Overexpression of PrPc,combined with MGr1‐Ag/37LRP,is predictive of poor prognosis in gastric cancer

Prion protein (PrPc) has been previously reported to be involved in gastric cancer (GC) development and progression. However, the association between expression of PrPc and GC prognosis is yet poorly characterized. In the present study, the expressions of PrPc and MGr1‐Ag/37LRP, a protein interacting with PrPc, were detected using the tissue microarray technique and immunohistochemical method to compare clinicopathological parameters of 238 GC patients. We found that the expressions of PrPc and MGr1‐Ag/37LRP were upregulated in GC lesions compared with their expressions in adjacent noncancerous tissues (p < 0.01). High expression of PrPc was detected in 37.39% (89/238) of GC patients and positively correlated with the expression of MGr1‐Ag/37LRP (r = 0.532, p < 0.001). PrPc expression was associated with a number of clinicopathological parameters including depth of invasion and lymph node metastasis of the tumor (p < 0.001). High expression of PrPc brought a poorer prognosis than low PrPc expression. Moreover, GC patients with high level of PrPc and high level of MGr1‐Ag/37LRP had the poorest prognosis. Multivariate survival analysis suggested that, along with other parameters, combined expression of PrPc and MGr1‐Ag/37LRP was independent prognostic factors for GC patients. These data indicates that overexpression of PrPc, combined with MGr1‐Ag/37LRP, is predictive of poor prognosis in GC and thereby could be used to guide the clinical decision.     

MDR1启动子/荧光素酶质粒的构建及其在朊蛋白高表达胃癌细胞中的活性检测

目的:构建含MDR1基因启动子的荧光素酶报告基因质粒,并检测其在朊蛋白高表达胃癌细胞系中的活性表达。方法:PCR克隆人MDRl基因启动子片段,通过亚克隆将启动子分别插入到pMD18-T载体和荧光素酶报告基因pGL3-Enhancer载体中,建立含MDR1启动子的荧光素酶报告基因质粒pGL-MDR1,并经测序及酶切确定扩增序列;脂质体基因转染法将pGL-MDR1转染入朊蛋白高表达胃癌细胞系SGC7901-PrP,并测定其荧光素酶活性。结果:PCR克隆出MDR1启动子经DNA测序证实序列正确,pGL-MDR1转染入朊蛋白高表达胃癌细胞系的荧光素酶活性,较转染入pcDNA3.1空载体细胞系相比升高3~5倍。结论:成功构建含MDRl启动子的荧光素酶报告基因质粒;上调朊蛋白表达可激活MDR1的转录活性。     

Induction of cellular prion protein (PrPc) under hypoxia inhibits apoptosis caused by TRAIL treatment

Hypoxia decreases cytotoxic responses to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein. Cellular prion protein (PrPc) is regulated by HIF-1α in neurons. We hypothesized that PrPc is involved in hypoxia-mediated resistance to TRAIL-induced apoptosis. We found that hypoxia induced PrPc protein and inhibited TRAIL-induced apoptosis. Thus silencing of PrPc increased TRAIL-induced apoptosis under hypoxia. Overexpression of PrPc protein using an adenoviral vector inhibited TRAIL-induced apoptosis. In xenograft model in vivo, shPrPc transfected cells were more sensitive to TRAIL-induced apoptosis than in shMock transfected cells. Molecular chemo-therapy approaches based on the regulation of PrPc expression need to address anti-tumor function of TRAIL under hypoxia. Molecular chemo-therapy approaches based on the regulation of PrPc expression need to address anti-tumor function of TRAIL under hypoxia.     

Pharmacological inhibition of Bcl-2 family members reactivates TRAIL-induced apoptosis in malignant glioma

The major aim of this study was to develop novel therapeutic approaches to potentiate and reactivate apoptosis induced by TNF-Related Apoptosis Inducing Ligand (TRAIL) in malignant glioma. Analysis of five glioma cell lines (U87, U251, U373, MZ-54 and MZ-18) indicated that only two of the cell lines were sensitive to apoptosis induced by TRAIL alone. TRAIL resistance was not correlated to expression levels of the death receptors DR4 and DR5 or the decoy receptors DcR1 and DcR2, suggesting that it was mediated by inactivation of TRAIL-induced downstream signalling. Activation of the BH3 only protein Bid and subsequent activation of the mitochondrial apoptosis pathway are known to play a pivotal role in TRAIL-induced apoptosis. Since this process is blocked by overexpression of anti-apoptotic Bcl-2 family members, we analyzed the therapeutic potential of BH3 mimetics in potentiating TRAIL-induced apoptosis. Treatment with TRAIL in combination with the specific Bcl-2 inhibitor HA14-1 and the Bcl-2/Bcl-xL inhibitor BH3I-2′ potently enhanced apoptosis in TRAIL-sensitive U87 cells in a dose-dependent fashion. TRAIL-induced apoptosis was significantly reactivated by HA14-1 and BH3I-2′ in one (U343) and two (MZ-54 and MZ-18) of three investigated TRAIL-insensitive cell lines, respectively. Knockdown of the anti-apoptotic Bcl-2 family member Mcl-1 by RNA interference had no additional effect on apoptosis induced by TRAIL and HA14-1 in U87 and U343 cells. Our data indicate that Bcl-2 and Bcl-xL play fundamental roles in TRAIL resistance of malignant glioma and suggest that using TRAIL or agonistic TRAIL receptor antibodies in combination with BH3 mimetics may represent a promising approach to reactivate apoptosis in therapy-resistant high grade gliomas.     

Overexpression and significance of prion protein in gastric cancer and multidrug-resistant gastric carcinoma cell line SGC7901/ADR

In our previous work, cellular prion protein (PrPc) was identified as an upregulated gene in adriamycin-resistant gastric carcinoma cell line SGC7901/ADR compared to its parental cell line SGC7901. Here we investigate the expression of PrPc in gastric cancer and whether it was involved in multidrug resistance (MDR) of gastric cancer. We demonstrated that PrPc was ubiquitously expressed in gastric cancer cell lines and tissues. PrPc conferred resistance of both P-glycoprotein (P-gp)-related and P-gp-nonrelated drugs on SGC7901, which was accompanied by decreased accumulation and increased releasing amount of adriamycin in PrPc-overexpressing cell line. Inhibition of PrPc expression by antisense or RNAi technology could partially reverse multidrug-resistant phenotype of SGC7901/ADR. PrPc significantly upregulated the expression of the classical MDR-related molecule P-gp but not multidrug resistance associated protein and glutathione S-transferase pi. The PrPc-induced MDR could be partially reversed by P-gp inhibitor verapamil. PrPc could also suppress adriamycin-induced apoptosis and alter the expression of Bcl-2 and Bax, which might be another pathway contributing to PrPc-related MDR. The further study of the biological functions of PrPc may be helpful for understanding the mechanisms of occurrence and development of clinical gastric carcinoma and PrPc-related MDR and developing possible strategies to treat gastric cancer.     

Constitutional activation of IL-6-mediated JAK/STAT pathway through hypermethylation of SOCS-1 in human gastric cancer cell line

The interleukin-mediated Janus kinase (JAK)/STAT pathway plays a crucial role in carcinogenesis. Recently, increased STAT3 activity was found in hepatocellular carcinoma and multiple myeloma in which there was silencing of SOCS-1 (suppressor of cytokine signalling-1) by gene promoter hypermethylation. We investigated the expression level of interleukin-6 (IL-6) and SOCS-1 in gastric cancer cell lines. Expression of SOCS-1 correlated with IL-6 level in most of the cell lines, except for AGS cells in which SOCS-1 was absent despite a high level of IL-6 production. Methylation analysis by methylation-specific polymerase chain reaction and bisulphite sequencing revealed that CpG island of SOCS-1 was densely methylated in AGS cells. Demethylation treatment by 5'aza-deoxycytidine restored SOCS-1 expression and also suppressed constitutive STAT3 phosphorylation in AGS cells. Moreover, methylation of SOCS-1 was detected in 27.5% (11 of 40) of primary gastric tumours samples, 10% (one of 10) of adjacent noncancer tissues but not in any (zero of nine) normal gastric mucosa. Methylation of SOCS-1 also correlated with the loss of mRNA expression in some primary gastric cancers. In conclusion, this is the first report to demonstrate that hypermethylation of SOCS-1 led to gene silencing in gastric cancer cell line and primary tumour samples. Downregulation of SOCS-1 cooperates with IL-6 in the activation of JAK/STAT pathway in gastric cancer.     

Caveolins in the development and diseases of musculoskeletal system

Caveolins, essential scaffold proteins of caveolae, have emerged as versatile molecules that can influence numerous signaling pathways and disease processes. This brief review is focused on the role of caveolins in the physiology and pathology of musculoskeletal system and will discuss the key features of caveolins as related to differentiation and diseases of bone and muscle cells.     

Molecular biology in breast cancer: intrinsic subtypes and signaling pathways

The last decade has brought a breakthrough in the knowledge of the biology of breast cancer. The technological development, and in particular the high throughput technologies, have allowed researchers to inquire more deeply into the nature of the disease through the comparative study of large numbers of samples. The classification of breast cancer by traditional parameters has been joined by rankings based on gene expression. Among the most popular platforms are MammaPrint®, Oncotype DX® the wound-response model, the rate of two genes model, the genomic grade index and the intrinsic subtype model. The latter one provides the amplest biological information and allows for the classification of breast cancer into six intrinsic subtypes: luminal A, luminal B, HER2-enriched, basal-like, normal breast and claudin-low. These new classifications are not yet fully applicable to clinical practice not only because they have not been standardized, but also because they entail a substantial economic outlay. Nevertheless, they have provided valuable information on tumor biology that has led to a better understanding of the signaling pathways governing the processes of formation, maintenance and expansion of the tumors. Researchers now know more about the HER2, estrogen receptor, IGF1R, PI3K/AKT, mTOR, AMPK and angiogenesis pathways which has allowed for the development of new targeted therapeutics now being tested in ongoing clinical trials.     

PFKFB3在胃癌中的表达及对胃癌细胞生长和凋亡的影响研究

背景与目的:6-磷酸果糖激酶-2同工酶3(6-phosphofructo-2-kinase 3,PFKFB3)与肿瘤的发生、发展密切相关,且对肿瘤细胞的生物学行为具有重要的调节作用。分析PFKFB3在胃癌组织及癌旁组织中的表达,并观察其对胃癌细胞生长和凋亡的作用及机制。方法:采用TCGA数据库分析72例在南昌大学第二附属医院及第三附属医院经外科手术切除的新鲜胃癌标本及其相应的癌旁组织中PFKFB3的表达,并分析PFKFB3的表达与胃癌预后的关系。进一步通过实时荧光定量聚合酶链反应(real-time fluorescence quantitative polymerase chain reaction,RTFQ-PCR)、蛋白质印迹法(Western blot)及免疫组织化学法分析胃癌组织标本及癌旁组织标本中PFKFB3的表达。shNC及shPFKFB3质粒转染至胃癌细胞中,采用RTFQ-PCR和Western blot验证转染效率。分别通过细胞计数试剂盒-8(cell counting kit-8,CCK-8)实验、EdU实验、流式细胞术和Western blot分析PFKFB3下调后对胃癌细胞的增殖能力、细胞周期变化和细胞凋亡的影响。最后采用Western blot分析PFKFB3影响胃癌细胞生长的机制。结果:TCGA数据库分析显示,胃癌组织中PFKFB3的表达明显高于癌旁组织(P<0.05),且PFKFB3高表达与胃癌患者较差的预后密切相关。另外,RTFQ-PCR、Western blot及免疫组织化学检测也同样证实PFKFB3在胃癌组织中高表达(P<0.01),且PFKFB3的表达升高与淋巴结转移及TNM分期密切相关(P<0.05)。沉默胃癌细胞中PFKFB3的表达后,其生长能力明显减弱(P<0.01),胃癌细胞凋亡比例增加(P<0.01),细胞周期G1期阻滞(P<0.01)。PFKFB3通过激活磷酸化磷脂酰肌醇3-激酶(phosphoinositide 3-kinase,PI3K)/蛋白激酶B(protein kinase B,AKT)信号通路而调控胃癌细胞的生长。结论:PFKFB3在胃癌组织中高表达,且与患者预后密切相关,沉默PFKFB3的表达后抑制胃癌细胞的生长并促进其凋亡,PFKFB3可能是胃癌靶向治疗的潜在生物标志物。     

PI3K／Akt途径在朊蛋白介导胃癌耐药中的作用研究

目的：探讨P13K／Akt途径在朊蛋白（PrPc）介导胃癌耐药中的作用。方法：脂质体基因转染法建立高表达PrPc的胃癌细胞亚系。Western印迹检测转染细胞中Akt蛋白的表达。噻唑蓝（MTT）比色法测定单独或联用P13K抑制剂LY294002时转染细胞对化疗药物的敏感性。流式细胞仪检测单独或联用LY294002时转染细胞内阿霉素蓄积和潴留。结果：将PrPc正义载体pcDNA—PrP转入SGC7901,成功建立PrPc高表达胃癌细胞亚系并命名为PS;空载体转染细胞命名为BS。Western—Blot显示磷酸化Akt在PS中的表达较Bs及SGC7901增高,而三者的总Akt则无差别。未经LY294002处理时,在阿霉素或长春新碱的作用下,PS的存活率分别为91．4％±3．4％和89．4％±3．8％,较BS（79．2％±4．3％和75．9％±2．1％）明显增高（均）,PS细胞内阿霉素蓄积量和潴留量分别为4．4±0．3和4．2±0．4,明显低于BS（8．2±0．5和8．0±0．3）（均）;当联合LY294002处理后,PS在两种药物作用下的存活率均随着LY294002浓度的增加逐渐降低,并均在LY294002为30tLmol／L时接近BS（均）,PS细胞内阿霉素蓄积量和潴留量逐渐增高,并均在LY294002为30μmol／L时接近BS（均）。结论：PrPc介导的胃癌耐药与P13K／Akt途径活性密切相关,抑制P13K／Akt途径活性可逆转PrPc介导的胃癌耐药。     

The activation of ERK1/2 via a tyrosine kinase pathway attenuates trail-induced apoptosis in HeLa cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves as an extracellular signal that triggers apoptosis in tumor cells. To characterize the molecular events involved in TRAIL-induced apoptotic signaling, we investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) in HeLa cell death. Here we show that TRAIL-activated ERK1/2 through a tyrosine kinase-dependent pathway, subsequently elevated anti-apoptotic Bcl-2 protein levels. ERK1/2 inhibition with PD98059 promoted apoptotic cell death through the downregulation of ERK1/2 activity and Bcl-2 protein levels. Moreover, tyrosine kinase inhibition with Genistein in TRAIL-induced apoptosis effectively attenuated ERK1/2 activity and enhanced apoptotic cell death. Taken together, our results indicate that ERK1/2 activation via tyrosine kinase pathway plays a protective role as the cellular defense mechanism through the upregulation of Bcl-2 protein levels in TRAIL-induced apoptosis.     

LncRNA DLEU2对胃癌细胞增殖、凋亡和PI3K/Akt信号通路的影响

目的探讨长链非编码RNA淋巴细胞白血病缺失基因2(DLEU2)对胃癌细胞增殖、凋亡和磷脂酰肌醇3激酶(PI3K)/蛋白激酶B(Akt)信号通路的影响。方法通过GEPIA在线分析来自TCGA数据库和GTEx项目的胃癌组织DLEU2水平,采用实时定量PCR(QPCR)检测正常胃黏膜上皮GES-1细胞和胃癌BGC-823细胞的DLEU2水平;脂质体法将3条靶向DLEU2的小干扰RNA(si-DLEU2-1、si-DLEU2-2和si-DLEU2-3)转染至BGC-823细胞中,筛选最佳si-DLEU2干扰序列进行实验。体外常规培养BGC-823细胞并分为转染si-DLEU2的干扰组、转染无义siRNA序列的阴性对照(NC)组和未转染的空白对照(Blank)组,采用MTT比色法和AnnexinⅤ-FITC/PI双染流式细胞术检测细胞的增殖活力和凋亡率,QPCR和Western blotting检测凋亡相关因子Bcl-2、Bax和caspase-3的水平,Western blotting检测磷酸化的PI3K调节亚基p85(p-p85)和Akt(p-Akt)水平。结果GEPIA在线分析显示胃癌组织的DLEU2水平高于正常组织(P<0.05);QPCR结果显示BGC-823细胞的DLEU2水平高于GES-1细胞(P<0.05),且3条si-DLEU2序列转染后,BGC-823细胞的DLEU2水平均降低(P<0.05),其中si-DLEU2-3序列的效果最佳,故选取si-DLEU2-3序列进行后续实验;干扰组的DLEU2水平及转染24、48 h后的增殖活力均低于Blank组和NC组(P<0.05)。干扰组的凋亡率为(21.529±1.320)%,高于Blank组的(9.032±0.536)%和NC组的(8.641±0.365)%(P<0.05)。与Blank组和NC组相比,干扰组的Bcl-2、p-p85和p-Akt水平降低,而Bax和caspase-3水平均升高(P<0.05)。Blank组和NC组上述指标的差异无统计学意义(P>0.05)。结论DLEU2在胃癌组织和细胞中均升高且发挥促癌作用,可能通过激活PI3K/Akt信号通路来增强细胞增殖能力并抑制凋亡,有望成为胃癌治疗的新靶点。     

miR-101-3p在胃癌中的表达及其靶向STC-1基因调控PI3K/AKT信号通路对癌细胞侵袭转移和血管生成的影响

目的 探究miR-101-3p在胃癌中的表达及其靶向STC-1基因调控PI3K/AKT信号通路对癌细胞侵袭转移、血管生成的作用机制。方法 qRT-PCR检测胃癌组织及BGC-823细胞中miR-101-3p和STC-1 mRNA的表达,并分析miR-101-3p表达与患者临床病理因素的关系;通过LipofectamineTM 2000将miRNA模拟物和质粒分别或者联合转染细胞;TargetScanHuman预测及双荧光素酶报告验证miR-101-3p对STC-1的靶向调控关系;划痕实验、Transwell小室实验、Matrigel体外成管实验及Westernblot检测验证miR-101-3p靶向STC-1基因对癌细胞的侵袭转移和血管生成的影响及可能的机制,并通过裸鼠致瘤实验检测移植瘤的发展。结果 胃癌组织中STC-1的表达水平高于正常组织。与正常胃组织和GES-1细胞相比,胃癌组织和BGC-823细胞中miR-101-3p下调,STC-1 mRNA上调,且miR-101-3p水平与STC-1水平负相关,miR-101-3p水平与肿瘤分化程度、TNM分期、淋巴结转移显著相关（P<0.05）;过表达miR-101-3p可抑制STC-1的表达,下调p-PI3K/PI3K、p-AKT/AKT、MMP-2、MMP-9、VEGF、Ang2水平,抑制肿瘤细胞的侵袭转移和血管生成,降低移植瘤体积和重量（P<0.05）。结论 miR-101-3p在胃癌中表达下调,能够靶向STC-1基因调控PI3K/AKT信号通路抑制胃癌细胞BGC-823的侵袭转移和血管生成及体内移植瘤的进展。     

Fibulin 1 is downregulated through promoter hypermethylation in gastric cancer

Tumour suppressor genes (TSGs) were frequently inactivated through promoter hypermethylation in gastric carcinoma as well as pre-malignant gastric lesions, suggesting that promoter hypermethylation can be used as a marker to define novel TSGs and also biomarkers for early detection of gastric cancer. In an effort to search for such genes aberrantly methylated in gastric cancer development, fibulin 1 (FBLN1) was found as a candidate TSG epigenetically downregulated in gastric cancer. FBLN1 expression was downregulated in all of gastric cancer cell lines used (100%, 7 out of 7) and the primary gastric carcinoma tissues (84%, 86 out of 102) and significantly restored after pharmacological demethylation. Hypermethylation of the FBLN1 promoter was frequently (71%, 5 out of 7) detected in gastric cancer cell lines and primary gastric carcinoma tissues. Ectopic expression of FBLN1 led to the growth inhibition of gastric cancer cells through the induction of apoptosis. In summary, FBLN1 was identified as a novel candidate TSG epigenetically downregulated in gastric cancer.     

Synergistic effects of acyclic retinoid and gemcitabine on growth inhibition in pancreatic cancer cells

Pancreatic cancer is a serious healthcare problem worldwide because of its high mortality. Gemcitabine, a DNA synthesis inhibitor, is the standard first-line treatment for advanced pancreatic cancer and is also expected as a key drug for the combination therapy of this malignancy. Retinoids, which are derivatives of vitamin A, exert anti-tumor effects in various types of human malignancies, including pancreatic cancer. This study examined whether combination therapy with gemcitabine and acyclic retinoid (ACR), a new synthetic retinoid, had enhanced anti-tumor efficacy in pancreatic cancer. ACR, 9-cis-retinoic acid and gemcitabine preferentially inhibited the growth of human pancreatic cancer cells (Panc-1 and KP-2) in comparison to PE normal human pancreatic epithelial cells. The combination of ACR plus gemcitabine synergistically inhibited the growth of Panc-1 cells. The combined treatment with these two agents also acted synergistically to induce apoptosis and to inhibit Ras activation in these cancer cells. In vivo, the combination therapy augmented tumor growth inhibition through the induction of apoptosis and inhibition of cell proliferation in tumor tissue. These results suggest that the combination of ACR plus gemcitabine may therefore be an effective regimen for the chemotherapy of pancreatic cancer.     

Phosphorylation of 4E-BP1 predicts sensitivity to everolimus in gastric cancer cells

We studied the effect of everolimus, an inhibitor of the mammalian target of rapamycin (mTOR) on human gastric cancer cell lines. Cell proliferation in 3 of 8 cell lines was effectively inhibited by everolimus. Basal phosphorylation level of 4E-BP1 (T37/46, T70) was significantly higher in everolimus-sensitive cells than in everolimus-resistant cells. In subcutaneous xenograft model, immunohistochemistry analysis revealed that everolimus-sensitive cells expressed high levels of phospho-4E-BP1 (T37/46). In conclusion, phosphorylation of 4E-BP1 may be a predictive biomarker of everolimus sensitivity in gastric cancer.     

沉默AFAP-1L2对胃癌MKN-28细胞的生物学影响

目的:探讨AFAP-1L2对胃癌MKN-28细胞的生物学影响。方法:siRNA干扰AFAP-1L2;CCK-8检测沉默AFAP-1L2后细胞的增殖情况;免疫荧光分析各组细胞的凋亡率;Transwell小室观察细胞的侵袭情况;Real time-PCR检测细胞中基因的表达情况。结果:siRNA有效干扰了AFAP-1L2的表达;沉默AFAP-1L2细胞组的细胞增殖明显受到抑制（P<0.05）;siRNA-AFAP-1L2组细胞的凋亡率与其他组比较,凋亡率增高;细胞的侵袭情况,沉默AFAP-1L2明显抑制了细胞的侵袭,与其他两组比较差异显著（P<0.05）;ERK1/2、p-ERK1/2和Bcl-2的表达水平,均是siRNA-AFAP-1L2细胞组低于其他两组（P<0.05）。结论:沉默AFAP-1L2抑制了胃癌MKN-28细胞的增殖,诱导细胞的凋亡,抑制了细胞的侵袭和抗凋亡基因的表达,AFAP-1L2可以通过ERK1/2途径发挥作用,为肿瘤的靶向治疗提供一定的理论依据。     

The BH3 mimetic S1 induces autophagy through ER stress and disruption of Bcl-2/Beclin 1 interaction in human glioma U251 cells

Previous results showed that a novel BH3 mimetic S1 could induce cell death in a wide range of cancer types in vitro through Bax/Bak-dependent apoptosis. We demonstrated that in addition to mitochondrial pathway apoptosis, endoplasmic reticulum (ER) stress-associated apoptosis was also induced by S1. Moreover, S1 can induce autophagy in U251 cells, which may occur through ER stress and disruption of the association of Bcl-2 and Beclin 1. Inhibition of autophagy by the autophagic inhibitors 3-methyladenine (3-MA) or chloroquine (CQ) increased S1-induced apoptosis. In conclusion, autophagy plays an important role in S1-induced U251 cell death.     

Helicobacter pylori bacteria alter the p53 stress response via Erk-HDM2 pathway

H. pylori infection is the strongest known risk factor for gastric cancer. Inhibition of host tumor suppressor mechanisms by the bacteria underlies the development of this disease. Among the tumor suppressors affected by H. pylori are p53 and E-cadherin, which inhibition has been shown to increase the risk of gastric cancer. In this report, we investigated the interaction between E-cadherin and p53 in H. pylori-infected cells. We found that downregulation of E-cadherin leads to cellular stress and activation of p53. In the setting of H. pylori infection, this mechanism, however, is disrupted. We found that although co-culture of gastric epithelial cells with H. pylori led to downregulation of E-cadherin and cellular stress, it resulted in inhibition of p53, which is mediated by intracellular Erk kinases and HDM2 protein induced by H. pylori. Experimental inhibition of HDM2/p53 interactions restored p53 activity, and decreased survival of infected cells. Collectively, our results revealed that regulation of p53 and E-cadherin is tightly linked through the p53 stress response mechanism that is inhibited by H. pylori via activation of Erk1/2-HDM2-p53 pathway leading to survival of damaged cells. This might be advantageous to the bacteria but may increase the cancer risk.     

Bcl-2:Beclin 1 complex: multiple, mechanisms regulating autophagy/apoptosis toggle switch

Cancer cells have developed novel mechanisms for evading chemotherapy-induced apoptosis and autophagy-associated cell death pathways. Upon the discovery that chemotherapeutics could target these cell death pathways in a manner that was not mutually exclusive, new discoveries about the interrelationship between these two pathways are emerging. Key proteins originally thought to be "autophagy-related proteins" are now found to be involved in either inducing or inhibiting apoptosis. Similarly, apoptosis inhibiting proteins can also block autophagy-associated cell death. One example is the complex formed by the autophagy protein, Beclin 1, and anti-apoptotic protein Bcl-2, which leads to inhibition of autophagy-associated cell death. Researchers have been investigating additional mechanisms that form/disrupt this complex in order to better design chemotherapeutics. This review will highlight the role Bcl-2 and Beclin 1 play in cancer development and drug resistance, as well as the role the Bcl-2:Beclin 1 complex in the switch between autophagy and apoptosis.