Overlapping features of therapy-related and de novo NPM1-mutated AML

Medicinal chemistry aspects of fat mass and obesity associated protein: structure, function and inhibitors

Adiposity and obesity-related proteins (FTO), the earliest identified mRNA N6-methyladenosine (m6A) demethylases, are known to play crucial roles in several biological processes. Therefore, FTO is a promising target for anticancer treatment. Understanding the biological functions and regulatory mechanisms of FTO targets can serve as guidelines for drug development. Despite significant efforts to develop FTO inhibitors, no specific small-molecule inhibitors have entered clinical trials so far. In this manuscript, we review the relationship between FTO and various cancers, the small-molecule inhibitors developed against FTO targets from the perspective of medicinal chemistry and other fields, and describe their structural optimization process and structure-activity relationship, providing clues for their future development direction.

Transforming growth factor-β1 and vascular endothelial growth factor levels in senile acute myeloid leukemia and correlation with prognosis

BACKGROUND

Acute myeloid leukemia (AML) is a disease in which immature hematopoietic cells accumulate in the bone marrow and continuously expand, inhibiting hematopoiesis. The treatment and prognosis of this disease have always been unsatisfactory.

AIM

To investigate the correlation between vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGFβ1) expression and prognosis in older adults with AML.

METHODS

This study enrolled 80 patients with AML (AML group), including 36 with complete response (AML-CR), 23 with partial response (AML-PR), and 21 with no response (AML-NR). The expression levels of VEGF and TGFβ1 were detected by reverse transcription polymerase chain reaction in bone marrow mononuclear cells isolated from 56 healthy controls. Kaplan-Meier analysis was performed to assess overall survival (OS) and progression- or disease-free survival (DFS). Prognostic risk factors were analyzed using a Cox proportional hazards model.

RESULTS

The AML group showed a VEGF level of 2.68 ± 0.16. VEGF expression was lower in patients with AML-CR than those with AML-PR or AML-NR (P < 0.05). TGFβ1 expression in the AML group was 0.33 ± 0.05. Patients with AML-CR showed a higher TGFβ1 expression than those with AML-PR or AML-NR (P < 0.05). VEGF and TGFβ1 expression in patients with AML was significantly correlated with the counts of leukocytes, platelets, hemoglobin, and peripheral blood immature cells (P < 0.05); Kaplan-Meier survival analysis revealed that patients with high TGFβ1 expression had better OS and DFS than those with low TGFβ1 expression (P < 0.05), whereas patients with low VEGF levels showed better OS and DFS than those with high VEGF levels (P < 0.05). VEGF, TGFβ1, and platelet count were identified by the Cox proportional hazards model as independent risk factors for OS (P < 0.05), while VEGF, TGFβ1, and white blood cell count were independent risk factors for DFS (P < 0.05).

CONCLUSION

Decreased VEGF expression and increased TGFβ1 expression in patients with AML provide valuable references for determining and individualizing clinical treatment strategies.

Updates in biology, classification, and management of acute myeloid leukemia with antecedent hematologic disorder and therapy related acute myeloid leukemia

Acute myeloid leukemia with antecedent hematologic disorder (AHD-AML) and therapy related AML (t-AML) constitute a heterogenous disease with inferior outcomes. It is often characterized by high-risk cytogenetic and molecular alterations associated with AHD or prior cancer therapy. Historically, the standard of care treatment has been intensive induction with "7 + 3", with an improved overall response rate and survival with CPX-351. Results from large registry-based studies suggested that allogeneic hematopoietic stem cell transplant is preferable to consolidation chemotherapy alone for achieving long-term survival in patients with AHD-AML. Prevalence of high-risk genetic features and advanced age and comorbidities in patients make AHD-AML and t-AML clinically challenging subgroups to treat with intensive approaches. Recent reports on less intensive treatment options, particularly the hypomethylating agent-venetoclax combination, have shown encouraging response rates in these patients. However, emerging resistance mechanisms compromise duration of response and overall survival. Several novel agents targeting apoptotic machinery, signaling pathways, and immune checkpoints are under clinical investigation, with an aim to truly improve overall outcomes in this subgroup. We reviewed updates in biology, classification, and clinical data comparing safety and efficacy of intensive and less intensive treatment options, and summarized ongoing studies with promising novel therapies in AHD-AML and t-AML.

Monocytic Differentiation in Acute Myeloid Leukemia Cells: Diagnostic Criteria, Biological Heterogeneity, Mitochondrial Metabolism, Resistance to and Induction by Targeted Therapies

We review the importance of monocytic differentiation and differentiation induction in non-APL (acute promyelocytic leukemia) variants of acute myeloid leukemia (AML), a malignancy characterized by proliferation of immature myeloid cells. Even though the cellular differentiation block is a fundamental characteristic, the AML cells can show limited signs of differentiation. According to the French-American-British (FAB-M4/M5 subset) and the World Health Organization (WHO) 2016 classifications, monocytic differentiation is characterized by morphological signs and the expression of specific molecular markers involved in cellular communication and adhesion. Furthermore, monocytic FAB-M4/M5 patients are heterogeneous with regards to cytogenetic and molecular genetic abnormalities, and monocytic differentiation does not have any major prognostic impact for these patients when receiving conventional intensive cytotoxic therapy. In contrast, FAB-M4/M5 patients have decreased susceptibility to the Bcl-2 inhibitor venetoclax, and this seems to be due to common molecular characteristics involving mitochondrial regulation of the cellular metabolism and survival, including decreased dependency on Bcl-2 compared to other AML patients. Thus, the susceptibility to Bcl-2 inhibition does not only depend on general resistance/susceptibility mechanisms known from conventional AML therapy but also specific mechanisms involving the molecular target itself or the molecular context of the target. AML cell differentiation status is also associated with susceptibility to other targeted therapies (e.g., CDK2/4/6 and bromodomain inhibition), and differentiation induction seems to be a part of the antileukemic effect for several targeted anti-AML therapies. Differentiation-associated molecular mechanisms may thus become important in the future implementation of targeted therapies in human AML.

Monocytic Differentiation of Human Acute Myeloid Leukemia Cells: A Proteomic and Phosphoproteomic Comparison of FAB-M4/M5 Patients with and without Nucleophosmin 1 Mutations

Even though morphological signs of differentiation have a minimal impact on survival after intensive cytotoxic therapy for acute myeloid leukemia (AML), monocytic AML cell differentiation (i.e., classified as French/American/British (FAB) subtypes M4/M5) is associated with a different responsiveness both to Bcl-2 inhibition (decreased responsiveness) and possibly also bromodomain inhibition (increased responsiveness). FAB-M4/M5 patients are heterogeneous with regard to genetic abnormalities, even though monocytic differentiation is common for patients with Nucleophosmin 1 (NPM1) insertions/mutations; to further study the heterogeneity of FAB-M4/M5 patients we did a proteomic and phosphoproteomic comparison of FAB-M4/M5 patients with (n = 13) and without (n = 12) NPM1 mutations. The proteomic profile of NPM1-mutated FAB-M4/M5 patients was characterized by increased levels of proteins involved in the regulation of endocytosis/vesicle trafficking/organellar communication. In contrast, AML cells without NPM1 mutations were characterized by increased levels of several proteins involved in the regulation of cytoplasmic translation, including a large number of ribosomal proteins. The phosphoproteomic differences between the two groups were less extensive but reflected similar differences. To conclude, even though FAB classification/monocytic differentiation are associated with differences in responsiveness to new targeted therapies (e.g., Bcl-2 inhibition), our results shows that FAB-M4/M5 patients are heterogeneous with regard to important biological characteristics of the leukemic cells.

[Efficacy and prognostic factors of allogeneic hematopoietic stem cell transplantation in the treatment of secondary acute myeloid leukemia]

Objective: To evaluate the efficacy and prognostic factors of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with secondary acute myeloid leukemia (sAML) . Methods: In this multicenter, retrospective clinical study, adult patients aged ≥18 years who underwent allo-HSCT for sAML at four centers of the Zhejiang Hematopoietic Stem Cell Transplantation Collaborative Group from January 2014 to November 2022 were included, and the efficacy and prognostic factors of allo-HSCT were analyzed. Results: A total of 95 patients were enrolled; 66 (69.5%) had myelodysplastic syndrome-acute myeloid leukemia (MDS-AML) , 4 (4.2%) had MDS/MPN-AML, and 25 (26.3%) had therapy-related AML (tAML) . The 3-year CIR, LFS, and overall survival (OS) rates were 18.6% (95% CI 10.2%-27.0%) , 70.6% (95% CI 60.8%-80.4%) , and 73.3% (95% CI 63.9%-82.7%) , respectively. The 3-year CIRs of the M-AML group (including MDS-AML and MDS/MPN-AML) and the tAML group were 20.0% and 16.4%, respectively (P=0.430) . The 3-year LFSs were 68.3% and 75.4%, respectively (P=0.176) . The 3-year OS rates were 69.7% and 75.4%, respectively (P=0.233) . The 3-year CIRs of the groups with and without TP53 mutations were 60.0% and 13.7%, respectively (P=0.003) ; the 3-year LFSs were 20.0% and 76.5%, respectively (P=0.002) ; and the 3-year OS rates were 40.0% and 77.6%, respectively (P=0.002) . According to European LeukmiaNet 2022 (ELN2022) risk stratification, the 3-year CIRs of patients in the low-, intermediate-, and high-risk groups were 8.3%, 17.8%, and 22.6%, respectively (P=0.639) . The three-year LFSs were 91.7%, 69.5%, and 65.6%, respectively (P=0.268) . The 3-year OS rates were 91.7%, 71.4%, and 70.1%, respectively (P=0.314) . Multivariate analysis revealed that advanced disease at allo-HSCT and TP53 mutations were independent risk factors for CIR, LFS, and OS. Conclusion: There was no significant difference in the prognosis of patients who underwent allo-HSCT among the MDS-AML, MDS/MPN-AML, and tAML groups. Advanced disease at transplantation and TP53 mutations were poor prognostic factors. ELN2022 risk stratification had limited value for predicting the prognosis of patients with sAML following allo-HSCT.

Criteria for Diagnosis and Molecular Monitoring of NPM1-Mutated AML

NPM1-mutated acute myeloid leukemia (AML) represents the largest molecular subgroup of adult AML. NPM1-mutated AML is recognizable by molecular techniques and immunohistochemistry, which, when combined, can solve difficult diagnostic problems (including identification of myeloid sarcoma and NPM1 mutations outside exon 12). According to updated 2022 European LeukemiaNet (ELN) guidelines, determining the mutational status of NPM1 (and FLT3) is a mandatory step for the genetic-based risk stratification of AML. Monitoring of measurable residual disease (MRD) by qRT-PCR, combined with ELN risk stratification, can guide therapeutic decisions at the post-remission stage. Here, we review the criteria for appropriate diagnosis and molecular monitoring of NPM1-mutated AML.

SIGNIFICANCE

NPM1-mutated AML represents a distinct entity in the 2022 International Consensus Classification and 5th edition of World Health Organization classifications of myeloid neoplasms. The correct diagnosis of NPM1-mutated AML and its distinction from other AML entities is extremely important because it has clinical implications for the management of AML patients, such as genetic-based risk stratification according to 2022 ELN. Monitoring of MRD by qRT-PCR, combined with ELN risk stratification, can guide therapeutic decisions at the post-remission stage, e.g., whether or not to perform allogeneic hematopoietic stem cell transplantation.

Interaction between myelodysplasia-related gene mutations and ontogeny in acute myeloid leukemia

Accurate classification and risk stratification are critical for clinical decision making in patients with acute myeloid leukemia (AML). In the newly proposed World Health Organization and International Consensus classifications of hematolymphoid neoplasms, the presence of myelodysplasia-related (MR) gene mutations is included as 1 of the diagnostic criteria for AML, AML-MR, based largely on the assumption that these mutations are specific for AML with an antecedent myelodysplastic syndrome. ICC also prioritizes MR gene mutations over ontogeny (as defined in the clinical history). Furthermore, European LeukemiaNet (ELN) 2022 stratifies these MR gene mutations into the adverse-risk group. By thoroughly annotating a cohort of 344 newly diagnosed patients with AML treated at the Memorial Sloan Kettering Cancer Center, we show that ontogeny assignments based on the database registry lack accuracy. MR gene mutations are frequently observed in de novo AML. Among the MR gene mutations, only EZH2 and SF3B1 were associated with an inferior outcome in the univariate analysis. In a multivariate analysis, AML ontogeny had independent prognostic values even after adjusting for age, treatment, allo-transplant and genomic classes or ELN risks. Ontogeny also helped stratify the outcome of AML with MR gene mutations. Finally, de novo AML with MR gene mutations did not show an adverse outcome. In summary, our study emphasizes the importance of accurate ontogeny designation in clinical studies, demonstrates the independent prognostic value of AML ontogeny, and questions the current classification and risk stratification of AML with MR gene mutations.

NPM1-mutated acute myeloid leukemia: New pathogenetic and therapeutic insights and open questions

The nucleophosmin (NPM1) gene encodes for a multifunctional chaperone protein that is localized in the nucleolus but continuously shuttles between the nucleus and cytoplasm. NPM1 mutations occur in about one-third of AML, are AML-specific, usually involve exon 12 and are frequently associated with FLT3-ITD, DNMT3A, TET2, and IDH1/2 mutations. Because of its unique molecular and clinico-pathological features, NPM1-mutated AML is regarded as a distinct leukemia entity in both the International Consensus Classification (ICC) and the 5th edition of the World Health Organization (WHO) classification of myeloid neoplasms. All NPM1 mutations generate leukemic mutants that are aberrantly exported in the cytoplasm of the leukemic cells and are relevant to the pathogenesis of the disease. Here, we focus on recently identified functions of the NPM1 mutant at chromatin level and its relevance in driving HOX/MEIS gene expression. We also discuss yet controversial issues of the ICC/WHO classifications, including the biological and clinical significance of therapy-related NPM1-mutated AML and the relevance of blasts percentage in defining NPM1-mutated AML. Finally, we address the impact of new targeted therapies in NPM1-mutated AML with focus on CAR T cells directed against NPM1/HLA neoepitopes, as well as XPO1 and menin inhibitors.

Therapy-related Myeloid Neoplasms: Considerations for Patients' Clinical Evaluation

Therapy-related myeloid neoplasms (t-MNs) encompass a specific sub-group of myeloid malignancies arising after exposure to radio/cytotoxic agents for the treatment of unrelated diseases. Such malignancies present unique features, including advanced age, high comorbidities burden, and unfavorable genetic profiles. All these features justify the need for a specific diagnostic work-up and dedicated treatment algorithms. However, as new classification systems recognize the unique clinical characteristics exhibited by t-MN patients, how to assess fitness status in this clinical setting is largely unexplored. Optimizing fitness assessment would be crucial in the management of t-MN patients, considering that factors usually contributing to a worse or better outcome (like age, comorbidities, and treatment history) are patient-specific. In the absence of specific tools for fitness assessment in this peculiar category of AML, the aim of this review is to describe all those factors related to patient, treatment, and disease that allow planning treatments with an optimal risk/benefit ratio.

Prognostic impact of secondary versus de novo ontogeny in acute myeloid leukemia is accounted for by the European LeukemiaNet 2022 risk classification

Secondary AML (sAML), defined by either history of antecedent hematologic disease (AHD) or prior genotoxic therapy (tAML), is classically regarded as having worse prognosis than de novo disease (dnAML). Clinicians may infer a new AML diagnosis is secondary based on a history of antecedent blood count (ABC) abnormalities in the absence of known prior AHD, but whether abnormal ABCs are associated with worse outcomes is unclear. Secondary-type mutations have recently been incorporated into the European LeukemiaNet (ELN) 2022 guidelines as adverse-risk features, raising the question of whether clinical descriptors of ontogeny (i.e., de novo or secondary) are prognostically significant when accounting for genetic risk by ELN 2022. In a large multicenter cohort of patients (n = 734), we found that abnormal ABCs are not independently prognostic after adjusting for genetic characteristics in dnAML patients. Furthermore, history of AHD and tAML do not confer increased risk of death compared to dnAML on multivariate analysis, suggesting the prognostic impact of ontogeny is accounted for by disease genetics as stratified by ELN 2022 risk and TP53 mutation status. These findings emphasize the importance that disease genetics should play in risk stratification and clinical trial eligibility in AML.

Standardising acute myeloid leukaemia classification systems: a perspective from a panel of international experts

The existence of two acute myeloid leukaemia classification systems-one put forth by WHO and one by the International Consensus Classification in 2022-is concerning. Although both systems appropriately move towards genomic disease definitions and reduced emphasis on blast enumeration, there are consequential disagreements between the two systems on what constitutes a diagnosis of acute myeloid leukaemia. This fundamental problem threatens the ability of heath-care providers to diagnose acute myeloid leukaemia, communicate with patients and other health-care providers, and deliver appropriate and consistent management strategies for patients with the condition. Clinical trial eligibility, standardised response assessments, and eventual drug development and regulatory pathways might also be negatively affected by the discrepancies. In this Viewpoint, we review the merits and limitations of both classification systems and illustrate how the coexistence, as well as application of both systems is an undue challenge to patients, clinicians, hematopathologists, sponsors of research, and regulators. Lastly, we emphasise the urgency and propose a roadmap, by which the two divergent classification systems can be harmonised.

Vacuolar ATPase Is a Possible Therapeutic Target in Acute Myeloid Leukemia: Focus on Patient Heterogeneity and Treatment Toxicity

Vacuolar ATPase (V-ATPase) is regarded as a possible target in cancer treatment. It is expressed in primary acute myeloid leukemia cells (AML), but the expression varies between patients and is highest for patients with a favorable prognosis after intensive chemotherapy. We therefore investigated the functional effects of two V-ATPase inhibitors (bafilomycin A1, concanamycin A) for primary AML cells derived from 80 consecutive patients. The V-ATPase inhibitors showed dose-dependent antiproliferative and proapoptotic effects that varied considerably between patients. A proteomic comparison of primary AML cells showing weak versus strong antiproliferative effects of V-ATPase inhibition showed a differential expression of proteins involved in intracellular transport/cytoskeleton functions, and an equivalent phosphoproteomic comparison showed a differential expression of proteins that regulate RNA processing/function together with increased activity of casein kinase 2. Patients with secondary AML, i.e., a heterogeneous subset with generally adverse prognosis and previous cytotoxic therapy, myeloproliferative neoplasia or myelodysplastic syndrome, were characterized by a strong antiproliferative effect of V-ATPase inhibition and also by a specific mRNA expression profile of V-ATPase interactome proteins. Furthermore, the V-ATPase inhibition altered the constitutive extracellular release of several soluble mediators (e.g., chemokines, interleukins, proteases, protease inhibitors), and increased mediator levels in the presence of AML-supporting bone marrow mesenchymal stem cells was then observed, especially for patients with secondary AML. Finally, animal studies suggested that the V-ATPase inhibitor bafilomycin had limited toxicity, even when combined with cytarabine. To conclude, V-ATPase inhibition has antileukemic effects in AML, but this effect varies between patients.

Modern Risk Stratification of Acute Myeloid Leukemia in 2023: Integrating Established and Emerging Prognostic Factors

An accurate estimation of AML prognosis is complex since it depends on patient-related factors, AML manifestations at diagnosis, and disease genetics. Furthermore, the depth of response, evaluated using the level of MRD, has been established as a strong prognostic factor in several AML subgroups. In recent years, this rapidly evolving field has made the prognostic evaluation of AML more challenging. Traditional prognostic factors, established in cohorts of patients treated with standard intensive chemotherapy, are becoming less accurate as new effective therapies are emerging. The widespread availability of next-generation sequencing platforms has improved our knowledge of AML biology and, consequently, the recent ELN 2022 recommendations significantly expanded the role of new gene mutations. However, the impact of rare co-mutational patterns remains to be fully disclosed, and large international consortia such as the HARMONY project will hopefully be instrumental to this aim. Moreover, accumulating evidence suggests that clonal architecture plays a significant prognostic role. The integration of clinical, cytogenetic, and molecular factors is essential, but hierarchical methods are reaching their limit. Thus, innovative approaches are being extensively explored, including those based on "knowledge banks". Indeed, more robust prognostic estimations can be obtained by matching each patient's genomic and clinical data with the ones derived from very large cohorts, but further improvements are needed.

Allogeneic hematopoietic stem cell transplantation and pre-transplant strategies in patients with NPM1-mutated acute myeloid leukemia: a single center experience

Patients with acute myeloid leukemia (AML) and nucleophosmin 1 gene mutations (NPM1mut) show a favorable prognosis with chemotherapy (CT) in the absence of negative prognostic genetic abnormalities. Between 2008 and 2021 64 patients with NPM1mutAML received alloHSCT because of additional adverse prognostic factors (1st line), inadequate response to or relapse during or after CT (2nd line). To expand the evidence in alloTX in NPM1mut AML, clinical and molecular data were retrospectively analyzed with respect to pre-transplant strategies and outcome. Patients with minimal residual disease negative (MRD-) CR at transplant had better 2-y-PFS and 2-y-OS (77% and 88%) than patients with minimal residual disease positive (MRD+) CR (41% and 71%) or patients with active disease (AD) at transplant (20% and 52%). The 2nd line patients with relapse after completing CT responded well to high dose cytarabine based salvage chemotherapy (salvage CT) in contrast to patients relapsing while still on CT (90% vs 20%, P = 0.0170). 2-y-PFS and 2-y-OS was 86% in patients who achieved a 2nd MRD- CR pre alloHSCT. Outcome in NPM1mutAML depends on disease burden at alloHSCT. Time and type of relapse in relation to CT are predictive for response to salvage CT.

Genetic, Phenotypic, and Clinical Heterogeneity of NPM1-Mutant Acute Myeloid Leukemias

The current classification of acute myeloid leukemia (AML) relies largely on genomic alterations. AML with mutated nucleophosmin 1 (NPM1-mut) is the largest of the genetically defined groups, involving about 30% of adult AMLs and is currently recognized as a distinct entity in the actual AML classifications. NPM1-mut AML usually occurs in de novo AML and is associated predominantly with a normal karyotype and relatively favorable prognosis. However, NPM1-mut AMLs are genetically, transcriptionally, and phenotypically heterogeneous. Furthermore, NPM1-mut is a clinically heterogenous group. Recent studies have in part clarified the consistent heterogeneities of these AMLs and have strongly supported the need for an additional stratification aiming to improve the therapeutic response of the different subgroups of NPM1-mut AML patients.

NPM1-Mutated Acute Myeloid Leukemia: Recent Developments and Open Questions

Somatic mutations in the nucleophosmin (NPM1) gene occur in approximately 30% of de novo acute myeloid leukemias (AMLs) and are relatively enriched in normal karyotype AMLs. Earlier World Health Organization (WHO) classification schema recognized NPM1-mutated AMLs as a unique subtype of AML, while the latest WHO and International Consensus Classification (ICC) now consider NPM1 mutations as AML-defining, albeit at different blast count thresholds. NPM1 mutational load correlates closely with disease status, particularly in the post-therapy setting, and therefore high sensitivity-based methods for detection of the mutant allele have proven useful for minimal/measurable residual disease (MRD) monitoring. MRD status has been conventionally measured by either multiparameter flow cytometry (MFC) and/or molecular diagnostic techniques, although recent data suggest that MFC data may be potentially more challenging to interpret in this AML subtype. Of note, MRD status does not predict patient outcome in all cases, and therefore a deeper understanding of the biological significance of MRD may be required. Recent studies have confirmed that NPM1-mutated cells rely on overexpression of HOX/MEIS1, which is dependent on the presence of the aberrant cytoplasmic localization of mutant NPM1 protein (NPM1c); this biology may explain the promising response to novel agents, including menin inhibitors and second-generation XPO1 inhibitors. In this review, these and other recent developments around NPM1-mutated AML, in addition to open questions warranting further investigation, will be discussed.