The contribution of the bone marrow (BM) immune microenvironment (TME) to acute myeloid leukemia (AML) development is well-known, but its prognostic significance is still elusive. Indoleamine 2,3-dioxygenase 1 (IDO1), which is negatively regulated by the BIN1 proto-oncogene, is an interferon (IFN)-γ-inducible mediator of immune tolerance. With the aim to develop a prognostic IDO1-based immune gene signature, biological and clinical data of 732 patients with newly diagnosed, non-promyelocytic AML were retrieved from public datasets and analyzed using established computational pipelines. Targeted transcriptomic profiles of 24 diagnostic BM samples were analyzed using the NanoString's nCounter platform. BIN1 and IDO1 were inversely correlated and individually predicted overall survival. PLXNC1, a semaphorin receptor involved in inflammation and immune response, was the IDO1-interacting gene retaining the strongest prognostic value. The incorporation of PLXNC1 into the 2-gene IDO1-BIN1 score gave rise to a powerful immune gene signature predicting survival, especially in patients receiving chemotherapy. The top differentially expressed genes between IDO1low and IDO-1high and between PLXNC1low and PLXNC1 high cases further improved the prognostic value of IDO1 providing a 7 and 10-gene immune signature, highly predictive of survival and correlating with AML mutational status at diagnosis. Taken together, our data indicate that IDO1 is pivotal for the construction of an immune gene signature predictive of survival in AML patients. Given the emerging role of immunotherapies for AML, our findings support the incorporation of immune biomarkers into current AML classification and prognostication algorithms.

The C-terminal aminoacidic sequence from NPM1-mutated protein, absent in normal human tissues, may serve as a leukemia-specific antigen and can be considered an ideal target for NPM1-mutated acute myeloid leukemia (AML) immunotherapy. Different in silico instruments and in vitro/ex vivo immunological platforms have identified the most immunogenic epitopes from NPM1-mutated protein. Spontaneous development of endogenous NPM1-mutated-specific cytotoxic T cells has been observed in patients, potentially contributing to remission maintenance and prolonged survival. Genetically engineered T cells, namely CAR-T or TCR-transduced T cells, directed against NPM1-mutated peptides bound to HLA could prospectively represent a promising therapeutic approach. Although either adoptive or vaccine-based immunotherapies are unlikely to be highly effective in patients with full-blown leukemia, these strategies, potentially in combination with immune-checkpoint inhibitors, could be promising in maintaining remission or preemptively eradicating persistent measurable residual disease, mainly in patients ineligible for allogeneic hematopoietic stem cell transplant (HSCT). Alternatively, neoantigen-specific donor lymphocyte infusion derived from healthy donors and targeting NPM1-mutated protein to selectively elicit graft-versus-leukemia effect may represent an attractive option in subjects experiencing post-HSCT relapse. Future studies are warranted to further investigate dynamics of NPM1-mutated-specific immunity and explore whether novel individualized immunotherapies may have potential clinical utility in NPM1-mutated AML patients.

Introduction Clinical response and chemosensitivity of relapse or refractory AML patients were evaluated after rescue and bridge‐to‐transplant MEC (mitoxantrone, etoposide, and cytarabine) regimen. Methods and Patients Fifty‐five consecutive AML patients were treated with MEC from 2009 to 2018. Chemosensitivity was evaluated by WT1 quantification. Results 27/55 patients (49.1%) had AML resistant to induction and 28/55 patients (50.9%) had AML relapse. 25/55 patients (45.5%) achieved a CR after one course of MEC, and 12 patients (21.8%) achieved WT1 negativity. In 12 patients, a second MEC was administered. Four out of 12 patients improved significantly their response with the 2nd MEC. MEC was an effective bridge to transplant, 32/55 patients (58.2%) received an allogenic stem cell transplant. Median overall survival (OS) from MEC was 455 days (95% CI 307‐602 days.); patient with WT1 negative CR had the best OS (P<.000). Conclusion WT1 is a useful marker of chemosensitivity after MEC as rescue and bridge‐to‐transplant therapy.

Acute myeloid leukemia (AML) carrying inv(16)/t(16;16), resulting in fusion transcript CBFB-MYH11, belongs to the favorable-risk category. However, even if most patients obtain morphological complete remission after induction, approximately 30% of cases eventually relapse. While well-established clinical features and concomitant cytogenetic/molecular lesions have been recognized to be relevant to predict prognosis at disease onset, the independent prognostic impact of measurable residual disease (MRD) monitoring by quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR), mainly in predicting relapse, actually supersedes other prognostic factors. Although the ELN Working Party recently indicated that patients affected with CBFB-MYH11 AML should have MRD assessment at informative clinical timepoints, at least after two cycles of intensive chemotherapy and after the end of treatment, several controversies could be raised, especially on the frequency of subsequent serial monitoring, the most significant MRD thresholds (most commonly 0.1%) and on the best source to be analyzed, namely, bone marrow or peripheral blood samples. Moreover, persisting low-level MRD positivity at the end of treatment is relatively common and not predictive of relapse, provided that transcript levels remain stably below specific thresholds. Rising MRD levels suggestive of molecular relapse/progression should thus be confirmed in subsequent samples. Further prospective studies would be required to optimize post-remission monitoring and to define effective MRD-based therapeutic strategies.