title: Increased PRAME antigen-specific killing of malignant cell lines by low avidity CTL clones, following treatment with 5-Aza-2'-Deoxycytidine.
abstract: The cancer testis antigen Preferentially Expressed Antigen of Melanoma (PRAME) is overexpressed in many solid tumours and haematological malignancies whilst showing minimal expression in normal tissues and is therefore a promising target for immunotherapy. HLA-A0201-restricted peptide epitopes from PRAME have previously been identified as potential immunogens to drive antigen-specific autologous CTL responses, capable of lysing PRAME expressing tumour cells. CTL lines, from 13 normal donors and 10 melanoma patients, all of whom were HLA-A0201 positive, were generated against the PRAME peptide epitope PRA(100-108). Specific killing activity against PRA(100-108) peptide-pulsed targets was weak compared with CTL lines directed against known immunodominant peptides. Moreover, limiting dilution cloning from selected PRAME-specific CTL lines resulted in the generation of a clone of only low to intermediate avidity. Addition of the demethylating agent 5-aza-2'-Deoxycytidine (DAC) increased PRAME expression in 7 out of 11 malignant cell lines including several B lineage leukaemia lines and also increased class I expression. Pre-treatment of target cells was associated with increased sensitivity to antigen-specific killing by the low avidity CTL. When CTL, as well as of the target cells, were treated, the antigen-specific killing was further augmented. Interestingly, one HLA-A0201-negative DAC-treated line (RAJI) showed increased sensitivity to killing by clones despite a failure of expression of PRAME or HLA-A0201. Together these data point to a general increased augmentation of cancer immunogenocity by DAC involving both antigen-specific and non-specific mechanisms.
authors.affiliation: Unit of Molecular Haematology and Cancer Biology, University College London Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
authors.forename: Mengyong
authors.initials: M
authors.lastname: Yan
authors.forename: Nourredine
authors.initials: N
authors.lastname: Himoudi
authors.forename: B Piku
authors.initials: BP
authors.lastname: Basu
authors.forename: Rebecca
authors.initials: R
authors.lastname: Wallace
authors.forename: Edmund
authors.initials: E
authors.lastname: Poon
authors.forename: Stuart
authors.initials: S
authors.lastname: Adams
authors.forename: Fyeza
authors.initials: F
authors.lastname: Hasan
authors.forename: Shao-An
authors.initials: SA
authors.lastname: Xue
authors.forename: Natalie
authors.initials: N
authors.lastname: Wilson
authors.forename: Angus
authors.initials: A
authors.lastname: Dalgleish
authors.forename: Owen
authors.initials: O
authors.lastname: Williams
authors.forename: John
authors.initials: J
authors.lastname: Anderson
mesh_terms: D000915:Antibody Affinity; D000951:Antigens, Neoplasm / Q000276:immunology* / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D000077209:Decitabine; D018922:HL-60 Cells; D015789:HLA-A2 Antigen / Q000276:immunology; D006801:Humans; D016219:Immunotherapy, Adoptive / Q000379:methods*; D020014:K562 Cells; D009369:Neoplasms / Q000276:immunology* / Q000628:therapy*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014162:Transfection
chemical_list: D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; C404944:PRAME protein, human; D000077209:Decitabine; D001374:Azacitidine