Two-color fluorescent proteins reporting survivin regulation in breast cancer cells for high throughput drug screening

Development of 3D Cell-Based Fluorescent Reporter Assay for Screening of Drugs Downregulating Telomerase Reverse Transcriptase

A fluorescent cell-based assay was developed for the screening of chemicals repressing the expression of human telomerase reverse transcriptase (hTERT). hTERT is reactivated during carcinogenesis and is overexpressed in more than 90% of cancers but is almost silent in normal tissue cells. Because of its critical role in cancer, hTERT is a target in various therapeutic strategies for cancer treatment. In this study, the hTERT promoter was cloned in MCF7 breast cancer cells and used to control the expression of enhanced green fluorescent protein (EGFP). The fluorescence of EGFP indicated the activity of the hTERT promoter, and, in the presence of an hTERT repressor, the EGFP fluorescence signal was reduced as compared to the EGFP fluorescence controlled by the human cytomegalovirus (CMV) promoter, which was not affected by changes in culture conditions and worked as a control. The EGFP reporter cells were cultivated in three-dimensional (3D) microbioreactors to resemble the in vivo tumor physiology and provide in vivo-like responses. The assay's predictability was demonstrated with three known hTERT inhibitors, pristimerin, epigallocatechin gallate, and n-butylidenephthalide, and further evaluated with five widely used anticancer compounds, doxorubicin, cisplatin, paclitaxel, blasticidin, and tamoxifen. The results showed overall accuracy of over 83.3%, demonstrating the feasibility of using the hTERT promoter with EGFP as a reporter for the screening of potential cancer drugs targeting hTERT.

Engineering the reductive tricarboxylic acid pathway in Aureobasidium pullulans for enhanced biosynthesis of poly-L-malic acid

Aureobasidium pullulans produced poly-L-malic acid (PMA) as the main metabolite in fermentation but with relatively low productivity and yield limiting its industrial application. In this study, A. pullulans ZX-10 was engineered to overexpress cytosolic malate dehydrogenase (MDH) and pyruvate carboxylase (PYC) and PMA synthetase (PMS) using a high-copy yeast episomal plasmid with the gpdA promoter from Aspergillus nidulans. Overexpressing endogenous PMS and heterologous MDH and PYC from Aspergillus oryzae respectively increased PMA production by 19 % - 37 % (0.64 - 0.74 g/g vs. 0.54 g/g for wild type) in shake-flask fermentations, demonstrating the importance of the reductive tricarboxylic acid (rTCA) pathway in PMA biosynthesis. A. pullulans co-expressing MDH and PYC produced 96.7 g/L PMA at 0.90 g/L∙h and 0.68 g/g glucose in fed-batch fermentation, which were among the highest yield and productivity reported. The engineered A. pullulans with enhanced rTCA pathway is advantageous and promising for PMA production.

Erythrocyte-cancer hybrid membrane-coated reduction-sensitive nanoparticles for enhancing chemotherapy efficacy in breast cancer

Cell-membrane-coated biomimetic nanoparticles (NPs) have attracted great attention due to their prolonged circulation time, immune escape mechanisms and homotypic targeting properties. Biomimetic nanosystems from different types of cell -membranes (CMs) can perform increasingly complex tasks in dynamic biological environments thanks to specific proteins and other properties inherited from the source cells. Herein, we coated doxorubicin (DOX)-loaded reduction-sensitive chitosan (CS) NPs with 4T1 cancer cell -membranes (CCMs), red blood cell -membranes (RBCMs) and hybrid erythrocyte-cancer membranes (RBC-4T1CMs) to enhance the delivery of DOX to breast cancer cells. The physicochemical properties (size, zeta potential and morphology) of the resulting RBC@DOX/CS-NPs, 4T1@DOX/CS-NPs and RBC-4T1@DOX/CS-NPs, as well as their cytotoxic effect and cellular NP uptake in vitro were thoroughly characterized. The anti-cancer therapeutic efficacy of the NPs was evaluated using the orthotopic 4T1 breast cancer model in vivo. The experimental results showed that DOX/CS-NPs had a DOX-loading capacity of 71.76 ± 0.87 %, and that coating of DOX/CS-NPs with 4T1CM significantly increased the NP uptake and cytotoxic effect in breast cancer cells. Interestingly, by optimizing the ratio of RBCMs:4T1CMs, it was possible to increase the homotypic targeting properties towards breast cancer cells. Moreover, in vivo tumor studies showed that compared to control DOX/CS-NPs and free DOX, both 4T1@DOX/CS-NPs and RBC@DOX/CS-NPs significantly inhibited tumor growth and metastasis. However, the effect of 4T1@DOX/CS-NPs was more prominent. Moreover, CM-coating reduced the uptake of NPs by macrophages and led to rapid clearance from the liver and lungs in vivo, compared to control NPs. Our results suggest that specific self-recognition to source cells resulting in homotypic targeting increased the uptake and the cytotoxic capacity of 4T1@DOX/CS-NPs by breast cancer cells in vitro and in vivo. In conclusion, tumor-disguised CM-coated DOX/CS-NPs exhibited tumor homotypic targeting and anti-cancer properties, and were superior over targeting with RBC-CM or RBC-4T1 hybrid membranes, suggesting that the presence of 4T1-CM is critical for treatment outcome.