Myelodysplastic syndrome (MDS) is characterized by ineffective hematopoiesis with morphologic dysplasia and a propensity to transform into overt acute myeloid leukemia (AML). Our analysis of two ...cohorts of 20 MDS and 49 AML with multi‐lineage dysplasia patients shows a reduction in Nucleophosmin 1 (NPM1) expression in 70% and 90% of cases, respectively. A mouse model of Npm1 conditional knockout (cKO) in hematopoietic cells reveals that Npm1 loss causes premature aging of hematopoietic stem cells (HSCs). Mitochondrial activation in Npm1‐deficient HSCs leads to aberrant activation of the NLRP3 inflammasome, which correlates with a developing MDS‐like phenotype. Npm1 cKO mice exhibit shortened survival times, and expansion of both the intra‐ and extra‐medullary myeloid populations, while evoking a p53‐dependent response. After transfer into a p53 mutant background, the resulting Npm1/p53 double KO mice develop fatal leukemia within 6 months. Our findings identify NPM1 as a regulator of HSC aging and inflammation and highlight the role of p53 in MDS progression to leukemia.
SYNOPSIS
Mitochondrial alterations and increased inflammation in Npm1 cKO mice result in HSC aging and MDS‐like phenotypes. p53 dependent responses in Npm1 cKO mice lead to bone marrow failure, while Npm1/p53 double KO mice develop leukemia.
MDS and MLD in AML patients show reduced levels of NPM1.
Npm1 loss causes mitochondrial activation, triggering the NLRP3 inflammasome and premature aging of HSCs.
The p53‐dependent response induced by Npm1 loss results in bone marrow failure.
Npm1/p53 double KO mice develop fatal leukemia within 6 months.
Mitochondrial alterations and increased inflammation in Npm1 cKO mice result in HSC aging and MDS‐like phenotypes. p53 dependent responses in Npm1 cKO mice lead to bone marrow failure, while Npm1/p53 double KO mice develop leukemia.
Cells of the osteoblast lineage affect the homing and the number of long-term repopulating haematopoietic stem cells, haematopoietic stem cell mobilization and lineage determination and B cell ...lymphopoiesis. Osteoblasts were recently implicated in pre-leukaemic conditions in mice. However, a single genetic change in osteoblasts that can induce leukaemogenesis has not been shown. Here we show that an activating mutation of β-catenin in mouse osteoblasts alters the differentiation potential of myeloid and lymphoid progenitors leading to development of acute myeloid leukaemia with common chromosomal aberrations and cell autonomous progression. Activated β-catenin stimulates expression of the Notch ligand jagged 1 in osteoblasts. Subsequent activation of Notch signalling in haematopoietic stem cell progenitors induces the malignant changes. Genetic or pharmacological inhibition of Notch signalling ameliorates acute myeloid leukaemia and demonstrates the pathogenic role of the Notch pathway. In 38% of patients with myelodysplastic syndromes or acute myeloid leukaemia, increased β-catenin signalling and nuclear accumulation was identified in osteoblasts and these patients showed increased Notch signalling in haematopoietic cells. These findings demonstrate that genetic alterations in osteoblasts can induce acute myeloid leukaemia, identify molecular signals leading to this transformation and suggest a potential novel pharmacotherapeutic approach to acute myeloid leukaemia.
Background & Aims
Tufting enteropathy (TE) is a rare congenital disorder often caused by mutations in the gene encoding epithelial cell adhesion molecule (EpCam). The disease leads to diarrhoea, ...intestinal failure and dependence on total parenteral nutrition (TPN). These patients often have liver impairments, but the pathology and mechanism of the damage are not well understood. We evaluated liver biopsies from TE patients to understand the pathophysiology.
Methods
We identified three patients with TE who underwent liver biopsy. Two normal controls and 45 patients on TPN secondary to short gut syndrome were selected for comparison (five were age‐ and TPN duration matched to the TE patients).
Results
We found that all TE patients showed a complete loss of EpCam expression in enterocytes and biliary epithelial cells, while the normal and TPN groups show basolateral expression. Histologically TE patients showed ductopenia, which was not seen in control groups. E‐cadherin and β‐catenin are normally located along the lateral membrane of biliary epithelial cells. However, they were relocated to the apical membrane in TE patients, indicating a defect in the apical‐basal polarity of cholangiocytes. We examined hepatic reparative cells and found near absence of hepatic progenitor cells and intermediate hepatobiliary cells with mild reactive ductular cells in TE patients.
Conclusion
Our findings show that TE is associated with disrupted polarity of cholangiocyte and ductopenia. We demonstrate for the first time a role of EpCam in the maintenance of integrity of biliary epithelium. We also provided evidence for a disrupted development of hepatic reparative cells.
Immunohistochemistry has recently emerged as a powerful ancillary tool for differentiating lung adenocarcinoma and squamous cell carcinoma-a distinction with important therapeutic implications. ...Although the most frequently recommended squamous marker p63 is extremely sensitive, it suffers from low specificity due to its reactivity in a substantial proportion of lung adenocarcinomas and other tumor types, particularly lymphomas. p40 is a relatively unknown antibody that recognizes ΔNp63-a p63 isoform suggested to be highly specific for squamous/basal cells. Here we compared the standard p63 antibody (4A4) and p40 in a series of 470 tumors from the archives of Memorial Sloan-Kettering Cancer Center and The Johns Hopkins Hospital, which included lung squamous cell carcinomas (n=81), adenocarcinomas (n=237), and large cell lymphomas (n=152). The p63 was positive in 100% of squamous cell carcinomas, 31% of adenocarcinomas, and 54% of large cell lymphomas (sensitivity 100%, specificity 60%). In contrast, although p40 was also positive in 100% of squamous cell carcinomas, only 3% of adenocarcinomas, and none of large cell lymphomas had p40 labeling (sensitivity 100%, specificity 98%). The mean percentage of p63 versus p40-immunoreactive cells in squamous cell carcinomas was equivalent (97 vs 96%, respectively, P=0.73). Rare adenocarcinomas with p40 labeling had reactivity in no more than 5% of tumor cells, whereas the mean (range) of p63-positive cells in adenocarcinomas and lymphomas was 26% (1-90%) and 48% (2-100%), respectively. In summary, p40 is equivalent to p63 in sensitivity for squamous cell carcinoma, but it is markedly superior to p63 in specificity, which eliminates a potential pitfall of misinterpreting a p63-positive adenocarcinoma or unsuspected lymphoma as squamous cell carcinoma. These findings strongly support the routine use of p40 in place of p63 for the diagnosis of pulmonary squamous cell carcinoma.
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Despite recent advances, the myeloproliferative neoplasms (MPNs) are attended by considerable morbidity and mortality. Janus kinase (Jak) ...inhibitors such as ruxolitinib manage symptoms but do not substantially change the natural history of the disease. In this report, we show the effects of IMG‐7289, an irreversible inhibitor of the epigenetically active lysine‐specific demethylase 1 (LSD1) in mouse models of MPN. Once‐daily treatment with IMG‐7289 normalized or improved blood cell counts, reduced spleen volumes, restored normal splenic architecture, and reduced bone marrow fibrosis. Most importantly, LSD1 inhibition lowered mutant allele burden and improved survival. IMG‐7289 selectively inhibited proliferation and induced apoptosis of JAK2V617F cells by concomitantly increasing expression and methylation of p53, and, independently, the pro‐apoptotic factor PUMA and by decreasing the levels of its antiapoptotic antagonist BCLXL. These data provide a molecular understanding of the disease‐modifying activity of the LSD1 inhibitor IMG‐7289 that is currently undergoing clinical evaluation in patients with high‐risk myelofibrosis. Moreover, low doses of IMG‐7289 and ruxolitinib synergize in normalizing the MPN phenotype in mice, offering a rationale for investigating combination therapy.
MicroRNAs (miRNAs) are increasingly implicated in the regulation of metastasis. Despite their potential as targets for anti-metastatic therapy, miRNAs have only been silenced in normal tissues of ...rodents and nonhuman primates. Therefore, the development of effective approaches for sequence-specific inhibition of miRNAs in tumors remains a scientific and clinical challenge. Here we show that systemic treatment of tumor-bearing mice with miR-10b antagomirs-a class of chemically modified anti-miRNA oligonucleotide-suppresses breast cancer metastasis. Both in vitro and in vivo, silencing of miR-10b with antagomirs significantly decreases miR-10b levels and increases the levels of a functionally important miR-10b target, Hoxd10. Administration of miR-10b antagomirs to mice bearing highly metastatic cells does not reduce primary mammary tumor growth but markedly suppresses formation of lung metastases in a sequence-specific manner. The miR-10b antagomir, which is well tolerated by normal animals, appears to be a promising candidate for the development of new anti-metastasis agents.
MicroRNAs (miRNAs) are increasingly implicated in regulating the malignant progression of cancer. Here we show that miR-9, which is upregulated in breast cancer cells, directly targets CDH1, the ...E-cadherin-encoding messenger RNA, leading to increased cell motility and invasiveness. miR-9-mediated E-cadherin downregulation results in the activation of beta-catenin signalling, which contributes to upregulated expression of the gene encoding vascular endothelial growth factor (VEGF); this leads, in turn, to increased tumour angiogenesis. Overexpression of miR-9 in otherwise non-metastatic breast tumour cells enables these cells to form pulmonary micrometastases in mice. Conversely, inhibiting miR-9 by using a 'miRNA sponge' in highly malignant cells inhibits metastasis formation. Expression of miR-9 is activated by MYC and MYCN, both of which directly bind to the mir-9-3 locus. Significantly, in human cancers, miR-9 levels correlate with MYCN amplification, tumour grade and metastatic status. These findings uncover a regulatory and signalling pathway involving a metastasis-promoting miRNA that is predicted to directly target expression of the key metastasis-suppressing protein E-cadherin.
Activation of tumor suppressors for the treatment of human cancer has been a long sought, yet elusive, strategy. PTEN is a critical tumor suppressive phosphatase that is active in its dimer ...configuration at the plasma membrane. Polyubiquitination by the ubiquitin E3 ligase WWP1 (WW domain-containing ubiquitin E3 ligase 1) suppressed the dimerization, membrane recruitment, and function of PTEN. Either genetic ablation or pharmacological inhibition of WWP1 triggered PTEN reactivation and unleashed tumor suppressive activity.
appears to be a direct MYC (MYC proto-oncogene) target gene and was critical for MYC-driven tumorigenesis. We identified indole-3-carbinol, a compound found in cruciferous vegetables, as a natural and potent WWP1 inhibitor. Thus, our findings unravel a potential therapeutic strategy for cancer prevention and treatment through PTEN reactivation.
Nuclear exclusion of the PTEN (phosphatase and tensin homologue deleted in chromosome 10) tumour suppressor has been associated with cancer progression. However, the mechanisms leading to this ...aberrant PTEN localization in human cancers are currently unknown. We have previously reported that ubiquitinylation of PTEN at specific lysine residues regulates its nuclear-cytoplasmic partitioning. Here we show that functional promyelocytic leukaemia protein (PML) nuclear bodies co-ordinate PTEN localization by opposing the action of a previously unknown PTEN-deubiquitinylating enzyme, herpesvirus-associated ubiquitin-specific protease (HAUSP, also known as USP7), and that the integrity of this molecular framework is required for PTEN to be able to enter the nucleus. We find that PTEN is aberrantly localized in acute promyelocytic leukaemia, in which PML function is disrupted by the PML-RAR fusion oncoprotein. Remarkably, treatment with drugs that trigger PML-RAR degradation, such as all-trans retinoic acid or arsenic trioxide, restore nuclear PTEN. We demonstrate that PML opposes the activity of HAUSP towards PTEN through a mechanism involving the adaptor protein DAXX (death domain-associated protein). In support of this paradigm, we show that HAUSP is overexpressed in human prostate cancer and is associated with PTEN nuclear exclusion. Thus, our results delineate a previously unknown PML-DAXX-HAUSP molecular network controlling PTEN deubiquitinylation and trafficking, which is perturbed by oncogenic cues in human cancer, in turn defining a new deubiquitinylation-dependent model for PTEN subcellular compartmentalization.
MicroRNAs are frequently deregulated in cancer. Here we show that miR-22 is upregulated in myelodysplastic syndrome (MDS) and leukemia and its aberrant expression correlates with poor survival. To ...explore its role in hematopoietic stem cell function and malignancy, we generated transgenic mice conditionally expressing miR-22 in the hematopoietic compartment. These mice displayed reduced levels of global 5-hydroxymethylcytosine (5-hmC) and increased hematopoietic stem cell self-renewal accompanied by defective differentiation. Conversely, miR-22 inhibition blocked proliferation in both mouse and human leukemic cells. Over time, miR-22 transgenic mice developed MDS and hematological malignancies. We also identify TET2 as a key target of miR-22 in this context. Ectopic expression of TET2 suppressed the miR-22-induced phenotypes. Downregulation of TET2 protein also correlated with poor clinical outcomes and miR-22 overexpression in MDS patients. Our results therefore identify miR-22 as a potent proto-oncogene and suggest that aberrations in the miR-22/TET2 regulatory network are common in hematopoietic malignancies.
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•miR-22-TET2 regulatory network controls hematopoietic stem cell biology•miR-22 triggers myelodysplastic syndrome and hematological malignancies•Levels of miR-22 and TET2 are reliable prognostic factors in MDS patients
The microRNA miR-22 participates in the initiation of leukemia by targeting TET2 and high expression correlates with poor clinical outcomes, making it an attractive therapeutic target.
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