Superantigen-SEA gene modified tumor vaccine for hepatocellular carcinoma: An in vitro study

Recombinant Staphylococcal Enterotoxin Type A Stimulate Antitumoral Cytokines

BACKGROUND

About 20 different types of staphylococcal enterotoxins are produced by Staphylococcus aureus, in which type A is more common in food poisoning syndrome. Also staphylococcal enterotoxin A superantigen is a potent inducer of cytotoxic T lymphocyte activity and cytokine production and could stimulate T cells containing T-cell receptor beta chain domains when binding to major histocompatibility complex class II molecules. Hence, it is an important reagent in cancer immunotherapy.

METHODS

For the construction of pET-21a/ entA cassette, the staphylococcal enterotoxin type A gene was isolated from S aureus strain HN2, cloned into pET-21a, and introduced into Escherichia coli strain BL-21(DE3). Consequently, Western blot analysis showed pET-21a/ entA cassette expression inserted entA gene successfully. It is the first prompt using a pET-21a as a cloning vector for entA gene and expression of construct in BL-21(DE3). In addition, this study examined the ability of standard staphylococcal enterotoxin A and cloned staphylococcal enterotoxin A to activate T cells in vitro. Lymphocyte cells derived from lymph node BALB/c mice were exposed to standard staphylococcal enterotoxin A and cloned staphylococcal enterotoxin (1.10, 102,103, and 104 ng/µL) in order to evaluate the magnitude of proliferation, activation, and apoptosis of lymphocyte cells based on MTT and apoptosis assays, respectively.

RESULTS

Our investigation showed that the function of cloned staphylococcal enterotoxin A was same as standard staphylococcal enterotoxin A, and the optimal concentration for the activation of lymphocyte cells and induction of apoptosis was 100 ng/µL and 1000 ng/µL ( P < .05), respectively. Quantification of cytokines clearly showed that lymphocyte cells exposed to standard staphylococcal enterotoxin A and cloned staphylococcal enterotoxin A significantly secreted higher interferon γ and tumor necrosis factor α compared to control.

CONCLUSION

According to our results, the biological activity of standard staphylococcal enterotoxin A and cloned staphylococcal enterotoxin A is identical; therefore, these procedures may be approved as an efficient method to express and purify this protein in a large scale.

Preparation and In Vitro Evaluation of Antitumor Activity of TGFαL3-SEB as a Ligand-Targeted Superantigen

Tumor-targeted superantigens (TTSs) have been used to treat a variety of tumors in preclinical studies. The TTS utilizes the powerful T-cell activation strategy by means of staphylococcal enterotoxins (SEs) as superantigens (Sags) to target tumor cells. Monoclonal antibodies and tumor-related ligands have been used as targeting molecules of Sag. In this study, we assessed the antitumor potency of tumor-targeted superantigen (TTS) strategy to design and produce fusion protein as a new antitumor candidate. The third loop (L3) of transforming growth factor α (TGF-α) was genetically conjugated to staphylococcal enterotoxin type B (TGFαL3-SEB), and its in vitro antitumor activity against murine breast cancer cells (A431 cell line) was evaluated. We designed and prepared TGFαL3-SEB chimeric protein and evaluated superantigenic activity, binding property to cancer cells, overexpression of epidermal growth factor receptor (EGFR), and in vitro antitumor activities. Cloning of tgfαl3-seb was confirmed by colony-polymerase chain reaction, enzymatic digestion, and sequencing. The recombinant TGFαL3-SEB fusion protein with molecular weight of 31 kDa was expressed and confirmed by anti-His Western-blot analysis. The TGFαL3-SEB fusion protein attached to A431 cell line with proper affinity and induced dose-dependent cytotoxicity against EGFR-expressing cancer cells in vitro. The TGFαL3-SEB chimeric protein exhibited potent in vitro antitumor activity. Our findings indicated that TGFαL3-SEB may be a promising anticancer candidate in cancer immunotherapy, and further studies are required to explore its potential in vivo therapeutic applications.

Membrane-tethered proteins for basic research, imaging, and therapy

Secreted and intracellular proteins including antibodies, cytokines, major histocompatibility complex molecules, antigens, and enzymes can be redirected to and anchored on the surface of mammalian cells to reveal novel functions and properties such as reducing systemic toxicity, altering the in vivo distribution of drugs and extending the range of useful drugs, creating novel, specific signaling receptors and reshaping protein immunogenicity. The present review highlights progress in designing vectors to target and retain chimeric proteins on the surface of mammalian cells. Comparison of chimeric proteins indicates that selection of the proper cytoplasmic domain and introduction of oligiosaccharides near the cell surface can dramatically enhance surface expression, especially for single-chain antibodies. We also describe progress and limitations of employing surface-tethered proteins for preferential activation of prodrugs at cancer cells, imaging gene expression in living animals, performing high-throughput screening, selectively activating immune cells in tumors, producing new adhesion molecules, creating local immune privileged sites, limiting the distribution of soluble factors such as cytokines, and enhancing polypeptide immunogenicity. Surface-anchored chimeric proteins represent a rich source for developing new techniques and creating novel therapeutics.

Expression of costimulatory molecule CD80 in colonic dysplasia in ulcerative colitis: an immunosurveillance mechanism against colorectal cancer?

BACKGROUND AND AIMS

Ulcerative colitis is an established risk factor for colorectal cancer but dysplasia reports are much more frequent than invasive neoplasm diagnosis. The effective activation of T lymphocytes that provide antitumor surveillance requires the presence of costimulation molecules such as CD80 and CD86 on the surface of antigen-presenting cells. The aim of our study was to verify the presence of an in vivo immunosurveillance mechanism in the early stages of colon tumorigenesis.

PATIENTS AND METHODS

Expression of CD80, CD86, and IFN-gamma in the colonic mucosa of 21 consecutive ulcerative colitis (UC) patients was quantified using reverse transcription polymerase chain reaction. After a 7-year follow-up period, we reviewed the histology of all surveillance colonoscopy specimens for colonic dysplasia. Correlation, frequency, and survival analyses were performed.

RESULTS

CD80 was detectable in seven patients while expression of CD86 and IFN-gamma was evident in all patients. Histology confirmed the presence of dysplasia in eight patients. Patients who had dysplasia showed higher CD80 levels compared to those without dysplasia (p=0.02). Survival analysis demonstrated that cumulative dysplasia rates of CD80-positive patients were significantly higher than those of CD80-negative patients (p=0.04).

CONCLUSION

Even if partially limited by a relatively small sample size, our study seems to show an association between CD80 expression and colonic dysplasia in UC patients that may suggest a role for CD80 in the immunosurveillance against colorectal cancer in this early stage of tumorigenesis. On the contrary, CD86 seems to be involved in the inflammatory pathogenesis of UC.

Immunomodulation by SanPharma Fungal Metabolic Products

OBJECTIVE

In the present study, a series of fungal metabolite products from SanPharma (Dohren, Germany) were tested for effects on human peripheral blood leukocytes in vitro using standard immunologic methods.

BACKGROUND

Therapeutic strategies used in German biological medicine often include treatment (oral, nasal, rectal, topical, or injection) with fungal or bacterial products, also known as "isopathic remedies," of which some are limited to metabolic products, whereas others include microbial cell lysates and cell wall fragments as well. The SanPharma products are based on metabolites, and do not contain microbial cell wall compounds.

METHODS

Activation of natural killer (NK) cells was evaluated by cell surface immunostaining using CD3, CD56, CD69, and CD25 monoclonal antibodies. Production of interferon-gamma was evaluated by enzyme-linked immunoabsorbent assay (ELISA) on supernatants collected after 5 days' culture of peripheral blood mononuclear cells (PBMC). Direct mitogenic effect was assessed using the lipophilic membrane dye PHK26 (Sigma-Aldrich, St. Louis, MO) in a fluorescence-based proliferation assay, in which fluorescence intensity is reduced upon cell divisions. Cell viability upon exposure to fungal metabolites was assessed using propidium iodide staining and flow cytometry.

RESULTS

All fungal metabolite products specifically induced the expression of the CD69 marker on human CD3-negative, CD56-positive NK cells, but not CD3-positive T cells, in vitro, as shown by the induction of the CD69 marker on up to 50% of NK cells after 18 hours' culture with metabolites. Only one of the five metabolite products, Roqueforti, induced cyclooxygenase-2 (COX-2), indicating that nuclear factor-kappaB (NFkappaB)-mediated signaling may not have been involved in the NK activation by the other four products. The Notatum product reduced baseline levels of COX-2, indicating an anti-inflammatory effect. No evidence of toxic or mitogenic effects was found.

CONCLUSIONS

The fungal metabolite products from SanPharma specifically activate human NK cells in vitro.

Significance and relationship between infiltrating inflammatory cell and tumor angiogenesis in hepatocellular carcinoma tissues

AIM: To investigate the relationship between infiltrating inflammatory cell and tumor angiogenesis in hepatocellular carcinoma (HCC) tissues and their clinicopathological features.

METHODS: The paraffin-embedded specimens from 70 cases with HCC were stained using EliVision immunohistochemistry with mAbs against CD68, tryptase, and CD34. The counts of tumor-associated macrophage (TAM), mast cell (MC) and tumor microvessel (MV) were performed in the tissue sections.

RESULTS: The mean counts of TAM, MC, and MV in HCC tissues were significantly higher than those in pericarcinomatous liver tissues (TAM: 69.31 ± 11.58 vs 40.23 ± 10.36; MC: 16.74 ± 5.67 vs 7.59 ± 4.18; MV: 70.11 ± 12.45 vs 38.52 ± 11.16, P<0.01). The MV count in the patients with metastasis was markedly higher than that with non-metastasis (P < 0.01). In addition, the MC count in the patients with poorly differentiated HCC was obviously higher than that with well differentiated HCC (P < 0.01). The correlation analysis showed that the TAM count was significantly correlated with the count of MV (r ＝ 0.712, P < 0.01), and the MC count was obviously correlated with the MV count (r ＝ 0.336, P < 0.05).

CONCLUSION: TAM and MC might be closely related to the enhancement of tumor angiogenesis. The MV count might be associated with tumor invasion and metastasis. Moreover, the MC count might be associated with tumor differentiation and prognosis of HCC.

Immunotherapeutic strategies for hepatocellular carcinoma

There is a continuing need for innovative, alternative therapies for hepatocellular carcinoma (HCC). Immunotherapy for cancer is attractive because of the exquisite specificity of the immune response. Activation of an HCC-specific response can be accomplished by strategies targeting tumor-associated self-antigens (for example, alpha-fetoprotein [AFP]). Gene array studies have added to the list of HCC-specific gene products that can be targeted. Alternatively, the immune response can be targeted against viral antigens in those patients infected with hepatitis B or C virus. Uncharacterized and mutated antigens can also be targeted with whole tumor cell or tumor lysate-based immunization strategies or with vectors coding for genes that make the tumor immunogenic, allowing the immune system to naturally evolve specificity against immunogenic target antigens. Strategies being investigated in animal models include increasing tumor immunogenicity by targeting cytokines or costimulatory molecules to tumor; immunization with tumor cells fused with antigen-presenting cells; adoptive transfer of viral antigen-specific T cells; and targeting AFP-expressing HCC cells by DNA, adenovirus, peptide, and dendritic cell (DC) strategies. Strategies that have been tested in human clinical trials include adoptive transfer of lymphocytes and autologous tumor-pulsed DC as well as 2 AFP-based strategies: AFP-derived peptides in Montanide and AFP peptides pulsed onto autologous DC. These trials, testing novel immune-based interventions in HCC subjects, have resulted in immunologic responses and have impacted recurrence and survival in HCC subjects.