Immune responses against the mutated region of cytoplasmatic NPM1 might contribute to the favorable clinical outcome of AML patients with NPM1 mutations (NPM1mut)

Abstract

Immune responses against the mutated region of cytoplasmatic NPM1 might contribute to the favorable clinical outcome of AML patients with NPM1 mutations (NPM1 mut )Immune responses directed against epitopes derived from the mutated region of nucleophosmin 1 (NPM1) by NPM1 mut -specific CD8(1) cytotoxic T cells (CTLs) might be involved in the rejection of NPM1 mut myeloid leukemic blasts. NPM1 mutations are one of the most frequent molecular alterations in acute myeloid leukemia (AML) and are an important prognostic marker.1 The mutations cause an abnormal shift of the NPM1 protein from the nucleus to the cytoplasm, described by Falini et al.2 AML patients with NPM1 mut , but without FLT3 internal tandem duplication (ITD) mutation, show improved overall survival.3 NPM1 mut /FLT3-ITD-negative patients do not seem to benefit from allogeneic stem cell transplantation in first-line treatment; however, this issue is still under evaluation, further clinical trials are ongoing, and also minimal residual disease (MRD) has to be considered in treatment decision. 3,4 The functional role of NPM1 mut for the improved clinical outcome is still under evaluation. Immune responses to NPM1 mut may contribute to favorable prognosis of this AML subtype. Recently, we described specific T-cell responses of CD4 1 and CD8 1 T cells against epitopes derived from mutated regions of NPM1. 5 Two NPM1 mut -derived peptides, called #1 and #3, induced specific T-cell responses in patients with NPM1 mut (33% and 44%, respectively). NPM1 mut AML patients showed a significantly higher frequency of CTL responses against peptide #3 compared with healthy volunteers (P 5 .046).5 Several leukemia-associated antigens (LAAs) have been defined, most importantly RHAMM, Proteinase 3, and Wilms' tumor antigen 1 (WT-1). These antigens were tested in clinical peptide vaccination trials. 6 Immunologic and clinical responses were detected in patients with different hematologic malignancies. 7,8 Berneman et al 9 discussed NPM1 mut as a further important LAA to attack AML and leukemic stem cells by autologous T cells.In this work, we performed survival analysis of 25 NPM1 mut patients ( Figure 1A), analyzed by enzyme-linked immunospot comparing cases with or without specific T-cell responses. Our data suggest a better overall survival of patients with specific CTL responses against peptide #1 or #3 (P 5 .004; Figure 1B).Immune responses seem to differ in dependence on the epitopes (P = .026; Figure 1C), although this finding has to be interpreted with caution due to the low number of patients. The survival rate of all NPM1 mut patients is lower due to other molecular alterations (like FLT3-ITD in 11 of 25 NPM1 mut patients) and the inclusion of elderly patients (7 of 25 were older than 60 years of age). Due to its exquisite specificity in leukemia, NPM1 mut might constitute an ideal target structure for individualized immunotherapeutic approaches. Analysis with material from larger controlled clinical trials has to be performed. Nevertheless, these data suggest...

Outcome of patients with distinct molecular genotypes and cytogenetically normal AML after allogeneic transplantation

“…In the context of alloHSCT, this is ascribed to the presence of a particular strength of the allogeneic immune response. 38 In contrast, the previously described protective role of NPM1 mut in patients bearing FLT3-ITD [13][14][15] could not be unequivocally confirmed by our data. Hence, this co-occurrence might either play no major role after alloHSCT, or the influence of NPM1 mut might be limited to patients with a low FLT3-ITD/wild-type AR.…”

Expression of putative targets of immunotherapy in acute myeloid leukemia and healthy tissues

“…We quantified total RNA expression levels (necessary but not sufficient for a targetable LAA) but did not provide information on protein expression or epitope processing and presentation by MHC; these factors will be addressed in future work now that the list of candidate AML LAAs has been substantially refined to exclude those not overexpressed in AML. Neo-antigens (ie: those generated by somatic mutations including single nucleotide variations, insertions, deletions and splice variants) are an important potential class of AML LAAs that were not investigated in this work, although extensive data on these AML specific sequence changes are now available and immune responses to epitopes created by these mutations have recently been described(14). …”

Analogue peptides for the immunotherapy of human acute myeloid leukemia

“…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].…”