Constitutive activation of NF-κB in human hepatocellular carcinoma: Evidence of a cytoprotective role

Activation of nuclear factor-κB (NF-κB) can promote or inhibit apoptosis. Oxidative stress is an important mechanism by which certain anticancer drugs kill cancer cells, and is also one of the mechanisms that activate NF-κB. We therefore examined hepatic expression of the NF-κB monomer p65 in human hepatocellular carcinoma (HCC) tissue samples from eight patients and compared it with their respective samples of surrounding liver tissues. We also studied the effect of NF-κB inhibition in human HCC cells exposed to oxidative stress, by infecting HuH7 cells with a recombinant adenovirus carrying mutant IκBα (mIκBα). Cultured HuH7 cells were infected with mIκBα or β-galactosidase (β-Gal) for 24 hr followed by treatment with increasing concentrations of H2O2. Cytotoxicity, NF-κB translocation, NF-κB DNA binding, cell proliferation, and apoptosis were determined. The monomer p65 was overexpressed in six of eight human HCC tissues. In HuH7 cells, introduction of mIκBα potently inhibited the translocation, activation, and DNA binding of NF-κB. In control (β-Gal-infected) HuH7 cells, exposure to H2O2 produced a dose-dependent increase in apoptosis, regardless of NF-κB status. mIκBα- mediated inhibition of NF-κB activation sensitized HuH7 cells to H 2O2-induced inhibition of cell growth, and further promoted cell death. Addition of H2O2 (200-500 μM) to control or mIκBα-infected HuH7 cells enhanced caspase-3 activity and cleavage. Adenovirus-mediated transfer of mIκBα potently inhibits NF-κB activity in HuH7 cells, and this enhances oxidative stress-induced cell killing. © Mary Ann Liebert, Inc.published_or_final_versio

Constitutive activation of NF-κB in human hepatocellular carcinoma: Evidence of a cytoprotective role

Activation of nuclear factor-κB (NF-κB) can promote or inhibit apoptosis. Oxidative stress is an important mechanism by which certain anticancer drugs kill cancer cells, and is also one of the mechanisms that activate NF-κB. We therefore examined hepatic expression of the NF-κB monomer p65 in human hepatocellular carcinoma (HCC) tissue samples from eight patients and compared it with their respective samples of surrounding liver tissues. We also studied the effect of NF-κB inhibition in human HCC cells exposed to oxidative stress, by infecting HuH7 cells with a recombinant adenovirus carrying mutant IκBα (mIκBα). Cultured HuH7 cells were infected with mIκBα or β-galactosidase (β-Gal) for 24 hr followed by treatment with increasing concentrations of H2O2. Cytotoxicity, NF-κB translocation, NF-κB DNA binding, cell proliferation, and apoptosis were determined. The monomer p65 was overexpressed in six of eight human HCC tissues. In HuH7 cells, introduction of mIκBα potently inhibited the translocation, activation, and DNA binding of NF-κB. In control (β-Gal-infected) HuH7 cells, exposure to H2O2 produced a dose-dependent increase in apoptosis, regardless of NF-κB status. mIκBα- mediated inhibition of NF-κB activation sensitized HuH7 cells to H 2O2-induced inhibition of cell growth, and further promoted cell death. Addition of H2O2 (200-500 μM) to control or mIκBα-infected HuH7 cells enhanced caspase-3 activity and cleavage. Adenovirus-mediated transfer of mIκBα potently inhibits NF-κB activity in HuH7 cells, and this enhances oxidative stress-induced cell killing. © Mary Ann Liebert, Inc.published_or_final_versio

MicroRNA-143 is a potential tumor suppressor targeting DNA methyltransferases 3a in colorectal cancer

Gastroenterology, 2009, v. 136 n. 5, suppl.1, p. A165, abstract no. 10692009 DDW (Digestive Disease Week) Abstract Supplement , AGA (American Gastroenterological Association) Institute Topic Forum, Oral sessions: Scientific sessions: Microrna and digestive cancers, Oral presentation no. 1069postprin

Promoter methylation of CDKN2A and lack of p16 expression characterize patients with hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>The product of CDKN2A, p16 is an essential regulator of the cell cycle controlling the entry into the S-phase. Herein, we evaluated CDKN2A promoter methylation and p16 protein expression for the differentiation of hepatocellular carcinoma (HCC) from other liver tumors.</p> <p>Methods</p> <p>Tumor and corresponding non-tumor liver tissue samples were obtained from 85 patients with liver tumors. CDKN2A promoter methylation was studied using MethyLight technique and methylation-specific PCR (MSP). In the MethyLight analysis, samples with ≥ 4% of PMR (percentage of methylated reference) were regarded as hypermethylated. p16 expression was evaluated by immunohistochemistry in tissue sections (n = 148) obtained from 81 patients using an immunoreactivity score (IRS) ranging from 0 (no expression) to 6 (strong expression).</p> <p>Results</p> <p>Hypermethylation of the CDKN2A promoter was found in 23 HCCs (69.7%; mean PMR = 42.34 ± 27.8%), six (20.7%; mean PMR = 31.85 ± 18%) liver metastases and in the extralesional tissue of only one patient. Using MSP, 32% of the non-tumor (n = 85), 70% of the HCCs, 40% of the CCCs and 24% of the liver metastases were hypermethylated. Correspondingly, nuclear p16 expression was found immunohistochemically in five (10.9%, mean IRS = 0.5) HCCs, 23 (92%; mean IRS = 4.9) metastases and only occasionally in hepatocytes of non-lesional liver tissues (mean IRS = 1.2). The difference of CDKN2A-methylation and p16 protein expression between HCCs and liver metastases was statistically significant (p < 0.01, respectively).</p> <p>Conclusion</p> <p>Promoter methylation of CDKN2A gene and lack of p16 expression characterize patients with HCC.</p

Metallothionein in human oesophagus, Barrett's epithelium and adenocarcinoma

The potential of the metal-binding protein, metallothionein, in assessing the progression of normal oesophagus through Barrett's to adenocarcinoma was investigated. Metallothionein was quantitatively determined in resected tissues from patients undergoing oesophagectomy for high grade dysplasia/adenocarcinoma and in biopsies from patients with Barrett's syndrome. In 10 cancer patients, metallothionein concentrations in adenocarcinoma were not significantly different from normal oesophagus, although six had elevated metallothionein concentrations in the metaplastic tissue bordering the adenocarcinoma. In 17 out of 20 non-cancer patients with Barrett's epithelium, metallothionein was significantly increased by 108% (P<0.004). There was no association between the metallothionein levels in Barrett's epithelium and the presence of inflammatory cells, metaplasia or dysplasia. Metallothionein is a marker of progression from normal to Barrett's epithelium but is not increased in oesophageal adenocarcinoma

Expression of peroxisome proliferator-activated receptor δ in human gastric cancer and its response to specific COX-2 inhibitor

Peroxisome proliferator-activated receptor δ (PPARδ) is ligand-activated transcription factor of the nuclear receptor superfamily which is recently implicated in carcinogenesis. We examined the expression profiles of PPARδ in human gastric cancer, normal gastric mucosa and gastric cancer cell lines by RT-PCR, Western blot and immunohistochemistry. PPARδ mRNA and protein was found to be ubiquitously expressed in all 5 gastric cancer cell lines, 40 gastric cancer samples and 10 normal gastric mucosa from non-cancer patients. Positive immunoreactivity was detected in the nuclei of normal and malignant gastric epithelium. Treatment of gastric cell line MKN45 that overexpressed cyclooxygenase-2 (COX-2) with specific COX-2 inhibitor NS398 resulted in a time- and dose-dependent suppression of PPARδ expression. In contrast, there was no suppression of PPARδ in MKN28 gastric cell line with low COX-2 expression. Our results demonstrated the ubiquitous expression of PPARδ in normal and cancer gastric epithelium. Suppression of PPARδ may be one of the mechanisms underlying the chemopreventive effects of COX-2 inhibitor. © 2004 Elsevier Ireland Ltd. All rights reserved.link_to_subscribed_fulltex

Troglitazone inhibits tumor growth in hepatocellular carcinoma in vitro and in vivo

Peroxisome proliferator-activated receptor gamma (PPARgamma) has been implicated in the differentiation and growth inhibition of cancer cells. We examined the effects of PPARgamma activation by troglitazone on hepatocellular carcinoma (HCC) cell growth, proliferation, and apoptosis in vitro and in vivo. We also studied relationships between PPARgamma activation and cyclooxygenase-2 (COX-2) expression. Human HCC cell lines Huh7 and Hep3B were cultured in the presence or absence of troglitazone. Cell growth was determined via WST-1 assay, proliferation by cell cycle analysis and proliferating cell nuclear antigen (PCNA) Western blotting, and apoptosis by flow cytometry and TUNEL. Tumor growth after subcutaneous implantation of Huh7 cells in nude mice was monitored, and the effects of treatment with troglitazone were determined. In resected HCCs, PPARgamma expression was less compared with the histologically normal surrounding liver. In cultures of Hep3B and Huh7 cells, basal expression of PPARgamma was relatively low, but troglitazone caused dose-dependent induction of PPARgamma expression. Cell cycle analysis revealed a decreased proportion of cells in S phase, with arrest at G0/G1. Concomitant downregulation of PCNA and an increase in TUNEL staining, cells were consistent with decreased proliferation and induction of apoptosis by troglitazaone. Troglitazone-mediated PPARgamma activation also suppressed COX-2 expression and induced p27 in HCC cells. Administration of troglitazone to Huh7 tumor-bearing mice significantly reduced tumor growth and caused tumor regression. In conclusion, collectively, these results indicate that PPARgamma could be a regulator of cell survival and growth in HCC. PPARgamma therefore represents a putative molecular target for chemopreventive therapy or inhibition of liver cancer growth

Absence of cyclin D2 expression is associated with promoter hypermethylation in gastric cancer

Expression of cyclin D2 is absent in 30-70% of gastric cancers. We investigated the role of promoter hypermethylation in the transcriptional silencing of cyclin D2 in five gastric cell lines and 47 primary gastric carcinomas. CpG island methylation status of the cyclin D2 gene was studied by methylation-specific polymerase chain reaction and bisulphite sequencing. RNA and protein expression was analysed by reverse transcription-PCR and Western blot, respectively. Dense methylation of cyclin D2 was detected in three cell lines (KATOIII, AGS and NCI-N87), which also lacked cyclin D2 mRNA and protein expression. Bisulphite DNA sequencing revealed that loss ofcyclin D2 expression was closely associated with the density of methylation in the promoter region. Treatment with DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine, restored the cyclin D2 expression level in methylated gastric cells. Among the 47 primary gastric cancers, cyclin D2 hypermethylation was detected in 23 (48.9%) cases. None of the 23 normal gastric biopsies from noncancer patients showed hypermethylation. Hypermethylation was associated with loss of mRNA (P < 0.001) and protein (p = 0.006) expressions. Our study showed that cyclin D2 hypermethylation is associated with loss of cyclin D2 expression in a subset of gastric cancers, which may suggest an alternative gastric carcinogenesis pathway in the absence of cyclin D2 expression. © 2003 Cancer Research UK.link_to_subscribed_fulltex

Expression of trefoil peptides (TFFI, TFF2, and TFF3) in gastric carcinomas, intestinal metaplasia, and non-neoplastic gastric tissues

Trefoil factor family (TFF) domain peptides consist of three members that play a role in intestinal mucosal defence and repair, and in tumourigenesis. The role of the three TFF members in the gastric carcinogenesis cascade remains poorly defined. This study examined seven gastric cell lines, 50 gastric cancers and their adjacent non-cancer tissues, and tissues from 40 non-cancer patients, in order to elucidate the chronology of TFF expression in various stages of gastric carcinogenesis. TFF expression was determined by RT-PCR, immunohistochemistry, and western blot. Aberrant expression of TFF1, TFF2, and TFF3 was frequently detected in gastric cell lines. Specifically, TFF1 was detected in all non-cancer patients, but was detected in only 50% of gastric cancer and 66% of adjacent normal tissues. TFF2 expression was demonstrated in 87.5% of non-cancer patients, 34% of gastric carcinomas, and 58% of adjacent non-cancer tissues. There was a significant correlation between TFF1 and TFF2 expression in gastric cancer and adjacent non-cancer tissues (p<0.001). By contrast, TFF3 was detected in 25% of non-cancer patients and showed a predilection for areas with intestinal metaplasia (p = 0.005). Sixty-two per cent of gastric cancers and 24% of neighbouring non-cancer tissues showed TFF3 expression. Immunoreactivity against TFF3 was demonstrated in goblet cells of intestinal metaplasia and within the cytoplasm and nuclei of tumour cells. Progressive loss of TFF1 and TFF2, together with the induction of TFF3, is likely to be involved in the early stage of the multi-step gastric carcinogenesis pathway. Copyright © 2002 John Wiley & Sons, Ltd.link_to_subscribed_fulltex

Loss of XIAP sensitizes colon cancer cells to PPARγ independent antitumor effects of troglitazone and 15-PGJ2

We investigated whether the anticancer effect of a combination of XIAP down-regulation and PPAR γ activation on colon cancer is PPARγ receptor dependent. HCT116-XIAP +/+ cells and HCT116-XIAP -/- cells were treated with troglitazone or 15-deoxy-Δ 12,14-prostaglandin J2 (15-PGJ2) with or without prior exposure to PPARγ inhibitor GW9662. Cell proliferation and apoptosis was evaluated. Athymic mice carrying HCT116-XIAP -/- cells-derived tumors were treated with troglitazone in the presence or absence of GW9662. Inhibition of cell proliferation and induction of apoptosis by troglitazone and 15-PGJ2 were more prominent in HCT116-XIAP -/- cells. PPARγ ligand-induced growth inhibition, apoptosis, caspase and PARP cleavage could not be blocked by GW9662. Troglitazone significantly retarded growth of xenograft tumors and this effect was not blocked by GW9662. Marked apoptosis and an up-regulation of E-cadherin were observed in xenograft tumor tissues, and GW9662 did not affect these effects. Thus, a combination of XIAP down-regulation and PPARγ ligands exert a significant anticancer effect in colon cancer via a PPARγ independent pathway. © 2008 Elsevier Ireland Ltd. All rights reserved.link_to_subscribed_fulltex