Peptide Inhibitor Targeting the Extraterminal Domain in BRD4 Potently Suppresses Breast Cancer Both In Vitro and In Vivo

BRD4 is associated with a variety of human diseases, including breast cancer. The crucial roles of amino-terminal bromodomains (BDs) of BRD4 in binding with acetylated histones to regulate oncogene expression make them promising drug targets. However, adverse events impede the development of the BD inhibitors. BRD4 adopts an extraterminal (ET) domain, which recruits proteins to drive oncogene expression. We discovered a peptide inhibitor PiET targeting the ET domain to disrupt BRD4/JMJD6 interaction, a protein complex critical in oncogene expression and breast cancer. The cell-permeable form of PiET, TAT-PiET, and PROTAC-modified TAT-PiET, TAT-PiET-PROTAC, potently inhibits the expression of BRD4/JMJD6 target genes and breast cancer cell growth. Combination therapy with TAT-PiET/TAT-PiET-PROTAC and JQ1, iJMJD6, or Fulvestrant exhibits synergistic effects. TAT-PiET or TAT-PiET-PROTAC treatment overcomes endocrine therapy resistance in ERα-positive breast cancer cells. Taken together, we demonstrated that targeting the ET domain is effective in suppressing breast cancer, providing a therapeutic avenue in the clinic.

[Transjugular intrahepatic portosystemic shunt for esophagogastric variceal bleeding in liver cirrhosis: intended population and timing]

Esophagogastric variceal bleeding is a life-threatening complication of cirrhotic portal hypertension. Transjugular intrahepatic portosystemic shunt (TIPS) is an effective method for the treatment and prevention of esophagogastric variceal bleeding; however, right timing of TIPS and selection of appropriate candidates for TIPS are of vital importance in improving patients' survival rate and reducing mortality rate. This article reviews the intended population and right timing of TIPS for the treatment and prevention of esophagogastric variceal bleeding in liver cirrhosis.

[Current status of treatment of refractory ascites in patients with liver cirrhosis]

Ascites is a common clinical manifestation of cirrhotic portal hypertension, and about 60%-80% of cirrhotic patients develop the symptom of ascites within 10 years. Once ascites occurs, the 5-year survival rate is reduced from 80% to 50%. With the progression of liver diseases, approximately 5%-10% of patients with ascites develop refractory ascites, and the median survival time is only 6-12 months. This article reviews the definition and diagnosis of refractory ascites, evaluation of prognostic factors, and treatment regimens, including large-volume paracentesis combined with protein supplementation, transjugular intrahepatic portosystemic shunt, and liver transplantation.

Successful ABO-incompatible living-related intestinal transplantation: a 2-year follow-up

ABO-incompatible intestinal transplantation has rarely been performed due to poor patient outcomes. Herein we present a case of successful ABO-incompatible intestinal transplantation with a 2-year follow-up. A 16-year-old female with a history of extensive bowel resection received an ABO-incompatible living donor bowel graft from her father (blood type AB graft into a type A recipient). Posttransplant immunosuppression consisted of an initial anti-CD20, plasmapheresis/intravenous immunoglobulin before transplantation, followed by an anti-thymocyte globulin (ATG) induction and splenectomy, and maintenance with tacrolimus and prednisone. Her postoperative course was remarkable for a single episode of rejection on day 14 which responded promptly to treatment with methyprednisolone and ATG. Three months after transplantation, the patient developed an abdominal abscess requiring open surgical drainage. No viral infections were encountered. Posttransplant anti-B antibody titers and anti-B7 donor-specific antibody levels remained low. At a 2-year follow-up, the patient showed a progressive weight gain of 5.0 kg. This case illustrates that ABO-incompatible living-related bowel transplantation is immunologically feasible and is associated with good outcomes for the recipient. The management of blood type antibodies and the use of adequate immunosuppression in the early period of the procedure may be the keys to the success of future cases.

Inhibitory effects of indirubin derivative PHII-7 on invasion and migration in metastatic cancer

PHII-7, a derivative of indirubin, showed significant anti-cancer activities in vivo and in vitro. We asked whether treating human metastatic cancers and multidrug resistant cancer with PHII-7 would inhibit their invasion and migration. Cell growth was tested by MTT assay and colony formation assay. Apoptosis was examined by flow cytometry. Transwell-based assay and wound healing assay were used to examine cell invasion and migration. Real-time PCR assay and western blot assay were performed to test gene expression on mRNA and protein level, respectively. Firstly, we confirmed that MCF-7/ADR cells showed more invasive and migratory properties compared with MCF-7 cells which were associated with several EMT markers, such as E-cadherin, Slug and vimentin. Secondly, we found that slightly toxic doses of PHII-7 decreased the number of cells that invaded a model epithelial basement membrane and that migrated by switching the molecular signature of the cells from mesenchymal to epithelial. And PHII-7 significantly regulated expression of several epithelial-mesenchymal transition (EMT)-related genes, including E-cadherin, Slug, β-catenin and vimentin. Thirdly, compared with control, PHII-7 inhibited cell proliferation in a time- and dose-dependent manner. Higher doses of PHII-7 also induced apoptosis through activating PARP, caspase-9 and caspase-3. PHII-7 significantly inhibited invasion and migration in both metastatic cancers and multidrug resistant cancer. Our results may provide several data for future application of PHII-7 on drug design and patients treatment.

KEYWORDS

PHII-7, invasion, migration, multidrug resistance, epithelial-mesenchymal transition.

Sorafenib combined with transarterial chemoembolization for the treatment of advanced hepatocellular carcinoma: a large-scale multicenter study of 222 patients

BACKGROUND

Data on the efficacy and safety of sorafenib in combination with transarterial chemoembolization (TACE) in patients with advanced hepatocellular carcinoma (HCC) are lacking.

PATIENTS AND METHODS

In this multicenter retrospective study, 222 consecutive HCC patients receiving combination therapy were enrolled between June 2008 and July 2011.

RESULTS

Chronic hepatitis B was the predominant cause of HCC (86%). Eighty percent patients were at Barcelona Clinic Liver Cancer (BCLC) stage C, and 86% patients were in Child-Pugh (CP) A class. The overall median survival was 12 months (95% CI 10.1-13.9). The overall incidence of adverse events (AEs) was 87%. In 177 BCLC-C patients, performance status, the number of HCC nodules, Child-Pugh score and macrovascular invasion were significantly associated with overall survival (OS) and were included in the final risk scores (R), where R = 5 × (vascular invasion: 0 if no, 1 yes) + 6 × (CP: 0 if A, 1 if B) + 7 × (no. of lesions: 0 if 1-2, 1 ≥3) + 8 × ( Eastern Cooperative Oncology Group, ECOG: 0 if 0, 1 ≥1).

CONCLUSIONS

Sorafenib in combination with TACE should be considered a safe and effective therapy for advanced HCC. Further validation of the new subgroup of BCLC-C stage is warranted in an independent patient cohort.

Screening and identification of peritoneal metastasis-related genes of gastric adenocarcinoma using a cDNA microarray

With the aim of identifying peritoneal metastasis-related genes in gastric cancer, we performed a broad analysis of differential gene expression between the parental cell line GC9811 and its highly metastatic peritoneal counterpart, cell line GC9811-P. Two fluorescent cDNA probes, labeled with Cy3 and Cy5 dyes, were prepared from GC9811 and GC9811-P mRNA samples by the reverse transcription method. The two color probes were then mixed and hybridized to a cDNA chip constructed with double-dots from 11,901 human genes; this was scanned at two wavelengths. The experiment was repeated twice. In GC9811-P cells, 218 genes were upregulated and 30 genes were downregulated compared with the parental cell lines. Some selected genes were confirmed by RT-PCR and Western blot; we found that S100A4 and CTNNB1 were upregulated and PTEN was downregulated in GC9811-P cells. Identification of these differentially expressed genes could contribute to disclose the molecular mechanisms involved and provide new targets for therapeutic intervention to avoid peritoneal dissemination of gastric adenocarcinoma.

Transgenic cyclooxygenase-2 expression and high salt enhanced susceptibility to chemical-induced gastric cancer development in mice

Cyclooxoygenase (COX)-2 overexpression is involved in gastric carcinogenesis. While high-salt intake is a known risk factor for gastric cancer development, we determined the effects of high salt on gastric chemical carcinogenesis in COX-2 transgenic (TG) mice. COX-2 TG mice were developed in C57/BL6 strain using the full-length human cox-2 complementary DNA construct. Six-week-old COX-2 TG and wild-type (WT) littermates were randomly allocated to receive alternate week of N-methyl-N-nitrosourea (MNU, 240 p.p.m.) in drinking water or control for 10 weeks. Two groups of mice were further treated with 10% NaCl during the initial 10 weeks. All mice were killed at the end of week 50. Both forced COX-2 overexpression and high-salt intake significantly increased the frequency of gastric cancer development in mice as compared with WT littermates treated with MNU alone. However, no additive effect was observed on the combination of high salt and COX-2 expression. We further showed that MNU and high-salt treatment increased chronic inflammatory infiltrates and induced prostaglandin E(2) (PGE(2)) production in the non-cancerous stomach. Whereas high-salt treatment markedly increased the expression of inflammatory cytokines (tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-1 beta and IL-6) in the gastric mucosa, COX-2 overexpression significantly altered the cell kinetics in the MNU-induced gastric cancer model. In conclusion, both high salt and COX-2 overexpression promote chemical-induced gastric carcinogenesis, possibly related to chronic inflammation, induction of PGE(2), disruption of cell kinetics and induction of inflammatory cytokines.

Overexpression of PrPC and its antiapoptosis function in gastric cancer

Cellular prion protein (PrP(C)), a glycosylphosphatidylinositol-anchored membrane protein, was found in our lab to be widely expressed in gastric cancer cell lines. In order to evaluate its biological significance in human gastric cancer, we investigated its expression in a large series of gastric tissue samples (n = 124) by immuno histochemical staining with the monoclonal antibody 3F4. Compared with normal tissues, gastric adenocarcinoma showed increased PrP(C) expression, correlated with the histopathological differentiation (according to the WHO and Lauren classifications) and tumor progression (as documented by pTNM staging). To better understand the underlying mechanism, we introduced the PrP(C) and two pairs of RNAi into the poorly differentiated gastric cancer cell line AGS and found that PrP(C) suppressed ROS and slowed down apoptosis in transfected cells. Further study proved that the apoptosis-related protein Bcl-2 was upregulated whereas p53 and Bax were downregulated in the PrP(C)-transfected cells. A reverse effect was observed in PrP(C) siRNA-transfected cells. These results strongly suggested that PrP(C) might play a role as an effective antiapoptotic protein through Bcl-2-dependent apoptotic pathways in gastric cancer cells. Further study into the mechanism of these relationships might enrich the knowledge of PrP, better our understanding of the nature of gastric carcinoma, and further develop possible strategies to block or reverse the development of gastric carcinoma.

Identification of the heterogeneous nuclear ribonucleoprotein A2/B1 as the antigen for the gastrointestinal cancer specific monoclonal antibody MG7

MG7 is an early gastrointestinal cancer specific monoclonal antibody. It can detect gastric cancer with high sensitivity and specificity. However, the target antigen for MG7 has not been identified. Western blot analysis revealed that the MG7 antibody reproducibly recognized two approximately 35 kDa proteins in the total cell lysates of human gastric carcinoma cell lines KATO III and MKN-45. Using a proteomic approach, we identified these MG7 immunoreactive proteins as the human heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1). Western blot analysis of nuclear and cytosolic fraction of KATO III cells using either MG7 or hnRNP A2/B1 antibodies confirmed that the target antigen is located exclusively in the nucleus. With the use of archival samples, we also found that the level of hnRNP A2/B1 protein was increased in gastric cancer tissues (4 out of 5 patients), when compared to their corresponding matching normal stomach tissue.

Effects of somatostatin, octreotide and pitressin plus nitroglycerine on systemic and portal haemodynamics in the control of acute variceal bleeding

To examine the haemodynamic effects of somatostatin (SS) and octreotide (OC) versus pitressin plus nitroglycerine (PN) in the control of variceal bleeding, 224 patients with acute oesophageal and gastric variceal haemorrhage were randomly divided into three groups and treated with SS, OC and PN; they also had their Doppler ultrasound parameters measured before, during and after treatment. The success rates of bleeding control in the SS (80.9%, 86.8% and 89.7%, p<0.001) and OC (75.3%, 80.8% and 84.9%, p<0.01) groups were significantly higher than in the PN group (51.8%, 59.0% and 65.1%) at 24, 48 and 72 hours respectively, and the average duration of SS (12.7 + 6.8 h) and OC (13.8 + 8.0 h) was significantly lower than that of PN (24.6 + 15.4 h, p<0.001). Side-effects of SS (7.4%) and OC (8.2%) were less than those of PN (41.0%, p<0.001 and p<0.01). The diameter of portal vein (PVD), velocity of portal vein (PVV), volume of portal blood flow (PVF) and hepatic artery pulsatility index (HA-PI) in all three groups decreased significantly during initial treatment, but recovered when treatment was stopped. Heart rate and cardiac output decreased significantly in patients treated with SS and OC; mean arterial pressure was unchanged. However, heart rate and mean arterial pressure increased, and cardiac output decreased, with PN. Somatostatin and octreotide were more effective than pitressin plus nitroglycerine in patients with acute variceal haemorrhage, with fewer side-effects, and may decrease PVF and portal vein pressure through reduction of cardiac output and dilatation of the visceral blood vessels.

The value of MG7 antigen in predicting cancerous change in dysplastic gastric mucosa

The aim of this study was to ascertain whether MG7Ag is a useful predictor of evolution of gastric dysplasia to carcinoma. A total of 1090 patients with confirmed dysplasia were stained immunohistochemically with MG7 monoclonal antibody by the ABC method. A prospective follow-up study was undertaken on 19 patients with MG7Ag positive staining and 16 with MG7 negative staining over a period of 10-78 months. The expression of MG7Ag was also compared in another two groups by conducting retrospective studies. One group showed an evolution into gastric cancer over 2-4 years, the other did not. Quantitative analysis of MG7Ag expression was carried out on the last two groups. The receiver operating characteristic curve and Youden index were used to assess the best critical value for MG7Ag. MG7Ag was found positive in 456/1090 cases (41.8%) with dysplasia. Prospective follow-up of 35 patients showed that 6/19 patients with MG7Ag positive staining developed gastric cancer, but there were no carcinomatous changes in 16 patients with MG7 negative staining. The results of MG7Ag expression in 72 cases with retrospective follow-up showed there were 24 with positive immunostaining among 34 cancerous cases (70.6%), and only 7 in 38 non-cancerous cases (18.4%) (p<0.01). Image analysis showed that an average MG7Ag density index ++0.19 could be regarded as the critical value for high risk of gastric mucosa with dysplasia evolving to cancer. Positive MG7Ag expression in gastric mucosa of patients with dysplasia, especially in cases with a density index ++0.19, was an indicator of high risk of malignant change.

Polymorphism of flagellin A gene in Helicobacter pylori

AIM: To study the polymorphism of flagellin A genotype and its significance in Helicobacter pylori (H. pylori).

METHODS: As the template, genome DNA was purified from six clinical isolates of H. pylori from outpatients, and the corresponding flagellin A fragments were amplified by polymerase chain reaction. All these products were sequenced. These sequences were compared with each other, and analyzed by software of FASTA program.

RESULTS: Specific PCR products were amplified from all of these H. pylori isolates and no length divergence was found among them. Compared with each other, the highest ungapped identity is 99.10%, while the lowest is 94.65%. Using FASTA program, the alignments between query and library sequences derived from different H. pylori strains were higher than 90%.

CONCLUSION: The nucleotide sequence of flagellin A in H. pylori is highly conservative with incident divergence. This information may be useful for gene diagnosis and further study on flagellar antigen phenotype.

Relationship between genotype and phenotype of flagellin C in Salmonella

AIM: To discover the relationship between the genotype and antigen serotype of flagellin C among Salmonella strains.

METHODS: Fragment of Salmonella flagellin C in plasmid pLS408 was cloned, sequenced and compared with the corresponding sequence in other strains. Salmonella strains including two typhi strains, one paratyphoid strain, one enteritidis and one typhimurium strain were isolated from outpatients. Genome DNA was purified respectively from these clinical isolates, then the corresponding flagellin C fragment was amplified by polymerase chain reaction, and the amplification products were analyzed by agarose gel electrophoresis.

RESULTS: The cloned fragment includes 582 nucleotides encoding the variable region and partial conservative region of Salmonella flagellin C in plasmid pLS408. With comparison to the corresponding sequences reported previously, there is only a little difference from other strains with the same flagellar serotype in both nucleotide and amino acid level. Specific PCR products were amplified in Salmonella strains with flagellar serotype H-1-d including S. muenchen, typhi and typhimurium, but not in S. paratyphoid C or S. enteritidis strains.

CONCLUSION: In this experiment, the specificity of nucleotide sequence could be found in flagellin C central variable regions as it exists in flagellar serotypes in Salmonella. It may be helpful to developing a rapid, sensitive, accurate and PCR-based method to detect Salmonella strains with serotype H-1-d.

Association of H. pylori infection with gastric carcinoma: A meta analysis

AIM: To follow the principles of evidence based medicine to reach the integrated results of these studies.

METHODS: Twenty-one papers of case-control studies were selected, including 11 on gastric cancer, 7 on precancerous lesion of stomach and 3 on lymphoma of stomach. Meta analysis was used to sum up the odds ratios (OR) of these studies.

RESULTS: H. pylori vsgastric cancer (intestinal and diffuse type): the odds ratio from the fixed effect model is 3.0016 (95% CI: 2.4197-3.7234, P < 0.001). H. pylori vs precancerous lesion of stomach: a random effect model was used to calculate the summary odds ratio and its value is 2.5635 (95% CI: 1.8477-3.5566, P < 0.01). H. pylori vs lymphoma of stomach: though the quantity of literature is too small to make Meta analysis, the data of these 3 studies show that lymphoma of stomach is highly associated with H. pylori infections.

CONCLUSION: Since it had been revealed that H. pylori infection pre-exists in gastric carcinoma and precancerous lesions, the results of Meta analysis present a strong evidence to support the conclusion that H. pylori infection is a risk factor for gastric carcinoma.

T cell receptor Vbeta repertoire expression reflects gastric carcinoma progression

Analysis of TCR beta-chain complementarity-determining region size gives an indication of the T cell immune response. We examined CD4+ and CD8+ subgroups of T cells in the peripheral blood (PBL), benign gastric mucosa, and tumor (TIL) lymphocytes of 12 patients with primary gastric carcinomas of both intestinal and diffuse types. The average number of expanded clones in each compartment, expressed by the 24 families of the TCRVbeta repertoire, was analyzed according to tumor histological type, maximal invasive depth, and lymph node metastases. Fewer clones were expressed by the PBL in the cases with lymph node metastases than in those without (CD4+ P = 0.00017, CD8+ P = 0.016). Fewer CD8+ clones were expressed by the PBL in the cases with full thickness tumor infiltration than in those involving only the mucosa and submucosa (P = 0.05). The CD8+ TIL showed significantly fewer clones in the diffuse-type carcinoma than in the intestinal type (P = 0.046).

Non-steroidal anti-inflammatory drugs induce apoptosis in gastric cancer cells through up-regulation of bax and bak

Aspirin- and non-steroidal anti-inflammatory drug (NSAID)-induced apoptosis is one of the important mechanisms for their anti-tumour effect in gastric cancer. We aimed at determining the role of bcl-2 family proteins and caspases in the apoptotic process. Gastric cancer cell lines AGS (wild-type p53) and MKN-28 (mutant p53) were used. Cell proliferation was measured by MTT assay. Apoptosis was determined by acridine orange staining. Protein expressions were determined by western blotting. Aspirin and indomethacin inhibited cell proliferation and induced apoptosis in both cells. AGS cells were more sensitive compared with MKN-28 cells. The pro-apoptotic proteins bax and bak were overexpressed after treatment, while the protein level of bcl-2 remained unchanged. Apoptosis was accompanied by an increase in caspase-3 activity and cleavage of caspase-3 and poly(ADP-ribose) polymerase. Inhibition of caspase-3 rescued aspirin-induced apoptosis. Our results suggest that one of the major pathways which mediates the anti-tumour response of aspirin and indomethacin in gastric cancer cells is through up-regulation of bax and bak and activation of caspase-3. Bax and bak are important in the chemoprevention of gastric cancer.

Preparation of single chain variable fragment of MG7 mAb by phage display technology

AIM: To develop the single chain variable fragment of MG₇ murine anti-human gastric cancer monoclonal antibody using the phage display technology for obtaining a tumor-targeting mediator.

METHODS: mRNA was isolated from MG₇ producing murine hybridoma cell line and converted into cDNA. The variable fragments of heavy and light chain were amplified separately and assembled into ScFv with a specially constructed DNA linker by PCR. The ScFvs DNA was ligated into the phagmid vector pCANTAB5E and the ligated sample was transformed into competent E. Coli TG1. The transformed cells were infected with M13K07 helper phage to form MG₇ recombinant phage antibody library. The volume and recombinant rate of the library were evaluated by means of bacterial colony count and restriction analysis. After two rounds of panning with gastric cancer cell line KATOIII of highly expressing MG₇-binding antigen, the phage clones displaying ScFv of the antibody were selected by ELISA from the enriched phage clones. The antigen binding affinity of the positive clone was detected by competition ELISA. HB2151 E.coli was transfected with the positive phage clone demonstrated by competition ELISA for production of a soluble form of the MG₇ ScFv. ELISA assay was used to detect the antigen-binding affinity of the soluble MG₇ ScFv. Finally, the relative molecular mass of soluble MG₇ ScFv was measured by SDS-PAGE.

RESULTS: The V-H, V-L and ScFv DNAs were about 340 bp, 320 bp and 750 bp, respectively. The volume of the library was up to 2 × 10⁶ and 8 of 11 random clones were recombinants. Two phage clones could strongly compete with the original MG₇ antibody for binding to the antigen expressed on KATOIII cells. Within 2 strong positive phage clones, the soluble MG₇ ScFv from one clone was found to have the binding activity with KATOIII cells. SDS-PAGE showed that the relative molecular weight of soluble MG₇ ScFv was 32.

CONCLUSION: The MG₇ ScFv was successfully produced by phage antibody technology, which may be useful for broadening the scope of application of the antibody.

Expression of vascular endothelial growth factor and its role in oncogenesis of human gastric carcinoma

AIM

To establish the role of vascular endothelial growth factor (VEGF) in the oncogenesis of human gastric carcinoma more directly.

METHODS

The expression of VEGF and its receptor kinase-domain insert containing receptor (KDR) in human gastric cancer tissue were observed by immunohistochemical staining. VEGF levels were manipulated in human gastric cancer cell using eukaryotic expression constructs designed to express the complete VEGF(165) complimentary DNA in either the sense or antisense orientation. The biological changes of the cells were observed in which VEGF was up-regulated or down-regulated.

RESULTS

VEGF-positive rate was 50%, and VEGF was mainly localized in the cytoplasm and membrane of the tumor cells, while KDR was mainly located in the membrane of vascular endothelial cells in gastric cancer tissues and peri-cancerous tissue. In 2 cases of 50 specimens, the gastric cancer cells expressed KDR, localized in both the cytoplasm and membrane. Introduction of VEGF(165) antisense into human gastric cancer cells (SGC-7901, immunofluorescence intensity, 31.6%)) resulted in a significant reduction in VEGF-specific messenger RNA and total and cell surface VEGF protein (immunofluorescence intensity, 8.9%) (P<0.05). Conversely, stable integration of VEGF(165) in the sense orientation resulted in an increase in cellular and cell surface VEGF (immunofluorescence intensity, 75.4%) (P<0.05). Lowered VEGF levels were associated with a marked decrease in the growth of nude mouse xenografted tumor (at 33 days postimplantation, tumor volume: 345.40 +/- 136.31 mm3)(P<0.05 vs control SGC-7901 group: 1534.40 +/- 362.88 mm3), whereas up-regulation of VEGF resulted in increased xenografted tumor size (at 33 days postimplantation, tumor volume: 2350.50 +/- 637.70 mm3) (P<0.05 vs control SGC-7901 group).

CONCLUSION

This study provides direct evidence that VEGF plays an important role in the oncogenesis of human gastric cancer.

Detection of circulating gastric carcinoma-associated antigen MG7-Ag in human sera using an established single determinant immuno-polymerase chain reaction technique

BACKGROUND

In 1994, a novel sensitive method termed immuno-polymerase chain reaction (PCR) for the detection of the gastric carcinoma-associated antigen MG7-Ag in the gastric carcinoma cell line KATO III was reported. Compared with the enzyme-linked immunoadsorbent assay, the single determinant immuno-PCR technique could allow for as few as 20 cells to be detected and was found to show an approximately 10,000-fold enhancement in sensitivity of the detection limit. The current study clinically evaluated the significance of serum MG7-Ag detection in gastric carcinoma patients.

METHODS

The sera of patients were immobilized on wells and a specific DNA molecule, which could be amplified by PCR, was employed as a marker. The biotinylated monoclonal antibody against gastric carcinoma was added to bind the antigen immobilized on the wells. After the biotinylated antibody was bound to the antigen, free avidin was used to attach a biotinylated monoclonal antibody and biotinylated DNA molecule. The biotinylated DNA complexed with antigen-antibody-avidin was amplified by PCR and the PCR products were analyzed by agarose gel electrophoresis. In the current study this method was used to detect circulating MG7-Ag in the sera of patients with gastric carcinoma and other various malignancies. For comparison, carcinoembryonic antigen, CA 50, CA 19-9, and TAG-72 were quantitated by radioimmunoassay and immunoradiometric assay using the relevant commercial kits in the same sera samples from 86 patients with pathologically confirmed gastric carcinoma and 83 patients with relevant benign diseases of the stomach. In addition, the semiquantitative analysis of PCR products among gastric carcinoma patients with or without metastasis was performed to compare the intensity of DNA band amplification.

RESULTS

Using the immuno-PCR assay, positive results were obtained in 164 of 198 patients with gastric carcinoma (82.8%). The rates of positivity in other malignancies were 17.4% for esophageal carcinoma (15 of 86 patients), 44.4% for colonic carcinoma (40 of 90 patients), 0% for liver carcinoma (none of 84 patients), 2.2% for ovarian carcinoma (1 of 45 patients), 0% for uterine carcinoma (none of 27 patients), and 6.1% for lung carcinoma (4 of 66 patients). The positive results obtained from those patients with benign diseases were: 7.7% for peptic ulcer (6 of 78 patients), 5.9% for chronic gastritis (7 of 118 patients), 3.3% for chronic colitis (2 of 60 patients), and 0.8% for healthy blood donors (2 of 236 patients). In addition, the semiquantitative analysis of PCR products showed that the intensity of DNA band amplified from the PCR products of those patients with metastasis was much higher than that of patients without metastasis or those with early stage tumors (1.94 +/- 0.03 vs. 1.28 +/- 0.02). In comparative studies of immuno-PCR and commercial assays for tumor-associated antigens the sensitivity of immuno-PCR was 81.4% and pseudopositivity was lower (8.4% vs. 7.2-12.0% with radioimmunoassay or immunoradiometric assay).

CONCLUSIONS

The results of the current study demonstrate that introducing PCR into the indirect determination of tumor-associated antigen in the serum can improve the sensitivity of detection greatly. This novel assay also might be used to monitor the circulating amount of tumor-associated antigen after gastrectomy and provide information regarding recurrence or metastasis, as well as for screening elderly patients who have no indications for endoscopy and those with precancerous conditions. The application of immuno-PCR in the serologic diagnosis of carcinoma has significant advantages including ready application in the clinical setting as well as use as a potential screening tool in mass surveys of high risk populations with gastric carcinoma. (c) 2000 American Cancer Society.

[Establishment of immuno-PCR technique for the detection of tumor associated antigen MG7-Ag on the gastric cancer cell line]

The gastric cancer associated antigen McAb MG7-Ag was detected by means of a newly established method, termed immuno-PCR. A McAb-recombinant DNA chimeric molecule was made which possesses bispecific binding affinity for antigen that had been immobilized on microtiter wells and the segment of the attached DNA was amplified by PCR. The antigen of gastric cancer cell line KATO III was monitored by this method. Analysis of PCR products by agarose gel electrophoresis after staining with ethidium bromide allowed as few as 20 cells to be detected readily and reproducibly. Immuno-PCR showed a 10(4) enhancement in detection sensitivity compared with ELISA assay. When the same numbers of cells (2 x 10(6)/ml) were immobilized and then the serial diluted chimeric molecule was added, 3.8 x 10(-14) moles and 3.0 x 10(-11) moles were needed to give positive results with the immuno-PCR and ELISA assay, respectively. Therefore, immuno-PCR could give an enormous amplification capability with good specificity, and has a sensitivity much higher than any existing techniques for antigen detection.

Detection of antigen-specific immune complexes in sera of gastric and esophageal cancer patients

Using the murine monoclonal antibodies against human gastric cancer cell antigens designated MG7 and MGd1, we developed a sandwich ELISA to detect the levels of antigen-specific immune complexes (IC) in human sera. By this assay, only 6.7%(6/90) of healthy blood donors and 9.2%(6/65) of patients with chronic gastritis had antigen-specific IC in sera exceeding the cut-off value. Whereas 21.4%(6/28) of patients with colorectal cancer, 18.2%(4/22) of patients with hepatocellular cancer, 11.4%(4/35) of patients with lung cancer and 9.5%(2/21) of patients with breast cancer had elevated levels of the antigen-specific IC. In contrast, 58.7%(54/92) of patients with gastric cancer and 53.3%(24/45) of patients with esophageal cancer were positive for this antigen-specific IC. Determination of levels of antigen-specific IC in sera may be useful in serologic diagnosis of patients with gastric and esophageal cancer.

Specific targeting of mitomycin C to tumors by anti-gastric cancer monoclonal antibody

In the present study, an anti-gastric cancer monoclonal antibody, MGb2, was chosen to prepare antibody-mitomycin C (MMC) conjugate with dextran T-40 as intermediary. Twenty molecules of MMC were introduced into each molecule of antibody while the antigen-binding capacity of the antibody was kept well. The conjugate showed selective cytotoxicity upon human gastric cancer cell line SGC-7901. Radioimmunoimaging and biodistribution studies indicated that after conjugation with MMC via dextran T-40 as intermediary, the tumor localization capacity of the antibody was well retained. When tested in nude mice, inoculated with human gastric carcinoma SGC-7901 in bilateral subrenal capsules, intraperitoneal injection of the conjugate daily for 6 days at a dose of 1 mg/kg gave a tumor inhibitory rate of 68.67%, which was far better than that of free MMC or irrelevant conjugate. No synergetic effect was found in regard to the mixture of MGb2 with MMC.

Diagnostic significance of gastric cancer associated antigens (MG-AGS) in serum, ascitic fluid and gastric juice

A group of monoclonal antibodies against gastric cancer, pooled in equal proportions, was used to investigate their corresponding antigens (MG-Ags) in serum and body fluid of patients with gastrointestinal cancer and benign diseases using microsphere-ELISA method. The mean serum level (plus 3 standard deviations) in 59 normal subjects was arbitrarily set as the positive threshold value. The positive rate was found to be 68.8% (135/196) in sera of patients with gastric cancer, 70% (14/20) in colonic cancer, 72.2% (24/33) in rectal cancer, 43.8% (7/16) in esophageal cancer, 45.5% (5/11) in cholecystic cancer and 34.9% (15/43) in lung cancer, which, however, was not found in primary liver cancer, pancreatic cancer and ovarian cancer. In 214 patients with benign diseases, a false positive rate was 7.48%. In gastric juice and ascitic fluid of patients with gastric cancer, the positive rates were found to be 61.7% (27/44) and 83.3% (20/24) respectively. These antigens were also determined repeatedly in sera of patients with gastric cancer who had undergone gastrectomy. It was found that the level of MG-Ags in sera began to decrease at 8-10 days after operation. These results suggest that the determination of MG-Ags is useful in the diagnosis of gastrointestinal cancer and evaluation of the treatments.

Purification and partial characterization of a new group of gastric cancer associated antigens

The corresponding antigens of MG series monoclonal antibodies (MG5, MG9, MGd1 and MGe1) against gastric cancer were purified and partially characterized. Each of these monoclonal antibodies was purified by passing through a DEAE-52 cellulose columns and covalently coupled with CNBr-activated sepharose 4B successively. By means of concanavalin A and antibody affinity chromatography, the corresponding antigens of MG series McAb were extracted from gastric cancer tissue respectively. Immunological and biochemical studies confirmed that the corresponding antigens of MG series McAb were a new group of gastric cancer associated neutral glycolipid and glycoprotein antigens.

Preparation of antigastric cancer monoclonal antibody MGb2-mitomycin C conjugate with improved antitumor activity

In the present study, an antigastric cancer monoclonal antibody, MGb2, was chosen to prepare antibody-mitomycin C conjugate with dextran T-40 as intermediary. Up to 20 molecules of mitomycin C were specifically bound per molecule of antibody, without significantly impairing the antigen-binding capacity of the antibody and the pharmacological activity of mitomycin C. The conjugate showed selective cytotoxicity upon human gastric cancer cell line SGC-7901 in vitro. Radioimmunoimaging and biodistribution studies indicated that, after conjugation with mitomycin C via dextran T-40 as intermediary, the tumor localization capacity of the antibody was well-retained. When tested in nude mice inoculated with human gastric carcinoma GAII in bilateral subrenal capsules, intraperitoneal injection of the conjugate twice a week for 3 weeks at the dose of 1 mg/kg of drug gave a tumor inhibitory rate of 152.29%, the result being far better than that of free mitomycin C or an irrelevant conjugate. A similar result was found in another nude mouse model of human gastric carcinoma SGC-7901. Meanwhile, after conjugation with antibody, the toxicity of mitomycin C on tested animals was significantly reduced.

Targeted anti-tumor agents and their cytotoxicity on gastric cancer cells in vitro

Several chemotherapeutic drugs including methotrexate, daunomycin, mitomycin C and toxin such as ricin, A chain of ricin were chosen to conjugate with murine monoclonal antibodies MGb2 and MG11. The drugs were linked to antibody directly or through human serum albumin as intermediary. The ELISA results showed that the antibody retained well the antigen-binding capacity during conjugation. These conjugates showed highly selective cytotoxic effect on target cells. In chronic cytotoxicity tests, the cytotoxic effect of these conjugates on human gastric cancer cells KATOIII was quite similar to that of free drugs or ricin, but greater than that of irrelevant conjugates, while they had a little effect on non-target cells, suggesting that the selective cytotoxicity on target cells of the conjugates be mediated by antibodies.

Immunohistochemical study of monoclonal antibody MGD-1 in gastric carcinoma

This paper reports a pathological and immunohistochemical study of gastric carcinoma for immunoreactivity with a monoclonal antibody. MGD-1, raised against cells from an adenocarcinoma of stomach. Fifty-four of 61 gastric carcinomas (89%) were positive for MGD-1. Metastatic gastric carcinoma in local nodes was positive in all 11 such cases. Out of 40 examples of chronic atrophic gastritis, only three, with mild dysplasia, were positive (7.5%). Forty cases with normal gastric mucosa were negative. The MGD-1 detection-rate of well- and poorly-differentiated gastric carcinoma was 85% and 93% respectively. The metastatic cells and cells infiltrating the submucosa and muscular layer were more frequently positive and showed stronger staining with MGD-1 than those in mucosa. These results show that MGD-1 possesses a high degree of specificity for gastric carcinoma and could be used diagnostically.