Can we predict responsiveness to hypomethylating agents in AML?

Epigenetic Therapies in Triple-Negative Breast Cancer: Concepts, Visions, and Challenges

Breast cancer, the most frequent malignancy in women worldwide, is a molecularly and clinically very heterogeneous disease. Triple-negative breast cancer is defined by the absence of hormone receptor and growth factor receptor ERBB2/HER2 expression. It is characterized by a more aggressive course of disease and a shortage of effective therapeutic approaches. Hallmarks of cancer cells are not only genetic alterations, but also epigenetic aberrations. The most studied and best understood alterations are methylation of the DNA base cytosine and the covalent modification of histone proteins. The reversibility of these covalent modifications make them attractive targets for therapeutic intervention, as documented in numerous ongoing clinical trials. Epidrugs, targeting DNA methylation and histone modifications, might offer attractive new options in treating triple-negative breast cancer. Currently, the most promising options are combination therapies in which the epidrug increases the efficiency of immuncheckpoint inhibitors. This review focusses exclusively on DNA methylation and histone modifications. In reviewing the knowledge about epigenetic therapies in breast cancer, and especially triple-negative breast cancer, the focus is on explaining concepts and raising awareness of what is not yet known and what has to be clarified in the future.

Single-cell Multiomics Analysis of Myelodysplastic Syndromes and Clinical Response to Hypomethylating Therapy

Alterations in epigenetic marks, such as DNA methylation, represent a hallmark of cancer that has been successfully exploited for therapy in myeloid malignancies. Hypomethylating agents (HMA), such as azacitidine, have become standard-of-care therapy to treat myelodysplastic syndromes (MDS), myeloid neoplasms that can evolve into acute myeloid leukemia. However, our capacity to identify who will respond to HMAs, and the duration of response, remains limited. To shed light on this question, we have leveraged the unprecedented analytic power of single-cell technologies to simultaneously map the genome and immunoproteome of MDS samples throughout clinical evolution. We were able to chart the architecture and evolution of molecular clones in precious paired bone marrow MDS samples at diagnosis and posttreatment to show that a combined imbalance of specific cell lineages with diverse mutational profiles is associated with the clinical response of patients with MDS to hypomethylating therapy.

SIGNIFICANCE

MDS are myeloid clonal hemopathies with a low 5-year survival rate, and approximately half of the cases do not respond to standard HMA therapy. Our innovative single-cell multiomics approach offers valuable biological insights and potential biomarkers associated with the demethylating agent efficacy. It also identifies vulnerabilities that can be targeted using personalized combinations of small drugs and antibodies.

Transcriptional and phenotypic heterogeneity underpinning venetoclax resistance in AML

The venetoclax BCL2 inhibitor in combination with hypomethylating agents represents a cornerstone of induction therapy for older AML patients, unfit for intensive chemotherapy. Like other targeted therapies, venetoclax-based therapies suffer from innate and acquired resistance. While several mechanisms of resistance have been identified, the heterogeneity of resistance mechanism across patient populations is poorly understood. Here we utilized integrative analysis of transcriptomic and ex-vivo drug response data in AML patients to identify four transcriptionally distinct VEN resistant clusters (VR_C1-4), with distinct phenotypic, genetic and drug response patterns. VR_C1 was characterized by enrichment for differentiated monocytic- and cDC-like blasts, transcriptional activation of PI3K-AKT-mTOR signaling axis, and energy metabolism pathways. They showed sensitivity to mTOR and CDK inhibition. VR_C2 was enriched for NRAS mutations and associated with distinctive transcriptional suppression of HOX expression. VR_C3 was characterized by enrichment for TP53 mutations and higher infiltration by cytotoxic T cells. This cluster showed transcriptional expression of erythroid markers, suggesting tumor cells mimicking erythroid differentiation, activation of JAK-STAT signaling, and sensitivity to JAK inhibition, which in a subset of cases synergized with venetoclax. VR_C4 shared transcriptional similarities with venetoclax-sensitive patients, with modest over-expression of interferon signaling. They were also characterized by high rates of DNMT3A mutations. Finally, we projected venetoclax-resistance states onto single cells profiled from a patient who relapsed under venetoclax therapy capturing multiple resistance states in the tumor and shifts in their abundance under venetoclax selection, suggesting that single tumors may consist of cells mimicking multiple VR_Cs contributing to intra-tumor heterogeneity. Taken together, our results provide a strategy to evaluate inter- and intra-tumor heterogeneity of venetoclax resistance mechanisms and provide insights into approaches to navigate further management of patients who failed therapy with BCL2 inhibitors.

Spliceosome mutations are associated with clinical response in a phase 1b/2 study of the PLK1 inhibitor onvansertib in combination with decitabine in relapsed or refractory acute myeloid leukemia

PLK1 is overexpressed in acute myeloid leukemia (AML). A phase 1b trial of the PLK1 inhibitor onvansertib (ONV) combined with decitabine (DAC) demonstrated initial safety and efficacy in patients with relapsed/refractory (R/R) AML. The current study aimed to identify molecular predictors of response to ONV + DAC in R/R AML patients. A total of 44 R/R AML patients were treated with ONV + DAC and considered evaluable for efficacy. Bone marrow (BM) samples were collected at baseline for genomic and transcriptomic analysis (n = 32). A 10-gene expression signature, predictive of response to ONV + DAC, was derived from the leading-edge genes of gene set enrichment analyses (GSEA). The gene signature was evaluated in independent datasets and used to identify associated mutated genes. Twenty percent of the patients achieved complete remission, with or without hematologic count recovery (CR/CRi), and 32% exhibited a ≥50% reduction in bone marrow blasts. Patients who responded to treatment had elevated mitochondrial function and OXPHOS. The gene signature was not associated with response to DAC alone in an independent dataset. By applying the signature to the BeatAML cohort (n = 399), we identified a positive association between predicted ONV + DAC response and mutations in splicing factors (SF). In the phase 1b/2 trial, patients with SF mutations (SRSF2, SF3B1) had a higher CR/CRi rate (50%) compared to those without SF mutations (9%). PLK1 inhibition with ONV in combination with DAC could be a potential therapy in R/R AML patients, particularly those with high OXPHOS gene expression and SF mutations.

Crosstalk between DNA methylation and hypoxia in acute myeloid leukaemia

BACKGROUND

Acute myeloid leukaemia (AML) is a deadly disease characterised by the uncontrolled proliferation of immature myeloid cells within the bone marrow. Altered regulation of DNA methylation is an important epigenetic driver of AML, where the hypoxic bone marrow microenvironment can help facilitate leukaemogenesis. Thus, interactions between epigenetic regulation and hypoxia signalling will have important implications for AML development and treatment.

MAIN BODY

This review summarises the importance of DNA methylation and the hypoxic bone marrow microenvironment in the development, progression, and treatment of AML. Here, we focus on the role hypoxia plays on signalling and the subsequent regulation of DNA methylation. Hypoxia is likely to influence DNA methylation through altered metabolic pathways, transcriptional control of epigenetic regulators, and direct effects on the enzymatic activity of epigenetic modifiers. DNA methylation may also prevent activation of hypoxia-responsive genes, demonstrating bidirectional crosstalk between epigenetic regulation and the hypoxic microenvironment. Finally, we consider the clinical implications of these interactions, suggesting that reduced cell cycling within the hypoxic bone marrow may decrease the efficacy of hypomethylating agents.

CONCLUSION

Hypoxia is likely to influence AML progression through complex interactions with DNA methylation, where the therapeutic efficacy of hypomethylating agents may be limited within the hypoxic bone marrow. To achieve optimal outcomes for AML patients, future studies should therefore consider co-treatments that can promote cycling of AML cells within the bone marrow or encourage their dissociation from the bone marrow.

A Personalized Risk Model for Azacitidine Outcome in Myelodysplastic Syndrome and Other Myeloid Neoplasms Identified by Machine Learning Model Utilizing Real-World Data

Azacitidine is an approved therapy for higher-risk myelodysplastic syndrome (MDS). However, only 30-40% patients respond to azacitidine, and the responses may take up to six cycles to become evident. Delayed responses and the myelosuppressive effects of azacitidine make it challenging to predict which patients will benefit. This is further compounded by a lack of uniform prognostic tools to identify patients at risk of early treatment failure. Hence, we performed a retrospective analysis of 273 consecutive azacytidine-treated patients. The median overall survival was 16.25 months with only 9% alive at 5 years. By using pre-treatment variables incorporated into a random forest machine learning model, we successfully identified those patients unlikely to benefit from azacytidine upfront (7.99 vs. 22.8 months, p < 0.0001). This model also identified those who required significantly more hospitalizations and transfusion support. Notably, it accurately predicted survival outcomes, outperforming the existing prognostic scoring system. By integrating somatic mutations, we further refined the model and identified three distinct risk groups with significant differences in survival (5.6 vs. 10.5 vs. 43.5 months, p < 0.0001). These real-world findings emphasize the urgent need for personalized prediction tools tailored to hypomethylating agents, reducing unnecessary complications and resource utilization in MDS treatment.

In vivo kinetics of early, non-random methylome and transcriptome changes induced by DNA-hypomethylating treatment in primary AML blasts

Despite routine use of DNA-hypomethylating agents (HMAs) in AML/MDS therapy, their mechanisms of action are not yet unraveled. Pleiotropic effects of HMAs include global methylome and transcriptome changes. We asked whether in blasts and T-cells from AML patients HMA-induced in vivo demethylation and remethylation occur randomly or non-randomly, and whether gene demethylation is associated with gene induction. Peripheral blood AML blasts from patients receiving decitabine (20 mg/m² day 1-5) were serially isolated for methylome analyses (days 0, 8 and 15, n = 28) and methylome-plus-transcriptome analyses (days 0 and 8, n = 23), respectively. T-cells were isolated for methylome analyses (days 0 and 8; n = 16). We noted massive, non-random demethylation at day 8, which was variable between patients. In contrast, T-cells disclosed a thousand-fold lesser, random demethylation, indicating selectivity of the demethylation for the malignant blasts. The integrative analysis of DNA demethylation and transcript induction revealed 87 genes displaying a significant inverse correlation, e.g. the tumor suppressor gene IFI27, whose derepression was validated in two AML cell lines. These results support HMA-induced, non-random early in vivo demethylation events in AML blasts associated with gene induction. Larger patient cohorts are needed to determine whether a demethylation signature may be predictive for response to this treatment.

A machine learning model of response to hypomethylating agents in myelodysplastic syndromes

Hypomethylating agents (HMA) prolong survival and improve cytopenias in individuals with higher-risk myelodysplastic syndrome (MDS). Only 30-40% of patients, however, respond to HMAs, and responses may not occur for more than 6 months after HMA initiation. We developed a model to more rapidly assess HMA response by analyzing early changes in patients’ blood counts. Three institutions’ data were used to develop a model that assessed patients’ response to therapy 90 days after the initiation using serial blood counts. The model was developed with a training cohort of 424 patients from 2 institutions and validated on an independent cohort of 90 patients. The final model achieved an area under the receiver operating characteristic curve (AUROC) of 0.79 in the train/test group and 0.84 in the validation group. The model provides cohort-wide and individual-level explanations for model predictions, and model certainty can be interrogated to gauge the reliability of a given prediction.

•

We developed a model to more rapidly assess patients’ response to hypomethylating agents

•

The model’s predictions use exclusively routinely collected blood count data

•

The model confirmed prior findings and identified potential new prognostic factors

•

Model predictions are interpretable on both the individual and cohort-wide level

The Clinical Value of Decitabine Monotherapy in Patients with Acute Myeloid Leukemia

Decitabine (5-aza-2′-deoxycytidine) is a hypomethylating agent used in the treatment of acute myeloid leukemia (AML). Decitabine inhibits DNA methyltransferases, causing DNA hypomethylation, and leading amongst others to re-expression of silenced tumor suppressor genes. Decitabine is indicated for the treatment of adult patients with newly diagnosed de novo or secondary AML who are not eligible for standard induction chemotherapy. The initial authorization in 2012 was based on the results of the open-label, randomized, multicenter phase 3 DACO-016 trial, and supported by data from the supportive phase 2 open-label DACO-017 trial. Compared with standard care, decitabine significantly improved overall survival, event-free survival, progression-free survival, and response rate. Decitabine was generally well tolerated, offering a valuable treatment option in patients with AML irrespective of age, especially for patients achieving a complete response. Several observational “real-life” studies confirmed these results. In contrast to standard chemotherapy, the presence of adverse-risk karyotypes or TP53 mutations does not negatively impact sensitivity to hypomethylating therapy albeit with lower durability. Data suggest a potential positive effect of decitabine in patients with monosomal karyotype-positive AML. For the time being, decitabine is an appropriate option as monotherapy for patients with AML who are unfit to receive more intensive combination therapies, but emerging data suggest that decitabine-based doublet or triplet combinations may be future treatment options for patients with AML.

Gene Expression Profiles Identify Biomarkers of Resistance to Decitabine in Myelodysplastic Syndromes

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disease characterized by inefficient hematopoiesis and the potential development of acute leukemia. Among the most notable advances in the treatment of MDS is the hypomethylating agent, decitabine (5-aza-2′deoxycytidine). Although decitabine is well known as an effective method for treating MDS patients, only a subset of patients respond and a tolerance often develops, leading to treatment failure. Moreover, decitabine treatment is costly and causes unnecessary toxicity. Therefore, clarifying the mechanism of decitabine resistance is important for improving its therapeutic efficacy. To this end, we established a decitabine-resistant F-36P cell line from the parental F-36P leukemia cell line, and applied a genetic approach employing next-generation sequencing, various experimental techniques, and bioinformatics tools to determine differences in gene expression and relationships among genes. Thirty-eight candidate genes encoding proteins involved in decitabine-resistant-related pathways, including immune checkpoints, the regulation of myeloid cell differentiation, and PI3K-Akt signaling, were identified. Interestingly, two of the candidate genes, AKT3 and FOS, were overexpressed in MDS patients with poor prognoses. On the basis of these results, we are pursuing development of a gene chip for diagnosing decitabine resistance in MDS patients, with the goal of ultimately improving the power to predict treatment strategies and the prognosis of MDS patients.

Advances in acute myeloid leukemia

Acute myeloid leukemia (AML) is an uncommon but potentially catastrophic diagnosis with historically high mortality rates. The standard of care treatment remained unchanged for decades; however, recent discoveries of molecular drivers of leukemogenesis and disease progression have led to novel therapies for AML. Ongoing research and clinical trials are actively seeking to personalize therapy by identifying molecular targets, discovering patient specific and disease specific risk factors, and identifying effective combinations of modalities and drugs. This review focuses on important updates in diagnostic and disease classifications that reflect new understanding of the biology of AML, its mutational heterogeneity, some important genetic and environmental risk factors, and new treatment options including cytotoxic chemotherapy, novel targeted agents, and cellular therapies.

Hypomethylating agents (HMA) for the treatment of acute myeloid leukemia and myelodysplastic syndromes: mechanisms of resistance and novel HMA-based therapies

Aberrant DNA methylation plays a pivotal role in tumor development and progression. DNA hypomethylating agents (HMA) constitute a class of drugs which are able to reverse DNA methylation, thereby triggering the re-programming of tumor cells. The first-generation HMA azacitidine and decitabine have now been in standard clinical use for some time, offering a valuable alternative to previous treatments in acute myeloid leukemia and myelodysplastic syndromes, so far particularly in older, medically non-fit patients. However, the longer we use these drugs, the more we are confronted with the (almost inevitable) development of resistance. This review provides insights into the mode of action of HMA, mechanisms of resistance to this treatment, and strategies to overcome HMA resistance including next-generation HMA and HMA-based combination therapies.

Decitabine Induces Gene Derepression on Monosomic Chromosomes: In Vitro and In Vivo Effects in Adverse-Risk Cytogenetics AML

Hypomethylating agents (HMA) have become the backbone of nonintensive acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) treatment, also by virtue of their activity in patients with adverse genetics, for example, monosomal karyotypes, often with losses on chromosome 7, 5, or 17. No comparable activity is observed with cytarabine, a cytidine analogue without DNA-hypomethylating properties. As evidence exists for compounding hypermethylation and gene silencing of hemizygous tumor suppressor genes (TSG), we thus hypothesized that this effect may preferentially be reversed by the HMAs decitabine and azacitidine. An unbiased RNA-sequencing approach was developed to interrogate decitabine-induced transcriptome changes in AML cell lines with or without a deletion of chromosomes 7q, 5q or 17p. HMA treatment preferentially upregulated several hemizygous TSG in this genomic region, significantly derepressing endogenous retrovirus (ERV)3-1, with promoter demethylation, enhanced chromatin accessibility, and increased H3K4me3 levels. Decitabine globally reactivated multiple transposable elements, with activation of the dsRNA sensor RIG-I and interferon regulatory factor (IRF)7. Induction of ERV3-1 and RIG-I mRNA was also observed during decitabine treatment in vivo in serially sorted peripheral blood AML blasts. In patient-derived monosomal karyotype AML murine xenografts, decitabine treatment resulted in superior survival rates compared with cytarabine. Collectively, these data demonstrate preferential gene derepression and ERV reactivation in AML with chromosomal deletions, providing a mechanistic explanation that supports the clinical observation of superiority of HMA over cytarabine in this difficult-to-treat patient group. SIGNIFICANCE: These findings unravel the molecular mechanism underlying the intriguing clinical activity of HMAs in AML/MDS patients with chromosome 7 deletions and other monosomal karyotypes.See related commentary by O'Hagan et al., p. 813.

Is outcome of older people with acute myeloid leukemia improving with new therapeutic approaches and stem cell transplantation?

Introduction: The clinical outcome of older patients with acute myeloid leukemia (AML) is still poor, especially for those who are unfit to treatments aimed at altering the natural course of the disease. Hypomethylating agents (HMA) offer an important therapeutic opportunity to a consistent number of patients, but long-term results are largely unsatisfactory.Area covered: Recently, a number of new agents have been registered for AML, some of which selectively available for older patient population, with promising results in terms of response rate and survival. Furthermore, the upper age limit for allogeneic stem cell transplantation is constantly increasing, so that this procedure is offered and actually given to an increasing number of older patients with AML. A literature review was conducted of the PubMed database for articles published in English as well as for abstracts from most important and recent hematology meetings on AML in older patients.Expert opinion: Appropriate selection among different options on the basis of clinical fitness and molecular findings at diagnosis as well as at relapse would result in improvement of therapeutic results, sparing unnecessary toxicity and optimizing health systems resources.