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Chronic myeloid leukemia (CML) is an aggressive malignancy originating from hematopoietic stem cells. Imatinib (IM), the first-generation tyrosine kinase inhibitor, has greatly improved theliving quality of CML patients. However, owing to the recurrence and treatment failure coming from tyrosine kinase inhibitor (TKIs) resistance, some CML patients still bear poor prognosis. Therefore, we aimed to seek potential signaling pathways and specific biomarkers for imatinib resistance. We performed mRNA and miRNA expression profiling in imatinib-sensitive K562 cells (IS-K562) and imatinib-resistant K562 cells (IR-K562). Differentially expressed genes (DEGs) were identified and pathway enrichment analyses were performed to explore the potential mechanism. The protein–protein interaction (PPI) network and miRNA-mRNA regulatory network were constructed to explore potential relationships among these genes. RT-qPCR, western blot and CCK8 were used for further experiments. A total of 623 DEGs and 61 differentially expressed miRNAs were identified. GO revealed that DEGs were mainly involved in cell adhesion, cell migration, differentiation, and inflammatory response. KEGG revealed that DEGs were typically enriched in the Rap1 signaling pathway, focal adhesion, proteoglycans and transcriptional misregulation in cancer, signaling pathways regulating pluripotency of stem cells and some immune-related pathways. The protein–protein interaction (PPI) network and miRNA-mRNA regulatory network revealed a web of diverse connections among genes. Finally, we proved that RHoGDI2 played a critical role in imatinib resistance. The dynamic interplay between genes and signaling pathways is associated with TKIs resistance and RHoGDI2 is identified as a biomarker in IR-K562. [ABSTRACT FROM AUTHOR]

Leukemia is a type of disease in which hematopoietic stem cells proliferate clonally at the genetic level. We discovered previously by high‐resolution mass spectrometry that diallyl disulfide (DADS), which is one of the effective ingredients of garlic, reduces the performance of RhoGDI2 from APL HL‐60 cells. Although RhoGDI2 is oversubscribed in several cancer categories, the effect of RhoGDI2 in HL‐60 cells has remained unexplained. We aimed to investigate the influence of RhoGDI2 on DADS‐induced differentiation of HL‐60 cells to elucidate the association among the effect of inhibition or over‐expression of RhoGDI2 with HL‐60 cell polarization, migration and invasion, which is important for establishing a novel generation of inducers to elicit leukemia cell polarization. Co‐transfection with RhoGDI2‐targeted miRNAs apparently decreases the malignant biological behavior of cells and upregulates cytopenias in DADS‐treated HL‐60 cell lines, which increases CD11b and decreases CD33 and mRNA levels of Rac1, PAK1 and LIMK1. Meanwhile, we generated HL‐60 cell lines with high‐expressing RhoGDI2. The proliferation, migration and invasion capacity of such cells were significantly increased by the treated with DADS, while the reduction capacity of the cells was decreased. There was a reduction in CD11b and an increase in CD33 production, as well as an increase in the mRNA levels of Rac1, PAK1 and LIMK1. It also confirmed that inhibition of RhoGDI2 attenuates the EMT cascade via the Rac1/Pak1/LIMK1 pathway, thereby inhibiting the malignant biological behavior of HL‐60 cells. Thus, we considered that inhibition of RhoGDI2 expression might be a new therapeutic direction for the treatment of human promyelocytic leukemia. The anti‐cancer property of DADS against HL‐60 leukemia cells might be regulated by RhoGDI2 through the Rac1‐Pak1‐LIMK1 pathway, which provides new evidence for DADS as a clinical anti‐cancer medicine. [ABSTRACT FROM AUTHOR]

Background: Rho GDP dissociation inhibitor 2 (RhoGDI2) has been shown to contribute to the aggressive phenotypes of human cancers, such as tumor metastasis and chemoresistance. Objective: This study aimed to assess the effects of RhoGDI2 on tumor progression and chemoresistance in pancreatic cancer cells. Methods: The expression of RhoGDI2 in pancreatic cancer cells was detected by Western blot analysis. Gain-of-function and loss-of-function approaches were done to examine the malignant phenotypes of the RhoGDI2-expressing or RhoGDI2-depleting cells. The correlation between RhoGDI2 and Snail was also analyzed. Results: Differential expression of RhoGDI2 protein in pancreatic cancer cell lines was identified. Gain-of-function and loss-of-function experiments showed that RhoGDI2 induced the malignant phenotypes of pancreatic cancer cells, including proliferation, migration, invasion, and gemcitabine (GEM) chemoresistance. The upregulation of RhoGDI2 stimulated the expression of Snail, resulting in the altered expression of epithelial marker E-cadherin and mesenchymal marker Vimentin, which were characteristics of the tumorigenic activity of epithelial–mesenchymal transition. The expression of RhoGDI2 and Snail was upregulated in clinical tumor samples, and higher expression of RhoGDI2 or Snail was significantly associated with poor patient survival in pancreatic ductal adenocarcinoma (PDAC). Conclusion: The findings indicated that RhoGDI2 promoted GEM resistance and tumor progression in pancreatic cancer and that RhoGDI2 might be a potential therapeutic target in patients with PDAC. [ABSTRACT FROM AUTHOR]

Bing Xia, Jing Wang Hunan Cancer Hospital and the Affiliated Tumor Hospital of Xiang-Ya School of Medicine, Central South University, Changsha 410078, People’s Republic of ChinaCorrespondence: Jing WangHunan Cancer Hospital and the Affiliated Tumor Hospital of Xiang-Ya School of Medicine, Central South University, 283 Tongzipo Road, Yuelu District, Changsha 410078, People’s Republic of ChinaTel +86 135 4865 1043Email wangjing_hnzyyy@163.comObjective: 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.Keywords: adenosine, ovarian cancer, RhoGDI2, invasion, growth, angiogenesis

Gastric cancer (GC) is the fifth most common primary malignancy in humans. Rho GDP dissociation inhibitor 2 (RhoGDI2) is overexpressed in multiple cancer types, but the role of RhoGDI2 in GC has not been elucidated. This study aims to determine the level of RhoGDI2 in GC and to confirm the effect of its inhibition or overexpression on GC cell migration, invasion and chemosensitivity. RhoGDI2 level is significantly enhanced in human GC tissue samples in comparison with normal gastric epithelium and corresponding para-cancerous samples. The expression of RhoGDI2 is correlated with clinicopathological parameters and prognosis. Transfection in combination with miRNA targeting of RhoGDI2 in GC cell lines remarkably downregulates GC cell migration and invasion and reduces the mRNA levels of Rac1, Pak1 and LIMK1. The inhibition of RhoGDI2 downregulates GC cell migration and invasion by attenuating the EMT cascade via the Rac1/Pak1/LIMK1 pathway. Knockdown of RhoGDI2 is a potential therapeutic strategy for GC. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to evaluate the function of RhoGDI2 in lung cancer epithelial-mesenchymal transition (EMT) process and to illustrate the underlying mechanisms that will lead to improvement of lung cancer treatment. Methods: The RhoGDI2 knock-down and overexpressing A549 cell lines were first constructed. The influence of RhoGDI2 on cytoskeleton in A549 cells was studied using two approaches: G-LISA-based Rac1 activity measurement and immunostaining-based F-actin distribution. The expression levels of key EMT genes were analyzed using real time quantitative polymerase chain reaction (RT-qPCR), western blot and immunostaining in untreated and RhoGDI2 knock-down or overexpressing A549 cells in both in vivo and in vitro experimental settings. Results: Our study showed that the activity of Rac1, a key gene that is crucial for the initiation and metastasis of human lung adenocarcinoma, causing the redistribution of F-actin with partial loss of cell-cell adhesions and stress fibers, was significantly suppressed by RhoGDI2. RhoGDI2 promoted the expression of EMT marker gene E-cadherin and repressed EMT promoting genes Slug, Snail, α-SMA in both A549 cells and lung and liver organs derived from the mouse models. Knocking-down RhoGDI2 induced abnormal morphology for lung organs. Conclusion: These findings indicate that RhoGDI2 repressed the activity of Rac1 and may be involved in the rearrangement of cytoskeleton in lung cancer cells. RhoGDI2 suppresses the metastasis of lung cancer mediated through EMT by regulating the expression of key genes such as E-cadherin, Slug, Snail and α-SMA in both in vivo and in vitro models.

Rho GDP dissociation inhibitors (RhoGDIs) play important roles in various cellular processes, including cell migration, adhesion, and proliferation, by regulating the functions of the Rho GTPase family. Dissociation of Rho GTPases from RhoGDIs is necessary for their spatiotemporal activation and is dynamically regulated by several mechanisms, such as phosphorylation, sumoylation, and protein interaction. The expression of RhoGDIs has changed in many human cancers and become associated with the malignant phenotype, including migration, invasion, metastasis, and resistance to anticancer agents. Here, we review how RhoGDIs control the function of Rho GTPases by regulating their spatiotemporal activity and describe the regulatory mechanisms of the dissociation of Rho GTPases from RhoGDIs. We also discuss the role of RhoGDIs in cancer progression and their potential uses for therapeutic intervention.

Rho GDP dissociation inhibitors (GDIs) are pivotal regulators of Rho GTPases, which are essential for tumor progression, yet their role in hepatocellular carcinoma (HCC) remains poorly understood. The purpose of the present study was to assess the role of RhoGDIs in the invasiveness and migration of liver cancer, and to determine their clinical prognostic significances in HCC following liver transplantation (LT). In the present study, the expression of RhoGDIs was assessed using reverse transcription-quantitative polymerase chain reaction and confirmed by western-blot analysis and immunohistochemistry. Their prognostic values were also analyzed, and determined in patients treated with LT. In addition, the functions of RhoGDIs in liver cancer cell line were studied in vitro. As a result, the downregulation of RhoGDI1 and RhoGDI2 at mRNA and protein levels were detected in HCC when compared with that of adjacent noncancerous tissues (P<0.05). However, the level of RhoGDI3 was identified to be similar in tumor and para-carcinoma tissues. Additionally, Kaplan-Meier curves demonstrated that patients with lower expression of RhoGDI1 or RhoGDI2 exhibited significantly increased risk of tumor recurrence following LT (P=0.007 and P=0.006, respectively). Cox proportional hazards model analysis revealed that the decreased expression level of RhoGDI2 was an unfavorable independent prognostic factor (hazard ratio, 3.306; P=0.001). In vitro studies involving the silencing of RhoGDI1 or RhoGDI2 demonstrated a significant increase in the migratory and invasive ability of tumor cells upon the silencing of these genes. Results from the present study indicate that RhoGDI dysregulation is a frequent event in human HCC, and that it promotes cancer progression by stimulating cell migration and invasion. RhoGDI2 may be a prognostic biomarker for patients with HCC following LT, and act as a potential therapeutic target. [ABSTRACT FROM AUTHOR]

Background: The importance of the mTOR complex 2 (mTORC2) signaling complex in tumor progression is becoming increasingly recognized. HER2-amplified breast cancers use Rictor/mTORC2 signaling to drive tumor formation, tumor cell survival and resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy. Cell motility, a key step in the metastatic process, can be activated by mTORC2 in luminal and triple negative breast cancer cell lines, but its role in promoting metastases from HER2-amplified breast cancers is not yet clear.Methods: Because Rictor is an obligate cofactor of mTORC2, we genetically engineered Rictor ablation or overexpression in mouse and human HER2-amplified breast cancer models for modulation of mTORC2 activity. Signaling through mTORC2-dependent pathways was also manipulated using pharmacological inhibitors of mTOR, Akt, and Rac. Signaling was assessed by western analysis and biochemical pull-down assays specific for Rac-GTP and for active Rac guanine nucleotide exchange factors (GEFs). Metastases were assessed from spontaneous tumors and from intravenously delivered tumor cells. Motility and invasion of cells was assessed using Matrigel-coated transwell assays.Results: We found that Rictor ablation potently impaired, while Rictor overexpression increased, metastasis in spontaneous and intravenously seeded models of HER2-overexpressing breast cancers. Additionally, migration and invasion of HER2-amplified human breast cancer cells was diminished in the absence of Rictor, or upon pharmacological mTOR kinase inhibition. Active Rac1 was required for Rictor-dependent invasion and motility, which rescued invasion/motility in Rictor depleted cells. Rictor/mTORC2-dependent dampening of the endogenous Rac1 inhibitor RhoGDI2, a factor that correlated directly with increased overall survival in HER2-amplified breast cancer patients, promoted Rac1 activity and tumor cell invasion/migration. The mTORC2 substrate Akt did not affect RhoGDI2 dampening, but partially increased Rac1 activity through the Rac-GEF Tiam1, thus partially rescuing cell invasion/motility. The mTORC2 effector protein kinase C (PKC)α did rescue Rictor-mediated RhoGDI2 downregulation, partially rescuing Rac-guanosine triphosphate (GTP) and migration/motility.Conclusion: These findings suggest that mTORC2 uses two coordinated pathways to activate cell invasion/motility, both of which converge on Rac1. Akt signaling activates Rac1 through the Rac-GEF Tiam1, while PKC signaling dampens expression of the endogenous Rac1 inhibitor, RhoGDI2. [ABSTRACT FROM AUTHOR]

On activation at sites of vascular injury, platelets undergo morphological alterations essential to hemostasis via cytoskeletal reorganizations driven by the Rho GTPases Rac1, Cdc42, and RhoA. Here we investigate roles for Rho-specific guanine nucleotide dissociation inhibitor proteins (RhoGDIs) in platelet function. We find that platelets express two RhoGDI family members, RhoGDI and Ly-GDI. Whereas RhoGDI localizes throughout platelets in a granule-like manner, Ly-GDI shows an asymmetric, polarized localization that largely overlaps with Rac1 and Cdc42 as well as microtubules and protein kinase C (PKC) in platelets adherent to fibrinogen. Antibody interference and platelet spreading experiments suggest a specific role for Ly-GDI in platelet function. Intracellular signaling studies based on interactome and pathways analyses also support a regulatory role for Ly-GDI, which is phosphorylated at PKC substrate motifs in a PKC-dependent manner in response to the platelet collagen receptor glycoprotein (GP) VI–specific agonist collagen-related peptide. Additionally, PKC inhibition diffuses the polarized organization of Ly-GDI in spread platelets relative to its colocalization with Rac1 and Cdc42. Together, our results suggest a role for Ly-GDI in the localized regulation of Rho GTPases in platelets and hypothesize a link between the PKC and Rho GTPase signaling systems in platelet function. [ABSTRACT FROM AUTHOR]

Objective: To investigate the expressions and clime pathological significances of RHOGDI2 and CIAPIN1 in the liver cancer. Methods: 112 cases of patients with liver cancer admitted in our hospital from May 2013 to September 2015 were chosen for the research, and the expressions of RhoGDI2 and CTAPINl in the samples of liver cancer and the surrounding normal tissues were detected by immunohistochemistry and the unpact of both genes on the proliferation and invasion of liver cancer were analyzed. The relative genes related to the proliferation and invasion from GEO datasets were researched; the genes that expressed the same trend or the opposite trend with RhoGDI2 or CIAPIN1 with GE02R, online DAVID tools were used for mapping differentially expressed genes to signaling pathway, and finding the possible mechanisms that RhoGDI2 and CIAPIN1 worked on the proliferation and invasion of liver cancer. Results: The positive expression rates of RlioGDI2 and CIAPIN1 in liver cancer were 66.96 %, 27.68 % respectively. And the expression of both genes had a close contact with the process of liver cancer, and RhoGDI2 had a positive correlation with the lymphatic metastasis and distant metastasis of liver cancer and there was no relationship with age, gender, primary tumors in installment, primary focal diameter, histologic classification, TNM Installment. However, the expression of CIAPIN1 had no relationship with age, gender, primary tumors in installment, primary focal diameter, lymphatic metastasis and distant metastasis. But its expression had relationship with histologic classification and TNM installment. The expression of RhoGDI2 had positive relationship with metastasis of liver cancer, the expression of CIAPIN1 had positive relationship with histologic classification and negative relationship with TNM installment. And RlioGDI2 appeared to influence the PI3K-Akt-mTOR and Rho-ROCK pathway to play parts in regulating the proliferation and invasion of liver cancer with the help of DAVID tools, while CIAPIN1 may impact the process through ERK1/2-MAPK signaling pathway. Conclusions: Both RhoGDIZ and CIAPIN1 were highly expression in the liver cancer, and the high expression of RhoGDIZ might promote the invasion of liver cancer, and the expression of CIAPIN1 had no relationship with the invasion situation, but had a positive relationship with the severity of liver cancer, the two genes might play a role in the invasion and differentiation of liver cancer via different signaling pathway. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The hemerythrin-like domain of F-box and leucine-rich repeat protein 5 (FBXL5), an E3 ubiquitin ligase subunit, has critical roles in the regulation of cancer cells metastasis and chemoresistance by targeting diverse substrates for ubiquitin-mediated destruction. M ATERIALS AND METHODS: Here, we report that FBXL5 interacts with Rho GDP dissociation inhibitor 2 (RhoGDI2) and attenuates RhoGDI2-induced cisplatin resistance in gastric cancer cells. By utilizing immunoprecipitation (IP) coupled with mass spectrometry assay, we found that FBXL5 regulated gastric cancers migration via cortactin destruction. RESULTS: Depletion of FBXL5 enhances cisplatin resistance of gastric cancer cells through Erk and p38 activation. However, FBXL5 did not affect the abundance and stability of RhoGDI2. Instead, FBXL5 was rapidly degraded in response to cisplatin treatment in RhoGDI2-overexpressing gastric cancer cells. CONCLUSIONS: Collectively, our data suggested the existence of a FBXL5-RhoGDI2 negative feedback loop in RhoGDI2-induced cisplatin resistance in gastric cancer cells, implicating FBXL5 as a novel and promising therapeutic target for RhoGDI2-induced cisplatin resistance gastric cancers. [ABSTRACT FROM AUTHOR]

Filamin A (FLNA) is an actin filament crosslinking protein with multiple intracellular binding partners. Mechanical force exposes cryptic FLNA binding sites for some of these ligands. To identify new force-dependent binding interactions, we used a fusion construct composed of two FLNA domains, one of which was previously identified as containing a force-dependent binding site as a bait in a yeast two-hybrid system and identified the Rho dissociation inhibitor 2 (RhoGDI2) as a potential interacting partner. A RhoGDI2 truncate with 81 N-terminal amino acid residues and a phosphomimetic mutant, RhoGDI(Tyr153Glu) interacted with the FLNA construct. However, neither wild-type or full-length RhoGDI2 phosphorylated at Y153 interacted with FLNA. Our interpretation of these contradictions is that truncation and/or mutation of RhoGDI2 perturbs its conformation to expose a site that adventitiously binds FLNA and is not a bona–fide interaction. Therefore, previous studies reporting that a RhoGDI(Y153E) mutant suppresses the metastasis of human bladder cancer cells must be reinvestigated in light of artificial interaction of this point mutant with FLNA. [ABSTRACT FROM AUTHOR]

Multidrug resistance (MDR) is a major clinical obstacle in treatment of gastric cancer. Previously, using 2D electrophoresis-mass spectrometry, we identified RhoGDI2 as a contributor to 5-FU resistance in colon cancer cells, and also confer gastric cancer cells resistance to 5-FU. Here, we reported RhoGDI2 also induced MDR in gastric cancer cell line (MKN-45). To explore the underlining mechanism, we detected the mRNA, protein expression, activity of P-glycoprotein (P-gp) in MKN-45 stably transfected with RhoGDI2 expressing or control vector. All the mRNA, protein level, activity were increased by 130%, 230%, 35% respectively after ectopic expression of RhoGDI2. RhoGDI2 was correlated with P-gp expression in gastric cancer tissues as detected by immunohistochemistry. To further study how RhoGDI2 up-regulates P-gp expression, we tested the activity of Rac1 in MKN-45/RhoGDI2 and MKN-45/GFP. Ectopic expression of RhoGDI2 increased Rac1 activity (P < 0.05). For more important, silencing of Rac1 expression by siRNA decreased P-gp expression to undetectable level. Overall, these findings suggest that RhoGDI2 up-regulates P-gp expression via Rac1 to induce MDR. [ABSTRACT FROM AUTHOR]

The Rho GDP-dissociation inhibitor (RhoGDI) originally downregulates Rho family GTPases by preventing nucleotide exchange and membrane association. Although RhoGDI2 functions as a metastasis regulator, little is known in glial cells under neuropathological conditions. We monitored RhoGDI2 expression in the mouse brain after administering a kainic acid(KA)-induced excitotoxic lesion. In control, RhoGDI2 immunoreactivity (IR) was evident in the neuronal layer of the hippocampus. However, RhoGDI2 IR was increased in astrocytes markedly throughout the hippocampus at day 3 post-treatment with KA. To further investigate the molecular mechanism of RhoGDI2-induced cellular migration, primary astrocytes were transfected with the flag-tagged RhoGDI2 cDNA. Cell migration assay revealed that RhoGDI2 cDNA transfection inhibits astrocyte migration. Overexpression of RhoGDI2 leads to inhibit protein kinase B (PKB) activation and cdc42 and cAMP-responsive element-binding protein (CREB) phosphorylation. In conclusion, our results suggested for the first time that RhoGDI2 is required for PKB and CREB activation and cdc42 expression in astrocyte migration after KA-mediated excitotoxic lesion in mouse brain. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rho GDP dissociation inhibitor 2 (RhoGDI2) was identified as a functional metastasis suppressor in human bladder cancer, suggesting that increasing the RhoGDI2 level may represent a promising therapeutic strategy. It has been shown that the transactivator of transcription (TAT) protein from HIV-1 is able to efficiently deliver various biological molecules into several cell types. In this study, TAT peptide was fused with the N-terminus of RhoGDI2, and the resulting TAT-RhoGDI2 fragment was inserted into the pGEX-6p-1 plasmid and expressed as a glutathione S-transferase (GST)/TAT-RhoGDI2 fusion protein in Escherichia coli BL21(DE3) cells. A two-step purification strategy involving glutathione sepharose chromatography and PreScission protease cleavage was developed to purify TAT-RhoGDI2; subsequently, the identification of the involved macromolecules was achieved by Western blot. The final product, TAT-RhoGDI2, was obtained at a concentration of 112 mg/L. This is the first report on the efficient production of bioactive TAT-RhoGDI2 through a gene-engineering approach in E. coli. Using flow cytometry, we found that the TAT-RhoGDI2 fusion proteins could penetrate into bladder cancer cells with an extremely high efficiency. In vitro scratch and transwell assay and the migration/invasion behavior of UMUC3 cells were strongly reduced by the treatment with TAT-RhoGDI2. These studies support the use of the TAT-RhoGDI2 protein in tumor metastasis therapy. [ABSTRACT FROM AUTHOR]

Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches []. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive []. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass []. Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [, ] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [, , ] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements. In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases []. Many physicians and patients opt for additional chemotherapy in order to 'mop up' cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable. Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [-], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [-]. The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases []. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers. Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth []. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease. In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves []. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to evaluate the function of RhoGDI2 in lung cancer epithelial-mesenchymal transition (EMT) process and to illustrate the underlying mechanisms that will lead to improvement of lung cancer treatment. Methods: The RhoGDI2 knock-down and overexpressing A549 cell lines were first constructed. The influence of RhoGDI2 on cytoskeleton in A549 cells was studied using two approaches: G-LISA-based Rac1 activity measurement and immunostaining-based F-actin distribution. The expression levels of key EMT genes were analyzed using real time quantitative polymerase chain reaction (RT-qPCR), western blot and immunostaining in untreated and RhoGDI2 knock-down or overexpressing A549 cells in both in vivo and in vitro experimental settings. Results: Our study showed that the activity of Rac1, a key gene that is crucial for the initiation and metastasis of human lung adenocarcinoma, causing the redistribution of F-actin with partial loss of cell-cell adhesions and stress fibers, was significantly suppressed by RhoGDI2. RhoGDI2 promoted the expression of EMT marker gene E-cadherin and repressed EMT promoting genes Slug, Snail, α-SMA in both A549 cells and lung and liver organs derived from the mouse models. Knocking-down RhoGDI2 induced abnormal morphology for lung organs. Conclusion: These findings indicate that RhoGDI2 repressed the activity of Rac1 and may be involved in the rearrangement of cytoskeleton in lung cancer cells. RhoGDI2 suppresses the metastasis of lung cancer mediated through EMT by regulating the expression of key genes such as E-cadherin, Slug, Snail and α-SMA in both in vivo and in vitro models. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

RhoGDP dissociation inhibitor 2 (RhoGDI2) has been identified as a regulator of tumor metastasis; however, its role in cancer remains controversial. The aims of this study were to analyze RhoGDI2 in gastric cancer growth and metastasis, and to determine its possible signaling pathway. The level of expression of RhoGDI2 was further confirmed by real time RT-RCR and Western blot analysis. Transfection of cells with RhoGDI2 shRNA resulted in no effects of cell proliferation, as determined with MTT assays. In an in vitro invasion assay, significantly fewer cells transfected with RhoGDI2 shRNA, compared with control cells, were able to invade across a Matrigel membrane barrier. The role of RhoGDI2 in the level of HGF-induced up-regulation of vascular endothelial growth factor (VEGF) was measured by knockdown of RhoGDI2 with RhoGDI2 shRNA and a chromatic immuno-precipitation assay. The levels of RhoGDI2 and VEGF were up-regulated in cells treated with HGF in a dose-dependent manner. HGF-induced up-regulation of VEGF was repressed by RhoGDI2 knockdown. HGF-induced upregulation of phosphorylated ERK and P38 levels was inhibited in RhoGDI2 knockdown cells. HGF enhanced the binding activity of RhoGDI2 to the VEGF promoter in control cells, but not in RhoGDI2-shRNA cells. Findings of this study also showed a statistically significant difference in the mean RhoGDI2 level before and after surgery ( p < 0.01) and the mean level of RhoGDI2 before surgery showed a statistically significant difference depending on lymphatic, neural invasion and stage ( p < 0.05). In conclusion, RhoGDI2 might play an important role in up-regulation of VEGF induced by HGF and contributes to HGF-mediated tumor invasion and metastasis, which may serve as a promising target for gastric cancer therapy. [ABSTRACT FROM AUTHOR]

Rho GDP dissociation inhibitor 2 (RhoGDI2) expression is correlated with tumor growth, metastasis and chemoresistance in gastric cancer. However, the mechanisms by which RhoGDI2 promotes tumor cell survival and metastasis remain unclear. In this study, we clearly demonstrate that RhoGDI2 upregulates VEGF-C expression and RhoGDI2 expression is positively correlated with VEGF-C expression in human gastric tumor tissues as well as parental gastric cancer cell lines. VEGF-C depletion suppressed RhoGDI2-induced gastric cancer metastasis and sensitized RhoGDI2-overexpressing cells to cisplatin-induced apoptosis in vitro and in vivo. Secreted VEGF-C enhanced gastric cancer cell invasion and conferred cisplatin resistance to RhoGDI2-overexpressing cells. We also show that RhoGDI2 positively regulates Rac1 activity in gastric cancer cells. Inhibition of Rac1 expression suppressed RhoGDI2-induced VEGF-C expression, and this inhibition was associated with decreased invasiveness and increased sensitivity to cisplatin in RhoGDI2-overexpressing cells. Our results indicate that RhoGDI2 might be a potential therapeutic target for simultaneously reducing metastasis risk and enhancing chemotherapy efficacy in gastric cancer. [ABSTRACT FROM AUTHOR]

Rictor's role in cell migration has been first indicated in the original chemotaxis studies in Dictyostelium and more recent studies reported that rictor is required for migration of cancer cells. How rictor promotes cell migration remains poorly characterized. Based on our proteomics study we have identified a novel functional role of rictor in regulation of cell migration. Here, we discuss our recent finding that rictor by suppressing RhoGDI2 maintains activity of the Rac1/cdc42 GTPases and promotes cell migration. Our finding outlines a critical role of rictor in the regulation of RhoGDI2 activity. This study opens new avenues in the investigation of cancer metastasis by analyzing the rictor dependent post-translational modification of RhoGDI2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Rho GDP dissociation inhibitor (RhoGDI)2 has been identified as a regulator of Rho family GTPase. Recently, we suggested that RhoGDI2 could promote tumor growth and malignant progression in gastric cancer. In this study, we demonstrate that RhoGDI2 contributes to another important feature of aggressive cancers, i.e., resistance to chemotherapeutic agents such as cisplatin. Forced expression of RhoGDI2 attenuated cisplatin-induced apoptosis, whereas RhoGDI2 depletion showed opposite effects in vitro. Moreover, the increased anti-apoptotic effect of RhoGDI2 on cisplatin was further validated in RhoGDI2-overexpressing SNU-484 xenograft model in nude mice. Furthermore, we identified Bcl-2 as a major determinant of RhoGDI2-mediated cisplatin resistance in gastric cancer cells. Depletion of Bcl-2 expression significantly increased cisplatin-induced apoptosis in RhoGDI2-overexpressing gastric cancer cells, whereas overexpression of Bcl-2 blocked cisplatin-induced apoptosis in RhoGDI2-depleted gastric cancer cells. Overall, these findings establish RhoGDI2 as an important therapeutic target for simultaneously enhancing chemotherapy efficacy and reducing metastasis risk in gastric cancer. [Copyright &y& Elsevier]

Abstract: Rho GDP dissociation inhibitor 2 (RhoGDI2) is a regulator of the Rho family GTPases. Recent work from our laboratory suggests that RhoGDI2 expression potentially enhances resistance to cisplatin as well as promotes tumor growth and malignant progression in gastric cancer. In this study, we demonstrate that phospholipase C-gamma (PLCγ) is required for RhoGDI2-mediated cisplatin resistance and cancer cell invasion in gastric cancer. The levels of phosphorylated PLCγ are markedly enhanced in RhoGDI2-overexpressing SNU-484 cells and, by contrast, repressed in RhoGDI2-depleted MKN-28 cells. Depletion of PLCγ expression or inhibition of its activity not only significantly increases cisplatin-induced apoptosis but also suppresses the invasive ability of RhoGDI2-overexpressing SNU-484 cells. Taken together, our results suggest that PLCγ plays a key role in RhoGDI2-mediated cisplatin resistance and cell invasion in gastric cancer cells. [Copyright &y& Elsevier]

Abstract: The most lethal and debilitating attribute of cancer cells is their ability to metastasize. Throughout the process of metastasis, tumor cells interact with other tumor cells, host cells and a variety of molecules. Tumor cells are also faced with a number of insults, such as hemodynamic sheer pressure and immune selection. This brief review explores how metastasis suppressor proteins regulate interactions between tumor cells and the microenvironments in which tumor cells find themselves. [Copyright &y& Elsevier]

Rho GDP-Dissociation Inhibitors (RhoGDIs) are important regulators of the Rho family of small GTPases. The expression of RhoGDIs is altered in a variety of cancers and they have been shown to mediate several processes during tumorigenesis and cancer progression. Using examples of RhoGDI-mediated signaling and expression patterns in endothelial cells as well as pancreatic, breast, and bladder cancer, the multitude of potential cancer therapeutic targets presented by a better understanding of their function is illustrated. Several novel therapeutic strategies are proposed for intervening in RhoGDI signaling, and potential complications arising from their implementation are discussed. [Copyright &y& Elsevier]

Despite the recent advances in the diagnosis of bladder cancer, recurrence after surgical intervention for muscle invasive disease is still problematic as nearly half of the patients harbor occult distant metastases and this, in turn, is associated with poor 5-year survival rate. We have recently identified Rho family GDP dissociation inhibitor 2 (RhoGDI2) protein as functional metastasis suppressor and a prognostic marker in patients after cystectomy. In identifying the mechanisms underlying metastasis suppression by RhoGDI2, we found this protein to be associated with the c-Src kinase in human tumors, where the expression of both is diminished as a function of stage. Interestingly, c-Src bound to and phosphorylated RhoGDI2 resulting in enhanced metastasis suppressive potency. In this review, we will discuss the established roles of c-Src and RhoGDI2 in bladder cancer and speculate on their therapeutic relevance. [ABSTRACT FROM AUTHOR]

Abstract: The major problem for cancer patients is metastasis of the cancer from the primary tumor to secondary sites. Metastasis is the process by which tumor cells disseminate from the primary tumor, migrate through the basement membrane, survive in the circulatory system, invade into a secondary site, and start to proliferate. In the past, research had concentrated on the biology, taking more of a global view instead of a molecular view. More recently, the focus has been determining the molecular underpinnings, looking at genes that induce or inhibit metastasis. Metastasis suppressors, by definition, inhibit metastasis at any step of the metastatic cascade without blocking primary tumor growth. The expanding list of metastasis suppressors exist with every cellular compartment and have been shown to work by regulating signaling pathways that inhibit proliferation, cell migration and growth at the secondary site. Still, the biochemical basis of their inhibition is not completely known. Here we review the known metastasis suppressors and summarize the suspected mechanisms by which they inhibit metastasis. [Copyright &y& Elsevier]

RhoGDI2, a cytosolic regulator of Rho GTPase, is cleaved during apoptosis in a caspase-3 dependent fashion. By using 2D-gel electrophoresis, mass spectrometry and Western blotting we investigate in this paper the functional consequences of RhoGDI2 processing. We can show that loss of the N-terminal 19 amino acids results in a shift of the isoelectric point of the truncated RhoGDI2 (NΔ19) to a more basic value due to the removal of 9 acidic amino acids from the N-terminus, which may be responsible for enhanced retention of the N-terminally truncated protein within the nuclear compartment. Fusion of the p53 nuclear export signaling sequence MFRELNEALELK to NΔ19 (NΔ19NES) abolished its apoptosis promoting properties, while overexpression of NΔ19 significantly increased the susceptibility to apoptosis induction by the proteasome inhibitor PSI and by staurosporine. These results suggest that cleavage of RhoGDI2 by caspase-3 is not a functionally irrelevant bystander effect of caspase activation during apoptosis, but rather expedites progression of the apoptotic process. [ABSTRACT FROM AUTHOR]

Cancer metastasis is a significant contributor to breast cancer patient morbidity and mortality. In order to develop new anti-metastatic therapies, we need to understand the biological and biochemical mechanisms of metastasis. Toward these efforts, we and others have studied metastasis suppressor genes, which halt metastasis in vivo without affecting primary tumor growth. The first metastasis suppressor gene identified was nm23, also known as NDP kinase. Nm23 represents the most widely validated metastasis suppressor gene, based on transfection and knock-out mouse strategies. The biochemical mechanism of metastasis suppression via Nm23 is unknown and likely complex. Two potential mechanisms include binding proteins and a histidine kinase activity. Elevation of Nm23 expression in micrometastatic tumor cells may constitute a translational strategy for the limitation of metastatic colonization in high risk cancer patients. To date, medroxyprogesterone acetate (MPA) has been identified as a candidate compound for clinical testing. [ABSTRACT FROM AUTHOR]

Simple Summary: Rho GDP dissociation inhibitor 2 (RhoGDI2), a regulator of Rho family GTPase, has been known to promote tumor growth and malignant progression by activating Rac1 in gastric cancer. However, the precise molecular mechanism by which RhoGDI2 activates Rac1 in gastric cancer cells remains unclear. In this study, we found that interaction between RhoGDI2 and Rac1 is a prerequisite for the recruitment of Rac1 to Filamin A. Moreover, we found that Filamin A acts as a scaffold protein that mediates Rac1 activation. Furthermore, we found that Trio, a Rac1-specific GEF, is critical for Rac1 activation in gastric cancer cells. Conclusively, RhoGDI2 increases Rac1 activity by recruiting Rac1 to Filamin A and enhancing the interaction between Rac1 and Trio, which is critical for invasive ability of gastric cancer cells. Our findings suggest that RhoGDI2 might be a potential therapeutic target for reducing gastric cancer cell metastasis. Rho GDP dissociation inhibitor 2 (RhoGDI2), a regulator of Rho family GTPase, has been known to promote tumor growth and malignant progression in gastric cancer. We previously showed that RhoGDI2 positively regulates Rac1 activity and Rac1 activation is critical for RhoGDI2-induced gastric cancer cell invasion. In this study, to identify the precise molecular mechanism by which RhoGDI2 activates Rac1 activity, we performed two-hybrid screenings using yeast and found that RhoGDI2 plays an important role in the interaction between Rac1, Filamin A and Rac1 activation in gastric cancer cells. Moreover, we found that Filamin A is required for Rac1 activation and the invasive ability of gastric cancer cells. Depletion of Filamin A expression markedly reduced Rac1 activity in RhoGDI2-expressing gastric cancer cells. The migration and invasion ability of RhoGDI2-expressing gastric cancer cells also substantially decreased when Filamin A expression was depleted. Furthermore, we found that Trio, a Rac1-specific guanine nucleotide exchange factor (GEF), is critical for Rac1 activation and the invasive ability of gastric cancer cells. Therefore, we conclude that RhoGDI2 increases Rac1 activity by recruiting Rac1 to Filamin A and enhancing the interaction between Rac1 and Trio, which is critical for the invasive ability of gastric cancer cells. [ABSTRACT FROM AUTHOR]

Rho GDP dissociation inhibitors (RhoGDIs) play important roles in various cellular processes, including cell migration, adhesion, and proliferation, by regulating the functions of the Rho GTPase family. Dissociation of Rho GTPases from RhoGDIs is necessary for their spatiotemporal activation and is dynamically regulated by several mechanisms, such as phosphorylation, sumoylation, and protein interaction. The expression of RhoGDIs has changed in many human cancers and become associated with the malignant phenotype, including migration, invasion, metastasis, and resistance to anticancer agents. Here, we review how RhoGDIs control the function of Rho GTPases by regulating their spatiotemporal activity and describe the regulatory mechanisms of the dissociation of Rho GTPases from RhoGDIs. We also discuss the role of RhoGDIs in cancer progression and their potential uses for therapeutic intervention. [ABSTRACT FROM AUTHOR]

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., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

Background: The importance of the mTOR complex 2 (mTORC2) signaling complex in tumor progression is becoming increasingly recognized. HER2-amplified breast cancers use Rictor/mTORC2 signaling to drive tumor formation, tumor cell survival and resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy. Cell motility, a key step in the metastatic process, can be activated by mTORC2 in luminal and triple negative breast cancer cell lines, but its role in promoting metastases from HER2-amplified breast cancers is not yet clear., Methods: Because Rictor is an obligate cofactor of mTORC2, we genetically engineered Rictor ablation or overexpression in mouse and human HER2-amplified breast cancer models for modulation of mTORC2 activity. Signaling through mTORC2-dependent pathways was also manipulated using pharmacological inhibitors of mTOR, Akt, and Rac. Signaling was assessed by western analysis and biochemical pull-down assays specific for Rac-GTP and for active Rac guanine nucleotide exchange factors (GEFs). Metastases were assessed from spontaneous tumors and from intravenously delivered tumor cells. Motility and invasion of cells was assessed using Matrigel-coated transwell assays., Results: We found that Rictor ablation potently impaired, while Rictor overexpression increased, metastasis in spontaneous and intravenously seeded models of HER2-overexpressing breast cancers. Additionally, migration and invasion of HER2-amplified human breast cancer cells was diminished in the absence of Rictor, or upon pharmacological mTOR kinase inhibition. Active Rac1 was required for Rictor-dependent invasion and motility, which rescued invasion/motility in Rictor depleted cells. Rictor/mTORC2-dependent dampening of the endogenous Rac1 inhibitor RhoGDI2, a factor that correlated directly with increased overall survival in HER2-amplified breast cancer patients, promoted Rac1 activity and tumor cell invasion/migration. The mTORC2 substrate Akt did not affect RhoGDI2 dampening, but partially increased Rac1 activity through the Rac-GEF Tiam1, thus partially rescuing cell invasion/motility. The mTORC2 effector protein kinase C (PKC)α did rescue Rictor-mediated RhoGDI2 downregulation, partially rescuing Rac-guanosine triphosphate (GTP) and migration/motility., Conclusion: These findings suggest that mTORC2 uses two coordinated pathways to activate cell invasion/motility, both of which converge on Rac1. Akt signaling activates Rac1 through the Rac-GEF Tiam1, while PKC signaling dampens expression of the endogenous Rac1 inhibitor, RhoGDI2.

Rho GDP dissociation inhibitor 2 (RhoGDI2) expression is correlated with tumor growth, metastasis and chemoresistance in gastric cancer. However, the mechanisms by which RhoGDI2 promotes tumor cell survival and metastasis remain unclear. In this study, we clearly demonstrate that RhoGDI2 upregulates VEGF-C expression and RhoGDI2 expression is positively correlated with VEGF-C expression in human gastric tumor tissues as well as parental gastric cancer cell lines. VEGF-C depletion suppressed RhoGDI2-induced gastric cancer metastasis and sensitized RhoGDI2-overexpressing cells to cisplatin-induced apoptosis in vitro and in vivo. Secreted VEGF-C enhanced gastric cancer cell invasion and conferred cisplatin resistance to RhoGDI2-overexpressing cells. We also show that RhoGDI2 positively regulates Rac1 activity in gastric cancer cells. Inhibition of Rac1 expression suppressed RhoGDI2-induced VEGF-C expression, and this inhibition was associated with decreased invasiveness and increased sensitivity to cisplatin in RhoGDI2-overexpressing cells. Our results indicate that RhoGDI2 might be a potential therapeutic target for simultaneously reducing metastasis risk and enhancing chemotherapy efficacy in gastric cancer., (© 2014 UICC.)

The invasion of placental trophoblast cells into the maternal decidua is an essential aspect of placental embedment. The process of placentation bears several striking similarities to tumor cell metastasis. However, trophoblastic migration during implantation and placentation is stringently controlled both in space and time. RhoGDI2 belongs to a family of Rho guanosine diphosphate dissociation inhibitors (RhoGDIs), and RhoGDI2 is a metastasis suppressor gene and a marker of aggressive human cancer. We evaluated whether RhoGDI2 has a physiological role in embryo implantation, particularly trophoblast migration. The mRNA and protein expression levels of RhoGDI2 were higher in term placentas compared with first-trimester placentas as detected by real-time PCR and Western blot. Immunohistochemical studies indicated that RhoGDI2 localized to the cytotrophoblast layer and extravillous trophoblast in first-trimester placentas and was distributed in the syncytiotrophoblast layers of term placentas. Overexpression of RhoGDI2 in HTR-8/SVneo cells was associated with reduced RAC1-guanosine triphosphate (GTP) levels and inhibited cell migration. Conversely, small interfering RNA-mediated downregulation of RhoGDI2 resulted in significantly increased RAC1-GTP levels. Altered RhoGDI2 expression had no significant effects on cell proliferation. In conclusion, RhoGDI2 inhibits trophoblast cell migration, and this function may involve suppression of RAC1 activation.