High prevalence and allele burden-independent prognostic importance of p53 mutations in an inner-city MDS/AML cohort

Evaluating targeted therapies in older patients with TP53-mutated AML

Mutation of thetumor suppressor gene, TP53 (tumor protein 53), occurs in up to 15% of all patients with acute myeloid leukemia (AML) and is enriched within specific clinical subsets, most notably in older adults, and including secondary AML cases arising from preceding myeloproliferative neoplasm (MPN), myelodysplastic syndrome (MDS), patients exposed to prior DNA-damaging, cytotoxic therapies. In all cases, these tumors have remained difficult to effectively treat with conventional therapeutic regimens. Newer approaches fortreatmentofTP53-mutated AML have shifted to interventions that maymodulateTP53 function, target downstream molecular vulnerabilities, target non-p53 dependent molecular pathways, and/or elicit immunogenic responses. This review will describe the basic biology of TP53, the clinical and biological patterns of TP53 within myeloid neoplasms with a focus on elderly AML patients and will summarize newer therapeutic strategies and current clinical trials.

TP53-Mutated Myelodysplasia and Acute Myeloid Leukemia

TP53-mutated myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) form a distinct and heterogeneous group of myeloid malignancies associated with poor outcomes. Studies carried out in the last years have in part elucidated the complex role played by TP53 mutations in the pathogenesis of these myeloid disorders and in the mechanisms of drug resistance. A consistent number of studies has shown that some molecular parameters, such as the presence of a single or multiple TP53 mutations, the presence of concomitant TP53 deletions, the association with co-occurring mutations, the clonal size of TP53 mutations, the involvement of a single (monoallelic) or of both TP53 alleles (biallelic) and the cytogenetic architecture of concomitant chromosome abnormalities are major determinants of outcomes of patients. The limited response of these patients to standard treatments, including induction chemotherapy, hypomethylating agents and venetoclax-based therapies and the discovery of an immune dysregulation have induced a shift to new emerging therapies, some of which being associated with promising efficacy. The main aim of these novel immune and nonimmune strategies consists in improving survival and in increasing the number of TP53-mutated MDS/AML patients in remission amenable to allogeneic stem cell transplantation.

TP53 in AML and MDS: The new (old) kid on the block

MDS and AML are clonal hematopoietic stem cell disorders of increasing incidence, having a variable prognosis based, among others, on co-occurring molecular abnormalities. TP53 mutations are frequently detected in these myeloid neoplasms and portend a poor prognosis with known therapeutic resistance. This article provides a timely review of the complexity of TP53 alterations, providing updates in diagnosis and prognosis based on new 2022 International Consensus Classification (ICC) and World Health Organization (WHO) guidelines. The article addresses optimal testing strategies and reviews current and arising therapeutic approaches. While the treatment landscape for this molecular subgroup is under active development, further exploration is needed to optimize the care of this group of patients with unmet needs.

Clinical characteristics and overall survival among acute myeloid leukemia patients with TP53 gene mutation or chromosome 17p deletion

Approximately 5% to 15% of acute myeloid leukemia (AML) patients have TP53 gene mutations (TP53m), which are associated with very poor outcomes. Adults (≥18 years) with a new AML diagnosis were included from a nationwide, de-identified, real-world database. Patients receiving first-line therapy were divided into three cohorts: venetoclax (VEN) + hypomethylating agents (HMAs; Cohort A), intensive chemotherapy (Cohort B), or HMA without VEN (Cohort C). A total of 370 newly diagnosed AML patients with TP53m (n = 124), chromosome 17p deletion (n = 166), or both (n = 80) were included. The median age was 72 years (range, 24-84); most were male (59%) and White (69%). Baseline bone marrow (BM) blasts were ≤30%, 31%-50%, and >50% in 41%, 24%, and 29% of patients in Cohorts A, B, and C, respectively. BM remission (<5% blasts) with first-line therapy was reported in 54% of patients (115/215) overall, and 67% (38/57), 62% (68/110), and 19% (9/48) for respective cohorts (median BM remission duration: 6.3, 6.9, and 5.4 months). Median overall survival (95% CI) was 7.4 months (6.0-8.8) for Cohort A, 9.4 months (7.2-10.4) for Cohort B, and 5.9 months (4.3-7.5) for Cohort C. There were no differences in survival by treatment type after adjusting for the effects of relevant covariates (Cohort A vs. C adjusted hazard ratio [aHR] = 0.9; 95% CI, 0.7-1.3; Cohort A vs. B aHR = 1.0; 95% CI, 0.7-1.5; and Cohort C vs. B aHR = 1.1; 95% CI, 0.8-1.6). Patients with TP53m AML have dismal outcomes with current therapies, demonstrating the high unmet need for improved treatments.

Prediction of risk for myeloid malignancy in clonal hematopoiesis

Background

Clonal hematopoiesis of indeterminate potential (CHIP) and clonal cytopenia of undetermined significance (CCUS) are defined by somatic mutations in genes associated with myeloid neoplasms (MN) at a variant allele fraction (VAF) ≥ 0.02, in the absence and presence of cytopenia, respectively. CHIP/CCUS is highly prevalent in adults and defining predictors of MN risk would aid clinical management and research.

Methods

We analyzed sequenced exomes of healthy UK Biobank (UKB) participants (n = 438,890) in separate derivation and validation cohorts. Genetic mutations, laboratory values, and MN outcomes were used in conditional probability-based recursive partitioning and Cox regression to determine predictors of incident MN. Combined statistical weights defined a clonal hematopoiesis risk score (CHRS). Independent CHIP/CCUS patient cohorts were used to test prognostic capability of the CHRS in the clinical setting.

Results

Recursive partitioning distinguished CHIP/CCUS cases with 10-year probabilities of MN ranging from 0.0078 - 0.85. Multivariable analysis validated partitioning variables as predictors of MN. Key features, including single DNMT3A mutations, high risk mutations, ≥ 2 mutations, VAF ≥ 0.2, age ≥ 65 years, CCUS vs CHIP and red blood cell indices, influenced MN risk in variable direction. The CHRS defined low risk (n = 10018, 88.4%), intermediate risk (n = 1196, 10.5%), and high risk (n = 123, 1.1%) groups. In clinical cohorts, most MN events occurred in high risk CHIP/CCUS patients.

Conclusions

The CHRS provides simple prognostic framework for CHIP/CCUS, distinguishing a high risk minority from the majority of CHIP/CCUS which has minimal risk for progression to MN.

Review: MDMX plays a central role in leukemic transformation and may be a promising target for leukemia prevention strategies

Acute myeloid leukemia (AML) is a fatal disease resulting from preleukemic hematopoietic conditions including asymptomatic clonal hematopoiesis. The accumulation of genetic changes is one of the causes of leukemic transformation. However, nongenetic factors including the overexpression of specific genes also contribute to preleukemic to leukemic transition. Among them, the p53 inhibitor Murine Double Minute X (MDMX) plays crucial roles especially in leukemia initiation. MDMX is broadly overexpressed in vast majority of AML cases, including in hematopoietic stem/progenitor cell (HSPC) level. Recently, high expression of MDMX in HSPC has been shown to be associated with leukemic transformation in patients with myelodysplastic syndromes, and preclinical studies demonstrated that MDMX overexpression accelerates the transformation of preleukemic murine models, including models of clonal hematopoiesis. MDMX inhibition, through activation of cell-intrinsic p53 activity, shows antileukemic effects. However, the molecular mechanisms of MDMX in provoking leukemic transformation are complicated. Both p53-dependent and independent mechanisms are involved in the progression of the disease. This review discusses the canonical and noncanonical functions of MDMX and how these functions are involved in the maintenance, expansion, and progression to malignancy of preleukemic stem cells. Moreover, strategies on how leukemic transformation could possibly be prevented by targeting MDMX in preleukemic stem cells are discussed.

TP53 mutation variant allele frequency of ≥10% is associated with poor prognosis in therapy-related myeloid neoplasms

Revised diagnostic criteria for myeloid neoplasms (MN) issued by the International Consensus Classification (ICC) and the World Health Organization (WHO) recommended major change pertaining to TP53-mutated (TP53mut) MN. However, these assertions have not been specifically examined in therapy-related myeloid neoplasm (t-MN), a subset enriched with TP53mut. We analyzed 488 t-MN patients for TP53mut. At least one TP53mut with variant allele frequency (VAF) ≥ 2% with or without loss of TP53 locus was noted in 182 (37.3%) patients and 88.2% of TP53mut t-MN had a VAF ≥10%. TP53mut t-MN with VAF ≥ 10% had a distinct clinical and biological profile compared to both TP53mut VAF < 10% and wild-type TP53 (TP53wt) cases. Notably, TP53mut VAF ≥ 10% had a significantly shorter survival compared to TP53wt (8.3 vs. 21.6 months; P < 0.001), while the survival of TP53mut VAF < 10% was comparable to TP53wt. Within TP53mut VAF ≥ 10% cohort, the inferior outcomes persisted irrespective of the single- or multi-hit status, co-mutation pattern, or treatments received. Finally, survival of TP53mut patients was poor across all the blast categories and MDS patients with >10% blasts had inferior survival compared to <5%. In summary, TP53mut VAF ≥10% signified a clinically and molecularly homogenous cohort regardless of the allelic status.

Outcomes in Patients with Poor-Risk Cytogenetics with or without TP53 Mutations Treated with Venetoclax and Azacitidine

PURPOSE

To evaluate efficacy and safety of venetoclax + azacitidine in treatment-naïve patients with acute myeloid leukemia harboring poor-risk cytogenetics and TP53mut or TP53wt.

PATIENTS AND METHODS

We analyzed data from a phase III study (NCT02993523) comparing venetoclax (400 mg orally days 1-28) + azacitidine (75 mg/m2 days 1-7) or placebo + azacitidine, and from a phase Ib study (NCT02203773) of venetoclax + azacitidine. Patients were ineligible for intensive therapy. TP53 status was analyzed centrally; cytogenetic studies were performed locally.

RESULTS

Patients (n = 127) with poor-risk cytogenetics receiving venetoclax + azacitidine (TP53wt = 50; TP53mut = 54) were compared with patients with poor-risk cytogenetics (n = 56) receiving azacitidine alone (TP53wt = 22; TP53mut = 18).For poor-risk cytogenetics + TP53wt patients, venetoclax + azacitidine versus azacitidine alone resulted in composite remission rates (CRc) of 70% versus 23%, median duration of remission (DoR) of 18.4 versus 8.5 months, and median overall survival (OS) of 23.4 versus 11.3 months, respectively. Outcomes with venetoclax + azacitidine were comparable with similarly treated patients with intermediate-risk cytogenetics and TP53wt.For poor-risk cytogenetics + TP53mut patients, venetoclax + azacitidine versus azacitidine alone resulted in CRc of 41% versus 17%, median DoR of 6.5 versus 6.7 months, and median OS of 5.2 versus 4.9 months, respectively.For poor-risk cytogenetics + TP53mut patients, predominant grade ≥3 adverse events (AE) for venetoclax + azacitidine versus azacitidine were febrile neutropenia (55%/39%), thrombocytopenia (28%/28%), neutropenia (26%/17%), anemia (13%/6%), and pneumonia (28%/33%). AEs were comparable between TP53mut and TP53wt patients.

CONCLUSIONS

In poor-risk cytogenetics + TP53mut patients, venetoclax + azacitidine improved remission rates but not DoR or OS compared with azacitidine alone. However, in poor-risk cytogenetics + TP53wt patients, venetoclax + azacitidine resulted in higher remission rates and longer DoR and OS than azacitidine alone, with outcomes comparable with similarly treated patients with intermediate-risk cytogenetics. Toxicities were similar in TP53mut and TP53wt patients. See related commentary by Green and Zeidner, p. 5235.

Deep Molecular and In Silico Protein Analysis of p53 Alteration in Myelodysplastic Neoplasia and Acute Myeloid Leukemia

BACKGROUND

Mutation of the TP53 gene is one of the major drivers of myelodysplastic neoplasias (MDS) and acute myeloid leukemia with myelodysplasia-related changes (AML-MR). TP53 mutations present in these hematopoietic malignancies form a distinct molecular genetic cluster with a worse prognosis than without the alteration. However, besides well-characterized hot-spot variants, a significant proportion of TP53 alterations are of uncertain clinical significance.

METHODS

To enlighten so far unknown aspects, bone-marrow samples from altogether 77 patients are analyzed retrospectively with the diagnosis of AML-MR (26 cases), MDS-IB (12 cases), and MDS-LB (39 cases) according to WHO 2022 guidelines. Next-generation sequencing results are correlated with histological, cytogenetic, and survival data.

RESULTS

Twenty out of the 30 TP53 mutation types detected by NGS are not categorized in current public databases; thus, their clinical significance remained mysterious. Because of the interpretation difficulties and the absence of clinical correlations, pathogenicity is established based on in silico approaches. The 12 pathogenicity classification systems, as well as protein stability, protein-DNA, protein-protein interaction, and post-translational modification analyses are applied. We found statistically significant differences between AML/MDS groups considering p53 pathogenicity, protein structural changes, and overall survival. The largest number of abnormalities with the most severe consequences are found in AML-MR cases.

CONCLUSIONS

These molecular and in silico protein data further support that MDS with increased-blast (MDS-IB) is an intermediate group between AML-MR and MDS with low-blast (MDS-LB) patients, which frequently progresses to AML and is therefore considered a pre-leukemic condition.

Clonal Hematopoiesis: Role in Hematologic and Non-Hematologic Malignancies

Hematopoietic stem cells (HSCs) ensure the coordinated and balanced production of all hematopoietic cell types throughout life. Aging is associated with a gradual decline of the self-renewal and regenerative potential of HSCs and with the development of clonal hematopoiesis. Clonal hematopoiesis of indeterminate potential (CHIP) defines the clonal expansion of genetically variant hematopoietic cells bearing one or more gene mutations and/or structural variants (such as copy number alterations). CHIP increases exponentially with age and is associated with cancers, including hematologic neoplasia, cardiovascular and other diseases. The presence of CHIP consistently increases the risk of hematologic malignancy, particularly in individuals who have CHIP in association with peripheral blood cytopenia.

TP53 Combined Phenotype Score Is Associated with the Clinical Outcome of TP53-Mutated Myelodysplastic Syndromes

Simple Summary

TP53 is the most frequently mutated genes in cancer, and mutations of TP53 are observed in 5–10% of patients in myelodysplastic syndrome (MDS). In patients with MDS, TP53 mutations are associated with adverse outcomes; however, there is still significant heterogeneity in these disease courses. We performed retrospective review of 107 patients with untreated TP53-mutated MDS, and identified that the functional impact of TP53 mutations, represented by phenotypic annotation of TP53 mutations (PHANTM) combined phenotype score is associated with prognosis. In patients with TP53-mutated MDS, we found that a higher PHANTM combined phenotype score is associated with poorer clinical outcome, and this has independent influence on prognosis accounting for IPSS-R and other risk variables. Our findings suggest that TP53-mutated MDS is heterogeneous and not all TP53 mutations harbor the same impact on prognosis. The PHANTM combined score adds to prognostic precision in MDS beyond previously reported TP53 allelic state.

Abstract

Mutations of TP53 are observed in 5–10% of patients in myelodysplastic syndrome (MDS) and are associated with adverse outcomes. Previous studies indicate that the TP53 allelic state and variant allele frequency of TP53 mutation impact patient outcomes, but there is significant heterogeneity within this MDS subgroup. We performed retrospective review of clinicopathologic and genomic information of 107 patients with TP53-mutated MDS. We assessed each mutation according to the phenotypic annotation of TP53 mutations (PHANTM) and analyzed the associations between predicted TP53 mutant function, represented by the PHANTM combined phenotype score, and overall survival (OS) using the log rank test and Cox regression. Our results indicated that patients with PHANTM combined phenotype score above the median (>1) had significantly shorter OS compared to those with scores below the median (median OS: 10.59 and 16.51 months, respectively, p = 0.025). This relationship remained significant in multivariable analysis (HR (95%CI): 1.62 (1.01–2.58), p = 0.044) and identified to have an independent prognostic influence, accounting for known risk such as IPSS-R and other standard risk variables. Our results suggest that the functional information of TP53 mutations, represented by PHANTM combined phenotype score, are associated with the clinical outcome of patients with TP53-mutated MDS.

Prognostic and therapeutic impacts of mutant TP53 variant allelic frequency in newly diagnosed acute myeloid leukemia

TP53 mutations are associated with poor outcomes in acute myeloid leukemia (AML). The prognostic impact of mutant TP53 (TP53mut) variant allelic frequency (VAF) is not well established, nor is how this information might guide optimal frontline therapy. We retrospectively analyzed 202 patients with newly diagnosed TP53-mutated AML who underwent first-line therapy with either a cytarabine- or hypomethylating agent (HMA)-based regimen. By multivariate analysis, TP53mut VAF >40% was independently associated with a significantly higher cumulative incidence of relapse (P = .003) and worse relapse-free survival (P = .001) and overall survival (OS; P = .003). The impact of TP53mut VAF on clinical outcomes was driven by patients treated with a cytarabine-based regimen (median OS, 4.7 vs 7.3 months for VAF >40% vs ≤40%; P = .006), whereas VAF did not significantly affect OS in patients treated with HMA. The addition of venetoclax to HMA did not significantly affect OS compared with HMA without venetoclax, both in the entire TP53-mutated population and in patients stratified by TP53mut VAF. Among patients with TP53mut VAF ≤40%, OS was superior in those treated with higher-dose cytarabine, whereas OS was similarly poor for patients with TP53mut VAF >40% regardless of therapy. The best long-term outcomes were observed in those with 1 TP53 mutation with VAF ≤40% who received a frontline cytarabine-based regimen (2-year OS, 38% vs 6% for all others; P < .001). In summary, TP53mut VAF provides important prognostic information that may be considered when selecting frontline therapy for patients with newly diagnosed TP53-mutated AML.

Genomic context and TP53 allele frequency define clinical outcomes in TP53-mutated myelodysplastic syndromes

TP53 mutations are associated with adverse outcomes and shorter response to hypomethylating agents (HMAs) in myelodysplastic syndrome (MDS). Limited data have evaluated the impact of the type, number, and patterns of TP53 mutations in response outcomes and prognosis of MDS. We evaluated the clinicopathologic characteristics, outcomes, and response to therapy of 261 patients with MDS and TP53 mutations. Median age was 68 years (range, 18-80 years). A total of 217 patients (83%) had a complex karyotype. TP53 mutations were detected at a median variant allele frequency (VAF) of 0.39 (range, 0.01-0.94). TP53 deletion was associated with lower overall response rate (ORR) (odds ratio, 0.3; P = .021), and lower TP53 VAF correlated with higher ORR to HMAs. Increase in TP53 VAF at the time of transformation was observed in 13 patients (61%), and previously undetectable mutations were observed in 15 patients (65%). TP53 VAF was associated with worse prognosis (hazard ratio, 1.02 per 1% VAF increase; 95% confidence interval, 1.01-1.03; P < .001). Integration of TP53 VAF and karyotypic complexity identified prognostic subgroups within TP53-mutant MDS. We developed a multivariable model for overall survival that included the revised International Prognostic Scoring System (IPSS-R) categories and TP53 VAF. Total score for each patient was calculated as follows: VAF TP53 + 13 × IPSS-R blast score + 16 × IPSS-R cytogenetic score + 28 × IPSS-R hemoglobin score + 46 × IPSS-R platelet score. Use of this model identified 4 prognostic subgroups with median survival times of not reached, 42.2, 21.9, and 9.2 months. These data suggest that outcomes of patients with TP53-mutated MDS are heterogeneous and that transformation may be driven not only by TP53 but also by other factors.

Implications of TP53 allelic state for genome stability, clinical presentation and outcomes in myelodysplastic syndromes

Tumor protein p53 (TP53) is the most frequently mutated gene in cancer1,2. In patients with myelodysplastic syndromes (MDS), TP53 mutations are associated with high-risk disease3,4, rapid transformation to acute myeloid leukemia (AML)5, resistance to conventional therapies6-8 and dismal outcomes9. Consistent with the tumor-suppressive role of TP53, patients harbor both mono- and biallelic mutations10. However, the biological and clinical implications of TP53 allelic state have not been fully investigated in MDS or any other cancer type. We analyzed 3,324 patients with MDS for TP53 mutations and allelic imbalances and delineated two subsets of patients with distinct phenotypes and outcomes. One-third of TP53-mutated patients had monoallelic mutations whereas two-thirds had multiple hits (multi-hit) consistent with biallelic targeting. Established associations with complex karyotype, few co-occurring mutations, high-risk presentation and poor outcomes were specific to multi-hit patients only. TP53 multi-hit state predicted risk of death and leukemic transformation independently of the Revised International Prognostic Scoring System (IPSS-R)11. Surprisingly, monoallelic patients did not differ from TP53 wild-type patients in outcomes and response to therapy. This study shows that consideration of TP53 allelic state is critical for diagnostic and prognostic precision in MDS as well as in future correlative studies of treatment response.

The expression of MDM2, MDM4, p53 and p21 in myeloid neoplasms and the effect of MDM2/MDM4 dual inhibitor

p53 together with its downstream product p21 plays an important role in tumorigenesis development. MDM2 and MDM4 are two p53 regulators. We studied the expression of p53, p21, MDM2, and MDM4 in a total of 120 cases of myeloid neoplasms including MDS, AML or MDS/MPN, and control, using single and double immunohistochemical stains. We found TP53 mutations had a worse outcome in patients with AML/MDS, and p53 expression detected by immunohistochemistry had a similar prognostic value. p21 expression was strongly related to TP53 mutation status, with loss of expression in almost all TP53 mutated cases. MDM2 and MDM4 were highly expressed in hematopoietic cells in both benign and neoplastic cells. MDM2/p53 double positive cells exceeded MDM4/p53 double positive cells in neoplastic cases. Finally, we observed that p21 protein expression was up regulated upon the use of ALRN-6924 (Aileron) while no significant changes were seen in p53, MDM2 and MDM4 expression.

The prognostic impact of variant allele frequency (VAF) in TP53 mutant patients with MDS: A systematic review and meta-analysis

Tumor protein p53 (TP53) is frequently expressed in patients with myelodysplastic syndromes (MDS). Studies have already reported the poor prognostic impact of TP53 gene mutations in MDS patients. However, parts of this subgroup of patients with low-risk MDS still have relatively better survival and longer remission times. Therefore, we performed a meta-analysis to evaluate the prognostic difference intra-gene of variant allele frequency (VAF). The primary endpoint was overall survival (OS), and event-free survival (EFS) was selected as the secondary endpoint. We extracted the hazard ratio (HR) and 95% confidence interval (CI) for OS and EFS from univariate and multivariate Cox proportional hazard models. A total of 4003 MDS patients and 1278 TP53-mutated patients from 13 cohorts of 11 studies up to February 24, 2020, were included in our meta-analysis. Pooled HRs suggested that a high mutant VAF had an adverse impact on OS (HR = 2.11, 95% CI: 1.48-3.01, P < .0001) but no impact on EFS (HR = 15.57, 95% CI: 0.75-324.44, P = .003) in MDS patients. Twenty percent is a proper threshold to set (HR = 2.02, 95% CI: 1.31-3.13, P = .001) and is a rough line between high clone burden and low clone burden, while 40% is an exact cutoff point (HR = 2.11, 95% CI: 1.26-3.55, P < .0001) to guide diagnosis and treatment. Beyond the traditional binary classification of gene mutation, we aimed to find a way to divide mutant molecular markers more specifically by VAF to provide clinical therapeutic values. Our meta-analysis indicates that a high VAF is an independent, adverse prognostic factor for OS in TP53 mutant MDS patients. Patients with mediate/low-frequency parts who could be treated like wide-type patients have relatively better survival and may choose allogeneic hematopoietic stem cell transplantation as conditions permitting. Further prospective studies are needed in the future, and a large subgroup analysis of the same cutoff point subgroups is needed to obtain a more reliable basis for the impact of other mutant gene VAFs on the prognosis of MDS.

Regulation of Adult Neurogenesis in Mammalian Brain

Adult neurogenesis is a multistage process by which neurons are generated and integrated into existing neuronal circuits. In the adult brain, neurogenesis is mainly localized in two specialized niches, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ) adjacent to the lateral ventricles. Neurogenesis plays a fundamental role in postnatal brain, where it is required for neuronal plasticity. Moreover, perturbation of adult neurogenesis contributes to several human diseases, including cognitive impairment and neurodegenerative diseases. The interplay between extrinsic and intrinsic factors is fundamental in regulating neurogenesis. Over the past decades, several studies on intrinsic pathways, including transcription factors, have highlighted their fundamental role in regulating every stage of neurogenesis. However, it is likely that transcriptional regulation is part of a more sophisticated regulatory network, which includes epigenetic modifications, non-coding RNAs and metabolic pathways. Here, we review recent findings that advance our knowledge in epigenetic, transcriptional and metabolic regulation of adult neurogenesis in the SGZ of the hippocampus, with a special attention to the p53-family of transcription factors.

Phase II Study of the ALK5 Inhibitor Galunisertib in Very Low-, Low-, and Intermediate-Risk Myelodysplastic Syndromes

PURPOSE

Overactivation of TGF-β signaling is observed in myelodysplastic syndromes (MDS) and is associated with dysplastic hematopoietic differentiation. Galunisertib, a first-in-class oral inhibitor of the TGF-β receptor type 1 kinase (ALK5) has shown effectiveness in preclinical models of MDS and acceptable toxicity in phase I studies of solid malignancies.

PATIENTS AND METHODS

A phase II multicenter study of galunisertib was conducted in patients with very low-, low-, or intermediate-risk MDS by the Revised International Prognostic Scoring System criteria with hemoglobin ≤ 10.0 g/dL. Patients received oral galunisertib 150 mg twice daily for 14 days on/14 days off.

RESULTS

Ten of 41 evaluable patients (24.4%; 95% confidence interval, 12.4-40.3) achieved hematologic improvement erythroid response by International Working Group (IWG) 2006 criteria. A total of 18 of 41 patients (43.9%) achieved erythroid response as per IWG 2000 criteria. Nine of 28 (32.1%) of transfusion-dependent patients had hematologic improvement. A total of 18 of 41 (44%) patients had a significant reduction in fatigue. Overall median duration of response was 90 days in all patients. Rigorous stem and progenitor flow cytometry showed that patients with an early stem cell differentiation block were more likely to respond to galunisertib. The most common treatment-emergent adverse events were grade 1 or 2 in 20 (49%) of 41 patients, including any-grade fatigue (8/41, 20%), diarrhea (7/41, 17%), pyrexia (5/41, 12%), and vomiting (5/41, 12%).

CONCLUSIONS

In summary, galunisertib treatment has an acceptable safety profile and was associated with hematologic improvements in lower- and intermediate-risk MDS, with responses in heavily transfusion-dependent patients and in those with signs of an early stem cell differentiation block.

TP53 mutation status divides myelodysplastic syndromes with complex karyotypes into distinct prognostic subgroups

Risk stratification is critical in the care of patients with myelodysplastic syndromes (MDS). Approximately 10% have a complex karyotype (CK), defined as more than two cytogenetic abnormalities, which is a highly adverse prognostic marker. However, CK-MDS can carry a wide range of chromosomal abnormalities and somatic mutations. To refine risk stratification of CK-MDS patients, we examined data from 359 CK-MDS patients shared by the International Working Group for MDS. Mutations were underrepresented with the exception of TP53 mutations, identified in 55% of patients. TP53 mutated patients had even fewer co-mutated genes but were enriched for the del(5q) chromosomal abnormality (p < 0.005), monosomal karyotype (p < 0.001), and high complexity, defined as more than 4 cytogenetic abnormalities (p < 0.001). Monosomal karyotype, high complexity, and TP53 mutation were individually associated with shorter overall survival, but monosomal status was not significant in a multivariable model. Multivariable survival modeling identified severe anemia (hemoglobin < 8.0 g/dL), NRAS mutation, SF3B1 mutation, TP53 mutation, elevated blast percentage (>10%), abnormal 3q, abnormal 9, and monosomy 7 as having the greatest survival risk. The poor risk associated with CK-MDS is driven by its association with prognostically adverse TP53 mutations and can be refined by considering clinical and karyotype features.

Clinical implications of subclonal TP53 mutations in acute myeloid leukemia

The role of subclonal TP53 mutations, defined by a variant allele frequency of <20%, has not been addressed in acute myeloid leukemia yet. We, therefore, analyzed their prognostic value in a cohort of 1,537 patients with newly diagnosed disease, prospectively treated within three trials of the "German-Austrian Acute Myeloid Leukemia Study Group". Mutational analysis was performed by targeted deep sequencing and patients with TP53 mutations were categorized by their variant allele frequency into groups with frequencies >40%, 20%-40% and <20%. A total of 108 TP53 mutations were found in 98 patients (6.4%). Among these, 61 patients had variant allele frequencies >40%, 19 had variant allele frequencies between 20%-40% and 18 had frequencies <20%. Compared to specimens with clonal TP53 mutations, those with subclonal ones showed significantly fewer complex karyotypes and chromosomal losses. In either TP53-mutated group, patients experienced significantly fewer complete responses (P<0.001) and had worse overall and event-free survival rates (P<0.0001). In Cox regression analyses adjusting for age, white blood cell count, cytogenetic risk and type of acute myeloid leukemia, the adverse prognostic effect of TP53 mutations remained significant for all TP53-mutated subgroups. These data suggest that subclonal TP53 mutations are a novel prognostic parameter in acute myeloid leukemia and emphasize the usefulness of next-generation sequencing technologies for risk stratification in this disorder. The study was registered at ClinicalTrials.gov with number NCT00146120.

TP53 and therapy-related myeloid neoplasms

Therapy-related myeloid neoplasms (t-MNs) are the most serious late complications in patients treated with traditional cytotoxic chemotherapy and/or radiation. T-MNs are aggressive and chemorefractory hematologic malignancies, with a median survival of less than 6 months. TP53 mutations are highly enriched in t-MN patients, though the mechanism for this selective enrichment has only come to light over the past several years. In this review, we discuss the history and function of p53, and the role of TP53 mutations in the origin and progression of t-MNs. Emerging data has begun to elucidate who may be at highest risk of developing t-MNs, which ideally will enable us to develop preventative strategies for this devastating disease. As t-MNs may not be avoidable, novel therapies are urgently needed for this patient group and are underway as exemplified by recent investigation in restoring wild-type p53 function as well as directly targeting TP53 mutant variants. With better prevention and treatment, outcomes will hopefully begin to improve in the near future.

Analysis of clinical and molecular features of MDS patients with complex karyotype in China

We retrospectively analyzed 101 primary MDS patients with complex karyotype during January 2010 and April 2017.The median overall survival (OS) time was 13 (95% CI 9.98-16.02) months, and there was no significant difference in OS for different treatment. Chromosome 5/7 involvement was common (78.22%, 79/101) and associated with shorter OS (12 months vs. 28 months, P < 0.01) Monosomal karyotype (MK) is overlapped with CK in 79 patients, but was not statistically associated with shorter OS. While in 59 cases with genes sequenced, 57 (96.61%) patients were found to have at least one mutation of known significance, and TP53 was the most frequent (74.58%, 44/59), the median OS of patients with TP53 mutation was shorter than those without (10 vs. 27 months, P < 0.01). Multivariate analysis demonstrated that only TP53 mutation was the strongest independent prognostic factor for OS. Moreover, high variant allele frequency (VAF) of TP53 mutation (median VAF was 70.00%) was seen and associated with adverse survival (9 months vs. 13 months, p = 0.04). In conclusion, MDS patients with CK implied an unfavorable outcome regardless of any treatment, TP53 mutation occurs at a high frequency and has a higher VAF, both were associated with worse survival.

Characterization of TP53 mutations in low-grade myelodysplastic syndromes and myelodysplastic syndromes with a non-complex karyotype

OBJECTIVES

Although commonly associated with high-grade myelodysplastic syndrome (MDS) and MDS with a complex karyotype, TP53 mutations also occur in low-grade MDS and MDS with a non-complex karyotype. In latter cases, their clinicopathological features and the characteristics of TP53 mutations remain poorly characterized.

METHODS

176 MDS cases with TP53 mutations were stratified and characterized based on their karyotype and histologic subtype.

RESULTS

Among 176 cases, 17% had a non-complex karyotype and 24% were low-grade MDS. TP53 mutations often occurred in DNA-binding domains and the majority of cases had only one mutation, irrespective of their karyotype and MDS subtype. The variant allele frequency (VAF), however, was associated with karyotype complexity and the types of MDS with a lower VAF found in cases with a non-complex karyotype and low-grade MDS. A low (<20%) VAF was associated with a better survival, as well as low-grade subtype.

CONCLUSIONS

In low-grade MDS and MDS with a non-complex karyotype, TP53 mutations showed a lower VAF. Patients with a lower VAF had a better survival. TP53 mutations are not the only prognostic factor in MDS patients with TP53 mutations as the VAF, blast counts and history of prior therapy also play important roles in prognosis.

Dysfunctional diversity of p53 proteins in adult acute myeloid leukemia: projections on diagnostic workup and therapy

The heterogeneous nature of acute myeloid leukemia (AML) and its poor prognosis necessitate therapeutic improvement. Current advances in AML research yield important insights regarding AML genetic, epigenetic, evolutional, and clinical diversity, all in which dysfunctional p53 plays a key role. As p53 is central to hematopoietic stem cell functions, its aberrations affect AML evolution, biology, and therapy response and usually predict poor prognosis. While in human solid tumors TP53 is mutated in more than half of cases, TP53 mutations occur in less than one tenth of de novo AML cases. Nevertheless, wild-type (wt) p53 dysfunction due to nonmutational p53 abnormalities appears to be rather frequent in various AML entities, bearing, presumably, a greater impact than is currently appreciated. Hereby, we advocate assessment of adult AML with respect to coexisting p53 alterations. Accordingly, we focus not only on the effects of mutant p53 oncogenic gain of function but also on the mechanisms underlying nonmutational wtp53 inactivation, which might be of therapeutic relevance. Patient-specific TP53 genotyping with functional evaluation of p53 protein may contribute significantly to the precise assessment of p53 status in AML, thus leading to the tailoring of a rationalized and precision p53-based therapy. The resolution of the mechanisms underlying p53 dysfunction will better address the p53-targeted therapies that are currently considered for AML. Additionally, a suggested novel algorithm for p53-based diagnostic workup in AML is presented, aiming at facilitating the p53-based therapeutic choices.

Ribosomal protein L23 negatively regulates cellular apoptosis via the RPL23/Miz-1/c-Myc circuit in higher-risk myelodysplastic syndrome

Ribosomal protein (RP) L23 is a negative regulator of cellular apoptosis, and RPL23 overexpression is associated with abnormal apoptotic resistance in CD34+ cells derived from patients with higher-risk myelodysplastic syndrome (MDS). However, the mechanism underlying RPL23-induced apoptotic resistance in higher-risk MDS patients is poorly understood. In this study, we showed that reduced RPL23 expression led to suppressed cellular viability, increased apoptosis and G1-S cell cycle arrest. Gene microarray analysis comparing RPL23-knockdown and control cells identified an array of differentially expressed genes, of which, Miz-1, was upregulated with transactivation of the cell cycle inhibitors p15^Ink4b and p21^Cip1, and Miz-1’s functional repressor, c-Myc, was downregulated. Cells derived from higher-risk MDS patients demonstrated consistently increased expression of RPL23 and c-Myc and decreased Miz-1 expression compared with cells from lower-risk patients. In conclusion, Miz-1-dependent induction of p15^Ink4b and p21^Cip1 was depressed with decreased Miz-1 and increased c-Myc expression under conditions of elevated RPL23 expression, leading to apoptotic resistance in higher-risk MDS patients. Because RPL23 is encoded by a target gene of c-Myc, the RPL23/Miz-1/c-Myc regulatory circuit provides a feedback loop that links efficient RPL23 expression with c-Myc’s function to suppress Miz-1-induced Cdk inhibitors and thereby leads to apoptotic resistance in higher-risk MDS patients.