p53 protein expression independently predicts outcome in patients with lower-risk myelodysplastic syndromes with del(5q)

Immunohistochemistry screening for TP53 mutation in myeloid neoplasms in AZF-fixed bone marrow biopsies

TP53 mutational status in myeloid neoplasms is prognostic and in acute myeloid leukaemia (AML) may lead to alternative induction therapy; therefore, rapid assessment is necessary for precision treatment. Assessment of multiple prognostic genes by next generation sequencing in AML is standard of care, but the turn-around time often cannot support rapid clinical decision making. Studies in haematological neoplasms suggest p53 immunohistochemistry (IHC) correlates with TP53 mutational status, but they have used variable criteria to define TP53 overexpression. p53 IHC was performed and interpreted on AZF-fixed, acid decalcified bone marrow biopsies on 47 cases of clonal myeloid neoplasms with TP53 mutations between 2016 and 2019 and 16 control samples. Results were scored by manual and digital analysis. Most TP53-mutated cases (81%) overexpressed p53 by digital analysis and manual analysis gave similar results. Among the nine TP53-mutated IHC-negative cases, seven (78%) were truncating mutations and two (22%) were single-hit missense mutations. Using a digital cut-off of at least 3% ≥1+ positive nuclei, the sensitivity and specificity are 81% and 100%; cases with loss-of-function mutations were more likely to be negative. In this cohort, p53 immunopositivity correlated with TP53 mutational status, especially missense mutations, with excellent specificity. Truncating TP53 mutations explain most IHC-negative cases, impacting the sensitivity. We demonstrate that p53 IHC can screen for TP53 mutations allowing quicker treatment decisions for most patients. However, not all patients will be identified, so molecular studies are required. Furthermore, cut-offs for positivity vary in the literature, consequently laboratories should independently validate their processes before adopting p53 IHC for clinical use. p53 IHC performs well to screen for TP53 mutations in AZF-fixed bone marrow. Performance in our setting differs from the literature, which shows variability of pre-analytic factors and cut-offs used to screen for TP53 mutations. Each laboratory should validate p53 IHC to screen for TP53 mutations in their unique setting.

Emergence of TP53 mutation during lenalidomide therapy of myelodysplastic syndrome with del(5q) and its subsequent disappearance following salvage therapy with decitabine

Not available.

Pharmacological reactivation of p53 in the era of precision anticancer medicine

p53, which is encoded by the most frequently mutated gene in cancer, TP53, is an attractive target for novel cancer therapies. Despite major challenges associated with this approach, several compounds that either augment the activity of wild-type p53 or restore all, or some, of the wild-type functions to p53 mutants are currently being explored. In wild-type TP53 cancer cells, p53 function is often abrogated by overexpression of the negative regulator MDM2, and agents that disrupt p53-MDM2 binding can trigger a robust p53 response, albeit potentially with induction of p53 activity in non-malignant cells. In TP53-mutant cancer cells, compounds that promote the refolding of missense mutant p53 or the translational readthrough of nonsense mutant TP53 might elicit potent cell death. Some of these compounds have been, or are being, tested in clinical trials involving patients with various types of cancer. Nonetheless, no p53-targeting drug has so far been approved for clinical use. Advances in our understanding of p53 biology provide some clues as to the underlying reasons for the variable clinical activity of p53-restoring therapies seen thus far. In this Review, we discuss the intricate interactions between p53 and its cellular and microenvironmental contexts and factors that can influence p53's activity. We also propose several strategies for improving the clinical efficacy of these agents through the complex perspective of p53 functionality.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissue: Myeloid Neoplasms

In this manuscript, we review myeloid neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5), focusing on changes from the revised fourth edition (WHO-HEM4R). Disease types and subtypes have expanded compared with WHO-HEM4R, mainly because of the expansion in genomic knowledge of these diseases. The revised classification is based on a multidisciplinary approach including input from a large body of pathologists, clinicians, and geneticists. The revised classification follows a hierarchical structure allowing usage of family (class)-level definitions where the defining diagnostic criteria are partially met or a complete investigational workup has not been possible. Overall, the WHO-HEM5 revisions to the classification of myeloid neoplasms include major updates and revisions with increased emphasis on genetic and molecular drivers of disease. The most notable changes have been applied to the sections of acute myeloid leukemia and myelodysplastic neoplasms (previously referred to as myelodysplastic syndrome) with incorporation of novel, disease-defining genetic changes. In this review we focus on highlighting the updates in the classification of myeloid neoplasms, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of myeloid neoplasms in routine practice.

Inactivation of p53 provides a competitive advantage to del(5q) myelodysplastic syndrome hematopoietic stem cells during inflammation

Inflammation is associated with the pathogenesis of myelodysplastic syndromes (MDS) and emerging evidence suggests that MDS hematopoietic stem and progenitor cells (HSPC) exhibit an altered response to inflammation. Deletion of chromosome 5 (del(5q)) is the most common chromosomal abnormality in MDS. Although this MDS subtype contains several haploinsufficient genes that impact innate immune signaling, the effects of inflammation on del(5q) MDS HSPC remains undefined. Utilizing a model of del(5q)-like MDS, inhibiting the IRAK1/4-TRAF6 axis improved cytopenias, suggesting that activation of innate immune pathways contributes to certain clinical features underlying the pathogenesis of low-risk MDS. However, low-grade inflammation in the del(5q)-like MDS model did not contribute to more severe disease but instead impaired the del(5q)-like HSPC as indicated by their diminished numbers, premature attrition and increased p53 expression. Del(5q)-like HSPC exposed to inflammation became less quiescent, but without affecting cell viability. Unexpectedly, the reduced cellular quiescence of del(5q) HSPC exposed to inflammation was restored by p53 deletion. These findings uncovered that inflammation confers a competitive advantage of functionally defective del(5q) HSPC upon loss of p53. Since TP53 mutations are enriched in del(5q) AML following an MDS diagnosis, increased p53 activation in del(5q) MDS HSPC due to inflammation may create a selective pressure for genetic inactivation of p53 or expansion of a pre-existing TP53-mutant clone.

P53 IHC Result as a Prognostic Tool in MDS

Background & Objective

Some of the patients with myelodysplastic syndrome (MDS) are categorized as good prognosis based on the Revised International Prognostic Scoring System (IPSS-R). However, these patients may have poor clinical outcomes. It seems that the current diagnostic tools and IPSS-R cannot consider genetic factors for determining the prognosis of MDS patients.

Methods

This cross-sectional study included all adult MDS patients of both genders who were admitted from March 2015 to March 2020 to the Hematology wards of two educational tertiary hospitals in Iran (Namazi and Faghihi, affiliated with Shiraz University of medical sciences). Study data included relevant retrospective data from medical records and the results of immunohistochemical p53 staining on bone marrow biopsies.

Results

Of the 84 patients, 65 (77.4%) showed p53 expression in bone marrow. They had shorter median survival than those without p53 expression. Considering both variables of P53 IHC results and IPSS-R score, the patients who died with low-risk IPSS-R score presented high p53 expression.

Conclusion

This study shows that the investigation of p53 expression by IHC at the time of diagnosis is a valuable indicator of survival rate in MDS patients. These data suggest that the immunohistochemical analysis of p53 can be a prognostic tool for MDS and should be used as an adjunct test to make decisions on the best therapeutic choice.

Clonal hematopoiesis and bone marrow inflammation

Clonal hematopoiesis (CH) occurs in hematopoietic stem cells with increased risks of progressing to hematologic malignancies. CH mutations are predominantly found in aged populations and correlate with an increased incidence of cardiovascular and other diseases. Increased lines of evidence demonstrate that CH mutations are closely related to the inflammatory bone marrow microenvironment. In this review, we summarize the recent advances in this topic starting from the discovery of CH and its mutations. We focus on the most commonly mutated and well-studied genes in CH and their contributions to the innate immune responses and inflammatory signaling, especially in the hematopoietic cells of bone marrow. We also aimed to discuss the interrelationship between inflammatory bone marrow microenvironment and CH mutations. Finally, we provide our perspectives on the challenges in the field and possible future directions to help understand the pathophysiology of CH.

The expression level of ARF and p53 in AML patients, and their relation to patients' outcome

Background

Acute myeloid leukemia (AML) is a cancer of hematopoietic progenitors characterized by gene mutations. The most popular deregulations are mutation and altered expression in the p53 gene, which is considered the guardian of the genome. Its activity is controlled by regulatory genes, e.g., alternate open reading frame (ARF), whose defects could affect p53 activity.

Aim

To study the effect of altered expression of p53 and ARF genes in de novo AML patients and correlate the results to the patients’ characteristics and outcomes.

Methods

Expression levels of p53 and ARF were assessed in 96 AML adult patients compared to 20 healthy controls using quantitative reverse-transcription PCR (RT-qPCR).

Results

There was significant up-regulation of p53 [77.6 (3.8–9528.3)] compared to controls [1.031 (0.210–9.051)], p < 0.001]. The expression level of ARF was significantly upregulated [6.2 (0.5–964.0)] compared to controls [0.854 (0.357–2.519), p < 0.001]. All of the low ARF expressers had low p53 overexpression, 61.1% of patients with high ARF expression had high p53 over-expression, and 38.9% with high ARF expression had low p53 over-expression (p < 0.001). ARF expression shows a trend of association with FLT3 mutation, as 89.3% with FLT3 mutation have high ARF expression (p = 0.080). Low p53 over-expression was seen in 77% of APL patients, while high p53 expression was associated with non-APL (p = 0.040). The median DFS of mutant NPM1 patients was higher than wild NPM1 (46.15 vs. 5.89 days, p = 0.045). Patients aged ≤ 50 years had better OS and DFS than those > 50 (p = 0.05, p = 0.035, respectively).There were no significant statistical associations between DFS and p53, ARF, and FLT3 mutations.

Conclusion

The p53 and ARF genes are overexpressed in de novo AML patients and they are interrelated. low p53 overexpression is associated with APL phenotype and t(15;17) and patients with t(15;17) had slightly better survival than patients with negative t(15;17) (p = 0.061). AML patients with mutated NPM1 had better DFS than wild NPM1 (p = 0.045). p53 pathway regulation can occur by many alternative ways rather than gene mutation.

Suspected Immune Thrombocytopenic Purpura Induced by Lenalidomide for the Treatment of Myelodysplastic Syndrome with Deletion of Chromosome 5q: A Case Report

Lenalidomide (LEN), one of the key drugs in the treatment of myelodysplastic syndromes (MDS) with 5q deletion, as well as multiple myeloma (MM), has various immunomodulatory effects and has been associated with autoimmune diseases, including immune thrombocytopenic purpura (ITP). A 78-year-old man presented with pancytopenia and was diagnosed with MDS with 5q deletion and other chromosomal abnormalities. Two cycles of LEN therapy (one cycle: 10 mg/day for 21 days) resulted in a transient improvement in anemia, followed by MDS progression with severe thrombocytopenia (4 × 10⁹/L) refractory to platelet transfusions. As other non-immune and alloimmune causes of transfusion-refractory thrombocytopenia were excluded, and the level of platelet-associated immunoglobulin G was extremely high compared with the level before treatment with LEN, the diagnosis of ITP was highly suspected. Despite treatment with prednisolone (PSL), eltrombopag, and repeated platelet transfusions, his platelet count did not increase, and he died of a gastrointestinal hemorrhage. Several cases of ITP induced by LEN used to treat MM had been reported, but the platelet count recovered after administration of PSL in these previous cases. However, we should be mindful of using LEN for patients with MDS because its treatment may become extremely difficult if ITP develops.

Isotypic analysis of anti-p53 serum autoantibodies and p53 protein tissue phenotypes in colorectal cancer

The presence of IgA- and IgM-specific autoantibody (AAb) isotypes and their relationship to p53 tissue expression patterns are not well understood. This study aims to investigate the clinical utility of the anti-p53 AAb isotypes and tissue positivity in colorectal cancer (CRC). We analysed anti-p53 IgG, IgM, and IgA AAbs in sera of 99 CRC patients and 99 non-cancer control subjects. Corresponding tissue expression of the p53 protein was evaluated by immunohistochemistry (IHC). Anti-p53 AAbs of the IgG isotype were present in the sera of 21 out of 99 patients (21%), while IgM AAbs were observed in 9 (9%) and IgA in 2 (2%) CRC patients. Anti-p53 AAbs of all three isotypes were generally associated with IHC staining indicative of mutated TP53. Seropositive anti-p53 IgM cases in the absence of anti-p53 IgG were linked to wild-type p53. Anti-p53 IgA in the absence of IgG AAbs was detected in two non-cancer controls indicating a potential p53 epitope mimicry. Although seropositivity was not associated with patient survival (P = 0.650), mutant-pattern p53 tissue expression was associated with reduced 5-year overall survival (P = 0.032), however, it was not an independent prognostic marker (Multivariate Cox regression, P = 0.193). In conclusion, immunoglobulin isotyping revealed that anti-p53 IgM and IgA AAbs were predominantly concurrent with anti-p53 serum IgG and the mutant-pattern p53 tissue phenotype. IgM and IgA seropositive cases in absence of anti-p53 IgG were linked to wild-type p53 tissue phenotype indicating early anti-p53 immune responses preceding isotype class-switch (IgM) or p53 antigen mimicry (IgA).

Synonymous Variants: Necessary Nuance in our Understanding of Cancer Drivers and Treatment Outcomes

Once called "silent mutations" and assumed to have no effect on protein structure and function, synonymous variants are now recognized to be drivers for some cancers. There have been significant advances in our understanding of the numerous mechanisms by which synonymous single nucleotide variants (sSNVs) can affect protein structure and function by affecting pre-mRNA splicing, mRNA expression, stability, folding, miRNA binding, translation kinetics, and co-translational folding. This review highlights the need for considering sSNVs in cancer biology to gain a better understanding of the genetic determinants of human cancers and to improve their diagnosis and treatment. We surveyed the literature for reports of sSNVs in cancer and found numerous studies on the consequences of sSNVs on gene function with supporting in vitro evidence. We also found reports of sSNVs that have statistically significant associations with specific cancer types but for which in vitro studies are lacking to support the reported associations. Additionally, we found reports of germline and somatic sSNVs that were observed in numerous clinical studies and for which in silico analysis predicts possible effects on gene function. We provide a review of these investigations and discuss necessary future studies to elucidate the mechanisms by which sSNVs disrupt protein function and are play a role in tumorigeneses, cancer progression, and treatment efficacy. As splicing dysregulation is one of the most well recognized mechanisms by which sSNVs impact protein function, we also include our own in silico analysis for predicting which sSNVs may disrupt pre-mRNA splicing.

Evolution of severe (transfusion-dependent) anaemia in myelodysplastic syndromes with 5q deletion is characterized by a macrophage-associated failure of the eythropoietic niche

Evolution of erythrocyte transfusion-dependent (RBC-TD) anaemia associated with haploinsufficiency of the ribosomal protein subunit S14 gene (RPS14) is a characteristic complication of myelodysplastic syndromes (MDS) with del(5q) [MDS.del(5q)]. Evaluating 39 patients with MDS.del(5q), <5% of anaemia progression was attributable to RPS14-dependent alterations of normoblasts, pro-erythroblasts, or CD34⁺ CD71⁺ precursors. Ninety-three percent of anaemia progression and 70% of the absolute decline in peripheral blood Hb value were attributable to disappearance of erythroblastic islands (Ery-Is). Ery-Is loss occurred independently of blast excess, TP53 mutation, additional chromosome aberrations and RPS14-dependent alterations of normoblasts and pro-erythroblasts. It was associated with RPS14-dependent intrinsic (S100A8⁺ ) and extrinsic [tumour necrosis factor α (TNF-α)-overproduction] alterations of (CD169⁺ ) marrow macrophages (p < 0.00005). In a mouse model of RPS14 haploinsufficiency, Ery-Is disappeared to a similar degree: approximately 70% of Ery-Is loss was related to RPS14-dependent S100A8 overexpression of marrow macrophages, less than 20% to that of CD71^high Ter119^- immature precursors, and less than 5% to S100A8/p53 overexpression of normoblasts or pro-erythroblasts. Marked Ery-Is loss predicted reduced efficacy (erythrocyte transfusion independence) of lenalidomide therapy (p = 0.0006). Thus, erythroid hypoplasia, a characteristic complication of MDS.del(5q), seems to result primarily from a macrophage-associated failure of the erythropoietic niche markedly reducing the productive capacity of erythropoiesis as the leading factor in anaemia progression and evolution of RBC-TD in MDS.del(5q).

TP53 in Myelodysplastic Syndromes

Simple Summary

The importance of gene variants in the prognosis of myelodysplastic syndromes (MDSs) has been repeatedly reported in recent years. Especially, TP53 mutations are independently associated with a higher risk category, resistance to conventional therapies, rapid transformation to leukemia, and a poor outcome. In the review, we discuss the features of monoallelic and biallelic TP53 mutations within MDS, the carcinogenic mechanisms, and the predictive value of TP53 variants in current standard treatments including hypomethylating agents, allogeneic hematopoietic stem cell transplantation, and lenalidomide, as well as the latest progress in TP53-targeted therapy strategies in MDS.

Abstract

Myelodysplastic syndromes (MDSs) are heterogeneous for their morphology, clinical characteristics, survival of patients, and evolution to acute myeloid leukemia. Different prognostic scoring systems including the International Prognostic Scoring System (IPSS), the Revised IPSS, the WHO Typed Prognostic Scoring System, and the Lower-Risk Prognostic Scoring System have been introduced for categorizing the highly variable clinical outcomes. However, not considered by current MDS prognosis classification systems, gene variants have been identified for their contribution to the clinical heterogeneity of the disease and their impact on the prognosis. Notably, TP53 mutation is independently associated with a higher risk category, resistance to conventional therapies, rapid transformation to leukemia, and a poor outcome. Herein, we discuss the features of monoallelic and biallelic TP53 mutations within MDS, their corresponding carcinogenic mechanisms, their predictive value in current standard treatments including hypomethylating agents, allogeneic hematopoietic stem cell transplantation, and lenalidomide, together with the latest progress in TP53-targeted therapy strategies, especially MDS clinical trial data.

Combined utility of CD177, P53, CD105 and c-kit immunohistochemical stains improves the detection of myelodysplastic syndrome

The diagnosis of myelodysplastic syndrome (MDS) relies primarily on identifying peripheral blood cytopenia and morphologic dysplasia as well as detecting cytogenetic aberrations in a subset of patients. Accumulating data points to the importance of examining certain immunophenotypic changes characteristic of MDS, most of which are tested by flow cytometry. The role of immunohistochemistry in the diagnostic workup of MDS is less known. In this study, we used immunohistochemistry to survey the expression patterns of CD177, P53, CD105 and c- kit in a cohort of MDS bone marrow specimens (n = 57) and compared the results with a control group of patients who had cytopenia for other benign conditions (n = 49). MDS cases showed significant higher rates of: CD177-loss (13/57, 23% vs 1/49, 2%; P = .0016), P53 overexpression (8/57, 14% vs none; P = .005) and the presence of clusters of CD105-positive cells (6/57, 11% vs none; P = .021). Increased c-kit-positive cells was more common in MDS patients, but not statistically significant (17/57, 30% vs 8/49, 16%; P = .102). On multivariate analysis, only loss of CD177 expression was significantly higher in MDS group (P = .014). These findings suggest that a panel of immunohistochemical stains could serve as an adjunct tool in investigating unexplained cytopenias and warrant further comparative studies with flow cytometry.

Accuracy of bone marrow histochemical TP53 expression compared to the detection of TP53 somatic mutations in patients with myelodysplastic syndromes harbouring a del5q cytogenetic abnormality

TP53 gene mutations are common in Myelodysplastic Syndromes (MDS) with del5q and have a clinical and prognostic significance. Next Generation Sequencing (NGS) is an accurate, but expensive, technique, and not commonly available. Immunohistochemistry (IHC) for TP53 expression has been recently used as a surrogate to assess TP53 mutations. To compare the concordance between TP53 expression in IHC and TP53 mutations by NGS, 30 cases with MDS harbouring a del5q abnormality were evaluated. Overall, 10/30 patients (33.3%) had TP53 mutations by NGS, while 16/29 (55.1%) had TP53 overexpression in IHC. TP53 expression by IHC had a 70% sensitivity to identify patients with TP53 mutation by NGS, but its specificity was low (52.6%, kappa = 0.198; P = 0.24). In addition, ROC curve analyses showed that the overall diagnostic value (accuracy) of TP53 expression in IHC to identify patients with TP53 mutation by NGS was 68% in the whole study sample and 67% in patients with isolated del5q-. In both cases, the areas under the curves did not attain the statistical significance (P = 0.11 and P = 0.29, respectively). Based on the ROC curve, the cut-off of 2.3% TP53 expression in IHC was shown to be the best cut-off to identify TP53 mutations: using this cut-off, the agreement between TP53 expression and TP53 mutation by NGS reached statistical significance (kappa = 0.42; P = 0.023). In conclusion, the agreement between TP53 expression in IHC and TP53 mutation analysis by NGS is rather unsatisfactory in MDS patients with del5q at the standard cut-off. Thus, the IHC technique cannot be considered a valid alternative to NGS evaluation of TP53 mutational status in these patients.

Targeting the Myeloid Lineages and the Immune Microenvironment in Myelodysplastic Syndromes: Novel and Evolving Therapeutic Strategies

OBJECTIVE

To discuss the recent and emerging data for novel targeted therapies in myelodysplastic syndromes (MDS).

DATA SOURCES

A literature search from January 2015 to June 2021 was performed using the key terms targeted therapies, myelodysplastic syndromes, DNA repair, erythroid differentiation therapy, epigenetic inhibitors, signal transduction inhibitors, and apoptosis-inducing agents.

STUDY SELECTION AND DATA EXTRACTION

Relevant clinical trials and articles in the English language were identified and reviewed.

DATA SYNTHESIS

MDS are a heterogeneous group of malignant blood disorders affecting the bone marrow (BM), ultimately leading to BM failure, acute leukemia, and death. Selection of treatment is influenced by the severity of symptoms, cytopenia, cytogenetics, prognostic category, medical fitness, and patient preferences. Although current therapies such as erythropoiesis stimulating agents (ESAs) and hypomethylating agents (HMAs) help improve anemia and reduce transfusion burden, limited treatment options exist when patients experience treatment failure to ESAs or HMA. Recent regulatory approval of luspatercept, which targets the erythroid differentiation pathway, represents a major therapeutic advance in the management of anemia in MDS patients who are refractory to ESAs. Many investigational targeted therapies that aim at the myeloid lineage signaling pathway and the immune microenvironment are in active development.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This nonexhaustive review summarizes and describes the recent data for targeted therapies for MDS.

CONCLUSION

The development of novel and investigational therapeutic agents continues to contribute to an improved understanding of tumor biology. The precise therapeutic role and timing of these agents remain to be elucidated.

Age, Blasts, Performance Status and Lenalidomide Therapy Influence the Outcome of Myelodysplastic Syndrome With Isolated Del(5q): A Study of 58 South American Patients

BACKGROUND

Myelodysplastic Syndrome (MDS) with isolated deletion 5q is associated with a low risk to leukemic evolution and long overall survival (OS); it comprises 3%-4.5% of MDS cases in Latin America classified according to the World Health Organization 2008. This study aims to describe clinical, laboratory and the outcome of patients according to the newest World Health Organization 2016 proposal.

METHODS

We retrospectively reviewed patients from four Brazilian (BR) and four Argentinean (AR) centers diagnosed between 1999 and 2019.

RESULTS

The 58 patients (16-AR and 42-BR) presented a median age of 67 (IQR 61-75) years old, women predominance (70.7%) and transfusion dependency (62.5%) at diagnosis. Median hemoglobin level was 8.1g/dL, 27.5% and 44.4% presented thrombocytosis and neutropenia, respectively. Bone marrow (BM) was predominantly hypercellular (43.1%) with 66% showing dysplasia >1 lineage and 37.9% with >2% of blasts. Deletion 5q was mostly isolated (79.3%) and a variety of abnormalities were observed in remaining cases. Most patients were treated with erythropoietin-stimulating agents (ESA), 18 with lenalidomide and 15 with thalidomide. Median follow-up was 7.6 years, with a median OS of 3.5 years and an 8-years leukemic evolution rate of 18.4%. Multivariate analysis showed that age >75 years (HR 2.19), ECOG ≥2 (HR 5.76), BM blasts >2% (HR 2.92) and lenalidomide treatment (HR 0.25) independently influenced the OS.

CONCLUSION

Older age, worse performance status and higher percentage of blasts, that can be easily assessed, were associated to a worse prognosis. Also, our results corroborate the protective influence of lenalidomide in terms of OS in this South American series.

TIFAB Regulates USP15-Mediated p53 Signaling during Stressed and Malignant Hematopoiesis

TRAF-interacting protein with a forkhead-associated domain B (TIFAB) is implicated in myeloid malignancies with deletion of chromosome 5q. Employing a combination of proteomic and genetic approaches, we find that TIFAB regulates ubiquitin-specific peptidase 15 (USP15) ubiquitin hydrolase activity. Expression of TIFAB in hematopoietic stem/progenitor cells (HSPCs) permits USP15 signaling to substrates, including MDM2 and KEAP1, and mitigates p53 expression. Consequently, TIFAB-deficient HSPCs exhibit compromised USP15 signaling and are sensitized to hematopoietic stress by derepression of p53. In MLL-AF9 leukemia, deletion of TIFAB increases p53 signaling and correspondingly decreases leukemic cell function and development of leukemia. Restoring USP15 expression partially rescues the function of TIFAB-deficient MLL-AF9 cells. Conversely, elevated TIFAB represses p53, increases leukemic progenitor function, and correlates with MLL gene expression programs in leukemia patients. Our studies uncover a function of TIFAB as an effector of USP15 activity and rheostat of p53 signaling in stressed and malignant HSPCs.

Niederkorn et al. identify TIFAB as a critical node in hematopoietic cells under stressed and oncogenic cell states. Their studies indicate that deregulation of the TIFAB-USP15 complex, as observed in del(5q) myelodysplasia or MLL-rearranged leukemia, modulates p53 activity and has critical functional consequences for stressed and malignant hematopoietic cells.

p53 immunohistochemistry discriminates between pure erythroid leukemia and reactive erythroid hyperplasia

Pure erythroid leukemia (PEL) is a rare, aggressive subtype of acute myeloid leukemia with a poor prognosis. The diagnosis of PEL is often medically urgent, quite challenging, and is typically a diagnosis of exclusion requiring meticulous distinction from non-neoplastic erythroid proliferations, particularly florid erythroid hyperplasia/regeneration. Given the frequency of TP53 mutations in the molecular signature of PEL, we hypothesize that differential p53 expression by immunohistochemistry (IHC) may be useful in distinguishing PEL versus non-neoplastic erythroid conditions. We performed p53 IHC on 5 normal bone marrow, 46 reactive erythroid proliferations, and 27 PEL cases. We assessed the positivity and intensity of nuclear staining in pronormoblasts and basophilic normoblasts using a 0–3+ scale with 0 being absent (with internal positive controls) and 3 being strong nuclear positivity. A total of 26/27 PEL cases showed strong, uniform, diffuse intense staining by the neoplastic pronormoblasts versus 0/5 and 0/46 normal and reactive controls, respectively. The control cases show various staining patterns ranging from 0 to 3+ in scattered erythroid precursor cells. Uniform, strong p53 positivity is unique to PEL and discriminates this entity from a benign erythroid mimic. Thus, p53 IHC may be a useful marker in urgent medical cases to assist in the confirmation of a malignant PEL diagnosis while awaiting the results of additional ancillary studies such as cytogenetics.

TP53 mutations in myelodysplastic syndromes and secondary AML confer an immunosuppressive phenotype

Somatic gene mutations are key determinants of outcome in patients with myelodysplastic syndromes (MDS) and secondary AML (sAML). In particular, patients with TP53 mutations represent a distinct molecular cohort with uniformly poor prognosis. The precise pathogenetic mechanisms underlying these inferior outcomes have not been delineated. In this study, we characterized the immunological features of the malignant clone and alterations in the immune microenvironment in patients with TP53-mutant and wild-type MDS or sAML. Notably, PDL1 expression is significantly increased in hematopoietic stem cells of patients with TP53 mutations, which is associated with MYC upregulation and marked downregulation of MYC's negative regulator miR-34a, a p53 transcription target. Notably, patients with TP53 mutations display significantly reduced numbers of bone marrow-infiltrating OX40+ cytotoxic T cells and helper T cells, as well as decreased ICOS+ and 4-1BB+ natural killer cells. Further, highly immunosuppressive regulatory T cells (Tregs) (ie, ICOShigh/PD-1-) and myeloid-derived suppressor cells (PD-1low) are expanded in cases with TP53 mutations. Finally, a higher proportion of bone marrow-infiltrating ICOShigh/PD-1- Treg cells is a highly significant independent predictor of overall survival. We conclude that the microenvironment of TP53 mutant MDS and sAML has an immune-privileged, evasive phenotype that may be a primary driver of poor outcomes and submit that immunomodulatory therapeutic strategies may offer a benefit for this molecularly defined subpopulation.

Single Cell Detection of the p53 Protein by Mass Cytometry

Simple Summary

Investigation of protein expression in cancer cells is an important part of the diagnostic process. Increasing knowledge about expression of different proteins has been exploited for prognostic assessments and in some cases also for selection of treatment. The p53 protein has proven important in development of various cancers, and the expression of this protein and its signaling pathway is therefore of interest when examining cancer patient samples. Here, we present mass cytometry as a tool for detection of p53 expression. Mass cytometry allows for measurement of up to 50 parameters per sample with single cell resolution, and we aim to demonstrate its potential for p53-focused research.

Abstract

Purpose: The p53 protein and its post-translational modifications are distinctly expressed in various normal cell types and malignant cells and are usually detected by immunohistochemistry and flow cytometry in contemporary diagnostics. Here, we describe an approach for simultaneous multiparameter detection of p53, its post-translational modifications and p53 pathway-related signaling proteins in single cells using mass cytometry. Method: We conjugated p53-specific antibodies to metal tags for detection by mass cytometry, allowing the detection of proteins and their post-translational modifications in single cells. We provide an overview of the antibody validation process using relevant biological controls, including cell lines treated in vitro with a stimulus (irradiation) known to induce changes in the expression level of p53. Finally, we present the potential of the method through investigation of primary samples from leukemia patients with distinct TP53 mutational status. Results: The p53 protein can be detected in cell lines and in primary samples by mass cytometry. By combining antibodies for p53-related signaling proteins with a surface marker panel, we show that mass cytometry can be used to decipher the single cell p53 signaling pathway in heterogeneous patient samples. Conclusion: Single cell profiling by mass cytometry allows the investigation of the p53 functionality through examination of relevant downstream signaling proteins in normal and malignant cells. Our work illustrates a novel approach for single cell profiling of p53.

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.

TIFA and TIFAB: FHA-domain proteins involved in inflammation, hematopoiesis, and disease

Forkhead-associated (FHA) domain-containing proteins are widely expressed across eubacteria and in eukaryotes. FHA domains contain phosphopeptide recognition motifs, which operate in a variety of phosphorylation-dependent and -independent biological processes, including the DNA damage response, signal transduction, and regulation of the cell cycle. More recently, two FHA domain-containing proteins were discovered in mammalian cells as tumor necrosis factor receptor-associated factor (TRAF)-interacting proteins: TIFA and TIFAB. TIFA and TIFAB are important modifiers of the innate immune signaling through their regulation of TRAF proteins. Recent studies have also revealed distinct roles for TIFA and TIFAB in the context of immune cell function, chronic inflammation, hematopoiesis, and hematologic disorders. Collectively, these studies indicate the important role of TIFA- and TIFAB-dependent signaling in hematopoietic cells and their dysregulation in several human diseases. In this review, we summarize the molecular mechanisms and biological role of these FHA-domain homologues, placing them into the context of human disease.

High-level MYC expression associates with poor survival in patients with acute myeloid leukemia and collaborates with overexpressed p53 in leukemic transformation in patients with myelodysplastic syndrome

INTRODUCTION

Patients with mutated and overexpressed p53 have an aggressive course in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Studies on the impact of MYC expression in AML are limited. This is the first study to evaluate MYC expression and p53 status in AML and MDS.

METHODS

We identified 214 patients, 101 AML, 79 MDS, and 34 negative control patients. We retrospectively assessed p53 and MYC expression by immunohistochemistry and correlated MYC expression with p53 expression and aberrational status of TP53.

RESULTS

The level of both p53 and MYC expression was significantly higher in AML (mean: 9.7%; 12.1%) and MDS (mean: 5.2%; 5.5%) patients compared with control cases (mean: 0.18%; 2.3%; P = .001-0.02). p53 and MYC expression levels were even more elevated in AML when compared to MDS patients (P < .001). MYC expression was significantly associated with p53 expression and TP53 aberration in AML patients but not in MDS patients (P < .001). p53 expression and >20% MYC expression showed an adverse impact on overall survival (OS) (P < .05) in AML patients while p53 but not MYC expression showed an adverse impact on OS in MDS patients. MYC and p53 dual expression, as well as combined MYC expression and TP53 aberration, showed negative impact on OS in AML patients. MDS patients with leukemic transformation revealed an interval increase in expression of both p53 and MYC.

CONCLUSION

High-level MYC expression associates with p53 abnormality and poor survival in AML. MYC may provide proliferative advantage for leukemic progression in p53 dependent and independent manner.

p53 is associated with high-risk and pinpoints TP53 missense mutations in mantle cell lymphoma

Survival for patients diagnosed with mantle cell lymphoma (MCL) has improved drastically in recent years. However, patients carrying mutations in tumour protein p53 (TP53) do not benefit from modern chemotherapy-based treatments and have poor prognosis. Thus, there is a clinical need to identify missense mutations through routine analysis to enable patient stratification. Sequencing is not widely implemented in clinical practice for MCL, and immunohistochemistry (IHC) is a feasible alternative to identify high-risk patients. The aim of the present study was to investigate the accuracy of p53 as a tool to identify patients with TP53 missense mutations and the prognostic impact of overexpression and mutations in a Swedish population-based cohort. In total, 317 cases were investigated using IHC and 255 cases were sequenced, enabling analysis of p53 and TP53 status among 137 cases divided over the two-cohort investigated. The accuracy of predicting missense mutations from protein expression was 82%, with sensitivity at 82% and specificity at 100% in paired samples. We further show the impact of p53 expression and TP53 mutations on survival (hazard ratio of 3·1 in univariate analysis for both), and the association to risk factors, such as high MCL International Prognostic Index, blastoid morphology and proliferation, in a population-based setting.

Myelodysplastic syndromes: a review of therapeutic progress over the past 10 years

INTRODUCTION

Myelodysplastic syndromes (MDS) represent a range of bone marrow disorders, with patients affected by cytopenias and risk of progression to AML. There are limited therapeutic options available for patients, including hypomethylating agents (azacitidine/decitabine), growth factor support, lenalidomide, and allogeneic stem cell transplant.

AREAS COVERED

This review provides an overview of the progress made over the past decade for emerging therapies for lower- and higher-risk MDS (MDS-HR). We also cover advances in prognostication, supportive care, and use of allogeneic SCT in MDS.

EXPERT OPINION

While there have been no FDA-approved therapies for MDS in the past decade, we anticipate the approval of luspatercept based on results from the MEDALIST trial for patients with lower-risk MDS (MDS-LR) and ringed sideroblasts who have failed or are ineligible for erythropoiesis stimulating agents (ESAs). With growing knowledge of the biologic and molecular mechanisms underlying MDS, it is anticipated that new therapies will be approved in the coming years.

Do next-generation sequencing results drive diagnostic and therapeutic decisions in MDS?

This article has a companion Point by Thol and Platzbecker.

Myeloid neoplasms in the setting of sickle cell disease: an intrinsic association with the underlying condition rather than a coincidence; report of 4 cases and review of the literature

Myeloid neoplasms occasionally occur in patients with sickle cell disease, and the underlying connection between the two diseases is unclear. Herein, we retrospectively analyzed four cases of sickle cell disease patients who developed myeloid neoplasm. Age at time of diagnosis ranged from 27 to 59 years with a median of 35.5 years. Two patients were treated with hydroxyurea and the other two with supportive care alone, with one out of the four patients receiving additional treatment with hematopoietic stem cell transplant. Three patients presented with leukocytosis, and the remaining patient presented with pancytopenia. Two patients were diagnosed with myelodysplastic syndrome/myeloproliferative neoplasm, one with myelodysplastic syndrome, and the other with acute myeloid leukemia. All four cases demonstrated certain degrees of myelodysplasia and complex cytogenetic abnormalities with - 7/7q- and/or - 5/5q- or with 11q23 (KMT2A) rearrangement. This cytogenetic profile resembles that seen in therapy-related myeloid neoplasm, suggesting that myeloid neoplasm in the setting of sickle cell disease may represent a subcategory of the disease distinct from de novo myeloid neoplasm in general. Extensive literature review further demonstrates this similarity in cytogenetic profile, as well as in other associated pathologic features. Potential etiology includes therapy for sickle cell disease, disease-related immunomodulation, or disease-related chronic inflammation. We hypothesize that constant hematopoietic hyperplasia, stimulated by a hemolysis-induced cytokine storm, may increase the chance of somatic mutations/cytogenetic aberrations, resulting in transformation of myeloid precursors. This group of myeloid neoplasms seems to herald a dismal clinical outcome, with median survival <1 year, although the exact pathogenesis and biology of the disease remain to be investigated by large cohorts in future studies.

MMP9 inhibition increases erythropoiesis in RPS14-deficient del(5q) MDS models through suppression of TGF-β pathways

The del(5q) myelodysplastic syndrome (MDS) is a distinct subtype of MDS, associated with deletion of the ribosomal protein S14 (RPS14) gene that results in macrocytic anemia. This study sought to identify novel targets for the treatment of patients with del(5q) MDS by performing an in vivo drug screen using an rps14-deficient zebrafish model. From this, we identified the secreted gelatinase matrix metalloproteinase 9 (MMP9). MMP9 inhibitors significantly improved the erythroid defect in rps14-deficient zebrafish. Similarly, treatment with MMP9 inhibitors increased the number of colony forming unit-erythroid colonies and the CD71+ erythroid population from RPS14 knockdown human BMCD34+ cells. Importantly, we found that MMP9 expression is upregulated in RPS14-deficient cells by monocyte chemoattractant protein 1. Double knockdown of MMP9 and RPS14 increased the CD71+ population compared with RPS14 single knockdown, suggesting that increased expression of MMP9 contributes to the erythroid defect observed in RPS14-deficient cells. In addition, transforming growth factor β (TGF-β) signaling is activated in RPS14 knockdown cells, and treatment with SB431542, a TGF-β inhibitor, improved the defective erythroid development of RPS14-deficient models. We found that recombinant MMP9 treatment decreases the CD71+ population through increased SMAD2/3 phosphorylation, suggesting that MMP9 directly activates TGF-β signaling in RPS14-deficient cells. Finally, we confirmed that MMP9 inhibitors reduce SMAD2/3 phosphorylation in RPS14-deficient cells to rescue the erythroid defect. In summary, these study results support a novel role for MMP9 in the pathogenesis of del(5q) MDS and the potential for the clinical use of MMP9 inhibitors in the treatment of patients with del(5q) MDS.

Managing anaemia in bone marrow failure syndromes

PURPOSE OF REVIEW

Anaemia is a common haematological presentation in patients with bone marrow failure, yet a challenging condition to treat. As anaemia has a direct impact on the patient's symptoms, managing anaemia in the common bone marrow failure conditions, such as myelodysplastic syndrome will help to improve the quality of life. This review discusses the available treatment options and the benefit of improving the haemoglobin level.

RECENT FINDINGS

Managing anaemia effectively has shown to improve the patient outcome, yet treatment option remain limited. Recently, activin inhibitors such as Luspatercept have shown to be effective in patients' refractory to ESAs and further clinical trials are ongoing to explore this further.

SUMMARY

Transfusion still remains the mainstay of treatment in patients not suitable, lost response or refractory to erythropoiesis-stimulating agents (ESAs). Majority of these patients are not suitable for definite treatment options such as bone marrow transplantation. The aim of treatment remains improving the quality of life and newer therapeutic options may offer better and more sustained response.

Treatment of myelodysplastic syndrome in the era of next-generation sequencing

Next-generation sequencing (NGS) is rapidly changing the clinical care of patients with myelodysplastic syndrome (MDS). NGS can be used for various applications: (i) in the diagnostic process to discriminate between MDS and other diseases such as aplastic anaemia, myeloproliferative disorders and idiopathic cytopenias; (ii) for classification, for example, where the presence of SF3B1 mutation is one criterion for the ring sideroblast anaemia subgroups in the World Health Organization 2016 classification; (iii) for identification of patients suitable for targeted therapy (e.g. IDH1/2 inhibitors); (iv) for prognostication, for example, where specific mutations (e.g. TP53 and RUNX1) are associated with inferior prognosis, whereas others (e.g. SF3B1) are associated with superior prognosis; and (v) to monitor patients for progression or treatment failure. Most commonly, targeted sequencing for genes (normally 50-100 genes) reported to be recurrently mutated in myeloid disease is used. At present, NGS is rarely incorporated into clinical guidelines although an increasing number of studies have demonstrated the benefit of using NGS in the clinical management of MDS patients.

Strong expression of p53 protein in bone marrow samples after hematopoietic stem cell transplantation indicates risk of relapse in pediatric acute lymphoblastic leukemia patients

BACKGROUND

For pediatric ALL patients that relapse or respond poorly to conventional chemotherapy treatment, HSCT is one treatment option. Still, relapse occurs in 30% of the children after HSCT. Mutations in the tumor suppressor gene TP53 which can lead to an altered p53 protein expression are rare at time of diagnosis of ALL, yet occur more frequent at relapse indicating a more aggressive disease. Our aim was to evaluate if alterations in the expression of the tumor suppressor protein p53 signaled a relapse in pediatric ALL patients post-HSCT and could guide for preemptive immunotherapy.

PROCEDURE

Paraffin-embedded bone marrow samples from 46 children diagnosed with ALL between 1997 and 2010, and transplanted at Karolinska University Hospital, were analyzed for p53 by IHC. Samples were analyzed independently at diagnosis, before HSCT, and after HSCT 0-3 months, 3-6 months, and 6-12 months.

RESULT

Strong expression of p53 in the bone marrow at 0-3-months after HSCT was associated with increased risk of relapse, odds ratio 2.63 (confidence interval 1.08-6.40) P = 0.033.

CONCLUSION

Evaluation of p53 protein expression in bone marrow from pediatric ALL patients that undergo HSCT may be a potential, additional prognostic marker for predicting relapse after HSCT.

Prognostic Impact of Immunohistochemical p53 Expression in Bone Marrow Biopsy in Higher Risk MDS: a Pilot Study

Background and objectives

Mutations of the TP53 gene have an unfavorable prognosis in Myelodysplastic Syndromes (MDS). The product of the TP53 gene is the p53 protein. Most of the TP53 mutations entail the accumulation of the protein in the nucleus of tumor cells. The immunohistochemical (IHC) staining for p53 can be a surrogate suggesting a mutational status and, if overexpressed, seems to be of prognostic value by itself. The best prognostic cut-off value of overexpression is controversial. The aim of this pilot study is to investigate the correct value from a homogenous group of patients with higher IPSS-R risk MDS.

Methods

In sixty consecutive patients diagnosed with MDS and categorized as “intermediate,” “high” and “very high” IPSS-risk, the bone marrow biopsies performed at diagnosis were retrospectively re-examined for IHC p53 expression. The result of p53 expression was subsequently related to survival.

Results

A worse overall survival was observed both in patients whose IHC p53 expression was ≥5% and ≥ 10% compared to patients with a p53 expression below 5% (p= 0.0063) or 10% (p=0.0038) respectively.

Conclusions

The ICH p53 expression in bone marrow biopsy in higher risk MDS was confirmed to have prognostic value. These results indicate more than 10% expression as the best cut off value.

Molecular pathogenesis of myelodysplastic syndromes with deletion 5q

The molecular pathogenesis of deletion 5q (del(5q)) myelodysplastic syndrome (MDS) has recently been realized as a result of major advances in our understanding of the mechanisms responsible for clinical phenotype. Identification of commonly deleted genes such as RPS14, miRNA-145, HSPA9, CD78, and CSNK1a1 have elucidated the precise biological changes responsible for the anemia, leukopenia, and thrombocytosis that characterizes del(5q) MDS and highlighted the importance of allelic haploinsufficiency in the hematological phenotype. Recent elegant investigations have also identified a critical role of innate immune signaling in del(5q) pathogenesis. TP53 and Wnt/β-catenin pathways have also been found to be involved in clonal expansion and progression of the disease as well as resistance and poor outcomes to available therapy. Understanding the molecular pathogenesis of the disease has provided a critical foundation in identifying the biological targets of lenalidomide in del(5q) MDS, which has led to the development of novel therapeutic agents in hematologic malignancies as well as potential alternative targets to exploit in patients who have failed lenalidomide treatment.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Dual inhibition of MDM2 and MDM4 in virus-positive Merkel cell carcinoma enhances the p53 response

Merkel cell polyomavirus (MCV) contributes to approximately 80% of all Merkel cell carcinomas (MCCs), a highly aggressive neuroendocrine carcinoma of the skin. MCV-positive MCC expresses small T antigen (ST) and a truncated form of large T antigen (LT) and usually contains wild-type p53 (TP53) and RB (RB1). In contrast, virus-negative MCC contains inactivating mutations in TP53 and RB1. While the MCV-truncated LT can bind and inhibit RB, it does not bind p53. We report here that MCV LT binds to RB, leading to increased levels of ARF, an inhibitor of MDM2, and activation of p53. However, coexpression of ST reduced p53 activation. MCV ST recruits the MYC homologue MYCL (L-Myc) to the EP400 chromatin remodeler complex and transactivates specific target genes. We observed that depletion of EP400 in MCV-positive MCC cell lines led to increased p53 target gene expression. We suspected that the MCV ST-MYCL-EP400 complex could functionally inactivate p53, but the underlying mechanism was not known. Integrated ChIP and RNA-sequencing analysis following EP400 depletion identified MDM2 as well as CK1α, an activator of MDM4, as target genes of the ST-MYCL-EP400 complex. In addition, MCV-positive MCC cells expressed high levels of MDM4. Combining MDM2 inhibitors with lenalidomide targeting CK1α or an MDM4 inhibitor caused synergistic activation of p53, leading to an apoptotic response in MCV-positive MCC cells and MCC-derived xenografts in mice. These results support dual targeting of MDM2 and MDM4 in virus-positive MCC and other p53 wild-type tumors.

Presence of CD34+ in Megakaryocytes in Association With p53 Expression Predicts Unfavorable Prognosis in Low-risk Myelodysplastic Syndrome Patients

BACKGROUND/AIM

Although risk stratification using the Prognostic Scores Systems (IPSS, WPSS and IPSS-R) incorporate key information about prognosis of patients with Myelodysplastic syndromes (MDS), patients classified as low-risk may evolve rapidly and aggressively, despite a "favorable" prognostic stratification. The aim of this study was to identify biomarkers for predicting prognosis, and for better stratification and management of these patients.

MATERIALS AND METHODS

Expression of CD34 and p53 in megakaryocytes was examined by immunohistochemistry in 71 MDS patients classified as low-risk.

RESULTS

CD34 staining in megakaryocytes was associated with p53 expression (p=0.0166). CD34 and p53 expression were associated to worse overall survival in patients (p=0.0281).

CONCLUSION

The presence of CD34 in megakaryocytes is associated with p53 expression and an adverse prognosis for MDS patients.

P53 protein overexpression in de novo acute myeloid leukemia patients with normal diploid karyotype correlates with FLT3 internal tandem duplication and worse relapse-free survival

Although ~50% of acute myeloid leukemia (AML) patients have a normal diploid karyotype by conventional cytogenetics at diagnosis, this patient subset has a variable disease course and outcome. Aberrant overexpression of the p53 protein is usually associated with TP53 alterations and a complex karyotype, but the prevalence and impact of p53 overexpression in AML with diploid cytogenetics is unknown. We examined 100 newly diagnosed AML patients to evaluate the impact of p53 expression status quantified in bone marrow core biopsy samples using immunohistochemistry and computer-assisted image analysis. A total of 24 patients had p53 overexpression defined as 3+ staining intensity in ≥5% of cells; this finding correlated with lower platelet counts (P = .002), absence of CD34 expression in blasts (P = .009), higher bone marrow blast counts (P = .04), and a higher frequency of FLT3 internal tandem duplication (P = .007). Overexpression of p53 independently predicted for shorter leukemia-free survival in patients who underwent allogeneic stem cell transplantation by univariate (P = .021) and multivariate analyses (P = .004). There was no correlation between MDM2 and p53 protein expression in this cohort. We conclude that p53 expression evaluated by immunohistochemistry in bone marrow biopsy specimens at the time of AML diagnosis may indicate distinct clinical characteristics in patients with normal diploid cytogenetics and is a potentially valuable tool that can enhance risk-stratification.

Differences in the bone marrow histology between childhood myelodysplastic syndrome with multilineage dysplasia and refractory cytopenia of childhood without multilineage dysplasia

AIMS

Refractory cytopenia of childhood (RCC) is subdivided into myelodysplastic syndrome with multilineage dysplasia (MDS-MLD) and RCC without (w/o) multilineage dysplasia (RCC without MLD). Although RCC is a histomorphological distinct entity, the bone marrow (BM) histology of RCC is not yet characterised in relation to multilineage dysplasia. We investigated the BM histological features of RCC to clarify the characteristics of BM histology of MDS-MLD in childhood compared to RCC without MLD.

METHODS AND RESULTS

The BM histology and cytology in 60 RCC patients from the nationwide registry of Japanese Childhood AA-MDS Study Group were reviewed retrospectively. Although a thorough genetic assessment, including GATA2 and/or SAMD9, was not performed, inherited BM failure disorders were excluded by a cytogenetic test, a chromosome fragility test and a telomere length measurement along with careful clinical assessments. Among the 60 patients, 20 (33%) of MDS-MLD and 40 (67%) of RCC w/o MLD were classified according to their BM cytology. We then investigated the BM histological features and compared them between the two groups. The BM cellularity, distribution pattern of haematopoiesis, frequency of left-shifted granulopoiesis, numbers of micromegakaryocytes and p53 immunostaining-positive cells were significantly different between the groups. The BM histology of MDS-MLD in childhood showed higher cellularity, the more common occurrence of diffuse distribution pattern, more frequently left-shifted granulopoiesis and more micromegakaryocytes and p53 immunostaining-positive cells than RCC without MLD.

CONCLUSIONS

Our results showed that MDS-MLD in childhood had a characteristic BM histology compared to RCC without MLD. The clinical relevance of MDS-MLD in childhood needs to be evaluated.

Crbn I391V is sufficient to confer in vivo sensitivity to thalidomide and its derivatives in mice

Thalidomide and its derivatives, lenalidomide and pomalidomide, are clinically effective treatments for multiple myeloma and myelodysplastic syndrome with del(5q). These molecules lack activity in murine models, limiting investigation of their therapeutic activity or toxicity in vivo. Here, we report the development of a mouse model that is sensitive to thalidomide derivatives because of a single amino acid change in the direct target of thalidomide derivatives, cereblon (Crbn). In human cells, thalidomide and its analogs bind CRBN and recruit protein targets to the CRL4CRBN E3 ubiquitin ligase, resulting in their ubiquitination and subsequent degradation by the proteasome. We show that mice with a single I391V amino acid change in Crbn exhibit thalidomide-induced degradation of drug targets previously identified in human cells, including Ikaros (Ikzf1), Aiolos (Ikzf3), Zfp91, and casein kinase 1a1 (Ck1α), both in vitro and in vivo. We use the Crbn I391V model to demonstrate that the in vivo therapeutic activity of lenalidomide in del(5q) myelodysplastic syndrome can be explained by heterozygous expression of Ck1α in del(5q) cells. We found that lenalidomide acts on hematopoietic stem cells with heterozygous expression of Ck1α and inactivation of Trp53 causes lenalidomide resistance. We further demonstrate that Crbn I391V is sufficient to confer thalidomide-induced fetal loss in mice, capturing a major toxicity of this class of drugs. Further study of the Crbn I391V model will provide valuable insights into the in vivo efficacy and toxicity of this class of drugs.

Patterns of mutations in TP53 mutated AML

TP53 mutated acute myeloid leukemia (AML) responds poorly to chemotherapy and has a short overall survival rate with a median of 5-9 months. Poor outcomes in TP53 mutated AML following chemotherapy have been observed and treatment options remain limited, although the presence of TP53 mutations alone should not be a barrier to therapy. Decitabine is emerging as an alternative treatment option for patients with TP53 mutated AML, although the agent has not been associated with deep molecular remissions and requires additional consolidation. The clinical and genomic characteristics of TP53 mutated AML are reviewed in this paper.

The histopathology of bone marrow failure in children

Bone marrow failure (BMF) is a rare but life-threatening disorder that usually manifests as (pan)cytopenia. BMF can be caused by a variety of diseases, but inherited BMF (IBMF) syndromes are a clinically important cause, especially in children. IBMF syndromes are a heterogeneous group of genetic disorders characterized by BMF, physical abnormalities, and predisposition to malignancy. An accurate diagnosis is critical, as disease-specific management, surveillance, and genetic counselling are required for each patient. The major differential diagnoses of IBMF syndromes are acquired aplastic anemia (AA) and refractory cytopenia of childhood (RCC). These diseases have overlapping features, such as BM hypocellularity and/or dysplastic changes, which make the differential diagnosis challenging. RCC has been defined as a histomorphologically distinct entity. Therefore, understanding the BM histopathology of these diseases is essential for the differential diagnosis. However, the BM histopathological features have not been characterized in detail, as descriptions of BM histopathology are very limited due to the rarity of the diseases. This review provides a detailed description of the BM histopathology in cases of RCC, AA, and the four most common IBMF syndromes: Fanconi anemia (FA), dysketatosis congenita (DC), Diamond-Blackfan anemia (DBA), and Shwachman-Diamond syndrome (SDS). An overview, including the clinical features and diagnosis, is also provided.

Histological evaluation of myeloproliferative neoplasms

In 2017, the revised World Health Organization was published. Regarding myeloproliferative neoplasms, histological findings of bone marrow biopsy is becoming more important for diagnosis. This article highlights particularly the morphology of megakaryocytes and evaluation of myelofibrosis for pathological diagnosis, and immunohistochemistry which can detect somatic mutation.

Challenges in Diagnosing Myelodysplastic Syndromes in the Era of Genetic Testing: Proceedings of the 13th Workshop of the European Bone Marrow Working Group

The 13th workshop of the European Bone Marrow Working Group in Utrecht, The Netherlands, was devoted to studying myelodysplastic syndromes (MDS) and their boundaries. The panel received 44 cases submitted to the 3 invited categories, which included: reactive cytopenias with dysplasia, idiopathic cytopenia of undetermined significance, clonal haematopoiesis of indeterminate potential, idiopathic dysplasia of uncertain significance and overt MDS. For this summary, we have selected 17 cases that highlight difficulties in separating true MDS from other causes of cytopenia and the intricate relationship between clonal haematopoiesis and true MDS. In addition, cases of overt MDS with challenging features were also selected. All cases were stained for p53 expression. Using instructive submitted cases we discuss the following: (1) cytopenia with clonal haematopoiesis not fulfilling MDS criteria, (2) cytopenia and/or dysplasia with germline mutations and/or familial history suggesting an underlying gene defect, (3) MDS based on a recurrent chromosomal abnormality and (4) overt MDS with diagnostic difficulties due to concurrent treatment or disease. The lively discussion in the open forum of the workshop illustrated the need for better integrative understanding of the evolution of acquired genetic abnormalities in haematopoiesis, and the challenge of diagnosing true MDS in cytopenic patients with genetic abnormalities, either germline or acquired.

Acute Myeloid Leukemia: The Good, the Bad, and the Ugly

Acute myeloid leukemia (AML) was initially subdivided according to morphology (the French-American-British system), which proved helpful in pathologic categorization. Subsequently, clinical and genomic factors were found to correlate with response to chemotherapy and with overall survival. These included a history of antecedent hematologic disease, a history of chemotherapy or radiation therapy, the presence of various recurrent cytogenetic abnormalities, and, more recently, the presence of specific point mutations. This article reviews the biology and responses of one AML subgroup with consistent response and good outcomes following chemotherapy (core-binding factor leukemia), and two subgroups with persistently bad, and even ugly, outcomes (secondary AML and TP53-mutated AML).

Early detection and evolution of preleukemic clones in therapy-related myeloid neoplasms following autologous SCT

tMNs after ASCT originate from HSCs bearing (pre-)tMN mutations that are present years before disease onset. Post-ASCT treatment can influence selection and outgrowth of (pre)leukemic clones.