title: A novel HLA-A*0201 restricted peptide derived from cathepsin G is an effective immunotherapeutic target in acute myeloid leukemia.
abstract: OBJECTIVE
  Immunotherapy targeting aberrantly expressed leukemia-associated antigens has shown promise in the management of acute myeloid leukemia (AML). However, because of the heterogeneity and clonal evolution that is a feature of myeloid leukemia, targeting single peptide epitopes has had limited success, highlighting the need for novel antigen discovery. In this study, we characterize the role of the myeloid azurophil granule protease cathepsin G (CG) as a novel target for AML immunotherapy.
  
  
  METHODS
  We used Immune Epitope Database and in vitro binding assays to identify immunogenic epitopes derived from CG. Flow cytometry, immunoblotting, and confocal microscopy were used to characterize the expression and processing of CG in AML patient samples, leukemia stem cells, and normal neutrophils. Cytotoxicity assays determined the susceptibility of AML to CG-specific cytotoxic T lymphocytes (CTL). Dextramer staining and cytokine flow cytometry were conducted to characterize the immune response to CG in patients.
  
  
  RESULTS
  CG was highly expressed and ubiquitinated in AML blasts, and was localized outside granules in compartments that facilitate antigen presentation. We identified five HLA-A*0201 binding nonameric peptides (CG1-CG5) derived from CG, and showed immunogenicity of the highest HLA-A*0201 binding peptide, CG1. We showed killing of primary AML by CG1-CTL, but not normal bone marrow. Blocking HLA-A*0201 abrogated CG1-CTL-mediated cytotoxicity, further confirming HLA-A*0201-dependent killing. Finally, we showed functional CG1-CTLs in peripheral blood from AML patients following allogeneic stem cell transplantation.
  
  
  CONCLUSIONS
  CG is aberrantly expressed and processed in AML and is a novel immunotherapeutic target that warrants further development.
authors.affiliation: Stem Cell Transplantation and Cellular Therapy, Surgical Oncology, and Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Mao
authors.initials: M
authors.lastname: Zhang
authors.forename: Pariya
authors.initials: P
authors.lastname: Sukhumalchandra
authors.forename: Atim A
authors.initials: AA
authors.lastname: Enyenihi
authors.forename: Lisa S
authors.initials: LS
authors.lastname: St John
authors.forename: Sally A
authors.initials: SA
authors.lastname: Hunsucker
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Mittendorf
authors.forename: Anna
authors.initials: A
authors.lastname: Sergeeva
authors.forename: Kathryn
authors.initials: K
authors.lastname: Ruisaard
authors.forename: Zein
authors.initials: Z
authors.lastname: Al-Atrache
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Ropp
authors.forename: Haroon
authors.initials: H
authors.lastname: Jakher
authors.forename: Tania
authors.initials: T
authors.lastname: Rodriguez-Cruz
authors.forename: Gregory
authors.initials: G
authors.lastname: Lizee
authors.forename: Karen
authors.initials: K
authors.lastname: Clise-Dwyer
authors.forename: Sijie
authors.initials: S
authors.lastname: Lu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Molldrem
authors.forename: Gary L
authors.initials: GL
authors.lastname: Glish
authors.forename: Paul M
authors.initials: PM
authors.lastname: Armistead
authors.forename: Gheath
authors.initials: G
authors.lastname: Alatrash
mesh_terms: D051997:ADP-ribosyl Cyclase 1 / Q000378:metabolism; D018952:Antigens, CD34 / Q000378:metabolism; D056649:Cathepsin G / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic; D000939:Epitopes / Q000276:immunology / Q000378:metabolism; D015789:HLA-A2 Antigen / Q000276:immunology* / Q000378:metabolism; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007167:Immunotherapy; D015470:Leukemia, Myeloid, Acute / Q000276:immunology* / Q000378:metabolism / Q000628:therapy; D010455:Peptides / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D021381:Protein Transport; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014184:Transplantation, Homologous
chemical_list: D018952:Antigens, CD34; D000939:Epitopes; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D010455:Peptides; D051997:ADP-ribosyl Cyclase 1; D056649:Cathepsin G