Mutated regions of nucleophosmin 1 elicit both CD4+ and CD8+ T-cell responses in patients with acute myeloid leukemia

Abstract

Mutations in the nucleophosmin gene (NPM1 mut ) are one of the most frequent molecular alterations in acute myeloid leukemia (AML), and immune responses may contribute to the favorable prognosis of AML patients with NPM1 mut . In the present study, we were able to demonstrate both CD4 ؉ and CD8 ؉ T-cell responses against NPM1 mut . Ten peptides derived from wild-type NPM1 and NPM1 mut were subjected to ELISPOT analysis in 33 healthy volunteers and 27 AML patients.Tetramer assays against the most interesting epitopes were performed and Cr 51 -release assays were used to show the cytotoxicity of peptide-specific T cells. Moreover, HLA-DR-binding epitopes were used to test the role of CD4 ؉ T cells in NPM1 immunogenicity. Two epitopes (epitopes #1 and #3) derived from NPM1 mut induced CD8 ؉ T-cell responses. A total of 33% of the NPM1 mut AML patients showed immune responses against epitope #1 and 44% against epitope #3. Specific lysis of leukemic blasts was detected. To obtain robust immune responses against tumor cells, the activation of CD4 ؉ T cells is crucial. Therefore, overlapping (OL) peptides were analyzed in ELISPOT assays and OL8 was able to activate both CD8 ؉ and CD4 ؉ T cells. The results of the present study show that NPM1 mut induces specific T-cell responses of CD4 ؉ and CD8 ؉ T cells and therefore is a promising target for specific immunotherapies in AML. (Blood. 2012;120(6):1282-1289) IntroductionMutations in the nucleophosmin 1 gene (NPM1 mut ) represent some of the most common gene mutations in acute myeloid leukemia (AML). 1,2 Falini et al first described the abnormal cytoplasmic localization of the NPM1 protein caused by mutations in exon 12 of the gene. 3 In AML patients with normal cytogenetics, the incidence of NPM1 mut was reported in up to 60% of the patients. 1-3 NPM1 constitutes an important prognostic marker, especially in the context of FMS-related tyrosine kinase internal tandem duplication (FLT3-ITD). In more than 90% of AML patients harboring NPM1 mut , the 3 different NPM1 mut types (A, B, and D) were found. 1,2,4-6 AML patients harboring an NPM1 mut without an FLT3-ITD mutation showed improved survival when treated with intensive chemotherapy. 2 Most AML patients with NPM1 mut seem not to benefit from an allogeneic stem cell transplantation as a first-line treatment. 2,7 However, this issue remains to be elucidated in the context of minimal residual disease detection 8 and the coexistence of other molecular markers. The functional role of NPM1 mut for the improved clinical outcome remains to be elucidated. Immune responses may contribute to clinical outcome by lysis of residual leukemic cells through specific T cells after chemotherapy. Leukemia-associated antigens (LAAs) can be targeted by the immune system in a specific manner, leading to the hypothesis that the expression of LAAs might also influence the clinical outcome of AML patients. mRNA expression of at least 1 of the 3 LAA, receptor for hyaluronic acid-mediated motility (RHAMM), preferentially expressed antigen in mela...

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

“…This is reflected by the emergence of antigen-specific CD8 þ T cells in the peripheral blood of AML patients following transplantation. Such CTL responses have been reported against a broad range of AML-related tumor antigens, including HOXA9 (HOXA9 146-154 ), 62 hTERT (hTERT 540-548 ), 62 27,62 and RAGE-1 (RAGE-1 [11][12][13][14][15][16][17][18][19][20] (Table 1). 79 NuSAP1 has been identified as a target of humoral immunity following allogeneic HSCT.…”

“…The mutant proteins arising from these gene mutations are known to act as LSAs. [10][11][12] The majority of antigens have been characterized as LAAs, that is, they are expressed by both normal and leukemic cells. Hence, autoimmunity could be a logical consequence of targeting TAAs.…”

Analogue peptides for the immunotherapy of human acute myeloid leukemia

“…It was shown that epitopes derived from the mutated regions of NPM1 induced specific CD4 + and CD8 + T-cell responses. Two HLA-A2 restricted epitopes induced high frequencies of specific CD8 + T-cell responses in healthy volunteers and AML patients [79]. Furthermore, a survival analysis of 25 NPM1 mut patients, comparing cases with or without specific CTL responses against NPM1 mut epitopes, suggested a better overall survival of patients with specific NPM1 mut CTL responses [80].…”

Acute myeloid leukemia with mutated nucleophosmin 1: an immunogenic acute myeloid leukemia subtype and potential candidate for immune checkpoint inhibition

“…Our group previously described specific immune responses against epitopes derived from the mutational region of NPM1. 1 Furthermore, in a smaller cohort of AML patients we found a significantly better overall survival for patients with specific cytotoxic T-lymphocyte (CTL) response against NPM1 mut -derived immunogenic epitopes, 2 when compared to NPM1 wt AML patients. This suggests that immune responses against NPM1 mut might in part contribute to the more favorable outcome in AML patients.…”