title: Mathematical model of a telomerase transcriptional regulatory network developed by cell-based screening: analysis of inhibitor effects and telomerase expression mechanisms.
abstract: Cancer cells depend on transcription of telomerase reverse transcriptase (TERT). Many transcription factors affect TERT, though regulation occurs in context of a broader network. Network effects on telomerase regulation have not been investigated, though deeper understanding of TERT transcription requires a systems view. However, control over individual interactions in complex networks is not easily achievable. Mathematical modelling provides an attractive approach for analysis of complex systems and some models may prove useful in systems pharmacology approaches to drug discovery. In this report, we used transfection screening to test interactions among 14 TERT regulatory transcription factors and their respective promoters in ovarian cancer cells. The results were used to generate a network model of TERT transcription and to implement a dynamic Boolean model whose steady states were analysed. Modelled effects of signal transduction inhibitors successfully predicted TERT repression by Src-family inhibitor SU6656 and lack of repression by ERK inhibitor FR180204, results confirmed by RT-QPCR analysis of endogenous TERT expression in treated cells. Modelled effects of GSK3 inhibitor 6-bromoindirubin-3'-oxime (BIO) predicted unstable TERT repression dependent on noise and expression of JUN, corresponding with observations from a previous study. MYC expression is critical in TERT activation in the model, consistent with its well known function in endogenous TERT regulation. Loss of MYC caused complete TERT suppression in our model, substantially rescued only by co-suppression of AR. Interestingly expression was easily rescued under modelled Ets-factor gain of function, as occurs in TERT promoter mutation. RNAi targeting AR, JUN, MXD1, SP3, or TP53, showed that AR suppression does rescue endogenous TERT expression following MYC knockdown in these cells and SP3 or TP53 siRNA also cause partial recovery. The model therefore successfully predicted several aspects of TERT regulation including previously unknown mechanisms. An extrapolation suggests that a dominant stimulatory system may programme TERT for transcriptional stability.
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Bilsland
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: Katrina
authors.initials: K
authors.lastname: Stevenson
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: Stacey
authors.initials: S
authors.lastname: Hoare
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: Claire J
authors.initials: CJ
authors.lastname: Cairney
authors.affiliation: Cancer Research Technology Ltd., Wolfson Institute for Biomedical Research, London, United Kingdom.
authors.forename: Jon
authors.initials: J
authors.lastname: Roffey
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, United Kingdom.
authors.forename: W Nicol
authors.initials: WN
authors.lastname: Keith
mesh_terms: D045744:Cell Line, Tumor; D019295:Computational Biology; D055808:Drug Discovery; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D053263:Gene Regulatory Networks / Q000235:genetics; D016259:Genes, myc; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D055641:Mathematical Concepts; D008954:Models, Biological; D008957:Models, Genetic; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D050787:Proto-Oncogene Protein c-ets-2 / Q000235:genetics; D011720:Pyrazoles / Q000494:pharmacology; D011724:Pyridazines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
chemical_list: C494069:ETS2 protein, human; D004791:Enzyme Inhibitors; C505241:FR 180204; D007211:Indoles; D050787:Proto-Oncogene Protein c-ets-2; D011720:Pyrazoles; D011724:Pyridazines; C416927:SU 6656; D013449:Sulfonamides; D038362:Glycogen Synthase Kinase 3; C509186:TERT protein, human; D019098:Telomerase