MiR‐133b inhibits growth of human gastric cancer cells by silencing pyruvate kinase muscle‐splicer polypyrimidine tract‐binding protein 1

The metabolism in tumor cells shifts from oxidative phosphorylation to glycolysis even in an aerobic environment. This phenomenon is known as the Warburg effect. This effect is regulated mainly by polypyrimidine tract‐binding protein 1 (PTBP1), which is a splicer of the mRNA for the rate‐limiting enzymes of glycolysis, pyruvate kinase muscle 1 and 2 (PKM1 and PKM2). In the present study, we demonstrated that miR‐133b reduced PTBP1 expression at translational level and that the expression levels of miR‐133b were significantly downregulated in gastric cancer clinical samples and human cell lines, whereas the protein expression level of PTBP1 was upregulated in 80% of the 20 clinical samples of gastric cancer examined. Ectopic expression of miR‐133b and knockdown of PTBP1 in gastric cancer cells inhibited cell proliferation through the induction of autophagy by the switching of PKM isoform expression from PKM2‐dominant to PKM1‐dominant. The growth inhibition was partially canceled by an autophagy inhibitor 3‐MA or a reactive oxygen species scavenger N‐acetylcysteine. These findings indicated that miR‐133b acted as a tumor‐suppressor through negative regulation of the Warburg effect in gastric cancer cells.     

miR‐212 is downregulated and suppresses methyl‐CpG‐binding protein MeCP2 in human gastric cancer

To clarify the role of micro (mi) RNAs in gastric carcinogenesis, we studied the expression and function of miRNAs in gastric carcinoma (GC) cells. Initially, we performed microarray analysis using total RNA from 3 human GC cell lines and noncancerous gastric tissue. Among the downregulated miRNAs in GC cells, miR‐212 expression was decreased in all 8 GC cell lines examined and a significant decrease of miR‐212 expression in human primary GC tissues was also observed in 6 of 11 cases. Transfection of the precursor miR‐212 molecule induced decreased growth of 3 GC cell lines. Using 3 different databases, methyl‐CpG‐binding protein MeCP2 was postulated to be a target of miR‐212. As seen on reporter assaying, miR‐212 repressed the construct with the MECP2 3′‐UTR. Ectopic expression of miR‐212 repressed expression of the MeCP2 protein but not the MECP2 mRNA level. These data suggest that downregulation of miR‐212 may be related to gastric carcinogenesis through its target genes, such as MECP2.     

Deubiquitinase PSMD14 promotes ovarian cancer progression by decreasing enzymatic activity of PKM2

Dysregulation of deubiquitination has been reported to contribute to carcinogenesis. However, the function and mechanism of deubiquitinating enzyme 26S proteasome non‐ATPase regulatory subunit 14 (PSMD14) in the progression of ovarian cancer (OV), the deadliest gynecological cancer, still remains to be characterized. The present study demonstrated that PSMD14 was overexpressed in OV tissues and its higher levels correlated with a higher International Federation of Gynecology and Obstetrics (FIGO) stage in OV patients. A high level of PSMD14 expression was related to poor survival in OV patients. Knockdown and overexpression experiments elucidated that PSMD14 stimulated OV cell proliferation, invasion, and migration in vitro. Repression of PSMD14 suppressed OV tumor growth in vivo. PSMD14 inhibitor O‐phenanthroline (OPA) effectively attenuated malignant behaviors of OV cells in vitro and OV tumor growth in vivo. Mechanistically, we uncovered that PSMD14 was involved in post‐translational regulation of pyruvate kinase M2 isoform (PKM2). PSMD14 decreased K63‐linked ubiquitination on PKM2, downregulated the ratio of PKM2 tetramers to dimers and monomers, and subsequently diminished pyruvate kinase activity and induced nuclear translocation of PKM2, contributing to aerobic glycolysis in OV cells. Collectively, our findings highlight the potential roles of PSMD14 as a biomarker and therapeutic candidate for OV.     

Apoptosis signal‐regulating kinase‐1 inhibitor as a potent therapeutic drug for the treatment of gastric cancer

Aside from the human epidermal growth factor receptor‐2 (HER2)‐targeting agent trastuzumab, molecular targeting therapy for gastric cancer (GC) has not been established. We previously reported that apoptosis signal‐regulating kinase‐1 (ASK1) was upregulated in human GC and that overexpression of ASK1 promoted GC cell proliferation. Here, we investigated the effect of ASK1 inhibitor K811 on GC cells. K811 efficiently prevented cell proliferation in cell lines with high ASK1 expression and in HER2‐overexpressing GC cells. Treatment with K811 reduced sizes of xenograft tumors by downregulating proliferation markers. These results indicate that ASK1 inhibition prevents GC cell growth in vitro and in vivo, suggesting that ASK1 inhibitors can be potent therapeutic drugs for GC.     

Helicobacter pylori antibody responses and evolution of precancerous gastric lesions in a Chinese population

Helicobacter pylori‐specific proteins are involved in gastric carcinogenesis. To investigate the seroprevalence of six H. pylori‐specific antibodies in patients with different gastric histology, and the impact of seropositivities on the evolution of precancerous gastric lesions, a follow‐up study was conducted in Linqu County, China. The seropositivities for CagA, VacA, GroEL, UreA, HcpC and gGT were assessed by recomLine analysis in 573 H. pylori‐positive subjects and correlated with evolution of precancerous gastric lesions. We found that the score of H. pylori recomLine test was significantly increased in subjects with chronic atrophic gastritis (CAG, p < 0.0001) or intestinal metaplasia (IM, p = 0.0125), and CagA was an independent predictor of advanced gastric lesions, adjusted odds ratios (ORs) were 2.54 (95% CI = 1.42–4.55) for IM and 2.38 (95% CI = 1.05–5.37) for dysplasia (DYS). Moreover, seropositivities for CagA and GroEL were identified as independent predictors for progression of gastric lesions in a longitudinal study, and ORs were 2.89 (95% CI = 1.27–6.59) and 2.20 (95% CI = 1.33–3.64), respectively. Furthermore, the risk of progression was more pronounced in subjects with more than three positive antigens (p_{for trend} = 0.0003). This population‐based study revealed that seropositivities for CagA and GroEL might be potential markers to identify patients infected with high‐risk H. pylori strains, which are related to the development of GC in a Chinese high‐risk population, and recomLine test might serve as a tool for risk stratification.     

Benserazide is a novel inhibitor targeting PKM2 for melanoma treatment

The M2 splice isoform of pyruvate kinase (PKM2) is a key enzyme for generating pyruvate and ATP in the glycolytic pathway, whereas the role of PKM2 in tumorigenesis remains a subject of debate. In our study, we found PKM2 is highly expressed in melanoma patients and the malignance is positively correlated with high PKM2 activity and glycolytic capability in melanoma cells. Suppression of PKM2 expression by knocking down markedly attenuated malignant phenotype both in vitro and in vivo, and restoration of PKM2 expression in PKM2 depleted cells could rescue melanoma cells proliferation, invasion and metastasis. With the data indicating PKM2 as a potential therapeutic target, we performed screening for PKM2 inhibitors and identified benserazide (Ben), a drug currently in clinical use. We demonstrated that Ben directly binds to and blocks PKM2 enzyme activity, leading to inhibition of aerobic glycolysis concurrent up-regulation of OXPHOS. Of note, despite PKM2 is very similar to PKM1, Ben does not affect PKM1 enzyme activity. We showed that Ben significantly inhibits cell proliferation, colony formation, invasion and migration in vitro and in vivo. The specificity of Ben was demonstrated by the findings that, suppression of PKM2 expression diminishes the efficacy of Ben in inhibition of melanoma cell growth; ectopic PKM2 expression in normal cells sensitizes cells to Ben treatment. Interestingly, PKM2 activity and aerobic glycolysis are upregulated in BRAFi-resistant melanoma cells. As a result, BRAFi-resistant cells exhibit heightened sensitivity to suppression of PKM2 expression or treatment with Ben both in vitro and in vivo.     

Differential oncogenic potential of geographically distinct Helicobacter pylori CagA isoforms in mice

Infection with cagA‐positive Helicobacter pylori is associated with gastric carcinoma. The cagA‐encoded CagA protein is delivered into gastric epithelial cells and, upon tyrosine phosphorylation at the C‐terminal EPIYA segments, binds and deregulates SHP‐2 oncoprotein. On the basis of the differential alignment of the EPIYA segments, CagA can be subdivided into Western CagA, which is produced by H. pylori isolated in Western countries, and East Asian CagA, which is produced by H. pylori circulating in East Asian countries. Western CagA contains EPIYA‐A, EPIYA‐B and variable numbers of EPIYA‐C segments, whereas East Asian CagA contains EPIYA‐A, EPIYA‐B and variable numbers of EPIYA‐D segments. Upon tyrosine phosphorylation, EPIYA‐C and EPIYA‐D, respectively, serve as low‐affinity and high‐affinity SHP‐2‐binding sites. We previously reported that systemic expression of East Asian CagA (CagA‐ABDD) induces gastrointestinal and hematopoietic malignancies in mice. In this study, we generated transgenic mice that systemically express Western CagA (CagA‐ABCCC), the levels of which are comparable to those in mice expressing East Asian CagA. The mice developed gastric epithelial hypertrophy and gastrointestinal tumors and also showed lymphoid abnormality but not myeloid abnormalities such as granulocytosis and myeloid leukemia found in mice carrying East Asian CagA. The incidence of tumors in mice expressing Western CagA was significantly lower than that in mice expressing East Asian CagA. Our results indicate that Western CagA is qualitatively less oncogenic than East Asian CagA. Differential oncogenic potential of geographically distinct CagA isoforms may contribute to the differential prevalence of gastric carcinoma between East Asian countries and Western countries. © 2009 UICC     

Natural variant of the Helicobacter pylori CagA oncoprotein that lost the ability to interact with PAR1

Helicobacter pylori strains carrying the cagA gene are associated with severe disease outcomes, most notably gastric cancer. CagA protein is delivered into gastric epithelial cells by a type IV secretion system. The translocated CagA undergoes tyrosine phosphorylation at the C‐terminal EPIYA motifs by host cell kinases. Tyrosine‐phosphorylated CagA acquires the ability to interact with and activate SHP2, thereby activating mitogenic signaling and inducing cell morphological transformation (hummingbird phenotype). CagA also interacts with PAR1b via the CM sequence, resulting in induction of junctional and polarity defects. Furthermore, CagA‐PAR1b interaction stabilizes the CagA‐SHP2 complex. Because transgenic mice systemically expressing CagA develop gastrointestinal and hematological malignancies, CagA is recognized as a bacterium‐derived oncoprotein. Interestingly, the C‐terminal region of CagA displays a large diversity among H. pylori strains, which influences the ability of CagA to bind to SHP2 and PAR1b. In the present study, we investigated the biological activity of v225d CagA, an Amerindian CagA of H. pylori isolated from a Venezuelan Piaroa Amerindian subject, because the variant CagA does not possess a canonical CM sequence. We found that v225d CagA interacts with SHP2 but not PAR1b. Furthermore, SHP2‐binding activity of v225d CagA was much lower than that of CagA of H. pylori isolated from Western countries (Western CagA). v225d CagA also displayed a reduced ability to induce the hummingbird phenotype than that of Western CagA. Given that perturbation of PAR1b and SHP2 by CagA underlies the oncogenic potential of CagA, the v225d strain is considered to be less oncogenic than other well‐studied cagA‐positive H. pylori strains.     

Helicobacter pylori CagA oncoprotein interacts with SHIP2 to increase its delivery into gastric epithelial cells

Chronic infection with Helicobacter pylori cagA‐positive strains is causally associated with the development of gastric diseases, most notably gastric cancer. The cagA‐encoded CagA protein, which is injected into gastric epithelial cells by bacterial type IV secretion, undergoes tyrosine phosphorylation at the Glu‐Pro‐Ile‐Tyr‐Ala (EPIYA) segments (EPIYA‐A, EPIYA‐B, EPIYA‐C, and EPIYA‐D), which are present in various numbers and combinations in its C‐terminal polymorphic region, thereby enabling CagA to promiscuously interact with SH2 domain‐containing host cell proteins, including the prooncogenic SH2 domain‐containing protein tyrosine phosphatase 2 (SHP2). Perturbation of host protein functions by aberrant complex formation with CagA has been considered to contribute to the development of gastric cancer. Here we show that SHIP2, an SH2 domain‐containing phosphatidylinositol 5′‐phosphatase, is a hitherto undiscovered CagA‐binding host protein. Similar to SHP2, SHIP2 binds to the Western CagA‐specific EPIYA‐C segment or East Asian CagA‐specific EPIYA‐D segment through the SH2 domain in a tyrosine phosphorylation‐dependent manner. In contrast to the case of SHP2, however, SHIP2 binds more strongly to EPIYA‐C than to EPIYA‐D. Interaction with CagA tethers SHIP2 to the plasma membrane, where it mediates production of phosphatidylinositol 3,4‐diphosphate [PI(3,4)P₂]. The CagA‐SHIP2 interaction also potentiates the morphogenetic activity of CagA, which is caused by CagA‐deregulated SHP2. This study indicates that initially delivered CagA interacts with SHIP2 and thereby strengthens H. pylori‐host cell attachment by altering membrane phosphatidylinositol compositions, which potentiates subsequent delivery of CagA that binds to and thereby deregulates the prooncogenic phosphatase SHP2.     

miR-133a-3p在胃癌组织和血浆中的表达及其对胃癌细胞增殖的影响

[摘要] 目的：检测miR-133a-3p 在胃癌组织及患者血浆中的表达水平及其对胃癌细胞增殖的影响,并探讨其与患者预后的关系。方法：收集河北医科大学第四医院普外科2012 年5 月至2013 年5 月胃癌手术切除的组织标本及术前外周静脉血标本52例,每例组织标本采集肿瘤组织(非坏死部分)和配对的癌旁组织。采用实时荧光定量RT-PCR（RT-qPCR）法检测miR-133a-3p 在胃癌组织、癌旁组织、血浆及健康体检者血浆（35 例）的表达情况,分析miR-133a-3p 的表达水平与胃癌患者中位DFS及临床病理特征的关系。CCK-8 法检测过表达或沉默miR-133a-3p 对胃癌SGC7901 细胞增殖的影响。结果：miR-133a-3p 在胃癌组织中的表达明显降低（P<0.01）,其表达水平与肿瘤TNM分期、肿瘤侵润深度（T）、淋巴结转移（N）及脉管瘤栓相关（P<0.01）;在胃癌患者血浆中的表达明显升高（P<0.01）,其表达水平与肿瘤TNM分期、淋巴结转移（N）及脉管瘤栓相关（P<0.05）;与患者血清中CA199的表达水平正相关（P<0.01）。胃癌组织中miR-133a-3p 高表达组患者中位DFS 明显高于低表达组（20.8 vs 14.8 个月,P<0.05）。血浆中miR-133a-3p 的高表达组患者中位DFS明显低于低表达组（14.4 vs 20.3 个月,P<0.05）。过表达miR-133a-3p 可明显抑制SGC7901 细胞的增殖能力,同样沉默其表达可明显促进SGC701 细胞的增殖能力（均P<0.05）。结论：miR-133a-3p 可明显抑制胃癌细胞SGC7901 的增殖能力,在胃癌组织和血浆中存在明显异常表达,其表达与患者预后明显相关,可作为胃癌早诊早治及患者临床预后判定的潜在标志物。     

Metastasis‐associated in colon cancer‐1 upregulation predicts a poor prognosis of gastric cancer,and promotes tumor cell proliferation and invasion

Metastasis‐associated in colon cancer‐1 (MACC1) is a newly identified oncogene, and little is known about its role in gastric cancer (GC). Our study was performed to investigate whether MACC1 influences the prognosis of GC patients and to explore the potential mechanisms involved. MACC1 expression was verified to be higher in GC tissues than in adjacent nontumorous tissues by Western blotting. A retrospective analysis of 361 GC patients (Stages I–IV) revealed that higher MACC1 expression was associated with more advanced disease, more frequent postoperative recurrence, more metastases and a higher mortality rate. The disease‐free survival of Stage I–III patients and overall survival of Stage‐IV patients were significantly worse when their tumors showed high MACC1 expression. To investigate the underlying mechanisms, MACC1 overexpression and downregulation were established in two GC cell lines (BGC‐823 and MKN‐28 cells). MACC1 overexpression significantly accelerated tumor growth and facilitated metastasis in athymic mice. MACC1 also promoted the proliferation, migration and invasion of both GC cell lines. Moreover, gastric MACC1 mRNA expression levels were significantly correlated with markers of the epithelial‐to‐mesenchymal transition (EMT) in patients with GC. MACC1 overexpression upregulated mesenchymal–epithelial transition factor and induced changes to markers of EMT, whereas silencing of MACC1 reversed all these changes. These findings provide some novel insights into the role of MACC1, a gene that contributes to a poor prognosis of GC by promoting tumor cell proliferation and invasion as well as the EMT.     

Cancer‐associated fibroblast‐derived Lumican promotes gastric cancer progression via the integrin β1‐FAK signaling pathway

Gastric cancer (GC) is one of the most frequent malignant tumors worldwide and is associated with high invasiveness, high metastasis and poor prognosis. Cancer‐associated fibroblasts (CAFs), residing around tumor cells in tumor stroma, are important modifiers of tumor initiation and progression. However, the molecular mechanisms by which CAF's modulate tumor development have yet not to be characterized in GC. Here we performed tissue assay analyses identifying that Lumican, an extracellular matrix protein, is highly expressed in human gastric CAFs and its expression is positively associated with depth of invasion, lymph node metastasis, TNM stage and poor survival rate of GC. Functional studies revealed that integrin β1‐FAK signaling pathways mediate the promoting effect of Lumican on GC cell proliferation, migration and invasion in vitro. In accordance with these observations, in GC cells co‐cultured with CAFs in which Lumican had been knocked down, decreased gastric tumor growth and metastasis in vivo was apparent. In summary, CAF‐derived Lumican contributes to tumorigenesis and metastasis of GC by activating the integrin β1‐FAK signaling pathway.     

长链非编码RNA ATB在胃癌中的表达及对糖酵解水平的影响

目的:探讨长链非编码RNA（lncRNA） ATB对胃癌细胞糖酵解水平的影响。方法:实时定量PCR检测80例胃癌组织标本以及相应癌旁组织中lncRNA ATB的表达水平并利用葡萄糖、乳酸含量评价ATB对胃癌细胞糖酵解水平的影响。结果:lncRNA ATB在胃癌组织表达高于癌旁组织，差异有统计学意义(P<0.05)。当胃癌细胞中敲除ATB后，能够显著降低胃癌细胞摄取葡萄糖和排放乳酸的含量。结论:在胃癌组织中ATB表达高于癌旁组织；在体外细胞实验中发现，ATB够促进胃癌细胞糖酵解水平，其能够有望成为胃癌治疗的潜在靶点。     

Therapeutic potential of highly cytotoxic natural killer cells for gastric cancer

To develop more effective therapies for patients with advanced gastric cancer, we examined the potential of ex vivo expanded natural killer (NK) cells. We assessed the expression of ligands for NK Group 2 Member D (NKG2D, an important NK activation molecule) in primary tumors from 102 patients with gastric cancer by immunohistochemistry and determined their prognostic value. We then examined the in vitro and in vivo cytotoxicity of NK cells from healthy donors and patients with gastric cancer. The cytotoxicity of resting and of interleukin (IL)‐2‐activated NK cells was compared to that of NK cells expanded for 7 days by coculture with the K562‐mb15‐4.1BBL cell line. As a result, the expression of NKG2D ligands in primary tumors was correlated with favorable presenting features and outcomes, suggesting that gastric cancer may be sensitive to NK cell cytotoxicity. Although resting NK cells showed minimal cytotoxicity against gastric cancer cells, K562‐mb15‐4.1BBL‐expanded NK cells were highly cytotoxic and significantly more powerful than IL‐2‐activated NK cells. Cytotoxicity was correlated with NKG2D ligand expression and could be modulated by mitogen‐activated protein kinase and AKT‐PI3 kinase inhibitors. The cytotoxicity of expanded NK cells against HER2‐positive gastric cancer cells could be increased by Herceptin and further augmented by Lapatinib. Finally, expanded NK cells exhibited strong antitumor activity in immunodeficient mice engrafted with a gastric cancer cell line. In conclusion, gastric cancer tumors express NKG2D ligands and are highly susceptible to killing by NK cells stimulated by K562‐mb15‐4.1BBL. These results provide a strong rationale for clinical testing of these NK cells in patients and suggest their use to augment the effects of antibody therapy.     

Fibroblast growth factor receptor 4 regulates proliferation and antiapoptosis during gastric cancer progression

BACKGROUND:

Fibroblast growth factor receptor 4 (FGFR4) belongs to the tyrosine kinase receptor family. Little is known about the effect of FGFR4 on gastric cancer (GC). Therefore, the objective of the current study was to elucidate the role of FGFR4 in the tumorigenesis and progression of GC.

METHODS:

FGFR4 and some common prognosis markers, including p53, neu, and proliferating cell nuclear antigen (PCNA), were detected in 71 tissue samples from patients with GC using immunohistochemical analysis. In addition, a series of functional assays were carried out using small interfering RNA (siRNA) and included proliferation assays, clone assays, and apoptosis detection.

RESULTS:

Cytoplasmic FGFR4 expression in GC tissues was negative (7% of samples), low (14.1% of samples), intermediate (40.8%), and high (38% of samples). FGFR4 expression was associated with lymph node status and with PCNA and neu expression (P < .05). The 5‐year relative survival rate was 61.5% in patients who had GC with low FGFR4 expression but was only 42% in patients who had high FGFR4 expression (P = .058). A subgroup analysis of the patients who had high FGFR4 expression revealed that those with stage III and IV disease had a worse prognosis (P = .044). Moreover, knockdown of FGFR4 expression led to decreased proliferation and an increased rate of apoptosis in the MKN45 and SGC7901 GC cell lines (P < .05). Western blot analysis demonstrated that the expression of caspase 3 increased, whereas the expression of extra‐large B‐cell lymphoma (Bcl‐xL) decreased in MKN45 and SGC7901 cells after FGFR4‐siRNA transfection.

CONCLUSIONS:

FGFR4 expression in GC tissue was extremely high. The current results indicated that FGFR4 may contribute to the progression of GC by regulating proliferation and antiapoptosis, indicating that FGFR4 may be a potential, novel drug target against GC. Cancer 2011;. © 2011 American Cancer Society.     

High KRT8 expression promotes tumor progression and metastasis of gastric cancer

Keratin8 (KRT8) is the major component of the intermediate filament cytoskeleton and predominantly expressed in simple epithelial tissues. Aberrant expression of KRT8 is associated with multiple tumor progression and metastasis. However, the role of KRT8 in gastric cancer (GC) remains unclear. In this study, KRT8 expression was investigated and it was found to be upregulated along with human GC progression and metastasis at both mRNA and protein levels in human gastric cancer tissues. In addition, KRT8 overexpression enhanced the proliferation and migration of human gastric cancer cells, whereas the knock‐down of KRT8 by siRNA only inhibited migration of human gastric cancer cells. Integrinβ1‐FAK‐induced epithelial‐mesenchymal‐transition (EMT) only existed in the high KRT8 cells. Furthermore, KRT8 overexpression led to increase in p‐smad2/3 levels and TGFβ dependent signaling events. KRT8 expression in GC was related to tumor clinical stage and worse survival. Kaplan–Meier analysis proved that KRT8 was associated with overall survival of patients with GC that patients with high KRT8 expression tend to have unfavorable outcome. Moreover, Cox's proportional hazards analysis showed that high KRT8 expression was a prognostic marker of poor outcome. These results provided that KRT8 expression may therefore be a biomarker or potential therapeutic target to identify patients with worse survival.