Expression of Fas antigen and its mediation of apoptosis in human gastric cancer cell lines

Urushiol Induces Apoptosis via a p53-dependent Pathway in Human Gastric Cancer Cells

BACKGROUND

Urushiols are mixtures of olefinic catechols which is isolated from the sap of Korean lacquer tree (Rhus vernicifera Stokes). The aim of this study was to determine the anticancer effects of urushiol in human gastric adenocarcinoma cell lines.

METHODS

The cytotoxicity of urushiols was assessed by MTT assays on the two gastric adenocarcinoma cell lines, MKN-45 (wild type of p53) and MKN-28 (mutant type of p53). We also examined the action mechanisms of urushiol by analyzing its effects on cell cycle progression and apoptosis induction.

RESULTS

The cytotoxic results from MTT assays indicated that urushiol inhibited human gastric cancer cell growth in a dose-dependent manner, with IC50 values of approximately 15 and 20 μg/ml on MKN-45 and MKN-28 cells, respectively. Urushiol mediated cell death on these two cancer cell lines through different pathways. Urushiol induced apoptosis on MKN-45 cells, concomitant with apoptotic nuclear change, DNA fragmentation, poly (ADP-ribose) polymerase cleavage and apoptotic body formation via extrinsic pathway of apoptosis. However, no apoptotic features were induced by urushiol treatment on MKN-28 cells. Urushiol induced cytostatic cell growth inhibition via upregulation of the cyclin-dependent kinase inhibitors, p21 (WAF1/CIP1) and p27 (KIP1) proteins and down-regulation of cyclin-dependent kinase 2 and 4 proteins in a p53-independent manner.

CONCLUSIONS

These data provide evidence that urushiol has the potential to be used as a chemotherapeutic agent in human gastric cancer.

Immunohistochemical analysis of phospho-BAD protein and mutational analysis of BAD gene in gastric carcinomas

Mounting evidence indicates that deregulation of apoptosis contributes to the development of human cancers. BAD, a proapoptotic Bcl-2 family protein, regulates the intrinsic apoptosis pathway. The aim of this study was to explore whether alterations of phospho-BAD (p-BAD) protein that antagonizes apoptosis function of BAD and mutation of BAD gene are characteristics of human gastric cancers. We analyzed expression of p-BAD in 60 gastric adenocarcinomas by immunohistochemistry. Also, we analyzed BAD gene for detection of somatic mutations by single-strand conformation polymorphism (SSCP) assay. p-BAD expression was detected well in normal gastric mucosal epithelial cells, whereas it was detected in only 51% (31 of the 60) of the cancers. There was no somatic mutation of BAD gene in the 60 gastric cancer samples. The decreased expression of p-BAD in malignant gastric epithelial cells compared to normal mucosal epithelial cells suggested that loss of p-BAD expression may play a role in gastric tumorigenesis. The data also suggest that BAD mutation may not be a direct target of inactivation in gastric tumorigenesis.

Expression of phosphorylated caspase-9 in gastric carcinomas

Alterations of caspases, the main executioners of apoptosis, have been described in human cancers. Caspase-9 plays a crucial role in the initiation phase of the intrinsic apoptosis pathway. Caspase-9 is phosphorylated at Thr125 through the mitogen-activated protein kinase (MAPK) pathway, and this phosphorylation is associated with inhibition of caspase-9 activation. The aim of this study was to explore whether phosphorylated caspase-9 (p-caspase-9) expression could be a characteristic of gastric carcinomas. We analyzed expression of p-caspase-9 protein in 60 gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. p-caspase-9 was detected in 33 of the 60 carcinomas (55%). Both early and advanced gastric carcinomas expressed p-caspase-9. There was no significant association of p-caspase-9 expression with clinocopathological characteristics, including invasion, metastasis and stage. In contrast to gastric cancer cells, epithelial cells in normal gastric mucosa showed no or only weak expression of p-caspase-9. Taken together, these results indicate that caspase-9 is frequently phosphorylated in gastric carcinomas, and that the phosphorylation of caspase-9 might be an inhibitory mechanism of caspase-9-mediated apoptosis in gastric carcinomas. Increased expression of p-caspase-9 in malignant gastric epithelial cells compared to normal mucosal epithelial cells suggests that p-caspase-9 expression might play a role in gastric carcinoma development.

Decreased expression of tumour suppressor Bax-interacting factor-1 (Bif-1), a Bax activator, in gastric carcinomas

AIMS

Evasion of apoptosis is one of the hallmarks of cancer. Bax-interacting factor-1 (Bif-1) interacts with both Bax and Bak that are essential for the intrinsic pathway of apoptosis, and enhances apoptosis. The aim of this study was to explore whether alteration of Bif-1 expression might be a characteristic of gastric cancer.

METHODS

We analysed the expression of Bif-1 protein in 60 gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach.

RESULTS

In normal gastric mucosal cells, surface and glandular epithelial cells strongly expressed Bif-1. While Bif-1 expression was detected in 24 cases (40%) of the gastric carcinomas, there was no Bif-1 immunostaining in the remaining 36 cancers. Even in the 24 cases with positive Bif-1 immunostainings, 10 cancers showed decreased intensity of immunostaining compared with the normal mucosal epithelial cells.

CONCLUSION

The decreased expression of Bif-1 in malignant gastric epithelial cells compared with the normal mucosal cells suggests that loss of Bif-1 expression may play a role in gastric tumorigenesis, possibly by inhibiting the apoptosis mediated by Bif-1.

Expression of RUNX3 protein in human esophageal mucosa and squamous cell carcinoma

Runt-related transcriptional factor gene 3 (RUNX3) belongs to the runt domain family of transcriptional factors that plays an important role during normal tissue development and in tumorigenesis in several organs. This study examined the expression of RUNX3 protein in human esophageal mucosa and squamous cell carcinoma in comparison with clinicopathological profiles. Western blot analysis and RT-PCR revealed that both RUNX3/P44 and P27, but not P46, were expressed in all three human esophageal squamous cell carcinoma (SCC) cell lines, as well as in three pairs of esophageal SCC cell lines and the corresponding nontumoral mucosa specimens. RUNX3 expression was shown in prickle and functional cell layer cells in normal esophageal mucosa. On the other hand, immunoreactivity was seen only in carcinoma cells around the cancer pearls. RUNX3 expression was significantly higher in the 19 well-differentiated SCCs than in the 56 moderately or 69 poorly differentiated SCCs (p < 0.01). The 3-year survival rate was significantly lower in the 29 patients with lower RUNX3 expression than in the 37 patients with higher expression (p = 0.0003). These results indicated that RUNX3 protein might play an important role in cellular differentiation in both esophageal mucosa and SCC. The expression correlated with the patients' prolonged survival, implying a tumor suppressive effect in esophageal SCCs.

Overcoming Fas-mediated apoptosis accelerates Helicobacter-induced gastric cancer in mice

The initiating molecular events in Helicobacter-induced gastric carcinogenesis are not known. Early in infection, Fas antigen-mediated apoptosis depletes parietal and chief cell populations, leading to architectural distortion. As infection progresses, metaplastic and dysplastic glands appear, which are resistant to Fas-mediated apoptosis. These abnormal lineages precede, and are thought to be the precursor lesions of, gastric cancer. Acquisition of an antiapoptotic phenotype before transformation of cells suggests that loss of Fas sensitivity may be an early required trait for gastric cancer. We reasoned that forced Fas-apoptosis resistance would result in earlier and more aggressive gastric cancer in our mouse model. Fas antigen-deficient (lpr) mice or C57BL/6 wild-type mice were irradiated and reconstituted with C57BL/6 marrow forming partial lpr/wt chimera or wt/wt control mice, extending the life span of the lpr and ensuring a competent immune response to Helicobacter felis infection. Infected lpr/wt mice developed gastric cancer as early as 7 months after infection (compared with 15 months in wt/wt mice). At 10 months (90%) and 15 months (100%), mice developed aggressive invasive lesions. This earlier onset and more aggressive histology strongly argues that Fas-apoptosis resistance is an early and important feature of gastric cancer formation.

Pharmacological activity in growth inhibition and apoptosis of cultured human leiomyomal cells of tropical plant Scutellaria barbata D. Don (Lamiaceae)

Scutellaria barbata D. Don (Lamiaceae) (SB), which is known in traditional Korean medicine, has been used as an anti-inflammatory and antitumor agent. Since uterine leiomyoma is the most common benign smooth muscle cell tumor of the myometrium, we aimed to determine the growth inhibition and the induction of apoptotic cell death brought about by the herb SB in two different leiomyomal cells, named LM-1 and LM-2, and to clarify the mechanism of this apoptosis. Water-soluble ingredients of SB, and the leiomyomal cell lines of LM-1 and LM-2, were used in vitro. Growth inhibition, induction of cell death, morphological features, the presence of DNA ladders, increases in Caspase 3-like activity, the effects of a Caspase 3 inhibitor on apoptotic cell death, and the release of Cytochrome C by SB were analyzed. SB inhibited the growth and decreased the viability of the leiomyomal cells. The viability of normal myomatrial smooth muscle cells (SMC) in the presence of low concentrations of SB was higher than those of leiomyomal cells. Apoptotic bodies and DNA ladders were observed to be induced in leiomyomal cells of LM-1 and LM-2 by SB. The synthetic tetrapeptide Caspase 3 inhibitor, N-acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO), inhibited the apoptotic cell death of leiomyomal cells induced by SB. The Caspase 3-like activity in leiomyomal cells LM-1 and LM-2 increased after the addition of SB. Cytochrome C was released from mitochondria into the cytosol 8h after the addition of SB, and reached a peak at 16h. The peak of Cytochrome C release was earlier than that of Caspase 3-like activity. We concluded that SB inhibited the growth of the leiomyomal cells and induced apoptosis. The apoptosis of leiomyomal cells induced by SB was associated with the release of Cytochrome C from the mitochondria, followed by an increase in Caspase 3-like activity.

COX-2 inhibitor, NS398, enhances Fas-mediated apoptosis via modulation of the PTEN-Akt pathway in human gastric carcinoma cell lines

A variety of human cancer cells are resistant to Fas ligand and anti-Fas antibody induced apoptosis. Previously, we reported that human gastric carcinoma cell lines were resistant to the anti-Fas antibody, CH-11, without interferon-gamma pretreatment in vitro. Cyclooxygenase (COX)-2 is known to be expressed in many human malignancies, and is correlated with tumor progression and resistance to apoptosis. This study examined whether NS398, a COX-2 inhibitor, inhibited cell proliferation and increased Fas-mediated apoptosis in human gastric carcinoma cell lines. Treatment of NS398 inhibited cell proliferation in MKN-45, which expressed the highest level of COX-2 among seven human gastric carcinoma cell lines, in a dose- and time-dependent manner, in contrast to less prominent effects in KATO-III, which expresses no COX-2. Although the treatment of CH-11 induced apoptosis in both cells, the simultaneous treatment of NS398 and CH-11 remarkably induced apoptosis, as confirmed by Hoechst 33258 staining and the terminal deoxynucleotidyl transferase- mediated dUTP-digoxigenin nick-end labeling (TUNEL) method in MKN-45. Flow cytometric analysis also revealed the increased pre-G1 fraction by the simultaneous treatment. The treatment of NS398 induced upregulation of Bad and PTEN, and downregulation of phosphorylated Akt (Thr308). These findings suggest that COX-2 might inhibit Fas-mediated apoptosis in human gastric carcinoma cell lines, especially MKN-45, by modulating PTEN and Akt.

Expression of RUNX3 protein in human gastric mucosa, intestinal metaplasia and carcinoma

BACKGROUND

Human runt-related transcription factor gene 3 (RUNX3) is considered as a possible candidate of tumour suppressor gene in human gastric carcinoma.

MATERIALS AND METHODS

To investigate the RUNX3 protein expression in human gastric mucosa and carcinoma, we generated a polyclonal antibody, AS251, which recognized amino acid sequences from 251 to 266 of human RUNX3. The AS251 antibody was immunoreactive with only RUNX3 protein, but not with RUNX1 and RUNX2. The AS251-antibody was available for Western blotting and immunohistochemistry using paraffin-embedded specimens.

RESULTS

Western-blot analysis revealed that three (MKN-1, -7 and -45) of six human gastric carcinoma cell lines variably expressed RUNX3 protein, consistent with the expression pattern of RUNX3 mRNA reported previously by Li et al. (Cell 2002;109:113-24). Immunohistochemistry disclosed RUNX3 protein in most chief cells and a few gastrin-containing G cells in normal mucosa, but not in intestinal metaplasia and carcinoma cells.

CONCLUSIONS

These data suggest that RUNX3 may play a physiologic role in chief cells and G cells in gastric mucosa, and that suppression of RUNX3 expression in intestinal metaplasia and carcinoma of human stomach may be implicated in gastric carcinogenesis.

Loss of caspase-2, -6 and -7 expression in gastric cancers

Female adnexal tumor of probable Wolffian origin (FATWO) is a rare entity which is believed to originate from mesonephric (Wolffian) remnants on the basis of its location where the remnants are abundant. Its behavior is usually indolent, although some cases can recur or metastasize. The authors present the clinicopathological features of two cases of FATWO arising in the broad ligament, and focus on the expression of adhesion molecules and proliferative marker. Mesonephric duct remnants are also examined in an attempt to elucidate the histogenesis of FATWOs. The two FATWOs were well-circumscribed solid masses arising in the leaves of the broad ligament and histological examination revealed a mixture of cysts and tubules imparting a sieve-like pattern and mucin-negative eosinophilic secretion within these tubules. Immunohistochemically, the tumors showed the expression of cytokeratin 7 and 20, high-molecular-weight cytokeratin, and calretinin, which closely resembled that of the mesonephric duct remnants. Regarding CK 20, CD 10, EMA, S-100 protein, and vimentin their expression was in part not identical with previous studies. E-cadherin, alpha and beta-catenin were strongly expressed along the cell membrane of the tumor cells. The Ki-67 labeling index of FATWO was 0% and 3.2% in each case. The preservation of the E-cadherin-catenin complex and low Ki-67 labeling index could explain the indolent behavior and low malignant potential of this tumor.

Role of the phosphatidylinositol 3'-kinase-Akt signal pathway in the proliferation of human pancreatic ductal carcinoma cell lines

: Phosphatidylinositol 3'-kinase (PI3K) and Akt mediate survival signals and allow the cells to escape apoptosis in various human cancers. We postulated that LY294002, a PI3K inhibitor, might inactivate Akt, consequently inhibiting cell proliferation in 3 human pancreatic ductal carcinoma cell lines, PSN-1, PANC-1, and KP-4. LY294002 (50 micromol/L) caused a decrease in phosphorylated Akt and inhibition of cell proliferation in a time-dependent manner, but there was no obvious induction of apoptosis. Flow cytometric analysis revealed that pancreatic cancer cells treated with 50 micromol/L LY294002 underwent G1 arrest, which was associated with dephosphorylation of the ppRB protein, a decrease in the protein expression of cyclin D and E, and their activating partners Cdk2, 4, and 6 with simultaneous accumulation of P27/Kip1. Our data indicate that P27/Kip1 accumulation by Akt inactivation could induce cell cycle arrest in the G1 phase and suggest that the PI3K-Akt pathway plays an important role in cell proliferation in human pancreatic ductal carcinoma cells.

Endogenous decoy receptor 3 blocks the growth inhibition signals mediated by Fas ligand in human pancreatic adenocarcinoma

Many cancers are resistant to Fas-mediated apoptosis despite the expression of Fas. To investigate the mechanisms by which Fas signals are attenuated, we focused on decoy receptor 3 (DcR3). DcR3 is a soluble receptor against Fas ligand belonging to the tumor necrosis factor receptor superfamily and overexpresses in some forms of cancers. Exogenous DcR3 inhibits Fas-mediated apoptosis in Fas-sensitive Jurkat cells. In our study, we examined the expression and function of DcR3 in pancreatic cancers. TaqMan RT-PCR showed that DcR3 mRNA was highly expressed in pancreatic cancer cell lines (71%) and tissues (67%). Its expression significantly correlated with cancer invasion to veins. Western blotting showed that the DcR3 protein was produced and secreted in 4 of 6 cell lines. The protein expressions were compatible with the mRNA expression. Five of 7 pancreatic cancer cell lines became sensitive to agonistic anti-Fas antibody (CH-11) to various extents, without Fas upregulation, when exposed to CH-11 for 48 hr after pretreatment with IFNgamma. Four of 7 pancreatic cancer cell lines were inhibited from growing, compared to control cells, when cocultured with membrane-bounded Fas ligand (mFasL) transfected lymphomas for 48 hr after pretreatment with IFNgamma. DcR3 reduced this growth inhibition when added exogenously. Regression analysis showed that the DcR3 expression significantly correlated with the sensitivity to mFasL, and not to CH-11. These results suggest that DcR3 is highly expressed in many pancreatic cancers and endogenous DcR3 blocks the growth inhibition signals mediated by mFasL. DcR3 can be a candidate target molecule for the therapeutic intervention.

Increased expression of FLIP, an inhibitor of Fas-mediated apoptosis, in stomach cancer

Despite the cell surface expression of Fas (Apo-1/CD95), many types of tumor cells, including stomach cancer cells, are resistant to Fas-mediated apoptosis, indicating the presence of inactivating mechanisms of Fas signaling. Expression of FLICE-like inhibitory protein (FLIP), one of the inhibitory proteins of Fas-mediated apoptosis, has been reported in several cancer types, but not in stomach cancer. In the present study, we analyzed the expression of Fas and FLIP in 60 advanced gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. Immunopositivity (defined as >/=30% of the neoplastic cells) was observed for Fas in 58 (97%) and FLIP in 54 (90%) of the 60 cancers. All of the tumors with FLIP immunostaining also showed Fas immunostaining. Loss of cell surface Fas immunostaining, another mechanism of Fas resistance, was observed in 45 tumors (75%). By contrast, normal gastric mucosal cells showed no or weak expression of both Fas and FLIP. Taken together, these results indicate that increased expression of FLIP is a frequent event in stomach carcinomas, and suggest that for evading apoptosis stomach carcinoma cells in vivo may need FLIP expression, which might contribute to tumor development.

Stomach cancer highly expresses both initiator and effector caspases; an immunohistochemical study

Caspases play an essential role during apoptotic cell death. While caspases 8 and 10 act as initiator caspases of the extrinsic apoptosis pathway, caspase 9 acts as an initiator caspase of the intrinsic apoptosis pathway. Caspase 3 is considered to be the main effector caspase involved in both intrinsic and extrinsic pathways. Alteration of apoptosis is essential for cancer development. Thus, analysis of the expression status of caspases, the main executioners of apoptosis, in cancer tissues is needed for a sophisticated understanding of cancer biology. In the current study, we analyzed the expression of caspases 3, 8, 9 and 10 in 60 advanced gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. Immunopositivity was observed for caspase 3 in 57 (95%), caspase 8 in 56 (93%), caspase 9 in 54 (90%), and caspase 10 in 58 (97%) of the 60 cancers. While 46 cancers (77%) expressed all of the caspases examined, 14 cancers (23%) showed loss of expression in one or more caspases examined. Normal gastric mucosal cells showed no or weak expression of caspases 3, 8, 9 and 10. Taken together, these results suggest that stomach cancer cells in vivo may need caspase expression for apoptosis. Also, higher expression of the caspases in stomach cancer cells than in normal gastric mucosal cells suggests that apoptosis in susceptible stomach cancer cells might be easily triggered, thereby producing selective pressure to make more apoptosis-resistant cells during tumor development.

Helicobacter pylori organisms induce expression of activation and apoptotic surface markers on human lymphocytes and AGS cells: a cytofluorimetric evaluation

Human peripheral blood mononuclear cells (PBMCs) were treated with Helicobacter pylori (Hp) organisms alone or with Hp-stimulated AGS cells (a gastric adenocarcinoma cell line). Hp organisms were able per se to increase the percentage of CD8 +/- CD95 +/- cells, while number of CD25+ cells and HLA-DR molecule expression increased following pretreatment with Hp-stimulated AGS cells. A comparison was made with a test system in which PBMCs were stimulated with Escherichia coli (Ec) organisms and colo-cells (a colon carcinoma cell line). In this case, CD95+ cells and CD25+ cells increased when the combination Ec organisms/colo-cells was present in the culture. On the other hand, Hp bacteria in combination with colo-cells were not able to induce activation and/or apoptotic surface markers on PBMCs, while Ec-stimulated AGS cells increased the expression of CD95 on PBMC. Finally, the direct interaction of AGS cells with Hp was able to induce higher expression of CD95 on gastric epithelial cells than Hp-stimulated PBMCs. Taken together, these data support the interplay between bacteria and epithelial cells in the course of Hp-mediated gastropathy.

Expression of manganese superoxide disumutase influences chemosensitivity in esophageal and gastric cancers

The purpose of this study was to examine whether the increased sensitivity of cancer cells to adriamycin (ADM), which is known to produce superoxide radicals, was brought through suppressed manganese superoxide disumutase (MnSOD) expression in the presence of transforming growth factor beta1 (TGFbeta1). T.T., MKN28, and MKN45 cell lines were treated with TGFbeta1 before exposure to ADM. Athymic female mice bearing the MKN28 cells were treated with TGFbeta1, ADM, or TGFbeta1 + ADM. Pretreatment of T.T., MKN28, and MKN45 cell lines with TGFbeta1 resulted in increased sensitivity to ADM. In contrast, simultaneous exposure to TNFalpha, which increased MnSOD expression, decreased sensitivity of cancer cells to ADM. In vivo studies demonstrated that the combined administration of TGFbeta1 and ADM delayed tumor growth better than either treatment alone. Our results suggest that the synergistic antitumor effects of TGFbeta1 and ADM may be due to decreased MnSOD expression in cancer cells. Thus, combined administration of TGFbeta1 and ADM might prove useful for treatment of malignant disease.

Enhanced disease severity in Helicobacter pylori-infected mice deficient in Fas signaling

Recent evidence suggests that immune-mediated gastric epithelial cell apoptosis through Fas-Fas ligand interactions participates in Helicobacter pylori disease pathogenesis. To define the role of Fas signaling in vivo, H. pylori strain SS1 infection in C57BL/6 mice was compared to that in mice deficient in the Fas ligand (gld). gld mice had a degree of gastritis similar to that of C57BL/6 mice after 6 weeks (gastritis score, 5.2 +/- 0.6 [mean +/- standard error] versus 3.5 +/- 0.8) and 12 weeks (4.0 +/- 0.7 versus 3.4 +/- 0.5) of infection. Bacterial colonization was comparable in each group of mice at 12 weeks of infection (2.1 +/- 0.3 versus 1.6 +/- 0.3 for gld and C57BL/6, respectively; the difference is not significant). Sixty-seven percent of H. pylori-infected gld mice displayed atrophic changes in the gastric mucosa, compared with 37% of infected C57BL/6 mice, at 12 weeks. In addition, atrophic changes were more severe in H. pylori-infected gld mice (P < 0.05). Splenocytes isolated from H. pylori-infected C57BL/6 mice had a twofold increase in production of the Th1 cytokine gamma interferon (IFN-gamma) in response to H. pylori antigens at both 6 and 12 weeks compared to controls (143 +/- 65 versus 69 +/-26 pg/ml and 336 +/- 73 versus 172 +/- 60, respectively). In contrast, there was a lack of detectable IFN-gamma in gld mice infected with the bacterium. H. pylori-infected C57BL/6 mice had increased epithelial cell apoptosis compared with sham-infected C57BL/6 mice (35.0 +/- 8.9 versus 12.3 +/- 6.9; P < 0.05). Epithelial cell apoptosis did not differ between H. pylori-infected and control gld mice (5.2 +/- 1.6 versus 6.5 +/- 2.9 [not significant]). These data demonstrate that mice with mutations in the Fas ligand develop more severe premalignant mucosal changes in response to infection with H. pylori in association with both an impaired gastric epithelial cell apoptotic response and IFN-gamma production. The Fas death pathway modulates disease pathophysiology following murine infection with H. pylori. Deregulation of the Fas pathway could be involved in the transition from gastritis to gastric cancers during H. pylori infection.

Analysis of the gene-expression profile regarding the progression of human gastric carcinoma

BACKGROUND

Tumor tissue consists of a variable mixture of tumor and host-cell populations. Recent developments in laser microdissection (LMD) and cDNA microarray analysis have encouraged us to study the differential gene expression profiles among normal cells, primary carcinoma cells, and metastatic carcinoma cells in cases of gastric carcinoma.

METHODS

Total RNA was extracted from the cells obtained by means of LMD from the primary carcinoma, the corresponding gastric epithelium, and the lymph node metastasis in 5 cases of primary gastric carcinoma. RNA was amplified by the T7-based amplification system to be applied to a cDNA microarray. Thereafter, the differentially expressed genes among the 3 populations were evaluated.

RESULTS

cDNA samples for microarray studies were successfully obtained from each cell population of 5 cases. The cDNA microarray demonstrated that several interesting genes, such as cell-cycle regulators and growth factors, were overexpressed in the metastatic cells compared with in the primary carcinoma cells. Oncogenes and cell-adhesion molecules were more overexpressed in the primary carcinoma cells than in the normal cells. On the other hand, caspase 8 and cadherin were more suppressed in the primary carcinoma cells than in the normal cells. Interestingly, among the matrix metalloproteinase family, only MMP7 was identified as a differentially overexpressed gene in both the primary carcinoma and the metastatic cells in comparison with the normal cells.

CONCLUSIONS

This study demonstrated that the combined use of LMD, T7-based amplification, and a cDNA microarray enabled us to identify genes directly associated with each population of tumor tissue. The method will open up new possibilities for the precise gene analysis of tumor progression and metastasis.

Antitumor action of the PKC activator gnidimacrin through cdk2 inhibition

Daphnane-type diterpene gnidimacrin (NSC252940), isolated from a Chinese plant, exhibited antitumor activity against murine leukemias and solid tumors. At concentrations of 10(-9) to 10(-10) M, this agent strongly inhibited the growth of human tumor cell lines. In sensitive human leukemia K562 cells, gnidimacrin is a PKC activator that arrests the cell cycle in the G(1) phase by inhibiting cdk2 activity. A 4 hr exposure of K562 cells to gnidimacrin induced the CDK inhibitor p21(WAF1/Cip1), but this effect was transient and did not correlate temporally with the onset of G(1) arrest. Expression of cdc25A, a phosphatase that activates cdk2, was reduced during 24-hr exposure to gnidimacrin. Moreover, the suppression corresponded in a concentration- and time-dependent manner to both the inhibition of cdk2 activity and the mobility shift observed when cdk2 was electrophoresed on SDS-PAGE, indicating that the phosphorylation state of cdk2 must change. Cyclin E, the other regulator of cdk2 activity, was not influenced by gnidimacrin. These results suggest that gnidimacrin exerts antitumor activity through suppression of cdc25A and inhibition of cdk2 activity.

Negative selection of T cells by Helicobacter pylori as a model for bacterial strain selection by immune evasion

The majority of humans infected with Helicobacter pylori maintain a lifelong infection with strains bearing the cag pathogenicity island (PAI). H. pylori inhibits T cell responses and evades immunity so the mechanism by which infection impairs responsiveness was investigated. H. pylori caused apoptotic T cell death, whereas Campylobacter jejuni did not. The induction of apoptosis by H. pylori was blocked by an anti-Fas Ab (ZB4) or a caspase 8 inhibitor. In addition, a T cell line with the Fas rendered nonfunctional by a frame shift mutation was resistant to H. pylori-induced death. H. pylori strains bearing the cag PAI preferentially induced the expression of Fas ligand (FasL) on T cells and T cell death, whereas isogenic mutants lacking these genes did not. Inhibiting protein synthesis blocked FasL expression and apoptosis of T cells. Preventing the cleavage of FasL with a metalloproteinase inhibitor increased H. pylori-mediated killing. Thus, H. pylori induced apoptosis in Fas-bearing T cells through the induction of FasL expression. Moreover, this effect was linked to bacterial products encoded by the cag PAI, suggesting that persistent infection with this strain may be favored through the negative selection of T cells encountering specific H. pylori Ags.

Direct growth suppressive activity of interferon-alpha and -gamma on human gastric cancer cells

BACKGROUND AND OBJECTIVES

Interferons (IFNs) exhibit anti-tumor activities through either immune modulation or direct anti-tumor effects. We have investigated the activity and mechanisms of IFN-alpha and IFN-gamma on the growth of TSGH9201, TMK-1 and AGS gastric cancer cells in vitro.

METHODS

Activities of IFNs on cell growth were analyzed by measuring total cellular DNA. Effects of IFNs on apoptosis was evaluated by formation of in situ DNA breakage and DNA ladders. Effects of IFNs on cells cycle phase distribution were analyzed using flow cytometry. Levels of Bcl-2 family proteins after treatment with IFNs were analyzed using Western blot.

RESULTS

Both IFN-alpha and IFN-gamma were active in suppressing the growth of TSGH9201 and TMK-1 cells, while AGS cells were resistant to treatment with IFNs. The IC(50)s of IFN-alpha for TSGH9201 and TMK-1 cells were 300 and 500 U/ml, respectively, and the IC(50)s of IFN-gamma were 40 and 2.0 U/ml, respectively. Both IFN-alpha- and IFN-gamma-induced cell cycle arrest in sensitive cells. IFN-gamma also increased cellular apoptosis, demonstrated by increasing in situ DNA damage and DNA fragmentation. IFN-gamma increased BAK protein levels and decreased Bcl-2 and Bcl-X(S) protein levels in TSGH9201 cells.

CONCLUSIONS

IFN-alpha suppressed growth of gastric cancer cells through induction of cell cycle arrest. IFN-gamma suppressed cell growth through induction of both cell cycle arrest and apoptosis. IFN-gamma-mediated apoptosis was associated with the alteration in protein levels of Bcl-2, Bcl-X(S) and BAK.

Helicobacter pylori modulates lymphoepithelial cell interactions leading to epithelial cell damage through Fas/Fas ligand interactions

Helicobacter pylori causes a common chronic infection of humans that leads to epithelial cell damage. Studies have shown that apoptosis of the gastric epithelium is increased during infection and this response is associated with an expansion of gastric T-helper type 1 (Th1) cells. We report that gastric T cells contribute to apoptosis of the epithelium by a Fas/Fas ligand (FasL) interaction. Fas receptor expression was detected on freshly isolated gastric epithelial cells by flow cytometry and immunohistochemistry, and this level of expression was increased during infection with H. pylori. The expression of Fas receptor on three gastric epithelial cell lines was increased by H. pylori, either alone or in combination with gamma interferon or tumor necrosis factor alpha. The role of Fas in apoptosis of gastric epithelial cell lines was evidenced by DNA fragmentation after cross-linking of Fas with specific antibodies. FasL expression was detected by immunohistochemistry on mononuclear cells in gastric biopsy specimens of infected but not uninfected subjects. Gastric T-cell lines were also shown to express FasL, as evidenced by reverse transcription-PCR and killing of target cells expressing Fas receptor. Moreover, these T-cell lines were capable of killing cultured gastric epithelial target cells and antibodies that block the interaction between Fas receptor and FasL inhibited this cytotoxic activity. These observations demonstrate that local Th1 cells may contribute to the pathogenesis of gastric disease during H. pylori infection by increasing the expression of Fas on gastric epithelial cells and inducing apoptosis through Fas/FasL interactions.

Role of apoptosis in gastric epithelial turnover

Gastric epithelial turnover is a dynamic process. It is characterized by continuous cell proliferation, which is counterbalanced by cell loss. The biological principle that mediates the homeostasis of epithelium is programmed cell death, or apoptosis. Currently, several subtypes of apoptosis are distinguished, which are mediated by different mechanisms. Various subtypes of apoptosis also occur in the gastric epithelium under various conditions. In the normal stomach, apoptosis due to cell isolation (anoikis) mediates the physiological epithelial turnover. Albeit rarely seen in routine histology, approximately 2% of epithelial cells in the normal stomach are apoptotic. In Helicobacter pylori-induced gastritis, apoptosis and epithelial proliferation are moderately increased, with approximately 8% apoptotic epithelial cells. In gastritis, factors such as CD95 ligand or tumor necrosis factor (TNF) alpha act as death factors. They bind to specific receptors, CD95 and TNF-R, which are induced either by other cytokines, such as interferon gamma, or by Helicobacter pylori itself. In addition to CD95, H.pylorican also induce upregulation of CD95 ligand expression. Taken together, the upregulated expression of CD95, and the presence of CD95L in the close proximity to apoptotic gastric epithelial cells suggest a functional role of the CD95-CD95L system in the induction of apoptosis in H.pylori-gastritis. The role of other pathways to apoptosis is currently under study. Apart from being a biological phenomenon, apoptosis in the stomach may also have direct clinical consequences. An extreme example is given in gastric graft-vs.-host disease when epithelial denudement occurs.

Helicobacter pylori induces gastric epithelial cell apoptosis in association with increased Fas receptor expression

The mechanisms involved in mediating the enhanced gastric epithelial cell apoptosis observed during infection with Helicobacter pylori in vivo are unknown. To determine whether H. pylori directly induces apoptosis of gastric epithelial cells in vitro and to define the role of the Fas-Fas ligand signal transduction cascade, human gastric epithelial cells were infected with H. pylori for up to 72 h under microaerophilic conditions. As assessed by both transmission electron microscopy and fluorescence microscopy, incubation with a cagA-positive, cagE-positive, VacA-positive clinical H. pylori isolate stimulated an increase in apoptosis compared to the apoptosis of untreated AGS cells (16.0% +/- 2.8% versus 5.9% +/- 1. 4%, P < 0.05) after 72 h. In contrast, apoptosis was not detected following infection with cagA-negative, cagE-negative, VacA-negative clinical isolates or a Campylobacter jejuni strain. In addition to stimulating apoptosis, infection with H. pylori enhanced Fas receptor expression in AGS cells to a degree comparable to that of treatment with a positive control, gamma interferon (12.5 ng/ml) (148% +/- 24% and 167% +/- 24% of control, respectively). The enhanced Fas receptor expression was associated with increased sensitivity to Fas-mediated cell death. Ligation of the Fas receptor with an agonistic monoclonal antibody resulted in an increase in apoptosis compared to the apoptosis of cells infected with the bacterium alone (38.5% +/- 7.1% versus 16.0% +/- 2.8%, P < 0.05). Incubation with neutralizing anti-Fas antibody did not prevent apoptosis of H. pylori-infected cells. Taken together, these findings demonstrate that the gastric pathogen H. pylori stimulates apoptosis of gastric epithelial cells in vitro in association with the enhanced expression of the Fas receptor. These data indicate a role for Fas-mediated signaling in the programmed cell death that occurs in response to H. pylori infection.

Transitional cell carcinoma expresses high levels of Fas ligand in vivo

OBJECTIVE

To characterize the Fas-Fas ligand system, a main apoptotic pathway, in transitional cell carcinoma (TCC) of the urinary bladder, by analysing the expression of Fas and Fas ligand (FasL) in TCC samples.

MATERIALS AND METHODS

Archival paraffin-embedded tissues from 37 patients with TCC were analysed by immunohistochemistry to determine Fas and FasL expression.

RESULTS

Fas and FasL were detected on the cell surface and cytoplasm of respectively 34 (92%) and all cases analysed. The expression of Fas and FasL did not differ with the cytological grade of TCC.

CONCLUSION

The high expression of FasL in TCC, reported for the first time in the present study, suggests that FasL may contribute to the immune escape of TCC through killing Fas-bearing lymphocytes. Co-expression of Fas with FasL also suggests that TCC may have pathways resistant to Fas-mediated autocrine cell suicide.

Apoptosis in Helicobacter pylori-associated gastric and duodenal ulcer disease is mediated via the Fas antigen pathway

Increased mucosal apoptosis is seen in H. pylori-infected gastric tissue; however, the precise mechanism by which this organism triggers programmed cell death is poorly understood and is investigated in this study. One pathway for induction of apoptosis is the Fas Ag pathway. Normal gastric and small bowel tissue express low levels of Fas antigen and nondetectable levels of Fas ligand. Consequent to H. pylori infection, there is elevated expression of Fas antigen in mucosal cells concurrent with Fas ligand expressing lymphocytes. This prompted us to investigate the potential role of Fas in mediating H. pylori-related apoptosis. It has been shown that inflammatory cytokines are abundant in H. pylori-infected tissue and that cytokines regulate the expression of Fas Ag in various tissue types. Using cell culture, we examine the role of specific inflammatory cytokines in activating this pathway. This communication presents the first evidence to implicate the Fas pathway in mediating apoptosis in H. pylori-associated gastric and duodenal ulcer disease.

Pancreatic cancer cells can evade immune surveillance via nonfunctional Fas (APO-1/CD95) receptors and aberrant expression of functional Fas ligand

BACKGROUND

The Fas (APO-1/CD95) receptor/Fas ligand (FasR/FasL) system plays a key role in immune surveillance. We investigated the possibility of a tumor escape mechanism involving the FasR/FasL system in pancreatic cancer cells.

METHODS

Fourteen pancreatic cancer cell lines and 3 pancreatic cancer surgical specimens were studied for their expression of FasR and FasL by flow cytometry, immunoblotting, and immunohistochemistry, FasR function was tested with an anti-FasR antibody. FasL function was assessed by coculture assays using pancreatic cancer cells and FasR-sensitive Jurkat T-cells.

RESULTS

FasR was expressed in normal pancreas, in 14 of 14 pancreatic cancer cell lines, and in 3 of 3 surgical specimens. However, only 1 of 14 cancer cell lines expressed functional FasR when grown in monolayer, although 3 additional cell lines displayed functional FasR when cultured in suspension. Normal pancreas did not express FasL, whereas 14 of 14 cancer cell lines and 3 of 3 surgical specimens expressed FasL. FasL expressed by pancreatic cancer cells mediated killing of Jurkat T-cells in coculture assays (P < .005).

CONCLUSIONS

These data suggest that pancreatic cancer cells have 2 potential mechanisms of evading Fas-mediated immune surveillance. A nonfunctional FasR renders them resistant to Fas-mediated apoptosis. The aberrant expression of functional FasL allows them to "counterattack" activated Fas-sensitive T-cells. Alone or in unison, these tumor escape mechanisms may contribute to the malignant and often rapid course of pancreatic cancer disease.

Human myeloma cell apoptosis induced by interferon-alpha

Although there have been reports regarding the clinical effectiveness of IFN alpha in the treatment of myeloma patients during this decade, its biological effects on human myeloma cells have still not been clarified. Recently, apoptosis has been considered as one of the most important mechanisms in the programmed cell death of malignant tumour cells induced by chemotherapeutic agents or cytotoxic immunological defence in malignancy-carrying hosts. Among the several pathways which function to induce apoptosis, Fas and the Fas ligand system have been thought to play an important role in inducing tumour-cell apoptosis, particularly in immunological prevention. In this study we investigated myeloma cell apoptosis induced by IFN alpha using five human myeloma cell lines which were established without any additional supplementation of IL-6. In addition, the mRNA expression levels of apoptosis-related genes employing the reverse transcriptase-polymerase chain reaction (RT-PCR) were also analysed with the KMS-12-PE cell line, which was the most sensitive of the five cell lines in terms of apoptosis induced by IFN alpha. Based on the results, it was determined that IFN alpha induced myeloma cell apoptosis in a dose-dependent manner, but the sensitivity to IFN alpha in the cell lines examined varied and one cell line revealed growth stimulation by IFN alpha. In addition, the apoptosis induced by IFN alpha did not seem to be mediated by the Fas/Fas ligand pathway. Finally, the IL-6, IL-6R, IRF1 and IRF2 genes were up-regulated in KMS-12-PE cells cultured with IFN alpha. Therefore these genes may play an important role during apoptosis induced by IFN alpha.

Pre-operative radio-chemotherapy enhances apoptotic cell death in oral squamous cell carcinoma

The effect of pre-operative radio-chemotherapy (RCT) has been examined in a total of 15 oral squamous cell carcinomas (SCCs), in terms of apoptosis (cell loss) and proliferation. All the patients received pre-operative radiation at a dosage of 30 or 40 Gy, as well as anticancer agents including tagaful (FT), 5-fluorouracil (5-FU), bleomycin (BLM) and peplomycin (PEP). Surgical specimens were obtained before and after RCT, and serial sections were prepared for immunohistochemistry for p53 oncoprotein and Ki-67 antigen, as well as for terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL). TUNEL indices (TI; percentage of TUNEL-positive cells in the tumor cells) before and after RCT were 1.2+/-1.1 and 4.7+/-2.9 in the nine well-differentiated oral SCCs, and 1.0+/-0.7 and 3.9+/-2.1 in the six poorly differentiated SCCs, respectively. Similarly, Ki-67 indices (KI; percentage of Ki-67 antigen-positive cells in tumor cells) before and after RCT were 31.1+/-14.2 and 15.8+/-11.1 in the former, and 37.1+/-7.8 and 8.7+/- 13.4 in the latter, respectively. Thus, pre-operative RCT enhanced apoptotic cell death and abated proliferative activity significantly (P<0.05), regardless of histological differentiation. Enhancement of apoptosis was more prominent in the group treated with FT or 5-FU than with BLM or PEP. Oral SCC with >20% of nuclear p53-positive tumor cells was noted in six cases. Enhanced TI and abadement of KI did not differ among the p53-positive and -negative tumors.