Growth inhibition and apoptosis induction of Sulindac on Human gastric cancer cells

Molecular mechanisms underlying the action of carcinogens in gastric cancer with a glimpse into targeted therapy

BACKGROUND

Gastric cancer imposes a substantial global health burden despite its overall incidence decrease. A broad spectrum of inherited, environmental and infectious factors contributes to the development of gastric cancer. A profound understanding of the molecular underpinnings of gastric cancer has lagged compared to several other tumors with similar incidence and morbidity rates, owing to our limited knowledge of the role of carcinogens in this malignancy. The International Agency for Research on Cancer (IARC) has classified gastric carcinogenic agents into four groups based on scientific evidence from human and experimental animal studies. This review aims to explore the potential comprehensive molecular and biological impacts of carcinogens on gastric cancer development and their interactions and interferences with various cellular signaling pathways.

CONCLUSIONS

In this review, we highlight recent clinical trial data reported in the literature dealing with different ways to target various carcinogens in gastric cancer. Moreover, we touch upon other multidisciplinary therapeutic approaches such as surgery, adjuvant and neoadjuvant chemotherapy. Rational clinical trials focusing on identifying suitable patient populations are imperative to the success of single-agent therapeutics. Novel insights regarding signaling pathways that regulate gastric cancer can potentially improve treatment responses to targeted therapy alone or in combination with other/conventional treatments. Preventive strategies such as control of H. pylori infection through eradication or immunization as well as dietary habit and lifestyle changes may reduce the incidence of this multifactorial disease, especially in high prevalence areas. Further in-depth understanding of the molecular mechanisms involved in the role of carcinogenic agents in gastric cancer development may offer valuable information and update state-of-the-art resources for physicians and researchers to explore novel ways to combat this disease, from bench to bedside. A schematic outlining of the interaction between gastric carcinogenic agents and intracellular pathways in gastric cancer H. pylori stimulates multiple intracellular pathways, including PI3K/AKT, NF-κB, Wnt, Shh, Ras/Raf, c-MET, and JAK/STAT, leading to epithelial cell proliferation and differentiation, apoptosis, survival, motility, and inflammatory cytokine release. EBV can stimulate intracellular pathways such as the PI3K/Akt, RAS/RAF, JAK/STAT, Notch, TGF-β, and NF-κB, leading to cell survival and motility, proliferation, invasion, metastasis, and the transcription of anti-apoptotic genes and pro-inflammatory cytokines. Nicotine and alcohol can lead to angiogenesis, metastasis, survival, proliferation, pro-inflammatory, migration, and chemotactic by stimulating various intracellular signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, ROS, and JAK/STAT. Processed meat contains numerous carcinogenic compounds that affect multiple intracellular pathways such as sGC/cGMP, p38 MAPK, ERK, and PI3K/AKT, leading to anti-apoptosis, angiogenesis, metastasis, inflammatory responses, proliferation, and invasion. Lead compounds may interact with multiple signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, DNA methylation-dependent, and epigenetic-dependent, leading to tumorigenesis, carcinogenesis, malignancy, angiogenesis, DNA hypermethylation, cell survival, and cell proliferation. Stimulating signaling pathways such as PI3K/Akt, RAS/RAF, JAK/STAT, WNT, TGF-β, EGF, FGFR2, and E-cadherin through UV ionizing radiation leads to cell survival, proliferation, and immortalization in gastric cancer. The consequence of PI3K/AKT, NF-κB, Ras/Raf, ROS, JAK/STAT, and WNT signaling stimulation by the carcinogenic component of Pickled vegetables and salted fish is the Warburg effect, tumorigenesis, angiogenesis, proliferation, inflammatory response, and migration.

Targeting multidrug resistance-associated protein 1 (MRP1)-expressing cancers: Beyond pharmacological inhibition

Resistance to chemotherapy remains one of the most significant obstacles to successful cancer treatment. While inhibiting drug efflux mediated by ATP-binding cassette (ABC) transporters is a seemingly attractive and logical approach to combat multidrug resistance (MDR), small molecule inhibition of ABC transporters has so far failed to confer clinical benefit, despite considerable efforts by medicinal chemists, biologists, and clinicians. The long-sought treatment to eradicate cancers displaying ABC transporter overexpression may therefore lie within alternative targeting strategies. When aberrantly expressed, the ABC transporter multidrug resistance-associated protein 1 (MRP1, ABCC1) confers MDR, but can also shift cellular redox balance, leaving the cell vulnerable to select agents. Here, we explore the physiological roles of MRP1, the rational for targeting this transporter in cancer, the development of small molecule MRP1 inhibitors, and the most recent developments in alternative therapeutic approaches for targeting cancers with MRP1 overexpression. We discuss approaches that extend beyond simple MRP1 inhibition by exploiting the collateral sensitivity to glutathione depletion and ferroptosis, the rationale for targeting the shared transcriptional regulators of both MRP1 and glutathione biosynthesis, advances in gene silencing, and new molecules that modulate transporter activity to the detriment of the cancer cell. These strategies illustrate promising new approaches to address multidrug resistant disease that extend beyond the simple reversal of MDR and offer exciting routes for further research.

Targeting molecular signal transduction pathways in hepatocellular carcinoma and its implications for cancer therapy

Hepatocellular carcinoma is a substantial health concern. It is currently the third dominating cause of mortality associated with cancer worldwide. The development of hepatocellular carcinoma is an intricate process that encompasses the impairment of genetic, epigenetic, and signal transduction mechanisms contributing to an aberrant metabolic system, enabling tumorigenesis. Throughout the past decade, research has led to the revelation of molecular pathways implicated in the progression of this notorious disorder. The altered signal transduction pathways, such as the mitogen-activated protein kinase pathway, phosphoinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway, WNT/β-catenin pathway, hepatocyte growth factor/c-MET pathway, and just another kinase/signal transducers and activators of transcription signaling pathway is of much therapeutic significance, as targeting them may avail to revert, retard or avert hepatocarcinogenesis. The present review article sums up the contemporary knowledge of such signaling mechanisms, including their therapeutic targets and betokens that novel and efficacious therapies can be developed only by the keen understanding of their character in hepatocarcinogenesis. In additament, we address the role of consequential therapeutic agents and preclinical nondrug therapies known for combating hepatocarcinogenesis.

Differentiation by NK cells is a prerequisite for effective targeting of cancer stem cells/poorly differentiated tumors by chemopreventive and chemotherapeutic drugs

Natural Killer (NK) cells target oral, pancreatic, lung, breast, glioblastoma and melanoma stem-like/poorly differentiated tumors. Differentiation of the abovementioned tumors with supernatants from split-anergized NK cells decreases their susceptibility to NK cells, but increases their sensitivity to cisplatin (CDDP)-mediated cell death. Breast and melanoma tumor cells with CD44 knockdown display enhanced susceptibility to NK cell-mediated lysis, potentially due to decreased differentiation. We also demonstrate that sulindac, a non-steroidal anti-inflammatory drug and a chemopreventive agent, not only limits the growth of oral tumor cells, but also aids in cancer cell elimination by NK cells. Treatment of oral tumors with sulindac, but not adriamycin inversely modulates the expression and function of NFκB and JNK, resulting in a significant down-regulation of IL-6, and VEGF secretion by oral tumor cells. In addition, increased secretion of IL-6 and VEGF is blocked by sulindac during interaction of oral tumors with NK cells. Sulindac treatment prevents synergistic induction of VEGF secretion by the tumor cells after their co-culture with untreated NK cells since non-activated NK cells lack the ability to efficiently kill tumor cells. Moreover, sulindac is able to profoundly reduce VEGF secretion by tumor cells cultured with IL-2 activated NK cells, which are able to significantly lyse the tumor cells. Based on the data presented in this study, we propose the following combinatorial approach for the treatment of stem-like/ poorly differentiated tumors in cancer patients with metastatic disease. Stem-like/ poorly differentiated tumor cells may in part undergo lysis or differentiation after NK cell immunotherapy, followed by treatment of differentiated tumors with chemotherapy and chemopreventive agents to eliminate the bulk of the tumor. This dual approach should limit tumor growth and prevent metastasis.

Synthesis and biological evaluation of betulonic acid derivatives as antitumor agents

Structural modification was performed at the C-28 position of betulonic acid (BetA). Twenty-five BetA derivatives were synthesized, and evaluated for their antitumor activities against MGC-803, PC3, Bcap-37, A375, and MCF-7 human cancer cell lines by MTT assay. Among the derivatives, most of the derivatives had significant antiproliferative ability (IC50 < 19 μM). Compound 3k, the most active compound, showed IC50 values of 3.6, 5.6, 4.2, 7.8, and 5.2 μM on the five cancer cell lines respectively, and was selected to investigate cell apoptosis by subsequent florescence staining and flow cytometry analysis. The results revealed that compound 3k could induce apoptosis in MGC-803 cell lines, and the apoptosis ratios reached 28.33% after 36 h of treatment at 10 μM. In addition, the study of cancer cell apoptotic signaling pathway indicated that the apoptosis of MGC-803 cells induced by compound 3k could be through the mitochondrial intrinsic pathway.

Thiram activates NF-kappaB and enhances ICAM-1 expression in human microvascular endothelial HMEC-1 cells

Thiram (TMTD) is a fungicidal and bactericidal agent used as antiseptic, seed disinfectant and animal repellent. In the light of known properties, thiram is considered to be used as an inhibitor of angiogenesis and/or inflammation. Since angiogenesis requires the growth of vascular endothelial cells we have used microvascular endothelial cell line HMEC-1 to elucidate the effect of thiram on normal and stimulated cells. We cultured HMEC-1 cells in the presence of thiram at low concentration (0.5 µg/mL or 2 µg/mL) (0.2 µM or 0.8 µM) or TNF-α (10 ng/mL) alone, and thiram together with TNF-α. TNF-α was used as a cytokine that triggers changes characteristic for inflammatory state of the cell. We carried out an in vitro study aimed at assessing generation of reactive oxygen species (ROS), activation of NF-κB, and expression of cell adhesion molecules ICAM-1, VCAM-1, PECAM-1. It was found that TMTD produced ROS and activated NF-κB. Activation of NF-κB was concurrent with an increase in ICAM-1 expression on the surface of HMEC-1 cells. ICAM-1 reflects intensity of inflammation in endothelial cell milieu. The expression of VCAM-1 and PECAM-1 on these cells was not changed by thiram. It was also found that stimulation of the HMEC-1 cells with the pro-inflammatory cytokine TNF-α caused activation of ICAM-1 and VCAM-1 expression with concomitant decrease of PECAM-1 cell surface expression above the control levels. Treatment with thiram and TNF-α changed cellular response compared with effects observed after treatment with TNF-α alone, i.e. further increase of ICAM-1 expression and impairment of the TNF-α effect on PECAM-1 and VCAM-1 expression. This study demonstrated that thiram acts as a pro-oxidant, and elicits in endothelial cell environment effects characteristic for inflammation. However, when it is present concurrently with pro-inflammatory cytokine TNF-α interferes with its action.

Bortezomib inhibits gastric carcinoma HGC-27 cells through the phospho-Jun N-terminal kinase (p-JNK) pathway in vitro

The study is designed to explore the anticancer mechanism of Bortezomib. The effects of Bortezomib on the proliferation of human gastric cancer cells HGC-27 and expression levels of the phospho-Jun N-terminal kinase (p-JNK) pathway-related proteins in vitro were investigated. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that the Bortezomib significantly decreased the viability of HGC-27 cells and induced apoptosis. Western blot showed that the Bortezomib strongly increased the levels of p-JNK, caspase-3, PARP, and bax proteins while it increased the level of bcl-2. However, SP600125 can significantly decrease antitumour effects of Bortezomib in HGC-27 cells. It can be concluded that Bortezomib has significant inhibitory effects on the growth of HGC-27 cells. The effect may be achieved partly via upregulating JNK pathway and its down-stream apoptosis-related proteins. Therefore, Bortezomib may be beneficial in gastric carcinoma treatment.

A review of the anticancer potential of the antimalarial herbal cryptolepis sanguinolenta and its major alkaloid cryptolepine

Cryptolepis sanguinolenta (Lindl.) Schltr (Periplocaceae), has a longstanding traditional use in the treatment of malaria in the West African region. Recent evidence suggests that the aqueous extract from the roots and the major alkaloid from the plant, cryptolepine, have prospects as cancer chemotherapeutic agents on account of their potent cytotoxicity to mammalian cells. Several mechanisms have been proposed to explain the cytotoxic activities of the agents. However, emerging evidence from their anti-inflammatory actions suggest that the mechanism of the cytotoxicity may be closely related to its anti-inflammatory activity. This review looks at the mechanisms of cryptolepis-induced cytotoxicity, its link with inflammation and its potential as anticancer agent. The elucidation of these interwoven mechanisms may be useful in the development of cryptolepine or other analogues as new anticancer agents.

Discovery and antitumor activities of constituents from Cyrtomium fortumei (J.) Smith rhizomes

Background

Cyrtomium fortumei (J.) Smith is an important Chinese herbal medicine because of its biological functions. However, systematic and comprehensive studies on the phytochemicals from Cyrtomium fortumei (J.) Smith and their bioactivity are limited.

Results

Using the bioassay-guided technique, the ethyl acetate and n-BuOH extracts of the rhizomes of Cyrtomium fortumei (J.) Smith were shown to exhibit good antitumor activities, consequently leading to the isolation of 23 compounds. All compounds were isolated from the plant for the first time. The inhibitory activities of these compounds were investigated on tumor cells MGC-803, PC3, and A375 in vitro by MTT (thiazolyl blue tetrazolium bromide) assay, and the results showed that pimpinellin (3) had potent cytotoxic activities against the three cell lines, with the IC₅₀ values of 14.4 ± 0.3 μM, 20.4 ± 0.5 μM, and 29.2 ± 0.6 μM, respectively. The mechanism of the antitumor action indicated that pimpinellin inhibited the growth of MGC-803 cells via the induction of tumor cell apoptosis, with apoptosis ratio of 27.44% after 72 h of treatment at 20 μM.

Conclusions

This study suggests that most of the compounds from the roots of Cyrtomium fortumei (J.) Smith could inhibit the growth of human carcinoma cells. Moreover, pimpinellin inhibited the growth of tumor cells via the induction of tumor cell apoptosis.

Effect of celecoxib on E-cadherin, VEGF, Microvessel density and apoptosis in gastric cancer

Cyclooxygenase-2 (COX-2) plays a crucial role in the development and invasion of gastric cancer. COX-2 inhibitors have been shown to be chemopreventive against gastrointestinal cancers. In vitro studies have suggested that the mechanisms may be related to induction of apoptosis and inhibition of angiogenesis. COX-2 may also have impact on E-cadherin. In our study we investigate the effect of Celecoxib on expression of E-cadherin and serum soluble E-cadherin, as well as on apoptosis and angiogenesis in patients with gastric cancer. Fifty nine gastric cancer patients were randomly divided into two groups: Surgery group (n = 22), in which patients underwent surgical resection after diagnosis, and Celecoxib + Surgery group (n = 37), in which patients received oral Celecoxib 200 mg twice daily for 7 days before curative resection. Twenty healthy subjects (Healthy controls) were recruited as normal controls. After curative resection, COX-2, E-cadherin, VEGF, and MVD were detected by immunohistochemistry. Serum soluble E-cadherin was quantitatively measured using a commercially available enzyme-linked immunosorbent assay kit. Apoptosis was determined by TUNEL assay. Significantly decreased expression of COX-2, increased E-cadherin and apoptosis, decreased VEGF and MVD were observed in gastric cancer tissues from patients receiving Celecoxib compared to Surgery group. Compared to Healthy controls, the serum soluble E cadherin levels were higher in gastric cancer patients which were decreased by Celecoxib. This in vivo study demonstrated that Celecoxib induces apoptosis and inhibit angiogenesis of gastric cancer. Its impact on E-cadherin may suggest that this agent may suppress the invasion of advanced gastric cancer.

Survivin depletion preferentially reduces the survival of activated K-Ras-transformed cells

To identify cancer-specific targets, we have conducted a synthetic lethal screen using a small interfering RNA (siRNA) library targeting ∼4,000 individual genes for enhanced killing in the DLD-1 colon carcinoma cell line that expresses an activated copy of the K-Ras oncogene. We found that siRNAs targeting baculoviral inhibitor of apoptosis repeat-containing 5 (survivin) significantly reduced the survival of activated K-Ras-transformed cells compared with its normal isogenic counterpart in which the mutant K-Ras gene had been disrupted (DKS-8). In addition, survivin siRNA induced a transient G2-M arrest and marked polyploidy that was associated with increased caspase-3 activation in the activated K-Ras cells. These results indicate that tumors expressing the activated K-Ras oncogene may be particularly sensitive to inhibitors of the survivin protein. [Mol Cancer Ther 2007;6(1):269–76]

Cyclo-oxygenase 2 expression impairs serum-withdrawal-induced apoptosis in liver cells

We have investigated the mechanism of COX-2 (cyclo-oxygenase 2)-dependent inhibition of apoptosis in liver, a key pathway underlying proliferative actions of COX-2 in liver cancers, cirrhosis, chronic hepatitis C infection and regeneration after partial hepatectomy. Stable expression of COX-2 in CHL (Chang liver) cells induced proliferation, with an increase in the proportion of cells in S-phase, but no other significant changes in cell-cycle distribution. This was associated with a marked inhibition of the apoptotic response to serum deprivation, an effect mimicked by treating empty-vector-transfected control cells (CHL-V cells) with prostaglandin E2 and prevented in COX-2-expressing cells (CHL-C cells) treated with selective inhibitors of COX-2. Serum-deprived CHL-V cells displayed several indicators of activation of intrinsic apoptosis: caspases 9 and 3 activated within 6 h and caspase 8 within 18 h, Bax expression was induced, cytochrome c was released to the cytosol, and PARP-1 [poly(ADP-ribose) polymerase 1] cleavage was evident in nuclei. COX-2 expression blocked these events, concomitant with reduced expression of p53 and promotion of Akt phosphorylation, the latter indicating activation of survival pathways. CHL cells were resistant to stimulation of the extrinsic pathway with anti-Fas antibody. Moreover, in vivo expression of GFP (green fluorescent protein)-labelled COX-2 in mice by hydrodynamics-based transient transfection conferred resistance to caspase 3 activation and apoptosis induced by stimulation of Fas.

Non-steroidal anti-inflammatory drugs in prevention of gastric cancer

Non-steroidal anti-inflammatory drugs (NSAIDs) including cyclooxygenase 2 (COX-2) selective inhibitors, are potential agents for the chemoprevention of gastric cancer. Epidemiological and experimental studies have shown that NSAID use is associated with a reduced risk of gastric cancer although many questions remain unanswered such as the optimal dose and duration of treatment. The possible mechanisms for the suppressor effect of NSAIDs on carcinogenesis are the ability to induce apoptosis in epithelial cells and regulation of angiogenesis. Both COX-dependent and COX-independent pathways have a role in the biological activity of NSAIDs. Knowledge of how NSAIDs prevent neoplastic growth will greatly aid the design of better chemopreventive drugs and novel treatments for gastric cancer.

A phase I clinical and pharmacokinetic study of the multi-drug resistance protein-1 (MRP-1) inhibitor sulindac, in combination with epirubicin in patients with advanced cancer

PURPOSE

Multi-drug resistance mediated by ATP-binding cassette trans-membrane protein pumps is an important cause of cancer treatment failure. Sulindac has been shown to be a competitive substrate for the clinically important resistance protein, multi-drug resistance protein-1 (MRP-1), and thus might enhance the anti-cancer activity of substrate chemotherapeutic agents, e.g. anthracyclines.

METHODS

We conducted a dose-escalating, single arm, prospective, open label, non-randomised phase I trial of epirubicin (75 mg/m(2)) in combination with escalating oral doses of sulindac (0-800 mg) in patients with advanced cancer to identify an appropriate dose of sulindac to use in future resistance studies. Anthracycline and sulindac pharmacokinetics were studied in cycles 1 and 3.

RESULTS

Seventeen patients (8 breast, 3 lung, 2 bowel, 1 melanoma, 1 renal, 1 ovarian and 1 of unknown primary origin, 16/17 having had prior chemotherapy) were enrolled. Eight patients received a full six cycles of treatment; 14 patients received three or more cycles. Dose-limiting toxicity was observed in two patients at 800 mg sulindac (1 renal impairment, 1 fatal haemoptysis in a patient with advanced lung cancer), and sulindac 600 mg was deemed to be the maximum tolerated dose. Sulindac had no effect on epirubicin pharmacokinetics. Among 15 patients with evaluable tumour, two partial responses were seen (malignant melanoma and breast cancer). Four others had prolonged stable disease.

CONCLUSION

Epirubicin 75 mg/m(2) and sulindac 600 mg are the recommended doses for phase II studies for these agents in combination.

Expression of COX-2 and P16 protein and their correlations in various types of gastric polyps and gastric cancer cell

AIM: To explore the expression of COX-2 and P16 in various types of gastric polyps and gastric cancer cell, and to investigate the relationship between COX-2 and P16 protein in the process of gastric cancer.

METHODS: The expression of COX-2 and P16 proteins were detected in normal gastric mucosa (n = 10), non-tumor gastric polyps (n = 30, inflammatory polyps and hyperplastic polyps), tumor gastric polyps (n = 20, adenomatous polyps), and gastric cancer (n = 40) by S-P immunohistochemical staining.

RESULTS: In the normal gastric mucosa, non-tumor gastric polyps, tumor gastric polyps, and gastric cancer cell, the expression rate of the COX-2 was 10%, 13.33%, 45%, and 75%, respectively; and the rate of P16 protein expression in those tissues was 90%, 86.67%, 60%, and 32.5%, respectively. The positive rates of COX-2 and P16 protein were both significantly different between gastric cancer and other tissues (P <0.05). The expression of COX-2 and P16 were associated with the differentiation degree of gastric cancer and lymph node metastasis. COX-2 expression was negatively related to P16 expression in gastric cancer (P <0.05).

CONCLUSION: COX-2 and P16 protein play key roles in the development of gastric cancer, and can be used as important indexes in the research of the biological behavior of gastric cancer.

Apoptotic and anti-angiogenic strategies in liver and gastrointestinal malignancies

Inappropriate suppression of apoptosis is strongly implicated in tumorigenesis. Tumor development is heralded by the mutation of tumor suppressor genes and overexpression of anti-apoptotic genes permitting cell survival. Thus, inducing the apoptotic process in various ways can be applied to cancer management. Besides, angiogenesis is a crucial process for tumor growth and metastasis. New strategies targeting fundamental play-markers of the angiogenic process are currently under investigation.

The role of prostaglandins and other eicosanoids in the gastrointestinal tract

Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally prescribed to ameliorate symptoms associated with acute pain and chronic inflammatory diseases such as arthritis. Recent epidemiologic studies and clinical trials indicate that use of NSAIDs and cyclooxygenase (COX)-2 selective inhibitors are associated with a reduced risk of certain malignancies, especially gastrointestinal cancer. The cyclooxygenase enzymes are the best known targets of NSAIDs; this diverse class of compounds blocks conversion of arachidonic acid to prostanoids. Prostaglandins and other eicosanoids derived from COX-1 and COX-2 are involved in a variety of physiologic and pathologic processes in the gastrointestinal tract. Recent efforts to identify the molecular mechanisms by which COX-2-derived prostanoids exert their proneoplastic effects have provided a rationale for the possible use of NSAIDs alone or in a combination with conventional or experimental anticancer agents for the treatment or prevention of gastrointestinal cancers.

Apoptosis of human gastric cancer SGC-7901 cells induced by mitomycin combined with sulindac

AIM: To investigate the effects of mitomycin (MMC) combined with sulindac on cell viability, apoptotic induction and expression of apoptosis-related gene Bcl-2 and cyclooxygenase-2 (COX-2) in gastric cancer SGC-7901 cells.

METHODS: Human gastric cancer SGC-7901 cells were divided into three treatment groups,namely sulindac treatment group, MMC treatment group and combined sulindac with MMC treatment group. After being treated with drugs, cell viability was examined by MTT assay. Flow cytometry was used to evaluate the cell cycle distribution and apoptotic rates. Morphology of the cells was observed under light microscope and interactive laser microscope. Expression of COX-2 and Bcl-2 was determined by immunocytochemical method.

RESULTS: After exposure for 12 h to three kinds of drugs, gastric cancer SGC-7901 cells presented some morphological features of apoptosis, including cell shrinkage, nuclear condensation, DNA fragmentation and formation of apoptotic bodies. Growth inhibition was more obvious in combined sulindac with MMC treatment group and sulindac treatment group than in MMC treatment group. The apoptotic rates in co-treated cells and MMC-treated cells 24 h after treatment were 12.0% and 7.2%, respectively. After exposure for 24 h to MMC, the expression of COX-2 and Bcl-2 protein was up-regulated, COX-2 levels were down-regulated but Bcl-2 gene expression was not changed significantly in combined treatment group.

CONCLUSION: MMC-induced apoptosis is reduced by up-regulating the expression of COX-2 and Bcl-2 genes. MMC combined with sulindac can suppress the growth of gastric cancer cells through induction of apoptosis mediated by down-regulation of apoptosis-related Bcl-2 and COX-2 gene.

Effects of quercetin combined with cisplatin on proliferation and apoptosis of human gastric cancer SGC-7901 cells

AIM: To investigate the effects of quercetin combined with cisplatin on the proliferation and apoptosis of, and the expression of apoptosis-related gene Bcl-X_L in human gastric cancer SGC-7901 cells.

METHODS: After treated with quercetin (QU), cisplatin (DDP) or both (QU-DDP), the viability of SGC-7901 cells was evaluated by MTT assay. Cell cycle distribution and apoptosis were detected by flow cytometry. Cell morphology was examined under light microscope and electron microscope. The expression of Bcl-X_L mRNA was detected by the reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: After exposure to different drugs for 24 h, SGC-7901 cells manifested typical morphological features of apoptosis. Both DDP and QU inhibited the proliferation and induced the apoptosis of SGC7901 cells in a time and concentration-dependent manner. QU combined with DDP synergistically enhanced cell death. The apoptosis was more pronounced in cells treated with both drugs (QU: 1 mmol/L, DDP: 80 mmol/L) than DDP alone (80 mmol/L) (19.930.07 vs 5.160.11, P<0.01). After exposure to DDP for 48 h, Bcl-X_L mRNA expression was down-regulated, which was promoted by QU.

CONCLUSION: QU combined with DDP effectively inhibits proliferation and induces apoptosis of the human gastric cancer SGC-7901 cells in vitro in a dose-dependent manner.

Relationship between bcl-2 gene expression and cell proliferation and apoptosis in human gastric carcinomas

AIM: To investigate the relationship between bcl -2 gene expression levels in human gastric carcinoma and the frequency of tumor cell proliferation activity and apoptosis.

METHODS: In situ hybridization and immunohistochemistry methods were used to study the frequencies of expressions of bcl -2 gene and nuclear antigen of proliferating cells (PCNA) in 53 gastric carcinomas. Meanwhile, an in situ apoptotic cell detection (TUNEL method) was adopted to compare the number of apoptotic cells and PCNA with the Bcl -2 protein expression in each case.

RESULTS: Of the 53 gastric carcinomas, 41 and 43 expressed bcl -2 mRNA and Bcl -2 protein, which were count for 77.4% and 81.1% respectively. There was no significant difference between the positive rates obtained by these two methods. The apoptotic index of gastric carcinomas negatively related to PCNA index (r = -0.993, P < 0.01). With the increase of Bcl-2 protein expression , the cell proliferating activity increased but the apoptosis decreased in the tumor cells. Significant difference of cell proliferation and apoptosis existed between +++ group and ++ group of Bcl -2 protein expression (t = 2.552, 2.699, P < 0.05) as well as between the former two groups and the -, + group (t = 4.487, 3.975, 2.807, 3.094, 4.885, 5.816, 3.404, 3.895, P < 0.01) respectively.

CONCLUSION: The overexpression of bcl -2 gene inhibits cell apoptosis and excessive cell proliferation in the development and progress of gastric carcinomas.

Helicobacter pylori and molecular mechanisms of gastric carcinogenesis: targets for prevention and therapy

Gastric cancer is still a leading cause of cancer death worldwide. It is frequently diagnosed in an advanced stage and the overall prognosis is dismal. A major improvement will only be reached with a better understanding of the genetic changes underlying gastric cancer, which may provide us with effective prevention and treatment strategies. This review will highlight the present knowledge on the role of Helicobacter pylori in gastric carcinogenesis and the molecular pathogenesis of gastric cancer, as well as provide a brief overview of possible future targets for more specific and successful treatment options.

Expression of COX-2 in gastric mucosa of atrophic gastritis caused by hot high-salt water in rats

AIM: To measure the expression of COX-2 in gastric mucosa of chronic atrophic gastritis (CAG) caused by hot high-salt water in rats and to study the pathogenesis of atrophic gastritis caused by hot high-salt diet.

METHODS: The atrophic gastritis rat model was made by hot high-salt water ig perfusion. The expression of COX-2 in gastric mucosa in 4, 8, 12, and 32 wk was detected by immunohistochemical method and the PEG2 levels were tested by ELISA.

RESULTS: All the model group rats formed CAG at the end of 12 wk with the following pathological changes of CAG under microscope, such as thin mucosa layer, thick muscle layer, decreased glands, and infiltration of inflammatory cells. With the time prolonging, the atrophy of gastric mucosa became more seriously. There was little or no expression of COX-2 in gastric mucosa in normal control group. While in hot high-salt water perfusion group, there was a little expression from the 8^th wk, and over expression in 12^th wk. There was a significant difference between the two groups (4.5%±2.1% vs 14.7%±5.7%, P < 0.05). The expression of COX-2 increased with the time and it reached the peak value in the 32^th wk. The PEG2 levels in hot high-salt water perfusion group increased in the 12^th wk. There was a significant difference between the two groups (125.6±21.2 ng/g vs 188.4±37.6 ng/g, P < 0.05), and it reached the peak value in the 32^th wk.

CONCLUSION: COX-2 plays an important role in the formation of atrophic gastritis and and alteration of diet habition may help prevent the formation of atrophic gastritis and gastric cancer.

Effects of COX-2 inhibitor with cisplatin on proliferation and apoptosis of pancreatic cancer cells

AIM: To investigate the effects of proliferation and apoptosis induced by cyclooxygenase-2 (COX-2) inhibitor celecoxib in combination with cisplatin.

METHODS: The human pancreatic cancer cell line BxPC-3 cells were treated with COX-2 inhibitors celecoxib and cisplatin. The cell relative viability was examined using 3 (4, 5-dimethylethiazoly 1-2-) 2, 5-diphonyl tetrazolium bromide (MTT) assays. the expression of COX-2 mRNA was detected by RT-PCR, flow cytometry and Hoechst-33258 were used to demonstrate apoptotic changes in celecoxib and cisplatin treated cells.

RESULTS: After treatment of BxPC-3 cells with celecoxib, as measured by MTT, cell viability was inhibited in a dose-dependent and time-dependent manner with an IC50 of 100 nM at the time of 24h. The expression of COX-2 mRNA could be significantly decreased by celecoxib. Furthermore, we demonstrated that the combination of celecoxib with cisplatin inhibited cell growth and induced cell apoptosis to a greater degree than either compound alone. The apoptotic morphologies were demonstrated by Hoechst-33 258.

CONCLUSION: Combination of celecoxib with cisplatin inhibits cell proliferation and induces cell apoptosis, and the potent effectiveness of celecoxib in combination with gemcitabine may hold a promise in the clinical treatment of pancreatic cancer.

Effects of indomethacin and/or casplatin on apoptosis of gastric cancer cells

AIM: To investigate the effects of indomethacin (IN) and casplain (CDDP) on apoptosis of gastric cancer cell line MGC803 and to provide the theoretic basis for gastric cancer therapy.

METHODS: Gastric cancer MGC803 cells were treated with IN and /or CDDP. Proliferation of the cells was detected by using MTT assay. Apoptosis of cells was measured by using fluorescence staining, and cell cycle kinetics by flow cytometry.

RESULTS: Both IN and CDDP were able to restrain the proliferation and induce apoptosis of the cells. There was dose-dependent and time-dependent cell proliferation induced by IN. High concentration of CDDP (10 mg/L) had also the time-effect, but a low dose of CDDP (0.1, 1 mg/L) did not. The percentage of apoptotic cells did not changed after 24h incubation with a low dose of CDDP. There also existed good dose-dependent and time-dependent effects when every concentration of CDDP combined with moderate dose IN (200 mmol/L). Low dose CDDP with IN had the similar effect to that of high dose CDDP alone.

CONCLUSION: IN and CDDP have the synergistic action when they work together on gastric cancer cell line MGC-803 and perhaps IN can antagonize the chemo-resistance of gastric cancer to other chemical drugs.

Inhibitory effects of celecoxib on proliferation of human liver and gastric carcinoma cells in vitro

AIM: To study the inhibitory effects of celecoxib on proliferation of human hepatoma SMMC-7721 cells and gastric cancer SGC-7901 cells in vitro.

METHODS: The two carcinoma cells were cultured with celecoxib at various concentrations(0, 20, 40, 80, 160 and 320 mmol/L). Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by transmission electron microscopy(TEM), and quantity of Cox-2 was evaluated by cytochemical staining.

RESULTS: The inhibition of proliferation on two carcinoma cells was observed(49.1% and 42.9% by 320 mmol/L celecoxib). The inhibitory effect was dose-dependent. Apoptotic cells were observed under transmission electron microscope. The different quantities of Cox-2 protein in cells were observed by cytochemical staining.

CONCLUSION: Celecoxib inhibits proliferation, induces apoptosis of human two carcinoma cells in vitro, and the effects have close relation to the quantities of Cox-2 protein in cells.

Apoptosis induced by mitomycin with sulindac on human gastric cancer cell SGC7901

AIM: To investigate the effects of mitomycin (MMC) with sulindac on the cell viability, apoptotic induction and expression of apoptosis-related gene Bcl-2 and cyclooxygenase-2 (COX-2) in gastric adenocarcinoma cell SGC7901.

METHODS: Human gastric cancer SGC7901 cells were divided into three groups, sulindac, MMC and sulindac with MMC. After treatment with drugs, cell viability was examined by MTT assay. Flow cytometry was used for the cell cycle distribution and apoptotic rates. The morphology of the cells was observed under light microscope and interactive laser cytometer. The expression of COX-2, Bcl-2 was determined by the immunocytochemical method.

RESULTS: After exposure for 12 h to three kinds of drugs, gastric cancer cells SGC7901 presented some morphologic features of apoptosis, including cell shrinkage, nuclear condensation, DNA fragmentation, formation of apoptotic bodies. The effects of growth inhibition were more obvious in cotreatment group with MMC and sulindac than MMC group. The apoptotic rates in cotreated cells and MMC-treated cells at 24 h after treatment were 12.0% and 7.2%, respectively. After exposure for 24 h to MMC, upregulation of COX-2 and Bcl-2 protein expression was noted, meanwhile, in cotreatment group, the levels of COX-2 were downregulated but the expression of Bcl-2 gene was not changed significantly.

CONCLUSION: MMC-induced apoptosis is reduced by upregulating the expression of COX-2 and Bcl-2 genes. MMC combined with sulindac can suppress growth of gastric cancer cells through induction of apoptosis which may be mediated by downregulation of apoptosis-related Bcl-2 gene and COX-2 gene.

Therapeutic mechanism of ginkgo biloba exocarp polysaccharides on gastric cancer

AIM: To study the therapeutic mechanism of Ginkgo biloba exocarp polysaccharides (GBEP) on gastric cancer.

METHODS: Thirty patients with gastric cancer were treated with oral GBEP capsules. The area of tumors was measured by electron gastroscope before and after treatment, then the inhibitory and effective rates were calculated. The ultrastructures of tumor cells were examined by transmissional electron microscope. Cell culture, MTT, flow cytometry were performed to observe proliferation, apoptosis and changes of relevant gene expression of human gastric cancer SGC-7901 cells.

RESULTS: Compared with the statement before treatment, GBEP capsules could reduce the area of tumors, and the effective rate was 73.4%. Ultrastructural changes of the cells indicated that GBEP could induce apoptosis and differentiation in tumor cells of patients with gastric cancer. GBEP could inhibit the growth of human gastric cancer SGC-7901 cells following 24-72 h treatment in vitro at 10-320 mg/L, which was dose- and time-dependent. GBEP was able to elevate the apoptosis rate and expression of c-fos gene, but reduce the expression of c-myc and bcl-2 genes also in a dose-dependent manner.

CONCLUSION: The therapeutic mechanism of GBEP on human gastric cancer may relate to its effects on the expression of c-myc, bcl-2 and c-fos genes, which can inhibit proliferation and induce apoptosis and differentiation of tumor cells.

Molecule action mechanisms of NM-3 on human gastric cancer SGC-7901 cells in vivo or in vitro

AIM: To study the molecule action mechanisms of NM-3 on the growth of human gastric cancer SGC-7901 cells in vivo or in vitro.

METHODS: SGC-7901 from human non-differentiated gastric cancer cell line was cultured with NM-3 at 100 mg/mL for 24 h. We observed its inhibitory rate and the density of micro-vascular growth in grafted mice with human gastric cancer SGC-7901. The apoptosis of human gastric cancer SGC-7901 was revealed in NM-3 treatment group by using terminal deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate-fluorescene nick end labeling (TUNEL) method and flow cytometry analysis.

RESULTS: The growth of SGC-7901 cells was markedly inhibited compared with control growp, which was smaller than that in normal saline control group (4.17 g ± 0.22 g vs 9.45 g ± 1.38 g, P < 0.01). The level of apoptosis of human gastric cell line SGC-7901 was obviously increased in NM-3 treatment group at 1 mg.L^-1 for 24 h. NM-3 inducing apoptotic index in NM-3 plus carboplatin group was 3.5 times that of carboplatin control group (TUNEL: 27.98% ± 6.12% vs 12.94% ± 2.12%, FACScan: 26.86% ± 5.69% vs 11.86% ± 1.09%, P < 0.01). Western blot analysis showed that the apoptotic index of human gastric cancer was elevated for 12, 24 and 36 h with an evident time-effect relationship in groups at 100 mg.L^-1. NM-3 enhanced the inhibitive effects and sensitivity of chemotherapy for human gastric cancer in nude mice. These results suggested that NM-3 played a key inhibitive role in the growth of grafted human gastric cancer in nude mice.

CONCLUSION: NM-3 can inhibit the growth of human gastric cancer cell line SGC-7901, and enhance the sensitivity of carboplatin on SGC-7901 and induced its apoptosis.

Expression of MTLC gene in gastric carcinoma

AIM: To investigate the expression of c-myc target from laryngeal cancer cells (MTLC) gene in gastric carcinoma (GC) tissues and the effect of MTLC over-expression on gastric carcinoma cell line BGC823.

METHODS: RT-PCR was performed to determine the expression of MTLC mRNA in GC and matched control tissues. BGC823 cells were transfected with an expression vector pcDNA3.1-MTLC by liposome and screened by G418. Growth of cells expressing MTLC was observed daily by manual counting. Apoptotic cells were determined by TdT-mediated dUTP nick-end labeling (TUNEL) assay.

RESULTS: The expression of MTLC mRNAs was down-regulated in 9 (60%) of 15 cases of GC tissues. The growth rates of the BGC823 cells expressing MTLC were indistinguishable from that of control cells. A marked acceleration of apoptosis was observed in MTLC-expressing cells.

CONCLUSION: MTLC was down-regulated in the majority of GC tissues and could promote apoptosis of GC cell lines, which suggests that MTLC may play an important role in the carcinogenesis of gastric carcinoma.

Identification of antigens by monoclonal antibody PD4 and its expression in Escherichia coli

AIM

To clone and express the antigen of monoclonal antibody (MAb) PD4 for further investigation of its function.

METHODS

MGC803 cDNA expression library was constructed and screened with PD4 as probes to clone the antigen. After failed in the library screening, immunoprecipitation and SDS-polyacrylamide gel electrophoresis were applied to purify the antigen for sequence analysis. The antigen coming from Mycoplasma hyorhinis (M. hyorhinis) was further confirmed with Western blot analysis by infecting M. hyorhinis -free HeLa cells and eliminating the M. hyorhinis from MGC803 cells. The full p37 gene was cloned by PCR and expressed successfully in Escherichia coli after site-directed mutations. Immunofluorescence assay was used to demonstrate if p37 protein could directly bind to gastric tumor cell AGS.

RESULTS

The cDNA library constructed with MGC803 cells was screened by MAb PD4 as probes. Unfortunately, the positive clones identified with MAb PD4 were also reacted with unrelated antibodies. Then, immunoprecipitation was performed and the purified antigen was identified to be a membrane protein of Mycoplasma hyorhinis (M. hyorhinis) by sequencing of N-terminal amino acid residues. The membrane protein was intensively verified with Western blot by eliminating M. hyorhinis from MGC803 cells and by infecting M. hyorhinis-free HeLa cells. The full p37 gene was cloned and expressed successfully in Escherichia coli after site-directed mutations. Immunofluorescence demonstrated that p37 protein could directly bind to gastric tumor cell AGS.

CONCLUSION

The antigen recognized by MAb PD4 is from M. hyorhinis, which suggests the actions involved in MAb PD4 is possibly mediated by p37 protein or M. hyorhinis. As p37 protein can bind directly to tumor cells, the pathogenic role of p37 involved in tumorigenesis justifies further investigation.

Establishment of apoptotic model induced by hydroxyapatite nanoparticles in human hepatoma cell line BEL-7402

AIM

To establish an apoptotic model induced by hydroxyapatite (HAP) nanoparticles in human hepatoma cell line in vitro in order to explore the mechanism of nanoparticles-induced apoptosis.

METHODS

The selected human hepatoma cell line BEL-7402 was treated with HAP nanoparticles at different concentrations and for various durations of time. Growth suppression was evaluated by MTT method. Apoptosis-related alterations in morphology and biochemistry were ascertained under cytochemical staining (Hoechst 33 258), transmission electron microscopy (TEM), and DNA agarose gel electrophoresis. Flow cytometry (FCM) was used to investigate the apoptotic rate.

RESULTS

HAP nanoparticles inhibited the growth of hepatoma cells in a dose and time-dependent manner. After BEL-7402 cells were treated with 50-200 mg/L HAP nanoparticles for 48 h, apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage were observed using fluorescent staining and TEM. DNA ladder could be demonstrated on DNA electrophoresis. By FCM analysis, the apoptotic rates at concentrations of 0 mg/L, 50 mg/L,75 mg/L, 100 mg/L, 150 mg/L, 200 mg/L were 2.2%, 20.3%, 25.3%, 29.8%, 45.1% and 53.1%, respectively. Cell apoptosis began approximately at 12h after administration of 50 mg/L and peaked at 48 h following treatment. The rates at 12, 24, 36, and 48 h were 2.7%, 3.5%, 6.3%, and 21.4%, respectively.

CONCLUSION

HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro. The successful establishment of this model will help further explore the molecular mechanism of hepatoma cells apoptosis.

Apoptosis-inducing effect of recombinant Caspase-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901

AIM: To investigate the apoptosis-inducing effect of Caspases-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901.

METHODS: PCR was employed to amplify the sequences of both small and large subunits of Caspases-3. Its products were separately cloned into the Sma I site of pBluescript KS⁺ to generate both plasmids pBS/SS and pBS/LS. The small subunit fragment was excised from plasmid pBS/SS with BamH I and then inserted into the BamH I site of plasmid pBS/LS preceding that of the large subunit to yield plasmid pBS/Rev-Caspase-3. Rev-Caspase-3 cDNA was excised with Kpn I + Xba I and then subcloned into plasmid pcDNA3.1 (+) to construct Rev-Caspase-3 eukaryotic expression vector pcDNA/Rev-Caspase-3, which was used to transiently transfect SGC7901 cell line. Cell count, MTT assay and electron microscopy were used to confirm the antiproliferation and apoptosis-inducing effect of Rev-Caspase-3 expression on gastric cancer cells.

RESULTS: Plasmid pBS/Rev-Caspase-3 and eukaryotic expression vector pcDNA/Rev-Caspase-3 were successfully constructed. SGC7901 cells were transiently transfected by either pcDNA/Rev-Caspase-3 or pcDNA3.1 (+) for 24, 48, 72, and 96 h respectively. Cell growth was measured by cell count and MTT assay. In cell count assay, the cell numbers were 1.8 × 10⁶, 1.55 × 10⁶, 2.0 × 10⁶, and 3.1 × 10⁶ in the experimental group and 2.5 × 10⁶, 3.1 × 10⁶, 4.0 × 10⁶, and 5.7 × 10⁶ in the control group at 24, 48, 72 and 96 h respectively. The growth of SGC7901 cells was suppressed by Rev-Caspase-3 in a time-dependent manner (P < 0.05). The results of MTT assay were similar to that of cell count (P < 0.05). The characteristics of apoptosis such as chromatin condensation, crescent formation and margination were seen and more obvious with time in the given-experimental period in the experimental group, but not easily observed in the control group.

CONCLUSION: The expression of Rev-Caspase-3 by the constructed eukaryotic vector can significantly induce apoptosis of gastric cancer cell line SGC7901, which may exhibit a potential way in gastric cancer gene therapy.

Effects of hydroxyapatite nanoparticles on proliferation and apoptosis of human hepatoma BEL-7402 cells

AIM: To study the effect of hydroxyapatite (HAP) nanoparticles on human hepatoma cell line BEL-7402 in vitro.

METHODS: The human hepatoma cell line BEL-7402 was cultured and treated with HAP nanoparticles at various concentrations. Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by cytochemical staining (Hoechst 33258), transmission electron microscopy (TEM), and flow cytometry (FCM).

RESULTS: HAP nanoparticles inhibited the growth of hepatoma cells in a dose-dependent manner, with IC₅₀ values of 29.30 mg/L. Treated with 50-200 mg/L HAP nanoparticles for 48 h, BEL-7402 cells apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage and the formation of apoptotic bodies were observed under cytochemical staining and transmission electron microscopy. FCM analysis showed hypodiploid peaks on histogram, the apoptotic rates at the concentrations of 50, 75, 100, 150 and 200 mg/L of HAP nanoparticles were 20.35 ± 2.23%, 25.35 ± 1.92%, 29.34 ± 4.61%, 44.92 ± 3.78% and 53.64 ± 3.49%, respectively, which were all significantly higher than that of control group 2.23 ± 0.14%. There was a significant correlation between HAP nanoparticle concentration and apoptotic rate (r = 0.994, P < 0.01).

CONCLUSION: HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro.

Peroxisome proliferator-activated receptor gamma ligands inhibit cell growth and induce apoptosis in human liver cancer BEL-7402 cells

AIM: To investigate the characteristics of PPAR gamma ligands induced apoptosis in liver cancer cells.

METHODS: The effects of ligands for each of the PPAR gamma ligands on DNA synthesis and cell viability were examined in BEL-7402 liver cancer cells. Apoptosis was characterized by Hochest33258 staining, DNA fragmentation, TUNEL and ELISA, and cell cycle kinetics by FACS. Modulation of apoptosis related caspases expression by PPAR gamma ligands was examined by Western blot.

RESULTS: PPARgamma ligands, 15-deoxy-^{12, 14}-prostaglandin J2 (15d-PGJ2) and troglitazone (TGZ), suppressed DNA synthesis of BEL-7402 cells. Both 15d-PGJ2 and TGZ induced BEL-7402 cell death in a dose dependent manner, which was associated with an increase in fragmented DNA and TUNEL-positive cells. At concentrations of 10 and 30 µM, 15d-PGJ₂ or troglitazone increased the proportion of cells with G₀/G₁ phase DNA content and decreased those with S phase DNA content. There was no significant change in the proportion of cells with G₂/M DNA content. The activities of Caspases-3, -6, -7 and -9 were increased by 15d-PGJ2 and TGZ treatment, while the activity of Caspase 8 had not significantly changed.

CONCLUSION: The present results suggest the potential usefulness of PPAR gamma ligands for chemoprevention and treatment of liver cancers.

Effects of cyclooxygenase-2 antisense vector on proliferation of human cholan-giocarcinoma cells

AIM

To transfect antisense vector of human COX-2 gene into COX-2 highly expressing cholangiocarcinoma cell line QBC939 and to explore its biological activities and role in carcinogenesis.

METHODS

QBC939 cells were transfected with antisense vector of human COX-2 gene using LipoVecTM transfecting technique. Transfected cells were selected with G418; COX-2 mRNA was examined by using reverse transcription polymerase chain reaction (RT-PCR) and COX-2 protein expression was detected by immunocytochemistry using isozyme selective antibodies. The proliferative status of transfected cells was measured by using methabenzthiazuron (MTT) assay; Cell cycle and apoptosis was analyzed by using flow cytometry (FCM).

RESULTS

RT-PCR showed a lower COX-2 mRNA level in transfected cells and immunocytochemistry showed weaker COX-2 protein expression in transfected cells. The proliferative index of the transfected cells decreased significantly(P<0.01), the percentage of S phase decreased remarkably in transfected cells(9.27±1.91%) compared with that in QBC939 cells without transfection (16.35±2.87%)(P<0.05), and the percentage of G0/G1 phase increased remarkably in transfected cells (75.16±4.13%) compared with that in QBC939 cells without transfection (57.31±10.16%)(P<0.05). Transfection with antisense vector of human COX-2 gene had no significant influence on the apoptosis in QBC939 cells (P>0.05).

CONCLUSION

Transfection with antisense vector of human COX-2 gene is able to inhibit the proliferation of human cholangiocarcinoma QBC939 cells.

Celecoxib inhibits proliferation and induces apoptosis via prostaglandin E2 pathway in human cholangiocarcinoma cell lines

AIM: To evaluate the roles and mechanisms of celecoxib in inducing proliferation inhibition and apoptosis of human cholangiocarcinoma cell lines.

METHODS: Cyclooxygenase-2-overexpressing human cholangiocarcinoma cell line QBC939 and cyclooxygenase-2-deficient human cholangiocarcinoma cell line SK-CHA-1 were used in the present study. The anti-proliferative effect was measured by methabenzthiazuron (MTT) assay; apoptosis was determined by transferase-mediated dUTP nick end labeling (TUNEL) detection and transmission electron microscopy (TEM). Cell cycle was analyzed by flow cytometry (FCM). The PGE₂ levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).

RESULTS: Celecoxib suppressed the production of PGE₂ and inhibited the growth of QBC939 cells. Celecoxib at 10, 20, and 40 μmol/L inhibited PGE₂ production by 26%, 58%, and 74% in QBC939 cells. The PGE₂ level was much lower constitutively in SK-CHA-1 cells (18.6 ± 3.2) compared with that in QBC939 (121.9 ± 5.6) cells (P < 0.01) and celecoxib had no significant influence on PGE₂ level in the SK-CHA-1 cells. The PGE₂ concentration in SK-CHA-1 cells also reduced but not significantly after treatment with celecoxib. The PGE₂ concentration in SK-CHA-1 cells was (16.5 ± 2.9) ng/well, (14.8 ± 3.4) ng/well, (13.2 ± 2.0) ng/well and (12.6 ± 3.1) ng/well respectively, when pre-treated with 1 μmol/L, 10 μmol/L, 20 μmol/L and 40 μmol/L of celecoxib for 48 h (P > 0.05, vs control). The anti-proliferation effect of celecoxib (20 μmol/L) on QBC939 cells was time-dependent, it was noticeable on day 2 (OD490 = 0.23 ± 0.04) and became obvious on day 3 (OD₄₉₀ = 0.31 ± 0.07) to day 4 (OD490 = 0.25 ± 0.06), and the OD₄₉₀ in the control group (day 1) was 0.12 ± 0.03 (P < 0.01, vs control). The anti-proliferation effect of celecoxib could be abolished by the addition of 200 pg/mL PGE₂. The proliferation of SK-CHA-1 cells was inhibited slightly by celecoxib, the cell density OD490 in the presence of celecoxib and in control group was 0.31 ± 0.04 and 0.42 ± 0.03 respectively on day 2 (P > 0.05), 0.58 ± 0.07 and 0.67 ± 0.09 respectively on day 3 (P > 0.05), and 0.71 ± 0.08 and 0.78 ± 0.06 respectively on day 4 (P > 0.05). Celecoxib induced proliferation inhibition and apoptosis by G₁-S cell cycle arrest: the percentage of QBC939 cells in G₀-G₁phase after treatment with 40 μmol/L (74.6 ± 66.21) and 20 μmol/L (68.63 ± 4.36) celecoxib increased significantly compared with control cells (54.41 ± 5.12, P < 0.01). The percentage of SK-CHA-1 cells in G₀-G₁ phase after treatment with various concentrations of celecoxib didn't change significantly compared with control cells. The TUNEL index was much higher in QBC939 cells treated with 20 μmol/L celecoxib for 2 d (0.063 ± 0.018) and for 4 d (0.102 ± 0.037) compared with control cells (0.017 ± 0.004, P < 0.01).

CONCLUSION: The current in vitro study indicates that inhibition of proliferation and induction of apoptosis in human cholangiocarcinoma cells by cyclooxygenase-2 specific inhibitor celecoxib may involve in COX-dependent mechanisms and PGE₂pathway. Celecoxib as a chemopreventive and chemotherapeutic agent might be effective primarily on COX-2-expressing cholangiocarcinoma.

PPARγ pathway activation results in apoptosis and COX-2 inhibition in HepG2 cells

AIM: To investigate whether troglitazone (TGZ), the peroxisome proliferator-activated receptor (PPAR) gamma ligand, can induce apoptosis and inhibit cell proliferation in human liver cancer cell line HepG2 and to explore the molecular mechanisms.

METHODS: [3-(4, 5)-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT), [³H] Thymidine incorporation, Hochest33258 staining, DNA ladder, enzyme-linked immunosorbent assay (ELISA), RT-PCR, Northern and Western blotting analyses were employed to investigate the effect of TGZ on HepG2 cells and related molecular mechanisms.

RESULTS: TGZ was found to inhibit the growth of HepG2 cells and to induce apoptosis. During the process, the expression of COX-2 mRNA and protein and Bcl-2 protein was down-regulated, while that of Bax and Bak proteins was up-regulated, and the activity of caspase-3 was elevated. Furthermore, the level of PGE₂ was decreased transiently after 12 h of treatment with 30 μM troglitazone.

CONCLUSION: TGZ inhibits cell proliferation and induces apoptosis in HepG2 cells, which may be associated with the activation of caspase-3-like proteases, down-regulation of the expression of COX-2 mRNA and protein, Bcl-2 protein, the elevation of PGE₂ levels, and up-regulation of the expressions of Bax and Bak proteins.

Effects of adenovirus-mediated human cox-2 antisense RNA on synthesis of DNA and proteins in esophgeal carcinoma cell line

AIM

To construct the recombinant adenovirus encoding human cox-2 antisense RNA, and to investigate its effect on synthesis of DNA and proteins in esophgeal carcinoma cell line EC9706.

METHODS

The shuttle plasmid encoding antisense cox-2 was constructed by cloning cox-2 cDNA fragment in the reverse direction into the pHCMVSP1A. Then the plasmid pJM17 and the shuttle plasmid were cotransferred into 293 cells with lipofectamine for homologouserecombinantion to acquire recombinant adenovirus confirmed by PCR. The expressions of cox-2 in esophgeal carcinoma cell line EC9706 cells were evaluated, and its effects on cell proliferation were determined by cell growth rate, ³H-TdR and ³H-Leucine incorporation.

RESULTS

The recombinant adenovirus encoding antisense cox-2 fragment ad-AShcox-2 was obtained with the titer of 0.86±10¹² PFU/ml. Ad-AShcox-2 can reduce the expression of cox-2, and inhibit cell growth rate and cause cellular death. Meanwhile, The efficiency of ³H-TdR and ³H-Leucine incorporation was significant lower than that in the control group at 48, 72, 96 hours (q_{48 h} = 16.36 vs 16.36, q_{72 h} = 39.07 vs 19.90 , q_{96 h}= 54.80 vs 30.33; P<0.001).

CONCLUSION

Reducing the expression of cox-2 may inhibit the proliferation of esophageal cancer cells through inhibiting the synthesis of DNA and protein.

Synergistic effects of nimesulide and 5-fluorouracil on tumor growth and apoptosis in the implanted hepatoma in mice

AIM: To compare the effect of nimesulide or/and 5-fluorouracil (5-FU) on tumor growth inhibition and apoptosis in mice with the implanted hepatoma and to observe their possible interactions.

METHODS: The inhibitory effects on tumor growth was evaluated by inhibition rate. Apoptosis was assessed by the ultrastructural, flow cytometry features and the DNA ladder demonstrated by agarose gel electrophoresis. PGE₂ level was determined by radioimmunoassay. Expression levels of c-jun, c-fos and p53 were evaluated by western blotting.

RESULTS: Nimesulide or 5-FU alone inhibited the growth of hepatoma, while a synergistic effect was observed for a combined use of both. More pronounced morphologic changes for tumor cell apoptosis and the DNA ladder were found for the latter treatment. Expression levels of c-jun and p53 were found to be elevated for the tumors from mice treated with nimesulide and 5-FU comparing to those with either of them, but a reduced PGE₂ level was observed only for the treatment with nimesulide. No change was detected on c-fos expression.

CONCLUSION: Nimesulide and 5-FU appear to have synergistic effects for the growth inhibition and apoptosis induction. Both were found to be overexpressed in p53 and c-jun proteins, rather than that of c-fos, associations with the resulted apoptosis.

Bile from a patient with anomalous pancreaticobiliary ductal union promotes the proliferation of human cholangiocarcinoma cells via COX-2 pathway

AIM: To explore the effects of COX-2 gene in the proliferative activity induced by bile from anomalous pancreaticobiliary ductal union (APBDU) on human cholangiocarcinoma cell line.

METHODS: Bile sample from APBDU and normal bile sample were used for this study. The proliferative effect of bile was measured by methabenzthiazuron (MTT) assay; COX-2 mRNA was examined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Cell cycle was analyzed by flow cytometry (FCM), and the PGE₂ levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).

RESULTS: Bile from APBDU can significantly promote the proliferation of human cholangiocarcinoma QBC939 cells compared with normal bile (P = 0.005) and up-regulated remarkably their COX-2 mRNA expression (P = 0.004). The proliferative activity of APBDU bile can be abolished by addition of cyclooxygenase-2 specific inhibitor celecoxib.

CONCLUSION: Bile from APBDU can promote the proliferation of human cholangiocarcinoma QBC939 cells via COX-2 pathway.

Nimesulide inhibits proliferation via induction of apoptosis and cell cycle arrest in human gastric adenocarcinoma cell line

AIM

To evaluate the potential role of Nimesulide, a selective COX-2 inhibitor, in proliferation and apoptosis of gastric adenocarcinoma cells SGC7901.

METHODS

Cell counts and MTT assay were used to quantify the influence of Nimesulide in the proliferation of SGC7901 cells. Transmission electron microscopy and flow cytometry were used to observe the induction of Nimesulide the apoptosis of SGC7901 cells and influence in the distribution of cell cycle. The expression of P27(kip1) protein was observed by immunocytochemical staining.

RESULTS

SGC-7901 Cells treated with Nimesulide at various concentrations exhibited a profound dose- and time-dependent reduction in the proliferation rate over the 72 h test period. The highest survival rate of the cells was 78.7 %, but the lowest being 22.7 %. Nimesulide induced apoptosis of the cells in a dose-dependent and non-linear manner and increased the proportion of cells in the G(0)/G(1) phase and decreased the proportion in the S and G(2)/M phase of the cell cycle. Meanwhile, Nimesulide could up-regulate the expression of P27(kip1) protein.

CONCLUSION

The induction of apoptosis and cell cycle arrest are both anti-proliferative responses that likely contribute to the antineoplastic action of nimesulide on SGC-7901 cells. The up-regulation of P27(kip1) gene may contribute to the accumulation of these cells in the G(0)/G(1) phase following treatment with Nimesulide. Selective COX-2 inhibitor may be a new channel of the chemoprevention and chemotherapy for gastric carcinoma.

Correlation of COX-2 expression and clinicopathological features of colorectal cancer

AIM: To investigate the expression of COX-2 on different stages of colorectal cancer and the correlation between the expression of COX-2 and its clinicopathological features.

METHODS: The expression of COX-2 was determined by immunohistochemical staining in seventy-six surgical specimens of colorectal cancer (late stage 44 and early stage 32), 33 adenomas and 18 normal colonic mucosal tissues were biopsied endocscopically. The correlation of COX-2 with the survival rate was evaluated with Kaplan-Meier survival curves and Cox proportional hazards regression.

RESULTS: The degree of expression of COX-2 was categorized into 4 grades ranged from "-" to "+++", the expression grades in series in normal colonic mucosal tissues was 83.3%, 16.7%, 0%, 0%, respectively; that in adenomas was 12.1%, 42.4%, 36.4%, 9.1%, respectively. The difference of the expression of COX-2 between late stage and early stage of colorectal cancer, and that between the late stage of cancer and adenoma were statistically significant (P < 0.01); however, no significant difference in the expression of COX-2 between early stage of cancer and adenoma was observed. A significant difference in the survival curves between low COX-2 expression group and high COX-2 expression group was showed by Kaplan-Meier survival analysis (P < 0.05). Cox proportional hazards regression indicated that the correlation of the expression of COX-2 with the poor long-term prognosis was existed with a hazard ratio of 2.665 unadjusted for other variables (P < 0.05); the expression of COX-2 was an independent risk factor for poor prognosis.

CONCLUSION: The expression of COX-2 is gradually up-regulated in the evolution of normal epithelium to adenoma or from early stage to advanced stage of colorectal cancer. The expression of COX-2 is an independent risk factor of poor prognosis for postoperative patients with advanced colorectal cancer.

The study of chemiluminescence in gastric and colonic carcinoma cell lines treated by anti-tumor drugs

AIM: To study the influence of chemotherapy on proliferation activation of tumor cell by observing the change of chemiluminescence (CL) and cell cycle in various tumor cell lines after mitomycin C treated.

METHODS: BGC823 and LoVo cell lines were all cultured in RPMI-1640, and then were adjusted to a concentration of 1 × 10⁵ cells/mL in fresh media and incubated for 24 h. Mitomycin C (100 ng·L^-1) was added to each bottle. All indeses were examined after 24 h. No Mitomycin C was added in control group. Each group contained 8 samples. Flow cytometric analysis and luminol-dependent CL were used to investigate the effect of mitomycin C on two gastrointestinal carcinoma cell lines.

RESULTS: BGC823 and LoVo cell lines incubated with MMC for 24 h. We discovered that the emergence of peak of CL stimulated by PHA was postponed significantly (BGC823: 12.63 ± 3.21 vs 4.50 ± 1.04, LoVo: 13.25 ± 2.96 vs 5.12 ± 1.36, P < 0.01) and the peak intension of CL was reduced significantly (BGC823: 120.25 ± 16.61 vs 248.38 ± 29.17, LoVo: 98.13 ± 10.49 vs 267.50 ± 18.56, P < 0.01). The PI of cell lines was decreased significantly (BGC823: 51.87 ± 4.82 vs 25.44 ± 2.26, LoVo: 47.11 ± 1.04 vs 24.23 ± 0.37, P < 0.01) and the apoptotic fractions changed by contraries (BGC823: 26.25 ± 5.29 vs 9.83 ± 2.51, LoVo: 33.50 ± 3.68 vs 9.63 ± 1.44, P < 0.01).

CONCLUSION: CL can be used to measure activation of tumor cells. We discovered that the ground CL intensions of two cell lines were not high but increased rapidly after stimulation of PHA. The CL peak ranged from 4-5 min, and then decreased gradually. The results were not reported before. CL of tumor cell has close correlativity with the dynamics of cell cycle and can reflect the feature of oxidation metabolism and proliferation activation of tumor cell. So it can be used to observe the influence of chemotherapy drug on metabolism and proliferation activation of tumor cell and screen out chemotherapy drugs to which tumor cells are sensitive.

Expression of cyclooxygenase-2 in pancreatic cancer and its correlation with p53

AIM: To investigate the expressions of COX-2 and p53 in human pancreatic cancer and their correlation with biological behaviors of pancreatic cancer.

METHODS: The expressions of COX-2 and p53 in 51 specimens of human pancreatic ductal adenocarcinoma and 11 specimens of normal tissues adjacent human pancreatic ductal adenocarcinoma were detected with immunohistochemistry by Envision.

RESULTS: The detectable rate of COX-2 and p53 in pancreatic ductal adenocarcinoma were 74.5% and 60.8%, respectively; but none in adjacent normal tissues. The expression of COX-2 was significantly associated with the clinical stages and metastasis status of lymph nodes (P = 0.022, 0.036), but not with histological grade (P = 0.152). The expression of p53 was significantly correlated with the lymph node metastasis status (P = 0.035), but not with their histological grades and clinical stages (P = 0.131, 0.078). There was a significant correlation between the expression of COX-2 and p53 (r = 0.452, P = 0.001). Conditions such as age, sex, tumor size and location had no relation with expression of COX-2 or p53.

CONCLUSION: The cooperation of COX-2 and p53 may play a pivotal role in the carcinogenesis and the progression in pancreatic cancer. They may provide new targets for the therapy of pancreatic cancer.

Proliferative activity of bile from congenital choledochal cyst patients

AIM: To explore the potential carcinogenicity of bile from congenital choledochal cyst (CCC) patients and the mechanism of the carcinogenesis in congenital choledochal cyst patients.

METHODS: 20 bile samples from congenital choledochal cyst patients and 10 normal control bile samples were used for this study. The proliferative effect of bile was measured by using Methabenzthiazuron (MTT) assay; Cell cycle and apoptosis were analyzed by using flow cytometry (FCM), and the PGE₂ levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).

RESULTS: CCC bile could significantly promote the proliferation of human cholangiocarcinoma QBC939 cells compared with normal bile (P = 0.001) and negative control group (P = 0.002), and the proliferative effect of CCC bile could be abolished by addition of cyclooxygenase-2 specific inhibitor celecoxib (20 µM). The QBC939 cells proliferative index was increased significantly after treated with 1% bile from CCC patient (P = 0.008) for 24 h, the percentage of S phase (29.48 ± 3.27)% was increased remarkably (P < 0.001) compared with normal bile (11.72 ± 2.70)%, and the percentage of G0/G1 phase (54.19 ± 9.46)% was decreased remarkably (P = 0.042) compared with normal bile (69.16 ± 10.88)%, however, bile from CCC patient had no significant influence on apoptosis of QBC939 cells (P = 0.719).

CONCLUSION: Bile from congenital choledochal cyst patients can promote the proliferation of human cholangiocarcinoma QBC939 cells via COX-2 and PGE₂ pathway.

Effect of Helicobacter pylori infection on bax protein expression in patients with gastric precancerous lesions

AIM: To evaluate the effect of Helicobacter pylori (H. pylori) infection on bax protein expression, and explore the role of H. pylori in the development of gastric carcinoma.

METHODS: H. pylori was examined by rapid urease test and Warthin-Starry method, and bax protein was examined by immunohistochemical staining in 72 patients with pre-malignant lesions.

RESULTS: Bax protein was expressed with different degree in intestinal metaplasia and gastric dysplasia, its positive rate being 63.9%. The positive rate of Bax protein expression in H. pylori-positive gastric precancerous lesions (72.3%) was significantly higher than that in H. pylori-negative gastric precancerous lesions (48.0%, x² = 4.191, P < 0.05). H. pylori infection was correlated well with the expression of Bax protein in gastric precancerous lesions(r = 0.978, P < 0.01). After eradication of H. pylori, the positive rate of bax protein expression was significantly decreased in H. pylori-positive gastric precancerous lesions(x² = 5.506, P < 0.05). In the persistent H. pylori infected patients, the positive rate of Bax protein expression was not changed.

CONCLUSION: H. pylori is involved in the expression of Bax gene. H. pylori infection increases the expression of Bax protein, this may be one of the mechanisms of H. pylori infection in the induction of gastric epithelial cell apoptosis. H. pylori might act as a tumor promoter in the genesis of gastric carcinoma. Eradication of H. pylori could inhibit the formation and development of gastric carcinoma.

Nimsulide suppresses the telomerase activity of SGC7901 gastric cancer cell line

AIM: To investigate whether nimsulide, a COX-2-specific inhibitor, could inhibit the proliferation viability and the telomerase activity of SGC7901 gastric cancer cell line.

METHODS: After SGC7901 was treated with different concentrations of nimsulide(0, 50, 100, 200 and 400 μmol/L, respectively), the cellular proliferation was evaluated by MTT assay and the telomerase activity was detected by PCR-ELISA assay. And the cell morphology and growth manner were observed under phase contrast microscope.

RESULTS: Nimsulide could inhibit the growth of SGC7901 gastric cancer cell line in the time and dose-dependent manner; and the telomerase activity of SGC7901 was significantly lower in the 50, 100, 200 and 400 μmol/L groups than that in the control group, their absorbance values were 2.12±0.11, 1.54±0.08, 1.13±0.09, 0.79±0.12 vs 2.76±0.06(P < 0.01), respectively.

CONCLUSION: COX-2-specific inhibitor could inhibit the telomerase activity of gastric cancer cell line, which provides a new pathway of COX-2-specific inhibitor in inhibiting the growth of gastric cancer.

Effect of apoptosis on gastric adenocarcinoma cell line SGC-7901 induced by cis-9, trans-11-conjugated linoleic acid

AIM: To determine the effect of apoptosis on gastric cancer cells (SGC-7901) induced by cis-9, trans-11-conjugated linoleic acid (c9, t11-CLA) and its possible mechanism in the inhibition of cancer cells growth.

METHODS: Using cell culture, flow cytometery and immunocytochemical techniques, we examined the cell growth, frequency of apoptosis and distribution of cell cycle, expression of ki67, bcl-2, Fas, and c-myc of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25, 50, 100 and 200 μmol·L^-1) of c9, t11-CLA for 24 h and 48 h, with a negative control (0.1% ethanol).

RESULTS: The growth of SGC-7901 cells was inhibited by c9,t11-CLA. Eight days after treatment with various concentrations of c9,t11-CLA, as mentioned above, the inhibition rates were 5.9%, 20.2%, 75.6% and 82.4%, respectively. The frequency of apoptosis on SGC-7901 cells induced by different concentrations of c9, t11-CLA (except for 25 μmol·L^-1, 24 h) was significantly greater than that in the negative control (P < 0.01). To further investigate the influence of the cell cycle progression, we found that apoptosis induced by c9, t11-CLA may be involved in blocking the cell cycle of SGC-7901 cells. Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations for various time periods significantly decreased the expressions of ki67 (the expression rates were 18.70%-3.20%, at 24 h and 8.10%-0.20% at 48 h, respectively), bcl-2 (4.30%-0.15% at 24 h and 8.05%-0% at 48 h),and c-myc (4.85%-2.20% at 24 h and 4.75%-0.30% at 48 h) as compared with those in the controls (the expressions of ki67, bcl-2, and c-myc were 15.1% at 24 h and 13.5% at 48 h, 6.80% at 24 h and 8.00% at 48 h, 5.50% at 24 h and 5.30% at 48 h, respectively) (P < 0.01), whereas the expressions of Fas were increased (0.60%-2.75%, 24 h and 0.45%-5.95%, 48 h).

CONCLUSION: The growth and proliferation of SGC-7901 cells are inhibited by c9, t11-CLA via blocking the cell cycle, pathways of bcl-2-associated mitochondria with reduced expression of bcl-2 and Fas-associated death domain protein (FADD) with enhanced expression of Fas. But expression of c-myc on SGC-7901 cells is lower than that in negative control, which needs to be studied further.