Cancer‐testis antigen expression and its epigenetic modulation in acute myeloid leukemia

Abstract

Cancer-testis antigens (CTA) represent attractive targets for tumor immunotherapy. However, a broad picture of CTA expression in acute myeloid leukemia (AML) is missing. CTA expression was analyzed in normal bone marrow (BM) as well as in AML cell lines before and after treatment with demethylating agents and/or histone acetylase inhibitors. Presence of selected CTA with a strictly tumor-restricted expression was then determined in samples of patients with AML before and after demethylating therapy. Screening AML cell lines for the expression of 20 CTA, we identified six genes (MAGE-A3, PRAME, ROPN1, SCP-1, SLLP1, and SPO11) with an AML-restricted expression. Analyzing the expression of these CTA in blast-containing samples from AML patients (N 5 64), we found all samples to be negative for MAGE-A3 and SPO11 while a minority of patients expressed ROPN1 (1.6%), SCP-1 (3.1%), or SLLP1 (9.4%). The only CTA expressed in substantial proportion of patients (53.1%) was PRAME. Following demethylating treatment with 5 0 -aza-2 0 -deoxycytidine, we observed an increased or de novo expression of CTA, in particular of SSX-2, in AML cell lines. In AML patients, we detected increased expression of PRAME and induction of SSX-2 after demethylating therapy with 5-azacytidine. With the exception of PRAME, CTA are mostly absent from AML blasts. However, demethylating treatment induces strong expression of CTA, particularly of SSX-2, in vitro and in vivo. Therefore, we propose that CTA-specific immunotherapy for AML should preferentially target PRAME and/or should be combined with the application of demethylating agents opening the perspective for alternative targets like CTA SSX-2. Am. J. Hematol. 86:918-922, 2011. V

Leukemia-associated antigens and their relevance to the immunotherapy of acute myeloid leukemia

“…86 Scheibenbogen et al 87 were the first to describe the natural existence of CD8 þ T-cell immunity against PR1 and WT1 126-134 in patients with AML, both at diagnosis and in complete remission. 87 These findings were corroborated by the later work of Rezvani et al, 73 who observed spontaneous T-cell responses to PR1 and WT1 [126][127][128][129][130][131][132][133][134] in two out of eight patients before immunization with a combined PR1/WT1 peptide vaccine. 73 In a separate study, the same group found that such CTL responses were not limited to the immunodominant WT1 [126][127][128][129][130][131][132][133][134] epitope, but could also be directed against other HLA-A*0201-restricted WT1-derived epitopes (WT1 [37][38][39][40][41][42][43][44][45] , WT1 [187][188][189][190][191][192][193][194][195] and WT1 [235][236][237][238][239][240][241][2...…”

“…16 This peptide sequence also encompasses the HLA-DP5-restricted WT1 337-347 epitope 70 as well as the WT1 333-347 epitope, which can be recognized by CD4 þ regulatory T cells in the context of HLA-DR4. 71 Other WT1 helper epitopes with direct relevance to AML immunotherapy are WT1 427-445 and WT1 [122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140] . 69 The latter contains another immunogenic CD4 þ T-cell epitope, WT1 [124][125][126][127][128][129][130][131][132][133][134][135][136][137][138] , and the HLA-A*0201-restricted CD8 þ T-cell epitope, WT1 [126][127][128][129][130][131][132][133][134] , 16 and is thus capable of stimulating a combined CD8 þ /CD4 þ WT1-specific T-cell immune response.…”

“…These studies, including WT1 peptide and WT1-targeted dendritic cell vaccine trials, have unequivocally established that CD8 þ T-cell immune responses specific to WT1 can be induced by active immunization in a substantial number of AML patients. 14 In those patients, multiple WT1 CTL epitopes have been recognized as immunogenic (including WT1 [37][38][39][40][41][42][43][44][45] , WT1 [126][127][128][129][130][131][132][133][134] , WT1 [187][188][189][190][191][192][193][194][195] and WT1 [235][236][237][238][239][240][241][242][243] ), demonstrating the excellent in vivo immunostimulatory potential of WT1 (Table 1). 14,72 This is further supported by the capacity to induce WT1-specific CD4 þ helper T-cell immunity in patients with AML through active immunization.…”

“…74 The clinical relevance of PR1 is further supported by the observation of a significant disease-free survival advantage and a trend toward improved overall survival in patients with myeloid malignancies developing immunity to PR1 after peptide immunization. 94 In a clinical trial of combined PR1/WT1 [126][127][128][129][130][131][132][133][134] peptide vaccination, Rezvani et al 73 demonstrated that the induction of high-avidity PR1-and/or WT1-specific CTLs was critically required to achieve clinical response (reduction of WT1 transcript levels). 73 Schmitt et al 47 assessed the clinical effectiveness of RHAMM 165-173 peptide vaccination in a mixed cohort of patients with hematological malignancies, including three patients with AML.…”

Azacitidine salvage therapy for relapse of myeloid malignancies following allogeneic hematopoietic SCT

“…9 AZA has been shown to increase the expression of tumor Ags by leukemic cells. [10][11][12][13] AZA can also increase regulatory T cells and CD8 þ tumor-specific T-cell responses both in vitro and in the human clinical setting. 14,15 Thus, AZA administration may potentially enhance the GVL effect while reducing active GVHD.…”