title: Genotyping and expression analysis of IDO2 in human pancreatic cancer: a novel, active target.
abstract: BACKGROUND
  The recently discovered indoleamine 2,3-dioxygenase-2 (IDO2) gene has 2 functional polymorphisms that abolish its enzymatic activity. We hypothesize that expression of the IDO2 enzyme in primary pancreatic ductal adenocarcinomas (PDA) can help cancer cells evade immune detection.
  
  
  METHODS
  Because the IDO2 enzyme might be the preferential target of d-1-methyl-tryptophan, a clinical lead inhibitor of IDO currently being evaluated in phase I trials, we sequenced IDO2 in 36 pancreatic specimens and evaluated its expression.
  
  
  RESULTS
  We found that 58% (21 of 36) of cases were heterozygous for the R248W polymorphism; 28% (10 of 36) were homozygous wild-type; and only 14% (5 of 36) were homozygous for the functionally inactive polymorphism. As for the Y359STOP polymorphism, we found that 27% (10 of 36) of cases were heterozygous, 62% (22 of 36) were homozygous wild-type, and only 11% (4 of 36) were homozygous for this functionally inactive allele. Ruling out the possibility of compound polymorphic variants, we estimated 75% of our resected patient cohort had an active IDO2 enzyme, with a conservative estimate that 58% of the patients had at least 1 functional allele. IDO2 was expressed in PDA tissue from each genetically polymorphic subgroup. We also detected IDO2 protein expression in the genetically distinct pancreatic cancer cell lines after exposure with interferon-gamma.
  
  
  CONCLUSIONS
  This is the first study to report IDO2 expression in PDA and related cancers indicating that IDO2 genetic polymorphisms do not negate interferon-gamma-inducible protein expression. Taken together, our data strongly suggest that the clinical lead compound d-1-methyl-tryptophan might be useful in treatment of PDA.
authors.affiliation: Department of Pathology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Agnieszka K
authors.initials: AK
authors.lastname: Witkiewicz
authors.forename: Christina L
authors.initials: CL
authors.lastname: Costantino
authors.forename: Richard
authors.initials: R
authors.lastname: Metz
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Muller
authors.forename: George C
authors.initials: GC
authors.lastname: Prendergast
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Yeo
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Brody
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000201:enzymology* / Q000276:immunology; D045744:Cell Line, Tumor; D005838:Genotype; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000235:genetics* / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000276:immunology; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D015854:Up-Regulation / Q000502:physiology
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007371:Interferon-gamma