PTEN encoding product: A marker for tumorigenesis and progression of gastric carcinoma

PTEN Expression Was Significantly Associated with PD-L1 Score but Not with EBV Infection in Gastric Cancer

Purpose

Gastric cancer (GC) remains a prevalent aggressive tumor with high morbidity and mortality globally. The identification of GC subtypes based on molecular features improved the prediction of prognosis and the selection of targeted therapies. PTEN is a characteristic tumor suppressor, while its association with different GC subtypes was unknown.

Patients and Methods

The cohort consisted of 248 patients diagnosed with gastric cancer who were hospitalized and received radical gastrectomy. In addition, PTEN gene expression matrix of STAD was retrieved from TCGA. The mRNA and protein levels of PTEN and PD-L1 were detected using qRT-PCR and IHC staining. Multivariate logistic regression and Kaplan–Meier analysis were used to examine the relationship between PTEN expression and clinical characteristics.

Results

In our study, PTEN was downregulated in gastric tumors both in mRNA and protein levels. Its inactivation was closely linked to higher histological grade (P = 0.005), neural invasion (P = 0.012), depth of invasion (P = 0.021), lymph metastasis (P = 0.026), and TNM stage (P = 0.001) of GC in the present study. Moreover, according to the molecular subtypes, high PTEN expression was related to high TPS score of PD-L1 positively (P = 0.010) but was not associated with MSI and EBV infection. Further, TCGA data validated that PTEN was indeed correlated with histological grade and invasion depth and positively related to PD-L1 expression (R = 0.29, adjusted P < 0.001).

Conclusion

The above results suggested that PTEN expression was a useful marker in gastric carcinogenesis and progression and in the selection of immunotherapy-based treatments for GC patients.

Secretome analysis reveals reduced expression of COL4A2 in hypoxic cancer-associated fibroblasts with a tumor-promoting function in gastric cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) are major components of the tumor microenvironment (TME). Hypoxic TME is known to promote tumor progression. However, how a hypoxic condition regulates CAFs remains elusive.

METHODS

To investigate the underlying mechanism involved in the regulation of gastric cancer (GC) progression by hypoxic CAFs, we performed secretome profiling. Normoxic or hypoxic CAFs conditioned media (CM) were filter-concentrated and in-gel trypsin digested. Resulting peptides were analyzed with LC-MS/MS.

RESULTS

We observed that CM derived from hypoxic CAFs could promote migration of a panel of GC cell lines (AGS, SNU668, SNU638). Mass spectrometry analysis of hypoxic or normoxic CAFs CM identified 1595 proteins, of which 19 proteins (10 upregulated and 9 downregulated) were differentially expressed in the hypoxic secretome. We focused on COL4A2, whose expression was significantly decreased in hypoxic CAFs in HIF-1α-independent manner. Silencing of COL4A2 expression in normoxic CAFs phenocopied the effect of hypoxic CAFs in promoting GC cell migration.

CONCLUSIONS

The reduced expression of COL4A2 in a hypoxic environment might be associated with the tumor-promoting role of hypoxic CAFs in GC.

ptk2 and mt2a Genes Expression in Gastritis and Gastric Cancer Patients with Helicobacter pylori Infection

BACKGROUND

ptk2 and mt2a genes contribute to the cell cycle during proliferation and apoptosis, respectively. Designing a case-control study including gastric adenocarcinoma and gastritis patients with and without Helicobacter pylori infection would lead to determinate of the correlations between ptk2 and mt2a genes expression with H. pylori infection in gastric antral epithelial cells.

METHODS

Overall, 50 and 30 gastric antral biopsy samples of gastric cancer (case group) and gastritis (control group) patients were included into study, respectively. All biopsy samples were collected considering the exclusion criteria including patients with a history of consumption of tobacco, alcohol, and anti-H. pylori drugs. Each patient group is divided into with and without H. pylori infection to detect cDNA fold changes of ptk2 and mt2a genes by using Real Time RT PCR. Furthermore, the presence of H. pylori virulence genes was detected directly by using specific primers and simple PCR on cDNA synthesized from total RNA of gastric antral biopsy samples.

RESULTS

A negative correlation was revealed between age and clinical manifestations with the ΔCt value of the ptk2 gene (P < 0.05). The H. pylori iceA1/2 and cagE genes revealed positive and negative correlations with the ΔCt value of the ptk2 gene (P < 0.05), respectively. Furthermore, a weak correlation was detectable between H. pylori babA2/B, oipA, and cagY genes and the ΔCt value of the mt2a gene in gastric antral epithelial cells of patients (P < 0.1).

CONCLUSIONS

The results of the current study opened a view for more investigation on the stunning roles of H. pylori infection in clinical outcomes through mt2a and ptk2 gene expression in gastric antral epithelial cells.

The HIF-1α as a Potent Inducer of the Hallmarks in Gastric Cancer

Hypoxia is the principal architect of the topographic heterogeneity in tumors. Hypoxia-inducible factor-1α (HIF-1α) reinforces all hallmarks of cancer and donates cancer cells with more aggressive characteristics at hypoxic niches. HIF-1α potently induces sustained growth factor signaling, angiogenesis, epithelial-mesenchymal transition, and replicative immortality. Hypoxia leads to the selection of cancer cells that evade growth suppressors or apoptotic triggers and deregulates cellular energetics. HIF-1α is also associated with genetic instability, tumor-promoting inflammation, and escape from immunity. Therefore, HIF-1α may be an important therapeutic target in cancer. Despite that, the drug market lacks safe and efficacious anti-HIF-1α molecules, raising the quest for fully unveiling the complex interactome of HIF-1α in cancer to discover more effective strategies. The knowledge gap is even wider in gastric cancer, where the number of studies on hypoxia is relatively low compared to other well-dissected cancers. A comprehensive review of the molecular mechanisms by which HIF-1α induces gastric cancer hallmarks could provide a broad perspective to the investigators and reveal missing links to explore in future studies. Thus, here we review the impact of HIF-1α on the cancer hallmarks with a specific focus on gastric cancer.

Role and mechanism of autophagy-regulating factors in tumorigenesis and drug resistance

A hallmark feature of tumorigenesis is uncontrolled cell division. Autophagy is regulated by more than 30 genes and it is one of several mechanisms by which cells maintain homeostasis. Autophagy promotes cancer progression and drug resistance. Several genes play important roles in autophagy-induced tumorigenesis and drug resistance including Beclin-1, MIF, HMGB1, p53, PTEN, p62, RAC3, SRC3, NF-2, MEG3, LAPTM4B, mTOR, BRAF and c-MYC. These genes alter cell growth, cellular microenvironment and cell division. Mechanisms involved in tumorigenesis and drug resistance include microdeletions, genetic mutations, loss of heterozygosity, hypermethylation, microsatellite instability and translational modifications at a molecular level. Disrupted or altered autophagy has been reported in hematological malignancies like lymphoma, leukemia and myeloma as well as multiple solid organ tumors like colorectal, hepatocellular, gall bladder, pancreatic, gastric and cholangiocarcinoma among many other malignancies. In addition, defects in autophagy also play a role in drug resistance in cancers like osteosarcoma, ovarian and lung carcinomas following treatment with drugs such as doxorubicin, paclitaxel, cisplatin, gemcitabine and etoposide. Therapeutic approaches that modulate autophagy are a novel future direction for cancer drug development that may help to prevent issues with disease progression and overcome drug resistance.

The PI3K/Akt/mTOR signaling pathway in gastric cancer; from oncogenic variations to the possibilities for pharmacologic interventions

Genetic and epigenetic alterations have been under concentrated investigations for many years in order to unearth the molecules regulating human cancer pathogenesis. However, the identification of a wide range of dysregulated genes and their protein products has raised a question regarding how the results of this large collection of alterations could converge into a formation of one malignancy. The answer may be found in the signaling cascades that regulate the survival and metabolism of the cells. Aberrancies of each participant molecule of such cascades may well result in augmented viability and unlimited proliferation of cancer cells. Among various signaling pathways, the phosphatidylinositol-3-kinase (PI3K) axis has been shown to be activated in about one-third of human cancers. One of the malignancies that is mostly affected by this axis is gastric cancer (GC), one of the most fatal cancers worldwide. In the present review, we aimed to illustrate the significance of the PI3K/Akt/mTOR axis in the pathogenesis of GC and also provided a wide perspective about the application of the inhibitors of this axis in the therapeutic strategies of this malignancy.

Targeting the histone demethylase PHF8-mediated PKCα-Src-PTEN axis in HER2-negative gastric cancer

Targeted treatments for advanced gastric cancer (GC) are needed, particularly for HER2-negative GC, which represents the majority of cases (80 to 88%). In this study, in silico analyses of the lysine histone demethylases (KDMs) involved in diverse biological processes and diseases revealed that PHD finger protein 8 (PHF8, KDM7B) was significantly associated with poor clinical outcome in HER2-negative GC. The depletion of PHF8 significantly reduced cancer progression in GC cells and in mouse xenografts. PHF8 regulated genes involved in cell migration/motility based on a microarray analysis. Of note, PHF8 interacted with c-Jun on the promoter of PRKCA which encodes PKCα. The depletion of PHF8 or PKCα greatly up-regulated PTEN expression, which could be rescued by ectopic expression of a PKCα expression vector or an active Src. These suggest that PTEN destabilization occurs mainly via the PKCα-Src axis. GC cells treated with midostaurin or bosutinib significantly suppressed migration in vitro and in zebrafish models. Immunohistochemical analyses of PHF8, PKCα, and PTEN showed a positive correlation between PHF8 and PKCα but negative correlations between PHF8 and PTEN and between PKCα and PTEN. Moreover, high PHF8-PKCα expression was significantly correlated with worse prognosis. Together, our results suggest that the PKCα-Src-PTEN pathway regulated by PHF8/c-Jun is a potential prognostic/therapeutic target in HER2-negative advanced GC.

PTEN Protein Loss and Loss-of-Function Mutations in Gastric Cancers: The Relationship with Microsatellite Instability, EBV, HER2, and PD-L1 Expression

Inactivation of phosphatase and tensin homolog (PTEN) is caused by multiple mechanisms, and loss of PTEN activity is related to the progression of various cancers. In gastric cancer (GC), the relationship between the loss of PTEN protein expression and various genetic alterations remains unclear. The effects of microsatellite instability (MSI), Epstein–Barr virus (EBV), HER2 overexpression, and PD-L1 expression on PTEN mutation have not been fully explored. We performed comprehensive cancer panel tests with a cohort of 322 tumor samples from patients with advanced GC. Immunohistochemistry for PTEN protein was performed in all cases, and the loss of protein expression was defined as a complete absence of nuclear staining. In total, 34 cases (10.6%) had pathogenic PTEN mutations, of which 19 (55.9%) showed PTEN protein loss. The most common PTEN variants associated with protein loss were p.R130 (n = 4) followed by p.R335, p.L265fs, and deletions (n = 2). All the ten nonsense mutations identified in the samples resulted in PTEN inactivation. In the remaining 288 GC cases with wild-type PTEN, protein loss was found in 35 cases (12.2%). Thus, PTEN mutations were significantly associated with PTEN protein loss (p = 5.232 × 10⁻¹⁰), high MSI (p = 3.936 × 10⁻⁸), and EBV-positivity (p = 0.0071). In conclusion, our results demonstrate that loss-of-function mutations in PTEN are a frequent genetic mechanism of PTEN inactivation in GC.

Variance-Preserving Estimation of Intensity Values Obtained From Omics Experiments

Faced with the lack of reliability and reproducibility in omics studies, more careful and robust methods are needed to overcome the existing challenges in the multi-omics analysis. In conventional omics data analysis, signal intensity values (denoted by M and values) are estimated neglecting pixel-level uncertainties, which may reflect noise and systematic artifacts. For example, intensity values from two-color microarray data are estimated by taking the mean or median of the pixel intensities within the spot and then subjected to a within-slide normalization by LOWESS. Thus, focusing on estimation and normalization of gene expression profiles, we propose a spot quantification method that takes into account pixel-level variability. Also, to preserve relevant variation that may be removed in LOWESS normalization with poorly chosen parameters, we propose a parameter selection method that is parsimonious and considers intrinsic characteristics of microarray data, such as heteroskedasticity. The usefulness of the proposed methods is illustrated by an application to real intestinal metaplasia data. Compared with the conventional approaches, the analysis is more robust and conservative, identifying fewer but more reliable differentially expressed genes. Also, the variability preservation allowed the identification of new differentially expressed genes. Using the proposed approach, we have identified differentially expressed genes involved in pathways in cancer and confirmed some molecular markers already reported in the literature.

Bridging genomics and phenomics of gastric carcinoma

Genetic alterations are the starting point leading to numerous changes in clinical and pathologic features (phenotypes) of individual cancers; however, their inter-relationships in gastric cancers (GC) are unclear. We performed massive parallel sequencing of 381 cancer-related genes and compared the results with clinical and pathologic findings in 330 GC. High tumor mutation burden (TMB) accounted for 11% of GC (n = 37) and all 19 MSI-H GCs were high TMB. High TMB was significantly more frequent in intestinal-type by Lauren, tumor with higher host cellular immune response, earlier AJCC stage and favorable prognosis. The most significantly mutated genes were TP53 (54%), ARID1A (23%), CDH1 (22%), PIK3CA (12%), RNF43 (10%) and KRAS (9%). For receptor tyrosine kinases, amplifications detected by immunohistochemistry were higher than sequencing (HER2, 9.1% vs. 5.8%; EGFR, 11.2% vs. 6.1%; FGFR2, 4.6% vs. 3.9%, c-MET, 3.4% vs. 0.9%). PTEN protein loss (22%) correlated well with underlying PTEN alterations while ATM loss (27%) was not significantly correlated with genetic alterations of ATM. p53 protein expression predicted alterations of TP53 with high sensitivity (97.8%) and low (15.9%) specificity. The poorly cohesive histology/CDH1-mutant GC subgroup showed the worst survival (p < 0.001). PD-L1 expression was significantly associated with MSI-H, MLH1 loss, ATM loss, MET positivity, higher host immune response, and genetic alterations of ARID1A, BRD3, PIK3CA, KRAS, MAP3K13, CDH2, PTEN and ESR1. The merged clinical, pathology and genomics of GC provide a better understanding of GC and new insights into the treatment of GC.

Expression of VEGF with tumor incidence, metastasis and prognosis in human gastric carcinoma

OBJECTIVE

To analysis the expression of VEGF in gastric carcinoma cell and tumor tissue, our study determined the relationship between the expression of VEGF and tumor incidence, metastasis and prognosis in human gastric carcinoma.

METHODS

Treatment of ZD6474 at dose of 30 μmol/L was performed in gastric carcinoma cell BGC823. qPCR and Western-blot were used to analysis the mRNA and protein expression of VEGF. MTT, wound healing and Transwell experiments were conducted to study the effect of VEGF on tumor incidence, metastasis and prognosis. Sixty patients with gastric cancer were selected as the gastric cancer group, and 30 patients with gastric ulcer receiving main gastric resection were selected as control group. The survival curve of patients with gastric cancer in five years was recorded. The correlation between expression of VEGF to incidence, metastasis and prognosis of gastric cancer was evaluated by Cox multifactor regression.

RESULTS

The mRNA and protein expression of VEGF in treatment group were significantly lower than that of control group (P< 0.01). The results of MTT, wound healing and Transwell experiments were showed that the cell proliferation, migration and invasion capacity in treatment group were significantly reduced compared to that of the control group (P< 0.01). The 5-year survival rate for patients with VEGF positive expression was significantly decreased compared to the patients with VEGF expression negative (P< 0.01). The tumor size, differentiation, lymph node metastasis and tumor stage were statistically related to VEGF level (P< 0.05). The results of Cox regression multifactor analysis showed that lymph node metastasis, tumor staging and the expression of VEGF were significantly associated to the prognosis of gastric cancer patients (P< 0.05).

CONCLUSION

Our data demonstrated that the expression of VEGF was significantly related to the tumor incidence, metastasis and prognosis of patients with gastric cancer, which provides new leads to the diagnosis of gastric cancer.

The Smad4/PTEN Expression Pattern Predicts Clinical Outcomes in Colorectal Adenocarcinoma

Background

Smad4 and PTEN are prognostic indicators for various tumor types. Smad4 regulates tumor suppression, whereas PTEN inhibits cell proliferation. We analyzed and compared the performance of Smad4 and PTEN for predicting the prognosis of patients with colorectal adenocarcinoma.

Methods

Combined expression patterns based on Smad4+/– and PTEN+/– status were evaluated by immunostaining using a tissue microarray of colorectal adenocarcinoma. The relationships between the protein expression and clinicopathological variables were analyzed.

Results

Smad4–/PTEN– status was most frequently observed in metastatic adenocarcinoma, followed by primary adenocarcinoma and tubular adenoma (p<.001). When Smad4–/PTEN– and Smad4+/PTEN+ groups were compared, Smad4–/PTEN– status was associated with high N stage (p=.018) and defective mismatch repair proteins (p=.006). Significant differences in diseasefree survival and overall survival were observed among the three groups (Smad4+/PTEN+, Smad4–/PTEN+ or Smad4+/PTEN–, and Smad4–/PTEN–) (all p<.05).

Conclusions

Concurrent loss of Smad4 and PTEN may lead to more aggressive disease and poor prognosis in patients with colorectal adenocarcinoma compared to the loss of Smad4 or PTEN alone.

Prognostic implications of phosphatidylinositol 3-kinase/AKT signaling pathway activation in gastric carcinomas

INTRODUCTION

Activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway plays a critical role in carcinogenesis and resistance to anticancer drugs. In this study, gastric carcinomas (GC) were investigated and statistical analyses were performed concerning the correlation between the clinicopathological features and activation of the PI3K/AKT pathway.

MATERIAL AND METHODS

Immunohistochemistry for p-AKT, p-mTOR and PTEN was performed in 239 GC and 200 non-neoplastic gastric tissues. The clinicopathological parameters were recorded from the medical charts. Statistical significance was defined by a p-value < 0.05.

RESULTS

High p-AKT expression was observed in 10% of the normal gastric tissue and in 90% of GC, and it was significantly associated with tumor size (p < 0.001), T3/T4 tumors (p < 0.001), and presence of metastases (p = 0.02). Similarly, p-mTOR positivity was found in GC cells, but not in the normal gastric mucosa, and was correlated with perineural invasion (p = 0.02) and T3/T4 tumors (p = 0.03). On the other hand, PTEN expression was weak and focal in the tumor cells, while in the normal gastric tissue this staining was strong and diffuse. Importantly, the expression of p-mTOR and PTEN was associated with overall survival.

CONCLUSIONS

The results of the present study, characterized by the loss of PTEN expression and higher expression of p-AKT and p-mTOR in the majority of tumor cells, apparently are implicated in the carcinogenesis and progression of GC. The identification of p-mTOR and PTEN expression as prognostic factors corroborates the identification and use of potential target drugs that could be more efficient for the treatment of these patients.

MiR-26a performs converse roles in proliferation and metastasis of different gastric cancer cells via regulating of PTEN expression

Gastric cancer is the second leading cause of cancer-related death in the world. The exact molecular pathways in gastric cancer need for further study. We herein indicated miR-26a performed converse roles on oncogenicity in different gastric cancer cells. In gastric cancer cells MKN-28, miR-26a promoted cell proliferation, migration and invasion. However, in gastric cancer cells AGS, miR-26a reduced cell proliferation and metastasis. PTEN was identified as a direct target of miR-26a. In MKN-28 cells, PTEN was suppressed by miR-26a through 3'-UTR, and PTEN mediated miR-26a promoting oncogenicity including cell proliferation and metastasis. On the other hand, in AGS cells, the expression of PTEN was enhanced by miR-26a, and PTEN mediated miR-26a reducing oncogenicity. The mechanism in AGS cells may be the indirect regulation of PTEN by miR-26a overcame the direct targeting regulation. The model like MKN-28 cells was concordant with patients with a high level of miR-26a and a low level of PTEN and patients with a low level of miR-26a and a high level of PTEN which showed lower overall survival (OS); the model like AGS cells was concordant with patients with both high level of miR-26a and PTEN and both low level of miR-26a and PTEN which showed higher OS. These findings will facilitate a better understanding of the functions and mechanisms about miR-26a, miR-26a and PTEN are potential combined biomarkers in patients with gastric cancer.

MicroRNA-214 promotes peritoneal metastasis through regulating PTEN negatively in gastric cancer

BACKGROUND AND OBJECTIVE

We aimed to investigate the effects of microRNA-214 (miR-214) on peritoneal metastasis as well as to elucidate its regulatory mechanism in gastric cancer (GC).

METHODS

The expression levels of miR-214 in human GC cell lines MKN-28NM, MKN-28M, GC9811 and GC9811-P were analyzed by quantitative real-time PCR. Lentiviral miR-214, lentiviral miR-214 inhibitor, and empty lentiviral vector were transfected to GC cell lines, respectively. The roles of miR-214 in cell invasion, migration, proliferation and colony-forming ability were then analyzed. Besides, the expression levels of PTEN in different transfected cells were determined by western blot analysis.

RESULTS

We found that miR-214 was up-regulated in GC9811-P cells with high metastatic potential to the peritoneum compared with that in GC9811 cells. In addition, in vitro overexpression of miR-214 promoted cell invasion, migration, proliferation and colony-forming ability of GC9811 cells, while down-regulation of miR-214 had opposite effects in GC9811-P cells. Besides, overexpression of miR-214 in GC9811 cells markedly down-regulated PTEN expression, whereas down-regulation of miR-214 in GC9811-P cells significantly increased PTEN expression.

CONCLUSIONS

Our findings indicate that miR-214 may promote peritoneal metastasis of GC cells via down-regulation of PTEN, thus leading to the progression of GC.

Upregulation of PTEN suppresses invasion in Tca8113 tongue cancer cells through repression of epithelial-mesenchymal transition (EMT)

We previously discovered that the expression of the tumor suppressor phosphatase and tensin homolog (PTEN) was downregulated in the majority patients with tongue squamous cell carcinoma (TSCC). The aim of this study was to investigate the role of PTEN overexpression in the regulation of epithelial-mesenchymal transition (EMT) of the tongue squamous carcinoma cell line Tca8113 as well as explore the underlying mechanism. GV230 (containing the PTEN gene) and empty vectors were transfected into Tca8113 cells. After stable transfection, the messenger RNA (mRNA) and protein levels of PTEN were validated using quantitative real-time PCR (qPCR) and Western blot analysis. The growth and cell cycle were analyzed using Cell Counting Kit-8 (CCK-8) and flow cytometry, respectively. The invasion ability was measured with a transwell assay. The effects of PTEN overexpression on EMT and Hedgehog signaling were assessed by comparing Tca8113-PTEN cells with control and negative control cell groups. We found that PTEN expression was significantly upregulated after transfection. Meanwhile, upregulated PTEN inhibited the proliferation and invasion of Tca8113 cells. In addition, we observed changes in the EMT- and Hedgehog-associated proteins. These data demonstrated that PTEN upregulation could reduce invasion by inhibiting the process of EMT in Tca8113 cells, which might be related to the Hedgehog signaling pathway.

Icariin regulates the proliferation and apoptosis of human ovarian cancer cells through microRNA-21 by targeting PTEN, RECK and Bcl-2

Icariin is the main active ingredient found in the traditional Chinese medicinal plant Epimedium, and exhibits various pharmacological effects such as enhanced immune function, anticancer activity, improved cardiovascular function and endocrine adjustment. However, the effect of icariin on ovarian cancer and the related mechanism have never been investigated. In the present study, we aimed to verify whether icariin inhibits the proliferation and increases the apoptosis of human ovarian cancer cells, and its molecular mechanism in order to establish an association and identify potential therapeutic targets. In the present study, ovarian cancer A2780 cells were treated with various concentrations of icariin, and the cell viability was evaluated by 3,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry and caspase-3 colorimetric assay were performed to observe apoptotic changes in the A2780 cells. qPCR analysis was used to analyze miR-21 expression in the A2780 cells. Western blot analysis was used to assess PTEN, RECK and Bcl-2 protein expression. Transfection of microRNA-21 (miR-21) and anti-miR-21 was used to investigate expression of its target genes associated with cell proliferation and apoptosis. Icariin concomitantly suppressed cell proliferation, accelerated apoptosis and increased caspase-3 activity in the A2780 cells. In the ovarian cancer A2780 cells, icariin substantially decreased the miR-21 expression level, increased PTEN and RECK protein expression levels and decreased the Bcl-2 protein expression level. Notably, miR-21 regulated the potential anticancer effects of icariin on cell proliferation and apoptosis by targeting PTEN, RECK and Bcl-2 in the ovarian cancer A2780 cells. Our results demonstrated that icariin is an excellent candidate antitumor agent which exhibits an anticancer curative effect on ovarian cancer cells. miR-21 and its target genes may play a vital role in the molecular mechanism of the anticancer effects of icariin.

Chemoresistance is associated with Beclin-1 and PTEN expression in epithelial ovarian cancers

The aim of the present study was to investigate the protein expression of the autophagy-related genes, BECN1 and PTEN, and the association with drug resistance in epithelial ovarian cancers. In total, 40 patients with pathologically diagnosed epithelial ovarian cancer were divided into a chemotherapy-sensitive group (n=20) and a chemotherapy-resistant group (n=20), according to the results of the pre- or post-operative normative chemotherapy and the post-operative follow-up. The protein expression of the phosphatase and tensin homolog (PTEN) and the BECN1 gene product, Beclin-1, was analyzed using immunohistochemistry in the 40 patients with ovarian carcinoma. The positive rate of Beclin-1 expression was significantly lower in the resistant group (35.0%) compared with the sensitive group (50.0%). The positive rate of PTEN expression was also significantly lower in the resistant group (30.0%) compared with the sensitive group (65.0%). Furthermore, the differences in the expression rates were revealed to be significant (P<0.05). The expression of Beclin-1 was identified to be positively correlated with the expression of PTEN (rs=0.816; P<0.0001). The low expression of the Beclin-1 and PTEN proteins in the ovarian cancer tissues was revealed to be closely associated with drug resistance. Therefore, Beclin-1 may interact with PTEN to participate in the mechanism of drug resistance and the changes in macrophage activity observed in cases of drug-resistant ovarian cancer.

Roles of PTEN (Phosphatase and Tensin Homolog) in gastric cancer development and progression

Gastric cancer is highly invasive, aggressively malignant, and amongst the most prevalent of all forms of cancer. Despite improved management strategies, early stage diagnosis of gastric cancer and accurate prognostic assessment is still lacking. Several recent reports have indicated that the pathogenesis of gastric cancer involves complex molecular mechanisms and multiple genetic and epigenetic alterations in oncogenes and tumor suppressor genes. Functional inactivation of the tumor suppressor protein PTEN (Phosphatase and Tensin Homolog) has been detected in multiple cases of gastric cancer, and already shown to be closely linked to the development, progression and prognosis of the disease. Inactivation of PTEN can be attributed to gene mutation, loss of heterozygosity, promoter hypermethylation, microRNA- mediated regulation of gene expression, and post-translational phosphorylation. PTEN is also involved in mechanisms regulating tumor resistance to chemotherapy. This review provides a comprehensive analysis of PTEN and its roles in gastric cancer, and emphasizes its potential benefits in early diagnosis and gene therapy-based treatment strategies.

Roles of F-box proteins in human digestive system tumors (Review)

F-box proteins (FBPs), the substrate-recognition subunit of E3 ubiquitin (Ub) ligase, are the important components of Ub proteasome system (UPS). FBPs are involved in multiple cellular processes through ubiquitylation and subsequent degradation of their target proteins. Many studies have described the roles of FBPs in human cancers. Digestive system tumors account for a large proportion of all the tumors, and their mortality is very high. This review summarizes for the first time the roles of FBPs in digestive system tumorige-nesis and tumor progression, aiming at finding new routes for the rational design of targeted anticancer therapies in digestive system tumors.

MicroRNA-106b in cancer-associated fibroblasts from gastric cancer promotes cell migration and invasion by targeting PTEN

It is well established that the interaction between cancer cells and microenvironment has a critical role in tumor development, but the roles of miRNAs in this interaction are rarely known. Here, we have shown that miR-106b is up-regulated in cancer associated fibroblasts compared with normal fibroblasts established from patients with gastric cancer, the expression level of miR-106b is associated with poor prognosis of patients, and CAFs with down-regulated miR-106b could significantly inhibit gastric cancer cell migration and invasion by targeting PTEN. Taken together, these data suggest that miR-106b might be a novel candidate target for the treatment of gastric cancer.

Therapeutic targets associated to E-cadherin dysfunction in gastric cancer

INTRODUCTION

Epithelial cadherin (E-cadherin) plays a key role in epithelial cell-cell adhesion, contributing to tissue differentiation and homeostasis. Throughout the past decades, research has shed light on the molecular mechanisms underlying E-cadherin's role in tumor progression, namely in invasion and metastization. Emerging evidence established E-cadherin as a tumor suppressor and suggests that targeting E-cadherin or downstream signaling molecules may constitute effective cancer therapeutics.

AREAS COVERED

This review aims to cover E-cadherin-mediated signaling during cancer development and progression and highlight putative therapeutic targets.

EXPERT OPINION

Reconstitution of E-cadherin expression or targeting of E-cadherin downstream molecules holds promise in cancer therapies. Considering the high frequency of CDH1 promoter hypermethylation as a second hit in malignant lesions from hereditary diffuse gastric cancer patients, histone deacetylase inhibitors are potential therapeutic agents in combination with conventional chemotherapy, specifically in initial tumor stages. Concerning E-cadherin-mediated signaling, we propose that HER receptors (as epidermal growth factor receptor) and Notch downstream targets are clinically relevant and should be considered in gastric cancer therapeutics and control.

MiR-214 regulate gastric cancer cell proliferation, migration and invasion by targeting PTEN

Background

MicroRNAs are a class of small non-coding RNAs that play an important role in various human tumor initiation and progression by regulating gene expression negatively. The aim of this study was to investigate the effect of miR-214 on cell proliferation, migration and invasion, as well as the functional connection between miR-214 and PTEN in gastric cancer.

Methods

miR-214 and PTEN expression was determined in gastric cancer and matched normal tissues, and human gastric cancer cell lines by quantitative real-time PCR. The roles of miR-214 in cell proliferation, migration and invasion were analyzed with anti-miR-214 transfected cells. In addition, the regulation of PTEN by miR-214 was evaluated by Western blotting and luciferase reporter assays.

Results

miR-214 was noted to be highly overexpressed in gastric cancer tissues and cell lines using qRT-PCR. The expression level of miR-214 is significantly associated with clinical progression and poor prognosis according to the analysis of the clinicopathologic data. We also found that the miR-214 levels are inversely correlated with PTEN in tumor tissues. And PTEN expression level is also associated with metastasis and invasion of gastric cancer. In addition, knockdown of miR-214 could significantly inhibit proliferation, migration and invasion of gastric cancer cells. Moreover, we demonstrate that PTEN is regulated negatively by miR-214 through a miR-214 binding site within the 3’-UTR of PTEN at the posttranscriptional level in gastric cancer cells.

Conclusions

These findings indicated that miR-214 regulated the proliferation, migration and invasion by targeting PTEN post-transcriptionally in gastric cancer. It may be a novel potential therapeutic agent for gastric cancer.

Reduced expression of PTEN and increased PTEN phosphorylation at residue Ser380 in gastric cancer tissues: a novel mechanism of PTEN inactivation

AIM

PTEN is a tumor suppressor gene in different cancers. This study was to determine the protein expression of PTEN and phosphorylation of PTEN (p-PTEN) at residue Ser380 in different histology specimens of gastric tissues.

METHODS

A total of 179tissue specimens of normal gastric mucosa, chronic gastritis, intestinal metaplasia, dysplasia, and gastric cancer were recruited for immunohistochemical analysis of PTEN and p-PTEN expression. Four gastric cancer AGS, MKN-45, MKN-28, and SGC-7901 cell lines and a non-cancerous gastric GES-1 cell line were used to detect expression of PTEN and p-PTEN protein using Western blot.

RESULTS

Expression level of PTEN protein was significantly decreased in gastric cancer tissues compared to normal gastric mucosa, chronic gastritis, intestinal metaplasia and dysplasia (P<0.05). In contrast, p-PTEN protein level was significantly increased in intestinal metaplasia, dysplasia and gastric cancer compared to normal gastric mucosa and chronic gastritis (P<0.05). However, there was no any association of PTEN and p-PTEN expression with clinicopathological characteristics from gastric cancer patients. Moreover, the ratio of p-PTEN and PTEN was higher in gastric cancer cell lines than that of the non-malignant cells.

CONCLUSIONS

This study demonstrated that aberrant expression of PTEN and p-PTEN at residue Ser380 was early event that could contribute to gastric carcinogenesis, and that PTEN phosphorylation at residue Ser380 could be a mechanism for PTEN inactivation.

A review of the association between osteosarcoma metastasis and protein translation

The malignant transformation of mesenchymal cells within the bone leads to the development of osteosarcoma (OS), but the genetic underpinnings of these events are not understood. From a clinical perspective, primary tumour management can be achieved successfully in most patients. However, the development of metastasis to the lungs represents the most common cause of death in OS patients. A clearer understanding of metastasis biology is required to improve cancer mortality and improve outcomes. Modelling the genetics, biology and therapy of OS can be accomplished through research involving a number of species. Most notable is the naturally occurring form of OS that develops in dogs. Through a cross-species and comparative approach important questions can be asked within specific and suitable models to advance our understanding of this disease and its common metastatic outcome. A comparative perspective on the problem of OS metastasis that utilizes a cross-species approach may offer unique opportunities to assist in this prioritization and generate new hypotheses related to this important clinical problem.

Sonic hedgehog pathway promotes metastasis and lymphangiogenesis via activation of Akt, EMT, and MMP-9 pathway in gastric cancer

Activation of sonic hedgehog (Shh) signaling has been implicated in progression of a variety of tumors. In this study, we elucidated a role for Shh in the invasion of gastric tumors and determined the mechanism by which Shh is regulated. Immunohistochemical analysis of 178 primary human gastric tumor biopsies indicated that Shh expression was positively correlated with lymph node metastasis, high lymphatic vessel density, and poor prognosis. In mouse xenograft models of human gastric cancer, enforced expression of Shh significantly enhanced the incidence of lung metastasis compared with nonexpressing controls. Mechanistic investigations revealed that phosphoinositide 3-kinase (PI3K)/Akt inhibition blocked Shh-induced epithelial-mesenchyme transition, the activity of matrix metalloproteinase 9 (MMP-9), and lymphangiogenesis, reducing tumor invasiveness and metastasis. Taken together, our findings establish that Shh signaling promotes the metastasis of gastric cancer through activation of the PI3K/Akt pathway, which leads to mesenchymal transition and MMP-9 activation. These findings offer preclinical validation of Shh as a candidate therapeutic target for treatment of metastatic gastric cancers.

Expression of PTEN and SHP1, investigated from tissue microarrays in pediatric acute lymphoblastic, leukemia

PTEN and SHP1 are tumor suppressor genes involved in the regulation of cell cycle control and apoptosis. The authors investigated the protein expression of PTEN and SHP1, by immunohistochemistry in tissue microarrays from bone marrow samples in children, diagnosed with acute lymphoblastic leukaemia and nonmalignant controls. PTEN was overexpressed in diagnostic ALL samples, while SHP1 showed a low expression. Both proteins showed a significant difference in expression compared to nonmalignant controls. The roles of PTEN and SHP1 are not well investigated in pediatric leukemia and could in the future play a role as prognostic factors.

Expression of NEDD4-1, a PTEN regulator, in gastric and colorectal carcinomas

Recent studies have disclosed that NEDD4-1 regulates PTEN activity by ubiquitination. NEDD4-1 negatively regulates PTEN in cytosol and acts as an oncogenic protein. By contrast, NEDD4-1 promotes PTEN nuclear import and acts as a tumor suppressor. Despite the importance of NEDD4-1 in PTEN regulation in cancer cells, expression of NEDD4-1 protein in cancer tissues is unknown. The aim of this study was to analyze NEDD4-1 expression in colorectal and gastric cancer tissues. We investigated NEDD4-1 protein expression in 103 colorectal and 60 gastric carcinoma tissues by immunohistochemistry using a tissue microarray approach. In the cancers, expression of NEDD4-1 was detected in 82 (80%) of the colorectal carcinomas and 45 (75%) of the gastric carcinomas in cytoplasm. By contrast, the normal mucosal cells of both stomach and colon showed no or very weak expression of NEDD4-1. There was no significant association of NEDD4-1 expression with clinicopathologic characteristics, including invasion, metastasis and stage. Our data indicate that NEDD4-1 overexpression is a feature of both colorectal and gastric carcinomas. The increased expression of NEDD4-1 in malignant gastric and colorectal cells compared to their normal epithelial cells suggests that NEDD4-1 expression may play a role in colorectal and gastric cancer development.

PCR-SSCP-DNA sequencing method in detecting PTEN gene mutation and its significance in human gastric cancer

AIM: To discuss the possible effect of PTEN gene mutations on occurrence and development of gastric cancer.

METHODS: Fifty-three gastric cancer specimens were selected to probe PTEN gene mutations in genome of gastric cancer and paracancerous tissues using PCR-SSCP-DNA sequencing method based on microdissection and to observe the protein expression by immunohistochemistry technique.

RESULTS: PCR-SSCP-DNA sequencing indicated that 4 kinds of mutation sites were found in 5 of 53 gastric cancer specimens. One kind of mutation was found in exons. AA-TCC mutation was located at 40bp upstream of 3’ lateral exon 7 (115946 AA-TCC). Such mutations led to terminator formation in the 297th codon of the PTEN gene. The other 3 kinds of mutation were found in introns, including a G-C point mutation at 91 bp upstream of 5’ lateral exon 5(90896 G-C), a T-G point mutation at 24 bp upstream of 5’ lateral exon 5 (90963 T-G), and a single base A mutation at 7 bp upstream of 5’ lateral exon 5 (90980 A del). The PTEN protein expression in gastric cancer and paracancerous tissues detected using immunohistochemistry technique indicated that the total positive rate of PTEN protein expression was 66% in gastric cancer tissue, which was significantly lower than that (100%) in paracancerous tissues (P < 0.005).

CONCLUSION: PTEN gene mutation and expression may play an important role in the occurrence and development of gastric cancer.

Targeting the AKT protein kinase for cancer chemoprevention

The AKT protein kinase transduces signals from growth factors and oncogenes to downstream targets that control crucial elements in tumor development. The AKT pathway is one of the most frequently hyperactivated signaling pathways in human cancers. Available data are reviewed herein to support targeting the AKT kinase for cancer prevention. This review will present data to show that AKT is up-regulated in preneoplastic lesions across a broad range of target tissues, briefly describe drug development efforts in this area, and present evidence that down-regulation of AKT signaling may be a viable strategy to prevent cancer.

Impact of loss of heterozygosity of encoding phosphate and tensin homolog on the prognosis of gastric cancer

BACKGROUND AND AIM

Encoding phosphate and tensin homolog (PTEN) is a cancer suppressor gene and it has been assumed that gene mutation and loss of heterozygosity (LOH) occurs frequently in various types of carcinoma. However, the role of LOH of PTEN and its outcome variables in gastric cancer have not been well established. In the present study, we investigated the roles of PTEN, LOH and their outcomes.

METHODS

Fresh frozen tumor samples from 119 gastric cancer patients with a primary diagnosis of gastric carcinoma were evaluated for LOH of PTEN using an automated sequencer. Results were compared with pathological parameters. The median follow-up period was 559 days.

RESULTS

Loss of heterozygosity of PTEN was observed in 17.1% of patients (13/76) diagnosed with gastric cancer. No particular relationship was found with any clinicopathological factor. However, the prognosis of patients with LOH of PTEN was significantly poor. Multivariate analyses revealed that vascular invasion, invasion depth, LOH of PTEN, histology and lymph node metastasis were correlated with survival of the patient.

CONCLUSIONS

Even though mutation of PTEN in gastric cancer has rarely been reported, according to our findings, LOH of PTEN frequently occurs in gastric cancers and is correlated with disease-related deaths. The LOH of PTEN is an independent prognostic factor and PTEN is a candidate as a haploinsufficient tumor suppressor in gastric cancers.

Expression of PTEN in the progression of cervical neoplasia and its relation to tumor behavior and angiogenesis in invasive squamous cell carcinoma

BACKGROUND AND OBJECTIVES

Loss of PTEN expression has been associated with tumor progression and adverse patient outcome. The purpose of this study was to evaluate PTEN expression in the successive steps of progression in cervical neoplasia and to determine its correlation with tumor angiogenesis and clinicopathologic features in squamous cell carcinoma of the uterine cervix.

METHODS

Immunohistochemical staining with anti-PTEN antibody was performed in a total of 160 patients with 12 normal cervical epithelium, 63 cervical intraepithelial neoplasia (33 CIN I, 30 CIN III), and 85 cervical squamous cell carcinomas. Microvessels were immunohistochemically labeled with an antibody for CD34. Computerized image analysis was used to evaluate microvessel density (MVD).

RESULTS

Reduced PTEN expression progressively increased along the continuum from normal epithelium to squamous cell carcinoma (P < 0.01). There was no significant correlation between PTEN expression and MVD. On univariate analysis, stage and reduced PTEN expression were significant prognostic factors for both disease-free and overall survival. However, stage was the only independent prognostic factor by multivariate analysis.

CONCLUSIONS

Our results suggest that tumor progression in the cervical epithelium is accompanied by loss of PTEN protein expression. Reduced PTEN expression is not associated with tumor angiogenesis of squamous cell carcinoma of the uterine cervix.

Bile acids induce ectopic expression of intestinal guanylyl cyclase C Through nuclear factor-kappaB and Cdx2 in human esophageal cells

BACKGROUND & AIMS

Although progression to adenocarcinoma at the gastroesophageal junction reflects exposure to acid and bile acids associated with reflux, mechanisms mediating this transformation remain undefined. Guanylyl cyclase C (GC-C), an intestine-specific tumor suppressor, may represent a mechanism-based marker and target of transformation at the gastroesophageal junction. The present studies examine the expression of GC-C in normal tissues and tumors from esophagus and stomach and mechanisms regulating its expression by acid and bile acids.

METHODS

Gene expression was examined by reverse-transcription polymerase chain reaction, promoter analysis, immunohistochemistry, immunoblotting, and functional analysis. Promoter transactivation was quantified by using luciferase constructs and mutational analysis. DNA binding of transcription factors was examined by electromobility shift analysis.

RESULTS

GC-C mRNA and protein were ectopically expressed in approximately 80% of adenocarcinomas arising in, but not in normal, esophagus and stomach. Similarly, in OE19 human esophageal cancer cells, deoxycholate and acid induced expression of GC-C. This was associated with the induction of expression of Cdx2, a transcription factor required for GC-C expression. In turn, induction of Cdx2 expression by deoxycholate was mediated by binding sites in the proximal promoter for nuclear factor kappaB (NF-kappaB). Furthermore, deoxycholate increased NF-kappaB activity, associated with nuclear translocation and Cdx2 promoter binding of the NF-kappaB subunit p50. Moreover, a dominant negative construct for NF-kappaB prevented deoxycholate-induced p50 nuclear translocation and activation of the Cdx2 promoter.

CONCLUSIONS

Transformation associated with reflux at the gastroesophageal junction reflects activation by bile acid and acid of a transcriptional program involving NF-kappaB and Cdx2, which mediate intestinal metaplasia and ectopic expression of GC-C.

Is the hypoxia-inducible factor pathway important in gastric cancer?

Tumour hypoxia is well recognised in oncology to be a key factor resulting in treatment resistance and poor prognosis. Hypoxia leads to the expression of a number of gene products that are involved in tumour progression, invasion and metastasis formation. The most important of these proteins is thought to be hypoxia-inducible factor-1alpha (HIF-1alpha), which appears to be a master regulator of the cellular response to hypoxia. HIF-1alpha expression is associated with a poor prognosis and treatment response in a number of tumour sites. There is some evidence that the HIF-1alpha pathway might be involved in gastric carcinogenesis. Studies have shown reactive oxygen species from Helicobacter pylori, associated with the development of gastric cancer, stabilise HIF-1alpha. Non-steroidal anti-inflammatory drugs, shown to reduce the risk of gastric cancer, can decrease HIF-1alpha expression. Although a large study correlating HIF-1alpha expression with prognosis is lacking in gastric cancer, the immunohistochemical expression of HIF-1alpha target genes (Glut-1, VEGF, CA9, iNOS) is associated with a poor prognosis. In addition, the targeted inhibition of HIF-1alpha has been shown to inhibit the growth of gastric tumours in animals. Increased understanding of the importance of hypoxia and the HIF-1alpha pathways may therefore hold the key to prevention strategies, improved selection of patients for adjuvant therapy and new treatments for the disease.

Relation of overexpression of S phase kinase-associated protein 2 with reduced expression of p27 and PTEN in human gastric carcinoma

AIM: To investigate the significance of S phase kinase-associated protein 2 (Skp2) expression in human gastric carcinoma and the relation between expressions of Skp2, p27 and PTEN.

METHODS: Immunohistochemical analysis was performed on 138 gastric carcinoma specimens, their paired adjacent mucosa specimens, 102 paired lymphatic metastatic carcinoma tissue specimens, 30 dysplasia specimens, 30 intestinal metaplasia specimens, 10 chronic superficial gastritis specimens and 5 normal gastric mucosa specimens for Skp2 expression and on 138 gastric carcinoma specimens for p27 and PTEN expression.

RESULTS: Skp2 labeling frequency was significantly higher in intestinal metaplasia (12.68±0.86) and adjacent mucosa (19.32±1.22) than in normal gastric mucosa (0.53±0.13) and chronic superficial gastritis (0.47±0.19) (P = 0.000); in dysplasia (16.74±0.82) than in intestinal metaplasia (P = 0.000); in gastric primary carcinoma (31.34±2.17) than in dysplasia and adjacent mucosa (P = 0.000); in metastasis gastric carcinoma in lymph nodes (39.76±2.00) than in primary gastric carcinoma (P = 0.037), respectively. Skp2 labeling frequency was positively associated with differentiation degree (rho = 0.315, P = 0.000), vessel invasion (rho = 0.303, P = 0.000) and lymph node metastasis (rho = 0.254, P = 0.000) of gastric cancer. Expression of Skp2 was negatively associated with p27 (rho = -0.451, P = 0.000) and PTEN (rho = -0.480, P = 0.000) expression in gastric carcinoma. p27 ex-pression was positively associated with PTEN expression in gastric carcinoma (rho = 0.642, P = 0.000).

CONCLUSION: Skp2 overexpression may be involved in carcinogenesis and progression of human gastric carcinoma in vivo, possibly via p27 proteolysis. PTEN may regulate the expression of p27 by negatively regulating Skp2 expression.

Heterozygosity loss of fragile histidine triad gene in gastric cancer and precancerous lesions

AIM: To detect the loss of heterozygosity (LOH) of fragile histidine triad (FHIT) gene in gastric cancer and precancerous lesions (dysplasia and intestinal metaplasia), and to analyze its role in the carcinogenesis of gastric cancer.

METHODS: The LOH at microsatellites loci D3S1234 and D3S1300 of FHIT gene were measured in samples of gastric cancer (n = 42), dysplasia (n = 44), intestinal metaplasia (n = 51) and their corresponding normal tissues by (polymerase chain reaction) PCR.

RESULTS: The rates of LOH at D3S1234 locus were 32.4%(11/34), 28.6%(10/35) and 10%(4/40) in gastric cancer, dysplasia and intestinal metaplasia respectively, and the ones at D3S1300 locus were 33.3%(12/36) , 32.4%(11/34) and 7.7% (3/39) respectively. The LOH rates at D3S1234 and D3S1300 loci in gastric cancer and atypical hyperplasia were higher than that of intestinal metaplasia (P<0.05, P<0.01 for D3S1234 and D3S1300 respectively). No significant difference of LOH rate was found between gastric cancer and dysplasia.

CONCLUSION: The loss of heterozygosity of FHIT gene may be an early event in the tumorigenesis of gastric cancer.

Effect of hypoxia on cell cycleand gene and protein expression in gastric cancer cell line MGC803

AIM: To investigate the effect of hypoxia on cell cycle, expression of mitochondrion ATP6 (mtATP6), mitochondrion Cyt-b (mtCyt-b), PTEN mRNA, vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) protein in human gastric cancer cell line MGC803.

METHODS: The MGC803 cells were exposed to anoxic environment for 0, 2, 8, 16, 24 h. The cell cycle was measured by flow cytometry, and the expression of mtATP6, mtCyt-b and PTEN mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR). Expression of VEGF and EGFR protein was determined by Western blot assay.

RESULTS: At 0, 2, 8, 16, and 24 h hypoxia, the rates of ATP6 mRNA expression of MGC803 cells were 78.22%, 69.28%, 84.40%, 39.84% and 42.52% respectively; Cyt-b mRNA expression was 83.40%, 75.87%, 64.57%, 79.05% and 77.44% respectively; PTEN mRNA expression was 23.93%, 26.52%, 35.74%, 40.31% and 49.92% respectively; VEGF protein expression was 16.1, 16.5, 18.2, 20.6, 27.5 and EGFR protein expression was 14.3, 17.2, 18.1, 32.6 and 37.7 respectively. The expression of PTEN mRNA, VEGF and EGFR proteins in vitro increased with the extending of hypoxia time. Expression of mtATP6 mRNA at 24 h was significantly reduced as compared with that under normal oxygen condition, and mtCyt-b mRNA was transiently reduced at 8 h but returned to normal level at 24 h. The MGC803 G₁ phase cells and apoptotic cells transiently increased after hypoxia as compared with those under normal oxygen condition. However, distribution of cell cycle at 24 h was similar to that under normal oxygen condition. There was no significant relation between hypoxia time and changes of cell cycles (P > 0.05).

CONCLUSION: Hypoxia transiently prolongs MGC803 G₁ phase and increases apoptotic rate of MGC803 cells. It up-regulates the expression of PTEN mRNA, VEGF and EGFR protein, and down-regulates the expression of mtATP6 mRNA.

Clinicopathological significance of maspin and Kail expressions in carcinogenesis and progression of gastric cancer

AIM: To investigate the expressions of maspin and Kai1 in gastric cancer and to explore their roles in tumorigenesis and progression of gastric cancer.

METHODS: Normal gastric mucosa (n = 182), gastric dysplasia (n = 69), and gastric cancer (n = 113) were detected for maspin and Kai1 expressions by immunohistochemical methods. The expressions were compared with clinicopathological parameters of the tumor. Relationship between maspin and Kai1 expressions was analyzed as well.

RESULTS: The positive rates of maspin expression were 79.8% (145/182), 75.4% (52/69), and 50.4% (57/113) in normal gastric mucosa, gastric dysplasia, and gastric cancer, while those of Kai1 expression were 81.9% (149/182), 65.2% (49/69), and 58.4% (66/113) in corresponding tissues, respectively. The gastric normal mucosa and dysplasia more frequently expressed maspin than primary gastric cancer did, (P <0.01), while the normal mucosa showed more frequent expression of Kai1 than dysplasia and primary cancer did (P <0.01). Maspin expression significantly related to invasive depth (P = 0.003<0.01), metastasis (P = 0.027<0.05), Lauren's (P = 0.015<0.05) and histological classification (P = 0.024<0.05), but not to tumor size, Borrmann's classification, growth pattern and TNM staging (P >0.05). Kai1 expression significantly related to invasive depth (P = 0.043<0.05), metastasis (P = 0.005<0.01), growth pattern (P = 0.034<0.05), Lauren's classification (P = 0.000<0.01) and histological classification (P = 0.004<0.01), but not to tumor size, Borrmann's classification and TNM staging (P >0.05). Maspin expression was significantly consistent with Kail expression in primary gastric cancer (P = 0.008<0.05).

CONCLUSION: Down-regulated expressions of maspin and Kai1 play an important role in gastric carcinogenesis. They may have inhibitory effects on invasion and metastasis of gastric cancer. Abnormal expressions of maspin and Kai1 might be an objective indicator for pathobiological behaviors of gastric cancer.

Role of PTEN and MMP-7 expression in growth, invasion, metastasis and angiogenesis of gastric carcinoma

To investigate the role of PTEN and matrix metalloproteinase-7 (MMP-7) expression in tumorigenesis and progression of gastric carcinoma, their expression in 113 gastric carcinomas was studied by immunohistochemistry. Microvessel density (MVD) was counted using the anti-CD34 antibody. The expressions of PTEN and MMP-7, and MVD were compared with the clinicopathological parameters of tumors, and the relationship between PTEN and MMP-7 expression and MVD was analyzed. It was found that PTEN was expressed less frequently in primary gastric carcinoma cells than in adjacent epithelial cells (P < 0.05), whereas this was reversed for MMP-7 (P < 0.05). PTEN expression was negatively correlated with invasion, metastasis, growth pattern, Lauren's classification and histological classification (P < 0.05). Matrix metalloproteinase-7 expression was positively associated with tumor size, Borrmann's classification, invasive depth, metastasis and TNM staging (P < 0.05), but negative with PTEN expression (P < 0.05). A positive correlation of MVD with tumor size, invasive depth, metastasis and TNM staging was found (P < 0.05). Microvessel density depended on decreased PTEN expression and increased MMP-7 expression (P < 0.05). The results of the present study suggested that down-regulated PTEN expression and up-regulated MMP-7 expression were greatly implicated in tumorigenesis and progression of gastric carcinoma. Close correlation between PTEN on MMP-7 expression provided a novel insight into the regulatory effects of PTEN on MMP-7 expression in gastric carcinoma.

Potassium antimonyl tartrate induces apoptosis in human gastric carcinoma cells

AIM: Potassium antimonyl tartrate (PAT), an antiparasitic agent, has rencently been shown to induce apoptosis of leukaemia cells. Its effects on human gastric cancer SGC-7901 cells and possible mechanism were investigated in this study.

METHODS: The growth inhibition of cells induced by various concentrations of PAT in different time course was analyzed by using MTT assay. The nuclei were stained by Hoechst 33 258 and the morphologic changes were observed by fluorescence microscope. TUNEL staining, double-staining, and flow cytomery were used to detect apoptosis of cells.

RESULTS: Growth inhibitory rates of SGC-7901 cells by PAT were significantly different in dose-and time-dependent manners (analysis of variance, P < 0.01). Chromatin condensation and nuclear fragmentation were seen under fluorescence microscope in the cells treated with Hoechst 33 258, and apoptotic cells were also detected by flow cytometry and TUNEL staining.

CONCLUSION: PAT can induce the apoptosis of SGC-7901 cells, and PAT may be a promising apoptosis-inducer in gastric cancer therapy.

Relationship between expression of VEGF, Flt1, bFGF and P53and outcome in patients with gastric carcinoma

AIM: To investigate the relationship between the expression of VEGF, Flt1, bFGF and P⁵³, the clinicopathological characteristics and outcome in patients with gastric carcinoma.

METHODS: The relationship between VEGF, Flt1, bFGF, P⁵³ expression and clinicopathological characteristics and outcome in the patient was assessed by streptoavidin-biotin method of immunohistochemistry with polyclonal antibodies against VEGF, Flt1, bFGF, and P⁵³ protein. The survival curves were formulated using Kaplan-Meier method and analyzed by the log-rank test, and the influence of each variable on suvival was assessed by the Cox' s proportional hazard model.

RESULTS: VEGF expression was closely correlated with serosal invasion (Se, Sei invasion vs Pm, SS and M, SM invasion, P < 0.01). Expression of P⁵³ was obviously higher in the patients with lymph node metastasis than those without (lymph node metastasis vs non-lymph node metastasis, P < 0.05). There was a positive correlation between VEGF and Flt1 expression (VEGF expression in Flt1 positive group vs Flt1 negative group, P < 0.01). The factors that affected the prognosis in patients with gastric carcinoma were PTNM stage, VEGF expression, serosal invasion, and surgical curability. Flt1, bFGF, and P⁵³ expression had no influence on the prognosis of patients with gastric carcinoma (P > 0.05).

CONCLUSION: P⁵³ expression has significant relationship with lymph node metastasis in gastric carcinoma. VEGF expression is correlated with serosal invasion and the prognosis and may be a good prognostic indicator in gastric carcinoma.

Gene expression profiling in intestinal-type gastric carcinoma by cDNA microarray

AIM: To identify a set of genes involved in the development of intestinal-type gastric carcinoma.

METHODS: Pure mRNAs from 6 cases of intestinal-type gastric carcinoma and corresponding noncancerous mucosae were reversely transcribed into cDNAs labeled with Cy5 and Cy3 dyes for probes, then mixed and hybridized with the cDNA microarray consisting of 4 096 genes, and the fluorescent signals were scanned.

RESULTS: Among total genes, 333 were up-regulated and 333 down-regulated in intestinal-type gastric cancer tissues. Within altered expression of those genes, cell-cycle regulators and growth factors were up-regulated, and the promoter genes of apoptosis were down-regulated; Oncogenes and cell-adhesion molecules were more up-regulated; The cancer progression genes were up-regulated, while the anti-cancer progression genes were down-regulated.

CONCLUSION: The quick and high-throughout method of gene expression profile by cDNA array provides us with an overview of gene changes that may involved in intestinal-type gastric cancer development, and will open up new possibilities to identify novel molecular targets for diagnosis and therapy. Several genes are altered in intestinal-type gastric cancer, which need to be further investigated.

Inactivation of the PTEN gene protein product is associated with the invasiveness and metastasis, but not angiogenesis, of breast cancer

PTEN is a novel tumor-suppressor gene located on chromosomal band 10q23. Loss of PTEN function has been implicated in the progression of several types of cancer, but the correlation between loss of PTEN expression and advanced carcinomas is not well established. The capacity for angiogenesis of a tumor is known to play a very important role in growth and metastasis, and there have been reports that PTEN relates to angiogenesis. In the present study, formalin-fixed and paraffin embedded tissues from 101 patients with breast carcinomas, including 88 cases of invasive ductal carcinomas and 13 cases of ductal carcinoma in situ (DCIS), were evaluated by immunohistochemical methods for the expression of PTEN and vascular endothelial growth factor (VEGF), as well as microvessel density (MVD). The results were compared with the clinicopathologic parameters. There was no loss of PTEN expression in any of the cases of DCIS, but 28 (32%) of the 88 invasive cases did not express PTEN. Loss of PTEN expression was associated with lymph node metastasis (P = 0.03), but did not correlate with tumor size, tumor grade, MVD or recurrence. VEGF expression significantly correlated with lymph node metastasis in invasive ductal carcinoma (P = 0.01). There was no correlation between the expression of PTEN and that of VEGF (P = 0.63). The present study suggests that loss of PTEN expression is common and correlates with tumor progression and lymph node metastasis in breast carcinoma. The relationship between loss of PTEN and progression of breast cancer may not be explained by modulation of angiogenesis.

Expression of MTLC gene in gastric carcinoma

AIM: To investigate the expression of c-myc target from laryngeal cancer cells (MTLC) gene in gastric carcinoma (GC) tissues and the effect of MTLC over-expression on gastric carcinoma cell line BGC823.

METHODS: RT-PCR was performed to determine the expression of MTLC mRNA in GC and matched control tissues. BGC823 cells were transfected with an expression vector pcDNA3.1-MTLC by liposome and screened by G418. Growth of cells expressing MTLC was observed daily by manual counting. Apoptotic cells were determined by TdT-mediated dUTP nick-end labeling (TUNEL) assay.

RESULTS: The expression of MTLC mRNAs was down-regulated in 9 (60%) of 15 cases of GC tissues. The growth rates of the BGC823 cells expressing MTLC were indistinguishable from that of control cells. A marked acceleration of apoptosis was observed in MTLC-expressing cells.

CONCLUSION: MTLC was down-regulated in the majority of GC tissues and could promote apoptosis of GC cell lines, which suggests that MTLC may play an important role in the carcinogenesis of gastric carcinoma.

Expression of PTEN encoding product in malignant lesions of gastric mucosa and its significance

AIM

To observe the expression of PTEN protein in gastric cancer and precancerous lesions, and to investigate the relationship between PTEN expression and the pathogenesis of gastric cancer.

METHODS

Normal gastric mucosa,chronic superficial gastritis, atrophic gastritis without intestinal metaplasia, atrophic gastritis with intestinal metaplasia, moderate and severe dysplasia, early and advanced gastric cancer, 60 cases each group, were selected for PTEN protein expression by SP immunohistochemistry.

RESULTS

The expression of PTEN encoding product in normal gastric mucosa was 100%. For chronic superficial gastritis, atrophic gastritis without intestinal metaplasia, atrophic gastritis with intestinal metaplasia, moderate dysplasia, severe dysplasia, the PTEN protein expression rate was 98.3%, 91.6%, 78.3%, 75%, 63.3%,respectively. The expression of PTEN protein in early stage and advanced gastric cancer was 61.7% and 43.3% respectively. Among the 120 cases of gastric cancer, 76 cases were intestinal type gastric cancer, the PTEN protein expression was 60.5%, 44 cases were diffuse gastric cancer , the PTEN protein expression was 38.6%.

CONCLUSION

The expression of PTEN protein is downregulated in the process of gastric cancer, PTEN protein can be used as a maker to evaluate the biological behaviours of gastric cancer.

Screening and identification of mimotope of gastric cancer associated antigen MGb1-Ag

AIM: Using a monoclonal antibody against gastric cancer antigen named MGb1 to screen a phage-displayed random peptide library fused with coat protein pIII in order to get some information on mimotopes.

METHODS: Through affinity enrichment and ELISA screening, positive clones of phages were amplified. 10 phage clones were selected after three rounds of biopanning and the ability of specific binding of the positive phage clones to MGb1-Ab were detected by ELISA assay (DNA sequencing was performed and the amino acid sequences were deduced) By blocking test, specificity of the mimic phage epitopes was identified.

RESULTS: There were approximately 200 times of enrichment about the titer of bound phages after three rounds of biopanning procedures. DNA of 10 phage clones after the third biopanning was assayed and the result showed that the positive clones had a specific binding activity to MGb1-Ab and a weak ability of binding to control mAb or to mouse IgG. DNA sequencing of 10 phage clones was performed and the amino acid sequences were deduced. According to the homology of the amino acid sequences of the displayed peptides, most of the phage clones had motifs of H(x)Q or L(x)S. And these 10 phage clones could also partly inhibit the binding of MGb1-Ab to gastric cancer cell KATO-III. The percentage of blocking was from (21.0 ± 1.6)% to (39.0 ± 2.7)%.

CONCLUSION: Motifs of H(x)Q and L(x)S selected and identified show a high homology in the mimic epitopes of gastric cancer associated antigen. There may be one or more clones which can act as candidates of tumor vaccines.

Relationship between expression of matrix metalloproteinase-7 and clinic-opathobiological behaviors of gastric cancer

AIM

To investigate the role of matrix metalloproteinase-7 (MMP-7) expression in caricinogenesis and progression of gastric cancer.

METHODS

We studied MMP-7 expression and microvessel density (MVD) in primary foci of 113 cases of gastric cancer by streptavidin-biotin-immunoperoxidase method with anti-MMP-7 and anti-CD34 antibodies. MMP-7 expression and mean MVD in primary foci were compared with clinicopathological features of tumors, and the relationship between MMP-7 expression and mean microvessel densities (MVD) in gastric cancer was concerned as well.

RESULTS

MMP-7 showed positive expression in 29.2 % (33/113) of adjacent mucosa of gastric cancer was less than that in its primary foci (69.0 %, 78/113) of gastric cancer. MMP-7 expression in primary foci was closely correlated with tumor size, invasive depth, metastasis and TNM staging of gastric cancer (P <0.05) despite no significant relationship between its expression and differentiation or growth pattern (P >0.05). Positive correlation of mean MVD with tumor size, depth of invasion, metastasis and TNM staging was found (P <0.05), but no relationship was found between mean MVD or differentiation of gastric cancer (P >0.05). Especially, mean MVD was dependent on MMP-7 expression in gastric cancer (P <0.05).

CONCLUSION

MMP-7 is an effective marker to reveal the biological behaviors of gastric cancer and plays an important role in carcinogenesis and progression of gastric cancer by participating in growth, invasion, metastasis and angio-genesis.