RhoGDI2 antagonizes ovarian carcinoma growth, invasion and metastasis

Hyperglycemic Stress Induces Expression, Degradation, and Nuclear Association of Rho GDP Dissociation Inhibitor 2 (RhoGDIβ) in Pancreatic β-Cells

Small G proteins (e.g., Rac1) play critical regulatory roles in islet β-cell function in health (physiological insulin secretion) and in metabolic stress (cell dysfunction and demise). Multiple regulatory factors for these G proteins, such as GDP dissociation inhibitors (GDIs), have been implicated in the functional regulation of these G proteins. The current set of investigations is aimed at understanding impact of chronic hyperglycemic stress on the expression and subcellular distribution of three known isoforms of RhoGDIs (RhoGDIα, RhoGDIβ, and RhoGDIγ) in insulin-secreting β-cells. The data accrued in these studies revealed that the expression of RhoGDIβ, but not RhoGDIα or RhoGDIγ, is increased in INS-1 832/13 cells, rat islets, and human islets. Hyperglycemic stress also promoted the cleavage of RhoGDIβ, leading to its translocation to the nuclear compartment. We also report that RhoGDIα, but not RhoGDIγ, is associated with the nuclear compartment. However, unlike RhoGDIβ, hyperglycemic conditions exerted no effects on RhoGDIα's association with nuclear fraction. Based on these observations, and our earlier findings of the translocation of Rac1 to the nuclear compartment under the duress of metabolic stress, we conclude that the RhoGDIβ-Rac1 signaling module promotes signals from the cytosolic to the nucleus, culminating in accelerated β-cell dysfunction under metabolic stress.

Differential functions of RhoGDIβ in malignant transformation and progression of urothelial cell following N-butyl-N-(4-hydmoxybutyl) nitrosamine exposure

BACKGROUND

Functional role of Rho GDP-dissociation inhibitor beta (RhoGDIβ) in tumor biology appears to be contradictory across various studies. Thus, the exploration of the molecular mechanisms underlying the differential functions of this protein in urinary bladder carcinogenesis is highly significant in the field. Here, RhoGDIβ expression patterns, biological functions, and mechanisms leading to transformation and progression of human urothelial cells (UROtsa cells) were evaluated following varying lengths of exposure to the bladder carcinogen N-butyl-N-(4-hydmoxybutyl) nitrosamine (BBN).

RESULTS

It was seen that compared to expression in vehicle-treated control cells, RhoGDIβ protein expression was downregulated after 2-month of BBN exposure, but upregulated after 6-month of exposure. Assessments of cell function showed that RhoGDIβ inhibited UROtsa cell growth in cells with BBN for 2-month exposure, whereas it promoted the invasion of cells treated with BBN for 6 months. Mechanistic studies revealed that 2-month of BBN exposure markedly attenuated DNMT3a abundance, and this led to reduced miR-219a promoter methylation, increased miR-219a binding to the RhoGDIβ mRNA 3'UTR, and reduced RhoGDIβ protein translation. While after 6-mo of BBN treatment, the cells showed increased PP2A/JNK/C-Jun axis phosphorylation and this in turn mediated overall RhoGDIβ mRNA transcription and protein expression as well as invasion.

CONCLUSIONS

These findings indicate that RhoGDIβ is likely to inhibit the transformation of human urothelial cells during the early phase of BBN exposure, whereas it promotes invasion of the transformed/progressed urothelial cells in the late stage of BBN exposure. The studies also suggest that RhoGDIβ may be a useful biomarker for evaluating the progression of human bladder cancers.

The Dual Function of RhoGDI2 in Immunity and Cancer

RhoGDI2 is a guanine nucleotide dissociation inhibitor (GDI) specific for the Rho family of small GTPases. It is highly expressed in hematopoietic cells but is also present in a large array of other cell types. RhoGDI2 has been implicated in multiple human cancers and immunity regulation, where it can display a dual role. Despite its involvement in various biological processes, we still do not have a clear understanding of its mechanistic functions. This review sheds a light on the dual opposite role of RhoGDI2 in cancer, highlights its underappreciated role in immunity and proposes ways to explain its intricate regulatory functions.

FHL1 Overexpression as A Inhibitor of Lung Cancer Cell Invasion via Increasing RhoGDIß mRNA Expression

Objective

Four and a half Lin-11, Isl-1, Mac-3 (LIM) protein 1 (FHL1) is one of the FHL protein family, which is regarded as a tumor suppressor in the multiple malignant tumors. In this study, we aimed to explore the regulatory effects and mechanisms of FHL1 on lung cancer cell invasion.

Materials and Methods

In this experimental study, bioinformatics analysis of FHL1 transcripts in human lung adenocarcinomas of TCGA database was performed. Quantitative real-time polymerase chain reaction (PCR) was performed to detect FHL1 mRNA expression in 15 paired human lung cancer tissues and their adjacent normal lung tissues, or lung cancer cell lines (A549 and H1299) in comparison with human bronchial epithelial cell line (Beas- 2B). Moreover, western blot was used to analyze FHL1 and rho GDP-dissociation inhibitor beta (RhoGDIβ) protein expression in the indicated cell lines. Also, transwell assays were employed to measure the migrated, and invaded of indicated cell lines.

Results

FHL1 transcripts were downregulated in the human lung adenocarcinoma. The impaired FHL1 transcripts were positively correlated with advanced tumor node metastasis (TNM) stage. Moreover, as compared to the adjacent normal lung tissues, FHL1 mRNA was low expressed in 15 paired human lung cancer tissues than their adjacent normal lung tissues. Besides, FHL1 mRNA and protein expression were also reduced in H1299 and A549 cell lines in comparison with Beas-2B cell line. Overexpressed FHL1 protein inhibited the invasive ability of H1299 and A549 cell lines. Mechanically, FHL1 protein overexpression increased the RhoGDIβ protein and mRNA abundance, while knockdown of RhoGDIβ protein, completely restored the invasion ability of A549 (Flag-FHL1) cell line.

Conclusion

Our findings indicated that as a key FHL1 downstream regulator, RhoGDIβ is in charge of FHL1 inhibiting lung cancer cell invasion abilities, providing a critical insight into understanding the role of FHL1 for lung cancer development.

CRIF1 deficiency suppresses endothelial cell migration via upregulation of RhoGDI2

Rho GDP-dissociation inhibitor (RhoGDI), a downregulator of Rho family GTPases, prevents nucleotide exchange and membrane association. It is responsible for the activation of Rho GTPases, which regulate a variety of cellular processes, such as migration. Although RhoGDI2 has been identified as a tumor suppressor gene involved in cellular migration and invasion, little is known about its role in vascular endothelial cell (EC) migration. CR6-interacting factor 1 (CRIF1) is a CR6/GADD45-interacting protein with important mitochondrial functions and regulation of cell growth. We examined the expression of RhoGDI2 in CRIF1-deficient human umbilical vein endothelial cells (HUVECs) and its role in cell migration. Expression of RhoGDI2 was found to be considerably higher in CRIF1-deficient HUVECs along with suppression of cell migration. Moreover, the phosphorylation levels of Akt and CREB were decreased in CRIF1-silenced cells. The Akt-CREB signaling pathway was implicated in the changes in endothelial cell migration caused by CRIF1 downregulation. In addition to RhoGDI2, we identified another factor that promotes migration and invasion of ECs. Adrenomedullin2 (ADM2) is an autocrine/paracrine factor that regulates vascular tone and other vascular functions. Endogenous ADM2 levels were elevated in CRIF1-silenced HUVECs with no effect on cell migration. However, siRNA-mediated depletion of RhoGDI2 or exogenous ADM2 administration significantly restored cell migration via the Akt-CREB signaling pathway. In conclusion, RhoGDI2 and ADM2 play important roles in the migration of CRIF1-deficient endothelial cells.

Binding of the Andes Virus Nucleocapsid Protein to RhoGDI Induces the Release and Activation of the Permeability Factor RhoA

Andes virus (ANDV) nonlytically infects pulmonary microvascular endothelial cells (PMECs), causing acute pulmonary edema termed hantavirus pulmonary syndrome (HPS). In HPS patients, virtually every PMEC is infected; however, the mechanism by which ANDV induces vascular permeability and edema remains to be resolved. The ANDV nucleocapsid (N) protein activates the GTPase RhoA in primary human PMECs, causing VE-cadherin internalization from adherens junctions and PMEC permeability. We found that ANDV N protein failed to bind RhoA but coprecipitates RhoGDI (Rho GDP dissociation inhibitor), the primary RhoA repressor that normally sequesters RhoA in an inactive state. ANDV N protein selectively binds the RhoGDI C terminus (residues 69 to 204) but fails to form ternary complexes with RhoA or inhibit RhoA binding to the RhoGDI N terminus (residues 1 to 69). However, we found that ANDV N protein uniquely inhibits RhoA binding to an S34D phosphomimetic RhoGDI mutant. Hypoxia and vascular endothelial growth factor (VEGF) increase RhoA-induced PMEC permeability by directing protein kinase Cα (PKCα) phosphorylation of S34 on RhoGDI. Collectively, ANDV N protein alone activates RhoA by sequestering and reducing RhoGDI available to suppress RhoA. In response to hypoxia and VEGF-activated PKCα, ANDV N protein additionally directs the release of RhoA from S34-phosphorylated RhoGDI, synergistically activating RhoA and PMEC permeability. These findings reveal a fundamental edemagenic mechanism that permits ANDV to amplify PMEC permeability in hypoxic HPS patients. Our results rationalize therapeutically targeting PKCα and opposing protein kinase A (PKA) pathways that control RhoGDI phosphorylation as a means of resolving ANDV-induced capillary permeability, edema, and HPS. IMPORTANCE HPS-causing hantaviruses infect pulmonary endothelial cells (ECs), causing vascular leakage, pulmonary edema, and a 35% fatal acute respiratory distress syndrome (ARDS). Hantaviruses do not lyse or disrupt the endothelium but dysregulate normal EC barrier functions and increase hypoxia-directed permeability. Our findings reveal a novel underlying mechanism of EC permeability resulting from ANDV N protein binding to RhoGDI, a regulatory protein that normally maintains edemagenic RhoA in an inactive state and inhibits EC permeability. ANDV N sequesters RhoGDI and enhances the release of RhoA from S34-phosphorylated RhoGDI. These findings indicate that ANDV N induces the release of RhoA from PKC-phosphorylated RhoGDI, synergistically enhancing hypoxia-directed RhoA activation and PMEC permeability. Our data suggest inhibiting PKC and activating PKA phosphorylation of RhoGDI as mechanisms of inhibiting ANDV-directed EC permeability and therapeutically restricting edema in HPS patients. These findings may be broadly applicable to other causes of ARDS.

2-O-Octadecylascorbic acid represses RhoGDIβ expression and ameliorates DNA damage-induced abnormal spindle orientations

The appropriate regulation of spindle orientation maintains proper tissue homeostasis and avoids aberrant tissue repair or regeneration. Spindle misorientation due to imbalance or improper functioning leads to a loss of tissue integrity and aberrant growth, such as tissue loss or overgrowth. Pharmacological manipulation to prevent spindle misorientation will enable a better understanding of how spindle orientation is involved in physiological and pathological conditions and will provide therapeutic possibilities to treat patients associated with abnormal tissue function caused by spindle misorientation. N-terminal-deleted Rho guanine nucleotide dissociation inhibitor β (RhoGDIβ/RhoGDI2/LyGDI) produced by caspase-3 activation perturbs spindle orientation in surviving cells following exposure to either ionizing radiation or UVC. Thus, presumably, RhoGDIβ cleaved by caspase-3 activation acts as a determinant of radiation-induced spindle misorientation that promote aberrant tissue repair due to deregulation of directional organization of cell population and therefore becomes a potential target of drugs to prevent such response. The objective of this study was to screen and identify chemicals that suppress RhoGDIβ expression. We focused our attention on ascorbic acid (AA) derivatives because of their impact on the maintenance of skin tissue homeostasis. Here, we screened for AA derivatives that suppress RhoGDIβ expression in HeLa cells and identified a lipophilic derivative, 2-O-octadecylascorbic acid (2-OctadecylAA), as a novel RhoGDIβ inhibitor that ameliorated ionizing radiation-induced abnormal spindle orientations. Among all examined AA derivatives, which were also antioxidative, the inhibition activity was specific to 2-OctadecylAA. Therefore, this activity was not due to simple antioxidant properties. 2-OctadecylAA was previously shown to prevent hepatocellular carcinoma development. Our findings suggest that the anticarcinogenic effects of 2-OctadecylAA are partly due to RhoGDIβ inhibition mechanisms by which spindle orientation perturbations are attenuated. Thus, the molecular targeting features of RhoGDIβ warrant its further development for the treatment or control of spindle orientation abnormalities that affect epithelial homeostasis.

Brain Tumor Microenvironment and Angiogenesis in Melanoma Brain Metastases

BACKGROUND

High tumor-infiltrating lymphocytes (TILs) and hemorrhage are important prognostic factors in patients who have undergone craniotomy for melanoma brain metastases (MBM) before 2011 at the University of Pittsburgh Medical Center (UPMC). We have investigated the prognostic or predictive role of these histopathologic factors in a more contemporary craniotomy cohort from the University of North Carolina at Chapel Hill (UNC-CH). We have also sought to understand better how various immune cell subsets, angiogenic factors, and blood vessels may be associated with clinical and radiographic features in MBM.

METHODS

Brain tumors from the UPMC and UNC-CH patient cohorts were (re)analyzed by standard histopathology, tumor tissue imaging, and gene expression profiling. Variables were associated with overall survival (OS) and radiographic features.

RESULTS

The patient subgroup with high TILs in craniotomy specimens and subsequent treatment with immune checkpoint inhibitors (ICIs, n=7) trended to have longer OS compared to the subgroup with high TILs and no treatment with ICIs (n=11, p=0.059). Bleeding was significantly associated with tumor volume before craniotomy, high melanoma-specific expression of basic fibroblast growth factor (bFGF), and high density of CD31+αSMA- blood vessels. Brain tumors with high versus low peritumoral edema before craniotomy had low (17%) versus high (41%) incidence of brisk TILs. Melanoma-specific expression of the vascular endothelial growth factor (VEGF) was comparable to VEGF expression by TILs and was not associated with any particular prognostic, radiographic, or histopathologic features. A gene signature associated with gamma delta (gd) T cells was significantly higher in intracranial than same-patient extracranial metastases and primary melanoma. However, gdT cell density in MBM was not prognostic.

CONCLUSIONS

ICIs may provide greater clinical benefit in patients with brisk TILs in MBM. Intratumoral hemorrhage in brain metastases, a significant clinical problem, is not merely associated with tumor volume but also with underlying biology. bFGF may be an essential pathway to target. VEGF, a factor principally associated with peritumoral edema, is not only produced by melanoma cells but also by TILs. Therefore, suppressing low-grade peritumoral edema using corticosteroids may harm TIL function in 41% of cases. Ongoing clinical trials targeting VEGF in MBM may predict a lack of unfavorable impacts on TIL density and/or intratumoral hemorrhage.

RAS and RHO family GTPase mutations in cancer: twin sons of different mothers?

The RAS and RHO family comprise two major branches of the RAS superfamily of small GTPases. These proteins function as regulated molecular switches and control cytoplasmic signaling networks that regulate a diversity of cellular processes, including cell proliferation and cell migration. In the early 1980s, mutationally activated RAS genes encoding KRAS, HRAS and NRAS were discovered in human cancer and now comprise the most frequently mutated oncogene family in cancer. Only recently, exome sequencing studies identified cancer-associated alterations in two RHO family GTPases, RAC1 and RHOA. RAS and RHO proteins share significant identity in their amino acid sequences, protein structure and biochemistry. Cancer-associated RAS mutant proteins harbor missense mutations that are found primarily at one of three mutational hotspots (G12, G13 and Q61) and have been identified as gain-of-function oncogenic alterations. Although these residues are conserved in RHO family proteins, the gain-of-function mutations found in RAC1 are found primarily at a distinct hotspot. Unexpectedly, the cancer-associated mutations found with RHOA are located at different hotspots than those found with RAS. Furthermore, since the RHOA mutations suggested a loss-of-function phenotype, it has been unclear whether RHOA functions as an oncogene or tumor suppressor in cancer development. Finally, whereas RAS mutations are found in a broad spectrum of cancer types, RHOA and RAC1 mutations occur in a highly restricted range of cancer types. In this review, we focus on RHOA missense mutations found in cancer and their role in driving tumorigenesis, with comparisons to cancer-associated mutations in RAC1 and RAS GTPases.

Adenosine Inhibits Ovarian Cancer Growth Through Regulating RhoGDI2 Protein Expression

Objective

This study aimed to investigate the effect of adenosine (Ado) on the growth of ovarian cancer and to explore the related mechanisms.

Methods

The effect of Ado on the proliferation of A2780 human ovarian cancer cells was examined according to the MTT method. Moreover, the nude mouse model of subcutaneous A2780 xenograft was constructed, and then, Ado and cisplatin were administered intraperitoneally to investigate the effect of Ado on tumor growth in vivo. Immunohistochemistry (IHC) was carried out to study the effect of Ado on the expression of Rho-specific guanine nucleotide dissociation inhibitor 2 (RhoGDI2) in the subcutaneous xenografts. Afterwards, the commercially constructed RhoGDI2 siRNA plasmid was transfected into A2780 cells, and tube formation assay was conducted to determine the effect of down-regulating RhoGDI2 expression on the regulation of angiogenesis in ovarian cancer by Ado. Besides, Western blotting was performed to detect the effect of RhoGDI2 down-regulation on the regulation of matrix metalloproteinase 2 (MMP-2), MMP-9, vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β), tumor necrosis factor (TNF-α), and platelet endothelial cell adhesion molecule-1 (PECAM-1 or CD31) expression in ovarian cancer cells by Ado.

Results

The relative viability of cells subsequent to Ado treatment proved to be both concentration- and time dependent. IHC results showed that Ado evidently enhanced the RhoGDI2 protein expression. In addition, interference with RhoGDI2 outstandingly attenuated the ability of Ado to suppress tumor cell invasion and induce angiogenesis in vitro. Furthermore, molecular mechanism studies indicated that Ado remarkably inhibited the expression of MMP-2, MMP-9, VEGF, TGF-β, TNF-α, and CD31, while interference with RhoGDI2 restored the expression of the above-mentioned angiogenic factors.

Conclusion

Ado inhibits the growth of A2780 human ovarian cancer cells through inhibiting tumor cell invasion and angiogenesis in a RhoGDI2-dependent manner.

NFκB2 p52 stabilizes rhogdiβ mRNA by inhibiting AUF1 protein degradation via a miR-145/Sp1/USP8-dependent axis

Although overexpression of the non-canonical NFκB subunit p52 has been observed in several tumors, the function and mechanism of p52 in bladder cancer (BC) are less well understood. Here, we aimed at understanding the role and mechanism underlying p52 regulation of BC invasion. Human p52 was stably knockdown with shRNA targeting p52 in two bladder cancer cell lines (T24 and UMUC3). Two constitutively expressing constructs, p52 and p100, were stably transfected in to T24 or UMUC3, respectively. The stable transfectants were used to determine function and mechanisms responsible for p52 regulation of BC invasion. We demonstrate that p52 mediates human BC invasion. Knockdown of p52 impaired bladder cancer invasion by reduction of rhogdiβ mRNA stability and expression. Positively regulation of rhogdiβ mRNA stability was mediated by p52 promoting AUF1 protein degradation, consequently resulting in reduction of AUF1 binding to rhogdiβ mRNA. Further studies indicated that AUF1 protein degradation was mediated by upregulating USP8 transcription, which was modulated by its negative regulatory transcription factor Sp1. Moreover, we found that p52 upregulated miR-145, which directly bound to the 3'-UTR of sp1 mRNA, leading to downregulation of Sp1 protein translation. Our results reveal a comprehensive pathway that p52 acts as a positive regulator of BC invasion by initiating a novel miR-145/Sp1/USP8/AUF1/RhoGDIβ axis. These findings provide insight into the understanding of p52 in the pathology of human BC invasion and progression, which may be useful information in the development of preventive and therapeutic approaches for using p52 as a potential target.

XIAP overexpression promotes bladder cancer invasion in vitro and lung metastasis in vivo via enhancing nucleolin-mediated Rho-GDIβ mRNA stability

Our recent studies demonstrate that X-linked inhibitor of apoptosis protein (XIAP) is essential for regulating colorectal cancer invasion. Here, we discovered that RhoGDIβ was a key XIAP downstream effector mediating bladder cancer (BC) invasion in vitro and in vivo. We found that both XIAP and RhoGDIβ expressions were consistently elevated in BCs of N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN)-treated mice in comparison to bladder tissues from vehicle-treated mice and human BCs in comparison to the paired adjacent normal bladder tissues. Knockdown of XIAP attenuated RhoGDIβ expression and reduced cancer cell invasion, whereas RhoGDIβ expression was attenuated in BBN-treated urothelium of RING-deletion knockin mice. Mechanistically, XIAP stabilized RhoGDIβ mRNA by its positively regulating nucleolin mRNA stability via Erks-dependent manner. Moreover, ectopic expression of GFP-RhoGDIβ in T24T(shXIAP) cells restored its lung metastasis in nude mice. Our results demonstrate that XIAP-regulated Erks/nucleolin/RhoGDIβ axis promoted BC invasion and lung metastasis.

Unconventional myosin VIIA promotes melanoma progression

Unconventional myosin VIIA (Myo7a) is an actin-based motor molecule that normally functions in the cochlear hair cells of the inner ear. Mutations of MYO7A/Myo7a have been implicated in inherited deafness in both humans and mice. However, there is limited information about the functions of Myo7a outside of the specialized cells of the ears. Herein, we report a previously unidentified function of Myo7a by demonstrating that it plays an important role in melanoma progression. We found that silencing Myo7a by means of RNAi inhibited melanoma cell growth through upregulation of cell cycle regulator p21 (also known as CDKN1A) and suppressed melanoma cell migration and invasion through downregulation of RhoGDI2 (also known as ARHGDIB) and MMP9. Furthermore, Myo7a depletion suppressed melanoma cell metastases to the lung, kidney and bone in mice. In contrast, overexpression of Myo7a promoted melanoma xenograft growth and lung metastasis. Importantly, Myo7a levels are remarkably elevated in human melanoma patients. Collectively, we demonstrated for the first time that Myo7a is able to function in non-specialized cells, a finding that reveals the complicated disease-related roles of Myo7a, especially in melanomas.

Friend leukemia virus integration 1 activates the Rho GTPase pathway and is associated with metastasis in breast cancer

Breast cancer is the most prevalent malignant disease in women worldwide. In patients with breast cancer, metastasis to distant sites directly determines the survival outcome. However, the molecular mechanism underlying metastasis in breast cancer remains to be defined. In this report, we found that Friend leukemia virus integration 1 (FLI1) proto-oncogene was differentially expressed between the aggressive MDA-MB231 and the non-aggressive MCF-7 breast cancer cells. Congruently, immunohistochemical staining of clinical samples revealed that FLI1 was overexpressed in breast cancers as compared with the adjacent tissues. The abundance of FLI1 protein was strongly correlated with the advanced stage, poor differentiation, and lymph node metastasis in breast cancer patients. Knockdown of FLI1 with small interfering RNAs significantly attenuated the potential of migration and invasion in highly metastatic human breast cancer cells. FLI1 oncoprotein activated the Rho GTPase pathway that is known to play a role in tumor metastasis. This study for the first time identifies FLI1 as a clinically and functionally important target gene of metastasis, providing a rationale for developing FLI1 inhibitors in the treatment of breast cancer.

Pharmacodynamic study of 131I-labeled CA215 antibody on an animal model of estrogen-resistant OC-3-VGH ovarian cancer

The aim of the present study was to explore the inhibitory effect of ¹³¹I-labeled ovarian cancer antigen 215 (¹³¹I-CA215) antibody on human OC-3-VGH ovarian cancer. A subcutaneous transplanted tumor model of estrogen-resistant human OC-3-VGH ovarian cancer in nude mice was established. The model mice were randomly divided into seven groups, which were the negative control (NC), positive control (PC; 60 mg/kg cyclophosphamide), high-dose CA215 antibody (HA; 10 mg/kg), low-dose CA215 antibody (LA; 2 mg/kg), high-dose ¹³¹I-CA215 antibody (¹³¹I-HA; 10 mg/kg + 125 μCi), medium-dose ¹³¹I-CA215 antibody (¹³¹I-MA; 6 mg/kg + 75 μCi) and low-dose ¹³¹I-CA215 antibody (¹³¹I-LA; 2 mg/kg + 25 μCi) groups. Each group received intraperitoneal administration for 14 consecutive days. At 24 h after the final administration, the tumor was removed and weighed to calculate the tumor inhibition rate (TIR) and the relative tumor increase rate (T/C). Compared with the NC group, the HA group, as well as the ³¹I-HA and ¹³¹I-MA antibody groups, exhibited significantly inhibited tumor growth. The relative T/C values were 54, 30 and 48%, respectively, and the TIRs were 33.59, 64.89 and 45.80%, respectively. All differences were statistically significant. The difference between the HA and ¹³¹I-HA groups also presented statistical significance. CA215 and ¹³¹I-CA215 antibodies can markedly inhibit OC-3-VGH ovarian cancer. The high-dose ¹³¹I-CA215 antibody demonstrated a clear synergetic effect.

Expression of RhoGDI2 and 14-3-3σ in gastric carcinoma

AIM: To detect the expression of RhoGDI2 and 14-3-3σ in gastric cancer, analyze their correlation with clinicopathological characteristics of gastric cancer, and assess their correlation.

METHODS: Immunohistochemistry was used to detect the expression of RhoGDI2 and 14-3-3σ in 152 gastric cancer specimens.

RESULTS: The positive rates of RhoGDI2 and 14-3-3σ in gastric cancer were 76.97% and 27.63%, respectively. The expression of RhoGDI2 and 14-3-3σ was related with tumor differentiation, depth of invasion, lymph node metastasis, distant metastasis and TNM stage in gastric cancer. There was a negative correlation between the expression of RhoGDI2 and 14-3-3σ in gastric cancer.

CONCLUSION: There is a correlation between the expression of RhoGDI2 and 14-3-3σ in gastric cancer. 14-3-3σ is very likely regulated by RhoGDI2 and functions as a downstream target gene of RhoGDI2 in tumor invasion and metastasis. They may be both involved in regulating the invasion and metastasis of gastric cancer.

Hypoxia-Induced WSB1 Promotes the Metastatic Potential of Osteosarcoma Cells

Intratumoral hypoxia occurs in many solid tumors, where it is associated with the development of metastatic character. However, the connections between these phenomena are not fully understood. In this study, we define an integrative role for the E3 ubiquitin ligase subunit WSB1. In primary osteosarcomas, increased levels of WSB1 correlated with pulmonary metastatic potential. RNAi-mediated attenuation of WSB1 or disruption of its E3 ligase activity potently suppressed tumor metastasis. Quantitative proteomic and functional analyses revealed that WSB1 ubiquitylates the Rho-binding protein RhoGDI2 and promotes its proteasomal degradation, thereby activating Rac1 to stimulate tumor cell motility and invasion. Our findings show how WSB1 regulates key steps of the metastatic cascade in hypoxia-driven osteosarcoma, and they highlight a candidate therapeutic target to potentially improve the survival of patients with metastatic disease.

Expression of RhoGDI2 protein in gastric cancer promotes tumor invasion and metastasis

AIM: To detect the expression of RhoGTP enzymatic dissociation inhibitory factor 2 (RhoGDI2) in gastric cancer, and to explore the relationship between RhoGDI2 expression and invasion and metastasis of gastric cancer.

METHODS: Immunohistochemistry was used to detect the expression of RhoGDI2 protein in 127 pairs of gastric cancer and adjacent tissue specimens.

RESULTS: RhoGDI2 was expressed mainly in hematopoietic tissues (leukomonocytes, granulocytes, and macrophagocytes). RhoGDI2 was also expressed in gastric cancer, mainly in the cytoplasm of tumor cells. The positive rate of RhoGDI2 protien expression was significantly higher in gastric cancer than in normal gastric tissues (65.4% vs 0.00%, P < 0.05). RhoGDI2 expression in gastric cancer tissue in the low differentiation group was significantly higher than in the high and moderate differentiation group. The expression of RhoGDI2 protein in gastric cancer was significantly correlated with grade of differentiation (χ² = 9.702, P < 0.05), depth of invasion (χ² = 8.029, P < 0.05), lymph node metastasis (χ² = 18.53, P < 0.05), distant metastasis (χ² = 24.1, P < 0.05) and clinical stage (χ² = 8.530, P < 0.05). RhoGDI2 expression in gastric cancer was negatively correlated with gender (χ² = 0.126, P > 0.05), age (<60 years vs ≥60 years; χ² = 0.916, P > 0.05), and diameter of primary tumor (< 5 cm vs ≥ 5 cm; χ² = 2.620, P > 0.05).

CONCLUSION: The expression of RhoGDI2 has a positive correlation with the invasion and metastasis of gastric cancer, and RhoGDI2 may participate in the occurrence and development of gastric cancer.

Novel candidate key drivers in the integrative network of genes, microRNAs, methylations, and copy number variations in squamous cell lung carcinoma

The mechanisms of lung cancer are highly complex. Not only mRNA gene expression but also microRNAs, DNA methylation, and copy number variation (CNV) play roles in tumorigenesis. It is difficult to incorporate so much information into a single model that can comprehensively reflect all these lung cancer mechanisms. In this study, we analyzed the 129 TCGA (The Cancer Genome Atlas) squamous cell lung carcinoma samples with gene expression, microRNA expression, DNA methylation, and CNV data. First, we used variance inflation factor (VIF) regression to build the whole genome integrative network. Then, we isolated the lung cancer subnetwork by identifying the known lung cancer genes and their direct regulators. This subnetwork was refined by the Bayesian method, and the directed regulations among mRNA genes, microRNAs, methylations, and CNVs were obtained. The novel candidate key drivers in this refined subnetwork, such as the methylation of ARHGDIB and HOXD3, microRNA let-7a and miR-31, and the CNV of AGAP2, were identified and analyzed. On three large public available lung cancer datasets, the key drivers ARHGDIB and HOXD3 demonstrated significant associations with the overall survival of lung cancer patients. Our results provide new insights into lung cancer mechanisms.

RNA interference-mediated knockdown of RhoGDI2 induces the migration and invasion of human lung cancer A549 cells via activating the PI3K/Akt pathway

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been identified as a tumor suppressor gene for cellular migration and invasion. However, the underlying mechanism and effector targets of RhoGDI2 in lung cancer are still not fully understood. In this study, a vector-expressed small hairpin RNA (shRNA) of RhoGDI2 was transfected into the human lung cancer cell line A549. After the successful transfection, the down-regulation of RhoGDI2 promoted the proliferation, migration, and invasion of lung cancer cells in vitro through the increasing expression and activities of the matrix metallopeptidase 9 (MMP-9) and PI3K/Akt pathways. Transiently transfecting the small interfering RNA (siRNA) of MMP-9 into the RhoGDI2 shRNA cells reduced the MMP-9 expression. Both transfecting the siRNA and adding the MMP-9 antibody into the RhoGDI2 shRNA cells led to a decrease in the invasion and migration of the lung cancer cells. The blockade of the PI3K/Akt pathway by LY294002 resulted in abolishment of the effects of RhoGDI2 shRNA in Akt phosphorylation and MMP-9 expression. This result suggests that the down-regulated RhoGDI2 contributed to the migration and invasion of the lung cancer cell line via activating the PI3K/Akt pathway and the ensuing increase in the expression and activity of MMP-9. In conclusion, we report that the shRNA-mediated knockdown of RhoGDI2 induces the invasion and migration of lung cancer due to cross-talk with the PI3K/Akt pathway and MMP-9. Verifying the role and molecular mechanism of the participation of RhoGDI2 in the migration and invasion of lung cancer may provide a target for better treatment.

Expression of RhoGDI2 and CIAPIN1 in gastric carcinoma

AIM: To detect the expression of RhoGTPase dissociation inhibitor 2 (RhoGDI2) and cytokine-induced apoptosis inhibitor 1 (CIAPIN1) in gastric cancer and to analyze their clinical significance.

METHODS: Immunohistochemistry was used to detect the expression of RhoGDI2 and CIAPIN1 in 94 gastric cancer specimens.

RESULTS: The positive rates of RhoGDI2 and CIAPIN1 in gastric cancer were 67.02% and 77.66%, respectively. The expression of RhoGDI2 and CIAPIN1 was related to tumor differentiation, depth of invasion, lymph node metastasis, distant metastasis and TNM stage in gastric cancer. There was a positive correlation between the expression of RhoGDI2 and that of CIAPIN1.

CONCLUSION: The expression of RhoGDI2 is correlated with that of CIAPIN1 in gastric cancer. CIAPIN1 is very likely to be regulated by RhoGDI2, and functions as a downstream target gene of RhoGDI2 in tumor invasion and metastasis. Both of them may be involved in regulating the invasion and metastasis of gastric cancer.

Comparative proteomic profiling of triple-negative breast cancer reveals that up-regulation of RhoGDI-2 is associated to the inhibition of caspase 3 and caspase 9

There are no targeted therapeutic modalities for triple-negative breast cancer (TNBC), thus it is associated with poor prognosis and worst clinical outcome. Here, our aim was to identify deregulated proteins in TNBC with potential therapeutic applications. Proteomics profiling of TNBC and normal breast tissues through two-dimensional electrophoresis and ESI-MS/MS mass spectrometry revealed the existence of 16 proteins (RhoGDI-2, HSP27, SOD1, DJ1, UBE2N, PSME1, FTL, SH3BGRL, and eIF5A-1) with increased abundance in carcinomas. We also evidenced for the first time the deregulation of COX5, MTPN and DB1 proteins in TNBC that may represent novel tumor markers. Particularly, we confirmed the overexpression of the Rho-GDP dissociation inhibitor 2 (RhoGDI-2) in distinct breast cancer subtypes, as well as in metastatic cell lines derived from lung, prostate, and breast cancer. Remarkably, targeted disruption of RhoGDI-2 by RNA interference induced mitochondrial dysfunction, and facilitated caspase-3 and -9 activation in two breast cancer cell lines. Moreover, suppression of RhoGDI-2 resulted in a robust sensitization of breast cancer cells to cisplatin therapy. In conclusion, we identified novel proteins deregulated in TNBC, and confirmed the overexpression of RhoGDI-2. We propose that RhoGDI-2 inhibition may be exploited as a potential therapeutic strategy along cisplatin-based chemotherapy in breast cancer.

BIOLOGICAL SIGNIFICANCE

There are no useful biomarkers neither targeted therapeutic modalities for triple-negative breast cancer, which highly contributes to the poor prognosis of this breast cancer subtype. In this work, we used two-dimensional electrophoresis and ESI-MS/MS spectrometry to identify novel deregulated proteins in breast cancer tissues. Particularly, our results showed that RhoGDI-2, a protein that has been associated to metastasis and poor survival in human cancers, is overexpressed in different subtypes of breast tumors, as well as in metastatic cell lines derived from lung, prostate, and breast cancer. Our data also provided novel insights about the role of RhoGDI-2 in apoptosis through intrinsic pathway inhibition. Importantly, they suggested that targeted modulation of RhoGDI-2 levels might be a useful strategy for breast cancer therapy.

Lentivirus vector-mediated Rho guanine nucleotide dissociation inhibitor 2 induces beta-2 adrenergic receptor desensitization in β2AR desensitization mice model

BACKGROUND

It is well-known that chronic administration of β2AR agonists can induce β2AR desensitization. Our previous study showed that Rho guanine nucleotide dissociation inhibitor 2 (RhoGDI2) overexpression induced beta-2 adrenergic receptor (β2AR) desensitization in airway smooth muscle cells. The purpose of this study was to further study the function of RhoGDI2 in β2AR desensitization by β2AR desensitization mouse model.

METHODS

Studies were performed using a β2AR desensitization mice model induced by salbutamol. The mice were randomly divided into five groups (n=45): RhoGDI2 overexpression group (n=10); RhoGDI2 siRNA group (n=10); empty viral vector group (n=10); experimental control group (n=10); blank control group-without any drug treatment (n=5). The first four groups were used the same methods and the same dose to establish β2AR desensitization mice model by salbutamol. The first three groups that salbutamol-treated were used for intratracheal delivery of lentiviral vectors. Airway hyperreactivity was measured through a whole-body plethysmograph system. RhoGDI2, β2AR, GRK2 mRNA and protein expression levels were then detected by RT-PCR and western blot analyses in fresh lung tissues. As well as the activity of GRK was assessed by light-dependent phosphorylation of rhodopsin.

RESULTS

We successfully constructed β2AR desensitization mouse model. As expected, airway responsiveness after inhaling acetylcholine chloride (Ach) was markedly increased in the RhoGDI2 overexpression group compared to experimental control group and blank control group when concentrations of Ach was 45 mg/mL (all P<0.05), while, it was markedly decreased in the RhoGDI2 siRNA group compared to experimental control group (P<0.05). RhoGDI2, GRK2 expressions and GRK enzymatic activity were significantly increased in RhoGDI2 overexpression group compared to experimental control group and blank control group (all P<0.05). RhoGDI2, GRK2 expressions and GRK enzymatic activity were significantly decreased in RhoGDI2 siRNA group compared to experimental control group and blank control group (all P<0.05). Conversely, β2AR expression were significantly lower in RhoGDI2 overexpression group compared to experimental control group and blank control group (all P<0.05), exhibiting an inverse correlation with RhoGDI2 expression.

CONCLUSIONS

To sum up, our present studies found that RhoGDI2 might induce β2AR desensitization and GRK2 might take part in RhoGDI2-mediated β2AR desensitization.

The Role of Ect2 Nuclear RhoGEF Activity in Ovarian Cancer Cell Transformation

Ect2, a Rho guanine nucleotide exchange factor (RhoGEF), is atypical among RhoGEFs in its predominantly nuclear localization in interphase cells. One current model suggests that Ect2 mislocalization drives cellular transformation by promoting aberrant activation of cytoplasmic Rho family GTPase substrates. However, in ovarian cancers, where Ect2 is both amplified and overexpressed at the mRNA level, we observed that the protein is highly expressed and predominantly nuclear and that nuclear but not cytoplasmic Ect2 increases with advanced disease. Knockdown of Ect2 in ovarian cancer cell lines impaired their anchorage-independent growth without affecting their growth on plastic. Restoration of Ect2 expression rescued the anchorage-independent growth defect, but not if either the DH catalytic domain or the nuclear localization sequences of Ect2 were mutated. These results suggested a novel mechanism whereby Ect2 could drive transformation in ovarian cancer cells by acting as a RhoGEF specifically within the nucleus. Interestingly, Ect2 had an intrinsically distinct GTPase specificity profile in the nucleus versus the cytoplasm. Nuclear Ect2 bound preferentially to Rac1, while cytoplasmic Ect2 bound to RhoA but not Rac. Consistent with nuclear activation of endogenous Rac, Ect2 overexpression was sufficient to recruit Rac effectors to the nucleus, a process that required a functional Ect2 catalytic domain. Furthermore, expression of active nuclearly targeted Rac1 rescued the defect in transformed growth caused by Ect2 knockdown. Our work suggests a novel mechanism of Ect2-driven transformation, identifies subcellular localization as a regulator of GEF specificity, and implicates activation of nuclear Rac1 in cellular transformation.

Mutationally activated Rho GTPases in cancer

The Rho family of GTPases (members of the Ras superfamily) are best known for their roles in regulating cytoskeletal dynamics. It is also well established that misregulation of Rho proteins contributes to tumorigenesis and metastasis. Unlike Ras proteins, which are frequently mutated in cancer (around 30%), Rho proteins themselves are generally not found to be mutated in cancer. Rather, misregulation of Rho activity in cancer was thought to occur by overexpression of these proteins or by misregulation of molecules that control Rho activity, such as activation or overexpression of GEFs and inactivation or loss of GAPs or GDIs. Recent studies, enabled by next-generation tumor exome sequencing, report activating point mutations in Rho GTPases as driver mutations in melanoma, as well as breast, and head and neck cancers. The Rac1(P29L) mutation identified in these tumor studies was previously identified by our lab as an activating Rac mutation in C. elegans neuronal development, highlighting the conserved nature of this mutation. Furthermore, this finding supports the relevance of studying Rho GTPases in model organisms such as C. elegans to study the mechanisms that underlie carcinogenesis. This review will describe the recent findings that report activating Rho mutations in various cancer types, moving Rho GTPases from molecules misregulated in cancer to mutagenic targets that drive tumorigenesis.

Targeting Cdc42 in cancer

INTRODUCTION

The Rho GTPases are a family of proteins that control fundamental cellular processes in response to extracellular stimuli and internal programs. Rho GTPases function as molecular switches in which the GTP-bound proteins are active and GDP-bound proteins are inactive. This article will focus on one Rho family member, Cdc42, which is overexpressed in a number of human cancers, and which might provide new therapeutic targets in malignancies.

AREAS COVERED

In this article, the key regulators and effectors of Cdc42 and their molecular alterations are described. The complex interactions between the signaling cascades regulated by Cdc42 are also analyzed.

EXPERT OPINION

While mutations in Cdc42 have not been reported in human cancer, aberrant expression of Cdc42 has been reported in a variety of tumor types and in some instances has been correlated with poor prognosis. Recently, it has been shown that Cdc42 activation by oncogenic Ras is crucial for Ras-mediated tumorigenesis, suggesting that targeting Cdc42 or its effectors might be useful in tumors harboring activating Ras mutations.

Reduced expression of Rho GDP dissociation inhibitor 2 mRNA is associated with lymph node metastasis in gastric carcinoma

Small GTPase proteins, including RhoA, RhoB, RhoC, Rac1 and cdc42, are molecules that have significant roles in linking cell shape and cell cycle progression in cytoskeletal arrangements and mitogenic signaling. Rho GDP dissociation inhibitor 2 (RhoGDI2) has recently been identified as a metastasis suppressor gene in models of bladder cancer. RhoGDI2 has also been identified as a potential regulator of tumorigenesis and cancer progression. The present study aimed to clarify the significance of RhoGDI2 gene expression in gastric carcinoma and to evaluate the outcome of affected patients. A total of 46 pairs of normal mucosa and cancer specimens were obtained from patients who had undergone a gastrectomy for primary gastric carcinoma and were subjected to semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) for RhoGDI2. The expression of RhoGDI2 mRNA was significantly higher in early-stage gastric cancer specimens compared with the normal gastric epithelium samples. By contrast, the depth of the tumor was negatively correlated with RhoGDI2 mRNA expression. In addition, a reduced expression of RhoGDI2 mRNA was associated with venous system invasion and lymph node metastasis. RhoGDI2 mRNA was more frequently expressed in differentiated adenocarcinoma compared with poorly-differentiated adenocarcinoma. Although the statistical significance was not established, RhoGDI2-positive patients tended to have a superior oncological outcome compared with RhoGDI2-negative patients. The reduced expression of RhoGDI2 mRNA in gastric carcinoma is associated with venous system invasion and lymph node metastasis.

The faces and friends of RhoGDI2

RhoGDI2 is a guanine nucleotide dissociation inhibitor (GDI) specific for the Rho family of small GTPases that plays dual opposite roles in tumor progression, being both a promoter in tissues such as breast and a metastasis suppressor in tissues such as the bladder. Despite a clear role for this protein in modulating the invasive and metastatic process, the mechanisms through which RhoGDI2 executes these functions remain unclear. This review will highlight the current state of our knowledge regarding how RhoGDI2 functions in metastasis with a focus on bladder cancer and will also seek to highlight other potential underappreciated avenues through which this protein may affect cancer cell behavior.

The Golgi in cell migration: regulation by signal transduction and its implications for cancer cell metastasis

Migration and invasion are fundamental features of metastatic cancer cells. The Golgi apparatus, an organelle involved in posttranslational modification and sorting of proteins, is widely accepted to regulate directional cell migration. In addition, mounting evidence suggests that the Golgi is a hub for different signaling pathways. In this paper we will give an overview on how polarized secretion and microtubule nucleation at the Golgi regulate directional cell migration. We will review different signaling pathways that signal to and from the Golgi. Finally, we will discuss how these signaling pathways regulate the role of the Golgi in cell migration and invasion. We propose that by identifying regulators of the Golgi, we might be able to uncover unappreciated modulators of cell migration. Uncovering the regulatory network that orchestrates cell migration is of fundamental importance for the development of new therapeutic strategies against cancer cell metastasis.

Off the beaten paths: alternative and crosstalk regulation of Rho GTPases

Rho proteins are small GTPases of the Ras superfamily that regulate a wide variety of biological processes, ranging from gene expression to cell migration. Mechanistically, the major Rho GTPases function as molecular switches cycling between an inactive GDP-bound and an active GTP-bound conformation, although several Rho proteins spontaneously exchange nucleotides or are simply devoid of GTPase activity. For over a decade, RhoGEFs and RhoGAPs have been established as the mainstream regulators of Rho proteins, respectively flipping the switch on or off. However, regulation by GEFs and GAPs leaves several fundamental questions on the operation of the Rho switch unanswered, indicating that the regulation of Rho proteins does not rely exclusively on RhoGEFs and RhoGAPs. Recent evidence indeed suggests that Rho GTPases are finely tuned by multiple alternative regulatory mechanisms, including post-translational modifications and protein degradation, as well as crosstalk mechanisms between Rho proteins. Here we review these alternative mechanisms and discuss how they alter Rho protein function and signaling. We also envision how the classic binary Rho switch may indeed function more like a switchboard with multiple switches and dials that can all contribute to the regulation of Rho protein function.