Automated SEM/EDS analysis for assessment of trace cross-contamination in 316L stainless steel powders

Following observations of microcracking in two, out of three, Additive manufactured (AM) 316L steel samples, an investigation was undertaken to ascertain the root cause. Welding diagrams, taking into account composition and process parameters, could not generally account for the experimental observations of non-cracked versus cracked AM 316L samples. EBSD phase maps in all three AM samples exhibited a fully austenitic microstructure not only in the bulk sample but also near-surface. Analysis of microcracked regions in the AM samples showed the presence of local enrichment of Ni, Cu and P. Automated SEM/EDS analysis on feedstock powder samples prepared for cross-section examination revealed a fine, foreign particulate contaminant, expected to arise from NiCrCuP alloy cross-contamination during atomization, to be completely embedded in a 316L powder particle. This type of contamination would not have been revealed on examination of powder mounted onto a SEM stub, a common approach to assess powder quality. Based on this analysis, it is recommended to consider including automated SEM/EDS analysis on powder cross-sections in any standardization protocol for quality control of powders, to increase the chances of detection and identification of fine cross-contaminants. It is also recommended that atomization of NiCrCuP alloy should no longer precede atomization of 316L alloy

Surface Modification of Polypropilene Non-woven Substrates by Padding with Antistatic Agents for Deposition of Polyvinyl Alcohol (PVA) Nanofiber Webs by Electrospinning

In recent years, the electrospinning process has become one of the most interesting processes to obtain nanofiber webs with interesting properties for uses in a wide variety of industrial sectors such as filtration, chemical barriers, medical devices, etc., as a consequence of the relatively high surface-to-volume ratio. Among the wide variety of polymers, polyvinyl alcohol (PVA) offers good advantages since it is water-soluble and this fact enables easy processing by electrospinning. There are many variables and parameters to be considered in order to optimize PVA nanofiber webs: some of them are related to the polymer solution, some others are related to the process, and some of them are related to the collector substrate. In this work a study on the effects of two different surface pre-treatments on a nonwoven polypropylene substrate as a collector of PVA nanofiber webs has been carried out. In particular, a chemical treatment with anionic antistatics and a physical treatment with lowpressure plasma have been investigated. The effects of these pre-treatments on morphology of PVA nanofiber webs have been evaluated by scanning electron microscopy. Results show that surface resistivity is one of the main parameters influencing the web formation as well as the nature of the electric charge achieved by the pre-treatment. The plasma treatment promotes changes in surface resistivity but it is not enough for good web deposition. Chemical pre-treatment (padding) with anionic antistatic leads to a decrease in surface resistivity up to values in the 1 × 109– 1 × 1011 Ω which is enough for good nanofiber deposition.This work was supported by the Ministerio de Ciencia y Tecnologia, grant number DPI2007-66849-C02-02.Blanes, M.; Marco, B.; Gisbert, MJ.; Bonet Aracil, MA.; Balart Gimeno, RA. (2010). Surface Modification of Polypropilene Non-woven Substrates by Padding with Antistatic Agents for Deposition of Polyvinyl Alcohol (PVA) Nanofiber Webs by Electrospinning. Textile Research Journal. 80(13):1335-1346. https://doi.org/10.1177/0040517509358801S133513468013Burger, C., Hsiao, B. S., & Chu, B. (2006). NANOFIBROUS MATERIALS AND THEIR APPLICATIONS. Annual Review of Materials Research, 36(1), 333-368. doi:10.1146/annurev.matsci.36.011205.123537Dersch, R., Steinhart, M., Boudriot, U., Greiner, A., & Wendorff, J. H. (2005). Nanoprocessing of polymers: applications in medicine, sensors, catalysis, photonics. Polymers for Advanced Technologies, 16(2-3), 276-282. doi:10.1002/pat.568Frenot, A., & Chronakis, I. S. (2003). Polymer nanofibers assembled by electrospinning. Current Opinion in Colloid & Interface Science, 8(1), 64-75. doi:10.1016/s1359-0294(03)00004-9GOPAL, R., KAUR, S., MA, Z., CHAN, C., RAMAKRISHNA, S., & MATSUURA, T. (2006). Electrospun nanofibrous filtration membrane. Journal of Membrane Science, 281(1-2), 581-586. doi:10.1016/j.memsci.2006.04.026Qin, X.-H., & Wang, S.-Y. (2006). Filtration properties of electrospinning nanofibers. Journal of Applied Polymer Science, 102(2), 1285-1290. doi:10.1002/app.24361Ren, G., Xu, X., Liu, Q., Cheng, J., Yuan, X., Wu, L., & Wan, Y. (2006). Electrospun poly(vinyl alcohol)/glucose oxidase biocomposite membranes for biosensor applications. Reactive and Functional Polymers, 66(12), 1559-1564. doi:10.1016/j.reactfunctpolym.2006.05.005Lee, S., & Obendorf, S. K. (2007). Use of Electrospun Nanofiber Web for Protective Textile Materials as Barriers to Liquid Penetration. Textile Research Journal, 77(9), 696-702. doi:10.1177/0040517507080284Heikkilä, P., Sipilä, A., Peltola, M., Harlin, A., & Taipale, A. (2007). Electrospun PA-66 Coating on Textile Surfaces. Textile Research Journal, 77(11), 864-870. doi:10.1177/0040517507078241Boudriot, U., Dersch, R., Greiner, A., & Wendorff, J. H. (2006). Electrospinning Approaches Toward Scaffold Engineering?A Brief Overview. Artificial Organs, 30(10), 785-792. doi:10.1111/j.1525-1594.2006.00301.xButtafoco, L., Kolkman, N. G., Engbers-Buijtenhuijs, P., Poot, A. A., Dijkstra, P. J., Vermes, I., & Feijen, J. (2006). Electrospinning of collagen and elastin for tissue engineering applications. Biomaterials, 27(5), 724-734. doi:10.1016/j.biomaterials.2005.06.024Lee, L. J. (2006). Polymer Nanoengineering for Biomedical Applications. Annals of Biomedical Engineering, 34(1), 75-88. doi:10.1007/s10439-005-9011-6Chew, S. Y., Hufnagel, T. C., Lim, C. T., & Leong, K. W. (2006). Mechanical properties of single electrospun drug-encapsulated nanofibres. Nanotechnology, 17(15), 3880-3891. doi:10.1088/0957-4484/17/15/045Huang, Z.-M., He, C.-L., Yang, A., Zhang, Y., Han, X.-J., Yin, J., & Wu, Q. (2006). Encapsulating drugs in biodegradable ultrafine fibers through co-axial electrospinning. Journal of Biomedical Materials Research Part A, 77A(1), 169-179. doi:10.1002/jbm.a.30564Kim, H.-W., Lee, H.-H., & Knowles, J. C. (2006). Electrospinning biomedical nanocomposite fibers of hydroxyapatite/poly(lactic acid) for bone regeneration. Journal of Biomedical Materials Research Part A, 79A(3), 643-649. doi:10.1002/jbm.a.30866Taepaiboon, P., Rungsardthong, U., & Supaphol, P. (2006). Drug-loaded electrospun mats of poly(vinyl alcohol) fibres and their release characteristics of four model drugs. Nanotechnology, 17(9), 2317-2329. doi:10.1088/0957-4484/17/9/041Ding, B., Kim, H.-Y., Lee, S.-C., Shao, C.-L., Lee, D.-R., Park, S.-J., … Choi, K.-J. (2002). Preparation and characterization of a nanoscale poly(vinyl alcohol) fiber aggregate produced by an electrospinning method. Journal of Polymer Science Part B: Polymer Physics, 40(13), 1261-1268. doi:10.1002/polb.10191Cui, W., Li, X., Zhou, S., & Weng, J. (2006). Investigation on process parameters of electrospinning system through orthogonal experimental design. Journal of Applied Polymer Science, 103(5), 3105-3112. doi:10.1002/app.25464Deitzel, J. ., Kleinmeyer, J., Harris, D., & Beck Tan, N. . (2001). The effect of processing variables on the morphology of electrospun nanofibers and textiles. Polymer, 42(1), 261-272. doi:10.1016/s0032-3861(00)00250-0Lyons, J., Li, C., & Ko, F. (2004). Melt-electrospinning part I: processing parameters and geometric properties. Polymer, 45(22), 7597-7603. doi:10.1016/j.polymer.2004.08.071Theron, S. A., Zussman, E., & Yarin, A. L. (2004). Experimental investigation of the governing parameters in the electrospinning of polymer solutions. Polymer, 45(6), 2017-2030. doi:10.1016/j.polymer.2004.01.024Kilic, A., Oruc, F., & Demir, A. (2008). Effects of Polarity on Electrospinning Process. Textile Research Journal, 78(6), 532-539. doi:10.1177/0040517507081296Reneker, D. H., & Chun, I. (1996). Nanometre diameter fibres of polymer, produced by electrospinning. Nanotechnology, 7(3), 216-223. doi:10.1088/0957-4484/7/3/009Lee, J. S., Choi, K. H., Ghim, H. D., Kim, S. S., Chun, D. H., Kim, H. Y., & Lyoo, W. S. (2004). Role of molecular weight of atactic poly(vinyl alcohol) (PVA) in the structure and properties of PVA nanofabric prepared by electrospinning. Journal of Applied Polymer Science, 93(4), 1638-1646. doi:10.1002/app.20602Mit-uppatham, C., Nithitanakul, M., & Supaphol, P. (2004). Effects of Solution Concentration, Emitting Electrode Polarity, Solvent Type, and Salt Addition on Electrospun Polyamide-6 Fibers: A Preliminary Report. Macromolecular Symposia, 216(1), 293-300. doi:10.1002/masy.200451227Kim, S. J., Lee, C. K., & Kim, S. I. (2005). Effect of ionic salts on the processing of poly(2-acrylamido-2-methyl-1-propane sulfonic acid) nanofibers. Journal of Applied Polymer Science, 96(4), 1388-1393. doi:10.1002/app.21567ZHANG, C., YUAN, X., WU, L., & SHENG, J. (2006). PROPERTIES OF ULTRAFINE FIBROUS POLY(VINYL ALCOHOL) MEMBRANES BY ELECTROSPINNING. Acta Polymerica Sinica, 006(2), 294-297. doi:10.3724/sp.j.1105.2006.00294Supaphol, P., & Chuangchote, S. (2008). On the electrospinning of poly(vinyl alcohol) nanofiber mats: A revisit. Journal of Applied Polymer Science, 108(2), 969-978. doi:10.1002/app.27664Jones, R. N. (1962). THE EFFECTS OF CHAIN LENGTH ON THE INFRARED SPECTRA OF FATTY ACIDS AND METHYL ESTERS. Canadian Journal of Chemistry, 40(2), 321-333. doi:10.1139/v62-050Yao, L., Haas, T. W., Guiseppi-Elie, A., Bowlin, G. L., Simpson, D. G., & Wnek, G. E. (2003). Electrospinning and Stabilization of Fully Hydrolyzed Poly(Vinyl Alcohol) Fibers. Chemistry of Materials, 15(9), 1860-1864. doi:10.1021/cm0210795Wei, Q. F., Gao, W. D., Hou, D. Y., & Wang, X. Q. (2005). Surface modification of polymer nanofibres by plasma treatment. Applied Surface Science, 245(1-4), 16-20. doi:10.1016/j.apsusc.2004.10.013Garcia, D., Sanchez, L., Fenollar, O., Lopez, R., & Balart, R. (2008). Modification of polypropylene surface by CH4–O2 low-pressure plasma to improve wettability. Journal of Materials Science, 43(10), 3466-3473. doi:10.1007/s10853-007-2322-2López, R., Sanchis, R., García, D., Fenollar, O., & Balart, R. (2009). Surface characterization of hydrophilic coating obtained by low-pressure CH4O2plasma treatment on a polypropylene film. Journal of Applied Polymer Science, 111(6), 2992-2997. doi:10.1002/app.29324Tsai, P. P., Schreuder-Gibson, H., & Gibson, P. (2002). Different electrostatic methods for making electret filters. Journal of Electrostatics, 54(3-4), 333-341. doi:10.1016/s0304-3886(01)00160-

Properties of composite laminates based on basalt fibers with epoxidized vegetable oils

This paper deals with the development of polymeric materials derived from epoxidized vegetable oils which have been used in the manufacture of laminated composite materials with basalt fabrics. Epoxidized linseed oil (ELO) and epoxidized soybean oil (ESBO) were used as biobased matrices. The basalt fabrics were modified with amino-silane and glycidyl-silane to increase fiber-matrix interactions. The curing behaviour of both resins was evaluated by differential scanning calorimetry (DSC) and oscillatory rheometry (OR). The evaluation of mechanical properties was made by tensile, flexural and Charpy tests. The extent of the fiber-matrix interactions among interface was evaluated by scanning electron microscopy (SEM). The obtained results revealed that surface modification of basalt fibers with glycidyl-silane clearly improves the mechanical properties of the composites. The use of the ELO resin as matrix for composite laminates improved substantially the mechanical performance compared to composites made with ESBO. (C) 2015 Elsevier Ltd. All rights reserved.This study was funded by the "Conselleria d'Educacio, Cultura i Esport" - Generalitat Valenciana (reference number: GV/2014/008).Samper Madrigal, MD.; Petrucci, R.; Sánchez Nacher, L.; Balart Gimeno, RA.; Kenny, JM. (2015). Properties of composite laminates based on basalt fibers with epoxidized vegetable oils. Materials and Design. 72:9-15. doi:10.1016/j.matdes.2015.02.002S9157

New environmentally friendly composite laminates with epoxidized linseed oil (ELO) and slate fiber fabrics

This work focuses on the development of new composite laminates based on the use of epoxidized linseed oil (ELO) as matrix and reinforcement fabrics from slate fibers with different silane treatments. The curing behavior of the ELO resin is followed by differential scanning calorimetry (DSC) and the gelation is studied by oscillatory rheometry and gel-time. Composite laminates of ELO matrix and slate fabrics are manufactured by Rein Transfer Molding (RTM) and the mechanical properties of the composite laminates are tested in tensile, flexural and impact conditions. The effects of different silane coupling agents on fiber-matrix interface phenomena are studied by scanning electron microscopy (SEM). As in other siliceous fibers, silane treatment leads to improved mechanical performance but glycidyl silane treatment produces the optimum results as the interactions between silanized slate fiber and epoxidized linseed oil are remarkably improved as observed by scanning electron microscopy (SEM). (C) 2014 Elsevier Ltd. All rights reserved.This study has been funded by the "Conselleria d'Educacio, Cultura i Esport" - Generalitat Valenciana (reference number: GV/2014/008). Authors thank Microscopy Services at UPV for helping in using SEM technique.Samper Madrigal, MD.; Petrucci, R.; Sánchez Nacher, L.; Balart Gimeno, RA.; Kenny, JM. (2015). New environmentally friendly composite laminates with epoxidized linseed oil (ELO) and slate fiber fabrics. Composites Part B: Engineering. 71:203-209. https://doi.org/10.1016/j.compositesb.2014.11.0342032097

The role of dilute solute additions on growth restriction in Cu-, Al-, Mg- and Ti-based alloys

The effect of dilute solute additions on growth restriction in Cu-, Al-, Mg- and Ti-based binary and ternary alloys was assessed by means of the heuristic growth restriction parameter (β) modelling framework. The CALPHAD (calculation of phase diagrams) methodology was used to calculate β values from the m and k values, at first approximation, as well as from the liquid-to-solid fraction to obtain true β values. Grain size values from the literature were plotted against the corresponding true β values, showing a negative or inverse correlation between the two

The effect of sepiolite on the compatibilization of polyethylene thermoplastic starch blends for environmentally friendly films

The final publication is available at Springer via http://dx.doi.org/10.1007/s10853-014-8647-8[EN] Green polyethylene is a new and attracting polymer from biobased resources (sugarcane) and identical properties to petroleum-based polyethylene. Its potential in the packaging industry is really promising. In this work, we report the use of different compatibilizer systems for green polyethylene (from sugarcane) and thermoplastic starch (30 wt% TPS) in order to increase ductile mechanical properties and biodegradable content. Typical petroleum-based graft copolymer of polyethylene with maleic anhydride (PE-g-MA) is used as reference compatibilizer, and new compatibilizer systems are developed using sepiolite. The obtained results show that sepiolite-based compatibilizers provide good compatibilization properties as observed by a remarkable increase in elongation at break and a noticeable size reduction of the TPS domains dispersed in the green polyethylene matrix as observed by scanning electron microscopy (SEM).This study has been funded by the ‘‘Conselleria d’Educacio´, Cultura i Esport’’—Generalitat Valenciana (Reference number: GV/2014/008). Authors thank Tolsa S.A for kindly supply sepiolite for this study and Microscopy Services at UPV for helping in using SEM and TEM techniques.Samper Madrigal, MD.; Fenollar Gimeno, OÁ.; Dominici, F.; Balart Gimeno, RA.; Kenny, JM. (2015). The effect of sepiolite on the compatibilization of polyethylene thermoplastic starch blends for environmentally friendly films. Journal of Materials Science. 50(2):863-872. https://doi.org/10.1007/s10853-014-8647-8S863872502Alvarenga RAF, Dewulf J (2013) Plastic vs. fuel: Which use of the Brazilian ethanol Can bring more environmental gains? Renew Energ 59:49–52Kikuchi Y, Hirao M, Narita K, Sugiyama E, Oliveira S, Chapman S, Arakaki MM, Cappra CM (2013) Environmental performance of biomass-derived chemical production: a case study on sugarcane-derived polyethylene. J Chem Eng Jpn 46:319–325Liptow C, Tillman A-M (2012) A comparative Life Cycle Assessment Study of polyethylene based on sugarcane and crude oil. J Ind Ecol 16:420–435Taghizadeh A, Sarazin P, Favis BD (2013) High molecular weight plasticizers in thermoplastic starch/polyethylene blends. J Mater Sci 48:1799–1811. doi: 10.1007/s10853-012-6943-8Park HM, Lee WK, Park CY, Cho WJ, Ha CS (2003) Environmentally friendly polymer hybrids—Part I—Mechanical, thermal, and barrier properties of thermoplastic starch/clay nanocomposites. J Mater Sci 38:909–915. doi: 10.1023/A:1022308705231Pimentel TAPF, Duraes JA, Drummond AL, Schlemmer D, Falcao R, Araujo Sales MJ (2007) Preparation and characterization of blends of recycled polystyrene with cassava starch. J Mater Sci 42:7530–7536. doi: 10.1007/s10853-007-1622-xRosa DS, Guedes CGF, Carvalho CL (2007) Processing and thermal, mechanical and morphological characterization of post-consumer polyolefins/thermoplastic starch blends. J Mater Sci 42:551–557. doi: 10.1007/s10853-006-1049-9Kaseem M, Hamad K, Deri F (2012) Thermoplastic starch blends: a review of recent works. Polym Sci Ser A 54:165–176Nafchi AM, Moradpour M, Saeidi M, Alias AK (2013) Thermoplastic starches: properties, challenges, and prospects. Starch-Starke 65:61–72Jimenez A, Jose Fabra M, Talens P, Chiralt A (2012) Edible and biodegradable starch films: a review. Food Bioprocess Tech 5:2058–2076Bikiaris D, Panayiotou C (1998) LDPE/starch blends compatibilized with PE-g-MA copolymers. J Appl Polym Sci 70:1503–1521Liu W, Wang YJ, Sun Z (2003) Effects of polyethylene-grafted maleic anhydride (PE-g-MA) on thermal properties, morphology, and tensile properties of low-density polyethylene (LDPE) and corn starch blends. J Appl Polym Sci 88:2904–2911Pedroso AG, Rosa DS (2005) Mechanical, thermal and morphological characterization of recycled LDPE/corn starch blends. Carbohyd Polym 59:1–9Rodriguez-Gonzalez FJ, Ramsay BA, Favis BD (2003) High performance LDPE/thermoplastic starch blends: a sustainable alternative to pure polyethylene. Polymer 44:1517–1526Yang L, Liu W (2010) Effects of functional groups of starch on asa emulsification and sizing. In: Sun RC, Fu SY (eds) Research progress in paper industry and biorefinery. China University of Technology Press, Guangzhou, pp 1936–1939Kapusniak J, Jochym K, Bajer K, Bajer D (2011) Review of methods for chemical modification of starch. Przem Chem 90:1521–1526Ren L, Jiang M, Tong J, Bai X, Dong X, Zhou J (2010) Influence of surface esterification with alkenyl succinic anhydrides on mechanical properties of corn starch films. Carbohyd Polym 82:1010–1013Cunha AG, Gandini A (2010) Turning polysaccharides into hydrophobic materials: a critical review. Part 2. Hemicelluloses, chitin/chitosan, starch, pectin and alginates. Cellulose 17:1045–1065Bhattacharya M (1998) Stress relaxation of starch synthetic polymer blends. J Mater Sci 33:4131–4139. doi: 10.1023/A:1004449002240Sam ST, Ismail H, Ahmad Z (2011) Soil burial of polyethylene-g-(maleic anhydride) compatibilised LLDPE/soya powder blends. Polym-Plast Technol 50:851–861Majid RA, Ismail H, Taib RM (2009) Effects of PE-g-MA on tensile properties, morphology and water absorption of LDPE/thermoplastic sago starch blends. Polym-Plast Technol 48:919–924Kahar M, Wahab A, Ismail H, Othman N (2012) Compatibilization effects of PE-g-MA on mechanical, thermal and swelling properties of high density polyethylene/natural rubber/thermoplastic tapioca starch blends. Polym-Plast Technol 51:298–303Xu Y, Thurber CM, Lodge TP, Hillmyer MA (2012) Synthesis and remarkable efficacy of model polyethylene-graft-poly(methyl methacrylate) copolymers as compatibilizers in polyethylene/poly(methyl methacrylate) blends. Macromolecules 45:9604–9610Wang N, Yu J, Ma X, Wu Y (2007) The influence of citric acid on the properties of thermoplastic starch/linear low-density polyethylene blends. Carbohyd Polym 67:446–453Kim JP, Yoon TH, Mun SP, Rhee JM, Lee JS (2006) Wood-polyethylene composites using ethylene-vinyl alcohol copolymer as adhesion promoter. Bioresource Technol 97:494–499Choudhury A, Mukherjee M, Adhikari B (2006) Recycling of polyethylene/nylon 6 based waste oil pouches using compatibilizer. 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Influence of glyoxal in the physical characterization of PVA nanofibres

[EN] The influence of solution composition is directly related to the properties of polyvinyl alcohol (PVA) nanofibers. Electrospinning is a viable technique to develop PVA nanofibers. The presence of a crosslinking agent such as glyoxal can produce variations not only in anti-water solubility effect, but also in the morphology of the electrodeposited fibers. The objective of this study was to characterize the influence of glyoxal on PVA nanofibers. Thus, we studied fiber dimensions, the weight of deposited fibers, and fiber crystallinity. The relation between those properties and the properties of the nanofiber web (color, opacity, and roughness) were studied. In this study we changed glyoxal concentration. Scanning electron microscopy, differential scanning calorimetry, and atomic force microscopy showed changes in the fiber properties. We could observe how the diameter fiber increased, the collector surface was widely covered, and the fiber crystallinity decreased. Regarding the properties of the web, the roughness decreased and the color turned whiter.The authors wish to acknowledge the financial support of the MINISTERIO DE CIENCIA E INNOVACION. Ref: CIT-020000-2008-016 for financial support. Also, the microscopy services at UPV are gratefully acknowledged for their assistance in using AFM techniques, and Octavio Fenollar at UPV is gratefully acknowledged for his assistance in using calorimetric techniques.Blanes, M.; Gisbert, MJ.; Marco, B.; Bonet Aracil, MA.; Gisbert Paya, J.; Balart Gimeno, RA. (2010). Influence of glyoxal in the physical characterization of PVA nanofibres. Textile Research Journal. 80(14):1465-1472. doi:10.1177/0040517509357654S14651472801

Solute effects on growth restriction in dilute ferrous alloys

The effect of dilute solute additions on growth restriction in binary ferrous alloys has been assessed by means of the heuristic growth restriction parameter (β) modelling framework (Fan et al. in Acta Mater. 152, 248–257, 2018). The CALPHAD (CALculation of PHAse Diagrams) methodology (Kaufman and Bernstein in Computer Calculation of Phase Diagrams, 1970) has been used to calculate β values from the liquidus slope m and the equilibrium distribution coefficient k values, at first approximation, in conjunction with the liquid-to-solid fraction to obtain true β values. Critical solute concentrations, below which solidification becomes partitionless, have also been calculated. Among 23 dilute binary ferrous alloy systems investigated, the five most efficient solutes on grain refinement are B, Y, O, S and C. A negative correlation, or inverse relationship, was observed between the true β values and the grain size values obtained from a study on experimental multicomponent dilute ferrous alloy systems (Li et al. in Metall. Mater. Trans. A 49 A, 2235–2247, 2018)

VAV3 mediates resistance to breast cancer endocrine therapy

Introduction: Endocrine therapies targeting cell proliferation and survival mediated by estrogen receptor α (ERα) are among the most effective systemic treatments for ERα-positive breast cancer. However, most tumors initially responsive to these therapies acquire resistance through mechanisms that involve ERα transcriptional regulatory plasticity. Herein we identify VAV3 as a critical component in this process. Methods: A cell-based chemical compound screen was carried out to identify therapeutic strategies against resistance to endocrine therapy. Binding to ERα was evaluated by molecular docking analyses, an agonist fluoligand assay and short hairpin (sh)RNA–mediated protein depletion. Microarray analyses were performed to identify altered gene expression. Western blot analysis of signaling and proliferation markers, and shRNA-mediated protein depletion in viability and clonogenic assays, were performed to delineate the role of VAV3. Genetic variation in VAV3 was assessed for association with the response to tamoxifen. Immunohistochemical analyses of VAV3 were carried out to determine its association with therapeutic response and different tumor markers. An analysis of gene expression association with drug sensitivity was carried out to identify a potential therapeutic approach based on differential VAV3 expression. Results: The compound YC-1 was found to comparatively reduce the viability of cell models of acquired resistance. This effect was probably not due to activation of its canonical target (soluble guanylyl cyclase), but instead was likely a result of binding to ERα. VAV3 was selectively reduced upon exposure to YC-1 or ERα depletion, and, accordingly, VAV3 depletion comparatively reduced the viability of cell models of acquired resistance. In the clinical scenario, germline variation in VAV3 was associated with the response to tamoxifen in Japanese breast cancer patients (rs10494071 combined P value = 8.4 × 10−4). The allele association combined with gene expression analyses indicated that low VAV3 expression predicts better clinical outcome. Conversely, high nuclear VAV3 expression in tumor cells was associated with poorer endocrine therapy response. Based on VAV3 expression levels and the response to erlotinib in cancer cell lines, targeting EGFR signaling may be a promising therapeutic strategy. Conclusions: This study proposes VAV3 as a biomarker and a rationale for its use as a signaling target to prevent and/or overcome resistance to endocrine therapy in breast cancer.This work was supported by grants from the Eugenio Rodríguez Pascual Foundation (2012, to MAP), the Government of Catalonia (2009-SGR283, to AV and MAP), the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (R01 DK015556, to JAK), the Red Cooperative Research Thematic Network on Cancer (RTICC) (12/0036/0002 to XRB and 12/0036/0008 to XRB and MAP) and the Spanish Ministry of Health, Fund for Health Research–Institute of Health Carlos III (11/00951 to AU and 12/01528 to MAP