Preparation of monoclonal antibody against apoptosis-associated antigens of hepatoma cells by subtractive immunization

One-Step Platform for Maduramicin and Salinomycin Detection Based on Bispecific Monoclonal Antibody and Interpretation of Molecular Recognition Mechanism

Maduramicin (MAD) and salinomycin (SAL) are the widely used poly(ether ionophore) antibiotics to control coccidiosis in animals. Due to their strong cytotoxicity, strict control over their dosage and residue in animal food is necessary. To improve the detection efficiency of the existing single-residue detection methods, a tetraploid tumor hybrid system was constructed using drug mutagenesis, and the bispecific monoclonal antibody (BsMAb) against MAD and SAL was obtained by hybridization-hybridoma technology. By optimizing the optimal working concentration of the tracer and antibody, a multiresidue fluorescence polarization immunoassay method based on BsMAb was successfully established. The whole detection process takes 10 min, and the LOD values of MAD and SAL were 4.71 and 3.49 ng·g-1, respectively. IC50 values were 6.45 and 6.24 ng·mL-1, respectively. There was no cross-reactivity with other polyether ionophore antibiotics. Finally, a breakthrough in detection was achieved: bispecific monoclonal antibody prepared by the hybridization-hybridoma technology was used to detect maduramicin and salinomycin.

Exploration of the hepatoprotective effect and mechanism of magnesium isoglycyrrhizinate in mice with arsenic trioxide‑induced acute liver injury

Arsenic trioxide (ATO)-induced hepatotoxicity limits the therapeutic effect of acute myelogenous leukemia treatment. Magnesium isoglycyrrhizinate (MgIG) is a natural compound extracted from licorice and a hepatoprotective drug used in liver injury. It exhibits anti-oxidant, anti-inflammatory and anti-apoptotic properties. The aim of the present study was to identify the protective action and underlying mechanism of MgIG against ATO-induced hepatotoxicity. A total of 50 mice were randomly divided into five groups (n=10/group): Control; ATO; MgIG and high- and low-dose MgIG + ATO. Following continuous administration of ATO for 7 days, the relative weight of the liver, liver enzyme, histological data, antioxidant enzymes, pro-inflammatory cytokines, cell apoptosis and changes in Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2) signaling pathway were observed. MgIG decreased liver injury, decreased the liver weight and liver index, inhibited oxidative stress and decreased the activity of glutathione, superoxide dismutase and catalase, production of reactive oxygen species and levels of pro-inflammatory cytokines, including IL-1β, IL-6 and TNF-α. Western blotting showed a decrease in Bax and caspase-3. There was decreased cleaved caspase-3 expression and increased Bcl-2 expression. MgIG notably activated ATO-mediated expression of Keap1 and Nrf2 in liver tissue. MgIG administration was an effective treatment to protect the liver from ATO-induced toxicity. MgIG maintained the level of Nrf2 in the liver and protected the antioxidative defense system to attenuate oxidative stress and prevent ATO-induced liver injury.

A rapid subtractive immunization method to prepare discriminatory monoclonal antibodies for food E. coli O157:H7 contamination

To detect food E. coli O157:H7 contamination rapidly and accurately, it is essential to prepare high specific monoclonal antibodies (mAbs) against the pathogen. Cyclophosphamide (Cy)-mediated subtractive immunization strategy was performed in mice to generate mAbs that react with E. coli O157:H7, but not with other affiliated bacteria. Specificity of 19 mAbs was evaluated by ELISA and/or dot-immunogold filtration assay (DIGFA). Immunogloubin typing, affinity and binding antigens of 5 selected mAbs were also analysed. MAbs 1D8, 4A7, 5A2 were found to have high reactivity with E. coli O157:H7 and no cross-reactivity with 80 other strains of bacteria including Salmonella sp., Shigella sp., Proteus sp., Yersinia enterocolitica, Staphylococcus aureus, Klebsiella pneumoniae, Citrobacter freundii and other non-E. coli O157:H7 enteric bacteria. Their ascetic titers reached 1∶10⁶ with E. coli O157:H7 and affinity constants ranged from 1.57×10¹⁰ to 2.79×10¹⁰ L/mol. The antigens recognized by them were different localized proteins. Furthermore, immune-colloidal gold probe coated with mAb 5A2 could specifically distinguish minced beef contaminated by E. coli O157:H7 from 84 other bacterial contaminations. The Cy-mediated subtractive immunization procedure coupled with hybridoma technology is a rapid and efficient approach to prepare discriminatory mAbs for detection of E. coli O157:H7 contamination in food.

Preparation and identification of monoclonal antibody against human hepatocellular carcinoma with a novel immunization

The purpose of this study was to prepare and identify a novel monoclonal antibody (MAb) against human primary hepatocellular carcinoma (PHC) with high specificity and activity. The hepatocellular carcinoma cell line HepG2 was used to immunize BALB/c mice for preparing MAb with the classic hybridoma production technique. Tail vein injection immunization combined with intrasplenic injection was applied for improvement. Immunoperoxidase staining studies showed that the MAb was reactive to HepG2 and another hepatocellular carcinoma cell line, SMMC7721, 98.5% (67/68) specimens of hepatocellular carcinoma, but not to normal human liver tissues and tissues derived from the other malignant tumors, except one of the five specimens of cholangiocarcinoma with dubious staining. Laser confocal scanning microscope (LCSM) analysis indicated that the MAb reacted with the whole cell, including the membrane fractions and the cytoplasm. The hybridoma cell contained 103 +/- 5 chromosomes, and the MAb was identified as IgM subclass by ELISA. It was concluded that this combined immunization can effectively produce highly specific MAb against PHC, and this MAb may be of potential use as a targeting agent for radionuclide therapy and chemotherapy for hepatocellular carcinoma.

Caspase-3 gene transfected with LIGHT gene: can it be used for therapy of human hepatocellular carcinoma?

BACKGROUND

The aim of this study was to detect the expression of apoptosis factor caspase-3 in transferred HepG2 cells and provide feasible evaluation of the treatment for primary liver cancer with gene methods.

METHODS

The pcDNA4C-LIGHT cDNA was extracted from Escherichia coli JM-109; then, the pcDNA4C-LIGHT cDNA was transferred into the HepG2 cells by a cationic liposome mediated method. Meanwhile, the blank group was established as the control group and the HepG2 cells were collected after transfection at 12 h, 24 h, 48 h, 3 days and 5 days. The expression of caspase-3 was identified in the supernatants by ELISA. A standard curve was generated for the set of samples assayed. Statistical significance was analyzed by SPSS.

RESULTS

The quantity of caspase-3 protein was the greatest at 48 h and the least on day 5. The secretion of caspase-3 did not increase in the control group. The coefficient of correlation was equal to 0.9986 and had evident significance.

CONCLUSIONS

The pcDNA4C-LIGHT was effectively transfected in human HepG2 cells mediated by liposome. The expression of caspase-3 increased in the transfected group. This study provides necessary theoretic support for the treatment of liver cancer with gene methods.

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Screening and identification of target genes differentially expressed in HepG2 cells treated with arsenic trioxide by suppression subtractive hybridization technique

AIM: To clone and identify human genes differentially expressed in human hepatocarcinoma HepG2 cells treated with arsenic trioxide by constructing a subtractive cDNA library with suppression subtractive hybridization (SSH) technique, and to elucidate the molecular mechanism of arsenic trioxide in the regulation of liver cells.

METHODS: The mRNA was isolated from HepG2 cells treated with arsenic trioxide and PBS, respectively, and then cDNA was synthesized. After digestion of restriction enzyme RsaI, small sizes cDNA were obtained. Then the tester cDNA was subdivided into two portions and each was ligated with a different cDNA adaptor. After the tester cDNA was hybridized with driver cDNA (twice) and underwent nested polymerase chain reaction (PCR) (twice), the DNA fragment was subcloned into T/A plasmid vectors to establish the subtractive cDNA library. Amplification of the library was performed in E. coli strain JM109. The amplified cDNA was sequenced and analyzed in GenBank with BLAST search after colony PCR.

RESULTS: The subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully. The amplified library contained 109 positive clones. Colony PCR showed that these clones all contained 200-1 000 bp inserts. Thirty-six clones were analyzed by sequencing and bioinformatics. The results showed there were 15 coding sequences with known function and 6 novel ones with unknown function.

CONCLUSION: A subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully using SSH technique.

Preparation and functional characterization of the monoclonal antibody HAb18Gedomab1

AIM: To obtain mouse anti-human monoclonal antibodies against recombinant extracellular domain of HAb18G (HAb18Ged), and to analyze and identify its character and biological function.

METHODS: Balb/c mice were immunized with HAb18Ged. Hybridoma cell was screened by cell fusion and subcloning approach. The monoclonal antibody in the ascites was purified by ion exchange chromatography and was identified by fluorescence-activated cell sorting analysis (FACs) and immunohistochemistry. Gelatin zymography and collagenase type I zymography were used to analyze the effects of HAb18Gedomab1 on activation and production of matrix metalloproteinase (MMPs); Matrigel-boyden degradation chamber method was used to evaluate the infiltrative cells ratio.

RESULTS: A hybridoma cell HAb18Gedomab1 stably secreting anti-HAb18Ged monoclonal antibody was obtained. The titer of this McAb in ascites was 1:10⁶. The purity of the McAb was higher than 90%. The McAb belonged to IgG1 subclass. HAb18Gedomab1 showed high specificity and affinity to the antigen of FHCC-98 cell membrane and the tissue of hepatocellular carcinoma. The McAb induced production and activation of MMP-2, MMP-9, MMP-1 and MMP-8 in mouse fibroblast cells (3T3), and also promoted the degradation of reconstituted basement membrane.

CONCLUSION: HAb18Gedomab1 can bind specifically to HAb18Ged protein. The McAb can also induce production and activation of MMPs and promote the degradation of reconstituted basement membrane.

Anti-hepatoma effect and its mechanism of arsenic trioxide on experimental liver cancer

AIM: To study the synergistic anti-hepatoma efficacy of arsenic trioxide (As₂O₃) and matrine in the treatment of experimental rat hepatocellular carcinoma (HCC) induced by 2-acetamidofluorene (2-FAA) and to elucidate the possible mechanisms.

METHODS: SD rats (2 mo old) were fed with 2-FAA for 8 weeks to induce HCC, then treated with As₂O₃ and matrine. On day 29, we weighed the liver and counted liver tumors. The histological changes of the liver were observed under microscope, and the cellular dynamic parameters were studied by flow cytometry. Immunohistochemistry (two-step method) was used to observe the expression of vascular endothelial growth factor (VEGF) and to show micro-vessel density (MVD) on consecutive sections. The pathological parameters were analyzed at the same time. The levels of serum AST, ALT, TBi and DBi were also investigated.

RESULTS: The number of liver tumors decreased significantly in groups treated with As₂O₃, especially in middle-dose (1 mg/kg) group (P < 0.01). Treatment with As₂O₃ caused HCC cell death via apoptosis. Necrosis was seldomly found and apoptosis was common when the dose was appropriate (1 mg/kg). Proliferation index (PI) decreased sharply in middle-dose (1 mg/kg) group (P < 0.01), but not in another (0.2 mg/kg) group (P > 0.05). However, S phase fraction (SPF) decreasd dramatically in the two groups, it reached the top only when the dose (1 mg/kg) was appropriciate (P < 0.01), and it was obviously accompanied with accumulation of cells in G₀/G₁ (G₀/G₁ restriction). The inhibitory effects of As₂O₃ on HCC cells were not significantly enhanced by matrine. Comparied with single treatment with As₂O₃ 1 mg/kg or 0.2 mg/kg, G₀/G₁ phase cells in the group of combination treatment with As₂O₃ 1 mg/kg or 0.2 mg/kg and matrine 4.2 g/kg did not increased, and apoptostic cells with fractional DNA content did not increased either. The expression of VEGF and MVD was significantly lower in middle-dose (1 mg/kg) group (P < 0.01) than that in normal saline group. In comparison with normal saline group, administration of As₂O₃ or/and matrine lowered the levels of AST in serum (P < 0.05), but had no effect on the amount of serum AST, TBi and DBi (P > 0.05).

CONCLUSION: Arsenic trioxide inhibits growth of experimental hepatocellular carcinoma in rats induced by 2-acetamidofluorene, but As₂O₃ has no obvious effect on the normal hepatic cells. The mechanisms may involved in decreasing cell mitosis, accumulating cells in G₀/G₁ phrase, inducing apoptosis of tumer cells, and having inhibitory effects on the angiogeninase through inhibiting vascular endothelial growth factor. Matrine with As₂O₃ has not significantly synergistic anti-hepatoma effects.

Screening and identification of mimotope of gastric cancer associated antigen MGb1-Ag

AIM: Using a monoclonal antibody against gastric cancer antigen named MGb1 to screen a phage-displayed random peptide library fused with coat protein pIII in order to get some information on mimotopes.

METHODS: Through affinity enrichment and ELISA screening, positive clones of phages were amplified. 10 phage clones were selected after three rounds of biopanning and the ability of specific binding of the positive phage clones to MGb1-Ab were detected by ELISA assay (DNA sequencing was performed and the amino acid sequences were deduced) By blocking test, specificity of the mimic phage epitopes was identified.

RESULTS: There were approximately 200 times of enrichment about the titer of bound phages after three rounds of biopanning procedures. DNA of 10 phage clones after the third biopanning was assayed and the result showed that the positive clones had a specific binding activity to MGb1-Ab and a weak ability of binding to control mAb or to mouse IgG. DNA sequencing of 10 phage clones was performed and the amino acid sequences were deduced. According to the homology of the amino acid sequences of the displayed peptides, most of the phage clones had motifs of H(x)Q or L(x)S. And these 10 phage clones could also partly inhibit the binding of MGb1-Ab to gastric cancer cell KATO-III. The percentage of blocking was from (21.0 ± 1.6)% to (39.0 ± 2.7)%.

CONCLUSION: Motifs of H(x)Q and L(x)S selected and identified show a high homology in the mimic epitopes of gastric cancer associated antigen. There may be one or more clones which can act as candidates of tumor vaccines.

In vivo antitumour activity of PBMCs via genetic modification of single-chain immunotoxin

AIM

To investigate In vivo antitumour activity of single-chain immunotoxin (sFv-TNF-α fusion protein).

METHODS

HCC-specific killer cells were generated by transducing the recombinant retroviral virus in supernatant of the virus producing cells (C₂₂) into human peripheral blood mononuclear cells (PBMCs). SMMC-7721 xenograft nude mice were given iv either 1×10⁶ (0.2 mL) transduced or mock-transduced PBMCs once five days for three weeks and tumour growth was detected.

RESULTS

Tumour growth were (20.8±4.9) mg/d in PBMCs/PST group and (28.5±6.7)mg/d in PBMCs/ pLXSN group, with a significant difference (P<0.05).

CONCLUSION

Genetic modification of PBMCs by single-chain immunotoxin has antitumour activity In vivo.

Effect of arsenic trioxide on rat hepatocarcinoma and its renal cytotoxicity

AIM: To study the effect of arsenic trioxide (As₂O₃) on rat experimental hepatocarcinoma and its renal cytotoxicity.

METHODS: The hepatocarcinoma model was established by diethaylnitrosamine perfusion in stomach of 120 Wistar rats, and the treatment began at the end of 20 weeks. Before the treatment, the rat models were randomly divided into 5 groups. In the treatment groups, three doses of As₂O₃ were injected into rat abdominal cavity, the total time of drug administration was 4 weeks. Cisplatin control or the blank group was injected into abdominal cavity with equal amount of cisplatin or saline at the same time, respectively. On the 7^th, 14^th and 28^th day after the treatment, the hepatocarcinoma nodules were obtained and the morphologic changes of hepatocarcinoma cells were observed under light and electron microscopes; Immunohistochemistry (S-P methods) was employed to detect the expression of bcl-2, bax and PCNA in hepatocarcinoma tissues; flow cytometry (TUNEL assay) was used to detect the apoptosis of liver cancer cells and the change of cytokinetics. On the 28^th day, the kidneys were obtained and their histologic changes were observed under light microscope, and immunohistochemistry (SP stain) was also employed to detect the expression of bcl-2 and PCNA. Cisplatin and saline solution were used as the control.

RESULTS: As₂O₃ could induce the apoptosis of rat liver cancer cells and exhibited typical morphologic changes. The incidence of apoptosis of hapatocarcinoma cells was elevated (P = 0.001). The elevation was the most higher in the group of middle-dose of As₂O₃ (1 mg·kg^-1), significantly higher than that of the other arsenic groups and the controls (P = 0.001). Large dose of As₂O₃ (5 mg·kg^-1) was able to arise the incidence of apoptosis, but also produced a large amount of necrosis and inflammatory reaction. Middle dose of As₂O₃ dramatically increased the cell number in G2/M phase (P = 0.0001), and apoptosis happened apparently. The expression of bcl-2 and bax was related to the dose of As₂O₃. With the up-regulation of apoptotic incidence, the ratio of bcl-2/bak decreased. But the incidence of apoptosis was not the highest status and the ratio of bcl-2/bax was at the lowest when the highest-dose of As₂O₃ was used. There was significant difference among the PCNA indexes (PCNA L1) of the five groups. Of them, three arsenic groups all showed decrease of different degrees, and this down-regulation was most obvious in group A. There was significant difference among the three groups (P = 0.016). Under the light microscope, the rat kidney in the cisplatin group exhibited tubular epithelium swelling and degeneration, protein casts in collecting tubules; While all arsenic groups didn’t show the significant changes (P = 0.013). In the arsenic groups, the expression of bcl-2 in the renal tubular epithelium was increased (P = 0.005), no obvious changes happened to PCNA L1. But in the group of cisplatin, the PCNA L1 increased significantly (P = 0.001).

CONCLUSION: As₂O₃ can induce apoptosis of rat hepatocellular carcinoma cells. And there is optimum dose; too high dose will induce the cytotoxic effect, while certain dose of As₂O₃ is able to block the cell cycle at G2/M phase. As₂O₃ had the most remarkable influence on G2/M cells, and it can also induce apoptosis to cells at other phases. As₂O₃ can restrain the proliferation of rat hepatocellular carcinoma cells, in a dose-time dependent manner. Compared with cisplatin, As₂O₃ didn’t show obvious renal toxicity, which was related to the increasing expression of bcl-2 in renal tubular epithelium, the inhibition of apoptosis and the anti-oxidation effects.

Laminin induces the expression of cytokeratin 19 in hepatocellular carcinoma cells growing in culture

AIM: To study the abnormal cytokeratin (CK) expression, emergence of CK19 with or without CK7, in liver parenchymal cells and the role of laminin (LN), a basement membrane protein, in this process.

METHODS: Six hepatocellular carcinoma (HCC) cell lines were examined for different CKs, LN and its receptor by immunocytochemistry and Western blotting. Double immunofluorescent reaction, laser-scanning confocal microscopy and an in vitro induction procedure were used to demonstrate the role of LN in regulating CK19 expression in these cells.

RESULTS: Immunoreactivities for CK8, CK18, CK7 and the receptor for LN were observed in all the six HCC cell lines examined. However, CK19 was merely found in four of the six cell lines, and was in any case associated with LN expression. Laser-scanning confocal microscopy demonstrated the concomitant presence of these two molecules in most of the positive cells. In the two HCC cell lines, originally negative for CK19, addition of LN to the culture medium resulted in an induction of CK19 in a dose-dependent manner. Both the artificially induced and the intrinsic production of CK19 were completely blocked by an antibody to LN.

CONCLUSION: LN can induce expression of CK19 in HCC cells in vitro, providing direct evidence for our hypothesis that the abnormal hepatocytic CK19 expression in situ is due to pathologic LN deposition.

Effect of monoclonal antibody 3A5 coupled with Chinese medicine compound Andi in targeted treatment of hepatocellular carcinoma

AIM

To explore the anti-tumor effect of monoclonal antibody 3A5 coupled with Chinese medicine compound Andi injection in targeted treatment of hepatocellular carcinoma(HCC).

METHODS

Monoclonal antibody 3A5 was used to prepare conjugates with Andi powder. The immunoreactivity of the conjugates on human HCC BEL-7402 cell was detected by ELISA. The targeted therapeutic effects of 12, 24 and 50 mg/kg conjugates were observed in mice/nude mice transplantation tumor models. The positive control group was treated with 5-FU.

RESULTS

The detection of clone production indicated that 3A5-Andi has more cytotoxicity than Andi, and their IC50 were 2.8 mg/L and 5.1 mg/L respectively (P < 0.01). The survival rates of 24 mg/kg and 50 mg/kg of 3A5-Andi ip on mice transplantation ascites H22 HCC were 133% and 167% respectively (P < 0.05), but those of 12 mg/kg and 24 mg/kg of Andi only were 112% and 138% respectively (P < 0.05). The inhibitory rates of 24 mg/kg of 3A5-Andi and 12 mg/kg of Andi iv on nude mice transplantated human HCC BEL-7 402 cell tumor were 63.5% and 52.5% respectively (P > 0.05). The inhibitory rates of 24 mg/kg 3A5-Andi and 12 mg/kg Andi pt on human HCC BEL-7402 cell were 75.4% and 61.0% respectively (P > 0.05).

CONCLUSION

3A5-Andi conjugates have a tumor targeted therapeutic effect. This effect is stronger than that of Andi only on nude mice transplanted human HCC BEL-7402, and the administration of pt is better than that of iv.

In vitro cytotoxicity of PBMCs via genetic modification of single-chain immunotoxin

AIM: To investigate the selective cytotoxicity of single-chain immunotoxin (sFv-TNF-α fusion proteins) in cell line SMMC-7721.

METHODS: HCC-specific killer cells were generated by transducing the recombinant retroviral virus in supernatant of the virus producing cells into human peripheral blood mononuclear cells (PBMCs). PCR and RT-PCR were used to detect integration and transcription of the sFv-TNF-α gene in transduced PBMCs (PBMCs/PST). MTT method was used to detect antitumour activity of the sFv-TNF-α fusion proteins.

RESULTS: There was integrated sFv-TNF-α gene in the genome of PBMCs/PST, and PBMCs/PST were able to express the fusion sFv-TNF-α proteins. Cell killing was significant in HCC cells co-cultivated with PBMCs/PST, whereas the PBMCs/pLXSN control cells had no significant cytotoxic effects on HCC cells.

CONCLUSION: Expression of sFv-TNF-α fusion proteins in PBMCs/PST has cytotoxicity to HCC cells in vitro.