HCRP-1 regulates cell migration and invasion via EGFR-ERK mediated up-regulation of MMP-2 with prognostic significance in human renal cell carcinoma

Corosolic acid inhibits metastatic response of human renal cell carcinoma cells by modulating ERK/MMP2 signaling

Corosolic acid (CA), a plant-derived pentacyclic triterpenoid, has potent anti-inflammatory, anti-metabolic, and anti-neoplastic actions against a variety of human cancers. However, the specific mechanism by which CA inhibits the progression of renal cell carcinoma (RCC) is yet unclear. We found that CA (≤8 μM) had no influence on either the growth or viability of RCC cell lines (786-O, ACHN, and Caki-1) or normal HK2 cells. However, in a dose-dependent manner, CA prevented the invasion and migration of RCC cells. Human protease array analysis showed that CA reduced MMP2 expression. At increasing concentrations of CA, the expression of MMP2 was dose-dependently reduced, as shown by western blot and RT-PCR analyses as well as immunofluorescence staining. CA also stimulated ERK1/2 phosphorylation in 786-O and Caki-1 cells. Transfection of CA-treated RCC cells with siRNA-ERK restored MMP2 protein expression and the motility and invasion capabilities of RCC cells. Molecular docking study results showed that CA and MMP2 interact strongly. These findings elucidate the mechanism by which CA prevents RCC cells from migrating and invading, and these findings indicate that CA may be a potential anti-metastatic therapy for RCC.

Asiatic acid from centella asiatica exert anti-invasive ability in human renal cancer cells by modulation of ERK/p38MAPK-mediated MMP15 expression

BACKGROUND

Asiatic acid (AA) is a naturally pentacyclic triterpenoids extracted from traditional medicine Centella asiatica l. that has demonstrated possesses potential health benefits and antitumor ability. However, the precise anticancer effects and mechanisms by which AA impact RCC cells remains unclear.

METHODS

Cell proliferation and cell cycle distribution were detected by MTT, colony formation assay and PI stain by flow cytometry, respectively. Cell mobility and invasiveness were determined by in vitro migration and invasion assay. The secretory MMP15 was detected by ELISA assay. Quantitative RT-PCR, siRNA, and immunoblot were used to determine gene expression/regulation and protein expression, respectively. Antimetastatic effect of AA were performed to lung nodule numbers in vivo metastasis mice model. MMP15, pERK1/2 and p-p38MAPK expressions were determined by immunohistochemistry.

RESULTS

Our findings indicated cell proliferation and cell cycle distribution of RCC cells were not significantly influenced by AA treatment. AA suppressed cell migration, invasion and significantly down-regulated mRNA and protein expression of MMP-15 (Matrix Metallopeptidase-15). Activation of ERK1/2 and p38MAPK were inhibited with AA, whereas combined AA with siRNA-ERK or siRNA-p38MAPK markedly reduced the metastatic effect and decreased MMP-15 expression in 786-O and A498 cells. Finally, AA significantly reduced the lung metastasis formation and metastasis-related proteins of human 786-O cells in vivo metastasis mice model.

CONCLUSION

AA inhibits the metastatic properties of RCC cells via inhibition of the p-ERK/p-p38MAPK axis and the subsequent down-regulation of MMP-15 in vitro and in vivo. Further study of AA as a potential anti-metastatic agent for RCC is warranted.

SPARC is a key mediator of TGF-β-induced renal cancer metastasis

Aberrant expression of transforming growth factor-β1 (TGF-β1) is associated with renal cell carcinoma (RCC) progression by inducing cancer metastasis. However, the downstream effector(s) in TGF-β signaling pathway is not fully characterized. In the present study, the elevation of secreted protein acidic and rich in cysteine (SPARC) as a TGF-β regulated gene in RCC was identified by applying differentially expressed gene analysis and microarray analysis, we further confirmed this result in several RCC cell lines. Clinically, the expression of these two genes is positively correlated in RCC patient specimens. Furthermore, elevated SPARC expression is found in all the subtypes of RCC and positively correlated with the RCC stage and grade. In contrast, SPARC expression is inversely correlated with overall and disease-free survival of patients with RCC, suggesting SPARC as a potent prognostic marker of RCC patient survival. Knocking down SPARC significantly inhibits RCC cell invasion and metastasis both in vitro and in vivo. Similarly, in vitro cell invasion can be diminished by using a specific monoclonal antibody. Mechanistically, SPARC activates protein kinase B (AKT) pathway leading to elevated expression of matrix metalloproteinase-2 that can facilitate RCC invasion. Altogether, our data support that SPARC is a critical role of TGF-β signaling network underlying RCC progression and a potential therapeutic target as well as a prognostic marker.

Modulation of the ERK1/2-MMP-2 pathway in the sclera of guinea pigs following induction of myopia by flickering light

It has been shown that flickering light can affect the development of eyeballs. However, the exact mechanism remains unclear. The ERK1/2-MMP-2 pathway is a classic pathway involved in the modulation of the extracellular matrix (ECM) in cancer tissues. However, to the best of our knowledge, the role of this pathway in modulating the scleral ECM in myopia has not been previously examined. The present study aimed to determine the effects of the ERK1/2-MMP-2 pathway on the formation of flickering light-induced myopia (FLM). Guinea pigs were raised under illumination at a flash rate of 0.5 Hz for 6 weeks to induce FLM. Peribulbar injections of dimethylsulfoxide or PD98059 (an inhibitor of phospho-ERK1/2) were administered starting at the third week of FLM modeling. Refraction was measured prior to and following treatments. The thickness of the posterior sclera (PS) was measured under a light microscope following H&E staining. The mRNA levels of MMP-2 were detected by the reverse transcription-quantitative PCR assay. The expression levels of MMP-2 and ERK1/2 were assayed by western blot and immunohistochemical analyses. Following 6 weeks of treatment, the refraction of the FLM group became more myopic compared with that of the control group, while PD98059 treatment inhibited the changes noted in the refraction. A marked reduction in the thickness of PS was observed in the FLM group, while PD98059 inhibited the remodeling of PS. In addition, the expression levels of MMP-2 and protein levels of phospho-ERK1/2 were increased in the FLM group, while PD98059 significantly inhibited MMP-2 mRNA and protein levels. These results indicated that ERK1/2-MMP-2 may be involved in the formation of FLM in guinea pigs by regulating the remodeling of PS.

Concurrent depletion of Vps37 proteins evokes ESCRT-I destabilization and profound cellular stress responses

Molecular details of how endocytosis contributes to oncogenesis remain elusive. Our in silico analysis of colorectal cancer (CRC) patients revealed stage-dependent alterations in the expression of 112 endocytosis-related genes. Among them, transcription of the endosomal sorting complex required for transport (ESCRT)-I component VPS37B was decreased in the advanced stages of CRC. Expression of other ESCRT-I core subunits remained unchanged in the investigated dataset. We analyzed an independent cohort of CRC patients, which also showed reduced VPS37A mRNA and protein abundance. Transcriptomic profiling of CRC cells revealed non-redundant functions of Vps37 proteins. Knockdown of VPS37A and VPS37B triggered p21 (CDKN1A)-mediated inhibition of cell proliferation and sterile inflammatory response driven by the nuclear factor (NF)-κB transcription factor and associated with mitogen-activated protein kinase signaling. Co-silencing of VPS37C further potentiated activation of these independently induced processes. The type and magnitude of transcriptional alterations correlated with the differential ESCRT-I stability upon individual and concurrent Vps37 depletion. Our study provides novel insights into cancer cell biology by describing cellular stress responses that are associated with ESCRT-I destabilization.

Knockdown of ALPK2 blocks development and progression of renal cell carcinoma

Renal cell carcinoma (RCC) is one of the most common malignant tumors in the urinary system, whose molecular mechanism is still not clear. ALPK2 is a member of alpha protein kinase family, and its relationship with RCC is never reported. In this study, expression of ALPK2 in tumor tissues or cells of RCC was detected by qPCR, western blotting and immunohistochemical analysis. The effects of ALPK2 knockdown on cell proliferation, colony formation, cell migration and apoptosis were assessed by MTT, colony formation assay, wound-healing assay, Transwell assay and flow cytometry, respectively. The influence of ALPK2 knockdown on tumor growth in vivo was evaluated by mice xenograft models. The results demonstrated that ALPK2 was upregulated in tumor tissues of RCC and its high expression was significantly associated with advanced stage and poor prognosis. Knockdown of ALPK2 could inhibited cell proliferation, colony formation and cell migration of RCC cells, while promoting cell apoptosis. The suppression of tumor growth in vivo by ALPK2 knockdown was also showed by using mice xenograft models. Moreover, the regulation of RCC by ALPK2 may involve Akt, CDK6, Cyclin D1 and PIK3CA signaling. Therefore, our studies suggested that ALPK2 may act as a tumor promotor in the development and progression of RCC, and could be considered as a novel therapeutic target for RCC treatment.

VHL-HIF-2α axis-induced SMYD3 upregulation drives renal cell carcinoma progression via direct trans-activation of EGFR

It has been well established that the von Hippel-Lindau/hypoxia-inducible factor α (VHL-HIFα) axis and epidermal growth factor receptor (EGFR) signaling pathway play a critical role in the pathogenesis and progression of renal cell carcinoma (RCC). However, few studies have addressed the relationship between the two oncogenic drivers in RCC. SET and MYND domain-containing protein 3 (SMYD3) is a histone methyltransferase involved in gene transcription and oncogenesis, but its expression and function in RCC remain unclear. In the present study, we found that SMYD3 expression was significantly elevated in RCC tumors and correlated with advanced tumor stage, histological and nuclear grade, and shorter survival. Depletion of SMYD3 inhibited RCC cell proliferation, colony numbers, and xenograft tumor formation, while promoted apoptosis. Mechanistically, SMYD3 cooperates with SP1 to transcriptionally promote EGFR expression, amplifying its downstream signaling activity. TCGA data analyses revealed a significantly increased SMYD3 expression in primary RCC tumors carrying the loss-of-function VHL mutations. We further showed that HIF-2α can directly bind to the SMYD3 promoter and subsequently induced SMYD3 transcription and expression. Taken together, we identify the VHL/HIF-2α/SMYD3 signaling cascade-mediated EGFR hyperactivity through which SMYD3 promotes RCC progression. Our study suggests that SMYD3 is a potential therapeutic target and prognostic factor in RCC.

G6PD facilitates clear cell renal cell carcinoma invasion by enhancing MMP2 expression through ROS‑MAPK axis pathway

Glucose-6-phosphate dehydrogenase (G6PD) is crucial rate-limiting enzyme of the pentose phosphate pathway (PPP). G6PD dysregulation has been reported in various types of human cancer, and the role of G6PD in cancer progression was demonstrated in numerous studies. A previous study from our laboratory described the prognostic significance of G6PD in clear cell renal cell carcinoma (ccRCC), and demonstrated its proliferative role through positive feedback regulation of the phosphorylated form of signal transducer and activator of transcription 3. However, the role of G6PD in ccRCC invasion remains unclear. In the present study, reverse transcription-quantitative (RT-q) PCR, western blotting, enzyme activity assay, transwell assay and immunohistochemistry analysis in cell model, xenograft mice model and human specimen studies were performed to evaluate the role of G6PD in ccRCC invasion. The results from the present study demonstrated that G6PD may promote ccRCC cell invasive ability by increasing matrix metalloproteinase 2 (MMP2) mRNA and protein expression both in vitro and in vivo. In addition, a positive correlation between G6PD and MMP2 expression was demonstrated by RT-qPCR and western blotting in twenty pairs of ccRCC tumor specimens and matched adjacent normal tissues. Furthermore, G6PD promoted reactive oxygen species (ROS) generation and activated the MAPK signaling pathway in ccRCC cells. In addition, ROS significantly promoted the MAPK signaling pathway activation, which in turn contributed to MMP2 overexpression in ccRCC cells. In conclusion, the present study demonstrated that G6PD may facilitate ccRCC cell invasive ability by enhancing MMP2 expression through ROS-MAPK axis pathway.

Ginkgolic acid inhibits the growth of renal cell carcinoma cells via inactivation of the EGFR signaling pathway

Renal cell carcinoma (RCC) is one of the most common urological malignancies occurring in adult human kidneys worldwide. Recent research on antitumor drugs has focused on plant extracts, a class of compounds that play critical roles in cancer treatment. The present study aimed to investigate the potential antitumor effect of ginkgolic acid (GA) in RCC. Transwell invasion assay, cell counting kit-8 assay and flow cytometry were used to measure cell migration, cell viability and apoptosis, respectively. A network pharmacology approach was applied to identify pathway information, combining molecular docking techniques to screen for key target information. In the present study, GA inhibited the viability and proliferation of RCC cells (786-O and A498), both in vitro and in vivo, via G₁ arrest. GA also reduced RCC cell invasion and migration. In addition, the epidermal growth factor receptor (EGFR) was identified as a critical target protein of GA, which significantly inactivated EGFR signaling in RCC (P<0.05). Collectively, the present study provided evidence that GA exerts its anticancer function by directly targeting the EGFR signaling pathway, revealing the potential of GA therapy for RCC.

HCRP-1 regulates cell migration, invasion and angiogenesis via Src/ FAK signaling in human prostate cancer

Prostate cancer (PCa) is the third leading malignancy engendering mortality among men globally. The present study aimed at determining the expression of hepatocellular carcinoma-related protein-1 (HCRP-1) in PCa, to explore its potential role in prostate tumorigenesis in vitro and in vivo. We evaluated HCRP-1 protein with immunohistochemistry (IHC) technology and found HCRP-1 expression was significantly low in PCa tissues (PCTs); In addition, the decreased HCRP-1 was significantly associated with TNM (tumor node metastasis) stage, advanced histology grade and gleason score. Transwell, tube formation, Western blot and co-immunoprecipitation (Co-IP) assays were utilized to determine the role of down-regulating HCRP-1 in PCa cell migration, invasion and angiogenesis. Meanwhile, we found HCRP-1 depletion induced Src and focal adhesion kinase (FAK) phosphorylation, which could be reversed by Src inhibitor PP2 or FAK inhibitor. Furthermore, down-regulated HCRP-1 evidently induced lung metastasis of PCa cells in xenograft mode. Taken together, our study indicates HCRP-1 plays an important role in PCa metastasis. HCRP-1 may serve as a potential therapeutic target for PCa.

RNF128 Promotes Invasion and Metastasis Via the EGFR/MAPK/MMP-2 Pathway in Esophageal Squamous Cell Carcinoma

Background: The prognosis of esophageal squamous cell carcinoma (ESCC) is generally poor, and the identification of molecular markers related to the regulation of ESCC invasion and migration is important. Methods and Results: In this study, we report that ring finger protein-128 (RNF128) enhances the invasiveness and motility of ESCC cells by using transwell assays and Western blotting. A xenograft nude mouse model showed that RNF128 promotes the metastasis of ESCC cells in the lung. A signal pathway analysis identified the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK)/matrix matalloproteinases 2 (MMP-2) cascade as a mediator of RNF128-induced enhancement of ESCC progression. Inhibition experiments using inhibitors of EGFR, ERK kinase (MEK)/extracellular-signal-regulated-kinase (ERK), and MMP-2 reversed this progression. Co-immunoprecipitation demonstrated that RNF128 promotes the activation of the EGFR/ERK/MMP-2 pathway by interacting with p53 and p53 interacting with EGFR. Conclusion: Our results establish the functional role of RNF128 in driving the invasion and metastasis of ESCC through the EGFR/MAPK/MMP-2 pathway, implicating its potential as a candidate therapeutic target and prognostic biomarker for ESCC.

Molecular mechanisms involved in the protective effect of pituitary adenylate cyclase-activating polypeptide in an in vitro model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of upper and lower motor neurons. Based on transcriptional profiles of motor cortex samples, in a previous work, we were able to classify two subgroups of sporadic ALS (SALS) patients, named SALS1 and SALS2. A further meta-analysis study has revealed sixteen drug targets commonly deregulated in SALS2 and superoxide dismutase 1 (SOD1) G93A mice. The identified candidate drug targets included pituitary adenylate cyclase-activating polypeptide (PACAP), epidermal growth factor receptor (EGFR) and matrix metallopeptidase-2 (MMP-2). By using a motor neuron-like hybrid cell line (NSC-34) expressing human SOD1 G93A as an in vitro model of ALS, here we investigated the functional correlation among these three genes. Our results have shown that PACAP increases cell viability following serum deprivation. This effect is induced through EGFR transactivation mediated by protein kinase A stimulation. Furthermore, EGFR phosphorylation activates mitogen-activated protein kinases/extracellular signal-regulated kinases 1 and 2 survival signaling pathway and increases MMP-2 expression, significantly reduced by serum starvation. These results suggest that a deeper characterization of mechanisms involved in PACAP/EGFR/MMP-2 axis activation in G93A SOD1 mutated neurons may allow identifying new targets for ALS therapy.

Hypoxia-Inducible Factor 2-Dependent Pathways Driving Von Hippel-Lindau-Deficient Renal Cancer

The most common type of the renal cancers detected in humans is clear cell renal cell carcinomas (ccRCCs). These tumors are usually initiated by biallelic gene inactivation of the Von Hippel-Lindau (VHL) factor in the renal epithelium, which deregulates the hypoxia-inducible factors (HIFs) HIF1α and HIF2α, and provokes their constitutive activation irrespective of the cellular oxygen availability. While HIF1α can act as a ccRCC tumor suppressor, HIF2α has emerged as the key HIF isoform that is essential for ccRCC tumor progression. Indeed, preclinical and clinical data have shown that pharmacological inhibitors of HIF2α can efficiently combat ccRCC growth. In this review, we discuss the molecular basis underlying the oncogenic potential of HIF2α in ccRCC by focusing on those pathways primarily controlled by HIF2α that are thought to influence the progression of these tumors.

The E3 ubiquitin ligase NEDD4 mediates cell migration signaling of EGFR in lung cancer cells

BACKGROUND

EGFR-dependent cell migration plays an important role in lung cancer progression. Our previous study observed that the HECT E3 ubiquitin ligase NEDD4 is significantly correlated with tumor metastasis and required for migration and invasion signaling of EGFR in gastric cancer cells. However, how NEDD4 promotes the EGFR-dependent lung cancer cell migration is unknown. This study is to elucidate the mechanism by which NEDD4 mediates the EGFR lung cancer migration signaling.

METHODS

Lentiviral vector-loaded NEDD4 shRNA was used to deplete endogenous NEDD4 in lung cancer cell lines. Effects of the NEDD4 knockdown on the EGFR-dependent or independent lung cancer cell migration were determined using the wound-healing and transwell assays. Association of NEDD4 with activated EGFR was assayed by co-immunoprecipitation. Co-expression of NEDD4 with EGFR or PTEN was determined by immunohistochemical (IHC) staining in 63 lung adenocarcinoma tissue samples. Effects of NEDD4 ectopic expression or knockdown on PTEN ubiquitination and down-regulation, AKT activation and lysosomal secretion were examined using the GST-Uba pulldown assay, immunoblotting, immunofluorescent staining and a human cathepsin B ELISA assay respectively. The specific cathepsin B inhibitor CA-074Me was used for assessing the role of cathepsin B in lung cancer cell migration.

RESULTS

Knockdown of NEDD4 significantly reduced EGF-stimulated cell migration in non-small cell lung carcinoma (NSCLC) cells. Co-immunoprecipitation assay found that NEDD4 is associated with EGFR complex upon EGF stimulation, and IHC staining indicates that NEDD4 is co-expressed with EGFR in lung adenocarcinoma tumor tissues, suggesting that NEDD4 might mediate lung cancer cell migration by interaction with the EGFR signaling complex. Interestingly, NEDD4 promotes the EGF-induced cathepsin B secretion, possibly through lysosomal exocytosis, as overexpression of the ligase-dead mutant of NEDD4 impedes lysosomal secretion, and knockdown of NEDD4 significantly reduced extracellular amount of cathepsin B induced by EGF. Consistent with the role of NEDD4, cathepsin B is pivotal for both basal and the EGF-stimulated lung cancer cell migration. Our studies propose a novel mechanism underlying the EGFR-promoted lung cancer cell migration that is mediated by NEDD4 through regulation of cathepsin B secretion.

CONCLUSION

NEDD4 mediates the EGFR lung cancer cell migration signaling through promoting lysosomal secretion of cathepsin B.

MiR-514a-3p inhibits cell proliferation and epithelial-mesenchymal transition by targeting EGFR in clear cell renal cell carcinoma

PURPOSE

Dysregulation of miR-514a-3p has been reported in multiple human malignancies. However, its biological function and molecular mechanisms in renal cell cancer (RCC) remain unclear. The aims of this study were to explore the role of miR-514a-3p and its potential mechanism in human RCC.

METHODS

The expression level of miR-514a-3p was quantified by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) in 20 cases of paired ccRCC and adjacent normal tissues and RCC cell lines. The role of miR-514a-3p in RCC cells was further evaluated by functional analyses. Western blot was applied to probe into the biological mechanism of miR-514a-3p in RCC cells.

RESULTS

The qRT-PCR results confirmed that miR-514a-3p was dramatically down-regulated in ccRCC specimens. Restoration of miR-514a-3p expression might distinctively suppress cell proliferation, viability, migration and invasion in comparison with negative control in RCC cells and negatively regulate the proteins related to epithelial-mesenchymal transition (EMT), such as E-Cadherin, N-Cadherin and Vimentin. Results of luciferase reporter assay and Western blot analysis identified that miR-514a-3p might inversely regulate the expression of epidermal growth factor receptor (EGFR) directly by binding to its 3'-untranslated region (3'-UTR) at the translational level. Further studies showed that the phenotypic changes of RCC cells caused by miR-514a-3p occurred through EGFR/MAPK/ERK pathway rather than PI3K/AKT signaling. Moreover, the inhibitory effect of miR-514a-3p was also confirmed in vivo study.

CONCLUSIONS

MiR-514a-3p is a novel tumor suppressor in ccRCC and potentially functions through EGFR/MAPK/ERK pathway.

18 β-glycyrrhetinic acid exhibits potent antitumor effects against colorectal cancer via inhibition of cell proliferation and migration

Accumulating evidence shows that 18 β-glycyr-rhetinic acid (GRA) has antitumor activities in breast, ovarian cancer and leukemia, while its role in colorectal cancer remains unknown. In the present study, we investigated the effect of GRA in colorectal cancer cells LoVo, SW480 and SW620 and studied the underlying molecular mechanisms. Results showed that GRA had potent inhibitory effects on colorectal cancer cell proliferation in a dose- and time-dependent manner in vitro and in vivo. Growth inhibition was mediated by pro-apoptosis, as evident from Annexin V-FITC staining, the reduced expression of survivin and the induced expression of cleaved PARP. Furthermore, GRA treatment resulted in marked reduction of cell migration, invasion and wound healing capability, accompanying by the downregulated MMP expression. Moreover, GRA decreased the protein levels of p-PI3K, p-AKT, p-STAT3, p-JNK, p-p38 and p-NF-κB p65, of which the phosphorylation of PI3K and STAT3 decreased as early as 2 h after the GRA treatment. These results suggest that regulation of the apoptosis, invasion and migration of colorectal cancer cells by GRA might be through suppressing PI3K and STAT3 signaling pathways. the present study indicated that GRA could be a potential effective therapy for patients with colorectal cancer.

Slit2 and Robo1 induce opposing effects on metastasis of hepatocellular carcinoma Sk-hep-1 cells

The neural guidance molecular, Slit2, and its cognate receptor, Robo1, play critical roles in the development of the nervous system, nevertheless, their functions are not limited to this system. Numerous studies have shown decreased Slit2 expression in a wide variety of cancers, highlighting its potential as a tumor suppressor. However, the Slit2/Robo1 signaling axis was reported to induce either suppressive or stimulatory effects on tumor growth and metastasis, depending on cellular context. There is a paucity of information on the effects of the Slit2/Robo1 signaling axis on the growth and metastasis of human hepatocellular carcinoma (HCC). Large-scale data mining of the Oncomine database has revealed heterogeneous expression of Slit2 in HCC. We screened the Sk-hep-1, a cell line showing a relatively high level of Slit2, and low level of Robo1 expression. After Slit2 knockdown and Robo1 overexpression in these cells, we found Slit2 and Robo1 exerted opposing effects on tumor growth and metastasis both in in vitro and in vivo models. Slit2 knockdown and Robo1 overexpression in Sk-hep-1 cells promoted tumor growth and metastasis, suggesting a negative and positive role for Slit2 and Robo1, respectively, in tumor progression. Robo1 overexpression upregulated matrix metalloproteinase (MMP)2, -9 and membrane-type1 MMP (MT1-MMP) expression, stimulated MMP2, but not MMP9 activation, and downregulated expression of TIMP1 and 2. The PI3K/Akt signaling pathway is of importance in regulating MMP2 expression in Sk-hep-1 cells, since Robo1 overexpression stimulated phosphorylation of Akt while the PI3K inhibitor LY294002, significantly inhibited the upregulation of MMP2 and also the enhanced cell invasion induced by Robo1 overexpression. We postulate that Robo1 promotes tumor invasion partly by the upregulation of MMP2 after activation of PI3K/Akt signaling pathway. Notably, Slit2 knockdown caused the upregulation of Robo1 expression both at the mRNA and protein levels. Thus, the stimulatory effects of Slit2 knockdown on tumor progression can be ascribed, at least in part, to the upregulation of Robo1 and its positive role in tumor progression.

Meloxicam suppresses hepatocellular carcinoma cell proliferation and migration by targeting COX-2/PGE2-regulated activation of the β-catenin signaling pathway

Recurrence and metastasis are the two leading causes of poor prognosis of hepatocellular carcinoma (HCC) patients. Cyclooxygenase (COX)-2 is overexpressed in many types of cancers including HCC and promotes its metastasis. Meloxicam is a selective COX-2 inhibitor that has been reported to exert an anti-proliferation and invasion/migration response in various tumors. In this study, we examined the role of meloxicam on HCC cell proliferation and migration and explored the molecular mechanisms underlying this effect. We found that meloxicam inhibited HCC cell proliferation and had a cell cycle arrest effect in human HCC cells. Furthermore, meloxicam suppressed the ability of HCC cells expressing higher levels of COX-2 and prostaglandin E2 (PGE2) to migration via potentiating expression of E-cadherin and alleviating expression of matrix metalloproteinase (MMP)-2 and -9. COX-2/PGE2 has been considered to activate the β-catenin signaling pathway which promotes cancer cell migration. We found that treatment with PGE2 significantly enhanced nuclear accumulation of β-catenin and the activation of GSK3β which could be reversed by meloxicam in HCC cells. We also observed that HCC cell migration and upregulation of the level of MMP-2/9 and downregulation of E-cadherin induced by PGE2 were suppressed by FH535, an inhibitor of β-catenin. Taken together, these findings provide a new treatment strategy against HCC proliferation and migration.