Growth-inhibitory effects of TGFαL3-SEB chimeric protein on colon cancer cell line

Targeting glioblastoma multiforme using a novel fusion protein comprising interleukin-13 and staphylococcal enterotoxin B in vitro

Targeting cell surface receptors with immunotoxins provides a novel, unique and highly potent treatment against cancers. A high expression of interleukin-13 (IL13) receptor α2 (IL13Rα2) has been reported in different types of cancers including glioblastoma multiforme (GBM). In this paper, to target IL13Rα2 on GBM cells, a fusion protein was generated comprising human IL13 and staphylococcal enterotoxin B (SEB), termed IL13-linker-SEB. The fusion protein was cloned into pET28a(+) and expressed in Escherichia coli strain BL21 (DE3); U251 (IL13Rα2-positive) and T98G (IL13Rα2-negative) GBM cell lines were employed and the functional activity of IL13-linker-SEB was evaluated by cell ELISA, cytotoxicity (MTT and LDH), apoptosis (flow cytometry and caspase-3 activity), adhesion, scratch and RT-PCR tests. SEB and chemotherapeutic drugs were employed to be compared to IL13-linker-SEB function. The IL13-linker-SEB exhibited higher binding affinity and cytotoxicity compared to SEB on U251 cells, although both recombinant proteins had shown similar behavior regarding T98G cells. Furthermore, the highest induction of apoptosis was observed in U251 cells treated with IL13-linker-SEB which was confirmed by Bax/Bcl-2 ratio. The expression of MMP2, MMP9 and VEGFR2 in U251 cells experienced a significant reduction after treatment with IL13-linker-SEB compared to SEB and T98G treated cells. The data showed that IL13-linker-SEB can be considered as a novel potential agent for GBM treatment; however, further research is needed to investigate the efficacy.

Novel SPEA Superantigen Peptide Agonists and Peptide Agonist-TGFαL3 Conjugate. In Vitro Study of Their Growth-Inhibitory Effects for Targeted Cancer Immunotherapy

Bacterial superantigens (SAgs) are effective T-cell stimulatory molecules that lead to massive cytokine production. Superantigens crosslink between MHC class II molecules on the Antigen Presenting Cells (APC) and TCR on T-cells. This enables them to activate up to 20% of resting T cells, whilst conventional antigen presentation results in the activation of 0.001-0.0001% of the T cell population. These biological properties of superantigens make them attractive for use in immunotherapy. Previous studies have established the effectiveness of superantigens as therapeutic agents. This, however, was achieved with severe side effects due to the high lethality of the native toxins. Our study aims to produce superantigen-based peptides with minimum or no lethality for safer cancer treatment. In previous work, we designed and synthesized twenty overlapping SPEA-based peptides and successfully mapped regions in SPEA superantigen, causing a vasodilatory response. We screened 20 overlapping SPEA-based peptides designed and synthesized to cover the whole SPEA molecule for T-cell activation and tumor-killing ability. In addition, we designed and synthesized tumor-targeted superantigen-based peptides by fusion of TGFαL3 either from the N' or C' terminal of selected SPEA-based peptides with an eight-amino acid flexible linker in between. Our study identified parts of SPEA capable of stimulating human T-cells and producing different cytokines. We also demonstrated that the SPEA-based peptide conjugate binds specifically to cancer cells and can kill this cancer. Peptides induce T-cell activation, and tumor killing might pave the way for safer tumor-targeted superantigens (TTS). We proposed the combination of our new superantigen-based peptide conjugates with other immunotherapy techniques for effective and safer cancer treatment.

ARA-linker-TGFαL3: a novel chimera protein to target breast cancer cells

Targeted cancer therapies based on overexpressed receptors and the fractions containing immunotoxins and bacterial metabolites are one of the well-known methods to overcome the chemotherapy resistance of cancer cells. In this paper, we designed ARA-linker-TGFαL3, using Arazyme, a Serratia proteamaculans metabolite, and a third loop segment of TGFα to target EGFR-expressing breast cancer cells. After cloning in pET28a (+), the expression of recombinant protein was optimized in Escherichia coli strain BL21 (DE3). MDA-MB-468 (EGFR positive) and MDA-MB-453 (EGFR negative) breast cancer cell lines were employed. Also, the chemotherapeutic drug, Taxotere (Docetaxel), was employed to compare cytotoxicity effects. Cell ELISA assessed the binding affinity of recombinant proteins to the receptor, and the cytotoxicity was detected by MTT and lactate dehydrogenase release assays. The interfacing with cancer cell adhesion was evaluated. Furthermore, the induction of apoptosis was examined utilizing flow cytometric analysis, and caspase-3 activity assay. Moreover, RT-PCR was conducted to study the expression of apoptosis (bax, bcl2, and casp3), angiogenesis (vegfr2), and metastasis (mmp2 and mmp9) genes. ARA-linker-TGFαL3 revealed a higher binding affinity, cytotoxicity, and early apoptosis induction in MDA-MB-468 cells compared to the effects of Arazyme while both recombinant proteins showed similar effects on MDA-MB-453. In addition, the Taxotere caused the highest cytotoxicity on cancer cells through induction of late apoptosis. Meanwhile, the expression of angiogenesis and metastasis genes was decreased in both cell lines after treatment with either ARA-linker-TGFαL3 or Arazyme. Our in vitro results indicated the therapeutic effect of ARA-linker-TGFαL3 on breast cancer cells.

Potent in vitro antitumor activity of B-subunit of Shiga toxin conjugated to the diphtheria toxin against breast cancer

Immunotoxins are protein-based drugs consist of a target-specific binding domain and a cytotoxic domain to eliminate target cells. Such compounds are potentially therapeutic to combat diseases such as cancer. Generally, the B-subunit of Shiga toxin (STXB) receptor, globotriaosylceramide (Gb3), is expressed in high amounts on a number of human tumors cancer cells. In this study, we evaluated a new antitumor candidate called DT389-STXB chimeric protein, which genetically fused the DT to B-subunit of Shiga-like toxin (STXB). First a chimeric protein, encoding DT389-STXB was synthesized. The optimized chimeric protein expressed in E.coli BL21 (DE3) and confirmed by anti-His Western blot analysis. T47D, SKBR3, 4T1 and MCF7 cell lines were treated separately with purified DT389-STXB recombinant protein and functional activity of DT389-STXB was analyzed by the cell enzyme-linked immunosorbentassay (ELISA), MTT, ICC, Western blot and apoptosis tests. The results indicated that the recombinant DT389-STXB fusion protein with a molecular weight of 53 kDa was successfully expressed in E.coli BL21 (DE3) and the anti-His western-blot was used to confirm the presence of the protein. The DT389-STXB fusion protein attached to T47D, SKBR3 and 4T1 cell lines with the proper affinity and induced dose-dependent cytotoxicity against GB3-expressing cancer cells in vitro. Our results showed that DT389-STXB fusion protein may be a promising candidate for antitumor therapy agent against breast cancer; however, further studies are required to explore its efficacy in vivo for therapeutic applications.

Insulin-like growth factor binding protein 3 chemosensitizes pancreatic ductal adenocarcinoma through its death receptor

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies. Gemcitabine and doxorubicin are commonly used as the chemotherapy agents, but most of PDAC tumors eventually acquired resistance to chemotherapy. Accumulating evidence indicates that Insulin-like growth factor binding protein 3 (IGFBP-3) plays a key role against tumor growth but its expression has commonly suppressed. The present study was designed to evaluate IGFBP-3 effects in chemotherapy sensitization of PDAC cells. Here, we report that the re-sensitization of chemoresistant PDAC cells was occurred by IGFBP-3 through recruitment of its death receptor (IGFBP-3R). Using gemcitabine, doxorubicin-resistant PDAC cell lines, we found that IGFBP-3 sensitized chemoresistant cells by activating apoptosis (as evaluated by Bax up-regulation, Bcl-2 down-regulation as well as Caspase-3 and Caspase 8 activation). IGFBP-3R was also found to have higher expression level in resistant AsPc-1 and MIA PaCa-2 cells in comparison to parental cells. IGFBP-3R was also highly expressed in PDAC tumor which exposed to chemotherapy in comparison to un-treated PDAC tumors. In addition, we confirmed our finding by using specific siRNA to knocking down of IGFBP-3R which prevents IGFBP-3 Chemosensitization. Taken together, the present study for the first time indicates the clinical relevance for combining IGFBP-3 with chemotherapy to reduce chemoresistance in PDAC.

Breast cancer targeted/ therapeutic with double and triple fusion Immunotoxins

Target-specific transport of therapeutic agents holds promise to increase the efficacy of cancer treatment by decreasing injury to normal tissues and post treatment problems. HER2 is a tumor cell surface marker that is expressed in 25-30 % of breast cancer patients. The significant role of HER2 in cancer development and its biological feature makes it a highly appealing goal for the therapeutic treatment of cancer targeted therapy using HER2 monoclonal antibody. This approach is currently used as a special treatment against breast cancer in some research. In the present study, HER2 monoclonal antibody (mAb), (Herceptin) fused to PE38 by recombinant DNA technology and a new recombinant IT was developed. The scFv(Herceptin)-PE-STXA and scFv(Herceptin)-PE fusions cloned in pET28a and recombinant protein expression was carried out and then the proteins were purified. MCF-7 and SKBR-3 cells were used as HER2-negative and HER2-positive breast cancer cells, respectively. The cytotoxicity of its evaluated using MTT assay. The cell ELISA was used to determine the binding ability of immunotoxins (ITs) to the cell receptor and internalization and apoptosis were also assessed. The results revealed that cell cytotoxicity occurred in SKBR-3 cells in a dose-dependent manner but not in MCF-7 cells. It is possible that this ITs can attach to HER2-positive breast cancer cells and then, internalize and eradicate cancer cells by apoptosis. Here, we concluded that the recombinant ITs have therapeutic potential against HER2-positive breast cancer.