Septins disruption controls tumor growth and enhances efficacy of Herceptin 1 2 Rakesh K Singh* 1 , Kyu Kwang Kim 1 , Negar Khazan 1 , Rachael B. Rowswell-Turner 1 , Christian 3 Laggner 3 , Aaron Jones 1 , Priyanka Srivastava 1 , Virginia Hovanesian 4 , Liz Lamere 1 , Thomas 4 Conley 1 , Ravina Pandita 1 , Cameron Baker 5 , Jason R Myers 5 , Elizabeth Pritchett 5 , Awada Ahmad 1 , 5 Luis Ruffolo 2 , Katherine Jackson 2 , Scott A. Gerber 2 , John Ashton 5 , Michael T. Milano 6 , David 6 Linehan 2 , Richard G Moore 1 7 8 1 Wilmot Cancer Institute, Division of Gynecologic Oncology, Department of Obstetrics and 9 Gynecology, University of Rochester Medical Center, Rochester, NY, USA. 10 2 Department of Surgery, Microbiology and Immunology; Department of Radiation Oncology and 11 Center for Tumor Immunology Research, University of Rochester Medical Center, Rochester, NY, 12 USA. 13 3 Atomwise Inc, San Francisco, CA, USA. 14 4 Rhode Island Hospital, Providence, RI, USA. 15 5 Genomics Research Center, Wilmot Cancer Center, University of Rochester Medical Center, NY, 16 USA. 17 6 Department of Radiation Oncology, University of Rochester, NY, USA. 18 19 20 * Corresponding author: 21 Rakesh_Singh@URMC.Rochester.Edu 22 Telephone (office): 585-276-6281. Fax: 585-276-2576 23 24 Abstract 25 Septin expressions are altered in cancer cells and exhibit poor prognoses in malignancies. As the 26 first approach to develop a septin filament targeting agent, we optimized the structure of 27 Forchlorfenuron (FCF), a known plant cytokinin to generate UR214-9, which contrary to FCF, 28 causes septin-2/9 filamental structural catastrophe in cancer cells without altering cellular septin 29 protein levels. In-silico docking using septin-2/septin-2 dimer complex showed that UR214-9 30 displaced the guanine carbonyl oxygen from the GDP binding domain and showed increased 31 binding energy than FCF(-8.59vs-7.21). UR214-9 reduced cancer cell growth, downregulated 32 HER2/STAT-3 axis and controlled growth of HER2+ pancreatic, breast and ovarian cancer 33 xenografts in NSG mice and enhanced response of Herceptin against HER2+breast cancer 34 xenograft. Transcriptome analysis of UR214-9 exposed cells demonstrated significant 35 perturbation of <20 genes compared to afatinib which impacted >1200 genes in JIMT-1 breast 36 cancer cells indicating target specificity and non-transcriptional functions of UR214-9. In summary, 37 disrupting septins via UR214-9 is a new approach to control the growth of HER2+ malignancies. 38 39 Introduction 40 41 Septins are a family of GTP-binding cytoskeletal proteins that participate in cytokinesis, 42 cell migration, chromosomal dynamics and protein secretion. Septins hetero-oligomerize to 43 generate scaffolding filaments, bundles, and rings within cells 1-11 . Additionally, septins are a 44 critical cytoskeletal component that regulate the function of tubulin and actin. Altered septin 45