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Background Mammography is widely used for breast cancer screening but suffers from a high false-positive rate. Here, we perform the largest comprehensive, multi-center study to date involving diverse ethnic groups, for the identification of circulating miRNAs for breast cancer screening. Methods This study had a discovery phase (n = 289) and two validation phases (n = 374 and n = 379). Quantitative PCR profiling of 324 miRNAs was performed on serum samples from breast cancer (all stages) and healthy subjects to identify miRNA biomarkers. Two-fold cross-validation was used for building and optimising breast cancer-associated miRNA panels. An optimal panel was validated in cohorts with Caucasian and Asian samples. Diagnostic ability was evaluated using area under the curve (AUC) analysis. Results The study identified and validated 30 miRNAs dysregulated in breast cancer. An optimised eight-miRNA panel showed consistent performance in all cohorts and was successfully validated with AUC, accuracy, sensitivity, and specificity of 0.915, 82.3%, 72.2% and 91.5%, respectively. The prediction model detected breast cancer in both Caucasian and Asian populations with AUCs ranging from 0.880 to 0.973, including pre-malignant lesions (stage 0; AUC of 0.831) and early-stage (stages I–II) cancers (AUC of 0.916). Conclusions Our panel can potentially be used for breast cancer screening, in conjunction with mammography.

ObjectiveAn unmet need exists for a non-invasive biomarker assay to aid gastric cancer diagnosis. We aimed to develop a serum microRNA (miRNA) panel for identifying patients with all stages of gastric cancer from a high-risk population.DesignWe conducted a three-phase, multicentre study comprising 5248 subjects from Singapore and Korea. Biomarker discovery and verification phases were done through comprehensive serum miRNA profiling and multivariant analysis of 578 miRNA candidates in retrospective cohorts of 682 subjects. A clinical assay was developed and validated in a prospective cohort of 4566 symptomatic subjects who underwent endoscopy. Assay performance was confirmed with histological diagnosis and compared with Helicobacter pylori (HP) serology, serum pepsinogens (PGs), ‘ABC’ method, carcinoembryonic antigen (CEA) and cancer antigen 19–9 (CA19-9). Cost-effectiveness was analysed using a Markov decision model.ResultsWe developed a clinical assay for detection of gastric cancer based on a 12-miRNA biomarker panel. The 12-miRNA panel had area under the curve (AUC)=0.93 (95% CI 0.90 to 0.95) and AUC=0.92 (95% CI 0.88 to 0.96) in the discovery and verification cohorts, respectively. In the prospective study, overall sensitivity was 87.0% (95% CI 79.4% to 92.5%) at specificity of 68.4% (95% CI 67.0% to 69.8%). AUC was 0.848 (95% CI 0.81 to 0.88), higher than HP serology (0.635), PG 1/2 ratio (0.641), PG index (0.576), ABC method (0.647), CEA (0.576) and CA19-9 (0.595). The number needed to screen is 489 annually. It is cost-effective for mass screening relative to current practice (incremental cost-effectiveness ratio=US$44 531/quality-of-life year).ConclusionWe developed and validated a serum 12-miRNA biomarker assay, which may be a cost-effective risk assessment for gastric cancer.Trial registration numberThis study is registered with ClinicalTrials.gov (Registration number: NCT04329299).

Minimally invasive testing for early detection of lung cancer to improve patient survival is a major unmet clinical need. This study aimed to develop and validate a serum multi-microRNA (multimiR) panel as a minimally invasive test for early detection of nonsmall cell lung cancer (NSCLC) regardless of smoking status, gender, and ethnicity. Our study included 744 NSCLC cases and 944 matched controls, including smokers and nonsmokers, male and female, with Asian and Caucasian subjects. Using RT-qPCR and a tightly controlled workflow, we quantified the absolute expression of 520 circulating microRNAs (miRNAs) in a Chinese cohort of 180 early stage NSCLC cases and 216 healthy controls (male smokers). Candidate biomarkers were verified in two case-control cohorts of 432 Chinese and 218 Caucasians, respectively (including females and nonsmokers). A multimiR panel for NSCLC detection was developed using a twofold cross-validation and validated in three additional Asian cohorts comprising 642 subjects. We discovered 35 candidate miRNA biomarkers, verified 22 of them, and developed a five-miR panel that detected NSCLC with area under curve (AUC) of 0.936-0.984 in the discovery and verification cohorts. The panel was validated in three independent cohorts with AUCs of 0.973, 0.916, and 0.917. The sensitivity of five-miR test was 81.3% for all stages, 82.9% for stages I and II, and 83.0% for stage I NSCLC, when the specificity is at 90.7%. We developed a minimally invasive five-miR serum test for detecting early stage NSCLC and validated its performance in multiple patient cohorts independent of smoking status, gender, and ethnicity.

Objectives To evaluate cost-effectiveness of a novel screening strategy using a microRNA (miRNA) blood test as a screen, followed by endoscopy for diagnosis confirmation in a 3-yearly population screening program for gastric cancer. Methods A Markov cohort model has been developed in Microsoft Excel 2016 for the population identified to be at intermediate risk (Singaporean men, aged 50-75 years with Chinese ethnicity). The interventions compared were (1) initial screening using miRNA test followed by endoscopy for test-positive individuals and a 3-yearly follow-up screening for test-negative individuals (proposed strategy), and (2) no screening with gastric cancer being diagnosed clinically (current practice). The model was evaluated for 25 years with a healthcare perspective and accounted for test characteristics, compliance, disease progression, cancer recurrence, costs, utilities, and mortality. The outcomes measured included incremental cost-effectiveness ratios, cancer stage at diagnosis, and thresholds for significant variables. Results The miRNA-based screening was found to be cost-effective with an incremental cost-effectiveness ratio of $40 971/quality-adjusted life-year. Key drivers included test costs, test accuracy, cancer incidence, and recurrence risk. Threshold analysis highlights the need for high accuracy of miRNA tests (threshold sensitivity: 68%; threshold specificity: 77%). A perfect compliance to screening would double the cancer diagnosis in early stages compared to the current practice. Probabilistic sensitivity analysis reported the miRNA-based screening to be cost-effective in >95% of iterations for a willingness to pay of $70 000/quality-adjusted life-year (approximately equivalent to 1 gross domestic product/capita) Conclusions The miRNA-based screening intervention was found to be cost-effective and is expected to contribute immensely in early diagnosis of cancer by improving screening compliance.

Astaxanthin is a natural pigment, known for its strong antioxidant activity and numerous health benefits to human and animals. Its antioxidant activity is known to be substantially greater than β-carotene and about a thousand times more effective than vitamin E. The potential health benefits have generated a growing commercial interest, and the escalating demand has prompted the exploration of alternative supply chain. Astaxanthin naturally occurs in many sea creatures such as trout, shrimp, and microalgae, some fungi, bacteria, and flowering plants, acting to protect hosts against environmental stress and adverse conditions. Due to the rapid growth and simple growth medium requirement, microbes, such as the microalga, Haematococcus pluvialis, and the fungus Xanthophyllomyces dendrorhous, have been developed to produce astaxanthin. With advances in metabolic engineering, non-carotenogenic microbes, such as Escherichia coli and Saccharomyces cerevisiae, have been purposed to produce astaxanthin and significant progress has been achieved. Here, we review the recent achievements in microbial astaxanthin biosynthesis (with reference to metabolic engineering strategies) and extraction methods, current challenges (technical and regulatory), and commercialization outlook. Due to greenness, sustainability, and dramatic cost reduction, we envision microbial synthesis of astaxanthin offers an alternative means of production (e.g. chemical synthesis) in the near future.

Circulating miRNAs are promising liquid biopsy biomarkers for noninvasive cancer detection. However, detection of subtle, but meaningful differences in circulating miRNA quantities between diseased and healthy samples remains a key challenge in clinical settings because biomarker signal/noise ratios are often low. Because extracellular vesicles (EVs) are key sources of circulating miRNAs in serum, it was hypothesized that isolating EVs would enrich miRNA biomarkers, leading to enhanced diagnostic ability and improved biomarker performance. This research assessed the performance of EV-miRNAs against serum miRNAs as biomarkers for gastric cancer (GC). It was first determined that polymer-based precipitation (PBP) gave the highest EV-miRNA recovery when compared with ultracentrifugation, column affinity, peptide affinity, and immunobead affinity EV purification. Four PBP reagents were used to isolate EV-miRNAs from 15 GC and 15 healthy controls and 133 GC-related miRNAs were profiled from EV fractions and total serum using real-time quantitative PCR. A PBP reagent that generated the most EV-miRNA biomarkers was selected and used to validate 11 EV-miRNAs in an independent set of 20 GC and 20 controls. Eight of these EV-miRNA biomarkers were found to give better GC detection accuracy (area under the curve, approximately 0.8). Overall, data suggest that EV miRNAs can improve GC detection performance compared with serum miRNAs and led to the identification of eight EV-miRNAs as potential noninvasive biomarkers for GC.

Terpenoids constitute a structurally diverse group of natural products with wide applications in the pharmaceutical, nutritional, flavor and fragrance industries. Fungi are known to produce a large variety of terpenoids, yet fungal terpene synthases remain largely unexploited. Here, we report the sesquiterpene network and gene clusters of the black poplar mushroom Agrocybe aegerita. Among 11 putative sesquiterpene synthases (STSs) identified in its genome, nine are functional, including two novel synthases producing viridiflorol and viridiflorene. On this basis, an additional 1133 STS homologues from higher fungi have been curated and used for a sequence similarity network to probe isofunctional STS groups. With the focus on two STS groups, one producing viridiflorene/viridiflorol and one Δ6-protoilludene, the isofunctionality was probed and verified. Three new Δ6-protoilludene synthases and two new viridflorene/viridiflorol synthases from five different fungi were correctly predicted. The study herein serves as a fundamental predictive framework for the discovery of fungal STSs and biosynthesis of novel terpenoids. Furthermore, it becomes clear that fungal STS function differs between the phyla Ascomycota and Basidiomycota with the latter phylum being more dominant in the overall number and variability. This study aims to encourage the scientific community to further work on fungal STS and the products, biological functions, and potential applications of this vast source of natural products.

Background Mesenchymal stem cells (MSCs) driven gene directed enzyme prodrug therapy is a promising approach to deliver therapeutic agents to target heterogenous solid tumours. To democratize such a therapy, cryopreservation along with cold chain transportation is an essential part of the logistical process and supply chain. Previously, we have successfully engineered MSCs by a non-viral DNA transfection approach for prolonged and exceptionally high expression of the fused transgene cytosine deaminase, uracil phosphoribosyl transferase and green fluorescent protein (CD::UPRT::GFP). The aim of this study was to determine the effects of cryopreservation of MSCs engineered to highly overexpress this cytoplasmic therapeutic transgene. Methods Modified MSCs were preserved in a commercially available, GMP-grade cryopreservative—CryoStor10 (CS10) for up to 11 months. Performance of frozen-modified MSCs was compared to freshly modified equivalents in vitro. Cancer killing potency was evaluated using four different cancer cell lines. Migratory potential was assessed using matrigel invasion assay and flow cytometric analysis for CXCR4 expression. Frozen-modified MSC was used to treat canine patients via intra-tumoral injections, or by intravenous infusion followed by a daily dose of 5-flucytosine (5FC). Results We found that cryopreservation did not affect the transgene expression, cell viability, adhesion, phenotypic profile, and migration of gene modified canine adipose tissue derived MSCs. In the presence of 5FC, the thawed and freshly modified MSCs showed comparable cytotoxicity towards one canine and three human cancer cell lines in vitro. These cryopreserved cells were stored for about a year and then used to treat no-option-left canine patients with two different types of cancers and notably, the patients showed progression-free interval of more than 20 months, evidence of the effectiveness in treating spontaneously occurring cancers. Conclusion This study supports the use of cryopreserved, off-the-shelf transiently transfected MSCs for cancer treatment.

Lignocellulose is the most abundant renewable natural resource on earth and has been successfully used for the production of biofuels. A significant challenge is to develop cost-effective, environmentally friendly and efficient processes for the conversion of lignocellulose materials into suitable substrates for biotransformation. A number of approaches have been explored to convert lignocellulose into sugars, e.g. combining chemical pretreatment and enzymatic hydrolysis. In nature, there are organisms that can transform the complex lignocellulose efficiently, such as wood-degrading fungi (brown rot and white rot fungi), bacteria (e.g. Clostridium thermocellum), arthropods (e.g. termite) and certain animals (e.g. ruminant). Here, we highlight recent case studies of the natural degraders and the mechanisms involved, providing new utilities in biotechnology. The sugars produced from such biotransformations can be used in metabolic engineering and synthetic biology for the complete biosynthesis of natural medicine. The unique opportunities in using lignocellulose directly to produce natural drug molecules with either using mushroom and/or ‘industrial workhorse’ organisms (Escherichia coli and Saccharomyces cerevisiae) will be discussed.

Background Clinicians need improved tools to better identify nonacute heart failure with preserved ejection fraction (HFpEF). Objectives The purpose of this study was to derive and validate circulating microRNA signatures for nonacute heart failure (HF). Methods Discovery and validation cohorts (N = 1,710), comprised 903 HF and 807 non-HF patients from Singapore and New Zealand (NZ). MicroRNA biomarker panel discovery in a Singapore cohort (n = 546) was independently validated in a second Singapore cohort (Validation 1; n = 448) and a NZ cohort (Validation 2; n = 716). Results In discovery, an 8-microRNA panel identified HF with an area under the curve (AUC) 0.96, specificity 0.88, and accuracy 0.89. Corresponding metrics were 0.88, 0.66, and 0.77 in Validation 1, and 0.87, 0.58, and 0.74 in Validation 2. Combining microRNA panels with N-terminal pro–B-type natriuretic peptide (NT-proBNP) clearly improved specificity and accuracy from AUC 0.96, specificity 0.91, and accuracy 0.90 for NT-proBNP alone to corresponding metrics of 0.99, 0.99, and 0.93 in the discovery and 0.97, 0.96, and 0.93 in Validation 1. The 8-microRNA discovery panel distinguished HFpEF from HF with reduced ejection fraction with AUC 0.81, specificity 0.66, and accuracy 0.72. Corresponding metrics were 0.65, 0.41, and 0.56 in Validation 1 and 0.65, 0.41, and 0.62 in Validation 2. For phenotype categorization, combined markers achieved AUC 0.87, specificity 0.75, and accuracy 0.77 in the discovery with corresponding metrics of 0.74, 0.59, and 0.67 in Validation 1 and 0.72, 0.52, and 0.68 in Validation 2, as compared with NT-proBNP alone of AUC 0.71, specificity 0.46, and accuracy 0.62 in the discovery; with corresponding metrics of 0.72, 0.44, and 0.57 in Validation 1 and 0.69, 0.48, and 0.66 in Validation 2. Accordingly, false negative (FN) (81% Singapore and all NZ FN cases were HFpEF) as classified by a guideline-endorsed NT-proBNP ruleout threshold, were correctly reclassified by the 8-microRNA panel in the majority (72% and 88% of FN in Singapore and NZ, respectively) of cases. Conclusions Multi-microRNA panels in combination with NT-proBNP are highly discriminatory and improved specificity and accuracy in identifying nonacute HF. These findings suggest potential utility in the identification of nonacute HF, where clinical assessment, imaging, and NT-proBNP may not be definitive, especially in HFpEF.

Simple Summary Breast cancer screening by mammography suffers from high rates of false positivity, resulting in unnecessary investigative imaging and biopsies. There is an unmet need for biomarkers that can distinguish between malignant and benign breast lesions. We performed miRNA profiling on 638 patients with abnormal mammograms and 100 healthy controls. A six-miRNA panel was identified and validated in an independent cohort that had an AUC of 0.881 when differentiating between cases versus those with benign lesions or healthy individuals with normal mammograms. In addition, biomarker panel scores increased with tumor size, stage and number of lymph nodes involved. This study demonstrates that circulating miRNAs can potentially be used in conjunction with mammography to differentiate between patients with malignant and benign breast lesions. Abstract Mammography is extensively used for breast cancer screening but has high false-positive rates. Here, prospectively collected blood samples were used to identify circulating microRNA (miRNA) biomarkers to discriminate between malignant and benign breast lesions among women with abnormal mammograms. The Discovery cohort comprised 72 patients with breast cancer and 197 patients with benign breast lesions, while the Validation cohort had 73 and 196 cancer and benign cases, respectively. Absolute expression levels of 324 miRNAs were determined using RT-qPCR. miRNA biomarker panels were identified by: (1) determining differential expression between malignant and benign breast lesions, (2) focusing on top differentially expressed miRNAs, and (3) building panels from an unbiased search among all expressed miRNAs. Two-fold cross-validation incorporating a feature selection algorithm and logistic regression was performed. A six-miRNA biomarker panel identified by the third strategy, had an area under the curve (AUC) of 0.785 and 0.774 in the Discovery and Validation cohorts, respectively, and an AUC of 0.881 when differentiating between cases versus those with benign lesions or healthy individuals with normal mammograms. Biomarker panel scores increased with tumor size, stage and number of lymph nodes involved. Our work demonstrates that circulating miRNA signatures can potentially be used with mammography to differentiate between patients with malignant and benign breast lesions.

Mesenchymal stem cells (MSCs) driven gene-directed enzyme prodrug therapy has emerged as a potential strategy for cancer treatment. The tumour-nesting properties of MSCs enable these vehicles to target tumours and metastases with effective therapies. A crucial step in engineering MSCs is the delivery of genetic material with low toxicity and high efficiency. Due to the low efficiency of current transfection methods, viral vectors are used widely to modify MSCs in preclinical and clinical studies. We show, for the first time, the high transfection efficiency (> 80%) of human adipose tissue derived-MSCs (AT-MSCs) using a cost-effective and off-the-shelf Polyethylenimine, in the presence of histone deacetylase 6 inhibitor and fusogenic lipids. Notably, the phenotypes of MSCs remained unchanged post-modification. AT-MSCs engineered with a fused transgene, yeast cytosine deaminase::uracil phosphoribosyltransferase (CDy::UPRT) displayed potent cytotoxic effects against breast, glioma, gastric cancer cells in vitro. The efficiency of eliminating gastric cell lines were effective even when using 7-day post-transfected AT-MSCs, indicative of the sustained expression and function of the therapeutic gene. In addition, significant inhibition of temozolomide resistant glioma tumour growth in vivo was observed with a single dose of therapeutic MSC. This study demonstrated an efficient non-viral modification process for MSC-based prodrug therapy.

Optimization of metabolic pathways consisting of large number of genes is challenging. Multivariate modular methods (MMMs) are currently available solutions, in which reduced regulatory complexities are achieved by grouping multiple genes into modules. However, these methods work well for balancing the inter-modules but not intra-modules. In addition, application of MMMs to the 15-step heterologous route of astaxanthin biosynthesis has met with limited success. Here, we expand the solution space of MMMs and develop a multidimensional heuristic process (MHP). MHP can simultaneously balance different modules by varying promoter strength and coordinating intra-module activities by using ribosome binding sites (RBSs) and enzyme variants. Consequently, MHP increases enantiopure 3S,3′S-astaxanthin production to 184 mg l−1 day−1 or 320 mg l−1. Similarly, MHP improves the yields of nerolidol and linalool. MHP may be useful for optimizing other complex biochemical pathways., Achieving high titer yield and productivity of target chemicals in industrial organism depends on multidimensional pathway optimization. Here, the authors use a refined modular method called multidimensional heuristic process to improve production of astaxanthin, nerolidol and linalool in E. coli.

Apocarotenoids, such as α-, β-ionone and retinol, have high commercial values in the food and cosmetic industries. The demand for natural ingredients has been increasing dramatically in recent years. However, attempts to overproduce β-ionone in microorganisms have been limited by the complexity of the biosynthetic pathway. Here, an Escherichia coli-based modular system was developed to produce various apocarotenoids. Incorporation of enzyme engineering approaches (N-terminal truncation and protein fusion) into modular metabolic engineering strategy significantly improved α-ionone production from 0.5 to 30 mg/L in flasks, producing 480 mg/L of α-ionone in fed-batch fermentation. By modifying apocarotenoid genetic module, this platform strain was successfully re-engineered to produce 32 mg/L and 500 mg/L of β-ionone in flask and bioreactor, respectively (> 80-fold higher than previously reported). Similarly, 33 mg/L of retinoids was produced in flask by reconstructing apocarotenoid module, demonstrating the versatility of the "plug-n-play" modular system. Collectively, this study highlights the importance of the strategy of simultaneous modular pathway optimization and enzyme engineering to overproduce valuable chemicals in microbes. This article is protected by copyright. All rights reserved

The preservation of nucleic acids from clinical samples is critical to facilitate accurate molecular diagnosis. The use of a paper matrix, Flinders Technology Associates (FTA) Elute cards, to archive DNA and viral RNA is well-documented. However, the feasibility of FTA Elute cards for archiving serum and serum exosomal microRNAs (miRNAs) remains unclear. Here, we performed a comprehensive evaluation of FTA Elute cards for miRNA storage and recovery in different pre-analytical conditions. The recovery of serum miRNA dry-spotted on FTA Elute cards by direct elution with water at high temperature was poor. However, serum miRNAs dry-spotted on the cards were isolated with about 40% yield when using QIAzol lysis reagent and recovery was improved remarkably (>80%) upon extraction from cards pre-treated with trehalose. miRNAs stored on the cards remained stable at room temperature and can be kept for prolonged periods. Furthermore, miRNAs could be similarly recovered from serum exosomes dry-spotted on the cards. Importantly, when using sera from gastric cancer (GC) patients, the miRNAs were efficiently recovered from trehalose pre-treated cards without affecting their representation. Collectively, we have demonstrated the potential of FTA Elute cards to archive serum and serum exosomal miRNAs, making it useful for biomarker discovery and diagnostics.

The Singapore Integrative Omics Study provides valuable insights on establishing population reference measurement in 364 Chinese, Malay, and Indian individuals. These measurements include > 2.5 millions genetic variants, 21,649 transcripts expression, 282 lipid species quantification, and 284 clinical, lifestyle, and dietary variables. This concept paper introduces the depth of the data resource, and investigates the extent of ethnic variation at these omics and non-omics biomarkers. It is evident that there are specific biomarkers in each of these platforms to differentiate between the ethnicities, and intra-population analyses suggest that Chinese and Indians are the most biologically homogeneous and heterogeneous, respectively, of the three groups. Consistent patterns of correlations between lipid species also suggest the possibility of lipid tagging to simplify future lipidomics assays. The Singapore Integrative Omics Study is expected to allow the characterization of intra-omic and inter-omic correlations within and across all three ethnic groups through a systems biology approach., The Singapore Genome Variation projects characterized the genetics of Singapore’s Chinese, Malay, and Indian populations. The Singapore Integrative Omics Study introduced here goes further in providing multi-omic measurements in individuals from these populations, including genetic, transcriptome, lipidome, and lifestyle data, and will facilitate the study of common diseases in Asian communities.

In vitro metabolic engineering is an alternative approach to cell-based biosynthesis. It offers unprecedented flexibility for the study of biochemical pathways, thus providing useful information for the rational design and assembly of reaction modules. Herein, we took the advantage of in vitro metabolic engineering to initially gain insight into the regulatory network of a reconstituted amorpha-4,11-diene (AD) synthetic pathway. Guided by lin-log approximation, we rapidly identified the hitherto unrecognized inhibition of adenosine triphosphate (ATP) on both farnesyl pyrophosphate synthase (FPPS) and amorpha-4,11-diene synthase (ADS). Furthermore, the byproduct, pyrophosphate (PPi), potently inhibits ADS, but not FPPS. To lower the inhibition, an ATP recycling system and pyrophosphatase were used and resulted in a significant (∼3-fold) enhancement in the rate of AD production (∼5.7 μmol L–1 min–1). A coimmobilized multienzyme reaction system was then developed to recycle the enzymes. When inhibitory metab...

Astaxanthin is a natural pigment, known for its strong antioxidant activity and numerous health benefits to human and animals. Its antioxidant activity is known to be substantially greater than β-carotene and about a thousand times more effective than vitamin E. The potential health benefits have generated a growing commercial interest, and the escalating demand has prompted the exploration of alternative supply chain. Astaxanthin naturally occurs in many sea creatures such as trout, shrimp, and microalgae, some fungi, bacteria, and flowering plants, acting to protect hosts against environmental stress and adverse conditions. Due to the rapid growth and simple growth medium requirement, microbes, such as the microalga, Haematococcus pluvialis, and the fungus Xanthophyllomyces dendrorhous, have been developed to produce astaxanthin. With advances in metabolic engineering, non-carotenogenic microbes, such as Escherichia coli and Saccharomyces cerevisiae, have been purposed to produce astaxanthin and significant progress has been achieved. Here, we review the recent achievements in microbial astaxanthin biosynthesis (with reference to metabolic engineering strategies) and extraction methods, current challenges (technical and regulatory), and commercialization outlook. Due to greenness, sustainability, and dramatic cost reduction, we envision microbial synthesis of astaxanthin offers an alternative means of production (e.g. chemical synthesis) in the near future.

Additional file 8. Scaling up MSC modification process on microcarrier culture. AD-MSCs were seeded at 28,000/cm2 on Cytodex® 3 microcarriers (total surface area of 1.9 cm2) in 24-well non-adherent plates, with agitation speed of 50 rpm for 24 h before transfection. Similar to flat-bed transfection, the polymer and DNA complex (at 200-300 ng of pDNA) were added to the cell culture using a dropwise manner after 15 min incubation. Cells were transfected in the presence or absence of the enhancer. Two-day post transfection, a the fluorescent images were captured at 10x magnification. Representative images are shown. b After which, cells were harvested through trypsinization. To separate the cells from microcarrier, the suspension cells were filtered through 70 μm cell strainer. The transfection efficiencies were determined through flow cytometry analysis. Cell viability based on PI exclusion was determined with NC-3000 automated cell counter. The combination chart presents % of GFP+ cells (graph bar) and cell viability (mark type) Data of biological triplicates are expressed as mean + SD. c For microcarriers with total surface area of 1.9 cm2 and 9.5 cm2, cells were transfected in 24-well non-adherent plates. To further scale up the transfection process, AD-MSCs were seeded on Cytodex® 3 (total surface area of 47.5 cm2) at 28,000 cells/cm2 in 125 mL Erlenmeyer flasks. One day later, cells were transfected in the presence of Enhancer. The amount of DNA was fixed at 150 ng/cm2 of microcarriers. Two-day post transfection, transfection efficiency was analysed. The scatter plot represents absolute number of GFP+ cells collected from each culture vessel; deduced from the readout of cell counting and flow cytometry analysis of the GFP expression. Data are expressed as mean + SD, n = 3.

Additional file 14. AD-MSCs generated with PEI plus Enhancers outperformed other methods. AD-MSCs were transfected with CD::UPRT::GFP plasmid using various protocols. Twenty-four hours post-transfection, CD::UPRT::GFP_AD-MSCs were cocultured with U-251MG in DMEM supplemented with 2% FBS, in the presence or absence of 100 μg/mL 5FC. The therapeutic cells were mixed at ratios of 1 CD::UPRT::GFP_AD-MSC to 25, 10, 5, 1 cancer cells. Seven days later, cell viability in the treatment conditions was evaluated spectrophotometrically by MTS assay. Cell viability was defined as sample/control × 100%. Conditions without 5FC treatment served as controls. No MSC condition suggests lack of 5FC cytotoxicity in cancer cells. Data presents mean + SD of the biological quadruplicates. Statistical differences between Lipofectamine 3000 and other methods were calculated using two tailed Student’s t-test. **, P

Additional file 9. Representative images and FACS profile of AD-MSCs transfected with 300 ng of CD::UPRT::GFP plasmid, in the presence or absence of the Enhancer.

Additional file 6. Supplementation of Enhancer to improve transfection in AD-MSCs. One day post seeding of 50,000 AD-MSCs, cells were transfected by 150-500 ng of PF463-CMV-GFP complexed with PEI at 1 μg pDNA to 3 μL PEI, in the presence or absence of Enhancer. a Two days post-transfection, the fluorescent images were captured at 4x magnification. Representative images are presented. b After which, cells were harvested for FACS analysis. Untransfected MSC served as negative control for gating. Data represents mean ± SD, n = 3 (Bar graph).

Additional file 2. Flow cytometry profiles of the cell cycle of the TMZ sensitive and resistant cell lines in the presence and absence of TMZ treatment. The number of cells acquired during flow cytometry measurement is 5000 per sample. The analysis of the cell cycle is presented in Fig. 1c and d.

Additional file 7. Scaling out MSC modification process on flat-bed culture. AD-MSCs were seeded in 6-well plate, T25, T75 and T175 flasks at 20,000/cm2. One day post seeding, cells were transfected with 150 ng PF463-CMV-GFP/ cm2 complexed at 1 μg pDNA to 3 μL PEI. Two-day post transfection, cells were harvested for analysis. Total number of cells harvested from each culture vessels were determined by the automated cell counter NC-3000. After which, the % of GFP+ cells measured with flow cytometry. a The scatter plot represents absolute number of GFP+ cells collected from each culture vessel; deduced from the readout of cell counting and flow cytometry of the GFP expression. Data of biological triplicates are expressed as mean + SD. b Representative images present the flow cytometry profile of unmodified and modified AD-MSCs harvested from T175 flasks.

Additional file 5. Determination of the transfection efficiencies of various commercial carriers in AD-MSCs. One day post seeding of 50,000 AD-MSCs, cells were transfected with different gene carriers at various GFP encoded plasmid (PF463-CMV-GFP, PlasmidFactory) and gene carrier amounts. AD-MSCs were transfected with a Lipofectamine 3000, b Polyfect, c Transficient, and d Turbofect according to the manufacturer’s instructions. e For cells transfected with PEI, the protocol is detailed in methods and materials section. Two-day post transfection, AD-MSCs were harvested. Transfection efficiency and cell viability (Propidium Iodide exclusion assay) were determined using NucleoCounter®NC-3000™. For each gene carrier, the left and right graph bar presents % of GFP+ cells and % of cell viability (% of PI- population), respectively. Data represents mean ± SD, n = 3.

Additional file 3. Gene expression of genes related in 5FU resistance pathway. Fold change of expression for DPYD, TYMS and UMPS in a U-251MG and b U-87MG TMRZ cell lines were calculated in relative to their respective parental cell lines. Similarly, changes in the expression of ABCC5 transporter were calculated accordingly for c U-251MG and d U-87MG TMZR cell lines. All samples were analysed in triplicates. The fold change in the expressions of the gene of interest was calculated after normalization to the house keeping gene GAPDH. Line graph shows the average fold change in gene expression, mean + SD (n = 3). Significant differences between parental and TMZR cells were calculated using unpaired, two-tailed Student’s t-test. p-value

Additional file 4. Gene expression z-score of patient derived cell lines for 5-FU pathway. DPYD, TYMS, UMPS, TYMP and ABCC5 expression levels are shown. The information was obtained from www.hgcc.se Dated: 3 Jun 2019.

Backgrounds: Abundant and renewable biomaterials serve as ideal substrates for the sustainable production of various chemicals, including natural products (e.g., pharmaceuticals and nutraceuticals). For decades, researchers have been focusing on how to engineer microorganisms and developing effective fermentation processes to overproduce these molecules from biomaterials. Despite many laboratory achievements, it remains a challenge to transform some of these into successful industrial applications. Results: Here, we review recent progress in strategies and applications in metabolic engineering for the production of natural products. Modular engineering methods, such as a multidimensional heuristic process markedly improve efficiencies in the optimization of long and complex biosynthetic pathways. Dynamic pathway regulation realizes autonomous adjustment and can redirect metabolic carbon fluxes to avoid the accumulation of toxic intermediate metabolites. Microbial co-cultivation bolsters the identification and overproduction of natural products by introducing competition or cooperation of different species. Efflux engineering is applied to reduce product toxicity or to overcome storage limitation and thus improves product titers and productivities. Conclusion: Without dispute, many of the innovative methods and strategies developed are gradually catalyzing this transformation from the laboratory into the industry in the biosynthesis of natural products. Sometimes, it is necessary to combine two or more strategies to acquire additive or synergistic benefits. As such, we foresee a bright future of the biosynthesis of pharmaceuticals and nutraceuticals in microbes from renewable biomaterials.

Cationic polymers remain attractive tools for non-viral gene transfer. The effectiveness of these vectors rely on the ability to deliver plasmid DNA (pDNA) into the nucleus of cells. While we have previously demonstrated the potential of Lignin-PGEA-PEGMA as a non-viral gene delivery vector, alterations of cellular phenotype and cytotoxicity were observed post transfection. The present study aims to explore transfection conditions for high efficiency and low toxicity of the Lignin-PGEA-PEGMA based gene delivery system. Cellular toxicity was significantly reduced by using the centrifugation protocol, which enables rapid deposition of DNA complexes. Replacement of media post centrifugation resulted in minimal exposure of cells to excess polymers, which were toxic to cells. At an optimized DNA amount (500–750 ng) and molar ratios of nitrogen (N) in polymer to phosphate (P) in pDNA (N/P = 30–40), with the use of a novel transfection enhancer that facilitates endosomal escape and nuclear trafficking, the efficiency of gene delivery was increased significantly 24 h post transfection. The present study demonstrated an appropriately optimized protocol that enabled the utility of a novel cationic polymer blend with a mixture of fusogenic lipids and a histone deacetylate inhibitor in non-viral transfection, thereby providing an attractive alternative to costly commercial gene carriers.

Metabolic engineering aims at altering cellular metabolism to produce valuable products at high yields and titers. Achieving high titers and productivity can be challenging if final products are largely accumulated intracellularly. A potential solution to this problem is to facilitate the export of these substances from cells by membrane transporters. Amorphadiene, the precursor of antimalarial drug artemisinin, is known to be secreted from Escherichia coli overexpressing the biosynthetic pathway. In order to assess the involvement of various endogenous efflux pumps in amorphadiene transport, the effects of single gene deletion of 16 known multidrug-resistant membrane efflux transporters were examined. The outer membrane protein TolC was found to be intimately involved in amorphadiene efflux. The overexpression of tolC together with ABC family transporters (macAB) or MFS family transporters (emrAB or emrKY) enhanced amorphadiene titer by more than threefold. In addition, the overexpression of transporters in the lipopolysaccharide transport system (msbA, lptD, lptCABFG) was found to improve amorphadiene production. As efflux transporters often have a wide range of substrate specificity, the multiple families of transporters were co-expressed and synergistic benefits were observed in amorphadiene production. This strategy of screening and then rationally engineering transporters can be used to improve the production of other valuable compounds in E. coli. Biotechnol. Bioeng. 2016;113: 1755-1763. © 2016 Wiley Periodicals, Inc.

A silicon nanowire platform prepared by glancing angle deposition and metal assisted chemical etching (GLAD-MACE) was used for oligonucleotides hybridization. The limit of detection of this platform was enhanced due to the large amount of probe molecules that can be accommodated on the nanowire surface and pores on the sidewall. In contrast to conventional substrates, the GLAD-MACE nanowires can accept 100 times more probes without showing probe steric hindrance. Compared to the detection of oligonucleotides with fluorescent reporters on a traditional substrate, even those facilitated by a microfluidic mixing chamber, at least a 10 times lower LoD could be reached with a passive hybridization strategy. For a device built with GLAD-MACE nanowires, it is clear that one important factor to optimize the system performance was to design an apparatus that can accelerate the diffusion process of antisense DNAs.

One-pot multienzyme biosynthesis is an attractive method for producing complex, chiral bioactive compounds. It is advantageous over step-by-step synthesis, as it simplifies the process, reduces costs and often leads to higher yield due to the synergistic effects of enzymatic reactions. In this study, dihydroartemisinic acid (DHAA) pathway enzymes were overexpressed in Saccharomyces cerevisiae, and whole-cell biotransformation of amorpha-4,11-diene (AD) to DHAA was demonstrated. The first oxidation step by cytochrome P450 (CYP71AV1) is the main rate-limiting step, and a series of N-terminal truncation and transcriptional tuning improved the enzymatic activity. With the co-expression of artemisinic aldehyde dehydrogenase (ALDH1), which recycles NADPH, a significant 8-fold enhancement of DHAA production was observed. Subsequently, abiotic conditions were optimized to further enhance the productivity of the whole-cell biocatalysts. Collectively, approximately 230 mg/L DHAA was produced by the multi-step whole-cell reaction, a ~50% conversion from AD. This study illustrates the feasibility of producing bioactive compounds by in vitro one-pot multienzyme reactions.

Background: Survival outcomes of breast cancer patients can be significantly improved by early detection and treatment. Implementation of mammogram-based screening has significantly improved early detection of breast cancer in the west. However, the use of screening mammography is less prevalent in Asia partly due to social and cultural reasons. The aim of this study was to determine if a serum microRNA (miRNA) panel could be used as blood-based biomarkers to assist in the early detection of breast cancer. Methods: We carried out a multi-center, multi-ethnic study to identify and validate miRNA biomarkers for the early detection of breast cancer. A total of 1042 subjects including 540 breast cancer cases (predominantly stage 1 and 2 cases) and 502 matched controls from 6 independent sources were included in this study. Among these, there were 750 American and European subjects recruited by biobanks and 292 Singaporean Asian Subjects recruited at the National Cancer Centre Singapore and the National University Hospital. The study was conducted in 3 phases in which sera of 289 European Caucasian serum samples (Discovery Cohort) were first interrogated to identify differentially expressed miRNAs between early-stage breast cancer cases and matched controls among 520 circulating miRNA candidates by quantitative RT-PCR using MiRXES assays. The remaining 753 subjects from 5 independent sources were assigned into two groups for biomarker optimization/algorithm development (Optimization Cohort, n=374) and validation (Validation Cohort, n=379). Results: Among the 520 circulating miRNAs measured, 241 were quantified in absolute copy numbers for 289 subjects in the Discovery Cohort. Thirty-three candidate miRNAs were identified. These miRNAs consistently showed differential expression between cancer and control subjects in the Optimization Cohort. A multi-variant panel of 8 miRNAs and an algorithm was developed using the Discovery and Optimization Cohort, with an AUC of 0.981 and 0.918 respectively. When validated in the independent Validation Cohort, the panel demonstrated an AUC of 0.915. Conclusion: We developed and validated a serum miRNA panel that is both sensitive (72.2 - 77.4%) and specific (90.2 - 91.5%) in detecting early stage of breast cancer in both Caucasian and Asian populations. Citation Format: Lihan Zhou, Ruiyang Zou, Sau Yeen Loke, Mikael Hartman, Patrick C.K Goo, Ann S.G. Lee-Lim, Heng-Phon Too. Identification and validation of a serum microRNA panel for detection of early-stage breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-01-02.

To date, low transfection efficiency remains the major drawback of polymer based gene delivery. Many cell types including stem cells, fibroblast and neurons are known to be poorly transfected with polymer based gene carriers and the high toxicity severely restrict their utility in gene delivery. Continual efforts are made to identify cellular barriers to efficient transfection as these carriers have low immunogenicity, ease of manufacturing and scalability. Here, we summarize the current status of understanding on uptake mechanism of polymer-DNA complexes (polyplexes), their endosomal escape, cytosolic transport and nuclear entry of pDNA.

MicroRNAs (miRNAs) are master regulators of gene expression at post-transcriptional level. The present study investigated the involvement of miRNAs in topological guidance of neurite outgrowth in an NGF treated PC12 cell model cultured on nano-patterned polyethylene terephthalate (PET) substrates fabricated with interference lithography. The expressions of 38 neuronal miRNAs were measured and 3 were found to be differentially regulated during topological guidance of neurite outgrowth. Altering the intracellular levels of these miRNAs disrupted the orderly growth of neurite along nano-patterned substrate. Our results showed miRNAs to be versatile regulators and their involvement should be thoroughly investigated for better understanding of biological processes. From the Clinical Editor In this basic science study, strong evidence was found that topological guidance is only one factor, and miRNA-s regulate axonal outgrowth from neurites. Nano-patterned polyethylene terephthalate substrates were used for the study, fabricated using interference lithography. Further studies of this biologically relevant process may pave the way to clinically useful axonal regrowth and axonal guidance methods.

Deep brain stimulation (DBS) is an established therapy for movement disorders such as Parkinson's disease (PD). Although the efficacy of DBS is clear, its precise molecular mechanism remains unknown. The glial cell line derived factor (GDNF) family of ligands has been shown to confer neuroprotective effects on dopaminergic neurons, and putaminal infusion of GDNF have been investigated in PD patients with promising results. Despite the potential therapeutic role of GDNF in alleviating motor symptoms, there is no data on the effects of electrical stimulation on GDNF-family receptor (GFR) expression in the basal ganglia structures. Here, we report the effects of electrical stimulation on GFRα1 isoforms, particularly GFRα1a and GFRα1b. Wistar rats underwent 2 hours of high frequency stimulation (HFS) at the globus pallidus interna nucleus. A control group was subjected to a similar procedure but without stimulation. The HFS group, sacrificed 24 hours after treatment, had a threefold decrease in mRNA expression level of GFRα1b (p=0.037), but the expression level reverted to normal 72 hours after stimulation. Our preliminary data reveal the acute effects of HFS on splice isoforms of GFRα1, and suggest that HFS may modulate the splice isoforms of GFRα1a and GFRα1b to varying degrees. Going forward, elucidating the interactions between HFS and GFR may shed new insights into the complexity of GDNF signaling in the nervous system and lead to better design of clinical trials using these signaling pathways to halt disease progression in PD and other neurodegenerative diseases.

Gliomas account for 70% of human malignant primary brain tumours. The most common form is glioblastoma multiforme, World Health Organization grade IV. Despite the implementation of post-operative adjuvant radiotherapy with concurrent temozolomide (TMZ), the disease’s overall prognosis remains dismal. TMZ is currently the only mono-chemotherapeutic agent for newly-diagnosed high-grade glioma patients and acquired resistance inevitably occurs in the majority of such patients, further limiting treatment options. Therefore, there is an urgent need to better understand the underlying mechanisms involved in TMZ resistance, a critical step to developing effective, targeted treatments. An emerging body of evidence suggests the intimate involvement of a novel class of nucleic acid, microRNA (miRNA), in tumorigenesis and disease progression for a number of human malignancies, including primary brain tumours. miRNA are short, single-stranded, non-coding RNA (∼22 nucleotides) that function as post-transcriptional regulators of gene expression. This review provides an overview of the key treatment obstacles faced in patients with high-grade gliomas, especially in the context of recurrent, chemoresistant tumours and the potential roles of miRNA in chemoresistance and management of this disease.

4065 Background: High mortality from gastric cancer is related to the late manifestation of its symptoms. A blood-based non-invasive biomarker with the ability to detect all stages of gastric cancer could significantly improve patient outcomes. We aimed to develop a novel serum miRNA assay for diagnosis of gastric cancer. Methods: We conducted a multi-center study involving 892 gastric cancer and control subjects from Singapore and Korea to develop a multi-target miRNA assay. Using RT-qPCR, we quantified the expressions of 578 serum miRNAs and constructed a 12-miR biomarker panel through multi-variant data analysis. The results were generated with the use of a logistic-regression algorithm, with the value of 40 or more considered to be positive. We subsequently validated this multi-miR assay in a large prospective cohort involving 4566 subjects and compared its performance with traditional markers such as H.Pylori and Pepsinogen. All participants underwent gastroscopy independent of the assay results. Results: Of the 4566 subjects that underwent gastroscopy and histopathological examination in the prospective cohort, 125 were diagnosed with gastric cancer. The 12-miR assay achieved an Area-Under-Curve (AUC) of 0.84, significantly outperforming (p-value < 0.01) that of H.Pylori (AUC of 0.64) and Pepsinogen (AUC of 0.62). The sensitivity of the miRNA assay in detecting early (stage 0-2) and late (stage 3-4) stage gastric cancer was 82.6% (95% CI, 68.6% to 92.2%) and 88.4% (95% CI, 78.4% to 94.9%) respectively at a specificity of 70.0% (95% CI, 67.8% to 71.9%). In comparison, H.Pylori showed a sensitivity of 80.4% at a specificity of 44.3% whereas the Pepsinogen showed sensitivity of 9.52% at a specificity of 95.3%. Using the miRNA assay as a pre-screening tool could potentially reduce number of endoscopy needed by 62% in detecting one case of gastric cancer. Conclusions: Our serum miRNA panel is a useful, non-invasive screening test for gastric cancer. It is cost-effective as it can reduce unnecessary diagnostic endoscopy.

3051 Background: The implementation of mammogram-based screening has significantly improved the early detection of breast cancer in the west. However, the use of screening mammography is less prevalent in Asia partly due to social and cultural reasons. The aim of this study was to determine if a serum microRNA (miRNA) panel could be used as biomarkers to assist in the early detection of breast cancer. Methods: We conducted a multi-center, multi-ethnic study to identify and validate miRNA biomarkers for the early detection of breast cancer. A total of 1070 subjects including 550 breast cancer cases (predominantly stage 1 and 2) and 520 matched controls from 6 independent sources were included in this study. Among these, there were 768 American and European subjects recruited by biobanks and 302 Singaporean Asian Subjects recruited at the National Cancer Centre Singapore and the National University Hospital. The study was conducted in 3 phases. First, 119 European Caucasian serum samples (Discovery Cohort) were interrogated to identify differentially expressed miRNAs between early-stage breast cancer cases and matched controls, among 520 circulating miRNA candidates by quantitative RT-PCR using MiRXES assays. The remaining 951 subjects from 5 independent sources were assigned into two groups for biomarker optimization/algorithm development (Optimization Cohort, n = 451) and validation (Validation Cohort, n = 500). Results: Among the 520 circulating miRNAs measured, 241 were quantified in absolute copy numbers for 119 subjects in the Discovery Cohort. Thirty-two candidate miRNAs were identified. These miRNAs consistently showed differential expression between cancer and control subjects in the Optimization Cohort. A multi-variant panel of 8 miRNAs and an algorithm was developed using the combined Discovery and Optimization Cohorts, with an AUC of > 0.90. When validated in the independent Validation Cohort, the panel demonstrated an AUC of > 0.85. Conclusions: We developed and validated a serum miRNA panel that is both sensitive (~70%) and specific (~90%) in detecting early-stage breast cancer.

Background & Aim Mesenchymal stem cells (MSC) are emerging as promising vehicles for Gene-directed enzyme prodrug therapy (GDEPT). The inherent tumor-trophic migratory properties of MSC enable these vehicles to deliver effective, targeted therapy to tumors and metastatic diseases. A critical step in modifying MSC is the delivery of genes with high efficiency and low cytotoxicity. Due to the poor efficiency of transfection approaches, viral methods are used extensively to transduce MSC in preclinical and clinical studies. This study aims to develop a scalable non viral gene delivery method to efficiently modify MSC. Methods, Results & Conclusion Methods TrafEn (Trafficking Enhancer), to enhance transfection using off-the-shelf, cost-effective polymers. TrafEn was rationally developed to facilitate efficient trafficking of the genetic material inside cells. Polyplex transfection was enhanced by including a simultaneous treatment with DOPE/CHEMS lipid suspension and a microtubule stabilizer, a histone deacetylase-6 inhibitor. Result We demonstrate, for the first time, the efficient transfection (>90%) of human adipose tissue derived MSCs (AT-MSCs) using an off-the shelf and cost-effective cationic polymer, polyethylenimine, in the presence of fusogenic lipids and histone deacetylase 6 inhibitor (HDAC6i) (Figure 1). Importantly, the cell phenotypes of MSCs remained unchanged after modification, a key requisite for clinical application of MSCs. AT-MSCs modified with a fused transgene, yeast cytosine deaminase::uracil phosphoribosyltransferase (CDy::UPRT), exhibited strong cytotoxic effects towards glioma, breast and gastric cancer cells in vitro. The efficiency of killing of gastric MKN1 and MKN28 cell lines were greater than 80% even with 7 days post-transfected AT-MSCs, indicative that the expression period of the therapeutic gene was sustainable. Conclusion This study describes a useful tool for polymer based ex vivo MSC modification which is highly scalable and cost-effective. The proposed workflow bypasses the restriction in viral vector supply and expedites MSC modification, without compromising the quality and anti-cancer efficacy of the theranostic MSCs.

We present the results of a systematic study on the porosity of silica microparticles and nanowires prepared by glancing angle deposition-metal-assisted chemical etching (GLAD-MACE) and interference lithography-metal-assisted chemical etching (IL-MACE) techniques using the thermoporometry (TPM) method. Good agreement was obtained between our TPM results and published data provided by the suppliers of silica microparticles. TPM characterization of the GLAD-MACE and IL-MACE nanowires was carried out on the basis of parameters obtained from TPM experiments on microparticles. Our nanowires showed a similar trend but lower values of the pore volume and surface area than nanowires prepared by MACE with AgNO3 solution. We attribute the enhanced bioanalysis performance of the GLAD-MACE nanowires based devices to the increased pore volume and total surface area of the nanowires.

Neurturin (NRTN), a member of the GDNF family of ligands (GFL), is currently investigated in a series of clinical trials for Parkinson's disease. NRTN signals through its cognate receptor GFRα2 and co-receptor RET to induce neurite outgrowth, but the underlying mechanism remains to be better understood. STAT3 was previously shown to be activated by oncogenic RET, independent of ligand and GFRα. In this study, we demonstrated that NRTN induced serine727 but not tyrosine705 phosphorylation of STAT3 in primary cortical neuron and neuronal cell lines. Remarkably, STAT3 phosphorylation was found to be mediated specifically by GFRα2c and RET9 isoforms. Furthermore, serine but not tyrosine dominant negative mutant of STAT3 impaired NRTN induced neurite outgrowth, indicative of the role of STAT3 as a downstream mediator of NRTN function. Similar to NGF, the NRTN induced P-Ser-STAT3 was localized to the mitochondria but not to the nucleus. Mitochondrial STAT3 was further found to be intimately involved in NRTN induced neurite outgrowth. Collectively, these findings demonstrated the hitherto unrecognized and novel role of specific GFRα2 and RET isoforms in mediating NRTN activation of STAT3 and the transcription independent mechanism whereby the mitochondria localized P-Ser-STAT3 mediated NRTN induced neurite outgrowth.