Proteomics-based strategy to delineate the molecular mechanisms of RhoGDI2-induced metastasis and drug resistance in gastric cancer

Circular RNA 0001789 sponges miR-140-3p and regulates PAK2 to promote the progression of gastric cancer

BACKGROUND

Gastric cancer (GC) is the third-leading cause of cancer-associated mortalities globally. The deregulation of circular RNAs (circRNAs) and microRNAs (miRNAs or miRs) is widely implicated in the pathogenesis and progression of different cancer types.

METHODS

The expression profiling of circRNAs in GC is required to identify crucial circRNAs as biomarkers or therapeutic targets. In the present study, a published circRNA microarray dataset was used to identify differentially expressed circRNAs between GC tissues and normal gastric mucosa tissues. Reverse transcription-quantitative PCR was performed to validate the expression of circ_0001789. Fisher's exact test, receiver operating characteristic curve and Kaplan-Meier plots were employed to analyze the clinical significance of circ_0001789. The miRNA targets of circ_0001789 were predicted using an online database, and their functional interaction was further confirmed by RNA pull-down, RNA immunoprecipitation and dual luciferase reporter assays. Transwell assays were conducted to investigate the biological functions of circ_0001789, miR-140-3p and p21 activated kinase 2 (PAK2) in the migration and invasion of GC cells. A xenograft mouse model was established to validate the role of circ_0001789 in the tumorigenesis of GC cells.

RESULTS

circ_0001789 was identified as a highly expressed circRNA in GC tissues versus normal gastric mucosa tissues. Silencing circ_0001789 attenuated the malignancy of GC cells, and exosomal circ_0001789 was sufficient to regulate the malignant phenotype of GC cells. miR-140-3p was further identified as a downstream target of circ_0001789, which showed a negative correlation with circ_0001789 expression in GC tissues. Overexpression of miR-140-3p suppressed cell migration, invasion and epithelial-mesenchymal transition in GC cells. PAK2 was identified as the target of miR-140-3 to mediate the malignant phenotype of GC cells.

CONCLUSION

The present data suggested that the upregulation of circ_0001789 was associated with the progression of GC and with poor prognosis in patients with GC, and that miR-140-3p/PAK2 served as the downstream axis to mediate the oncogenic effect of circ_0001789.

p21-Activated Kinase: Role in Gastrointestinal Cancer and Beyond

Simple Summary

Gastrointestinal tumors are the most common tumors with a high mortality rate worldwide. Numerous protein kinases have been studied in anticipation of finding viable tumor therapeutic targets, including PAK. PAK is a serine/threonine kinase that plays an important role in the malignant phenotype of tumors. The function of PAK in tumors is highlighted in cell proliferation, survival, motility, tumor cell plasticity and the tumor microenvironment, therefore providing a new possible target for clinical tumor therapy. Based on the current research works of PAK, we summarize and analyze the PAK features and signaling pathways in cells, especially the role of PAK in gastrointestinal tumors, thereby hoping to provide a theoretical basis for both the future studies of PAK and potential tumor therapeutic targets.

Abstract

Gastrointestinal tumors are the most common tumors, and they are leading cause of cancer deaths worldwide, but their mechanisms are still unclear, which need to be clarified to discover therapeutic targets. p21-activating kinase (PAK), a serine/threonine kinase that is downstream of Rho GTPase, plays an important role in cellular signaling networks. According to the structural characteristics and activation mechanisms of them, PAKs are divided into two groups, both of which are involved in the biological processes that are critical to cells, including proliferation, migration, survival, transformation and metabolism. The biological functions of PAKs depend on a large number of interacting proteins and the signaling pathways they participate in. The role of PAKs in tumors is manifested in their abnormality and the consequential changes in the signaling pathways. Once they are overexpressed or overactivated, PAKs lead to tumorigenesis or a malignant phenotype, especially in tumor invasion and metastasis. Recently, the involvement of PAKs in cellular plasticity, stemness and the tumor microenvironment have attracted attention. Here, we summarize the biological characteristics and key signaling pathways of PAKs, and further analyze their mechanisms in gastrointestinal tumors and others, which will reveal new therapeutic targets and a theoretical basis for the clinical treatment of gastrointestinal cancer.

RhoGDI2 induced malignant phenotypes of pancreatic cancer cells via regulating Snail expression

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.

miR-511-5p Suppresses Cell Migration, Invasion and Epithelial-Mesenchymal Transition Through Targeting PAK2 in Gastric Cancer

As a malignant tumor, gastric cancer (GC) is closely related with gastric mucosa and has a high mortality in the world. Since microRNA (miRNA) has become more and more important in tumor research, we intend to find out the functional role and mechanism of miR-511-5p in GC. Firstly, miR-511-5p level was examined in human GC cell lines and tissues, and its effect on cell migration and invasion of BGC-823 or HGC-27 cells was tested by migration assay and transwell assay. Then, we confirmed the association between miR-511-5p and p21 activated kinase 2 (PAK2) by the luciferase reporter assay, and further assessed their role in cell migration and invasion. Moreover, we verified the function of miR-511-5p and PAK2 in epithelial-mesenchymal transition (EMT). In our study, miR-511-5p was downregulated in GC cell lines and tissues, and inversely associated with PAK2. Luciferase reporter assay confirmed that miR-511-5p could bind to PAK2. MiR-511-5p mimics significantly upregulated E-cadherin and downregulated N-cadherin, Vimentin and Snail, and consequently inhibited cell migration and invasion. However, reintroduction of PAK2 reversed the inhibitory function of miR-511-5p on BGC-823 and HGC-27 cells. Our research suggested that tumor-suppressive function of miR-511-5p in GC was inhibited by PAK2, and miR-511-5p/PAK2 axis may serve as a new strategy in GC management.

Serum Levels of Cytokine-Induced Apoptosis Inhibitor 1 (CIAPIN1) as a Potential Prognostic Biomarker of Cholangiocarcinoma

The mortality rate of cholangiocarcinoma (CCA) is high since there is a lack of a non-invasive technique to accurately detect tumors at the early stage. CCA biomarkers are consistently needed for various purposes including screening, early diagnosis, prognosis and follow-up. Herein, using bioinformatic analysis of our mitochondrial proteome database of CCA tissues, we identified cytokine-induced apoptosis inhibitor 1 (CIAPIN1) as a potential prognostic biomarker for CCA. CIAPIN1 levels in the sera of 159 CCA patients and 93 healthy controls (HC) were measured using a dot blot assay. The median level ± quartile deviation of CIAPIN1 level in the sera of CCA patient group was 0.5144 ± 0.34 µg/µL, which was significantly higher than 0.2427 ± 0.09 µg/µL of the HC group (p < 0.0001). In CCA patients, higher serum CIAPIN1 level was significantly associated with lymph node metastasis (p = 0.024) and shorter overall survival time (p = 0.001, Kaplan–Meier test). Cox regression analysis showed that the serum CIAPIN1 level can be an independent prognostic indicator for the survival of CCA patients. Moreover, for the prediction of CCA prognosis, CIAPIN1 is superior to CEA, CA19-9 and ALP. In conclusion, CIAPIN1 can be a serum biomarker candidate for the poor prognosis of CCA.

Long intergenic noncoding RNA 00665 promotes proliferation and inhibits apoptosis in colorectal cancer by regulating miR-126-5p

Long intergenic noncoding RNAs (lincRNAs) regulate a series of biological processes, and their anomalous expression plays critical roles in the progression of multiple malignancies, including colorectal cancer (CRC). Although many studies have reported the oncogenic function of LINC00665 in multiple cancers, few studies have explored its role in CRC. The aim of this study was to assess the effect of LINC00665 on the malignant behaviors of CRC and explore the underlying regulatory mechanism of LINC00665. LINC00665 was significantly upregulated in CRC. A loss-of-function assay revealed that LINC00665 downregulation inhibited the proliferation and promoted the apoptosis of CRC cells, which was mediated by cyclin D1, CDK4, caspase-9 and caspase-3. Through mechanistic exploration, we found that miR-126-5p directly bound to LINC00665. Moreover, LINC00665 and miR-126-5p both regulated PAK2 and FZD3 expression. Mechanistically, miR-126-5p was predicted and further verified as a target of both PAK2 and FZD3. These findings demonstrate that LINC00665 might play an important pro-proliferative and antiapoptotic role in CRC and might be a potential biomarker and a new therapeutic target for CRC.

Nujiangexanthone A Inhibits Hepatocellular Carcinoma Metastasis via Down Regulation of Cofilin 1

Hepatocellular carcinoma (HCC) is one of the malignant tumors with poor prognosis. High expression level of cofilin 1 (CFL1) has been found in many types of cancers. However, the role of CFL1 in HCC hasn’t been known clearly. Here, we found that CFL1 was up regulated in human HCC and significantly associated with both overall survival and disease-free survival in HCC patients. Nujiangexanthone A (NJXA), the caged xanthones, isolated from gamboge plants decreased the expression of CFL1, which also inhibited the migration, invasion and metastasis of HCC cells in vitro and in vivo. Down regulation of CFL1 inhibited aggressiveness of HCC cells, which mimicked the effect of NJXA. Mechanism study indicated that, knockdown of CFL1 or treatment with NJXA increased the level of F-actin and disturbed the balance between F-actin and G-actin. In conclusion, our findings reveal the role of CFL1 in HCC metastasis through the CFL1/F-actin axis, and suggest that CFL1 may be a potential prognostic marker and a new therapeutic target. NJXA can effectively inhibit the metastasis of HCC cells by down regulating the expression of CFL1, which indicates the potential of NJXA for preventing metastasis in HCC.

Progesterone receptor membrane component 1 is involved in oral cancer cell metastasis

Cancer metastasis is a common cause of failure in cancer therapy. However, over 60% of oral cancer patients present with advanced stage disease, and the five‐year survival rates of these patients decrease from 72.6% to 20% as the stage becomes more advanced. In order to manage oral cancer, identification of metastasis biomarker and mechanism is critical. In this study, we use a pair of oral squamous cell carcinoma lines, OC3, and invasive OC3‐I5 as a model system to examine invasive mechanism and to identify potential therapeutic targets. We used two‐dimensional differential gel electrophoresis (2D‐DIGE) and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF/TOF MS) to examine the global protein expression changes between OC3 and invasive OC3‐I5. A proteomic study reveals that invasive properties alter the expression of 101 proteins in OC3‐I5 cells comparing to OC3 cells. Further studies have used RNA interference technique to monitor the influence of progesterone receptor membrane component 1 (PGRMC1) protein in invasion and evaluate their potency in regulating invasion and the mechanism it involved. The results demonstrated that expression of epithelial‐mesenchymal transition (EMT) markers including Twist, p‐Src, Snail1, SIP1, JAM‐A, vimentin and vinculin was increased in OC3‐I5 compared to OC3 cells, whereas E‐cadherin expression was decreased in the OC3‐I5 cells. Moreover, in mouse model, PGRMC1 is shown to affect not only migration and invasion but also metastasis in vivo. Taken together, the proteomic approach allows us to identify numerous proteins, including PGRMC1, involved in invasion mechanism. Our results provide useful diagnostic markers and therapeutic candidates for the treatment of oral cancer invasion.

CDK12 and PAK2 as novel therapeutic targets for human gastric cancer

Background: Gastric cancer remains the second leading cause of cancer-related death, and the third in mortality due to lack of effective therapeutic targets for late stage cancer patients. This study aims to identify potential druggable target biomarkers as potential therapeutic options for patients with gastric cancer.

Methods: Immunohistochemistry of human gastric tumor tissues was conducted to determine the expression level of cyclin-dependent kinase 12 (CDK12). Multiple in vitro and in vivo assays such as RNAi, mass spectrometry, computer docking models, kinase assays, cell xenograft NU/NU mouse models (CDXs) and patient-derived xenograft NOD/SCID mouse models (PDXs) were conducted to study the function and molecular interaction of CDK12 with p21 activated kinase 2 (PAK2), as well as to find CDK12 inhibitors as potential treatment options for human gastric cancer.

Results: Here we identified that CDK12 is a driver gene in human gastric cancer growth. Mechanistically, CDK12 directly binds to and phosphorylates PAK2 at T134/T169 to activate MAPK signaling pathway. We further identified FDA approved clinical drug procaterol can serve as an effective CDK12 inhibitor, leading to dramatic restriction of cancer cell proliferation and tumor growth in human gastric cancer cells and PDXs.

Conclusions: Our data highlight the potential of CDK12/PAK2 as therapeutic targets for patients with gastric cancer, and we propose procaterol treatment as a novel therapeutic strategy for human gastric cancer.

Celastrus orbiculatus extract suppresses the epithelial-mesenchymal transition by mediating cytoskeleton rearrangement via inhibition of the Cofilin 1 signaling pathway in human gastric cancer

Celastrus orbiculatus is a traditional medicinal plant used in the anti-inflammatory and analgesic treatment of various diseases. A previous study demonstrated that ethyl acetate extract of C. orbiculatus (COE) exhibited significant antitumor effects. However, studies concerning the effects and mechanism of COE in terms of suppressing the epithelial-mesenchymal transition (EMT) in human gastric adenocarcinoma cells have not been performed at present. The present study hypothesized that COE may inhibit EMT in gastric adenocarcinoma cells by regulating cell cytoskeleton rearrangement. The effect of COE on the viability of AGS cells was detected by MTT assay. An EMT model was induced by transforming growth factor-β1. Cell cytoskeleton staining, laser scanning confocal microscopy and electronic microscopy were used to detect the changes in cell morphology and microstructure of gastric adenocarcinoma cells prior and subsequent to COE treatment. Invasion and migration assays were used to observe the effect of COE on the metastatic ability of AGS cells in vitro. The effect of COE on the expression of Cofilin 1 and EMT biomarkers, including Epithelial-cadherin, Neural-cadherin, Vimentin and matrix metalloproteinases, was examined by western blotting in AGS cells. The correlation between Cofilin 1 and EMT was investigated with immunofluorescence and cytoskeleton staining methods. The results demonstrated that COE may significantly inhibit the process of EMT in AGS cells, and that this was concentration-dependent. In addition, COE significantly downregulated the level of Cofilin 1 in a concentration-dependent manner. In conclusion, these results suggested that Cofilin 1 was directly involved in the process of EMT in AGS cells, and that it served an important function. COE may significantly inhibit EMT in AGS cells, potentially by inhibiting the activation of the Cofilin 1 signaling pathway. The present study may provide a basis for the development of novel anticancer drugs and the development of novel therapeutic strategies, targeting Cofilin 1 protein.

Cofilin 1 induces the epithelial-mesenchymal transition of gastric cancer cells by promoting cytoskeletal rearrangement

Epithelial-mesenchymal transition (EMT) is an important biological process whereby malignant tumor cells obtain the ability to migrate, invade, resist apoptosis and degrade the extracellular matrix. We found that Cofilin1 (CFL1) expression was elevated in clinical gastric cancer specimens and correlated with biomarkers of EMT in BGC-823 gastric cancer cells. BGC-823 cells exhibited EMT phenotypes and increased metastatic ability when induced by TGF-β1. By contrast, BGC-823 cells transfected with Lv-siRNA-CFL1 did not exhibit EMT phenotypes under the same inducing conditions. As CFL1 expression increased, EMT cell filopodia stretched out. In addition, the ultrastructures observed using transmission electron microscopy indicated that silencing of CFL1 markedly inhibited depolymerization of fibrous actin and cytoskeletal reorganization during EMT. Similar results were obtained in vivo. These findings demonstrate that CFL1 induces EMT by promoting cytoskeletal rearrangement. Our results may provide the basis for developing new anticancer drugs to inhibit CFL1.

The dynamics of Rho GTPase signaling and implications for targeting cancer and the tumor microenvironment

Numerous large scale genomics studies have demonstrated that cancer is a molecularly heterogeneous disease, characterized by acquired changes in the structure and DNA sequence of tumor genomes. More recently, the role of the equally complex tumor microenvironment in driving the aggressiveness of this disease is increasingly being realized. Tumor cells are surrounded by activated stroma, creating a dynamic environment that promotes cancer development, metastasis and chemoresistance. The Rho family of small GTPases plays an essential role in the regulation of cell shape, cytokinesis, cell adhesion, and cell motility. Importantly, these processes need to be considered in the context of a complex 3-dimensional (3D) environment, with reciprocal feedback and cross-talk taking place between the tumor cells and host environment. Here we discuss the role of molecular networks involving Rho GTPases in cancer, and the therapeutic implications of inhibiting Rho signaling in both cancer cells and the emerging concept of targeting the surrounding stroma.

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

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

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

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

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

Overexpression of RhoGDI2 correlates with the progression and prognosis of pancreatic carcinoma

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been found to be a regulator of tumor metastasis. However, the expression of RhoGDI2 and its clinicopathological significance as well as the pathway of RhoGDI2 in tumor metastasis have yet to be investigated. To investigate the role of RhoGDI2 in the progression and prognosis of pancreatic carcinoma (PC), the expression of RhoGDI2 in human PC tissues was examined and compared with the clinicopathological characteristics and prognosis. Moreover, the relationship between RhoGDI2 and E-cadherin was examined. The results indicated that RhoGDI2 was overexpressed in PC tissues and associated with clinicopathological characteristics, including clinical stage and lymph node metastasis. Patients with a RhoGDI2‑negative expression had a significantly longer survival time than those with a RhoGDI2‑positive expression. Additionally, the expression of RhoGDI2 was negatively correlated with the expression of E-cadherin in PC tissues. Taken together, the findings suggest that RhoGDI2 is important in the progression and prognosis of PC, and may be used as a potential prognostic biomarker and a therapeutic target for PC.

RhoGDI2 promotes epithelial-mesenchymal transition via induction of Snail in gastric cancer cells

Rho GDP dissociation inhibitor 2 (RhoGDI2) expression correlates with tumor growth, metastasis, and chemoresistance in gastric cancer. Here, we show that RhoGDI2 functions in the epithelial-mesenchymal transition (EMT), which is responsible for invasiveness during tumor progression. This tumorigenic activity is associated with repression of E-cadherin by RhoGDI2 via upregulation of Snail. Overexpression of RhoGDI2 induced phenotypic changes consistent with EMT in gastric cancer cells, including abnormal epithelial cell morphology, fibroblast-like properties, and reduced intercellular adhesion. RhoGDI2 overexpression also resulted in decreased expression of the epithelial markers E-cadherin and β-catenin and increased expression of the mesenchymal markers vimentin and fibronectin. Importantly, RhoGDI2 overexpression also stimulated the expression of Snail, a repressor of E-cadherin and inducer of EMT, but not other family members such as Slug or Twist. RNA interference-mediated knockdown of Snail expression suppressed RhoGDI2-induced EMT and invasion, confirming that the effect was Snail-specific. These results indicate that RhoGDI2 plays a critical role in tumor progression in gastric cancer through induction of EMT. Targeting RhoGDI2 may thus be a useful strategy to inhibit gastric cancer cell invasion and metastasis.

14-3-3σ attenuates RhoGDI2-induced cisplatin resistance through activation of Erk and p38 in gastric cancer cells

Rho GDP dissociation inhibitor 2 (RhoGDI2) promotes tumor growth and malignant progression and enhances chemoresistance of gastric cancer. Recently, we noted an inverse correlation between RhoGDI2 and 14-3-3σ expression, which suggests that 14-3-3σ is a target of gastric cancer metastasis and the chemoresistance-promoting effect of RhoGDI2. Herein, we evaluated whether 14-3-3σ is regulated by RhoGDI2 and is functionally important for the RhoGDI2-induced cisplatin resistance of gastric cancer cells. We used highly metastatic and cisplatin-resistant RhoGDI2-overexpressing SNU-484 cells and observed decreased 14-3-3σ mRNA and protein expression. Depletion of 14-3-3σ in SNU-484 control cells enhanced cisplatin resistance, whereas restoration of 14-3-3σ in RhoGDI2-overexpressing SNU-484 cells impaired cisplatin resistance in vitro and in vivo. We also found that the phosphorylation levels of Erk and p38 kinases significantly decreased in RhoGDI2-overexpressing SNU-484 cells and recovered after 14-3-3σ expression, and that decreased activities of these kinases were critical for RhoGDI2-induced cisplatin resistance. In conclusion, 14-3-3σ is a RhoGDI2-regulated gene that appears to be important for suppressing the chemoresistance of gastric cancer cells.

Expression of RhoGDI2 and CIAPIN1 in gastric carcinoma

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

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

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

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

Depletion of RhoGDI2 expression inhibits the ability of invasion and migration in pancreatic carcinoma

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been identified as a regulator of tumor metastasis, although its role in tumor progression remains controversial. In this study, we examined the expression of RhoGDI2 in PC tissues and cell lines. To investigate the function of RhoGDI2 in PC cells, RhoGDI2 expression was depleted in PANC-1 and Patu8988 cells by small interfering RNA (siRNA). RhoGDI2 was found to be overexpressed in pancreatic carcinoma (PC) tissues and PC cell lines. Additionally, the results showed that depletion of RhoGDI2 significantly inhibited cell motility and invasion in vitro, but did not affect cell proliferation. The clinical study together with the experimental data confirmed that RhoGDI2 modulated the expression of matrix metalloproteinase 2 (MMP2). Taken together, findings of the present study indicated that RhoGDI2 is involved in pancreatic tumor malignancy and metastasis. Thus, RhoGDI2 is a potential target for the gene therapy of PC.

A monotonic and prognostic genomic signature from fibroblasts for colorectal cancer initiation, progression, and metastasis

The differential gene expression patterns between normal colonic fibroblasts (NCF), carcinoma-associated fibroblasts from primary tumors (CAF-PT), and CAFs from hepatic metastasis (CAF-LM) are hypothesized to be useful for predicting relapse in primary tumors. A transcriptomic profile of NCF (n = 9), CAF-PT (n = 14), and CAF-LM (n = 11) was derived. Prediction Analysis of Microarrays (PAM) was used to obtain molecular details for each fibroblast class, and differentially expressed transcripts were used to classify patients according to recurrence status. A number of transcripts (n = 277) were common to all three types of fibroblasts and whose expression level was sequentially deregulated according to the transition: NCF→CAF-PT→CAF-LM. Importantly, the gene signature was able to accurately classify patients with primary tumors according to their prognosis. This capacity was exploited to obtain a refined 19-gene classifier that predicted recurrence with high accuracy in two independent datasets of patients with colorectal cancer and correlates with fibroblast migratory potential. The prognostic power of this genomic signature is strong evidence of the link between the tumor-stroma microenvironment and cancer progression. Furthermore, the 19-gene classifier was able to identify low-risk patients very accurately, which is of particular importance for stage II patients, who would benefit from the omission of chemotherapy, especially T4N0 patients, who are clinically classified as being at high risk.

IMPLICATIONS

A defined stromal gene expression signature predicts relapse in patients with colorectal cancer.

Identification of reproducible gene expression signatures in lung adenocarcinoma

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide. Tremendous research efforts have been devoted to improving treatment procedures, but the average five-year overall survival rates are still less than 20%. Many biomarkers have been identified for predicting survival; challenges arise, however, in translating the findings into clinical practice due to their inconsistency and irreproducibility. In this study, we proposed an approach by identifying predictive genes through pathways.

RESULTS

The microarrays from Shedden et al. were used as the training set, and the log-rank test was performed to select potential signature genes. We focused on 24 cancer-related pathways from 4 biological databases. A scoring scheme was developed by the Cox hazard regression model, and patients were divided into two groups based on the medians. Subsequently, their predictability and generalizability were evaluated by the 2-fold cross-validation and a resampling test in 4 independent datasets, respectively. A set of 16 genes related to apoptosis execution was demonstrated to have good predictability as well as generalizability in more than 700 lung adenocarcinoma patients and was reproducible in 4 independent datasets. This signature set was shown to have superior performances compared to 6 other published signatures. Furthermore, the corresponding risk scores derived from the set were found to associate with the efficacy of the anti-cancer drug ZD-6474 targeting EGFR.

CONCLUSIONS

In summary, we presented a new approach to identify reproducible survival predictors for lung adenocarcinoma, and the identified genes may serve as both prognostic and predictive biomarkers in the future.

Clinicopathological significance of expression of RhoGDI2 in gastric carcinoma

AIM: To detect the expression of RhoGTPase dissociation inhibitor 2 (RhoGDI2) in gastric cancer, and to assess its correlation with clinicopathological characteristic of gastric cancer.

METHODS: Immunohistochemistry was used to detect the expression of RhoGDI2 in 103 gastric cancer specimens.

RESULTS: RhoGDI2 was expressed mainly in the cytoplasm or the nucleus. The positive rate of RhoGDI2 protein expression was significantly higher in gastric cancer than in normal gastric tissue (72.82% vs 0.00%, χ² = 38.70, P < 0.05). The expression of RhoGDI2 protein was significantly correlated with tumor differentiation, invasion, lymph node metastasis, distant metastasis and stage (χ² = 6.37, 21.64, 54.50, 19.81, 24.90, all P < 0.05), but not with gender, age, tumor location or size.

CONCLUSION: The expression of RhoGDI2 is closely related to the invasion and metastasis of gastric cancer.