Enhanced PPAR-gamma expression may correlate with the development of Barrett's esophagus and esophageal adenocarcinoma

PPAR-gamma is known to have a growth-suppressive effect in different cancers. In this study, we investigated the role of PPAR-gamma in the development of Barrett's esophagus (BE) and esophageal adenocarcinoma (EA). We used immunohistochemistry and real-time PCR to analyze differences in PPAR-gamma protein and mRNA expression levels in samples of normal esophageal squamous epithelium (n = 75), BE (n = 50), and EA (n = 25). Immunoreactivity with antibodies against PPAR-gamma was confined to the nuclei of goblet cells and surface glandular epithelium in BE samples. We found significantly lower levels of expression of PPAR-gamma protein (p < 0.01) in normal esophageal squamous epithelium when compared to BE and EA samples. PPAR-gamma protein levels showed an increasing trend from normal esophageal squamous epithelium < BE samples < EA samples (p < 0.01). PPAR-gamma mRNA expression levels in BE and EA samples were 5.9130-fold (p < 0.01) and 2.0314-fold (p < 0.01) higher than that of normal esophageal squamous epithelium, respectively. There was a trend towards increased expression of PPAR-gamma with decreasing levels of differentiation. Increased PPAR-gamma expression may play an important role in the development and progression from normal cells to BE and EA.     

The antiapoptotic effect of IL-6 autocrine loop in a cellular model of advanced prostate cancer is mediated by Mcl-1

Levels of the proinflammatory cytokine interleukin-6 (IL-6) are increased in therapy-resistant prostate cancer. IL-6 has been considered a positive growth factor in late-stage prostate cancer cells and a potential target for therapeutic interference. Effects of inhibition of IL-6 on cell survival were studied in LNCaP-IL6+ cells, a model system for advanced prostate cancer, which produce IL-6. We show that the autocrine IL-6 loop is responsible for resistance to apoptosis and increased cellular levels of myeloid cell leukemia-1 (Mcl-1) protein, an antiapoptotic member of the Bcl-2 family. Treatment of cells with a chimeric anti-IL-6 antibody (CNTO 328) led to the induction of apoptosis and downregulation of Mcl-1 protein levels. Specific knockdown of Mcl-1 gene expression by small interfering RNA also yielded an increase in apoptosis of LNCaP-IL-6+ cells. Vice versa, inactivation of IL-6 autocrine loop had no influence on apoptosis levels in the absence of Mcl-1, thus suggesting this molecule as a mediator of the survival action of IL-6. Mcl-1 protein regulation by the endogenous cytokine directly involved the extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase pathway. Our data support the concept of anti-IL-6 targeted therapy in therapy-resistant prostate cancer.     

Transcriptional analyses of Barrett's metaplasia and normal upper GI mucosae

Over the last two decades, the incidence of esophageal adenocarcinoma (EA) has increased dramatically in the US and Western Europe. It has been shown that EAs evolve from premalignant Barrett's esophagus (BE) tissue by a process of clonal expansion and evolution. However, the molecular phenotype of the premalignant metaplasia, and its relationship to those of the normal upper gastrointestinal (GI) mucosae, including gastric, duodenal, and squamous epithelium of the esophagus, has not been systematically characterized. Therefore, we used oligonucleotide-based microarrays to characterize gene expression profiles in each of these tissues. The similarity of BE to each of the normal tissues was compared using a series of computational approaches. Our analyses included esophageal squamous epithelium, which is present at the same anatomic site and exposed to similar conditions as Barrett's epithelium, duodenum that shares morphologic similarity to Barrett's epithelium, and adjacent gastric epithelium. There was a clear distinction among the expression profiles of gastric, duodenal, and squamous epithelium whereas the BE profiles showed considerable overlap with normal tissues. Furthermore, we identified clusters of genes that are specific to each of the tissues, to the Barrett's metaplastic epithelia, and a cluster of genes that was distinct between squamous and non-squamous epithelia.     

Multifocal heterogeneity in villin and Ep-CAM expression in Barrett's esophagus

Barrett's esophagus (BE) is a metaplastic change of the squamous esophageal epithelium to columnar gastric or intestinal-like epithelium. BE is associated with long-standing gastroesophageal reflux disease and carries an increased risk for dysplasia and adenocarcinoma. Little if any is known regarding the differentiation state of esophageal metaplasia and its relationship to carcinogenesis. In this study, we investigated the potential of villin, a cytoskeletal protein, and Ep-CAM, a glandular epithelial glycoprotein, to serve as markers for enterocytic differentiation in BE at the molecular level. Endoscopic mucosal biopsy samples of normal esophagus, BE, stomach and duodenum were collected from 23 patients with BE. Biopsies were analyzed for villin and Ep-CAM expression by immunoblotting, and in some cases for the presence of microvilli by electron microscopy. By mapping of BE segments in 6 patients, correlations were also made between the histologic evidence of metaplasia and villin expression. Villin was uniformly expressed in all duodenal samples but was not detected in normal esophagus and stomach. In BE biopsies, villin expression was limited to the subset of patients whose adjacent biopsies showed microvilli by electron microscopy. In several patients studied, however, the expression of villin and the epithelial glycoprotein Ep-CAM differed among various regions of esophageal metaplasia within the same patient. Mapping studies failed to reveal any correlation among histologic evidence of metaplasia, dysplasia and villin expression and confirmed the multifocal heterogeneity of villin expression in BE. Preliminary data of 4 adenocarcinoma patients studied showed that villin expression was absent in 3 and very low in 1 patient. Ep-CAM was highly expressed in all adenocarcinoma patients. Our results show that BE represents a complex epithelium with significant heterogeneity in antigen expression and ultrastructural morphologic features. This molecular heterogeneity supports the presence of different stages of differentiation within the same epithelium. © 1996 Wiley-Liss, Inc.     

COX-2在Barrett食管与食管腺癌发病中的意义

目的：研究环氧化酶（COX-2）在Barrett食管（BE）及食管腺癌（EA）中的表达，探讨BE及EA的发病机制。方法：采用免疫组化染色及real—timePCR检测正常食管上皮、BE粘膜及EA标本中COX-2的蛋白及mRNA表达情况。结果：COX-2蛋白在正常鳞状上皮中几乎不表达，而在BE中呈轻中度阳性表达，在EA中呈弥漫强阳性表达，三者之间差异显著（P〈0．01），且呈线性趋势（r=0．810，P〈0．01）。COX-2mRNA在BE及EA中表达均增强，其表达率分别为正常鳞状上皮的1．3728倍（P〈0．01）和1．8312倍（P〈0．01）。结论：COX-2在BE及EA中表达升高，提示其表达的上调可能在BE及EA的发生发展中起重要作用。     

Mcl-1 regulates survival and sensitivity to diverse apoptotic stimuli in human non-small cell lung cancer cells

Overexpression of anti-apoptotic Bcl-2 family members and deregulation of the pathways that regulate pro-apoptotic family members have been observed in non-small cell lung cancers (NSCLC). Previous reports have identified both Bcl-2 and Bcl-x(L) proteins as survival factors in lung cancer cells since reductions in these proteins can induce apoptosis and sensitize lung cancer cells to apoptosis induced by chemotherapy agents. Myeloid cell leukemia-1 (Mcl-1), another member of the Bcl-2 family, has been found to be a critical survival factor in hematopoietic cells, yet little data exists for a role of Mcl-1 in human lung cancers. We used NSCLC cell lines to explore how Mcl-1 levels affect lung cancer cell survival and studied tumors from patients to determine expression patterns of Mcl-1. NSCLC cells express abundant Mcl-1 protein and depletion of Mcl-1 levels by antisense Mcl-1 oligonucleotides induces apoptosis in A549 and H1299 lung cancer cells. Reduction in Mcl-1 levels can sensitize lung cancer cells to apoptosis induced by cytotoxic agents as well as by ionizing radiation. Lung cancer cells overexpressing Mcl-1 are less sensitive to apoptosis induced by chemotherapeutic agents, ZD1839 (an inhibitor of EGFR tyrosine kinase) and Bcl-2 or Bcl-x(L) antisense oligonucleotides. We find that epidermal growth factor (EGF) can enhance Mcl-1 protein levels in an ERK-dependent manner. Signal transduction agents that reduce Mcl-1 levels correlated with their individual ability to induce apoptosis in lung cancer cells. Finally, NSCLC tumors taken directly from patients have elevated levels of Mcl-1 protein compared with normal adjacent lung tissue. Therefore, agents that target Mcl-1 can induce apoptosis and sensitize cells to apoptosis induced by cytotoxic agents. Mcl-1 protein is overexpressed in a subset of human NSCLC and enhanced levels of Mcl-1 may protect lung cancer cells from death induced by a variety of pro-apoptotic stimuli.     

Elevated interleukin-6 during ethanol consumption acts as a potential endogenous protective cytokine against ethanol-induced apoptosis in the liver: involvement of induction of Bcl-2 and Bcl-x(L) proteins.

Elevation of serum interleukin-6 (IL-6) levels is always associated with alcoholic liver disease (ALD), but the significance of such elevation is not clear. Here we show that chronic ethanol consumption induces significant apoptosis in the liver of IL-6 (-/-) mice but not IL-6 (+/+) mice. IL-6 (-/-) hepatocytes are more susceptible to ethanol- and tumor necrosis factor alpha- (TNFalpha-) induced apoptotic killing, which can be corrected by IL-6. Expression of both anti-apoptotic (such as Bcl-2 and Bcl-x(L)) and proapoptotic (such as Bax) proteins is markedly elevated in the liver of human ALD and chronically ethanol-fed IL-6 (+/+) mice. On the contrary, induction of Bcl-2 and Bcl-x(L) is not observed in the liver of chronically ethanol-fed IL-6 (-/-) mice, whereas expression of Bax protein remains elevated. Injection of IL-6 markedly induces expression of Bcl-2 and Bcl-x(L) but not Bax in the liver. Finally, high concentrations of ethanol inhibit IL-6-activated anti-apoptotic signal, but increasing the concentrations of IL-6 is able to overcome such inhibitory effect. These findings suggest that elevated serum IL-6 levels in ALD may overcome the inhibitory effect of ethanol on IL-6-mediated anti-apoptotic signals and prevent alcohol-induced hepatic apoptosis by induction of Bcl-2 and Bcl-x(L).     

Expression of cyclin E in dysplasia, carcinoma, and nonmalignant lesions of Barrett esophagus

BACKGROUND: Barrett esophagus (BE) is a condition in which the normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. BE is a premalignant lesion because it is the initiating factor in a metaplasia-dysplasia-carcinoma sequence. METHODS: Expression of the proliferation-associated molecule cyclin E was immunohistochemically determined in metaplastic specialized epithelium (SE; n = 24), low grade dysplasia (LGD; n = 21), high grade dysplasia (HGD; n = 17), and invasive adenocarcinoma (CA; n = 35) from 36 esophagectomy specimens. In addition, endoscopically obtained samples of SE with minimal inflammatory changes (n = 11) and SE adjacent to erosions or ulcerations were tested for cyclin E expression. RESULTS: In the surgical specimens, expression of cyclin E was found in 0 of 24 SE (0%), 2 of 21 LGD (9.5%), 3 of 17 HGD (17.6%), and 5 of 35 CA (14. 3%). In the biopsy specimens, expression of cyclin E was found in all samples adjacent to erosions or ulcerations, whereas SE with minimal inflammatory changes was invariably negative for cyclin E. CONCLUSIONS: Accumulation of cyclin E can be found by means of immunohistochemistry in premalignant and malignant lesions in BE as well as in regenerative metaplastic epithelium. The determination of cyclin E expression is therefore not useful in the identification of BE patients with an increased risk for the development of carcinoma.     

Flavopiridol down-regulates antiapoptotic proteins and sensitizes human breast cancer cells to epothilone B-induced apoptosis

The molecular mechanisms underlying the cell cycle growth-inhibitory and apoptotic effects of flavopiridol (FP) were determined in human breast cancer cells. Treatment with FP caused accumulation in the G(1) phase of the cell cycle and induced apoptosis of SKBR-3 and MB-468 cells. This was associated with down-regulation of the levels of cyclins D1 and B1, as well as with inhibition of cyclin-dependent kinase (cdk) 1, cdk2, and cdk4. FP-induced apoptosis was accompanied by a conformational change and mitochondrial localization of Bax. This resulted in the accumulations of cytochrome c, Smac, and Omi/HtrA2 in the cytosol and induced the poly(ADP-ribose) polymerase cleavage activity of caspase-3. Treatment with FP also attenuated the mRNA and protein levels of XIAP, cIAP-2, Mcl-1, Bcl-x(L), and survivin. In MB-468 cells with overexpression of Bcl-2 (468/Bcl-2), FP-induced Bax conformational change and apoptosis were inhibited, whereas the FP-mediated decline in the levels of IAP proteins, Mcl-11 and Bcl-x(L) remained unaltered. The effects of cotreatment with FP and the nontaxane tubulin-polymerizing agent epothilone (Epo) B were also determined in MB-468 cells. Sequential treatment with Epo B followed by FP induced significantly more apoptosis of MB-468 cells than treatment with the reverse sequence of FP followed by Epo B or treatment with either agent alone (P < 0.05). Treatment with Epo B followed by FP induced more Bax conformational change and was associated with a greater decline in the levels of XIAP, cIAP-2, Mcl-1, and Bcl-x(L). However, MB-468/Bcl-2 cells remained relatively resistant to Epo B followed by FP. Taken together, these findings suggest that the superior sequence-dependent anti-breast cancer activity of Epo B followed by FP may be due to FP-induced Bax conformational change and down-regulation of the antiapoptotic IAP, Bcl-x(L), and Mcl-1 proteins, but this treatment may not overcome the resistance to apoptosis of breast cancer cells conferred by overexpression of Bcl-2.     

Knockdown of p53 levels in human keratinocytes accelerates Mcl-1 and Bcl-x(L) reduction thereby enhancing UV-light induced apoptosis

Ultraviolet (UV) light exposure is a common cause of epithelial-derived skin cancers, and the epidermal response to UV-light has been extensively studied using both mouse models and cultured human keratinocytes (KCs). Elimination of cells with UV-induced DNA damage via apoptosis provides a powerful mechanism to minimize retention or expansion of genetically abnormal cells. This cell editing function has largely been ascribed to the biological role of the p53 tumor suppressor gene, as mutations or deletions involving p53 have been linked to skin cancer development. Rather than introducing mutations, or using cells with complete loss of wild-type p53, we used an siRNA-based approach to knockdown, but not eliminate, p53 levels in primary cultures of human KCs followed by UV-irradiation. Surprisingly, when p53 levels were reduced by 50-80% the apoptosis induced by exposure to UV-light was accelerated and markedly enhanced (two- to three- fold) compared to control siRNA treated KCs. The p53 siRNA treated KCs were characterized by elevated E2F-1 levels accompanied by accelerated elimination of the Mcl-1 and Bcl-x(L) antiapoptotic proteins, as well as enhanced Bax oligomerization. Forced overexpression of either Mcl-1 or Bcl-x(L) reduced the UV-light enhanced apoptotic response in p53 siRNA treated KCs. We conclude that p53 not only can provide proapoptotic signals but also regulates a survival pathway influencing Mcl-1 and Bcl-x(L) levels. This overlooked survival function of p53 may explain previous paradoxical responses noted by investigators using p53 heterozygous and knockout mouse models, and opens up the possibility that not all liaisons within the cell involving p53 necessarily represent fatal attractions.     

The anti-apoptotic role of interleukin-6 in human cervical cancer is mediated by up-regulation of Mcl-1 through a PI 3-K/Akt pathway

Interleukin-6 (IL-6), a multifunctional cytokine, has recently been implicated in human cervical cancer, though the mechanism remains elusive. This study demonstrates that the anti-apoptotic protein Mcl-1 and IL-6 was concomitantly expressed in human cervical cancer tissues and cell lines, but not in normal cervix tissues. Upon IL-6 treatment, Mcl-1, but not other Bcl-2 family members, was rapidly up-regulated peaking at 4-8 h in human cervical cancer C33A cells. Supporting this observation, using anti-IL-6 or anti-IL-6 receptor antibody to interrupt the IL-6 autocrine loop in SiHa cells significantly reduced cellular level of Mcl-1. This study hypothesizes that the expression of Mcl-1 in cervical cancer cells is regulated by IL-6. The matter of which signaling pathways transduced by IL-6 is responsible for the Mcl-1 up-regulation is further investigated herein. Blocking the STAT3 or MAPK pathway with dominant-negative mutant STAT3F or the MEK inhibitor PD98059 failed to inhibit IL-6-mediated Mcl-1 expression. Meanwhile, the IL-6-induced Mcl-1 up-regulation was effectively abolished by treatment with PI 3-K inhibitors, LY294002. Additionally, overexpression of dominant-negative (dn) Akt in C33A cells could inhibit the IL-6-induced increase of Mcl-1. Finally, overexpression of IL-6 in C33A cells caused a markable resistance to apoptosis induced by doxorubicin or cisplatin. Transient transfection of IL-6-overexpressed cells with a mcl-1 antisense vector, leading to the attenuation of their apoptosis-resistant activity. In conclusion, the data herein suggest that IL-6 regulated the mcl-1 expression via a PI 3-K/Akt-dependent pathway that may facilitate the oncogenesis of human cervical cancer by modulating the apoptosis threshold.     

Bile acid and inflammation activate gastric cardia stem cells in a mouse model of Barrett-like metaplasia

Esophageal adenocarcinoma (EAC) arises from Barrett esophagus (BE), intestinal-like columnar metaplasia linked to reflux esophagitis. In a transgenic mouse model of BE, esophageal overexpression of interleukin-1β phenocopies human pathology with evolution of esophagitis, Barrett-like metaplasia and EAC. Histopathology and gene signatures closely resembled human BE, with upregulation of TFF2, Bmp4, Cdx2, Notch1, and IL-6. The development of BE and EAC was accelerated by exposure to bile acids and/or nitrosamines, and inhibited by IL-6 deficiency. Lgr5(+) gastric cardia stem cells present in BE were able to lineage trace the early BE lesion. Our data suggest that BE and EAC arise from gastric progenitors due to a tumor-promoting IL-1β-IL-6 signaling cascade and Dll1-dependent Notch signaling.     

A pro-inflammatory genotype predisposes to Barrett's esophagus

INTRODUCTION: Severity of mucosal inflammation is shown to be associated with Barrett's esophagus (BE) development in animals. It has therefore been postulated that a strong pro-inflammatory host response predisposes to BE. AIM: To determine the impact of cytokine gene polymorphisms on the development of BE. METHODS: The multiplex SNaPshot method was used to determine interleukin (IL)-12B (A+1188C), IL-10 (C-592A, C-819T, A-1082G), IL-8 (A-251T), IL-6 (G-174C) and IL-2 (G-330T) gene polymorphisms in 255 patients with BE and 247 patients with reflux esophagitis (RE). RESULTS: The presence of the IL-12B C-allele, which is associated with increased IL-12p70 expression, was more frequently observed in BE than in RE patients [odds ratio (OR) 1.8; 95% confidence interval (CI) 1.2-2.7; P = 0.007). The risk of BE was increased in patients in whom the IL-12B C-allele coincided with a hiatal hernia (OR 2.9; 95% CI 1.32-6.58; P = 0.008). The IL-10(-1082) GG genotype, which is associated with higher IL-10 levels, was also associated with a decreased risk of BE when it was associated with the IL-12B C-allele, indicating IL-10-dependent down-regulation of IL-12p70 expression. A combination of the IL-12B AA genotype and the IL-10 AA or AG genotypes was associated with RE (OR 1.4; 95% CI 1.05-1.85; P = 0.011). CONCLUSION: A genetic profile predisposing to a strong pro-inflammatory host response, mediated by IL-12p70 and partially dependent on IL-10, is associated with BE. This risk further increases when this genotype coincides with a hiatal hernia, suggesting that exposure to gastroesophageal reflux in the presence of a pro-inflammatory genetic background is a driving force in the development of BE.