RhoGTPases and Rho-effectors in hepatocellular carcinoma metastasis: ROCK N'Rho move it

A Novel hepatocellular carcinoma specific hypoxic related signature for predicting prognosis and therapeutic responses

Hypoxia is an important feature of the tumor microenvironment(TME) and is closely associated with cancer metastasis, immune evasion, and drug resistance. However, the precise role of hypoxia in hepatocellular carcinoma(HCC), as well as its influence on the TME, and drug sensitivity remains unclear. We found the excellent survival prediction value of Hypoxia_DEGs_Score model. In hypoxic HCC, somatic mutation, copy number variation, and DNA methylation were closely related to hypoxic changes and affected tumorigenesis, progression, metastasis, and drug resistance. In HCC, aggravated hypoxic stress was found to be accompanied by an immune exclusion phenotype and increased infiltration of immunosuppressive cells. In the validation cohort, patients with high Hypoxia_DEGs_Score were found to have worse immunotherapeutic outcomes and prognoses, and may benefit from drugs against cell cycle signaling pathways rather than those inhibiting the PI3K/mTOR pathway. Hypoxia_DEGs_Score has an excellent predictive capability of changes in the TME, the efficacy of immunotherapy, and the response of drugs. Therefore, Hypoxia_DEGs_Score can help develop personalized immunotherapy regimens and improve the prognosis of HCC patients.

Immunotherapy checkpoints in ovarian cancer vasculogenic mimicry: Tumor immune microenvironments, and drugs

Vasculogenic mimicry (VM), a vessel-like structure independent of endothelial cells, commonly exists in solid tumors which requires blood vessels to grow. As a special source of blood supply for tumor progression to a more aggressive state, VM has been observed in a variety of human malignant tumors and is tightly associated with tumor proliferation, invasion, metastasis, and poor patient prognosis. So far, various factors, including immune cells and cytokines, were reported to regulate ovarian cancer progression by influencing VM formation. Herein, we review the mechanisms that regulate VM formation in ovarian cancer and the effect of cells, cytokines, and signaling molecules in the tumor microenvironment on VM formation, Furthermore, we summarize the current clinical application of drugs targeting VM formation.

Construction and Comprehensive Analysis of a circRNA-miRNA-mRNA Regulatory Network to Reveal the Pathogenesis of Hepatocellular Carcinoma

Background: Circular RNAs (circRNAs) have been demonstrated to be closely related to the carcinogenesis of human cancer in recent years. However, the molecular mechanism of circRNAs in the pathogenesis of hepatocellular carcinoma (HCC) has not been fully elucidated. We aimed to identify critical circRNAs and explore their potential regulatory network in HCC.

Methods: The robust rank aggregation (RRA) algorithm and weighted gene co-expression network analysis (WGCNA) were conducted to unearth the differentially expressed circRNAs (DEcircRNAs) in HCC. The expression levels of DEcircRNAs were validated by quantitative real-time polymerase chain reaction (qRT-PCR). A circRNA-miRNA-mRNA regulatory network was constructed by computational biology, and protein-protein interaction (PPI) network, functional enrichment analysis, survival analysis, and infiltrating immune cells analysis were performed to uncover the potential regulatory mechanisms of the network.

Results: A total of 22 DEcircRNAs were screened out from four microarray datasets (GSE94508, GSE97332, GSE155949, and GSE164803) utilizing the RRA algorithm. Meanwhile, an HCC-related module containing 404 circRNAs was identified by WGCNA analysis. After intersection, only four circRNAs were recognized in both algorithms. Following qRT-PCR validation, three circRNAs (hsa_circRNA_091581, hsa_circRNA_066568, and hsa_circRNA_105031) were chosen for further analysis. As a result, a circRNA-miRNA-mRNA network containing three circRNAs, 17 miRNAs, and 222 mRNAs was established. Seven core genes (ESR1, BUB1, PRC1, LOX, CCT5, YWHAZ, and DDX39B) were determined from the PPI network of 222 mRNAs, and a circRNA-miRNA-hubgene network was also constructed. Functional enrichment analysis suggested that these seven hub genes were closely correlated with several cancer related pathways. Survival analysis revealed that the expression levels of the seven core genes were significantly associated with the prognosis of HCC patients. In addition, we also found that these seven hub genes were remarkably related to the infiltrating levels of immune cells.

Conclusion: Our research identified three pivotal HCC-related circRNAs and provided novel insights into the underlying mechanisms of the circRNA-miRNA-mRNA regulatory network in HCC.

RhoA and Rac1 in Liver Cancer Cells: Induction of Overexpression Using Mechanical Stimulation

Liver cancer, especially hepatocellular carcinoma (HCC), is an aggressive disease with an extremely high mortality rate. Unfortunately, no promising markers are currently available for the early diagnosis of this disease. Thus, a reliable biomarker reflecting the early behaviour of the tumour will be valuable for diagnosis and treatment. The Ras homologous (Rho) GTPases, which belong to the small guanosine triphosphate (GTP) binding proteins, have been reported to play an important role in mediating liver cancer based on their important function in cytoskeletal reorganisation. These proteins can be either oncogenic or tumour suppressors. They are also associated with the acquirement of malignant features by cancer cells. The overexpression of RhoA and Rac1, members of the Rho GTPases, have been linked with carcinogenesis and the progression of different types of cancer. In the quest of elucidating the role of mechanical stimulation in the mechanobiology of liver cancer cells, this paper evaluates the effect of stretching on the expression levels of RhoA and Rac1 in different types of liver cancers. It is shown that that stretching liver cancer cells significantly increases the expression levels of RhoA and Rac1 in HCC and cholangiocarcinoma cell lines. We hypothesise that this relatively simple and sensitive method could be helpful for screening biological features and provide suitable treatment guidance for liver cancer patients.

Olive oil polyphenols suppress the TGF-α-induced migration of hepatocellular carcinoma cells

Oleuropein and 3-hydroxytyrosol (3-HT) are natural polyphenols present in olive oil that are known to exhibit potent anti-oxidant activities and exert protective effects against a number of human diseases. In the liver, olive oil polyphenols have been demonstrated to prevent hepatocellular carcinoma (HCC) cell growth. However, little is known about their effects against HCC cell migration. Therefore, the present study investigated whether or not oleuropein and 3-HT were involved in the suppression of transforming growth factor-α (TGF-α)-induced migration of human HCC cells using human HCC-derived HuH7 cells. The TGF-α-induced migration of HuH7 cells was significantly and dose-dependently suppressed by oleuropein and 3-HT. This study group demonstrated previously that the TGF-α-induced activation of AKT and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) were involved in HuH7 cell migration. In addition to these protein kinases, the present study examined the involvement of TGF-α-induced activation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK) and Rho kinase in HuH7 cell migration. TGF-α-induced HuH7 cell migration was decreased by SB203580, a p38 MAPK inhibitor, and Y27632, a Rho kinase inhibitor. However, PD98059, an inhibitor of the upstream kinase activating ERK, did not suppress the TGF-α-induced migration of HuH7 cells. Although AKT, SAPK/JNK, p38 MAPK and Rho kinase pathways were suggested to be involved in the TGF-α-induced migration of HuH7 cells, 10-30 µM 3-HT did not exhibit any suppressive effect on the TGF-α-stimulated activities of these kinases. The results of the present study suggest that olive oil polyphenols suppressed the TGF-α-induced migration of HCC cells.

FARP1 Facilitates Cell Proliferation Through Modulating MAPK Signaling Pathway in Cutaneous Melanoma

PURPOSE

The purpose of our study was to investigate the biological functions of FARP1 gene in cutaneous melanoma.

METHODS

The mRNA expression level of FARP1 in cutaneous melanoma was analyzed based on the data obtained from ONCOMINE and The Cancer Genome Atlas database. Kaplan-Meier analysis was conducted to explore the association between FARP1 expression and the overall survival time of patients with cutaneous melanoma. The mRNA expression of FARP1 in melanoma cells was determined by qRT-PCR. A-375 cell line with silenced FARP1 was constructed to explore its biological functions. Cell proliferation, migration, and invasion abilities were determined by CCK8 assay, wound-healing assay, and transwell assays, respectively. Western blot was performed to explore the protein expression of FARP1, pMEK, MEK, pERK, and ERK.

RESULTS

Our results showed that the expression level of FARP1 was upregulated in cutaneous melanoma tissues and cells. Kaplan-Meier analysis revealed that high expression of FARP1 is predictive of shorter overall survival time in patients with cutaneous melanoma. Through CCK8 assay, we found that knockdown of FARP1 in A-375 cells exhibited dramatically inhibitory effect on cell proliferation. The results of wound-healing and transwell assays revealed that the motility of A-375 cells was notably suppressed after silencing FARP1. Moreover, the relative expression levels of pMEK/MEK and pERK/ERK decreased remarkably in A-375 cells following being transfected with si-FARP1.

CONCLUSIONS

Our present results preliminary proofed that FARP1 possibly acts as a promoter in cutaneous melanoma development and possesses the potential to be a therapeutic target in patients with cutaneous melanoma.

RhoC/ROCK2 promotes vasculogenic mimicry formation primarily through ERK/MMPs in hepatocellular carcinoma

Vasculogenic mimicry (VM) results in the formation of an alternative circulatory system that can improve the blood supply to multiple malignant tumors, including hepatocellular carcinoma (HCC). However, the potential mechanisms of RhoC/ROCK in VM have not yet been investigated in HCC. Here, RhoC expression was upregulated in HCC tissues, especially the VM-positive (VM+) group, compared to noncancerous tissues (P < 0.01), and patients with high expression of RhoC had shorter survival times (P < 0.001). The knockdown of RhoC via short hairpin RNA (shRNA) in SK-Hep-1 cells significantly decreased VM formation and cell motility. In contrast, cell motility and VM formation were remarkably enhanced when RhoC was overexpressed in HepG2 cells. To further assess the potential role of ROCK1 and ROCK2 on VM, we stably knocked down ROCK1 or ROCK2 in MHCC97H cells. Compared to ROCK1 shRNA, ROCK2 shRNA could largely affect VM formation, cell motility and the key VM factors, as well as the epithelial-mesenchymal transition (EMT) markers in vitro and in vivo. Moreover, p-ERK, p-MEK, p-FAK, p-paxillin, MT1-MMP and MMP2 levels were clearly altered following the overexpression of RhoC, but ROCK2 shRNA had little effect on the expression of p-FAK, which indicated that RhoC regulates FAK/paxillin signaling, but not through ROCK2. In conclusion, our results show that RhoC/ROCK2 may have a major effect on VM in HCC via ERK/MMPs signaling and might be a potential therapeutic target for the treatment of HCC.

Sphingosine 1-phosphate (S1P) reduces hepatocyte growth factor-induced migration of hepatocellular carcinoma cells via S1P receptor 2

A bioactive lipid, sphingosine 1-phosphate (S1P), acts extracellularly as a potent mediator, and is implicated in the progression of various cancers including hepatocellular carcinoma (HCC). S1P exerts its functions by binding to five types of specific receptors, S1P receptor 1 (S1PR1), S1PR2, S1PR3, S1PR4 and S1PR5 on the plasma membrane. However, the exact roles of S1P and each S1PR in HCC cells remain to be clarified. In the present study, we investigated the effect of S1P on the hepatocyte growth factor (HGF)-induced migration of human HCC-derived HuH7 cells, and the involvement of each S1PR. S1P dose-dependently reduced the HGF-induced migration of HuH7 cells. We found that all S1PRs exist in the HuH7 cells. Among each selective agonist for five S1PRs, CYM5520, a selective S1PR2 agonist, significantly suppressed the HGF-induced HuH7 cell migration whereas selective agonists for S1PR1, S1PR3, S1PR4 or S1PR5 failed to affect the migration. The reduction of the HGF-induced migration by S1P was markedly reversed by treatment of JTE013, a selective antagonist for S1PR2, and S1PR2- siRNA. These results strongly suggest that S1P reduces the HGF-induced HCC cell migration via S1PR2. Our findings may provide a novel potential of S1PR2 to therapeutic strategy for metastasis of HCC.

Ginsenoside Rg3 inhibits the migration and invasion of liver cancer cells by increasing the protein expression of ARHGAP9

Ginsenoside Rg3, a naturally occurring phytochemical, serves an important role in the prevention and treatment of cancer. In the present study, with the aim to reveal the molecular mechanism of Rg3 in liver cancer cell metastasis, the anti-migration and anti-invasion effects of Rg3 on liver cancer cells were investigated. It was demonstrated that Rg3 caused marked inhibition of cell migration and invasion of human liver cancer cells, HepG2 and MHCC-97L, in vitro, and the growth of HepG2 and MHCC-97L tumors in BABL/c nude mice. The protein expression of Rho GTPase activating protein 9 (ARHGAP9) was increased both in HepG2 and MHCC-97L cells. Following ARHGAP9 knockdown, the results of Transwell and tumorigenesis assays revealed that the anti-migration, anti-invasion and anti-tumor growth effects of Rg3 were impaired significantly. The increased expression of ARHGAP9 protein induced by Rg3 was remarkably suppressed. All results suggested that ARHGAP9 protein may be a vital regulator in the anti-metastatic role of Rg3. To the best of our knowledge, the present study is the first to report that Rg3 effectively suppressed the migration and invasion of liver cancer cells by upregulating the protein expression of ARHGAP9, indicating a novel natural therapeutic agent and a therapeutic target for the treatment of liver cancer.

Identification of protein kinase inhibitors to reprogram breast cancer cells

Direct reversion of cancers into normal-like tissues is an ideal strategy for cancer treatment. Recent reports have showed that defined transcription factors can induce reprogramming of cancer cells into pluripotent stem cells, supporting this notion. Here, we have developed a reprogramming method that uses a conceptually unique strategy for breast cancer cell treatment. We have screened a kinase inhibitor library and found that Rho-associated protein kinase (ROCK) and mammalian target of rapamycin (mTOR) kinase inhibitors can substitute for all transcription factors to be sufficient to reprogram breast cancer cells into progenitor cells. Furthermore, ROCK–mTOR inhibitors could reprogram breast cancer cells to another terminal lineage-adipogenic cells. Genome-wide transcriptional analysis shows that the induced fat-like cells have a profile different from breast cancer cells and similar to that of normal adipocytes. In vitro and in vivo tumorigenesis assays have shown that induced fat-like cells lose proliferation and tumorigenicity. Moreover, reprogramming treatment with ROCK–mTOR inhibitors prevents breast cancer local recurrence in mice. Currently, ROCK–mTOR inhibitors are already used as antitumor drugs in patients, thus, this reprogramming strategy has significant potential to move rapidly toward clinical trials for breast cancer treatment.

Reprogramming glioblastoma multiforme cells into neurons by protein kinase inhibitors

Background

Reprogramming of cancers into normal-like tissues is an innovative strategy for cancer treatment. Recent reports demonstrate that defined factors can reprogram cancer cells into pluripotent stem cells. Glioblastoma multiforme (GBM) is the most common and aggressive malignant brain tumor in humans. Despite multimodal therapy, the outcome for patients with GBM is still poor. Therefore, developing novel therapeutic strategy is a critical requirement.

Methods

We have developed a novel reprogramming method that uses a conceptually unique strategy for GBM treatment. We screened a kinase inhibitor library to find which candidate inhibitors under reprogramming condition can reprogram GBM cells into neurons. The induced neurons are identified whether functional and loss of tumorigenicity.

Results

We have found that mTOR and ROCK kinase inhibitors are sufficient to reprogram GBM cells into neural-like cells and “normal” neurons. The induced neurons expressed neuron-specific proteins, generated action potentials and neurotransmitter receptor-mediated currents. Genome-wide transcriptional analysis showed that the induced neurons had a profile different from GBM cells and were similar to that of control neurons induced by established methods. In vitro and in vivo tumorigenesis assays showed that induced neurons lost their proliferation ability and tumorigenicity. Moreover, reprogramming treatment with ROCK-mTOR inhibitors prevented GBM local recurrence in mice.

Conclusion

This study indicates that ROCK and mTOR inhibitors-based reprogramming treatment prevents GBM local recurrence. Currently ROCK-mTOR inhibitors are used as anti-tumor drugs in patients, so this reprogramming strategy has significant potential to move rapidly toward clinical trials.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0857-5) contains supplementary material, which is available to authorized users.

The noncoding RNA HOXD-AS1 is a critical regulator of the metastasis and apoptosis phenotype in human hepatocellular carcinoma

BACKGROUND

Despite accumulating evidence that long noncoding RNAs (lncRNAs) are associated with cancer development in multiple types of cancer, the biological roles of many lncRNAs in human hepatocellular carcinoma (HCC) metastasis have not been well characterized.

METHODS

A lncRNA+ mRNA human gene expression microarray analysis was used to identify differentially expressed lncRNAs in metastatic HCC tissues compared to non-metastatic tissue.

RESULTS

We observed remarkable overexpression of HOXD-AS1 in metastatic cancer tissues. In vitro and in vivo gain- or loss-of-function studies re-affirmed that HOXD-AS1 is able to facilitate cancer metastasis and inhibit apoptosis. Moreover, we identified that HOXD-AS1 upregulated the Rho GTPase activating protein 11A (ARHGAP11A) by competitively binding to microRNA-19a (miR19a), resulting in induced metastasis. Interestingly, the regulator of G-protein signaling 3 (RGS3), a potential inhibitor of the MEK-ERK1/2 signaling axis, was also found to be downregulated by ectopic HOXD-AS1 overexpression, leading to a remarkably reduced apoptotic effect.

CONCLUSIONS

The present investigation strongly indicates that HOXD-AS1 is an oncogenic lncRNA that promotes HCC metastasis and that its pro-metastatic phenotype can partially be attributed to the HOXD-AS1/miR19a/ARHGAP11A signaling axis.

Activating Transcription Factor 4 (ATF4) modulates Rho GTPase levels and function via regulation of RhoGDIα

In earlier studies, we showed that ATF4 down-regulation affects post-synaptic development and dendritic spine morphology in neurons through increased turnover of the Rho GTPase Cell Division Cycle 42 (Cdc42) protein. Here, we find that ATF4 down-regulation in both hippocampal and cortical neuron cultures reduces protein and message levels of RhoGDIα, a stabilizer of the Rho GTPases including Cdc42. This effect is rescued by an shATF4-resistant active form of ATF4, but not by a mutant that lacks transcriptional activity. This is, at least in part, due to the fact that Arhgdia, the gene encoding RhoGDIα, is a direct transcriptional target of ATF4 as is shown in ChIP assays. This pathway is not restricted to neurons. This is seen in an impairment of cell migration on ATF4 reduction in non-neuronal cells. In conclusion, we have identified a new cellular pathway in which ATF4 regulates the expression of RhoGDIα that in turn affects Rho GTPase protein levels, and thereby, controls cellular functions as diverse as memory and cell motility.

Knockdown of Rhotekin 2 expression suppresses proliferation and invasion and induces apoptosis in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC), which is one of the most common types of cancer worldwide, has been ranked as the third leading cause of cancer‑associated mortality worldwide. Rhotekin 2 (RTKN2), a Rho‑guanosine triphosphatase (GTPase) effector, has been reported to be anti‑apoptotic. However, the molecular mechanism underlying the biological function of RTKN2 in HCC is poorly defined. The current study reported that RTKN2 was overexpressed in 83% of HCC specimens compared with adjacent noncancerous tissues (n=30). Depletion of RTKN2 in HCC cells, HepG2 and BEL‑7404 by RNA interference led to marked inhibition of cell proliferation and cell cycle progression. Notably, RTKN2 silencing significantly reduced the levels of cell cycle‑associated proteins, proliferating cell nuclear antigen and cyclin‑dependent kinase 1. Additionally, it was identified that downregulation of RTKN2 in HCC cells notably induced cell apoptosis, while significantly repressing cell invasion. These data suggest that RTKN2 may act as an oncogene and inhibition of RTKN2 may be part of a novel therapeutic strategy for targeted HCC therapy.

Syntheses and preliminary evaluation of [(18) F]AlF-NOTA-G-TMTP1 for PET imaging of high aggressive hepatocellular carcinoma

The goal of this study is to evaluate a new (18) F-labeled imaging agent for diagnosing high metastatic (aggressive) hepatocellular carcinoma using positron emission tomography (PET). The new (18) F-labeled imaging agent [(18) F]AlF-NOTA-G-TMTP1 was synthesized and radiolabeled with (18) F using NOTA-AlF chelation method. The tumor-targeting characteristics of [(18) F]AlF-NOTA-G-TMTP1 was assessed in HepG2, SMCC-7721, HCC97L and HCCLM3 xenografts. The total synthesis time was about 20 min with radiochemical yield of 25 ± 6%. The specific activity was about 11.1-14.8 GBq/µmol at the end of synthesis based on the amount of peptide used and the amount of radioactivity trapped on the C18 column. The log P value of [(18) F]AlF-NOTA-G-TMTP1 was -3.166 ± 0.022. [(18) F]AlF-NOTA-G-TMTP1 accumulated in SMCC-7721 and HCCLM3 tumors (high metastatic potential) in vivo and result in tumor/muscle (T/M) ratios of 4.5 ± 0.3 and 4.7 ± 0.2 (n = 4) as measured by PET at 40 min post-injection (p.i.). Meanwhile, the tumor/muscle (T/M) ratios of HepG2 and HCC97L tumors (low metastatic potential) were1.6 ± 0.3 and 1.8 ± 0.4. The tumor uptake of [(18) F]AlF-NOTA-G-TMTP1 could be inhibited 61.9% and 57.6% by unlabeled G-TMTP1 in SMCC-7721 and HCCLM3 xenografts at 40 min p.i., respectively. Furthermore, [(18) F]AlF-NOTA-G-TMTP1 showed pretty low activity in the liver and intestines in all tumor bearing mice, such in vivo distribution pattern would be advantageous for the detection of hepatic carcinoma. Overall, [(18) F]AlF-NOTA-G-TMTP1 may specifically target high metastatic or/and aggressive hepatocellular carcinoma with low background activity and, therefore, holds the potential to be used as an imaging agent for detecting tumor lesions within the liver area. Copyright © 2016 John Wiley & Sons, Ltd.

Downregulation of microRNA-100 enhances the ICMT-Rac1 signaling and promotes metastasis of hepatocellular carcinoma cells

Metastasis is responsible for rapid recurrence of hepatocellular carcinoma (HCC) and poor survival of HCC patients. Here we showed that miR-100 downregulation in HCC tissues was significantly associated with venous invasion, advanced TNM stage, tumor nodule without complete capsule, poorer cell differentiation, and shorter recurrence-free survival. Both gain- and loss-of-function studies showed that miR-100 dramatically suppressed the ability of HCC cells to migrate and to invade through Matrigel in vitro. Analyses using mouse orthotopic xenograft model further revealed that xenografts of miR-100-stable-expressing HCC cells displayed a significant reduction in pulmonary metastasis, compared with control group. Subsequent investigations revealed that miR-100 directly inhibited the expression of isoprenylcysteine carboxyl methyltransferase (ICMT) and ras-related C3 botulinum toxin substrate 1 (Rac1) by binding to their 3′-UTRs, and in turn suppressed lamellipodia formation and matrix metallopeptidase 2 (MMP2) activation. Furthermore, knockdown of ICMT and Rac1 phenocopied the anti-metastasis effect of miR-100, whereas overexpression of the constitutively active Rac1 (Q61L) antagonized the function of miR-100. Taken together, miR-100 represses metastasis of HCC cells by abrogating the ICMT-Rac1 signaling. Downregulation of miR-100 contributes to HCC metastasis and the restoration of miR-100 is a potential strategy for cancer therapy.

Galectin 3 regulates HCC cell invasion by RhoA and MLCK activation

Hepatocellular carcinoma (HCC) carries a poor prognosis with no effective treatment available other than liver transplantation for selected patients. Vascular invasion of HCC is one of the most important negative predictor of survival. As the regulation of invasion of HCC cells is not well understood, our aim was to study the mechanisms by which galectin 3, a β-galactosidase-binding lectin mediates HCC cell migration. HCC was induced by N-diethylnitrosamine in wild-type and galectin 3(-/-) mice, and tumor formation, histology, and tumor cell invasion were assessed. The galectin 3(-/-) mice developed significantly smaller tumor burden with a less invasive phenotype than the wild-type animals. Galectin 3 was upregulated in the wild-type HCC tumor tissue, but not in the surrounding parenchyma. Galectin 3 expression in HCC was induced by NF-κB transactivation as determined by chromatin immunoprecipitation assays. In vitro studies assessed the pro-migratory effects of galectin 3. The migration of hepatoma cells was significantly decreased after transfection by the galectin 3 siRNA and also after using the Rho kinase inhibitor Y-27632. The reorganization of the actin cytoskeleton, RhoA GTPase activity and the phosphorylation of MLC2 (myosin light chain 2) were decreased in the galectin 3 siRNA-transfected cells. In addition, in vitro and in vivo evidence showed that galectin 3 deficiency reduced hepatoma cell proliferation and increased their apoptosis rate. In conclusion, galectin 3 is an important lectin that is induced in HCC cells, and promotes hepatoma cell motility and invasion by an autocrine pathway. Targeting galectin 3 therefore could be an important novel treatment strategy to halt disease progression.

Effect of DR-nm23 overexpression on biological characteristics of human colorectal carcinoma SW620 cells

AIM: To investigate the effect of DR-nm23 overexpression on biological characteristics of human colorectal carcinoma SW620 cells.

METHODS: SW620 cells were divided into three groups: non-endogenous expression (SW620) group, mock control (SW620/mock) group, and recombinant lentiviral expression vector pGC-FU-DR-nm23-GFP transfected (SW620/DR-nm23) group. Both in vitro cell experiments and in vivo xenograft tumor model assay were carried out to investigate the role of DR-nm23 in regulation of colorectal cancer cell proliferation, movement, invasion and metastasis.

RESULTS: Induced overexpression of DR-nm23 in SW620 cells via lentiviral infection resulted in significant inhibition of cell proliferation as revealed by cell growth curve (F = 15.657, P = 0.002) and clonogenic assay (F = 45.476, P = 0.003) in vitro. Meanwhile, Transwell assay showed that the numbers of cells that passed the membrane in the SW620/DR-nm23 group, SW620/mock group and SW620 group were 14.00 ± 1.85, 18.00 ± 2.01, and 17.00 ± 1.98, respectively, indicating that the migration ability was also significantly impaired in the SW620/DR-nm23 group (F = 10.746, P = 0.006). There was no significant difference in the three groups in Boyden chamber assay. Besides, the growth rate (F = 5.579, P = 0.008) and liver metastasis rate of the SW620/DR-nm23 group were significantly reduced as compared with those of the SW620 or SW620/mock group in vivo.

CONCLUSION: Overexpression of DR-nm23 may inhibit the invasive and metastatic capabilities of colorectal carcinoma SW620 cells. Thus, expression status of DR-nm23 may act as a potential prognostic factor in patients with colorectal cancer.

The role of cytoplasmic p57 in invasion of hepatocellular carcinoma

Background

Our previous research suggested that p57 downregulation could accelerate the growth and invasion of hepatocellular carcinoma in vitro and in vivo.

Aim

To evaluate the role of cytoplasmic p57 and its regulatory mechanism during hepatocellular carcinoma invasion.

Methods

We examined the subcellular localization of p57 by immunohistochemistry in 45 pairs of cancerous tissues and adjacent non-cancerous tissues. Moreover, we generated stable p57 knockdown hepatoma cell lines to investigate the mechanism of cytoplasmic p57-mediated regulation of invasion by immunoprecipitation, confocal immunofluorescence microscopy and western blot of nuclear and cytoplasmic extracts.

Results

Our results showed that cytoplasmic expression of p57 was reduced in specimens from patients with capsular invasion and metastasis (P < 0.05). Moreover, the level of p-cofilin was decreased in the group lacking cytoplasmic p57 expression (P < 0.05). Co-expression of p57 and p-cofilin was reduced in specimens from patients with tumors at later stages (III + IV), tumors showing capsular invasion and metastatic tumors. We further observed that p57 downregulation decreased the assembly of p57 and LIM domain kinase 1 and its kinase activity, subsequently reducing the level of p-cofilin in the cytoplasm.

Conclusions

Cytoplasmic p57 might be a key regulator in hepatocellular carcinoma invasion via the LIM domain kinase 1/p-cofilin pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-015-0319-x) contains supplementary material, which is available to authorized users.

microRNA-146a inhibits cancer metastasis by downregulating VEGF through dual pathways in hepatocellular carcinoma

Abstract

Growing evidence indicates that miR-146a is involved in carcinogenesis and tumor progression in several human malignancies. However, the molecular details underlying miR-146a mediated regulation of its target genes and its precise biological function in cancer, especially in hepatocellular carcinoma (HCC) remains unclear.

Methods

The expression levels of genes including miR-146a, APC, VEGF and HAb18G were examined in HCC cell lines and patient specimens were compared with control levels using quantitative reverse transcription-PCR. The functions of miR-146a and HAb18G in migration/invasion and liver metastasis formation were determined by transwell and spleen injection assays, respectively. miR-146a related genes were determined by PCR array. The potential regulatory targets of miR-146a were determined by bioinformatics and prediction tools, correlation with target protein expression, and luciferase reporter assay. DNA methylation status of miR-146a promoter were performed by PCR analysis of bisulfite-modified genomic DNA.

Results

We demonstrated that miR-146a expression was markedly downregulated in hepatoma cells and hepatoma tissues compared to immortalized normal liver epithelial cells and normal hepatic tissues. DNA methylation of miR-146a promoter correlated with its downexpression and with liver cancer metastasis. The restoration of miR-146a dramatically suppressed HCC cell invasion and metastasis by repressing VEGF expression through upregulating APC, which inhibits β-catenin accumulation in nucleus, and downregulating NF-κB p65 by targeting HAb18G. In human HCC, miR-146a expression was negative correlated with increased HAb18G, VEGF, NF-κB p65 and beneficial prognosis.

Conclusion

This study identified a novel target of miR-146a and defined miR-146a as a crucial tumor suppressor in human HCC that acts through multiple pathways and mechanisms to suppress HCC invasion or metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-14-5) contains supplementary material, which is available to authorized users.

Rho/ROCK signaling in motility and metastasis of gastric cancer

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

Baculovirus-mediated miRNA regulation to suppress hepatocellular carcinoma tumorigenicity and metastasis

MicroRNA 122 (miR-122) is a tumor suppressor for hepatocellular carcinoma (HCC) but is lowly expressed in HCC cells. MiR-151 is aberrantly overexpressed in HCC cells and promotes HCC metastasis yet its roles on HCC tumorigenicity are unknown. To combat HCC tumorigenicity/metastasis, we developed Sleeping Beauty (SB)-based hybrid baculovirus (BV) vectors that expressed (i) miR-122 precursors (pre-miR-122), (ii) miR-151 sponges, or (iii) pre-miR-122 and miR-151 sponges. Transduction of aggressive HCC cells (Mahlavu) with the pre-miR-122-expressing BV tremendously enhanced miR-122 levels for >6 weeks, suppressed the levels of downstream effectors (e.g., ADAM10 and Bcl-w), proliferation, anchorage-independent growth, motility and migration/invasion in vitro. Intratumoral injection of the pre-miR-122-expressing BV attenuated the HCC growth/metastasis. The miR-151 sponges-expressing BV diminished the miR-151 levels for 6 weeks, enhanced RhoGDIA expression, suppressed RhoGTPases, as well as motility and migration/invasion of Mahlavu cells. Intratumoral injection of the miR-151 sponge-expressing BV impeded not only HCC metastasis but also cell proliferation, MMP expression and tumor growth in vivo. The BV co-expressing pre-miR-122 and miR-151 sponges also simultaneously enhanced miR-122 expression and inhibited miR-151, and conferred antitumor/anti-metastasis effects albeit lack of synergism. These data implicate the potentials of the SB-based hybrid BV for persistently modulating miRNA and suppressing HCC tumorigenicity/metastasis.

Overexpression of CTHRC1 in hepatocellular carcinoma promotes tumor invasion and predicts poor prognosis

Collagen triple helix repeat containing-1 (CTHRC1) is a secreted glycoprotein that activates the planar cell polarity pathway of Wnt signaling. Using microarray analysis, we found that the CTHRC1 gene is overexpressed in hepatocellular carcinoma (HCC). The level of CTHRC1 mRNA was measured in 201 surgically resected HCCs using real time reverse transcription-polymerase chain reaction. Overexpression of CTHRC1 in HCC was associated with large tumor size and advanced tumor stage. Furthermore, expression of CTHRC1 as was identified as an independent prognostic factors in the multivariate analysis. Suppression of CTHRC1 expression inhibited tumor migration and invasion whereas overexpression of CTHRC1 promoted tumor invasion. Activation of RhoA, but not Rac1 or Cdc42, was found to play a crucial role in CTHRC1-induced cell migration. CTHRC1 promoted adhesion of cancer cells to extracellular matrix through induction of integrin β1 expression and activation of focal adhesion kinase. These results suggest CTHRC1 promotes tumor invasion and metastasis by enhancing the adhesion and migratory abilities of tumor cells. It is also a promising biomarker for predicting the prognosis of patients with HCC.

Loss of p57 expression and RhoA overexpression are associated with poor survival of patients with hepatocellular carcinoma

p57 and Ras homology A (RhoA) have been implicated in the growth and metastasis of several types of human cancers. This study aimed to detect their expression in hepatocellular carcinoma (HCC) tissue specimens and to determine a possible association with clinicopathological data and patient survival. A total of 80 HCC and corresponding distant normal tissue specimens were processed for immunohistochemical and qPCR analyses of p57 and RhoA expression. The data showed that expression of p57 mRNA and protein was reduced in HCC tissues when compared to that in distant non-cancer tissues (P<0.05), while expression of RhoA mRNA and protein was significantly higher in HCC tissue specimens when compared to that of the distant normal tissues. Loss of p57 expression was associated with HCC with higher α-fetoprotein (AFP) levels (>400 ng/ml; P=0.044), larger tumor size (>5 cm, P=0.004), poor tumor differentiation (P=0.020), advanced TNM stage (P=0.027), capsule invasion (P=0.018) and tumor thrombosis (P=0.008), whereas expression of RhoA protein was significantly associated with poor tumor differentiation (P=0.042), capsule invasion (P=0.022), and tumor thrombosis (P=0.002). Furthermore, there was a strong inverse relationship between p57 and RhoA expression in HCC tissues, indicating that loss of p57 expression may contribute to RhoA overexpression in HCC tissues. The median survival time of HCC patients with p57+ and p57- expression was 13.0 and 9.0 months, respectively, whereas the median survival time of HCC patients with RhoA+ and RhoA- was 9.0 and 15.0 months. Univariate analysis revealed that the levels of AFP, tumor size, TNM stage, histological grade, capsule invasion, tumor thrombosis, p57, RhoA and co-expression of p57 and RhoA were all significant prognostic indicators for overall survival of HCC patients. Multivariate analysis showed that tumor size, TNM stage, p57, RhoA and combined loss of p57 with RhoA were risk factors for poor survival of HCC patients. This study indicates that the abnormal expression of p57 and RhoA contributes to progression of HCC and poor survival of patients.

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

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

CONCLUSION

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

Lysophosphatidic acid receptor expression and function in human hepatocellular carcinoma

BACKGROUND

Lysophosphatidic acid (LPA) is a ubiquitously expressed phospholipid that regulates diverse cellular functions. Previously identified LPA receptor subtypes (LPAR1-5) are weakly expressed or absent in the liver. This study sought to determine LPAR expression, including the newly identified LPAR6, in normal human liver (NL), hepatocellular carcinoma (HCC), and non-tumor liver tissue (NTL), and LPAR expression and function in human hepatoma cells in vitro.

METHODS

We determined LPAR1-6 expression by quantitative reverse transcriptase polymerase chain reaction, Western blot, or immunohistochemistry in NL, NTL, and HCC, and HuH7, and HepG2 cells. Hepatoma cells were treated with LPA in the absence or presence of LPAR1-3 (Ki16425) or pan-LPAR (α-bromomethylene phosphonate) antagonists and proliferation and motility were measured.

RESULTS

We report HCC-associated changes in LPAR1, 3, and 6 mRNA and protein expression, with significantly increased LPAR6 in HCC versus NL and NTL. Analysis of human hepatoma cells demonstrated significantly higher LPAR1, 3, and 6 mRNA and protein expression in HuH7 versus HepG2 cells. Treatment with LPA (0.05-10 μg/mL) led to dose-dependent HuH7 growth and increased motility. In HepG2 cells, LPA led to moderate, although significant, increases in proliferation but not motility. Pretreatment with α-bromomethylene phosphonate inhibited LPA-dependent proliferation and motility to a greater degree than Ki16425.

CONCLUSIONS

Multiple LPAR forms are expressed in human HCC, including the recently described LPAR6. Inhibition of LPA-LPAR signaling inhibits HCC cell proliferation and motility, the extent of which depends on LPAR subtype expression.

Upregulated FoxM1 expression induced by hepatitis B virus X protein promotes tumor metastasis and indicates poor prognosis in hepatitis B virus-related hepatocellular carcinoma

BACKGROUND & AIMS

Forkhead box M1 (FoxM1) is a master regulator of tumor metastasis that plays an important role in the development of hepatocellular carcinoma (HCC). However, whether or not FoxM1 contributes to the progression of HBV-associated HCC (HBV-HCC) remains unknown. Therefore, we aimed at investigating the clinicopathologic significance of FoxM1 in HBV-HCC and the potential role of FoxM1 in hepatitis B virus X (HBx)-mediated invasiveness and metastasis.

METHODS

The expression of FoxM1 and its functional targets matrix metalloproteinase-7 (MMP-7), RhoC, and Rho-kinase 1 (ROCK1) in human HBV-HCC tissues was detected by immunohistochemistry. Luciferase reporter, chromatin immunoprecipitation, and electrophoretic mobility shift assays were used to measure the transcriptional regulation of FoxM1 promoter by HBx. The effect of FoxM1 on HBx-mediated invasiveness and metastasis was analyzed by transwell assays and an orthotopic metastatic model.

RESULTS

FoxM1 overexpression correlated with multiple malignant characteristics and indicated poor prognosis of HBV-HCC patients. FoxM1 expression was an independent factor affecting the recurrence and survival of patients with HBV-HCC after surgical resection. FoxM1 promoted hepatoma cell invasion and metastasis by promoting MMP-7, RhoC, and ROCK1 expression, while FoxM1 overexpression was associated with elevated expressions of these proteins in HBV-HCC tissues. HBx upregulated FoxM1 expression through the ERK/CREB pathway, and FoxM1 inhibition significantly decreased HBx-enhanced hepatoma cell invasion in vitro and lung metastasis in vivo.

CONCLUSIONS

We report a new molecular mechanism for HBV-associated hepatocarcinogenesis that involves the activation of FoxM1 expression by HBx through the ERK/CREB pathway, thereby leading to invasion and metastasis of hepatoma cells.

Rnd3/RhoE Is down-regulated in hepatocellular carcinoma and controls cellular invasion

We performed a review of public microarray data that revealed a significant down-regulation of Rnd3 expression in hepatocellular carcinoma (HCC), as compared to nontumor liver. Rnd3/RhoE is an atypical RhoGTPase family member because it is always under its active GTP-bound conformation and not sensitive to classical regulators. Rnd3 down-regulation was validated by quantitative real-time polymerase chain reaction in 120 independent tumors. Moreover, Rnd3 down-expression was confirmed using immunohistochemistry on tumor sections and western blotting on human tumor and cell-line extracts. Rnd3 expression was significantly lower in invasive tumors with satellite nodules. Overexpression and silencing of Rnd3 in Hep3B cells led to decreased and increased three-dimensional cell motility, respectively. The short interfering RNA-mediated down-regulation of Rnd3 expression induced a loss of E-cadherin at cell-cell junctions that was linked to epithelial-mesenchymal transition through the up-regulation of the zinc finger E-box binding homeobox protein, ZEB2, and the down-regulation of miR-200b and miR-200c. Rnd3 knockdown mediated tumor hepatocyte invasion in a matrix-metalloproteinase-independent, and Rac1-dependent manner.

CONCLUSION

Rnd3 down-regulation provides an invasive advantage to tumor hepatocytes, suggesting that RND3 might represent a metastasis suppressor gene in HCC.

Role of DLC1 tumor suppressor gene and MYC oncogene in pathogenesis of human hepatocellular carcinoma: potential prospects for combined targeted therapeutics (review)

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death, and its incidence is increasing worldwide in an alarming manner. The development of curative therapy for advanced and metastatic HCC is a high clinical priority. The HCC genome is complex and heterogeneous; therefore, the identification of recurrent genomic and related gene alterations is critical for developing clinical applications for diagnosis, prognosis and targeted therapy of the disease. This article focuses on recent research progress and our contribution in identifying and deciphering the role of defined genetic alterations in the pathogenesis of HCC. A significant number of genes that promote or suppress HCC cell growth have been identified at the sites of genomic reorganization. Notwithstanding the accumulation of multiple genetic alterations, highly recurrent changes on a single chromosome can alter the expression of oncogenes and tumor suppressor genes (TSGs) whose deregulation may be sufficient to drive the progression of normal hepatocytes to malignancy. A distinct and highly recurrent pattern of genomic imbalances in HCC includes the loss of DNA copy number (associated with loss of heterozygosity) of TSG-containing chromosome 8p and gain of DNA copy number or regional amplification of protooncogenes on chromosome 8q. Even though 8p is relatively small, it carries an unusually large number of TSGs, while, on the other side, several oncogenes are dispersed along 8q. Compelling evidence demonstrates that DLC1, a potent TSG on 8p, and MYC oncogene on 8q play a critical role in the pathogenesis of human HCC. Direct evidence for their role in the genesis of HCC has been obtained in a mosaic mouse model. Knockdown of DLC1 helps MYC in the induction of hepatoblast transformation in vitro, and in the development of HCC in vivo. Therapeutic interventions, which would simultaneously target signaling pathways governing both DLC1 and MYC functions in hepatocarcinogenesis, could result in progress in the treatment of liver cancer.

Transcriptional regulation of miR-224 upregulated in human HCCs by NFκB inflammatory pathways

BACKGROUND & AIMS

miR-224 is up-regulated in human HCCs as compared to both paired peri-tumoral cirrhotic tissues and cirrhotic livers without HCC. Here, we have cloned the miR-224 regulatory region and characterized its transcriptional regulation by the NFκB-dependent inflammatory pathways.

METHODS

Mature miRNA expression was evaluated by a 2 step stem-loop real-time RT-PCR. The recruitment of polymerase II and transcription factors on the pre-miR-224 promoter has been assessed by ChIPSeq and ChIP.

RESULTS

We found miR-224 levels strongly up-regulated in both peri-tumoral cirrhotic livers and HCC samples as compared to normal livers. In silico analysis of the putative miR-224 promoter revealed multiple NFκB sites. We showed that LTα and TNFα activate transcription from the miR-224 promoter and of endogenous miR-224 expression in HCC cell lines, whereas the expression of miR-224 target API5 was reduced. Exogenously expressed p65/RelA activates the miR-224 promoter and a dominant negative form of IκBα (IκBSR) represses it. ChIP analysis showed that p65/NFκB is recruited on the miR-224 promoter and that its binding sharply increases after exposure to LPS, TNFα, and LTα. Altogether these findings link the inflammatory signals to NFκB-mediated activation of miR-224 expression. An antago-miR specific for miR-224 blocked LPS and LTα stimulated HCC cells migration and invasion. Conversely, the IKK inhibitor BMS-345541 blocks pre-miR-224-induced cellular migration and invasion.

CONCLUSIONS

Our results identify p65/NFκB as a direct transcriptional regulator of miR-224 expression and link miR-224 up-regulation with the activation of the LPS, LTα, and TNFα inflammatory pathways and cell migration/invasion in HCC.

Downregulation of p57 accelerates the growth and invasion of hepatocellular carcinoma

p57 is a multifunctional protein involved in the regulation of tumor formation and development; however, the biological role of p57 in the pathogenesis of hepatocellular carcinoma (HCC) is poorly understood. To explore the role of p57 in the development of HCC, we examined p57 messenger RNA (mRNA) and protein levels in HCC tissues and adjacent non-cancerous tissues by immunohistochemistry, real-time polymerase chain reaction and western blot analysis. Moreover, we generated stable p57 knockdown HCC cell lines to investigate the impact of p57 downregulation on the growth and invasion of HCC in vitro and in vivo. Our results showed that p57 mRNA and protein levels were significantly decreased in human HCC tissues. In addition, this reduction in p57 expression was associated with increased tumor size, more advanced TNM stages, the presence of capsule invasion and extrahepatic metastasis and decreased overall survival time. In human HCC cell lines, p57 downregulation increased the expression of cyclin D1 and CDK2 and enhanced the activities of CDK4/cyclin D1 and CDK2/cyclin E complexes, resulting in increased cellular proliferation and growth of xenografts. Furthermore, p57 downregulation accelerated the invasion of HCC cells in vitro and in vivo by controlling the activity of LIMK1. In conclusion, the downregulation of p57 accelerates the growth and invasion of HCC, indicating that p57 is an important tumor suppressor in HCC. Based on these findings, p57 may be a potential target for HCC prevention and therapy.

MicroRNA-142-3p, a new regulator of RAC1, suppresses the migration and invasion of hepatocellular carcinoma cells

RAC1 regulates a diverse array of cellular events including migration and invasion. MicroRNAs (miRNAs) have a key role in the regulation of gene expression. In this study, we demonstrated that microRNA-142-3p (miR-142-3p) acted as a negative regulator of human RAC1. Overexpression of miR-142-3p decreased RAC1 mRNA and protein levels. Moreover, the overexpression of miR-142-3p suppressed, while blocking of miR-142-3p increased colony formation, migration and invasion in hepatocellular carcinoma (HCC) cell lines (QGY-7703 and SMMC-7721). RAC1 overexpression without the 3'untranslated region abolished the effect of miR-142-3p in the QGY-7703 and SMMC-7721 cells. These results demonstrated that miR-142-3p directly and negatively regulates RAC1 in HCC cells, which highlights the importance of miRNAs in tumorigenesis.

Overexpression of engulfment and cell motility 1 promotes cell invasion and migration of hepatocellular carcinoma

Engulfment and cell motility 1 (Elmo1) has been linked to the invasive phenotype of glioma cells. The use of Elmo1 inhibitors is currently being evaluated in hepato-cellular carcinoma (HCC), but the molecular mechanisms of their therapeutic effect have yet to be determined. Elmo1 expression in HCC tissue samples from 131 cases and in 5 HCC cell lines was determined by immunohistochemistry, quantitative RT-PCR and Western blotting. To functionally characterize Elmo1 in HCC, Elmo1 expression in the HCCLM3 cell line was blocked by siRNA. Cell migration was measured by wound healing and transwell migration assays in vitro. Elmo1 overexpression was significantly correlated with cell invasion and the poor prognosis of HCC. Elmo1-siRNA-treated HCCLM3 cells demonstrated a reduction in cell migration. The present study demonstrated for the first time that the suppression of Elmo1 expression inhibits cell invasion in HCC.

Guanine nucleotide exchange factors for RhoGTPases: good therapeutic targets for cancer therapy?

Rho guanosine triphosphatases (GTPases) are a family of small proteins which function as molecular switches in a variety of signaling pathways following stimulation of cell surface receptors. RhoGTPases regulate numerous cellular processes including cytoskeleton organization, gene transcription, cell proliferation, migration, growth and cell survival. Because of their central role in regulating processes that are dysregulated in cancer, it seems reasonable that defects in the RhoGTPase pathway may be involved in the development of cancer. RhoGTPase activity is regulated by a number of protein families: guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) and guanine nucleotide-dissociation inhibitors (GDIs). This review discusses the participation of RhoGTPases and their regulators, especially GEFs in human cancers. In particular, we focus on the involvement of the RhoGTPase GEF, Vav1, a hematopoietic specific signal transducer which is involved in human neuroblastoma, pancreatic ductal carcinoma and lung cancer. Finally, we summarize recent advances in the design and application of a number of molecules that specifically target individual RhoGTPases or their regulators or effectors, and discuss their potential for cancer therapy.