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Background: Trefoil factor family 1 (TFF1) is a member of the TFF-domain peptide family involved in epithelial restitution and cell motility. Recently, we screened Piezo1 as a candidate TFF1-binding protein., Aim: We aimed to confirm Piezo1 as a novel TFF1 binding protein and to assess the role of this interaction in mediating gastric cancer cell mobility., Methods: This interaction was confirmed by co-immunoprecipitation and co-localisation of TFF1 and Piezo1 in GES-1 cells. We used stable RNA interference to knockdown Piezo1 protein expression and restored the expression of TFF1 in the gastric cancer cell lines SGC-7901 and BGC-823. Cell motility was evaluated using invasion assay and migration assay in vitro. The expression levels of the integrin subunits β1, β5, α1 as well as the expression of β-catenin and E-cadherin were detected by Western blot., Results: We demonstrate that TFF1, but not TFF2 or TFF3, bind to and co-localize with Piezo1 in the cytoplasm in vitro. TFF1 interacts with the C-terminal portion of the Piezo1 protein. Wound healing and trans-well assays demonstrated that the restored expression of TFF1 promoted cell mobility in gastric cancer cells, and this effect was attenuated by the knockdown of Piezo1. Western blots demonstrated the decreased expression of integrin β1 in Piezo1-knockdown cells., Conclusions: Our data demonstrate that Piezo1 is a novel TFF1 binding protein that is important for TFF1-mediated cell migration and suggest that this interaction may be a therapeutic target in the invasion and metastasis of gastric cancer.

Background and Aims: EGFR activation and PKM2 expression are instrumental in tumorigenesis. EGFR activation regulates PKM2 functions in a subcellular compartment-dependent manner and promotes gene transcription and tumor growth. In addition, PKM2 is upregulated in EGFR-induced pathways in glioma malignancies. However, we found that PKM2 could also regulate the activity of the EGF/EGFR signaling pathway in gastric cancer cells. We aimed to define the biological mechanisms for PKM2 in regulating the cell motility and invasion., Methods: We employed stable transfection with short hairpin RNA to stably silence the expression of PKM2 in the BGC823, SGC7901 and AGS gastric cancer cell lines. The effects of PKM2 in vitro were determined by assessing cell migration and invasion. Immunohistochemical analysis was used to explore the relationship among PKM2 and other proteins., Results: Our results indicate that the knockdown of PKM2 decreased the activity of E-cadherin and enhanced the EGF/EGFR signaling pathway in the gastric cell lines BGC823 and SGC7901 that were positive for E-cadherin expression. However, in the undifferentiated gastric carcinoma cell line AGS, which lacks E-cadherin expression, PKM2 promoted cell migration and invasion. Immunohistochemical analyses showed that the levels of E-cadherin expression, ERK1/2 phosphorylation, and cytoplasmic PKM2 expression were correlated with each other., Conclusion: PKM2 may play different roles in differently differentiated gastric cancer cell types, and this finding would be consistent with the previous clinical research. The results of our study reveal an important link between PKM2 and E-cadherin during EGFR-stimulated gastric cancer cell motility and invasion.

We aimed to confirm the role of ECHS1 as a binding protein of HBsAg (HBs) and investigate its function during the development of hepatocellular carcinoma (HCC). Our results show that both exogenous and endogenous ECHS1 proteins bind to HBs and co-localize in the cytoplasm in vitro. The coexistence of HBs and ECHS1 enhances HepG2 cell apoptosis, affects ECHS1 localization in the mitochondria and induces apoptosis by decreasing the mitochondrial membrane potential (MMP). These findings suggest that ECHS1 may be applied as a potential therapeutic target during the treatment of HBV-related hepatitis or HCC., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Background and Aim: Aplasia ras homolog member I (ARHI) is a maternally imprinted tumor suppressor gene. ARHI protein is widely expressed in many types of human tissues; however, its expression is frequently reduced or absent in various tumors and plays a tumor suppressor role for in vitro study. In this study, we investigated the expression level of ARHI in gastric cancer in order to investigate the function of ARHI and signaling pathways that might be linked during gastric cancer development., Methods: ARHI mRNA and protein expression levels were analyzed in primary gastric cancer tissues, adjacent noncancerous gastric tissues and gastric cancer cell lines using semi-quantitative polymerase chain reaction, western blotting and immunohistochemistry, respectively., Results: Our results showed that both mRNA and protein expression levels of the ARHI gene were significantly downregulated (P < 0.05) in gastric cancer tissues and cell lines compared to the corresponding normal control groups. The protein expression level of ARHI was not associated with age, gender, location of tumor, tumor size or metastasis in patients with gastric cancer. However, a significant correlation between the level of ARHI protein expression and the degree of tumor differentiation and Tumor-Node-Metastasis stage was observed (P < 0.05). Furthermore, results of the methyl thiazolyl tetrazolium and Transwell assays and flow cytometric analysis showed increased cell proliferation, migration and anti-apoptotic capacities in the well-differentiated gastric cancer MKN-28 cell line, which has stably silenced ARHI protein expression., Conclusion: Our data indicate that ARHI expression is downregulated in human gastric cancer and it may be a novel tumor suppressive target for gastric cancer therapy., (© 2012 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd.)

Because Mongolia has much higher liver disease burden than any other regions of the world, it is necessary to provide information on real-time situation of chronic liver disease in Mongolia. In this article, we reviewed studies performed in Mongolia from 2000 to 2011 on seroprevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) among healthy individuals and patients with chronic liver diseases, and on the practice patterns for the management of liver cirrhosis and hepatocellular carcinoma (HCC). According to previous reports, the seroprevalence of HBV and HCV in general population in Mongolia is very high (11.8% and 15% for HBV and HCV, respectively). Liver cirrhosis is also highly prevalent, and mortality from liver cirrhosis remained high for the past decade (about 30 deaths per 100,000 populations per year). Among patients with cirrhosis, 40% and 39% are positive for HBsAg and anti-HCV, respectively, and 20% are positive for both. The seroprevalence is similar for HCC and more than 90% of HCC patients are positive for either HBV or HCV. The incidence of HCC in Mongolia is currently among the highest in the world. The mortality from HCC is also very high (52.2 deaths per 100,000 persons per year in 2010). Partly due to the lack of established surveillance systems, most cases of HCC are diagnosed at an advanced stage. The mortality from liver cirrhosis and HCC in Mongolia may be reduced by implementation of antiviral therapy program and control of alcohol consumption.

Pokemon (POK erythroid myeloid ontogenic factor), which belongs to the POK protein family, is also called LRF, OCZF and FBI-1. As a transcriptional repressor, Pokemon assumes a critical function in cellular differentiation and oncogenesis. Our study identified an oncogenic role for Pokemon in human hepatocellular carcinoma (HCC). We successfully established human HepG2 and Huh-7 cell lines in which Pokemon was stably knocked down. We demonstrated that Pokemon silencing inhibited cell proliferation and migration. Pokemon knockdown inhibited the PI3K/Akt and c-Raf/MEK/ERK pathways and modulated the expression of various cell cycle regulators in HepG2 and Huh-7 cells. Therefore, Pokemon may also be involved in cell cycle progression in these cells. We confirmed that Pokemon silencing suppresses hepatocellular carcinoma growth in tumor xenograft mice. These results suggest that Pokemon promotes cell proliferation and migration in hepatocellular carcinoma and accelerates tumor development in an Akt- and ERK-signaling-dependent manner.

Background and Aims: The expression of the jumping translocation breakpoint (JTB) gene is upregulated in malignant liver tissues; however, JTB is associated with unbalanced translocations in many other types of cancer that suppress JTB expression. No comprehensive analysis on its function in human hepatocellular carcinoma (HCC) has been performed to date. We aimed to define the biological consequences for interaction between JTB and HBsAg in HCC cell lines., Methods: We employed the stable transfection to establish small HBsAg expressing HepG2 cell line, and stably silenced the JTB expression using short hairpin RNA in HepG2 cell line. The effects of JTB and small HBsAg in vitro were determined by assessing cell apoptosis and motility., Results: Silencing of JTB expression promoted cancer cell motility and reduced cell apoptosis, which was significantly enhanced by HBs expression. Expression of HBsAg inhibited the translocation of JTB to the mitochondria. Furthermore, silencing of the JTB resulted in an increase in the phosphorylation of p65 in HepG2 cells and HepG2-HBs cells, whereas HBsAg expression decreased the phosphorylation of p65. The silencing of JTB in HepG2-HBs cells conferred increased advantages in cell motility and anti-apoptosis., Conclusion: HBsAg inhibited the translocation of JTB to the mitochondria and decreased the phosphorylation of p65 through the interaction with JTB, After JTB knockdown, HBsAg exhibited a stronger potential to promote tumor progression. Our data suggested that JTB act as a tumor suppressor gene in regards to HBV infection and its activation might be applied as a therapeutic strategy for in control of HBV related HCC development.

Background: Double-stranded RNA-activated protein kinase (PKR), an interferon (IFN)-stimulated gene, is activated by binding with double-stranded RNA, a putative replicative intermediate of the hepatitis C virus (HCV). Activated PKR phosphorylates the alpha subunit of eukaryotic initiation factor-2 to inhibit the translation of viral protein., Aims/methods: We established stable PKR knockdown Huh7 cells using RNA interference and investigated the effect of PKR against HCV replication using a subgenomic replicon that expressed luciferase reporter protein and the JFH1 full-length HCV genome., Results: In stable PKR knockdown cells that harboured a subgenomic replicon, luciferase activity was approximately three times higher than that of control cells, indicating that the subgenomic replicon replicated with a higher efficiency in stable PKR knockdown cells than that in control cells. Furthermore, stable PKR knockdown cells secreted significantly more HCV particles than did control cells after transfection with the full-length HCV genome. The replication of the subgenomic replicon was suppressed by the addition of IFN-alpha in both cells. Although the extent of suppression was significantly lower in stable PKR knockdown than control cells using a low concentration (2.5-5 U/ml) of IFN-alpha, even 10 U/ml IFN-alpha suppressed the replication of subgenomic replicon by >98% in both cells., Conclusions: Double-stranded RNA-activated protein kinase plays an important role in suppressing HCV replication in an innate state, but may not be essential in IFN therapy.

Unlabelled: Infection by hepatitis C virus (HCV) usually results into chronic hepatitis that can ultimately lead to cirrhosis and hepatocellular carcinoma. Type 1 interferons (IFN-alpha/beta) constitute the primary cellular defense against viral infection including HCV. IFN binding to their receptors activates associated Jak1 and Tyk2 kinases, which ultimately leads to phosphorylation and assembly of a signal transducer and activator of transcription protein (STAT)1-STAT2-interferon regulatory factor (IRF)9 trimetric complex called interferon-stimulated gene factor 3 that translocates into the nucleus and binds to the interferon- stimulated response elements (ISRE), leading to transcriptional induction of several antiviral genes, including double-stranded RNA-activated protein kinase (PKR), 2',5'- oligoadenylate synthetase (OAS), and myxovirus resistance protein A (MxA). Understanding the mechanisms of how the virus evades this cellular innate defense and establishes a chronic infection is the key for the development of better therapeutics against HCV infection. Here, we demonstrate that p53 could have a crucial role in the cellular innate defense against HCV. We observed significantly higher levels of HCV RNA replication and viral protein expression in the Huh7 cells when their p53 expressions were knocked down. Moreover, IFN treatment was less effective in inhibiting the HCV RNA replication in the p53-knocked-down (p53kd) Huh7 cells. In fact, the activation of the ISRE and the induction of ISGs were significantly attenuated in the p53kd Huh7 cells and p53 was found to directly interact with IRF9., Conclusion: These observations underscore the potential contributions of the tumor suppressor p53 in cellular antiviral immunity against HCV with possible therapeutic implications.

Smad4 is a tumour suppressor gene frequently deleted in pancreatic cancer. To investigate the roles of Smad4 deficiency in invasive and matastatic capabilities of pancreatic cancer, we examined the effects of Smad4 deficiency on regulation of the invasion suppressor E-cadherin in pancreatic cancer cell line PANC-1. TGF-beta decreased expression of E-cadherin and beta-catenin proteins at the plasma membrane, increased Snail and Slug mRNA expression, and induced fibroblastoid morphology in PANC-1 cells. These effects of TGF-beta were abrogated in Smad4-knocked-down PANC-1 cells. We also found that TGF-beta-induced down-regulation of E-cadherin expression was partially inhibited in Snail- and Slug-knocked-down PANC-1 cells. Thus, Smad4 mediates down-regulation of E-cadherin induced by TGF-beta in PANC-1 cells, at least in part, through Snail and Slug induction. These results suggest that Smad4 deficiency observed in invasive and metastatic pancreatic cancer might not be linked to the loss of E-cadherin.

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. It is a highly aggressive malignancy for which currently available treatments are of only limited efficacy. For this reason, much research is directed at elucidating fundamental molecular mechanisms underlying the biology of pancreatic cancer. These efforts are generating a rapidly growing body of information. The yet unmet challenge is to translate this information into clinically applicable strategies for early detection, prediction of prognosis, and effective therapies for patients diagnosed with pancreatic cancer.

HMGA1 proteins are architectural transcription factors that are overexpressed in a range of human malignancies, including pancreatic adenocarcinoma. We hypothesized that HMGA1 expression is a determinant of cellular invasiveness and metastasis in pancreatic cancer. Stable silencing of HMGA1 in MiaPaCa2 and PANC1 pancreatic adenocarcinoma cells was achieved by transfection of short hairpin RNA-generating vectors. Additionally, stable overexpression of HMGA1 in MiaPaCa2 cells (characterized by low levels of inherent HMGA1 expression) was achieved. HMGA1 silencing resulted in significant reductions in cellular invasiveness through Matrigel; in cellular matrix metalloproteinase-9 (MMP-9) activity, mRNA levels, and gene promoter activity; and in Akt phosphorylation at Ser(473). Conversely, forced HMGA1 overexpression resulted in significant increases in cellular invasiveness; in cellular MMP-9 activity, mRNA levels, and promoter activity; and in Akt phosphorylation at Ser(473). HMGA1 overexpression-induced increases in invasiveness were MMP-9 dependent. The role of phosphatidylinositol-3 kinase (PI3K)/Akt in mediating HMGA1-dependent invasiveness was elucidated by a specific PI3K inhibitor (LY294002) and constitutively active and dominant-negative Akt adenoviral constructs. Akt-dependent modulation of MMP-9 activity contributed significantly to HMGA1 overexpression-induced increases in invasive capacity. Furthermore, HMGA1 silencing resulted in reductions in metastatic potential and tumor growth in vivo and in tumoral MMP-9 activity. Our findings suggest that HMGA1 may be a novel molecular determinant of invasiveness and metastasis, as well as a potential therapeutic target, in pancreatic adenocarcinoma.

Purpose: It is important to identify the definitive molecular switches involved in the malignant transformation of premalignant tissues. Cellular senescence is a specific characteristic of precancerous tissues, but not of cancers, which might reflect tumorigenesis-protecting mechanisms in premalignant lesions. Polycomb protein Bmi1, which is a potent negative regulator of the p16INK4 gene, suppresses senescence in primary cells and is overexpressed in various cancers. We hypothesized that Bmi1 expression would also be dysregulated in precancerous lesions in human digestive precancerous tissues., Experimental Design: Bmi1 expression was investigated in cancerous and precancerous tissues of the digestive tract. The expression of p16, beta-catenin, and Gli1 and the in vivo methylation status of the p16 gene were also analyzed in serial sections of colonic precancerous lesions., Results: Bmi1 was clearly overexpressed across a broad spectrum of gastrointestinal cancers, and the expression of Bmi1 increased in a manner that reflected the pathologic malignant features of precancerous colonic tissues (low-grade dysplasia, 12.9 +/- 2.0%; high-grade dysplasia, 82.9 +/- 1.6%; cancer, 87.5 +/- 2.4%). p16 was also strongly expressed in high-grade dysplasia, but not in cancers. p16 promoter methylation was detected only in some Bmi1-positive neoplastic cells., Conclusions: Bmi1 overexpression was correlated with the malignant grades of human digestive precancerous tissues, which suggests that advanced Bmi1 dysregulation might predict malignant progression. The abnormal Bmi1 expression might link to malignant transformation via the disturbance of orderly histone modification.

The graft-versus-tumor (GVT) effect that occurs following allogeneic bone marrow transplantation (BMT) and donor lymphocyte infusion (DLI) is currently being subjected to intensive investigation because of clinical evidence for GVT efficacy against leukemia. In this report, we investigate the efficacy and molecular mechanisms of GVT against solid tumors, using a modification of the mouse parent-to-F1 BMT model. Mouse Colon26 cells in which tumor necrosis factor related apoptosis-inducing ligand (TRAIL) receptor expression was stably knocked down were transplanted to investigate the role of the TRAIL-TRAIL receptor system in the GVT effect. In addition, Fas ligand-(FasL) deficient mice on a C57BL6 (B6) background were used as donors, to determine the significance of the Fas-FasL system for the antitumor effect. The group that received B6 DLI followed by preconditioning with 950 rad irradiation underwent tumor reduction associated with the induction of IFN-gamma, TRAIL and tumor-cell apoptosis. In vitro cultured Colon26 cells were resistant to TRAIL but susceptible to the combination of IFN-gamma and TRAIL in a TRAIL-dose-dependent manner. The infusion of lymphocytes from FasL-defective donors reduced the tumor progression, although efficacy was decreased in the TRAIL receptor knockdown tumors but not in wild-type ones, compared with infusion of B6-derived lymphocytes. The findings indicate that GVT activity against subcutaneous colon tumors is efficiently induced by preconditioning with irradiation and allogeneic DLI, and that TRAIL and IFN-gamma act cooperatively in the antitumor effect., (2005 Wiley-Liss, Inc.)

Background & Aims: Persistent infection with hepatitis C virus (HCV) leads to chronic hepatitis and hepatocellular carcinoma (HCC). RNA interference (RNAi) may act as a host antiviral response against viral RNA., Methods: The effects of RNAi on both the replicative intermediates and the internal ribosome entry site (IRES) of HCV were studied by using HCV-related short interfering RNA (siRNA) detection assay. The mechanism that permits HCV to escape RNAi was studied by using RNAi assay materials., Results: These studies demonstrate that the Dicer, an RNase enzyme that generates short siRNA, can target and digest both the IRES and the replicative intermediate of HCV into siRNA of approximately 22 nucleotides. Further studies also show that Dicer can inhibit the replication of the HCV subgenomic replicon. However, the HCV core protein inhibits this RNAi and rescues the replication of the HCV subgenomic replicon through a direct interaction with Dicer., Conclusions: RNAi is a limiting factor for HCV infection, and the core protein suppresses the RNA silencing-based antiviral response. This ability of the core protein to counteract the host defense may lead to a persistent viral infection and may contribute to the pathogenesis of HCV.

The activation of Hedgehog (Hh) signaling has been implicated in the growth of various tumor types, including gastric carcinoma. However, the precise mechanisms of Hh activation and suppression of tumor growth by the blockade of Hh signaling in gastric carcinoma cells remain unknown. The aim of this study was to elucidate the mechanism of abnormal Hh signaling and the key molecules contributing to dysregulated growth of gastric carcinoma. The Sonic hedgehog (Shh) ligand and its receptor Patched were expressed in all five gastric carcinoma cell lines examined (MKN1, MKN7, MKN45, MKN74, and AGS cells). The blockade of Hh signaling with anti-Shh antibody inhibited the growth of all five gastric carcinoma cell lines. Shh was overexpressed (mean, 12.8-fold) in 8 of 14 (57.0%) cancerous tissue samples from patients with gastric carcinoma as compared with expression in the surrounding noncancerous tissues. The disruption of glioma-associated oncogene 1 (Gli1) by small interfering RNA induced an increase in p21/cyclin-dependent kinase-interacting protein 1 (CIP1), interfered with the G1-S transition, and suppressed cell proliferation. The stimulation or inhibition of Hh signaling did not affect p53 activity and the induction of p21/CIP1 expression and the G1 arrest by inhibition of Hh signaling were not affected by the p53 status. These findings suggest that the overexpression of Shh contributes to constitutive Hh activation and that this signaling pathway negatively regulates p21/CIP1 through a Gli1-dependent and p53-independent mechanism in gastric carcinoma cells.

Aim: Vascular endothelial growth factor (VEGF) is a potent mediator of peritoneal fluid accumulation following tumor progression. This study investigated the role of VEGF secreted by cancerous cells in the formation of malignant ascites., Methods: VEGF expression was eliminated by knockdown in the pancreas cancer cell-line PancO2 using vector-based short-hairpin type RNA interference (RNAi). Malignant ascites formation in the mouse was analyzed by intraperitoneal injection of PancO2 cells expressing VEGF or with expression knockdown., Results: The VEGF knockdown PancO2 cell was successfully established. Knockdown of VEGF did not affect cancer cell proliferation in vitro or in vivo. The volume of ascites following peritoneal expansion of the tumor in VEGF knockdown cells and control cells did not differ statistically in this in vivo study. Moreover, the VEGF concentration in the ascites did not differ statistically., Conclusion: Malignant ascites formation might be mediated by VEGF production in noncancerous tissues, such as stromal compartments. An anti-VEGF strategy against malignant ascites could be applied to various tumors regardless of whether they secrete VEGF.

Although RNA interference (RNAi) is a popular technique, no method for simultaneous silencing of multiple targets by small-hairpin RNA (shRNA)-expressing RNAi vectors has yet been established. Although gene silencing can be achieved by synthetic small-interfering RNA (siRNA) duplexes, the approach is transient and largely dependent on the transfection efficiency of the host cell. We offer a solution: a simple, restriction enzyme-generated stable RNAi technique that can efficiently silence multiple targets with a single RNAi vector and a single selection marker. In this study, we succeeded in simultaneous stable knockdown of transforming growth factor beta (TGF-beta) pathway-related Smads--Smad2, Smad3 and Smad4--at the cellular level. We observed distinct phenotypic changes in TGF-beta-dependent cellular functions such as invasion, wound healing and apoptosis. This method is best suited for an analysis of complex signal transduction pathways in which silencing of a single gene cannot account for the whole process.

The interaction between the chemokine receptor CXCR4 and its specific ligand, stromal cell-derived factor-1 (SDF-1/CXCL12), mediates several cellular functions. In cancer, SDF-1-positive or CXCR4-positive cells of various lineages are detected within tumor tissues. Recent intensive research has indicated the possibility that blocking CXCR4 could reduce the metastatic potential of cancer cells. Here, we show that the inhibition of the SDF-1/CXCR4 axis decreases the growth of s.c. gastrointestinal tumors through the suppression of tumor neoangiogenesis. The neutralization of CXCR4 suppressed the growth in vivo of tumors derived from mouse Colon38 and PancO2 cells, whereas it did not affect the growth of Colon38 and PancO2 cells in vitro. This attenuation of tumor growth was found to be independent of the expression of CXCR4 by the cancer cells themselves, because CXCR4 knocked-down Colon38 cells grew similarly to control cells. Furthermore, CD31-positive tumor capillaries were reduced to 45% (P < 0.001) and intratumor blood flows were decreased to 65% (P < 0.01) by blockade of CXCR4. The vascular endothelial growth factor (VEGF) concentration in the tumors was not affected by the neutralization of CXCR4. Taken together with the detection of CXCR4-positive endothelial cells in the tumor tissues, the findings suggest that the antiangiogenic effects of the blockade of CXCR4 are related to a reduction of the establishment of tumor endothelium independently of VEGF inhibition. Our data indicate that the SDF-1/CXCR4 pathway might be a general target for anticancer strategies and that blocking this system could be cooperatively effective in combination with other antiangiogenic therapies, such as blockade of VEGF.

Mutations in the PIK3CA gene, which encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K), have been reported in human cancers, including colorectal cancer. Most of the mutations cluster at hotspots within the helical and kinase domains. Whereas H1047R, one of the hotspot mutants, is reported to have elevated lipid kinase activity, the functional consequences of other mutations have not been examined. In this study, we examined the effects of colon cancer-associated PIK3CA mutations on the lipid kinase activity in vitro, activation of the downstream targets Akt and p70S6K in vivo and NIH 3T3-transforming ability. Of eight mutations examined, all showed increased lipid kinase activity compared with wild-type p110alpha. All the mutants strongly activated Akt and p70S6K compared with wild-type p110alpha as determined by immunoblotting using phospho-specific antibodies. These mutants also induced morphologic changes, loss of contact inhibition, and anchorage-independent growth of NIH 3T3 cells. The hotspot mutations examined in this study, E542K, E545K, and H1047R, all had high enzymatic and transforming activities. These results show that almost all the colon cancer-associated PIK3CA mutations are functionally active so that they are likely to be involved in carcinogenesis.

Mutations in the B-raf gene have been reported in a number of human cancers, including melanoma and lung cancer. More than 80% of the reported B-raf mutations were V599E; however, non-V599E mutations have been frequently found in non-small cell lung cancers as compared with melanoma. Some non-V599E mutations have been found surrounding Thr439, which is thought likely to be one of the three Akt phosphorylation sites in the B-raf protein. However, as a previous report indicated that Thr439 was not phosphorylated by Akt, the functional consequences of these mutations have been unclear. Here, we examined the effects of cancer-related B-raf mutations surrounding Thr439 on the activation of the mitogen-activated protein/ extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase (Erk) pathway and the transformation of NIH 3T3 fibroblasts. Among the three reported mutations (K438Q, K438T, and T439P) found in non-small cell lung carcinoma and melanoma, none elevated the activity of the MEK/Erk cascade as determined by in vitro kinase assays, immunoblots using antibody specific for phosphorylated Erk, or Elk1-dependent reporter assays. The inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt signaling by LY294002 increased the Erk activation induced by the mutant B-raf proteins, as well as by wild-type B-raf. Furthermore, the B-raf mutants did not have increased NIH 3T3-transforming activities, as determined by colony-formation assays. These results suggest that the B-raf mutations surrounding Thr439 found in human cancers are unlikely to contribute to increased oncogenic properties of B-raf., (Copyright 2005 Wiley-Liss, Inc.)

The transforming growth factor-beta (TGF-beta)-Smad signaling pathway inhibits the growth of human epithelial cells and plays a role in tumor suppression. The Smad4 gene is mutated or deleted in 50% of pancreatic cancers. In this study, we succeeded in establishing Smad4 knockdown (S4KD) pancreatic cancer cell lines using the stable RNA interference (RNAi) method. Smad4 protein expression was reduced dramatically and TGF-beta-Smad signaling was markedly inhibited in the S4KD cell lines. The S4KD and control cells were stimulated with TGF-beta and analysed using a cDNA microarray that contained 3756 genes, in order to screen for target molecules downstream of TGF-beta. The microarray analysis revealed that 187 S4KD genes and 155 genes in the control cells were regulated immediately upon TGF-beta stimulation. Quantitative RT-PCR analysis on several of these genes produced results that corroborated the outcome of the microarray analysis. Most of the genes in the S4KD and control cells identified by the array differed, which suggests signaling pathways that differ according to Smad4 status. Of the identified genes, 246 have not been reported previously as genes that lie downstream of TGF-beta. Genes that are involved in cell proliferation, adhesion, and motility were found to be regulated differentially with respect to S4KD and control cells. Cell migration induced by TGF-beta was inhibited in the S4KD cells, which might be associated with a different regulation of integrin beta7. The knock down of a specific gene using stable RNAi appears to be a promising tool for analysing endogenous gene function.