Defining the landscape of circRNAs in non-small cell lung cancer and their potential as liquid biopsy biomarkers: a complete review including current methods

Abstract

Despite the significant decrease in population-level mortality of lung cancer patients as reflected in the Surveillance Epidemiology and End Results program national database, lung cancer, with non-small cell lung cancer (NSCLC) in the lead, continues to be the most commonly diagnosed cancer and foremost cause of cancer-related death worldwide, primarily due to late-stage diagnosis and ineffective treatment regimens. Although innovative single therapies and their combinations are constantly being tested in clinical trials, the five-year survival rate of late-stage lung cancer remains only 5% (Cancer Research, UK). Henceforth, investigation in the early diagnosis of lung cancer and prediction of treatment response is critical for improving the overall survival of these patients. Circular RNAs (circRNAs) are a re-discovered type of RNAs featuring stable structure and high tissue-specific expression. Evidence has revealed that aberrant circRNA expression plays an important role in carcinogenesis and tumor progression. Further investigation is warranted to assess the value of EV- and platelet-derived circRNAs as liquid biopsy-based readouts for lung cancer detection. This review discusses the origin and biology of circRNAs, and analyzes their present landscape in NSCLC, focusing on liquid biopsies to illustrate the different methodological trends currently available in research. The possible limitations that could be holding back the clinical implementation of circRNAs are also analyzed.

Keywords

CircRNA / extracellular vesicles lung cancer / NSCLC / liquid biopsies / biomarkers

References

[1] Bray F,Soerjomataram I,Torre LA.Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.CA Cancer J Clin2018;68:394-424

[2] Howlader N,Mooradian MJ.The effect of advances in lung-cancer treatment on population mortality.N Engl J Med2020;383:640-9

[3] Bracht JWP,Berenguer J,Rosell R.The present and future of liquid biopsies in non-small cell lung cancer: combining four biosources for diagnosis, prognosis, prediction, and disease monitoring.Curr Oncol Rep2018;20:70

[4] Siravegna G,Siena S.Integrating liquid biopsies into the management of cancer.Nat Rev Clin Oncol2017;14:531-48

[5] He X,Chen Y.Extracellular vesicle-associated miRNAs as a biomarker for lung cancer in liquid biopsy.Front Mol Biosci2021;8:630718 PMCID:PMC7943919

[6] Müller Bark J, Kulasinghe A, Amenábar JM, Punyadeera C. Exosomes in cancer. Elsevier; 2021. pp. 1-40.

[7] Pinzani P,Del Re M.Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors.Clin Chem Lab Med2021;

[8] Tang X,Guo M,Yang Y.Review on circular RNAs and new insights into their roles in cancer.Comput Struct Biotechnol J2021;19:910-28 PMCID:PMC7851342

[9] Salzman J,Wang PL,Brown PO.Circular RNAs are the predominant transcript isoform from hundreds of human genes in diverse cell types.PLoS One2012;7:e30733 PMCID:PMC3270023

[10] Hua X,Chen J.Circular RNAs in drug resistant tumors.Biomed Pharmacother2019;118:109233

[11] Nigro JM,Fearon ER.Scrambled exons.Cell1991;64:607-13

[12] Lee ECS,Lim GPL.The roles of circular RNAs in human development and diseases.Biomed Pharmacother2019;111:198-208

[13] Ji P,Chen S.Expanded expression landscape and prioritization of circular RNAs in mammals.Cell Rep2019;26:3444-3460.e5

[14] Guo JU,Guo H.Expanded identification and characterization of mammalian circular RNAs.Genome Biol2014;15:409 PMCID:PMC4165365

[15] Salzman J,Olsen MN,Brown PO.Cell-type specific features of circular RNA expression.PLoS Genet2013;9:e1003777 PMCID:PMC3764148

[16] Dragomir M.Circular RNAs in cancer - lessons learned from microRNAs.Front Oncol2018;8:179 PMCID:PMC5992376

[17] Xiao MS,Wilusz JE.Biogenesis and functions of circular RNAs come into focus.Trends Cell Biol2020;30:226-40 PMCID:PMC7069689

[18] Chen CY.Initiation of protein synthesis by the eukaryotic translational apparatus on circular RNAs.Science1995;268:415-7

[19] Rybak-Wolf A,Glažar P.Circular RNAs in the mammalian brain are highly abundant, conserved, and dynamically expressed.Mol Cell2015;58:870-85

[20] Li X,Xue W.Coordinated circRNA biogenesis and function with NF90/NF110 in viral infection.Mol Cell2017;67:214-227.e7

[21] Ashwal-Fluss R,Pamudurti NR.circRNA biogenesis competes with pre-mRNA splicing.Mol Cell2014;56:55-66

[22] Fei T,Xiao T.Genome-wide CRISPR screen identifies HNRNPL as a prostate cancer dependency regulating RNA splicing.Proc Natl Acad Sci U S A2017;114:E5207-15 PMCID:PMC5495225

[23] Errichelli L,Laneve P.FUS affects circular RNA expression in murine embryonic stem cell-derived motor neurons.Nat Commun2017;8:14741 PMCID:PMC5379105

[24] Conn SJ,Toubia J.The RNA binding protein quaking regulates formation of circRNAs.Cell2015;160:1125-34

[25] Aktaş T,Maticzka D.DHX9 suppresses RNA processing defects originating from the Alu invasion of the human genome.Nature2017;544:115-9

[26] Khan MA,Aufiero S.RBM20 regulates circular RNA production from the Titin gene.Circ Res2016;119:996-1003

[27] Jeck WR,Wang K.Circular RNAs are abundant, conserved, and associated with ALU repeats.RNA2013;19:141-57 PMCID:PMC3543092

[28] Huang C,Tatomer DC.A length-dependent evolutionarily conserved pathway controls nuclear export of circular RNAs.Genes Dev2018;32:639-44 PMCID:PMC6004072

[29] Hansen TB,Bramsen JB.miRNA-dependent gene silencing involving Ago2-mediated cleavage of a circular antisense RNA.EMBO J2011;30:4414-22 PMCID:PMC3230379

[30] Park OH,Lee Y.Endoribonucleolytic Cleavage of m⁶A-Containing RNAs by RNase P/MRP Complex.Mol Cell2019;74:494-507.e8

[31] Liu CX,Nan F.Structure and degradation of circular RNAs regulate PKR activation in innate immunity.Cell2019;177:865-880.e21

[32] Fischer JW,Shao Y.Structure-mediated RNA decay by UPF1 and G3BP1.Mol Cell2020;78:70-84.e6 PMCID:PMC8055448

[33] Yu T,Fan Y.CircRNAs in cancer metabolism: a review.J Hematol Oncol2019;12:90 PMCID:PMC6727394

[34] Zhou R,Wang W.Circular RNAs (circRNAs) in cancer.Cancer Lett2018;425:134-42

[35] Xu L,Zheng X,Lan C.The circular RNA ciRS-7 (Cdr1as) acts as a risk factor of hepatic microvascular invasion in hepatocellular carcinoma.J Cancer Res Clin Oncol2017;143:17-27

[36] Yan B,Mao XW.Circular RNA ciRS-7 correlates with advance disease and poor prognosis, and its down-regulation inhibits cells proliferation while induces cells apoptosis in non-small cell lung cancer.Eur Rev Med Pharmacol Sci2018;22:8712-21

[37] Wang L,Wu X.Circ-SOX4 promotes non-small cell lung cancer progression by activating the Wnt/β-catenin pathway.Mol Oncol2020;14:3253 PMCID:PMC7718952

[38] Chen X,Su W.Circular RNA circHIPK3 modulates autophagy via MIR124-3p-STAT3-PRKAA/AMPKα signaling in STK11 mutant lung cancer.Autophagy2020;16:659-71 PMCID:PMC7138221

[39] Xie Y,Zhou W.The circular RNA HIPK3 (circHIPK3) and its regulation in cancer progression: review.Life Sci2020;254:117252

[40] Wang Y,Lu H.Circular RNA SMARCA5 inhibits the proliferation, migration, and invasion of non-small cell lung cancer by miR-19b-3p/HOXA9 axis.Onco Targets Ther2019;12:7055-65 PMCID:PMC6722457

[41] Qiu BQ,Xiong D.CircRNA fibroblast growth factor receptor 3 promotes tumor progression in non-small cell lung cancer by regulating Galectin-1-AKT/ERK1/2 signaling.J Cell Physiol2019;234:11256-64

[42] Liu G,Deng L.Circular RNA circ-FOXM1 facilitates cell progression as ceRNA to target PPDPF and MACC1 by sponging miR-1304-5p in non-small cell lung cancer.Biochem Biophys Res Commun2019;513:207-12

[43] Varella-Garcia M.Chromosomal and genomic changes in lung cancer.Cell Adh Migr2010;4:100-6 PMCID:PMC2852566

[44] Wu K,Gong Y.Circular RNA F-circSR derived from SLC34A2-ROS1 fusion gene promotes cell migration in non-small cell lung cancer.Mol Cancer2019;18:98 PMCID:PMC6530145

[45] Huang XY,Wei CY.Circular RNA circMET drives immunosuppression and anti-PD1 therapy resistance in hepatocellular carcinoma via the miR-30-5p/snail/DPP4 axis.Mol Cancer2020;19:92 PMCID:PMC7236145

[46] Pei X,Long X.circMET promotes NSCLC cell proliferation, metastasis, and immune evasion by regulating the miR-145-5p/CXCL3 axis.Aging (Albany NY)2020;12:13038-58 PMCID:PMC7377868

[47] Li YH,He CJ,Liu JL.circMTDH.4/miR-630/AEG-1 axis participates in the regulation of proliferation, migration, invasion, chemoresistance, and radioresistance of NSCLC.Mol Carcinog2020;59:141-53

[48] Dong Y,Zhong S.Circ_0076305 regulates cisplatin resistance of non-small cell lung cancer via positively modulating STAT3 by sponging miR-296-5p.Life Sci2019;239:116984

[49] Xu Y,Wu C.CircAKT3 inhibits glycolysis balance in lung cancer cells by regulating miR-516b-5p/STAT3 to inhibit cisplatin sensitivity.Biotechnol Lett2020;42:1123-35

[50] Xu N,Liu Y.Profiles and bioinformatics analysis of differentially expressed circrnas in taxol-resistant non-small cell lung cancer cells.Cell Physiol Biochem2018;48:2046-60

[51] Yu W,Sha H.Hsa_circ_0003998 promotes chemoresistance via modulation of miR-326 in lung adenocarcinoma cells.Oncol Res2019;27:623-8 PMCID:PMC7848394

[52] Huang MS,Xia XB.Hsa_circ_0001946 inhibits lung cancer progression and mediates cisplatin sensitivity in non-small cell lung cancer via the nucleotide excision repair signaling pathway.Front Oncol2019;9:508 PMCID:PMC6582772

[53] Zheng F.CircPVT1 contributes to chemotherapy resistance of lung adenocarcinoma through miR-145-5p/ABCC1 axis.Biomed Pharmacother2020;124:109828

[54] Ding C,Wu X.Exosome-mediated transfer of circRNA CircNFIX enhances temozolomide resistance in glioma.Cancer Lett2020;479:1-12

[55] Huang W,Wu J.Circular RNA cESRP1 sensitises small cell lung cancer cells to chemotherapy by sponging miR-93-5p to inhibit TGF-β signalling.Cell Death Differ2020;27:1709-27 PMCID:PMC7206039

[56] Zhou Y,Xu B.Circular RNA hsa_circ_0004015 regulates the proliferation, invasion, and TKI drug resistance of non-small cell lung cancer by miR-1183/PDPK1 signaling pathway.Biochem Biophys Res Commun2019;508:527-35

[57] Fu Y,Tang H.hsa_circRNA_012515 is highly expressed in NSCLC patients and affects its prognosis.Cancer Manag Res2020;12:1877-86 PMCID:PMC7075336

[58] Chen T,Gu Y,Luo Q.Comprehensive analysis of circular RNA profiling in AZD9291-resistant non-small cell lung cancer cell lines.Thorac Cancer2019;10:930-41 PMCID:PMC6449233

[59] Zhang PF,Li KS.Circular RNA circFGFR1 promotes progression and anti-PD-1 resistance by sponging miR-381-3p in non-small cell lung cancer cells.Mol Cancer2019;18:179 PMCID:PMC6900862

[60] Yang H,Yang Y.Hypoxia induced exosomal circRNA promotes metastasis of Colorectal Cancer via targeting GEF-H1/RhoA axis.Theranostics2020;10:8211-26 PMCID:PMC7381736

[61] Li Y,Bao C.Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis.Cell Res2015;25:981-4 PMCID:PMC4528056

[62] Lasda E.Circular RNAs Co-precipitate with extracellular vesicles: a possible mechanism for circRNA clearance.PLoS One2016;11:e0148407 PMCID:PMC4743949

[63] Wang M,Li P.Emerging function and clinical significance of exosomal circRNAs in cancer.Mol Ther Nucleic Acids2020;21:367-83 PMCID:PMC7340966

[64] Shang BQ,Quan HY.Functional roles of circular RNAs during epithelial-to-mesenchymal transition.Mol Cancer2019;18:138 PMCID:PMC6745795

[65] Chen F,Wu Q,Chen S.Circular RNAs expression profiles in plasma exosomes from early-stage lung adenocarcinoma and the potential biomarkers.J Cell Biochem2020;121:2525-33

[66] He F,Lin Z.Plasma exo-hsa_circRNA_0056616: a potential biomarker for lymph node metastasis in lung adenocarcinoma.J Cancer2020;11:4037-46 PMCID:PMC7196257

[67] Xian J,Liu L.Identification of three circular RNA cargoes in serum exosomes as diagnostic biomarkers of non-small-cell lung cancer in the chinese population.J Mol Diagn2020;22:1096-108

[68] Hang D,Qin N.A novel plasma circular RNA circFARSA is a potential biomarker for non-small cell lung cancer.Cancer Med2018;7:2783-91 PMCID:PMC6010816

[69] Liu XX,Liu X.A two-circular RNA signature as a noninvasive diagnostic biomarker for lung adenocarcinoma.J Transl Med2019;17:50 PMCID:PMC6380039

[70] Tan S,Pu W.Circular RNA F-circEA produced from EML4-ALK fusion gene as a novel liquid biopsy biomarker for non-small cell lung cancer.Cell Res2018;28:693-5 PMCID:PMC5993747

[71] Alhasan AA,Al-Balool HH.Circular RNA enrichment in platelets is a signature of transcriptome degradation.Blood2016;127:e1-e11 PMCID:PMC4797142

[72] Preußer C,Schneider T.Selective release of circRNAs in platelet-derived extracellular vesicles.J Extracell Vesicles2018;7:1424473 PMCID:PMC5769804

[73] Best MG,In 't Veld SGJG.Swarm intelligence-enhanced detection of non-small-cell lung cancer using tumor-educated platelets.Cancer Cell2017;32:238-252.e9 PMCID:PMC6381325

[74] Liu YT,Xing PY.Circular RNA profiling identified as a biomarker for predicting the efficacy of Gefitinib therapy for non-small cell lung cancer.J Thorac Dis2019;11:1779-87 PMCID:PMC6588778

[75] Konoshenko MY,Vlassov AV.Isolation of extracellular vesicles: general methodologies and latest trends.Biomed Res Int2018;2018:8545347 PMCID:PMC5831698

[76] Xu R,Chen M,Greening DW.Extracellular vesicles in cancer - implications for future improvements in cancer care.Nat Rev Clin Oncol2018;15:617-38

[77] Théry C,Aikawa E.Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines.J Extracell Vesicles2018;7:1535750 PMCID:PMC6322352

[78] Tang YT,Zheng L.Comparison of isolation methods of exosomes and exosomal RNA from cell culture medium and serum.Int J Mol Med2017;40:834-44 PMCID:PMC5548045

[79] Guria A,Srikakulam N.Circular RNA profiling by illumina sequencing via template-dependent multiple displacement amplification.Biomed Res Int2019;2019:2756516 PMCID:PMC6369502

[80] Hert DG,Barron AE.Advantages and limitations of next-generation sequencing technologies: a comparison of electrophoresis and non-electrophoresis methods.Electrophoresis2008;29:4618-26

[81] Qu S,Yang X.Microarray expression profile of circular RNAs in human pancreatic ductal adenocarcinoma.Genom Data2015;5:385-7 PMCID:PMC4583707

[82] Kulkarni MM.Digital multiplexed gene expression analysis using the NanoString nCounter system.Curr Protoc Mol Biol2011;Chapter 25:Unit25B.10

[83] Kamyabi N,Maitra A,Biswal SL.Isolation and mutational assessment of pancreatic cancer extracellular vesicles using a microfluidic platform.Biomed Microdevices2020;22:23

[84] Garcia-Contreras M,Tamayo A.Plasma-derived exosome characterization reveals a distinct microRNA signature in long duration Type 1 diabetes.Sci Rep2017;7:5998 PMCID:PMC5519761

[85] Dahl M,Andersen MS.Enzyme-free digital counting of endogenous circular RNA molecules in B-cell malignancies.Lab Invest2018;98:1657-69 PMCID:PMC6265260

[86] Vincent HA.Insights into how RNase R degrades structured RNA: analysis of the nuclease domain.J Mol Biol2009;387:570-83 PMCID:PMC2786168

[87] Xiao MS.An improved method for circular RNA purification using RNase R that efficiently removes linear RNAs containing G-quadruplexes or structured 3' ends.Nucleic Acids Res2019;47:8755-69 PMCID:PMC6895279

[88] Koch L.RNA: Translated circular RNAs.Nat Rev Genet2017;18:272-3

[89] Panda AC.Detection and analysis of circular RNAs by RT-PCR.Bio Protoc2018;8:e2775 PMCID:PMC5891140

[90] Zhong S,Yang S.Identification of internal control genes for circular RNAs.Biotechnol Lett2019;41:1111-9

[91] You X,Babic A.Neural circular RNAs are derived from synaptic genes and regulated by development and plasticity.Nat Neurosci2015;18:603-10 PMCID:PMC4376664

[92] Conn V.SplintQuant: a method for accurately quantifying circular RNA transcript abundance without reverse transcription bias.RNA2019;25:1202-10 PMCID:PMC6800515

[93] Liu M,Shen J,Ding X.Circbank: a comprehensive database for circRNA with standard nomenclature.RNA Biol2019;16:899-905 PMCID:PMC6546381

[94] Glažar P,Rajewsky N.circBase: a database for circular RNAs.RNA2014;20:1666-70 PMCID:PMC4201819

[95] Feng J,Xia S.CircView: a visualization and exploration tool for circular RNAs.Brief Bioinform2018;19:1310-6

[96] Liangsupree T,Riekkola ML.Modern isolation and separation techniques for extracellular vesicles.J Chromatogr A2021;1636:461773

[97] Han L,Xu Q,Lam EW.Extracellular vesicles in the tumor microenvironment: therapeutic resistance, clinical biomarkers, and targeting strategies.Med Res Rev2017;37:1318-49

[98] Saarenheimo J,Andersen H,Jekunen A.The value of liquid biopsies for guiding therapy decisions in non-small cell lung cancer.Front Oncol2019;9:129 PMCID:PMC6411700

[99] Wen G,Gu W.The potential of using blood circular RNA as liquid biopsy biomarker for human diseases.Protein Cell2020;

[100] Fan CM,Tang YY.circMAN1A2 could serve as a novel serum biomarker for malignant tumors.Cancer Sci2019;110:2180-8 PMCID:PMC6609809

[101] Lam WK, Dennis Lo YM. Circular RNAs as urinary biomarkers.Clin Chem2019;65:1196-8

[102] Akhoundova D,Musmann LE.The role of the liquid biopsy in decision-making for patients with non-small cell lung cancer.J Clin Med2020;9:3674 PMCID:PMC7696948

[103] Dudekula DB,Grammatikakis I,Abdelmohsen K.CircInteractome: a web tool for exploring circular RNAs and their interacting proteins and microRNAs.RNA Biol2016;13:34-42 PMCID:PMC4829301

[104] Dong R,Li GW.CIRCpedia v2: an updated database for comprehensive circular RNA annotation and expression comparison.Genomics Proteomics Bioinformatics2018;16:226-33 PMCID:PMC6203687

[105] Chen X,Zhou T.et al. circRNADb: a comprehensive database for human circular RNAs with protein-coding annotations.Sci Rep2016;6:34985 PMCID:PMC5057092

[106] circRNABase. Available from: http://www.hzrna.com/circrn-shujuku/circrnabase [Last accessed on 30 Jun 2021]

[107] Fan C,Fang Z,Wu FX.CircR2Disease: a manually curated database for experimentally supported circular RNAs associated with various diseases.Database (Oxford)2018;2018 PMCID:PMC5941138

[108] Li JH,Zhou H,Yang JH.starBase v2.0: decoding miRNA-ceRNA, miRNA-ncRNA and protein-RNA interaction networks from large-scale CLIP-Seq data.Nucleic Acids Res2014;42:D92-7 PMCID:PMC3964941

[109] Wu W,Zhao F.CircAtlas: an integrated resource of one million highly accurate circular RNAs from 1070 vertebrate transcriptomes.Genome Biol2020;21:101 PMCID:PMC7187532

[110] Meng X,Zhang P,Chen M.CircFunBase: a database for functional circular RNAs.Database (Oxford)2019;2019 PMCID:PMC6360206

[111] Rophina M,Poojary M.Circad: a comprehensive manually curated resource of circular RNA associated with diseases.Database (Oxford)2020;2020:baaa019 PMCID:PMC7100626

[112] Xia S,Chen K.CSCD: a database for cancer-specific circular RNAs.Nucleic Acids Res2018;46:D925-9 PMCID:PMC5753219

[113] Niu M,Li Y.CirRNAPL: a web server for the identification of circRNA based on extreme learning machine.Comput Struct Biotechnol J2020;18:834-42 PMCID:PMC7153170

[114] Ghosal S,Sen R,Chakrabarti J.Circ2Traits: a comprehensive database for circular RNA potentially associated with disease and traits.Front Genet2013;4:283 PMCID:PMC3857533

[115] Chen L,Bruggeman EC,Yao B.circMeta: a unified computational framework for genomic feature annotation and differential expression analysis of circular RNAs.Bioinformatics2020;36:539-45 PMCID:PMC7999137

[116] Li L,Zhao Y.CircRNAwrap - a flexible pipeline for circRNA identification, transcript prediction, and abundance estimation.FEBS Lett2019;593:1179-89

[117] Ungerleider N.SpliceV: analysis and publication quality printing of linear and circular RNA splicing, expression and regulation.BMC Bioinformatics2019;20:231 PMCID:PMC6507234

[118] Ma XK,Liu CX.CIRCexplorer3: a CLEAR pipeline for direct comparison of circular and linear RNA expression.Genomics Proteomics Bioinformatics2019;17:511-21 PMCID:PMC7056929

[119] Chaabane M,Stephens AT.circDeep: deep learning approach for circular RNA classification from other long non-coding RNA.Bioinformatics2020;36:73-80 PMCID:PMC6956777

[120] Hoffmann S,Doose G.A multi-split mapping algorithm for circular RNA, splicing, trans-splicing and fusion detection.Genome Biol2014;15:R34 PMCID:PMC4056463

[121] Cheng J,Dieterich C.Specific identification and quantification of circular RNAs from sequencing data.Bioinformatics2016;32:1094-6

[122] Song X,Han P,Wang K.Circular RNA profile in gliomas revealed by identification tool UROBORUS.Nucleic Acids Res2016;44:e87 PMCID:PMC4872085

[123] Chuang TJ,Chen CY,Chiang TW.NCLscan: accurate identification of non-co-linear transcripts (fusion, trans-splicing and circular RNA) with a good balance between sensitivity and precision.Nucleic Acids Res2016;44:e29 PMCID:PMC4756807

[124] Tang Z,Zhao J.TRCirc: a resource for transcriptional regulation information of circRNAs.Brief Bioinform2019;20:2327-33

[125] Cheng L,Scicluna BJ,Hill AF.Characterization and deep sequencing analysis of exosomal and non-exosomal miRNA in human urine.Kidney Int2014;86:433-44

[126] Valladares-Ayerbes M,Taron M.Circular RNAs as biomarkers in liquid biopsy in colorectal cancer.Clinical Oncol2020;38:suppl

[127] Zhang J,Li C.Circular RNA profiling provides insights into their subcellular distribution and molecular characteristics in HepG2 cells. RNA Biol 2019;16:220-32. PMCID:PMC6380345

[128] Sun L,Schnell R.Structural and Functional Characterization of the BcsG Subunit of the Cellulose Synthase in Salmonella typhimurium.JMB2018;18:3170-89 PMCID:PMC7020665