif-1α and preventing tumor cell death.

Rho-associated coiled-coil kinase (ROCK) signaling and disease

The small Rho GTPase family of proteins, encompassing the three major G-protein classes Rho, Rac and cell division control protein 42, are key mitogenic signaling molecules that regulate multiple cancer-associated cellular phenotypes including cell proliferation and motility. These proteins are known for their role in the regulation of actin cytoskeletal dynamics, which is achieved through modulating the activity of their downstream effector molecules. The Rho-associated coiled-coil kinase 1 and 2 (ROCK1 and ROCK2) proteins were the first discovered Rho effectors that were primarily established as players in RhoA-mediated stress fiber formation and focal adhesion assembly. It has since been discovered that the ROCK kinases actively phosphorylate a large cohort of actin-binding proteins and intermediate filament proteins to modulate their functions. It is well established that global cellular morphology, as modulated by the three cytoskeletal networks: actin filaments, intermediate filaments and microtubules, is regulated by a variety of accessory proteins whose activities are dependent on their phosphorylation by the Rho-kinases. As a consequence, they regulate many key cellular functions associated with malignancy, including cell proliferation, motility and viability. In this current review, we focus on the role of the ROCK-signaling pathways in disease including cancer.

Suppression of RND3 activity by AES downregulation promotes cancer cell proliferation and invasion

Amino-terminal enhancer of split (AES) is a member of the Groucho/TLE family. Although it has no DNA-binding site, AES can regulate transcriptional activity by interacting with transcriptional factors. Emerging evidence indicates that AES may play an important role in tumor metastasis, but the molecular mechanism is still poorly understood. In this study, we found that knockdown of AES by RNA interference (RNAi) downregulated RND3 expression at the mRNA and protein levels in MDA-MB-231 and HepG2, two cancer cell lines. Furthermore, luciferase assays showed that overexpression of AES significantly enhanced RND3 promoter activity. Moreover, inhibition of AES both in MDA-MB-231 and HepG2 cells by RNAi significantly promoted cell proliferation, cell cycle progression and invasion, consistent with the effects of RNAi-mediated RND3 knockdown in these cells. For the first time, data are presented showing that alteration of the malignant behavior of cancer cells by AES is related to RND3 regulation, and these findings also provide new insights into the mechanism of AES action in regulating tumor malignancy.

RhoE is frequently down-regulated in hepatocellular carcinoma (HCC) and suppresses HCC invasion through antagonizing the Rho/Rho-kinase/myosin phosphatase target pathway

Deregulation of Rho guanosine triphosphatase (GTPase) pathways plays an important role in tumorigenesis and metastasis of hepatocellular carcinoma (HCC). RhoE/Rnd3 belongs to an atypical subfamily of the RhoGTPase, the Rnd family, as it lacks the intrinsic GTPase activity and remains always in its active GTP-bound form. In this study we investigated the role of RhoE in HCC. We examined the expression of RhoE in primary HCC samples from patients predominantly infected with the hepatitis B virus (HBV) and found that the RhoE messenger RNA (mRNA) level was frequently down-regulated (83.1%, 59/71) in HCCs. Low expression of RhoE in the tumors was significantly associated with shorter disease-free survival (P = 0.020) of the patients. Knockdown of RhoE by short-hairpin RNA using a lentiviral approach led to increased cell motility and invasiveness in SMMC7721 and BEL7402 HCC cells. Moreover, in vivo an orthotopic liver injection model in nude mice further demonstrated that knockdown of RhoE enhanced local invasion of HCC cells in the livers, with more invasive tumor front and increased incidence of venous invasion. Mechanistically, stable knockdown of RhoE in HCC cells significantly enhanced the phosphorylation of myosin phosphatase, promoted assembly of stress fibers, and increased the formation of plasma membrane blebbings, all these changes and activities being associated with activation of the Rho/Rho-kinase (ROCK) pathway.

CONCLUSION

RhoE was frequently down-regulated in predominantly HBV-associated HCCs and this down-regulation was associated with a more aggressive HCC phenotype. RhoE regulated the cytoskeleton remodeling and suppressed HCC motility and invasiveness by way of inhibiting the Rho/ROCK axis.

Hypoxia-regulated target genes implicated in tumor metastasis

Hypoxia is an important microenvironmental factor that induces cancer metastasis. Hypoxia/hypoxia-inducible factor-1α (HIF-1α) regulates many important steps of the metastatic processes, especially epithelial-mesenchymal transition (EMT) that is one of the crucial mechanisms to cause early stage of tumor metastasis. To have a better understanding of the mechanism of hypoxia-regulated metastasis, various hypoxia/HIF-1α-regulated target genes are categorized into different classes including transcription factors, histone modifiers, enzymes, receptors, kinases, small GTPases, transporters, adhesion molecules, surface molecules, membrane proteins, and microRNAs. Different roles of these target genes are described with regards to their relationship to hypoxia-induced metastasis. We hope that this review will provide a framework for further exploration of hypoxia/HIF-1α-regulated target genes and a comprehensive view of the metastatic picture induced by hypoxia.

RhoE is associated with relapse and prognosis of patients with colorectal cancer

BACKGROUND

RhoE, an atypical Rho protein, is differently deregulated in some solid tumors, and there are conflicting data describing the role of RhoE in tumor cell migration and invasion. This study aimed to investigate RhoE expression in human colorectal cancer and its relationship with clinicopathological features and prognosis.

METHODS

Colorectal cancer and adjacent normal tissues from 202 patients were examined by immunohistochemistry. Staining evaluation results were analyzed statistically in relation to various clinicopathological parameters, disease-free survival, and overall survival. RhoE expression was also investigated by immunohistochemistry in 80 node metastases and the corresponding primary lesions, and by Western blot test in six cancer and adjacent normal tissues. The relationship between RhoE and invasion was examined by transwell assay and Western blot test.

RESULTS

The positive rate for RhoE in colorectal cancer was significantly higher than that of normal colorectal tissues. In colorectal cancer, RhoE expression was significantly correlated with depth of invasion, lymph node metastasis, and distant metastasis. Consistently, overexpression of RhoE in SW620 cells up-regulated vimentin, down-regulated E-cadherin, increased the expression of matrix metalloproteinase (MMP) 9, and enhanced cell invasion in vitro; in contrast, silencing of RhoE by a specific siRNA caused opposite effects. Most importantly, disease-free and overall survivals were significantly poorer for patients with RhoE-positive tumors than for those with RhoE-negative tumors.

CONCLUSIONS

These findings emphasize the positive role of RhoE in invasion and metastasis in human colorectal cancer. It could also serve as an independent prognostic marker in addition to the tumor, node, metastasis staging system.