title: Noninvasive theranostic imaging of HSV1-sr39TK-NTR/GCV-CB1954 dual-prodrug therapy in metastatic lung lesions of MDA-MB-231 triple negative breast cancer in mice.
abstract: Metastatic breast cancer is an obdurate cancer type that is not amenable to chemotherapy regimens currently used in clinic. There is a desperate need for alternative therapies to treat this resistant cancer type. Gene-Directed Enzyme Prodrug Therapy (GDEPT) is a superior gene therapy method when compared to chemotherapy and radiotherapy procedures, proven to be effective against many types of cancer in pre-clinical evaluations and clinical trials. Gene therapy that utilizes a single enzyme/prodrug combination targeting a single cellular mechanism needs significant overexpression of delivered therapeutic gene in order to achieve therapy response. Hence, to overcome this obstacle we recently developed a dual therapeutic reporter gene fusion that uses two different prodrugs, targeting two distinct cellular mechanisms in order to achieve effective therapy with a limited expression of delivered transgenes. In addition, imaging therapeutic reporter genes offers additional information that indirectly correlates gene delivery, expression, and functional effectiveness as a theranostic approach. In the present study, we evaluate the therapeutic potential of HSV1-sr39TK-NTR fusion dual suicide gene therapy system that we recently developed, in MDA-MB-231 triple negative breast cancer lung-metastatic lesions in a mouse model. We compared the therapeutic potential of HSV1-sr39TK-NTR fusion with respective dual prodrugs GCV-CB1954 with HSV1-sr39TK/GCV and NTR/CB1954 single enzyme prodrug system in this highly resistant metastatic lesion of the lungs. In vitro optimization of dose and duration of exposure to GCV and CB1954 was performed in MDA-MB-231 cells. Drug combinations of 1 μg/ml GCV and 10 μM CB1954 for 3 days was found to be optimal regimen for induction of significant cell death, as assessed by FACS analysis. In vivo therapeutic evaluation in animal models showed a complete ablation of lung metastatic nodules of MDA-MB-231 triple negative breast cancer cells following two consecutive doses of a combination of GCV (40 mg/kg) and CB1954 (40 mg/kg) administered at 5 day intervals. In contrast, the respective treatment condition in animals expressing HSV1-sr39TK or NTR separately, showed minimal or no effect on tumor reduction as measured by bioluminescence (tumor mass) and [(18)F]-FHBG microPET (TK expression) imaging. These highlight the strong therapeutic effect of the dual fusion prodrug therapy and its use in theranostic imaging of tumor monitoring in living animals by multimodality molecular imaging.
authors.affiliation: Molecular Imaging Program at Stanford, Bio-X Program, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Thillai V
authors.initials: TV
authors.lastname: Sekar
authors.affiliation: Molecular Imaging Program at Stanford, Bio-X Program, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Kira
authors.initials: K
authors.lastname: Foygel
authors.affiliation: Molecular Imaging Program at Stanford, Bio-X Program, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Ohad
authors.initials: O
authors.lastname: Ilovich
authors.affiliation: Molecular Imaging Program at Stanford, Bio-X Program, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Paulmurugan
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001388:Aziridines / Q000627:therapeutic use; D004195:Disease Models, Animal; D015316:Genetic Therapy / Q000379:methods*; D005973:Glutamine / Q000031:analogs & derivatives / Q000627:therapeutic use; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy*; D051379:Mice; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging / Q000188:drug therapy*; D009601:Nitroreductases / Q000378:metabolism; D061848:Optical Imaging / Q000379:methods; D009942:Organometallic Compounds / Q000627:therapeutic use; D011355:Prodrugs / Q000627:therapeutic use*; D011859:Radiography; D013937:Thymidine Kinase / Q000378:metabolism; D016896:Treatment Outcome; D064726:Triple Negative Breast Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000556:secondary
chemical_list: D000970:Antineoplastic Agents; D001388:Aziridines; C533573:L-glutamine-o-vanillin-copper; D009942:Organometallic Compounds; D011355:Prodrugs; D005973:Glutamine; C100099:tretazicar; D009601:Nitroreductases; D013937:Thymidine Kinase
keywords: Gene-Directed Enzyme Prodrug Therapy; theranostic imaging; tumor monitoring