High-level expression, purification and pro-apoptosis activity of HIV-TAT-survivin (T34A) mutant to cancer cells in vitro

Discovering and Characterizing of Survivin Dominant Negative Mutants With Stronger Pro-apoptotic Activity on Cancer Cells and CSCs

Survivin as a member of the inhibitor of apoptosis proteins (IAPs) family is undetectable in normal cells, but highly expressed in cancer cells and cancer stem cells (CSCs) which makes it an attractive target in cancer therapy. Survivin dominant negative mutants have been reported as competitive inhibitors of endogenous survivin protein in cancer cells. However, there is a lack of systematic comparative studies on which mutants have stronger effect on promoting apoptosis in cancer cells, which will hinder the development of novel anti-cancer drugs. Here, based on the previous study of survivin and its analysis of the relationship between structure and function, we designed and constructed a series of different amino acid mutants from survivin (TmSm34, TmSm48, TmSm84, TmSm34/48, TmSm34/84, and TmSm34/48/84) fused cell-permeable peptide TATm at the N-terminus, and a dominant negative mutant TmSm34/84 with stronger pro-apoptotic activity was selected and evaluated systematically in vitro. The double-site mutant of survivin (TmSm34/84) showed more robust pro-apoptotic activity against A549 cells than others, and could reverse the resistance of A549 CSCs to adriamycin (ADM) (reversal index up to 7.01) by decreasing the expression levels of survivin, P-gp, and Bcl-2 while increasing cleaved caspase-3 in CSCs. This study indicated the selected survivin dominant negative mutant TmSm34/84 is promising to be an excellent candidate for recombinant anti-cancer protein by promoting apoptosis of cancer cells and their stem cells and sensitizing chemotherapeutic drugs.

High-level SUMO-mediated fusion expression of ABP-dHC-cecropin A from multiple joined genes in Escherichia coli

The antimicrobial peptide ABP-dHC-cecropin A is a small cationic peptide with potent activity against a wide range of bacterial species. Evidence of antifungal activity has also been suggested; however, evaluation of this peptide has been limited due to the low expression of cecropin proteins in Escherichia coli. To improve the expression level of ABP-dHC-cecropin A in E. coli, tandem repeats of the ABP-dHC-cecropin A gene were constructed and expressed as fusion proteins (SUMO-nABP-dHC-cecropin, n = 1, 2, 3, 4) via pSUMO-nABP-dHC-cecropin A vectors (n = 1, 2, 3, 4). Comparison of the expression levels of soluble SUMO-nABP-dHC-cecropin A fusion proteins (n = 1, 2, 3, 4) suggested that BL21 (DE3)/pSUMO-3ABP-dHC-cecropin A is an ideal recombinant strain for ABP-dHC-cecropin A production. Under the selected conditions of cultivation and isopropylthiogalactoside (IPTG) induction, the expression level of ABP-dHC-cecropin A was as high as 65 mg/L, with ∼21.3% of the fusion protein in soluble form. By large-scale fermentation, protein production reached nearly 300 mg/L, which is the highest yield of ABP-dHC-cecropin A reported to date. In antibacterial experiments, the efficacy was approximately the same as that of synthetic ABP-dHC-cecropin A. This method provides a novel and effective means of producing large amounts of ABP-dHC-cecropin A.

In vitro production and antifungal activity of peptide ABP-dHC-cecropin A

The antimicrobial peptide ABP-dHC-cecropin A is a small cationic peptide with potent activity against a wide range of bacterial species. Evidence of antifungal activity has also been suggested; however, testing of this peptide has been limited due to the low expression of cecropin proteins in Escherichia coli. To improve expression of this peptide in E. coli, ABP-dHC-cecropin A was cloned into a pSUMO vector and transformed into E. coli, resulting in the production of a pSUMO-ABP-dHC-cecropin A fusion protein. The soluble form of this protein was then purified by Ni-IDA chromatography, yielding a total of 496-mg protein per liter of fermentation culture. The SUMO-ABP-dHC-cecropin A fusion protein was then cleaved using a SUMO protease and re-purified by Ni-IDA chromatography, yielding a total of 158-mg recombinant ABP-dHC-cecropin A per liter of fermentation culture at a purity of ≥94%, the highest yield reported to date. Antifungal activity assays performed using this purified recombinant peptide revealed strong antifungal activity against both Candida albicans and Neurospora crassa, as well as Rhizopus, Fusarium, Alternaria, and Mucor species. Combined with previous analyses demonstrating strong antibacterial activity against a number of important bacterial pathogens, these results confirm the use of ABP-dHC-cecropin A as a broad-spectrum antimicrobial peptide, with significant therapeutic potential.

Multisite mutation of monomer survivin with enhanced effect on apoptosis regulation of breast cancer cells

Survivin is an important protein in regulating both cell apoptosis and proliferation. It has attracted growing attentions in recent years as a promising target for cancer therapy. Previous studies have revealed that monomeric survivin regulated apoptosis in a more significant way than the wild-type survivin that generally contains a large portion of its dimers. In order to investigate the roles of monomeric mutant survivin apoptosis and cell cycle regulation of human cancer cells, we developed and tested three dominant-negative mutants with multisite mutations (MSM) including TAT-survivin(34/101/102), TAT-survivin(34/117/101/102) and TAT-survivin(117/101/102). Results revealed that MSM mutants remained as monomers under ambient conditions, and induced cells (breast cancer Bcap-37 cells) apoptosis even more efficiently, primarily through the caspase-dependent and Bcl-2-related pathways, than non-monomeric mutants. We further identified that the TAT-survivin(34/101/102) and TAT-survivin(117/101/102) MSM significantly inhibited the proliferation of Bcap-37 cells and arrested cells in S and G2/M phases, while TAT-survivin(34/117/101/102) arrested cells in G2/M phase. It appeared to us that TAT-survivin(34/101/102) and TAT-survivin(117/101/102) also inhibited cell proliferation more significantly. These findings suggest that such MSM afford monomeric survivin with promising potentials for cancer therapy.

Controlled delivery of BID protein fused with TAT peptide sensitizes cancer cells to apoptosis

BACKGROUND

Low cellular level of BID is critical for viability of numerous cancer cells. Sensitization of cells to anticancer agents by BID overexpression from adenovirus or pcDNA vectors is a proposed strategy for cancer therapy; however it does not provide any stringent control of cellular level of BID. The aim of this work was to examine whether a fusion of BID with TAT cell penetrating peptide (TAT-BID) may be used for controlled sensitization of cancer cells to anticancer agents acting through death receptors (TRAIL) or DNA damage (camptothecin). Prostate cancer PC3 and LNCaP, non-small human lung cancer A549, and cervix carcinoma HeLa cells were used in the study.

METHODS

Uptake of TAT-BID protein by cells was studied by quantitative Western blot analysis of cells extracts. Cells viability was monitored by MTT test. Apoptosis was detected by flow cytometry and cytochrome c release assay.

RESULTS

TAT-BID was delivered to all cancer cells in amounts depending on time, dose and the cell line. Recombinant BID sensitized PC3 cells to TRAIL or, to lesser extent, to camptothecin. Out of remaining cells, TAT-BID sensitized A549, and only slightly HeLa cells to TRAIL. None of the latter cell lines were sensitized to camptothecin. In all cases the mutant not phosphorylable by CK2 (TAT-BIDT59AS76A) was similarly efficient in sensitization as the wild type TAT-BID.

CONCLUSIONS

TAT-BID may be delivered to cancer cells in controlled manner and efficiently sensitizes PC3 and A549 cells to TRAIL. Therefore, it may be considered as a potential therapeutic agent that enhances the efficacy of TRAIL for the treatment of prostate and non-small human lung cancer.

Genetic protein TmSm(T34A) enhances sensitivity of chemotherapy to breast cancer cell lines as a synergistic drug to doxorubicin

In order to eliminate common side effects to cancer patients and resistance from chemotherapy, a genetic protein TmSm(T34A) was investigated as a sensitizer to doxorubicin. The results indicated TmSm(T34A) enhanced the sensitivity of three breast cancer cell lines to doxorubicin with low dose, and reduced the dose of doxorubicin significantly in contrast to common effective dose. As a synergistic therapy, the TmSm(T34A) also caused strongest apoptotic activity in MCF-7, and the possible molecular mechanisms were explored primarily. The research showed the TmSm(T34A) is promising to be a potential drug in strengthening therapy effects of breast cancer chemotherapy.

Production of bioactive human hemangiopoietin in Escherichia coli

To devise an efficient approach for production of human hemangiopoietin (hHAPO), the gene of hHAPO was synthesized and subcloned into the pSUMO vector with a SUMO tag at the N-terminus. The expression construct was then transformed into the expression strain E. coli BL21(DE3). The fusion protein was expressed in soluble form and identified by SDS-PAGE and Western blotting. The fusion protein was purified to 90% purity by metal chelate chromatography with a yield of 45 mg per liter fermentation culture. The SUMO tag was removed by cleavage with SUMO protease at room temperature for 1 h, and the hHAPO was then re-purified by the metal chelate chromatography. Finally, about 21 mg hHAPO was obtained from 1 liter of fermentation culture with no less than 95% purity. The recombinant hHAPO significantly stimulated the proliferation of human umbilical vein endothelial cells.

Expression and functional characterization of tumor-targeted fusion protein composed of NGR peptide and 15-kDa actin fragment

To induce tumor cell apoptosis, a modified 15 kDa actin linked with a peptide NGR "homing" into tumor or tumor vessels was expressed in Escherichia coli. After refolding and purification, this fusion protein NGR-15actin was labeled with FITC to testify whether NGR-15actin could integrate into the cytoskeleton. It was found that this targeted peptide could induce HepG2 and HeLa cells apoptosis through its effect on the cytoskeleton function by binding to cytoskeleton protein. Thus, targeted NGR-15actin could be a candidate molecule for the therapy of cancer.

Production of a cytotoxic cationic antibacterial peptide in Escherichia coli using SUMO fusion partner

Antibacterial peptide CM4 (ABP-CM4) is a small cationic peptide with broad-spectrum activities against bacteria, fungi, and tumor cells, which may possibly be used as an antimicrobial agent. We report here the application of small ubiquitin-related modifier (SUMO) fusion technology to the expression and purification of cationic antibacterial peptide ABP-CM4. The fusion protein expressed in a soluble form was purified to a purity of 90% by Ni-IDA chromatography and 112 mg protein of interest was obtained per liter of fermentation culture. After the SUMO-CM4 fusion protein was cleaved by the SUMO protease at 30 degrees C for 1 h, the cleaved sample was re-applied to a Ni-IDA. Finally, about 24 mg recombinant CM4 was obtained from 1 l fermentation culture with no less than 96% purity and the recombinant CM4 had similar antimicrobial properties to the synthetic CM4. Thus, the SUMO-mediated peptide expression and purification system potentially could be employed for the production of recombinant cytotoxic peptides.

The anti-apoptotic gene survivin contributes to teratoma formation by human embryonic stem cells

Teratomas derived from human embryonic stem (hES) cells are unique among oncogenic phenomena as they are polyclonal and develop from apparently normal cells. A deeper understanding of this process should aid in the development of safer cell therapies and may help elucidate the basic principles of tumor initiation. We find that transplantation of diploid hES cells from four independent cell lines generates benign teratomas with no sign of malignancy or persisting embryonal carcinoma-like cells. In contrast, mouse embryonic stem (mES) cells from four cell lines consistently generate malignant teratocarcinomas. Global gene expression analysis shows that survivin (BIRC5), an anti-apoptotic oncofetal gene, is highly expressed in hES cells and teratomas but not in embryoid bodies. Genetic and pharmacological ablation of survivin induces apoptosis in hES cells and in teratomas both in vitro and in vivo. We suggest that continued expression of survivin upon differentiation in vivo may contribute to teratoma formation by hES cells.