Optimization of Epigenetic Modifier Drug Combination for Synergistic Effect against Glioblastoma Multiform Cancer Cell Lines.

Glioblastoma multiforme (GBM), is a frequent class of malignant brain tumors. Epigenetic therapy, especially with synergistic combinations is highly paid attention for aggressive solid tumors like GBM. Here, RSM optimization has been used to increase the efficient arrest of U87 and U251 cell lines due to synergistic effects. Cell lines were treated with SAHA, 5-Azacytidine, GSK-126, and PTC-209 individually and then RSM was used to find most effective combinations. Results showed that optimized combinations significantly reduce cell survival and induce cell cycle arrest and apoptosis in both cell lines. Expression of cyclin B1 and cyclin D1 were decreased while caspase3 increased expression.

Efficient refolding of recombinant reteplase expressed in Escherichia coli strains using response surface methodology.

Reteplase is a deleted variant of human tissue plasminogen activator with a complex structure containing nine disulfide bonds. Reteplase is expressed as inclusion bodies in Escherichia coli and needs the additional step of refolding for activation. In this study an experimental design was performed to find the optimal refolding condition for reteplase. The influence of 14 chemical additives was assessed by one factor at a time method and then Taguchi design followed by response surface methodology was employed to find compounds with most significant effects on reteplase refolding and their optimum concentration. We found that 0.13 M histidine, 1.64 M methionine, 0.33 M cysteine, and 0.34 M arginine in addition to the GSH/GSSG is the optimal condition for refolding of reteplase. We also investigated the refolding yield for inclusion bodies obtained from different E. coli strains and found that BL21 (DE3) has the best recovery yield in comparison to Rosetta-gami and Shuffle T7.

Auto-induction for high level production of biologically active reteplase in Escherichia coli.

Reteplase is a third generation tissue plasminogen activator (tPA) with a modified structure and prolonged half-life in comparison to native tPA. As a non-glycosylated protein, reteplase is expressed in Escherichia coli. Due to presence of several disulfide bonds, high level production of reteplase is complicated and needs extra steps for conversion to biologically active form. Auto-induction represents a method for high-yield growth of bacterial cells and higher expression of recombinant proteins. Here we have tried to optimize the auto-induction procedure for soluble and active expression of reteplase in E. coli. Results showed that using auto-induction strategy at 37 °C, Rosetta-gami (DE3) had the highest level of active and soluble reteplase production in comparison to E. coli strains BL21 (DE3), and Shuffel T7. Temperature dominantly affected the level of active reteplase production. Decreasing the temperature to 25 and 18 °C increased the level of active reteplase by 20 and 60%, respectively. The composition of auto-induction medium also dramatically changed the active production of reteplase in cytoplasm. Using higher enriched auto-induction medium, super broth base including trace elements, significantly increased biologically active reteplase by 30%. It is demonstrated here that auto-induction is a powerful method for expression of biologically active reteplase in oxidative cytoplasm of Rosetta-gami. Optimizing expression condition by decreasing temperature and using an enriched auto-induction medium resulted in at least three times higher level of active reteplase production. Production of correctly folded and active reteplase in spite of its complex structure helps for removal of inefficient and cumbersome step of refolding.