Martin Jädersten

TP53 Mutations in Low-Risk Myelodysplastic Syndromes With del(5q) Predict Disease Progression

PURPOSE To determine the frequency of TP53 mutations and the level of p53 protein expression by immunohistochemistry (IHC) in low-risk myelodysplastic syndromes (MDS) with del(5q) and to assess their impact on disease progression. PATIENTS AND METHODS Pre- and postprogression bone marrow (BM) samples from 55 consecutive patients with International Prognostic Scoring System low risk (n = 32) or intermediate-1 risk (n = 23) were studied by next-generation sequencing of TP53. IHC for p53 was performed on 148 sequential BM samples. RESULTS TP53 mutations with a median clone size of 11% (range, 1% to 54%) were detected in 10 patients (18%) already at an early phase of the disease. Mutations were equally common in low-risk and intermediate-1-risk patients and were associated with evolution to acute myeloid leukemia (5 of 10 v 7 of 45; P = .045). Nine of 10 patients carrying mutations showed more than 2% BM progenitors with strong p53 staining. The probability of a complete cytogenetic response to lenalidomide was lower in mutated patients (0 of 7 v 12 of 24; P = .024). CONCLUSION By using sensitive deep-sequencing technology, we demonstrated that TP53 mutated populations may occur at an early disease stage in almost a fifth of low-risk MDS patients with del(5q). Importantly, mutations were present years before disease progression and were associated with an increased risk of leukemic evolution. TP53 mutations could not be predicted by common clinical features but were associated with p53 overexpression. Our findings indicate a previously unrecognized heterogeneity of the disease which may significantly affect clinical decision making.

Lenalidomide inhibits the malignant clone and up-regulates the SPARC gene mapping to the commonly deleted region in 5q− syndrome patients

Myelodysplastic syndromes (MDSs) are a group of hematopoietic stem cell disorders characterized by ineffective hematopoiesis and peripheral blood cytopenias. Lenalidomide has dramatic therapeutic effects in patients with low-risk MDS and a chromosome 5q31 deletion, resulting in complete cytogenetic remission in >60% of patients. The molecular basis of this remarkable drug response is unknown. To gain insight into the molecular targets of lenalidomide we investigated its in vitro effects on growth, maturation, and global gene expression in isolated erythroblast cultures from MDS patients with del(5)(q31). Lenalidomide inhibited growth of differentiating del(5q) erythroblasts but did not affect cytogenetically normal cells. Moreover, lenalidomide significantly influenced the pattern of gene expression in del(5q) intermediate erythroblasts, with the VSIG4, PPIC, TPBG, activin A, and SPARC genes up-regulated by >2-fold in all samples and many genes involved in erythropoiesis, including HBA2, GYPA, and KLF1, down-regulated in most samples. Activin A, one of the most significant differentially expressed genes between lenalidomide-treated cells from MDS patients and healthy controls, has pleiotropic functions, including apoptosis of hematopoietic cells. Up-regulation and increased protein expression of the tumor suppressor gene SPARC is of particular interest because it is antiproliferative, antiadhesive, and antiangiogenic and is located at 5q31-q32, within the commonly deleted region in MDS 5q− syndrome. We conclude that lenalidomide inhibits growth of del(5q) erythroid progenitors and that the up-regulation of SPARC and activin A may underlie the potent effects of lenalidomide in MDS with del(5)(q31). SPARC may play a role in the pathogenesis of the 5q− syndrome.

Erythropoietin and Granulocyte-Colony Stimulating Factor Treatment Associated With Improved Survival in Myelodysplastic Syndrome

PURPOSE To assess the effect of erythropoietin (EPO) plus granulocyte-colony stimulating factor (G-CSF) treatment on survival and leukemic transformation in myelodysplastic syndrome (MDS). PATIENTS AND METHODS We compared the long-term outcome of patients with MDS treated with EPO plus G-CSF (n = 121) with untreated patients (n = 237) with MDS using multivariate Cox regression with delayed entry, for the first time adjusting for all major prognostic variables (WHO classification, karyotype, cytopenias, level of transfusion-need, age, and sex). RESULTS The erythroid response rate to EPO plus G-CSF was 39%, and the median response duration 23 months (range, 3 to 116+). In the multivariate analysis, treatment was associated with improved overall survival (hazard ratio, 0.61; 95% CI, 0.44 to 0.83; P = .002). Interestingly, this positive association was primarily observed in patients requiring fewer than 2 units of RBCs per month. Treatment was not linked to the rate of acute myeloid leukemia in any defined subgroup, including patients with an increase of marrow blasts or an unfavorable karyotype. CONCLUSION The inherent risk of leukemic evolution in MDS makes the current investigation highly relevant, in light of the recent reports of potential negative effects of EPO treatment on outcome in patients with cancer. We conclude that treatment of anemia in MDS with EPO plus G-CSF may have a positive impact on outcome in patients with no or low transfusion need, while not affecting the risk of leukemic transformation.

Frequent mutation of the polycomb-associated gene ASXL1 in the myelodysplastic syndromes and in acute myeloid leukemia

Frequent mutation of the polycomb-associated gene ASXL1 in the myelodysplastic syndromes and in acute myeloid leukemia

Deregulated gene expression pathways in myelodysplastic syndrome hematopoietic stem cells.

To gain insight into the molecular pathogenesis of the myelodysplastic syndromes (MDS), we performed global gene expression profiling and pathway analysis on the hematopoietic stem cells (HSC) of 183 MDS patients as compared with the HSC of 17 healthy controls. The most significantly deregulated pathways in MDS include interferon signaling, thrombopoietin signaling and the Wnt pathways. Among the most significantly deregulated gene pathways in early MDS are immunodeficiency, apoptosis and chemokine signaling, whereas advanced MDS is characterized by deregulation of DNA damage response and checkpoint pathways. We have identified distinct gene expression profiles and deregulated gene pathways in patients with del(5q), trisomy 8 or −7/del(7q). Patients with trisomy 8 are characterized by deregulation of pathways involved in the immune response, patients with −7/del(7q) by pathways involved in cell survival, whereas patients with del(5q) show deregulation of integrin signaling and cell cycle regulation pathways. This is the first study to determine deregulated gene pathways and ontology groups in the HSC of a large group of MDS patients. The deregulated pathways identified are likely to be critical to the MDS HSC phenotype and give new insights into the molecular pathogenesis of this disorder, thereby providing new targets for therapeutic intervention.

Gene expression profiling of CD34+ cells in patients with the 5q− syndrome

The transcriptome of the CD34+ cells was determined in a group of 10 patients with the 5q− syndrome using a comprehensive array platform, and was compared with the transcriptome of CD34+ cells from 16 healthy control subjects and 14 patients with refractory anaemia and a normal karyotype. The majority of the genes assigned to the commonly deleted region (CDR) of the 5q− syndrome at 5q31–q32 showed a reduction in expression levels in patients with the 5q− syndrome, consistent with the loss of one allele. Candidate genes showing haploinsufficiency in the 5q− syndrome included the tumour suppressor gene SPARC and RPS14, a component of the 40S ribosomal subunit. Two genes mapping to the CDR, RBM22 and CSNK1A1, showed a >50% reduction in gene expression, consistent with the downregulation of the remaining allele. This study identified several significantly deregulated gene pathways in patients with the 5q− syndrome and gene pathway analysis data supports the proposal that SPARC may play a role in the pathogenesis of the 5q− syndrome. This study suggests that several of the genes mapping to the CDR of the 5q− syndrome play a role in the pathogenesis of this disorder.

Role of Reduced-Intensity Conditioning Allogeneic Hematopoietic Stem-Cell Transplantation in Older Patients With De Novo Myelodysplastic Syndromes: An International Collaborative Decision Analysis

PURPOSE Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders that are more common in patients aged ≥ 60 years and are incurable with conventional therapies. Reduced-intensity conditioning (RIC) allogeneic hematopoietic stem-cell transplantation is potentially curative but has additional mortality risk. We evaluated RIC transplantation versus nontransplantation therapies in older patients with MDS stratified by International Prognostic Scoring System (IPSS) risk. PATIENTS AND METHODS A Markov decision model with quality-of-life utility estimates for different MDS and transplantation states was assessed. Outcomes were life expectancy (LE) and quality-adjusted life expectancy (QALE). A total of 514 patients with de novo MDS aged 60 to 70 years were evaluated. Chronic myelomonocytic leukemia, isolated 5q- syndrome, unclassifiable, and therapy-related MDS were excluded. Transplantation using T-cell depletion or HLA-mismatched or umbilical cord donors was also excluded. RIC transplantation (n = 132) stratified by IPSS risk was compared with best supportive care for patients with nonanemic low/intermediate-1 IPSS (n = 123), hematopoietic growth factors for patients with anemic low/intermediate-1 IPSS (n = 94), and hypomethylating agents for patients with intermediate-2/high IPSS (n = 165). RESULTS For patients with low/intermediate-1 IPSS MDS, RIC transplantation LE was 38 months versus 77 months with nontransplantation approaches. QALE and sensitivity analysis did not favor RIC transplantation across plausible utility estimates. For intermediate-2/high IPSS MDS, RIC transplantation LE was 36 months versus 28 months for nontransplantation therapies. QALE and sensitivity analysis favored RIC transplantation across plausible utility estimates. CONCLUSION For patients with de novo MDS aged 60 to 70 years, favored treatments vary with IPSS risk. For low/intermediate-1 IPSS, nontransplantation approaches are preferred. For intermediate-2/high IPSS, RIC transplantation offers overall and quality-adjusted survival benefit.

SF3B1 mutation identifies a distinct subset of myelodysplastic syndrome with ring sideroblasts

Refractory anemia with ring sideroblasts (RARS) is a myelodysplastic syndrome (MDS) characterized by isolated erythroid dysplasia and 15% or more bone marrow ring sideroblasts. Ring sideroblasts are found also in other MDS subtypes, such as refractory cytopenia with multilineage dysplasia and ring sideroblasts (RCMD-RS). A high prevalence of somatic mutations of SF3B1 was reported in these conditions. To identify mutation patterns that affect disease phenotype and clinical outcome, we performed a comprehensive mutation analysis in 293 patients with myeloid neoplasm and 1% or more ring sideroblasts. SF3B1 mutations were detected in 129 of 159 cases (81%) of RARS or RCMD-RS. Among other patients with ring sideroblasts, lower prevalence of SF3B1 mutations and higher prevalence of mutations in other splicing factor genes were observed (P < .001). In multivariable analyses, patients with SF3B1 mutations showed significantly better overall survival (hazard ratio [HR], .37; P = .003) and lower cumulative incidence of disease progression (HR = 0.31; P = .018) compared with SF3B1-unmutated cases. The independent prognostic value of SF3B1 mutation was retained in MDS without excess blasts, as well as in sideroblastic categories (RARS and RCMD-RS). Among SF3B1-mutated patients, coexisting mutations in DNA methylation genes were associated with multilineage dysplasia (P = .015) but had no effect on clinical outcome. TP53 mutations were frequently detected in patients without SF3B1 mutation, and were associated with poor outcome. Thus, SF3B1 mutation identifies a distinct MDS subtype that is unlikely to develop detrimental subclonal mutations and is characterized by indolent clinical course and favorable outcome.

The Role of the Iron Transporter ABCB7 in Refractory Anemia with Ring Sideroblasts

Refractory Anemia with Ring Sideroblasts (RARS) is an acquired myelodysplastic syndrome (MDS) characterized by an excess iron accumulation in the mitochondria of erythroblasts. The pathogenesis of RARS and the cause of this unusual pattern of iron deposition remain unknown. We considered that the inherited X-linked sideroblastic anemia with ataxia (XLSA/A) might be informative for the acquired disorder, RARS. XLSA/A is caused by partial inactivating mutations of the ABCB7 ATP-binding cassette transporter gene, which functions to enable transport of iron from the mitochondria to the cytoplasm. Furthermore, ABCB7 gene silencing in HeLa cells causes an accumulation of iron in the mitochondria. We have studied the role of ABCB7 in RARS by DNA sequencing, methylation studies, and gene expression studies in primary CD34+ cells and in cultured erythroblasts. The DNA sequence of the ABCB7 gene is normal in patients with RARS. We have investigated ABCB7 gene expression levels in the CD34+ cells of 122 MDS cases, comprising 35 patients with refractory anemia (RA), 33 patients with RARS and 54 patients with RA with excess blasts (RAEB), and in the CD34+ cells of 16 healthy controls. We found that the expression levels of ABCB7 are significantly lower in the RARS group. RARS is thus characterized by lower levels of ABCB7 gene expression in comparison to other MDS subtypes. Moreover, we find a strong relationship between increasing percentage of bone marrow ring sideroblasts and decreasing ABCB7 gene expression levels. Erythroblast cell cultures confirm the low levels of ABCB7 gene expression levels in RARS. These data provide an important link between inherited and acquired forms of sideroblastic anemia and indicate that ABCB7 is a strong candidate gene for RARS.

Clonal heterogeneity in the 5q- syndrome: p53 expressing progenitors prevail during lenalidomide treatment and expand at disease progression

Transformation to acute myeloid leukemia may occur in patients with myelodysplastic syndrome with isolated del(5q) treated with lenalidomide, particularly in those without a cytogenetic response. In this study, the authors performed molecular investigations in a patient with classical 5q- syndrome with complete erythroid and partial cytogenetic response to lenalidomide, who later developed high-risk myelodysplastic syndrome with a complex karyotype. Clonal heterogeneity has not been described in patients with myelodysplastic syndrome with isolated del(5q), for which lenalidomide has emerged as a highly potent treatment. However, transformation to acute myeloid leukemia is occasionally observed, particularly in patients without a cytogenetic response to lenalidomide. We performed molecular studies in a patient with classical 5q- syndrome with complete erythroid and partial cytogenetic response to lenalidomide, who evolved to high-risk myelodysplastic syndrome with complex karyotype. Immunohistochemistry of pre-treatment marrow biopsies revealed a small fraction of progenitors with overexpression of p53 and sequencing confirmed a TP53 mutation. TP53 mutated subclones have not previously been described in myelodysplastic syndrome with isolated del(5q) and indicates a previously unknown heterogeneity of this disease. The aberrant subclone remained stable during the treatment with lenalidomide and expanded at transformation, suggesting that this pre-existing cell population had molecular features which made it insensitive to lenalidomide and prone to disease progression.