Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disease (MPD) initiated by expression of the p210-BCR-ABL fusion protein. We demonstrate in a murine model of p210-BCR-ABL-induced ...MPD that gene targeting of
Rac1 and
Rac2 significantly delays or abrogates disease development. Attenuation of the disease phenotype is associated with severely diminished p210-BCR-ABL-induced downstream signaling in primary hematopoietic cells. We utilize NSC23766, a small molecule antagonist of Rac activation, to validate biochemically and functionally Rac as a molecular target in both a relevant animal model and in primary human CML cells in vitro and in a xenograft model in vivo, including in Imatinib-resistant p210-BCR-ABL disease. These data demonstrate that Rac is an additional therapeutic target in p210-BCR-ABL-mediated MPD.
Altered mRNA translation is one of the effects exerted by the BCR/ABL oncoprotein in the blast crisis phase of chronic myelogenous leukemia (CML). Here, we report that in BCR/ABL+ cell lines and in ...patient-derived CML blast crisis mononuclear and CD34+ cells, p210BCR/ABL increases expression and activity of the transcriptional-inducer and translational-regulator heterogeneous nuclear ribonucleoprotein K (hnRNP K or HNRPK) in a dose- and kinase-dependent manner through the activation of the MAPKERK1/2 pathway. Furthermore, HNRPK down-regulation and interference with HNRPK translation-but not transcription-regulatory activity impairs cytokine-independent proliferation, clonogenic potential, and in vivo leukemogenic activity of BCR/ABL-expressing myeloid 32Dcl3 and/or primary CD34+ CML-BC patient cells. Mechanistically, we demonstrate that decreased internal ribosome entry site (IRES)-dependent Myc mRNA translation accounts for the phenotypic changes induced by inhibition of the BCR/ABL-ERK-dependent HNRPK translation-regulatory function. Accordingly, MYC protein but not mRNA levels are increased in the CD34+ fraction of patients with CML in accelerated and blastic phase but not in chronic phase CML patients and in the CD34+ fraction of marrow cells from healthy donors. Thus, BCR/ABL-dependent enhancement of HNRPK translation-regulation is important for BCR/ABL leukemogenesis and, perhaps, it might contribute to blast crisis transformation. (Blood. 2006;107:2507-2516)
Hypermethylation of 5'-cytosine-guanosine islands of tumor suppressor genes resulting in their silencing has been proposed to be a hallmark of various tumors. Modulation of DNA methylation with DNA ...methylation inhibitors has been shown to result in cancer cell differentiation or apoptosis and represents a novel strategy for chemotherapy. Currently, effective DNA methylation inhibitors are mainly limited to decitabine and 5-azacytidine, which still show unfavorable toxicity profiles in the clinical setting. Thus, discovery and development of novel hypomethylating agents, with a more favorable toxicity profile, is essential to broaden the spectrum of epigenetic therapy. Parthenolide, the principal bioactive sesquiterpene lactone of feverfew, has been shown to alkylate Cys(38) of p65 to inhibit nuclear factor-kappaB activation and exhibit anti-tumor activity in human malignancies. In this article, we report that parthenolide 1) inhibits DNA methyltransferase 1 (DNMT1) with an IC(50) of 3.5 microM, possibly through alkylation of the proximal thiolate of Cys(1226) of the catalytic domain by its gamma-methylene lactone, and 2) down-regulates DNMT1 expression possibly associated with its SubG(1) cell-cycle arrest or the interruption of transcriptional factor Sp1 binding to the promoter of DNMT1. These dual functions of parthenolide result in the observed in vitro and in vivo global DNA hypomethylation. Furthermore, parthenolide has been shown to reactivate tumor suppressor HIN-1 gene in vitro possibly associated with its promoter hypomethylation. Hence, our study established parthenolide as an effective DNA methylation inhibitor, representing a novel prototype for DNMT1 inhibitor discovery and development from natural structural-diversified sesquiterpene lactones.
Sulforaphane is a natural product that is constantly under biological investigation for its unique biological properties. This naturally occurring isothiocyanate (ITC) and its analogs are the main ...components of cruciferous vegetables, such as cauliflower, watercress, broccoli, cabbage, Brussels sprouts, widely used as chemopreventive agents. Due to their interesting biological profiles, natural ITCs have been exploited as starting point to develop new synthetic analogs. The present mini-review briefly highlights the most important biological actions of selected new synthetic ITCs focusing on their structure-activity relationships and related synthetic strategies.
The protein phosphatase 2A (PP2A) tumor suppressor is inactivated in different leukemias through the activity of its endogenous inhibitors (e.g., SET), which are aberrantly regulated by oncogenic ...tyrosine kinases. Like other effective and nontoxic PP2A-activating drugs (PAD), OP449 inhibits SET and impairs leukemogenesis. This further supports the immediate use of PADs in patients with leukemia.
In the originally published version of this Article, the positions of the final two authors in the author list were inadvertently inverted during the production process. This error has now been ...corrected in both the PDF and HTML versions of the Article.
Aqueous humor (AH), the clear fluid in front of the eye, maintains the pressure and vitality of ocular tissues. This fluid is accessible via the clear cornea which enables use of AH as a liquid ...biopsy source of biomarkers for intraocular disease. Extracellular vesicles are detectable in the AH and small extracellular vesicles (sEVs) are present in the AH from adults. However, EVs in AH from pediatric eyes in vivo have never previously been explored. We know very little about the heterogeneity of AH EV populations in ocular disease. Twenty‐seven processing‐free AH samples from 19 patients across four different pediatric ocular diseases were subjected to Nanoparticle Tracking Analysis (NTA) and Single Particle‐Interferometric Reflectance Imaging Sensor (SP‐IRIS) analysis. NTA demonstrated the concentration of AH EV/EPs is 3.11 × 109–1.38 × 1010 particles/ml; the majority sized 76.8–103 nm. SP‐IRIS revealed distinct patterns of tetraspanin expression of AH sEVs. An enriched mono‐CD63+ sEV subpopulation identified in AH indicates this is a potential AH‐specific biomarker. In the setting of retinoblastoma there was a more heterogeneous population of sEVs which normalized with treatment. This suggests a potential clinical application of direct measurement of sEV subpopulations in AH samples to monitor successful tumor response to therapy.
In t(8;21) acute myeloid leukemia (AML), the AML1/ETO fusion protein promotes leukemogenesis by recruiting class I histone deacetylase (HDAC)-containing repressor complex to the promoter of AML1 ...target genes. Valproic acid (VPA), a commonly used antiseizure and mood stabilizer drug, has been shown to cause growth arrest and induce differentiation of malignant cells via HDAC inhibition. VPA causes selective proteasomal degradation of HDAC2 but not other class I HDACs (i.e., HDAC 1, 3, and 8). Therefore, we raised the question of whether this drug can effectively target the leukemogenic activity of the AML1/ETO fusion protein that also recruits HDAC1, a key regulator of normal and aberrant histone acetylation. We report here that VPA treatment disrupts the AML1/ETO-HDAC1 physical interaction, stimulates the global dissociation of AML1/ETO-HDAC1 complex from the promoter of AML1/ETO target genes, and induces relocation of both AML1/ETO and HDAC1 protein from nuclear to perinuclear region. Furthermore, we show that mechanistically these effects associate with a significant inhibition of HDAC activity, histone H3 and H4 hyperacetylation, and recruitment of RNA polymerase II, leading to transcriptional reactivation of target genes (i.e., IL-3) otherwise silenced by AML1/ETO fusion protein. Ultimately, these pharmacological effects resulted in significant antileukemic activity mediated by partial cell differentiation and caspase-dependent apoptosis. Taken together, these data support the notion that VPA might effectively target AML1/ETO-driven leukemogenesis through disruption of aberrant HDAC1 function and that VPA should be integrated in novel therapeutic approaches for AML1/ETO-positive AML.
Several RNA binding proteins (RBPs) have been implicated in the progression of chronic myelogenous leukemia (CML) from the indolent chronic phase to the aggressively fatal blast crisis. In the latter ...phase, expression and function of specific RBPs are aberrantly regulated at transcriptional or posttranslational levels by the constitutive kinase activity of the BCR/ABL oncoprotein. As a result, altered expression/function of RBPs leads to increased resistance to apoptotic stimuli, enhanced survival, growth advantage, and differentiation arrest of CD34+ progenitors from patients in CML blast crisis. Here, we identify the mRNAs bound to the hnRNP-A1, hnRNP-E2, hnRNP-K, and La/SSB RBPs in BCR/ABLtransformed myeloid cells. Interestingly, we found that the mRNA encoding the transcription factor E2F3 associates to hnRNP-A1 through a conserved binding site located in the E2F3 3′ untranslated region (UTR). E2F3 levels were up-regulated in CML-BCCD34+ in a BCR/ABL kinase– and hnRNP-A1 shuttling–dependent manner. Moreover, by using shRNA-mediated E2F3 knock-down and BCR/ABL-transduced lineage-negative bone marrow cells from E2F3+/+ and E2F3−/− mice, we show that E2F3 expression is important for BCR/ABL clonogenic activity and in vivo leukemogenic potential. Thus, the complexity of the mRNA/RBP network, together with the discovery of E2F3 as an hnRNP-A1–regulated factor, outlines the relevant role played by RBPs in posttranscriptional regulation of CML development and progression.
Genetic Events Other than BCR-ABL1 Neviani, Paolo
Current hematologic malignancy reports,
03/2014, Letnik:
9, Številka:
1
Journal Article
Recenzirano
The BCR-ABL1 oncoprotein is the cause of chronic myeloid leukemia and occurs as a consequence of the translocation t(9;22), a well-defined genetic event that results in the formation of the ...Philadelphia chromosome. While this genomic aberration is recognized to be the main culprit of the chronic phase of chronic myeloid leukemia, the natural clonal evolution of this myeloproliferative neoplasm involves the accumulation of secondary alterations through genomic instability. Thus, efforts to dissect the frequency and nature of the genomic events at diagnosis and at later stages are producing valuable insights into understanding the mechanisms of blastic transformation and development of resistance in chronic myeloid leukemia. The identification of alternative BCR-ABL1-dependent and BCR-ABL1-independent targets that sustain the survival of leukemic blasts and/or leukemia-initiating cells will facilitate the development of novel viable therapeutic options for patients who become resistant or intolerant to the currently available therapeutic options based on tyrosine kinase inhibitors.
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