Clinical implications of myeloid malignancy‑related somatic mutations in aplastic anemia

Hematopoietic stem cell transplantation and immunosuppressive therapy: implications of clonal haematopoiesis

Aplastic anemia (AA) is a life-threatening bone marrow failure syndrome. The advent of next-generation sequencing (NGS) has shed light on the link between somatic mutations (SM) and the efficacy of immunosuppressive therapy (IST) in AA patients. However, the relationship between SM and hematopoietic stem cell transplantation (HSCT) has not been extensively explored. In this retrospective analysis, we examined 166 AA patients who received HSCT or IST at our institution between May 2019 and December 2023. NGS was conducted on 66 genes within bone marrow cells to investigate the correlation between SM and the prognosis and therapeutic response in AA patients, as well as to assess the impact of mutation types on HSCT outcomes. Clinical data were gathered from 166 AA patients, comprising 84 males and 82 females, with a median age of 32 years (ranging from 9 to 75 years). In our study, a total of 151 somatic mutations were identified across 84 patients (50.6%), with 42 patients (25.3%) presenting a single mutation and 26 patients (15.7%) harboring two mutations. The top five genes with the highest mutation frequency were BCOR/BCORL1 (12.6%), ASXL1 (8.6%), TET2 (6.6%), CEBPA (5.3%), and GATA2 (4.6%). We stratified patients into SM and No-SM groups based on the presence of mutations and further divided them into HSCT and IST groups to assess the influence of mutation types on treatment response and survival within and between these groups. The findings were as follows: 1.Patients in the HSCT group exhibited a higher treatment response (OR 85.9% vs. 68.4%, p < 0.05), although there was no significant difference in survival. 2.Patients with favorable mutations, such as PIGA and BCOR/BCORL1, experienced significantly improved response and survival compared to those with unfavorable mutations like ASXL1, DNMT3A, and TET2 (OR 93.7% vs. 72%, p < 0.05) (3-year OS 93.7% vs. 80%, p > 0.05). 3.The HSCT-Favorable group demonstrated superior response rates (OR 100% vs. 67.7%, p < 0.05) and longer survival (3-year OS 100% vs. 67.7%, p < 0.05) compared to the IST-Favorable group. This study underscores that AA patients carrying favorable mutations, particularly BCOR/BCORL1, tend to have a more robust response and better prognosis than those without mutations or those with unfavorable mutations, such as ASXL1/DNMT3A. These findings are especially pertinent to HSCT, highlighting the importance of NGS prior to initiating treatment.

When inflammatory stressors dramatically change, disease phenotypes may transform between autoimmune hematopoietic failure and myeloid neoplasms

Aplastic anemia (AA) and hypoplastic myelodysplastic syndrome are paradigms of autoimmune hematopoietic failure (AHF). Myelodysplastic syndrome and acute myeloid leukemia are unequivocal myeloid neoplasms (MNs). Currently, AA is also known to be a clonal hematological disease. Genetic aberrations typically observed in MNs are detected in approximately one-third of AA patients. In AA patients harboring MN-related genetic aberrations, a poor response to immunosuppressive therapy (IST) and an increased risk of transformation to MNs occurring either naturally or after IST are predicted. Approximately 10%-15% of patients with severe AA transform the disease phenotype to MNs following IST, and in some patients, leukemic transformation emerges during or shortly after IST. Phenotypic transformations between AHF and MNs can occur reciprocally. A fraction of advanced MN patients experience an aplastic crisis during which leukemic blasts are repressed. The switch that shapes the disease phenotype is a change in the strength of extramedullary inflammation. Both AHF and MNs have an immune-active bone marrow (BM) environment (BME). In AHF patients, an inflamed BME can be evoked by infiltrated immune cells targeting neoplastic molecules, which contributes to the BM-specific autoimmune impairment. Autoimmune responses in AHF may represent an antileukemic mechanism, and inflammatory stressors strengthen antileukemic immunity, at least in a significant proportion of patients who have MN-related genetic aberrations. During active inflammatory episodes, normal and leukemic hematopoieses are suppressed, which leads to the occurrence of aplastic cytopenia and leukemic cell regression. The successful treatment of underlying infections mitigates inflammatory stress-related antileukemic activities and promotes the penetration of leukemic hematopoiesis. The effect of IST is similar to that of treating underlying infections. Investigating inflammatory stress-powered antileukemic immunity is highly important in theoretical studies and clinical practice, especially given the wide application of immune-activating agents and immune checkpoint inhibitors in the treatment of hematological neoplasms.