title: Tumor-specific promoter-driven adenoviral therapy for insulinoma.
abstract: BACKGROUND
  Insulinomas are the most common type of neuroendocrine (NE) pancreatic islet tumors. Patients with insulinomas may develop complications associated with hyperinsulinemia. To increase the treatment options for insulinoma patients, we have tested a conditionally replicating adenovirus that has been engineered in such a way that it can specifically express therapeutic genes in NE tumors.
  
  
  METHODS
  We used a promoter-specific adenoviral vector delivery system that is regulated by an INSM1 (insulinoma-associated-1) promoter, which is silent in normal adult tissues but active in developing NE cells and tumors. Through a series of modifications, using an insulator (HS4) and neuron-restrictive silencer elements (NRSEs), an oncolytic adenoviral vector was generated that retains tumor specificity and drives the expression of a mutated adenovirus E1A gene (Δ24E1A) and the herpes simplex virus thymidine kinase (HSV-tk) gene. The efficacy of this vector was tested in insulinoma-derived MIN, RIN, βTC-1 and pancreatic (Panc-1) cells using in vitro cell survival and in vivo tumor growth assays.
  
  
  RESULTS
  Using in vitro insulinoma-derived cell lines and an in vivo subcutaneous mouse tumor model we found that the INSM1 promoter-driven viruses were able to replicate specifically in INSM1-positive cells. INSM1-specific HSV-tk expression in combination with ganciclovir treatment resulted in dose-dependent tumor cell killing, leaving INSM1-negative cells unharmed. When we combined the INSM1-promoter driven HSV-tk with Δ24E1A and INSM1p-HSV-tk (K5) viruses, we found that the co-infected insulinoma-derived cells expressed higher levels of HSV-tk and exhibited more efficient tumor suppression than cells infected with INSM1p-HSV-tk virus alone.
  
  
  CONCLUSIONS
  INSM1 promoter-driven conditionally replicating adenoviruses may serve as a new tool for the treatment of insulinoma and may provide clinicians with additional options to combat this disease.
authors.affiliation: The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, New Orleans, LA, 70118, USA.|Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA.
authors.forename: Alan Wei-Shun
authors.initials: AW
authors.lastname: Tseng
authors.affiliation: The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, New Orleans, LA, 70118, USA.|Laboratory of Diana Helis Henry Medical Research Foundation, New Orleans, LA, 70119, USA.
authors.forename: Chiachen
authors.initials: C
authors.lastname: Chen
authors.affiliation: The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, New Orleans, LA, 70118, USA.|Laboratory of Diana Helis Henry Medical Research Foundation, New Orleans, LA, 70119, USA.|Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA.
authors.forename: Mary B
authors.initials: MB
authors.lastname: Breslin
authors.affiliation: The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, New Orleans, LA, 70118, USA. mlan@chnola-research.org.|Laboratory of Diana Helis Henry Medical Research Foundation, New Orleans, LA, 70119, USA. mlan@chnola-research.org.|Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA. mlan@chnola-research.org.|Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA. mlan@chnola-research.org.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lan
mesh_terms: D000256:Adenoviridae; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D015774:Ganciclovir / Q000494:pharmacology; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D006801:Humans; D007340:Insulinoma; D051379:Mice; D050130:Oncolytic Virotherapy / Q000379:methods*; D010190:Pancreatic Neoplasms; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D012097:Repressor Proteins; C087342:INSM1 protein, human; D013937:Thymidine Kinase; D015774:Ganciclovir
keywords: Endocrine tumor; Gene therapy; INSM1; Insulinoma; Oncolytic