Oxidative stress‐induced angiogenesis is mediated by miR‐205‐5p

miR‐205‐5p is known to be involved in VEGF‐related angiogenesis and seems to regulate associated cell signalling pathways, such as cell migration, proliferation and apoptosis. Therefore, several studies have focused on the potential role of miR‐205‐5p as an anti‐angiogenic factor. Vascular proliferation is observed in diabetic retinopathy and the ‘wet’ form of age‐related macular degeneration. Today, the most common treatments against these eye‐related diseases are anti‐VEGF therapies. In addition, both AMD and DR are typically associated with oxidative stress; hence, the use of antioxidant agents is accepted as a co‐adjuvant therapy for these patients. According to previous data, ARPE‐19 cells release pro‐angiogenic factors when exposed to oxidative insult, leading to angiogenesis. Matching these data, results reported here, indicate that miR‐205‐5p is modulated by oxidative stress and regulates VEGFA‐angiogenesis. Hence, miR‐205‐5p is proposed as a candidate against eye‐related proliferative diseases.     

Pro‐inflammatory angiogenesis is mediated by p38 MAP kinase

Chronic inflammation is tightly linked to diseases associated with endothelial dysfunction including aberrant angiogenesis. To better understand the endothelial role in pro‐inflammatory angiogenesis, we analyzed signaling pathways in continuously activated endothelial cells, which were either chronically exposed to soluble TNF or the reactive oxygen species (ROS) generating H₂O₂, or express active transmembrane TNF. Testing in an in vitro capillary sprout formation assay, continuous endothelial activation increased angiogenesis dependent on activation of p38 MAP kinase, NADPH oxidase, and matrix metalloproteinases (MMP). p38 MAP kinase‐ and MMP‐9‐dependent angiogenesis in our assay system may be part of a positive feed forward autocrine loop because continuously activated endothelial cells displayed up‐regulated ROS production and subsequent endothelial TNF expression. The pro‐angiogenic role of the p38 MAP kinase in continuously activated endothelial cells was in stark contrast to the anti‐angiogenic activity of the p38 MAP kinase in unstimulated control endothelial cells. In vivo, using an experimental prostate tumor, pharmacological inhibition of p38 MAP kinase demonstrated a significant reduction in tumor growth and in vessel density, suggesting a pro‐angiogenic role of the p38 MAP kinase in pathological angiogenesis in vivo. In conclusion, our results suggest that continuous activation of endothelial cells can cause a switch of the p38 MAP kinase from anti‐angiogenic to pro‐angiogenic activities in conditions which link oxidative stress and autocrine TNF production. J. Cell. Physiol. 226: 800–808, 2011. © 2010 Wiley‐Liss, Inc.     

Polyethylenimine/small interfering RNA‐mediated knockdown of vascular endothelial growth factor in vivo exerts anti‐tumor effects synergistically with Bevacizumab

Background

RNA interference is a powerful method for the knockdown of pathologically relevant genes. The in vivo delivery of siRNAs, preferably through systemic, nonviral administration, poses the major challenge in the therapeutic application of RNAi. Small interfering RNA (siRNA) complexation with polyethylenimines (PEI) may represent a promising strategy for siRNA‐based therapies and, recently, the novel branched PEI F25‐LMW has been introduced in vitro. Vascular endothelial growth factor (VEGF) is frequently overexpressed in tumors and promotes tumor growth, angiogenesis and metastasis and thus represents an attractive target gene in tumor therapy.

Methods

In subcutaneous tumor xenograft mouse models, we established the therapeutic efficacy and safety of PEI F25‐LMW/siRNA‐mediated knockdown of VEGF. In biodistribution and siRNA quantification studies, we optimized administration strategies and, employing chemically modified siRNAs, compared the anti‐tumorigenic efficacies of: (i) PEI/siRNA‐mediated VEGF targeting; (ii) treatment with the monoclonal anti‐VEGF antibody Bevacizumab (Avastin®); and (iii) a combination of both.

Results

Efficient siRNA delivery is observed upon systemic administration, with the biodistribution being dependent on the mode of injection. Toxicity studies reveal no hepatotoxicity, proinflammatory cytokine induction or other side‐effects of PEI F25‐LMW/siRNA complexes or polyethylenimine, and tumor analyses show efficient VEGF knockdown upon siRNA delivery, leading to reduced tumor cell proliferation and angiogenesis. The determination of anti‐tumor effects reveals that, in pancreas carcinoma xenografts, single treatment with PEI/siRNA complexes or Bevacizumab is already highly efficacious, whereas, in prostate carcinoma, synergistic effects of both treatments are observed.

Conclusions

PEI F25‐LMW/siRNA complexes, which can be stored frozen as opposed to many other carriers, represent an efficient, safe and promising avenue in anti‐tumor therapy, and PEI/siRNA‐mediated, therapeutic VEGF knockdown exerts anti‐tumor effects. Copyright © 2010 John Wiley & Sons, Ltd.     

TRAIL/TRAIL‐R in hematologic malignancies

Defects in apoptosis are observed in many cancer cell types and contribute in a relevant way to tumorigenesis. Apoptosis is a complex and well‐regulated cell death program that plays a key role in the control of cell homeostasis, particularly at the level of the hematopoietic system. Apoptosis can be initiated through two different mechanisms involving either activation of the death receptors (extrinsic pathway) or activation of a mitochondrial apoptotic process (intrinsic pathway). Among the various death receptors a peculiar role is played by TNF‐related apoptosis‐inducing ligand (TRAIL)‐receptors (TRAIL‐Rs) and their ligand TRAIL. TRAIL recently received considerable interest for its potent anti‐tumor killing activity, sparing normal cells. Here, we will review the expression and the abnormalities of TRAIL/TRAIL‐R system in hematologic malignancies. The large majority of primary hematologic tumors are resistant to TRAIL‐mediated apoptosis, basically due to the activation of anti‐apoptotic signaling pathway (such as NF‐κB), overexpression of anti‐apoptotic proteins (such as FLIP, Bcl‐2, XIAP) or expression of TRAIL decoy receptors or reduced TRAIL‐R1/‐R2 expression. Strategies have been developed to bypass this TRAIL resistance and are based on the combination of TRAIL with chemotherapy or radiotherapy, or with proteasome or histone deacetylase or NF‐κB inhibitors. The agents used in combination with TRAIL either enhance TRAIL‐R1/‐R2 expression or decrease expression of anti‐apoptotic proteins (c‐FLIP, XIAP, Bcl‐2). Many of these combinatorial therapies hold promise for future developments in treatment of hematologic malignancies. J. Cell. Biochem. 110: 21–34, 2010. © 2010 Wiley‐Liss, Inc.     

Recombinant vascular basement membrane derived multifunctional peptide blocks endothelial cell angiogenesis and neovascularization

Angiogenesis is an innovative target in the therapy of cancer and other diseases, but the effects of anti‐angiogenic drugs have been rather modest in clinical trials. We have developed a small peptide, recombinant vascular basement membrane derived multifunctional peptide (rVBMDMP), which significantly inhibits endothelial cells in vitro. Here we test the mechanisms of rVBMDMP in angiogenesis balance in assays of tubule formation, colony formation, and apoptosis in HUVE‐12 endothelial cells. We also analyzed the differential expression of phosphorylation proteins and related genes in a protein phosphorylation chip and extracellular matrix adhesion molecule cDNA microarray, and validated changes with Western blot or real‐time quantitative PCR, respectively. rVBMDMP dose‐dependently inhibited colony formation, induced apoptosis, and inhibited in vitro tubule formation. rVBMDMP increased the phosphorylation of 88 signal proteins, including caspase‐3, death receptor 3, 4, and 5, and integrin αV, β1, and β3, and down‐regulated 41 signal proteins, including EGFR, pEGFR, VEGFR‐1, and survivin versus control. rVBMDMP upregulated 14 genes, including collagen 4, 7, and 27, and down‐regulated 21 genes, including integrin αVβ3, MMP10, and MMP12. Our study suggests that rVBMDMP inhibits angiogenesis and may be a viable drug candidate in anti‐angiogenesis and anticancer therapies. J. Cell. Biochem. 111: 453–460, 2010. © 2010 Wiley‐Liss, Inc.     

Resistance to tyrosine kinase inhibitors in clear cell renal cell carcinoma: From the patient's bed to molecular mechanisms

The introduction of anti-angiogenic drugs especially tyrosine kinase inhibitors (TKIs) was a breakthrough in the treatment of renal cell carcinoma (RCC). Although TKIs have significantly improved outcome in patients with metastatic disease, the majority still develop resistance over time. Because different combinations and sequences of TKIs are tested in clinical trials, resistance patterns and mechanisms underlying this phenomenon should be thoroughly investigated. From a clinical point of view, resistance occurs either as a primary phenomenon (intrinsic) or as a secondary phenomenon related to various escape/evasive mechanisms that the tumor develops in response to vascular endothelial growth factor (VEGF) inhibition. Intrinsic resistance is less common, and related to the primary redundancy of available angiogenic signals from the tumor, causing unresponsiveness to VEGF-targeted therapies. Acquired resistance in tumors is associated with activation of an angiogenic switch which leads to either upregulation of the existing VEGF pathway or recruitment of alternative factors responsible for tumor revascularization. Multiple mechanisms can be involved in different tumor settings that contribute both to evasive and intrinsic resistance, and current endeavor aims to identify these processes and assess their importance in clinical settings and design of pharmacological strategies that lead to enduring anti-angiogenic therapies.     

Machine-learning aided in situ drug sensitivity screening predicts treatment outcomes in ovarian PDX tumors

Long-term treatment outcomes for patients with high grade ovarian cancers have not changed despite innovations in therapies. There is no recommended assay for predicting patient response to second-line therapy, thus clinicians must make treatment decisions based on each individual patient. Patient-derived xenograft (PDX) tumors have been shown to predict drug sensitivity in ovarian cancer patients, but the time frame for intraperitoneal (IP) tumor generation, expansion, and drug screening is beyond that for tumor recurrence and platinum resistance to occur, thus results do not have clinical utility. We describe a drug sensitivity screening assay using a drug delivery microdevice implanted for 24 h in subcutaneous (SQ) ovarian PDX tumors to predict treatment outcomes in matched IP PDX tumors in a clinically relevant time frame. The SQ tumor response to local microdose drug exposure was found to be predictive of the growth of matched IP tumors after multi-week systemic therapy using significantly fewer animals (10 SQ vs 206 IP). Multiplexed immunofluorescence image analysis of phenotypic tumor response combined with a machine learning classifier could predict IP treatment outcomes against three second-line cytotoxic therapies with an average AUC of 0.91.     

Bacoside A downregulates matrix metalloproteinases 2 and 9 in DEN‐induced hepatocellular carcinoma

Cancer metastasis is a complex multi‐step process, responsible for a majority of cancer‐related deaths by affecting the critical organs and causing complications in therapies. Hepatocellular carcinoma is a multi‐factorial disease and is the third most common cause of cancer related mortality worldwide. Clinical and experimental studies have shown that MMP‐2 and MMP‐9 are involved in tumor invasion and metastases and their elevated expression has been associated with poor prognosis. Our recent studies showed a strong anti‐oxidant and hepatoprotective effects of bacoside A (BA) against carcinogen. Nevertheless the effect of BA on the activities and expression of MMP‐2 and MMP‐9 during hepatocellular carcinoma is not yet recognized. Therefore, the present study was designed to assess the same. Results of gelatin zymography study showed that BA co‐treatment significantly decreased the activities of MMP‐2 and MMP‐9, which is increased during hepatocellular carcinoma. Further immunoblot analysis showed decreased expression of MMP‐2 and MMP‐9 in rats co‐treated with BA compared to DEN‐induced hepatocellular carcinoma. Our results reveal that BA exerts its anti‐metastatic effect against DEN‐induced hepatocellular carcinoma by inhibiting the activities and expressions of MMP‐2 and MMP‐9. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects on in vitro and in vivo angiogenesis induced by small peptides carrying adhesion sequences

It is well known that tumor growth is strictly dependent on neo‐vessel formation inside the tumor mass and that cell adhesion is required to allow EC proliferation and migration inside the tumor. In this work, we have evaluated the in vitro and in vivo effects on angiogenesis of some peptides, originally designed to promote cell adhesion on biomaterials, containing RGD motif mediating cell adhesion via integrin receptors [RGD, GRGDSPK, and (GRGDSP)₄K] or the heparin‐binding sequence of human vitronectin that interacts with HSPGs [HVP(351–359)]. Cell adhesion, proliferation, migration, and capillary‐like tube formation in Matrigel were determined on HUVECs, whereas the effects on in vivo angiogenesis were evaluated using the CAM assay. (GRGDSP)₄K linear sequence inhibited cell adhesion, decreased cell proliferation, migration and morphogenesis in Matrigel, and induced anti‐angiogenic responses on CAM at higher degree than that determined after incubation with RGD or GRGDSPK. Moreover, it counteracted both in vitro and in vivo the pro‐angiogenic effects induced by the Fibroblast growth factor (FGF‐2). On the other hand, HVP was not able to affect cell adhesion and appeared less effective than (GRGDSP)₄K. Our data indicate that the activity of RGD‐containing peptides is related to their adhesive properties, and their effects are modulated by the number of cell adhesion motifs and the aminoacidic residues next to these sequences. The anti‐angiogenic properties of (GRGDSP)₄K seem to depend on its interaction with integrins, whereas the effects of HVP may be partially due to an impairment of HSPGs/FGF‐2. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Amprenavir inhibits the migration in human hepatocarcinoma cell and the growth of xenografts

The introduction of HAART (highly‐active‐antiretroviral‐therapy) has resulted in extended survival of HIV positive patients. Conversely, due to the prolonged expectancy of life and the ageing of the HIV positive population, tumors are now one of the major cause of death, and among them hepatocellular carcinoma (HCC) has become a growing concern in these patients. Considering the potential anti‐tumoral effects of HIV protease inhibitors, we decided to evaluate the anti‐tumoral activity of Amprenavir on liver carcinoma and to evaluate its potential synergistic effects in combination with standard chemoterapic drugs, such as Doxorubicin. Our results indicate that Amprenavir had direct inhibitory effects on invasion of Huh‐7 hepatocarcinoma cell lines, inhibiting MMP proteolytic activation. Amprenavir was able to delay the growth of hepatocarcinoma xenografts in nude mice and had a synergistic effect with Doxorubicin. Furthermore, Amprenavir was able to promote regression of hepatocarcinoma growth in vivo by anti‐angiogenetic and overall anti‐tumor activities, independently by PI3K/AKT related pathways that at today is one of the more suggestive hypothesis to explain the anti‐tumor effects of the different protease inhibitors. In summary these findings suggest novel anti‐neoplastic action of Amprenavir on liver cancer showing the possibility of novel combination therapies. J. Cell. Physiol. 228: 640–645, 2013. © 2012 Wiley Periodicals, Inc.     

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.     

The next‐generation BET inhibitor,PLX51107, delays melanoma growth in a CD8‐mediated manner

Epigenetic agents such as bromodomain and extra‐terminal region inhibitors (BETi) slow tumor growth via tumor intrinsic alterations; however, their effects on antitumor immunity remain unclear. A recent advance is the development of next‐generation BETi that are potent and display a favorable half‐life. Here, we tested the BETi, PLX51107, for immune‐based effects on tumor growth in BRAF V600E melanoma syngeneic models. PLX51107 delayed melanoma tumor growth and increased activated, proliferating, and functional CD8+ T cells in tumors leading to CD8+ T‐cell‐mediated tumor growth delay. PLX51107 decreased Cox2 expression, increased dendritic cells, and lowered PD‐L1, FasL, and IDO‐1 expression in the tumor microenvironment. Importantly, PLX51107 delayed the growth of tumors that progressed on anti‐PD‐1 therapy; a response associated with decreased Cox2 levels, decreased PD‐L1 expression on non‐immune cells, and increased intratumoral CD8+ T cells. Thus, next‐generation BETi represent a potential first‐line and secondary treatment strategy for metastatic melanoma by eliciting effects, at least in part, on antitumor CD8+ T cells.     

Molecular biomarker‐guided anti‐angiogenic targeted therapy for malignant glioma

Despite aggressive multimodality treatment, the prognosis of glioma, especially malignant glioma, remains very poor. After decades of effort, anti‐angiogenic therapy has become an important method of cancer treatment in addition to surgery, radiotherapy and chemotherapy. Although the performance of anti‐angiogenic therapy in colorectal cancer is good, its performance in malignant glioma remains unsatisfactory. Several phase III clinical trials showed no overall survival benefits. To solve this problem, the division of patients into groups based on their molecular biomarkers is an important step. This paper provides current insights into anti‐angiogenic drugs undergoing clinical trials and discusses the potential of molecular biomarkers to guide glioma diagnosis.     

Angiogenesis and Inflammation Signaling Are Targets of Beer Polyphenols on Vascular Cells

Emerging evidence indicates that chronic inflammation and oxidative stress cluster together with angiogenic imbalance in a wide range of pathologies. In general, natural polyphenols present health‐protective properties, which are likely attributed to their effect on oxidative stress and inflammation. Hops used in beer production are a source of polyphenols such as xanthohumol (XN), and its metabolites isoxanthohumol (IXN) and phytoestrogen 8‐prenylnaringenin (8PN). Our study aimed to evaluate XN, IXN, and 8PN effects on angiogenesis and inflammation processes. Opposite in vitro effects were observed between 8PN, stimulating endothelial and smooth muscle cell (SMC) growth, motility, invasion and capillary‐like structures formation, and XN and IXN, which inhibited them. Mouse matrigel plug and rat skin wound‐healing assays confirmed that XN and IXN treatments reduced vessel number as well as serum macrophage enzymatic activity, whereas 8PN increased blood vessels formation in both assays and enzyme activity in the wound‐healing assay. A similar profile was found for serum inflammatory interleukin‐1β quantification, in the wound‐healing assay. Our data indicate that whereas 8PN stimulates angiogenesis, XN and IXN manifested anti‐angiogenic and anti‐inflammatory effects in identical conditions. These findings suggest that the effects observed for individual compounds on vascular wall cells must be carefully taken into account, as these polyphenols are metabolized after in vivo administration. The modulation of SMC proliferation and migration is also of special relevance, given the role of these cells in many pathological conditions. Furthermore, these results may provide clues for developing useful therapeutic agents against inflammation‐ and angiogenesis‐associated pathologies. J. Cell. Biochem. 111: 1270–1279, 2010. © 2010 Wiley‐Liss, Inc.     

Low‐dose angiostatic tyrosine kinase inhibitors improve photodynamic therapy for cancer: lack of vascular normalization

Photodynamic therapy (PDT) is an effective clinical treatment for a number of different cancers. PDT can induce hypoxia and inflammation, pro‐angiogenic side effects, which may counteract its angio‐occlusive mechanism. The combination of PDT with anti‐angiogenic drugs offers a possibility for improved anti‐tumour outcome. We used two tumour models to test the effects of the clinically approved angiostatic tyrosine kinase inhibitors sunitinib, sorafenib and axitinib in combination with PDT, and compared these results with the effects of bevacizumab, the anti‐VEGF antibody, for the improvement of PDT. Best results were obtained from the combination of PDT and low‐dose axitinib or sorafenib. Molecular analysis by PCR revealed that PDT in combination with axitinib suppressed VEGFR‐2 expression in tumour vasculature. Treatment with bevacizumab, although effective as monotherapy, did not improve PDT outcome. In order to test for tumour vessel normalization effects, axitinib was also applied prior to PDT. The absence of improved PDT outcome in these experiments, as well as the lack of increased oxygenation in axitinib‐treated tumours, suggests that vascular normalization did not occur. The current data imply that there is a future for certain anti‐angiogenic agents to further improve the efficacy of photodynamic anti‐cancer therapy.     

Design of novel artemisinin‐like derivatives with cytotoxic and anti‐angiogenic properties

Artemisinins are plant products with a wide range of medicinal applications. Most prominently, artesunate is a well tolerated and effective drug for treating malaria, but is also active against several protozoal and schistosomal infections, and additionally exhibits anti‐angiogenic, anti‐tumorigenic and anti‐viral properties. The array of activities of the artemisinins, and the recent emergence of malaria resistance to artesunate, prompted us to synthesize and evaluate several novel artemisinin‐like derivatives. Sixteen distinct derivatives were therefore synthesized and the in vitro cytotoxic effects of each were tested with different cell lines. The in vivo anti‐angiogenic properties were evaluated using a zebrafish embryo model. We herein report the identification of several novel artemisinin‐like compounds that are easily synthesized, stable at room temperature, may overcome drug‐resistance pathways and are more active in vitro and in vivo than the commonly used artesunate. These promising findings raise the hopes of identifying safer and more effective strategies to treat a range of infections and cancer.     

Differential remodeling of extracellular matrices by breast cancer initiating cells

Cancer initiating cells (CICs) have been the focus of recent anti‐cancer therapies, exhibiting strong invasion capability via potentially enhanced ability to remodel extracellular matrices (ECM). We have identified CICs in a human breast cancer cell line, MX‐1, and developed a xenograft model in SCID mice. We investigated the CICs' matrix‐remodeling effects using Second Harmonic Generation (SHG) microscopy to identify potential phenotypic signatures of the CIC‐rich tumors. The isolated CICs exhibit higher proliferation, drug efflux and drug resistant properties in vitro; were more tumorigenic than non‐CICs, resulting in more and larger tumors in the xenograft model. The CIC‐rich tumors have less collagen in the tumor interior than in the CIC‐poor tumors supporting the idea that the CICs can remodel the collagen more effectively. The collagen fibers were preferentially aligned perpendicular to the CIC‐rich tumor boundary while parallel to the CIC‐poor tumor boundary suggesting more invasive behavior of the CIC‐rich tumors. These findings would provide potential translational values in quantifying and monitoring CIC‐rich tumors in future anti‐cancer therapies.

CIC‐rich tumors remodel the collagen matrix more than CIC‐poor tumors.     

Anti-tumour and anti-angiogenetic effects of zoledronic acid on human non-small-cell lung cancer cell line

Objectives: Although emerging data suggest that zoledronic acid (Zol) may have different anti‐tumour activities against a broad range of cancers, its effects on lung cancer remain largely unknown. The aim of this study was to evaluate in vitro the anti‐tumoural and anti‐angiogenetic effect of zoledronic acid in non‐small‐cell lung cancer (NSCLC) cells. Material and methods: We treated A549 NSCLC cells with zoledronic acid to investigate survival, cell cycle activity, anti‐angiogenic activity and apoptotic responses to it. Results: We observed that highest Zol concentration (100 μm ) caused arrest in G1 phase of the cell cycle and also induced different percentages of apoptosis in presence (0.9% versus 4.4%) or absence (2.4% versus 28.5%) of serum (P = 0.0001). Zol concentration from 5 to 100 μm for 2 days induced significant concentration‐dependent cell death in adherent cells. Furthermore, Zol (10–100 μm ) induced dose‐dependent reduction both of mRNA and protein expression of VEGF associated with parallel decrease in VEGF secretion in the culture medium. Conclusion: Taken together, these results support a possible anti‐cancer and anti‐angiogenetic activity of Zol. Our data may not only provide a basis for the clinical use of this drug as preventive agent of bone metastases but also suggest that Zol deserves attention as an anti‐cancer agent in non‐small‐cell lung cancer.     

Redesigning of anti‐c‐Met single chain Fv antibody for the cytoplasmic folding and its structural analysis

Typically, single chain Fv antibodies are unable to fold properly under a reducing cytoplasm because of the reduction of disulfide bonds. The inability to fold limits both the production of the functional scFvs and their targeting against antigens, which are generally executed in a reducing cytoplasm. In this study, the target scFv CDR was grafted with stable human consensus framework sequences, which enabled the generation of a foldable scFv in a reducing cytoplasm of Escherichia coli. Additionally, the structural features affecting the folding efficiency of the engineered scFv were identified by analyzing the predicted structure. An anti‐c‐Met scFv, which was a cytoplasmic non‐foldable protein, was redesigned as the model system. This study confirmed that the engineered anti‐c‐Met scFv was folded into its native form in the cytoplasm of E. coli BL21(DE3) without a significant loss in the specific binding activity against c‐Met antigen. The structures of the wild‐type anti‐c‐Met scFv and the engineered scFv were predicted using homology modeling. A comparative analysis based on the sequence and structure showed that the hydrophobicity of 12 solvent exposed residues decreased, and two newly formed salt bridges might have improved the folding efficiency of the engineered scFv under the reducing condition. Biotechnol. Bioeng. 2010; 106: 367–375. © 2010 Wiley Periodicals, Inc.