A novel dual-epigenetic inhibitor enhances recombinant monoclonal antibody expression in CHO cells.

Epigenetic regulation plays a central role in the regulation of a number of cellular processes such as proliferation, differentiation, cell cycle, and apoptosis. In particular, small molecule epigenetic modulators are key elements that can effectively influence gene expression by precisely regulating the epigenetic state of cells. To identify useful small-molecule regulators that enhance the expression of recombinant proteins in Chinese hamster ovary (CHO) cells, we examined a novel dual-HDAC/LSD1 inhibitor I-4 as a supplement for recombinant CHO cells. Treatment with 2 µM I-4 was most effective in increasing monoclonal antibody production. Despite cell cycle arrest at the G1/G0 phase, which inhibits cell growth, the addition of the inhibitor at 2 µM to monoclonal antibody-expressing CHO cell cultures resulted in a 1.94-fold increase in the maximal monoclonal antibody titer and a 2.43-fold increase in specific monoclonal antibody production. In addition, I-4 significantly increased the messenger RNA levels of the monoclonal antibody and histone H3 acetylation and methylation levels. We also investigated the effect on HDAC-related isoforms and found that interference with the HDAC5 gene increased the monoclonal antibody titer by 1.64-fold. The results of this work provide an effective method of using epigenetic regulatory strategies to enhance the expression of recombinant proteins in CHO cells. KEY POINTS: • HDAC/LSD1 dual-target small molecule inhibitor can increase the expression level of recombinant monoclonal antibodies in CHO cells. • By affecting the acetylation and methylation levels of histones in CHO cells and downregulating HDAC5, the production of recombinant monoclonal antibodies increased. • It provides an effective pathway for applying epigenetic regulation strategies to enhance the expression of recombinant proteins.

Lung adenocarcinoma discovered during the follow-up of lung-dominant connective tissue disease: a case report and literature review.

Interstitial lung disease (ILD) can lead to lung cancer, which brings great challenges to differential diagnosis and comprehensive treatment. However, the clinical features of lung-dominant connective tissue disease (LD-CTD) related ILD combined with lung cancer has not been validated. We report the case of an 80-year-old woman with LD-CTD treated regularly with nintedanib who presented progressive dyspnoea and hypoxemia after recurrent viral infections. Her chest computed tomography (CT) showed aggravated interstitial fibrosis in both lower lungs with moderate right pleural effusion. Clinicians should be alert to lung cancer in patients who are experiencing poor responsiveness to treatment or acute progression of ILD. The available literatures about the differential diagnosis of clinical manifestations, imaging, treatment and prognosis of LD-CTD are reviewed and discussed in this study.

Construction of an expression vector mediated by the dual promoter for prokaryotic and mammalian cell expression system.

The aim of this study was to construct an expression vector mediated by the dual promoter that can simultaneously drive the recombinant protein production in eukaryotic and prokaryotic cells. The prokaryotic T7 promoter and ribosome binding site (RBS) was cloned downstream of CMV promoter in the eukaryotic expression vector pIRES-neo, and T7 termination sequence was inserted upstream of neomycin phosphotransferase gene to generate the dual promoter vector. The enhanced green fluorescent protein (eGFP) gene was used as reporter gene. Then, the resultant vector was transfected into Chinese hamster ovary (CHO) cells and transformed into Escherichia coli (E. coli) BL21, and the eGFP expression levels were analyzed by fluorescence microscopy, flow cytometry and Western blot, respectively. Fluorescence microscopy revealed that the eGFP was expressed in both CHO cells and E. coli BL21. Flow cytometry showed that the eGFP expression level had no significant difference between the dual promoter vector and control vector in transfected CHO cells. Western blot analysis indicated the eGFP expressed in transformed E. coli. In conclusion, a prokaryotic-eukaryotic double expression vector was successfully constructed, which has potential applications in rapid cloning and expression of recombinant proteins in both prokaryotic and eukaryotic expression systems.

Distance effect characteristic of the matrix attachment region increases recombinant protein expression in Chinese hamster ovary cells.

OBJECTIVES: Previously, we have found that the matrix attachment region (MAR) may confer a 'distance effect' on transgene expression. This work aims to systematically explore the increased transgene expression in transfected Chinese hamster ovary (CHO) cells due to the characteristics of MAR and its mechanism. RESULTS: Compared with the control vector, 500 and 1000 bp DNA distances between MAR and the cytomegalovirus promoter can increase transgene expression by 1.77- and 1.56-fold, respectively. Meanwhile, transgene expression was not affected when 2000 and 2500 bp spacer DNAs were inserted, but a declining trend was observed when a 1500 bp spacer DNA was inserted. The vector containing a 500 bp DNA distance significantly increased the expression of the enhanced green fluorescent protein, and this increase was not related to transgene copy numbers. CONCLUSIONS: A short DNA distance-containing MAR confers high transgene expression level in transfected CHO cells, but a distance threshold does not exist in the vector system.

Novel short synthetic matrix attachment region for enhancing transgenic expression in recombinant Chinese hamster ovary cells.

Matrix attachment regions (MARs) are DNA fragments with specific motifs that enhance transgenic expression; however, the characteristics and functions of these elements remain unclear. In this study, we designed and synthesized three short chimeric MARs, namely, SM4, SM5, and SM6, with different numbers and orders of motifs on the basis of the features and motifs of previously reported MARs, namely, SM1, SM2, and SM3, respectively. Expression vectors with six synthetic MARs flanking the down or upstream of the expression cassette for enhanced green fluorescence protein (EGFP) were constructed and introduced into Chinese hamster ovary (CHO) cells. Results indicated that the EGFP expression of the CHO cells with transfection bySM4, SM5, or SM6-containing vectors was higher than that of those containing SM1, SM2, or SM3 regardless of the MAR insertion position. The improving effect of SM5 was particularly pronounced. Transgenic expression was further enhanced with the increasing SM5 copy number. Bioinformatics analysis indicated that several arrangements of the DNA-binding motifs for CEBP, FAST, Hox, glutathione, and NMP4 may help increase transgenic expression levels and the average population of highly expressed cells. Our findings on novel synthetic MARs will help establish stable expression systems in mammalian cells.

Enhancing expression level and stability of transgene mediated by episomal vector via buffering DNA methyltransferase in transfected CHO cells.

Nonviral episomal vectors present attractive alternative vehicles for gene therapy applications. Previously, we have established a new type of nonviral episomal vector-mediated by the characteristic motifs of matrix attachment regions (MARs), which is driven by the cytomegalovirus (CMV) promoter. However, the CMV promoter is intrinsically susceptible to silencing, resulting in declined productivity during long-term culture. In this study, Chinese hamster ovary (CHO) cells and DNA methyltransferase-deficient (Dnmt3a-deficient) CHO cells were transfected with plasmid-mediated by MAR, or CHO cells were treated with the DNA methylation inhibitor 5-Aza-2'-deoxycytidine. Flow cytometry, plasmid rescue experiments, fluorescence in-situ hybridization (FISH), and bisulfite sequencing were performed to observe transgene expression, its state of existence, and the CpG methylation level of the CMV promoter. The results indicated that all DNA methylation inhibitor and methyltransferase deficient cells could increase transgene expression levels and stability in the presence or absence of selection pressure after a 60-generation culture. Plasmid rescue assay and FISH analysis showed that the vector still existed episomally after long-time culture. Moreover, a relatively lower CMV promoter methylation level was observed in Dnmt3a-deficient cell lines and CHO cells treated with 5-Aza-2'-deoxycytidine. In addition, Dnmt3a-deficient cells were superior to the DNA methylation inhibitor treatment regarding the transgene expression and long-term stability. Our study provides the first evidence that lower DNA methyltransferase can enhance expression level and stability of transgenes mediated by episomal vectors in transfected CHO cells.

Recent developments in Hericium erinaceus polysaccharides: extraction, purification, structural characteristics and biological activities.

Hericium erinaceus (H. erinaceus), an edible mushroom with medicinal value, has a long history of usage in China and other oriental countries. Polysaccharide is supposed to be one of the major bioactive compounds in H. erinaceus, which possesses immunomodulating, anti-cancer, antioxidant, gastroprotection and intestinal health promotion, neuroprotective, hepatoprotective, antihpyerglycemic and hypolipidemic activities. In this review, the current advancements on extraction, purification, structural characteristics and biological activities of polysaccharide from different sources (fruiting body, mycelium and culture broth) of H. erinaceus were summarized. Among these aspects, summaries of the structural characteristics focused on the purified polysaccharides. Meanwhile, comparisons on the structural characteristics among the purified polysaccharides obtained from above three sources were made. Moreover, their biological activities were introduced on the basis of in vivo and in vitro experiments, and some possible action mechanisms were listed. Furthermore, the structure-activity relationship of the polysaccharide was discussed. New perspectives for the future work of Hericium erinaceus polysaccharide were also proposed. HIGHLIGHTS Extraction, purification, structural characteristics and biological activities of Hericium erinaceus polysaccharide (HEP) were summarized. Structural characteristics of the purified polysaccharides from different sources (fruiting body, mycelium and culture broth) of Hericium erinaceus were summarized and compared. Structure-activity relationship of HEP was discussed, and new perspectives for the future work of this polysaccharide were proposed.

SV40 intron, a potent strong intron element that effectively increases transgene expression in transfected Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells have become the most widely utilized mammalian cell line for the production of recombinant proteins. However, the product yield and transgene instability need to be further increased and solved. In this study, we investigated the effect of five different introns on transgene expression in CHO cells. hCMV intron A, adenovirus tripartite leader sequence intron, SV40 intron, Chinese hamster EF-1alpha gene intron 1 and intervening sequence intron were cloned downstream of the eGFP expression cassette in a eukaryotic vector, which was then transfected into CHO cells. qRT-PCR and flow cytometry were used to explore eGFP expression levels. And gene copy number was also detected by qPCR, respectively. Furthermore, the erythropoietin (EPO) protein was used to test the selected more strong intron. The results showed that SV40 intron exhibited the highest transgene expression level among the five compared intron elements under transient and stable transfections. In addition, the SV40 intron element can increase the ratio of positive colonies and decrease the coefficient of variation in transgene expression level. Moreover, the transgene expression level was not related to the gene copy number in stable transfected CHO cells. Also, the SV40 intron induced higher level of EPO expression than IVS intron in transfected CHO cell. In conclusion, SV40 intron is a potent strong intron element that increases transgene expression, which can readily be used to more efficient transgenic protein production in CHO cells.

CRISPR/Cas9-mediated gene knockout for DNA methyltransferase Dnmt3a in CHO cells displays enhanced transgenic expression and long-term stability.

CHO cells are the preferred host for the production of complex pharmaceutical proteins in the biopharmaceutical industry, and genome engineering of CHO cells would benefit product yield and stability. Here, we demonstrated the efficacy of a Dnmt3a-deficient CHO cell line created by CRISPR/Cas9 genome editing technology through gene disruptions in Dnmt3a, which encode the proteins involved in DNA methyltransferases. The transgenes, which were driven by the 2 commonly used CMV and EF1α promoters, were evaluated for their expression level and stability. The methylation levels of CpG sites in the promoter regions and the global DNA were compared in the transfected cells. The Dnmt3a-deficent CHO cell line based on Dnmt3a KO displayed an enhanced long-term stability of transgene expression under the control of the CMV promoter in transfected cells in over 60 passages. Under the CMV promoter, the Dnmt3a-deficent cell line with a high transgene expression displayed a low methylation rate in the promoter region and global DNA. Under the EF1α promoter, the Dnmt3a-deficient and normal cell lines with low transgene expression exhibited high DNA methylation rates. These findings provide insight into cell line modification and design for improved recombinant protein production in CHO and other mammalian cells.

Identification of a potent MAR element from the human genome and assessment of its activity in stably transfected CHO cells.

Low-level and unstable transgene expression are common issues using the CHO cell expression system. Matrix attachment regions (MARs) enhance transgene expression levels, but additional research is needed to improve their function and to determine their mechanism of action. MAR-6 from CHO chromosomes actively mediates high and consistent gene expression. In this study, we compared the effects of two new MARs and MAR-6 on transgene expression in recombinant CHO cells and found one potent MAR element that can significantly increase transgene expression. Two MARs, including the human CSP-B MAR element and DHFR intron MAR element from CHO cells, were cloned and inserted downstream of the poly(A) site in a eukaryotic vector. The constructs were transfected into CHO cells, and the expression levels and stability of eGFP were detected by flow cytometry. The three MAR sequences can be ranked in terms of overall eGFP expression, in decreasing order, as follows: human CSP-B, DHFR intron MAR element and MAR-6. Additionally, as expected, the three MAR-containing vectors showed higher transfection efficiencies and transient transgene expression in comparison with those of the non-MAR-containing vector. Bioinformatics analysis indicated that the NFAT and VIBP elements within MAR sequences may contribute to the enhancement of eGFP expression. In conclusion, the human CSP-B MAR element can improve transgene expression and its effects may be related to the NFAT and VIBP elements.

Construction strategies for developing expression vectors for recombinant monoclonal antibody production in CHO cells.

Recent years have seen the use of recombinant proteins in the treatment of different diseases. Among them, monoclonal antibodies (mAbs) are currently the fastest growing class of bio-therapeutic recombinant proteins. Chinese hamster ovary (CHO) cells are the most commonly used host cells for production of these recombinant mAbs. Expression vectors determine the expression level and quality of recombinant mAbs. Currently, few construction strategies for recombinant mAbs expression vectors in CHO cells have been developed, including monocistronic vector, multiple-promoter expression vector, and tricistronic vector mediated by internal ribosome entry site (IRES) or Furin-2A element. Among them, Furin-2A-mediated vector is an effective approach due to advantages of high "self-cleavage" efficiency, and equal expression of light and heavy chains from a single open reading frame. Here, we have reviewed the progress in development of different strategies for constructing recombinant mAb expression vectors in CHO cells and its potential advantages and disadvantages.

[Effects of Different Promoters and MAR Combinations on Transgene Expression of Recombinant CHO Cells].

OBJECTIVE: To analyze the effects of different promoters and matrix attachment region (MAR) on the expression of transgene in Chinese hamster ovary (CHO) cells. METHODS: The expression vector was constructed by the combination of beta globin MAR (gMAR) with the human cytomegalovirus immediate-early promoter (CMV-IE) and simian virus 40 (SV40) promoter. These vectors were transfected into CHO cells,after 48 h,the transient expression of enhanced green fluorescent protein (eGFP) was observed; G418 was used to screen stably transformed cell lines,and the expression level of eGFP in CHO cells was analyzed by flow cytometry. The relative copy numbers of eGFP were analyzed by qPCR. RESULTS: Without gMAR expression vector,the expression of eGFP which was driven by CMV-IE promoter was stronger than that of SV40 promoter; gMAR could increase the expression level of eGFP driven by CMV-IE promoter,but did not show any enhancement in SV40 promoter. The expression level of eGFP which containing gMAR on both sides was stronger than that of gMAR on one side driven by CMV-IE promoter; After G418 screening,the expression level of eGFP containing gMAR driven by SV40 promoter wasunstable,the fluorescence gradually weakened,therefore,we only analyzed the expression vector stably expressing the eGFP gene driven by CMV-IE promoter by flow cytometry and qPCR. Compared with the expression vector without gMAR containing CMV-IE promoter,flow cytometry showed that the expression levels of eGFP on one and both sides with gMAR were increased by 9.85-fold and 12.94-fold,respectivley; The result of qPCR showed that the copy number of the eGFP gene without gMAR was set to 1,the copy number of the eGFP gene in the expression vector driven by CMV-IE with gMAR on one side and both sides were 3.68-fold and 9.25-fold,respectively. CONCLUSION: The activity of CMV-IE promoter is stronger than that of SV40 promoter. gMAR can enhance the expression levels of transgene,which may be related to the increase of gene copy number.

[Effect of Intron Orientation on the Expression of Transgene Imposed by MAR Expression Vector in Stably Recombinant CHO Cells].

OBJECTIVE: To determine the effect of intron orientation on the transgene expression level imposed by matrix attachment region (MAR) expression vector. METHODS: The MAR of ß-globin was amplified by PCR, and then cloned into MAR expression vectors. An intron sequence was digested with restriction enzyme, ligated to the MAR expression vector in reverse orientation, and then transfected into Chinese hamster ovary (CHO) cells. The transfected stable cells were screened by G418. The level of chloramphenicol acetyltransferase (CAT) gene expression was analyzed by ELISA method. RESULTS: The transgene expression levels of CHO cells with the two expression vectors with a positive intron or without MAR were higher than that of CHO cells with an expression vector with reverse intron (P < 0.05). MAR did not improve transgene expression with reverse intron presence. CONCLUSION: Different orientation of intron can affect transgene expression in recombinant CHO cells. The transgene expression level can be increased using positive intron and MAR.

The effect of recombinant lentiviral vector encoding miR-145 on human esophageal cancer cells.

miR-145, a newly identified microRNA molecule, is hypothesized to function as a tumor suppressor, but this activity has not been investigated in esophageal l carcinoma (EC). The aim of this study was to investigate the effect of miR-145 on the biological features of EC cells. miR-145 was obtained using PCR technology and cloned into the lentiviral vector, pLVX-IRES-ZsGreen1, to construct the resulting vector, pLVX-IZ-miR-145. The vector was packaged, the viral titer was tested, and ECA109 cells were infected with the optimal viral titer. Cells that were stably transfected with miR-145 were screened. Flow cytometry was used to analyze enhanced green fluorescence protein gene expression, and to measure cell apoptosis and cell cycle. miR-145 expression was detected by real-time fluorescent quantitative PCR. Furthermore, cell proliferation was assayed using CCK-8 assay. The pLVX-IZ-miR-145 vector was successfully constructed, and the viral titer achieved up to 5.0 × 10(8) TU/mL. The transfection efficiency was 90 %. Compared to the control group, the expression level of miR-145 in the transfected group was significantly higher (185-fold, P < 0.05). miR-145 overexpression significantly inhibited esophageal cancer cell proliferation (P < 0.05). Moreover, the number of cells at the G2/M stage, as well as the cell apoptotic rate, in the miR-145-transfected group was significantly increased (P < 0.05). Our study reveals that overexpression of miR-145 inhibits cell proliferation, increases apoptosis, and influences the cell cycle progression of EC cell.

Highly lipophilic 3-epi-betulinic acid derivatives as potent and selective TGR5 agonists with improved cellular efficacy.

AIM: TGR5 is a G protein-coupled receptor that is expressed in intestinal L-cells and stimulates glucagon-like peptide 1 (GLP-1) secretion. TGR5 may represent a novel target for the treatment of metabolic disorder. Here, we sought to design and synthesize a series of TGR5 agonists derived from the natural product betulinic acid. METHODS: A series of betulinic acid derivatives were designed and synthesized. A cAMP assay was established using a HEK293 cell line expressing human TGR5. Luciferase reporter assay was established using HEK293 cells transfected with plasmids encoding human FXR and luciferase reporter. A human intestinal L-cell line NCI-H716 was used to evaluate the effects of the betulinic acid derivatives on GLP-1 secretion in vitro. RESULTS: Biological data revealed that the 3-α-OH triterpenoids consistently show increased potency for TGR5 compared to their 3-ß-OH epimers. 3-OH esterification increased the lipophilicity and TGR5 activity of 3-α betulinic derivatives and enhanced the activity differences between 3-α and 3-ß derivatives. The 3-α-acyloxy betulinic acids also exhibited a significant dose-dependent GLP-1 secretion effect. CONCLUSION: This study demonstrates that highly lipophilic 3-epi-betulinic acid derivatives can be potent and selective TGR5 agonists with improved cellular efficacy, and our research here provides a new strategy for the design and development of potent TGR5 agonists.

Distance effect of matrix attachment regions on transgene expression in stably transfected Chinese hamster ovary cells.

The ß-globin matrix attachment regions (MARs) were inserted into the 5'-site of the eukaryotic expression vector cassette and DNA fragments 350 and 750 bp in length were inserted into the site to generate expression vectors with varying distances between the expression cassette and MAR. The vectors containing MARs increased chloramphenicol acetyltransferase (CAT) expression levels compared to the negative control vector lacking the MAR; the highest expression increase was 3.8-fold. A greater MAR-transgene distance (750 bp) correlated with a greater increase in transgene expression when compared to the control vector that lacked separation between the MAR and transgene. CAT gene copy numbers were higher in cells transformed with the vector possessing a smaller MAR-transgene distance (350 bp) than in cells belonging to the other three groups. However, MAR-induced transgene expression levels did not exhibit a direct relationship with gene copy number.

Edible plant oils modulate gut microbiota during their health-promoting effects: a review.

Edible plant oils are widely used in cooking, cosmetics, health supplement capsules, and other industries, due to their various health-promoting effects. There is increasing evidence that edible plant oils can modulate gut microbiota during their health-promoting effects in animal experiments and cohort or clinical studies. However, the information concerning the gut microbiota modulation of edible plant oils during their health-promoting effects is scattered. In this article, the research progress on gut microbiota modulation of edible plant oils (especially camellia oil, olive oil, and flaxseed oil) is summarized. Meanwhile, a summary on correlations between modulated gut microbiota and changed biochemical indexes is provided. The alterations of edible plant oils on gut microbiota-derived metabolites and the correlations between altered metabolites and modulated gut microbiota as well as changed biochemical indexes are reviewed. Furthermore, the prospects for gut microbiota modulation of edible plant oils during their health-promoting effects are put forward. Existing literature has shown that edible plant oils could modulate gut microbiota during their health-promoting effects, and some differential gut microbiota biomarkers were gained. Some similarities and differences existed while the oils exhibited health-promoting actions. Dosage and treatment time have influences on gut microbiota modulation of edible plant oils. Different edible plant oils exhibited different behaviors in modulating gut microbiota, and edible plant oils were mostly different in modulating gut microbiota compared to edible animal oils. Moreover, the modulated gut microbiota was significantly correlated with the changed biochemical indexes. Furthermore, edible plant oils altered SCFAs and other gut microbiota-derived metabolites. The altered metabolites were obviously correlated with the modulated gut microbiota and changed biochemical indexes. This review is helpful to the future research and application of edible plant oils in health-promoting effects from the perspective of gut microbiota.

A review on structure, bioactivity, mechanism, structure-activity relationship and application of anti-breast cancer polysaccharides.

Breast cancer (BC) is one of the most common female malignant tumors. BC treatment depends on the use of chemotherapeutic drugs, causing various adverse effects. Increasing evidence has shown that natural polysaccharides (NPs) are potential adjuvants or substitutes for anti-BC drugs. However, the information regarding anti-BC NPs remains scattered. Thus, the recent progress in the structure, bioactivity, mechanism and application of anti-BC NPs is comprehensively summarized in this review. Moreover, the structure-activity relationship is discussed. Additionally, the prospects for future work are proposed. Recent studies have shown that anti-BC NPs have diverse structural features, which are affected by the extraction and purification methods. NPs show anti-BC activities in cell and animal experiments as well as in clinical researches, and enhance anti-BC effects of chemotherapeutic drugs in cell and animal experiments. The anti-BC mechanisms of NPs include anti-proliferation, inducing apoptosis, anti-metastasis and anti-invasion, immunoenhancement, gut microbiota regulation and others. The anti-BC activities of NPs are influenced by molecular weight, monosaccharide composition, functional groups, glycosidic bond types, backbone and side chains. NPs-based nanoparticles, nanocarriers, drug delivery systems, nanocomposites and other materials can also be used in anti-BC. This review provides theoretical bases for future research and functional application of NPs in anti-BC.

Analysis of risk factors associated with pre-myopia among primary school students in the Mianyang Science City.

Objectives To find out the prevalence rate of pre-myopia among primary school students in the Mianyang Science City Area, analyze its related risk factors, and thus provide a reference for local authorities to formulate policies on the prevention and control of myopia for primary school students. Methods From September to October 2021, Cluster sampling was adopted by our research group to obtain the vision levels of primary school students employing a diopter test in the Science City Area. In addition, questionnaires were distributed to help us find the risk factors associated with pre-myopia. Through the statistical analysis, we identify the main risk factors for pre-myopia and propose appropriate interventions. Results The prevalence rate of pre-myopia among primary school students in the Science City Area was 45.27% (1020/2253), of which 43.82% were boys and 46.92% were girls, with no statistically significant difference in the prevalence rate of myopia between boys and girls (2 =2.171, P=0.141). The results of the linear trend test showed that the prevalence rate of pre-myopia tends to decrease with increasing age (Z=296.521, P=0.000). Logistic regression analysis demonstrated that the main risk factors for pre-myopia were having at least one parent with myopia, spending less than 2 hours a day outdoors, using the eyes continuously for more than 1 hour, looking at electronic screens for more than 2 hours, and having an improper reading and writing posture. Conclusion The Science City Area has a high prevalence rate of pre-myopia among primary school students. It is proposed that students, schools, families, and local authorities work together to increase the time spent outdoors, reduce digital screens and develop scientific use of eye habits.

Synthetic enhancers including TFREs improve transgene expression in CHO cells.

The human cytomegalovirus major immediate early gene (CMV) promoter is currently the most preferred promoter for recombinant therapeutic proteins (RTPs) production in CHO cells. To enhance the production of RTPs, five synthetic enhancers including multiple transcription factor regulatory elements (TFREs) were evaluated to enhance recombinant protein level in transient and stably transfected CHO cells. Compared with the control, four elements can enhance the report genes expression under both two transfected states. Further, the function of these four enhancers on human serum albumin (HSA) were investigated. We found that the transient expression can increase by up to 1.5 times, and the stably expression can maximum increase by up to 2.14 times. The enhancement of transgene expression was caused by the boost of their corresponding mRNA levels. Transcriptomics analysis was performed and found that transcriptional activation and cell cycle regulation genes were involved. In conclusion, optimization of enhancers in the CMV promoter could increase the production yield of transgene in transfected CHO cells, which has significance for developing high-yield CHO cell expression system.