Chibby 1: a new component of β-catenin-signaling in chronic myeloid leukemia

Chibby 1 (CBY1) is a small and evolutionarily conserved protein, which act as β-catenin antagonist. CBY1 is encoded by C22orf2 (22q13.1) Its antagonistic function on β-catenin involves the direct interaction with:

The C-terminal activation domain of β-catenin, which hinders β-catenin binding with Tcf/Lef transcription factors hence repressing β-catenin transcriptional activation.

14-3-3 scaffolding proteins (σ or ξ), which drive CBY1 nuclear export into a stable tripartite complex with β-catenin.

The relative proximity of C22orf2 gene encoding for CBY1 to the BCR breakpoint on chromosome 22q11, whose translocation and rearrangement with the c-ABL is the causative event of chronic myeloid leukemia (CML), suggested that gene haploinsufficiency may play a role in the disease pathogenesis and progression. We found CBY1 down-modulation associated with the BCR-ABL1, promoted by transcriptional mechanisms (promoter hyper-methylation) and post-transcriptional events, addressing the protein towards proteasome-dependent degradation through SUMOylation. CBY1 reduced expression in clonal progenitors and, more importantly, in leukemic stem cells (LSC), is contingent upon the tyrosine kinase (TK) activity of BCR-ABL1 fusion protein. Accordingly, its induction by Imatinib (IM) and second generation TK inhibitors contributes to β-catenin inactivation through multiple events encompassing the activation of endoplasmic reticulum (ER) stress-associated unfolded protein response (UPR) and autophagy, eventually leading to apoptotic death. These findings support the advantage of combined regimens including drugs targeting DNA epigenetics and/or proteasome to eradicate the BCR-ABL1+ hematopoiesis.

FOXM1 Transcription Factor: A New Component of Chronic Myeloid Leukemia Stem Cell Proliferation Advantage

FOXM1 transcription factor is a central component of tumor initiation, growth, and progression due to its multiple effects on cell cycle, DNA repair, angiogenesis and invasion, chromatin, protein anabolism, and cell adhesion. Moreover, FOXM1 interacts with β-catenin promoting its nuclear import and transcriptional activation. Here, we show that FOXM1 is involved in the advantage of chronic myeloid leukemia hematopoiesis over the normal counterpart. FOXM1 hyper-activation associated with BCR-ABL1 results from phosphorylation by the fusion protein kinase-dependent activation of Polo-like kinase 1. FOXM1 phosphorylation lets its binding with β-catenin and β-catenin transcriptional activation, a key event for persistence of the leukemic stem cell compartment under tyrosine kinase inhibitor therapy. Polo-like kinase 1 inhibitor BI6727, already advanced for clinical use, breaks β-catenin interaction with FOXM1, hence hampering FOXM1 phosphorylation, β-catenin binding, nuclear import, and downstream signaling. In conclusion, our results support Polo-like kinase 1/FOXM1 axis as a complementary target to eradicate leukemic early progenitor/stem cell compartment in chronic myeloid leukemia. J. Cell. Biochem. 118: 3968-3975, 2017. © 2017 Wiley Periodicals, Inc.

14-3-3 Binding and Sumoylation Concur to the Down-Modulation of β-catenin Antagonist chibby 1 in Chronic Myeloid Leukemia

The down-modulation of the β-catenin antagonist Chibby 1 (CBY1) associated with the BCR-ABL1 fusion gene of chronic myeloid leukemia (CML) contributes to the aberrant activation of β-catenin, particularly in leukemic stem cells (LSC) resistant to tyrosine kinase (TK) inhibitors. It is, at least partly, driven by transcriptional events and gene promoter hyper-methylation. Here we demonstrate that it also arises from reduced protein stability upon binding to 14-3-3σ adapter protein. CBY1/14-3-3σ interaction in BCR-ABL1+ cells is mediated by the fusion protein TK and AKT phosphorylation of CBY1 at critical serine 20, and encompasses the 14-3-3σ binding modes I and II involved in the binding with client proteins. Moreover, it is impaired by c-Jun N-terminal kinase (JNK) phosphorylation of 14-3-3σ at serine 186, which promotes dissociation of client proteins. The ubiquitin proteasome system UPS participates in reducing stability of CBY1 bound with 14-3-3σ through enhanced SUMOylation. Our results open new routes towards the research on molecular pathways promoting the proliferative advantage of leukemic hematopoiesis over the normal counterpart.

BCR-ABL1-associated reduction of beta catenin antagonist Chibby1 in chronic myeloid leukemia

Beta Catenin signaling is critical for the self-renewal of leukemic stem cells in chronic myeloid leukemia. It is driven by multiple events, enhancing beta catenin stability and promoting its transcriptional co-activating function. We investigated the impact of BCR-ABL1 on Chibby1, a beta catenin antagonist involved in cell differentiation and transformation. Relative proximity of the Chibby1 encoding gene (C22orf2) on chromosome 22q12 to the BCR breakpoint (22q11) lets assume its involvement in beta catenin activation in chronic myeloid leukemia as a consequence of deletions of distal BCR sequences encompassing one C22orf2 allele. Forty patients with chronic myeloid leukemia in chronic phase were analyzed for C22orf2 relocation and Chibby1 expression. Fluorescent in situ hybridization analyses established that the entire C22orf2 follows BCR regardless of chromosomes involved in the translocation. In differentiated hematopoietic progenitors (bone marrow mononuclear cell fractions) of 30/40 patients, the expression of Chibby1 protein was reduced below 50% of the reference value (peripheral blood mononuclear cell fractions of healthy persons). In such cell context, Chibby1 protein reduction is not dependent on C22orf2 transcriptional downmodulation; however, it is strictly dependent upon BCR-ABL1 expression because it was not observed at the moment of major molecular response under tyrosine kinase inhibitor therapy. Moreover, it was not correlated with the disease prognosis or response to therapy. Most importantly, a remarkable Chibby1 reduction was apparent in a putative BCR-ABL1+ leukemic stem cell compartment identified by a CD34+ phenotype compared to more differentiated hematopoietic progenitors. In CD34+ cells, Chibby1 reduction arises from transcriptional events and is driven by C22orf2 promoter hypermethylation. These results advance low Chibby1 expression associated with BCR-ABL1 as a component of beta catenin signaling in leukemic stem cells.

Chibby drives β catenin cytoplasmic accumulation leading to activation of the unfolded protein response in BCR-ABL1+ cells

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by the constitutive tyrosine kinase (TK) activity of the BCR-ABL fusion protein. However, the phenotype of leukemic stem cells (LSC) is sustained by β catenin rather than by the BCR-ABL TK. β catenin activity in CML is contingent upon its stabilization proceeding from the BCR-ABL-induced phosphorylation at critical residues for interaction with the Adenomatous polyposis coli (APC)/Axin/glycogen synthase kinase 3 (GSK3) destruction complex or GSK3 inactivating mutations. Here we studied the impact of β catenin antagonist Chibby (CBY) on β catenin signaling in BCR-ABL1+ cells. CBY is a small conserved protein which interacts with β catenin and impairs β catenin-mediated transcriptional activation through two distinct molecular mechanisms: 1) competition with T cell factor (TCF) or lymphoid enhancer factor (LEF) for β catenin binding; and 2) nuclear export of β catenin via interaction with 14-3-3. We found that its enforced expression in K562 cell line promoted β catenin cytoplasmic translocation resulting in inhibition of target gene transcription. Moreover, cytoplasmic accumulation of β catenin activated the endoplasmic reticulum (ER) stress-associated pathway known as unfolded protein response (UPR). CBY-driven cytoplasmic accumulation of β catenin is also a component of BCR-ABL1+ cell response to the TK inhibitor Imatinib (IM). It evoked the UPR activation leading to the induction of BCL2-interacting mediator of cell death (BIM) by UPR sensors. BIM, in turn, contributed to the execution phase of apoptosis in the activation of ER resident caspase 12 and mobilization of Ca(2+) stores.

Abstract 4051: Loss of nuclear beta catenin, following chibby enforced expression, activates endoplasmic reticulum stress in cells expressing the BCR-ABL1 fusion gene of chronic myeloid leukemia

CML is a myeloproliferative disease originated from a pluripotent hematopoietic cell, the bona fide leukemic stem cell (LSC), where reciprocal translocation t(9;22) generates the BCR-ABL rearranged gene. This single genetic lesion drives the clonal expansion of leukemic hematopoiesis through the constitutively activated tyrosine kinase (TK) of its protein. The majority of CML patients undergoes complete hematologic remission in response to TK inhibitor Imatinib (IM). However, BCR-ABL+ LSC are neither dependent on BCR-ABL TK for proliferation and survival nor killed by IM and second generation inhibitors, providing a putative source of drug-resistance.

β catenin is a central component of BCR-ABL+ LSC self-renewal. Moreover, it may have a role in the stemness recovery of committed granulocyte/macrophage progenitors at the outcome of blast crisis. Consequently, beta catenin subcellular distribution is a central component of signaling activity and its nuclear-cytoplasmatic shuttling is tightly regulated by multiple carrier protein, including 14-3-3.

Chibby (CBY) is a protein that directly interacts with beta catenin and competes with TCF/LEF factors for beta catenin binding, repressing its transcriptional activity. Moreover, Chibby cooperates with 14-3-3 to regulate beta catenin subcellular distribution and signaling activity. We have recently found a significant CBY reduction associated with BCR-ABL TK with a consequent increment of active beta catenin. This findings suggested a CBY putative role in the proliferative advantage of CML hematopoiesis and addressed our further investigation towards the CBY impact on proliferation and survival of BCR-ABL+ cells. To this purpose we stably transduced the BCR-ABL+ K562 cell line with a construct containing C22orf2.

The cytoplasmatic accumulation of beta catenin triggered the endoplasmic reticulum (ER)-associated stress pathway known as the unfolded protein response (UPR). The UPR is primarily a survival response which activates a series of complementary adaptive mechanisms to resolve the dysregulation of protein folding. However, under prolonged and irreversible ER stress conditions UPR triggers apoptosis through caspase activation and modulation of ER Ca2+ signaling. The ER stress elicited by beta catenin cytoplasmatic accumulation in consequence of CBY overexpression doomed K562 cells to apoptotic death induced by a significant increase of CHOP, which amplifies the pro-apoptotic signal by transcriptional activation of BIM and the release of PKR-like eIF2 kinase (PERK) and inositol-requiring enzyme (IRE1), all mediators of ER stress.

Our results suggest that enforced CBY expression significantly reduced K562 proliferation through events encompassing the beta catenin prominent relocation to the cytoplasm and its transcriptional silencing.

Citation Format: Manuela Mancini, Elisa Leo, Enrica Borsi, Fausto Castagnetti, Michelangelo Fiorentino, Ilaria Iacobucci, Michele Cavo, Maria Alessandra Santucci, Giovanni Martinelli. Loss of nuclear beta catenin, following chibby enforced expression, activates endoplasmic reticulum stress in cells expressing the BCR-ABL1 fusion gene of chronic myeloid leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4051. doi:10.1158/1538-7445.AM2013-4051

Gadd45a transcriptional induction elicited by the Aurora kinase inhibitor MK-0457 in Bcr-Abl-expressing cells is driven by Oct-1 transcription factor

The advantage of Aurora kinase (AK) inhibitors in chronic myeloid leukemia (CML) therapy mostly arises from "off-target" effects on tyrosine kinase (TK) activity of wild type (wt) or mutated Bcr-Abl proteins which drive the disease resistance to imatinib (IM). We proved that the AK inhibitor MK-0457 induces the growth arrest DNA damage-inducible (Gadd) 45a through recruitment of octamer-binding (Oct)-1 transcription factor at a critical promoter region for gene transcription and covalent modifications of histone H3 (lysine 14 acetylation, lysine 9 de-methylation). Such epigenetic chromatin modifications may depict a general mechanism promoting the re-activation of tumor suppressor genes silenced by Bcr-Abl.

A new nonpeptidic inhibitor of 14-3-3 induces apoptotic cell death in chronic myeloid leukemia sensitive or resistant to imatinib

Resistance of chronic myeloid leukemia (CML) to tyrosine kinase inhibitor imatinib mesylate (IM) is most often due to point mutations in the Bcr-Abl fusion gene. T315I mutation (resulting in substitution of Ile for a Thr residue at the "gatekeeper" position 315) raises particular concern, because it also provides resistance to second-generation kinase inhibitors already approved for clinical use (nilotinib and dasatinib). Much effort is therefore focused on alternative molecular-based strategies. Previous studies proved that binding to 14-3-3 scaffolding proteins leads to cytoplasmic compartmentalization and suppression of proapoptotic and antiproliferative signals associated with Bcr-Abl protein kinase, hence contributing to leukemic clone expansion. Here we investigated the effect of 14-3-3 inhibition disruption on hematopoietic cells expressing the IM-sensitive wild type Bcr-Abl and the IM-resistant T315I mutation. Using a virtual screening protocol and docking simulations, we identified a nonpeptidic inhibitor of 14-3-3, named BV02, that exhibits a remarkable cytotoxicity against both cell types. c-Abl release from 14-3-3σ, promoting its relocation to nuclear compartment (where it triggers transcription of p73-dependent proapoptotic genes) and to mitochondrial membranes (where it induces the loss of mitochondrial transmembrane potential) combined with c-Abl enhanced association with caspase 9 (a critical step of sequential caspase activation further contributing to c-Abl pro-apoptotic function) has a prominent role in the effect of BV02 on Bcr-Abl-expressing cells. In conclusion, BV02 may be considered as a treatment option for CML and, in particular, for more advanced phases of the disease that developed IM resistance as a consequence of Bcr-Abl point mutations.

Identification of the first non-peptidic small molecule inhibitor of the c-Abl/14-3-3 protein-protein interactions able to drive sensitive and Imatinib-resistant leukemia cells to apoptosis

An in silico structure-based ligand design approach resulted in the identification of the first non-peptidic small molecule able to inhibit protein-protein interactions between 14-3-3 and c-Abl. This compound shows an anti-proliferative effect on human leukemia cells either sensitive or resistant to Imatinib, in consequence of the T315I mutation. It also mediates c-Abl release from 14-3-3 in a way similar to that found in response to Imatinib treatment.

mTOR inhibitor RAD001 (Everolimus) enhances the effects of imatinib in chronic myeloid leukemia by raising the nuclear expression of c-ABL protein

Constitutive tyrosine kinase (TK) activity of p210 BCR-ABL fusion protein of chronic myeloid leukemia (CML) usurps physiological functions of normal p145 c-ABL protein. Accordingly, its inhibition by imatinib mesylate (IM) lets p145 c-ABL translocate into the nuclear compartment, which drives cell growth arrest and apoptotic death. Here we show that IM and the mammalian target of rapamycin (mTOR) inhibitor RAD001 (Everolimus) have additive effects on BCR-ABL-expressing cells. Those effects are at least partly conditional upon the enhanced nuclear accumulation of p145 c-ABL through events encompassing post-translational modifications of p145 c-ABL (Thr(735) phosphorylation) precluding its nuclear export and of 14-3-3 sigma (Ser(186) phosphorylation by c-Jun N-terminal kinase [JNK]) promoting p145 c-ABL nuclear re-import.

14-3-3 ligand prevents nuclear import of c-ABL protein in chronic myeloid leukemia

Here we demonstrated that the 'loss of function' of not-rearranged c-ABL in chronic myeloid leukemia (CML) is promoted by its cytoplasmic compartmentalization bound to 14-3-3 sigma scaffolding protein. In particular, constitutive tyrosine kinase (TK) activity of p210 BCR-ABL blocks c-Jun N-terminal kinase (JNK) phosphorylation leading to 14-3-3 sigma phosphorylation at a critical residue (Ser(186)) for c-ABL binding in response to DNA damage. Moreover, it is associated with 14-3-3 sigma over-expression arising from epigenetic mechanisms (promoter hyper-acetylation). Accordingly, p210 BCR-ABL TK inhibition by the TK inhibitor Imatinib mesylate (IM) evokes multiple events, including JNK phosphorylation at Thr(183), p38 mitogen-activated protein kinase (MAPK) phosphorylation at Thr(180), c-ABL de-phosphorylation at Ser residues involved in 14-3-3 binding and reduction of 14-3-3 sigma expression, that let c-ABL release from 14-3-3 sigma and nuclear import, and address BCR-ABL-expressing cells towards apoptotic death. Informational spectrum method (ISM), a virtual spectroscopy method for analysis of protein interactions based on their structure, and mathematical filtering in cross spectrum (CS) analysis identified 14-3-3 sigma/c-ABL binding sites. Further investigation on CS profiles of c-ABL- and p210 BCR-ABL-containing complexes revealed the mechanism likely involved 14-3-3 precluded phosphorylation in CML cells.

Genomic imbalances associated with secondary acute leukemias in Hodgkin lymphoma

Secondary tumors and leukemias are major complications in Hodgkin lymphoma (HL). They likely arise from clonal selection of cells that have accumulated genomic lesions induced by chemo- and radiotherapy and may be further promoted by the loss of DNA repair and/or other pathways ensuring the fidelity of replicated DNA. To distinguish genomic imbalances associated with the development of acute myeloid leukemia (AML) in HL we used an array-based comparative genomic hybridization (aCGH) strategy on whole lymph node biopsies of HL patient. Genomic imbalances (amplifications and deletions) associated with AML outcome in 3 classic HL patients, at clinical diagnosis they exhibited a discrete individual variability. Three amplifications and 5 deletions were shared by all 3 patients. They involved AFM137XA11, a 9p11.2 pericentric region; FGFR1, the FGF receptor most frequently translocated in AML; PPARBP, a co-activator of nuclear receptors RARalpha, RXR and TRbeta1; AFM217YD10, a 17q25 telomeric region; FGR, an SRC2 kinase involved in cytokine production by NK and CD4+ NKT cells; GATA3, a Th2-specific transcription factor; TOP1, involved in DNA recombination and repair; WT1, a transcription factor involved in CD8+ T cell response against leukaemic blasts. Immunohistochemistry confirmed aCGH results and distinguished the distribution of either amplified or deleted gene products in neoplastic Reed Sternberg (RS) cells and non-neoplastic lymph node components.

Persistent Cdk2 inactivation drives growth arrest of BCR-ABL-expressing cells in response to dual inhibitor of SRC and ABL kinases SKI606

Complementary inhibition of tyrosine and SRC kinases implement dual SRC/ABL inhibitor effects in chronic myeloid leukemia (CML). Here, we show that one such inhibitor, SKI-606, induces persistent Cdk2 inactivation leading to growth arrest of BCR-ABL-expressing cells either IM-sensitive or driven to IM-resistance by other events than gene overexpression and point mutations. Inhibition of Akt serine/threonine kinase, a phosphatidylinositol 3 kinase (PI-3k) target that integrates p210 TK signaling with membrane-associated SRC kinases, is a central component of restored expression and subcellular redistribution of Cdk2 regulatory signals (p21 and p27 and Cdc25A phosphatase) in response to SKI-606. The putative roles of growth factor (namely IL-3) autocrine loop in BCR-ABL-expressing progenitor progression towards a drug-resistant phenotype are discussed.

Modulation of apoptotic signalling by 9-hydroxystearic acid in osteosarcoma cells

9-hydroxystearic acid (9-HSA) belongs to the class of endogenous lipid peroxidation by-products that greatly diminish in tumors, causing as a consequence the loss of one of the control mechanisms on cell division. We have previously shown that 9-HSA controls cell growth and differentiation by inhibiting histone deacetylase 1 (HDAC1) activity. In this paper our attention has not only been focused on HDAC1 inhibition but also on the hyperacetylation of other substrates such as p53, that is involved in inducing cell cycle arrest and/or apoptosis, and whose activity and stability are known to be regulated by posttranslational modifications, particularly by acetylation at the C-terminus region. 9-HSA administration to U2OS, an osteosarcoma cell line p53 wt, induces a growth arrest of the cells in G2/M and apoptosis via a mitochondrial pathway. In particular hyperacetylation of p53 induced by the HDAC1 inhibitory activity of 9-HSA has been demonstrated to increase Bax synthesis both at the transcriptional and the translational level. The subsequent translocation of Bax to the mitochondria is associated to a significant increase in caspase 9 activity. Our data demonstrate that the effects of 9-HSA on U2OS correlate with posttranslational modifications of p53.

P210 Bcr-abl tyrosine kinase interaction with histone deacetylase 1 modifies histone H4 acetylation and chromatin structure of chronic myeloid leukaemia haematopoietic progenitors

The BCR-ABL fusion gene, originating from the balanced (9;22) translocation, is the molecular hallmark and the causative event of chronic myeloid leukaemia (CML). The interactions of its p210 protein constitutively activated and improperly confined to the cytoplasm with multiple regulatory signals of cell cycle progression, apoptosis and self-renewal, induce the illegitimate enlargement of clonal haematopoiesis and genetic instability that drives its progression towards the fully transformed phenotype of blast crisis. However, its effects on the basic transcription machinery and chromatin remodelling are unknown. Our study underscored histone H4 hyperacetylation associated with p210 tyrosine kinase in vitro and in vivo and its role in BCR-ABL transcription. Histone H4 hyperacetylation proceeds, at least partly, from the 'loss of function' of histone deacetylase 1 protein, a critical component of Rb-mediated transcriptional repression, in consequence of its cytoplasmatic compartmentalisation.

Tyrosine kinase inhibitor STI571 (Imatinib) cooperates with wild-type p53 on K562 cell line to enhance its proapoptotic effects

In order to ascertain whether p53 has a role in chronic myeloid leukemia hematopoietic progenitor response to the innovative tyrosine kinase inhibitor STI571 (Imatinib), we overexpressed a wild type (wt) p53 construct in the K562 cell line, generated from a human blast crisis and lacking endogenous p53. Wt p53 overexpression was associated with a significant reduction of bcr-abl expression levels resulting, at least in part, from post-transcriptional events affecting the stability of p210 bcr-abl fusion protein. Moreover, we demonstrated that p53 overexpression enhances the commitment to the apoptotic death fate of K562 following its in vitro exposure to 1 microM STI571. Multiple mechanisms are involved in p53 impact on K562 survival: Most importantly, we found that a greater reduction of bcr-abl transcription by STI571 was associated with the overexpression of wt p53. Further studies are required to elucidate the mechanisms involved in the transcriptional repression of bcr-abl by STI571 and p53 and in their synergic effects on the clonal hematopoiesis of chronic myeloid leukemia.

Chk2 drives late G1/early S phase arrest of clonal myeloid progenitors expressing the p210 BCR-ABL tyrosine kinase in response to STI571

STI571 is the most innovative drug for the cure of Chronic Myeloid Leukemia. It inhibits, in fact, the disease causative event, the p210 bcr-abl tyrosine kinase, and addresses clonal myeloid progenitors to apoptotic death. Here, we demonstrated that STI571 also induces growth arrest by activating the Chk2-Cdc25A-Cdk2 axis, a pathway complementary to p53 in the activation of G(1)/S cell cycle checkpoint. In vitro exposure to STI571 of 32D murine myeloid progenitor cell clones transducing a temperature-sensitive p210 bcr-abl construct was associated with Chk2 phosphorylation and activation, Cdc25A degradation and persistent Cdk2 inhibitory phosphorylation, preventing, in turn, cell transition to and progression throughout the S phase of cell cycle. Chk2 and Cdc25A are both components of a complex network that integrates signals involved in regulated cell cycle progression, DNA repair and cell decision between life or death. Chk2 gene mutations or decreased expression, leading to its protein loss of function on Cdc25A target, and Cdc25A overexpression have been linked to poor prognosis of human cancers. In CML, they might further enhance the proliferative advantage and genomic instability of clonal myeloid progenitors featuring a class of poor prognosis patients eventually resistant to STI571.

9-Hydroxystearic acid upregulates p21(WAF1) in HT29 cancer cells

Growing evidence supports the critical role of lipid peroxidation products in the control of cell proliferation. In previous studies we demonstrated the efficient restriction of the proliferation rate in several cell lines resulting from the in vitro treatment with endogenous lipid polar components of cell membranes. Among these, 9-hydroxystearic acid (9-HSA), a primary intermediate of lipid peroxidation, induced a significant arrest in G0/G1 in HT29 colon cancer cells. In response to 9-HSA treatment of HT29 we observed cell growth arrest and increase in p21(WAF1) expression both at the transcriptional and the translational levels. Growth of p21(WAF1)-deleted HCT116 human colon carcinoma cells was not inhibited by 9-HSA. We present evidence that p21(WAF1) is required for 9-HSA mediated growth arrest in human colon carcinoma cells.

Endoplasmic reticulum stress initiates apoptotic death induced by STI571 inhibition of p210 bcr–abl tyrosine kinase

The endoplasmic reticulum (ER) is the site where proteins destined to either secretion or different subcellular compartments assemble and the major storage of intracellular Ca(2+). The ER stress resulting from a variety of toxic insults leads to apoptosis. Here, we showed that the apoptotic death triggered by STI571, an inhibitor of the p210 bcr-abl tyrosine kinase, in murine myeloid progenitors transducing the p210 bcr-abl tyrosine kinase of Chronic Myeloid Leukemia (CML) proceeds from ER stress. The Bcl-2 dowmodulation and inactivation induced by the binding to its antagonist: Bad, the release of caspase 12 from the ER membranes in its active form and of Ca(2+) from the ER pool addressed towards ER a sensor of STI571-induced pro-apoptotic signal.

p53 loss of function enhances genomic instability and accelerates clonal evolution of murine myeloid progenitors expressing the p(210)BCR-ABL tyrosine kinase

BACKGROUND AND OBJECTIVES

The p210 bcr-abl fusion protein has a key role in the pathogenesis of chronic myeloid leukemia (CML). However, its influence on disease progression to blast crisis is marginal and mostly due to its effect of impairing the genomic stability of clonal myeloid progenitors through pathways still largely unknown.

DESIGN AND METHODS

To elucidate the role of p53 in CML progression we generated, from the 32D murine myeloid cell line, several clones co-expressing the E6 product gene of human papilloma virus (HPV) 16, which abrogates p53 function, and a temperature-sensitive bcr-abl construct encoding a fully active p210 protein only at the permissive temperature of 33 degrees C.

RESULTS

Co-expression of the two proteins resulted in a significant enlargement of the G(2)/M phase of cell cycle and in the appearance of a poly-aneuploid cell population. Furthermore, with continuous in vitro passages the p210 tyrosine kinase became dispensable for growth. Increased levels of cyclin B(1) and enhanced activity of its associated cyclin-dependent kinase (cdc2) became apparent during the clonal evolution of p210 bcr-abl-transduced 32D cell clones lacking p53.

INTERPRETATION AND CONCLUSIONS

The acceleration of clonal evolution of p210 bcr-abl-transduced 32D myeloid progenitors associated with p53 functional abrogation is consistent with oncosuppressor loss having a key role in CML progression. This would allow emergence of additional genomic aberrations which would lead to the fully transformed phenotype of blast crisis. Deregulated activity of the cyclin B1-cdc2 complex may be involved in the loss of temporal co-ordination of mitotic events and further free the barrier to genomic instability of CML clonal myeloid progenitors lacking p53.

Cell-cycle deregulation in BALB/c 3T3 cells transformed by 1,2-dibromoethane and folpet pesticides

The cell-transforming potential of 1,2-dibromoethane and folpet, two widely used agricultural pesticides that are potential sources of environmental pollution, has been previously ascribed to their promoting activity. In this study, we investigated whether BALB/c 3T3 transformation by these chemicals was associated with the deregulation of signals involved in cell-cycle progression and in cell-cycle checkpoint induction. We found that two BALB/c 3T3 cell clones transformed by in vitro medium-term (8-week) exposure to the carcinogens had a constitutive acceleration of cell transition from G(1) to S phase and an abrogation of the radiation-induced G(1)/S checkpoint. These events involved multiple signals; in particular, the inhibitors of cyclin/cyclin-dependent kinase complexes p21 and p27 were significantly down-modulated and the positive regulators of cell-cycle progression cyclin D(3) and E were up-modulated. As anticipated for cells where the G(1)/S checkpoint was abrogated, the transformed cells exhibited a significant reinforcement of the radiation-induced G(2)/M checkpoint, the only checkpoint remaining to protect genomic integrity. However, cyclin A(1) and B(1) coexpression and cyclin A(1) overexpression were found despite the G2 arrest in irradiated cells and these signals likely attenuate the G(2)/M checkpoint. These alterations to normal cell cycling may promote the emergence of both numerical and structural chromosomal abnormalities and their tolerance. Such a condition could play a key role in neoplastic transformation and be crucial in tumor progression. Furthermore, cyclin A(1) overexpression may play an autonomous role in the neoplastic transformation of BALB/c 3T3 cells, as it does in other cell types of mesenchymal origin.

Perceptions about advance directives by nurses in a community hospital

Despite the legal mandate for hospitals to comply with the Patient Self-Determination Act and recommendations by the American Nurses' Association for nurses to advocate for the participation of patients in end-of-life decisions, nurses' compliance has been less than enthusiastic. This study used an exploratory descriptive design and a 10-item self-reported questionnaire, which included both multiple-choice and open-ended questions. This study examined nurses' knowledge and comfort with the implementation of the Patient Self-Determination Act. An analysis of this research shows that two major themes emerged: a need for more education involving advance directives and a desire to have other healthcare workers involved in informing patients about advance directives.

Expression of P21(WAF1/CIP1/SID1) cyclin-dependent kinase inhibitor in hematopoietic progenitor cells

P21(Waf1/Cip1/Sid1) is a critical component of biomolecular pathways leading to the G(1) arrest evoked in response to DNA damage, growth arrest signals and differentiation commitment. It belongs to the Cip/Kip class of cyclin-dependent kinase inhibitors and is at least partly regulated by p53. P21(Waf1/Cip1/Sid1) functional inactivation possibly resulting from mutations of the gene itself or, more likely, from p53 mutations may be critical for either the cell fate following DNA-damaging insults or clonal evolution toward malignancy. In the study presented here we describe a competitive polymerase chain reaction (PCR) strategy whose sensitivity and reproducibility enable us to attain a precise quantitation of p21(Waf1/Cip1/Sid1) expression levels in hematopoietic progenitors, the cell compartment which mostly suffers from the side effects of genotoxic drugs in use for cancer cure. The strategy was set in the M07 factor-dependent hematopoietic progenitor cell line. We confirmed that its p21(waf1/cip1/sid1) constitutive expression level is very low and up-modulated by DNA-damaging agents: ionizing radiations and ultraviolet light. Gene up-modulation resulted in checkpoint activation and, in particular, in a significant G(1) arrest, required for either the repair of damaged DNA sequences or apoptotic cell death. Our competitive PCR strategy was further validated in CD34(+) purified hematopoietic progenitors from healthy donors mobilized into the peripheral blood by granulocyte colony-stimulating factor and intended for allogeneic bone marrow transplantation. The constitutive p21(WAF1/CIP1/SID1) expression levels, measured in three separate harvests, were very low and no significant differences were apparent. Our results support the use of a competitive PCR strategy as a useful tool for clinical purposes, to assess the individual biomolecular response of early hematopoietic progenitors to antiblastic drugs.

Competitive polymerase chain reaction as a method to detect the amplification of bcr-abl gene of chronic myeloid leukemia

BACKGROUND AND OBJECTIVES

The chimeric product of the bcr-abl rearranged gene is critical in the pathogenesis of chronic myeloid leukemia (CML), yet its role in the progression of the disease remains unclear. There is some evidence that increased bcr-abl expression levels, possibly due to gene amplification, precede the clonal evolution of CML hematopoietic progenitors toward a fully transformed phenotype and might be involved in their resistance to interferon-alpha or tyrosine kinase inhibitors.

DESIGN AND METHODS

To quantify the bcr-abl gene both at the genomic and at the transcriptional levels we developed a competitive polymerase chain reaction (PCR) strategy. The competitive PCR technique is based upon the co-amplification of the sample template (target) together with increasing amounts of a DNA fragment (competitor) sharing with the target the primer recognition sites, but differing in size. We constructed a competitor for the quantification of both b2a2 and b3a2 alternative splicing forms of the bcr-abl chimera and established the accuracy and reproducibility of our competitive strategy in a clone of the murine 32DG hematopoietic cell line (32D LG7), which bears a stable integration of a single copy of p210 bcr-abl fusion gene. We utilized this technique to follow, over a period of 200 days, the fusion gene copy numbers and transcription rates in several p210 bcr-abl-transduced 32D cell clones, an experimental condition mimicking the evolution of CML myeloid progenitors in vivo.

RESULTS

Our results are consistent with p210 bcr-abl overexpression but not gene amplification associated with their clonal evolution. Increased p210 bcr-abl transcription rate is associated with the abrogation of radiation-induced apoptotic cell death, suggesting a role for the chimeric gene expression level in cell life expectancy after a genotoxic insult.

INTERPRETATION AND CONCLUSIONS

We conclude that the assessment of gene amplification and expression might serve to improve prognostic classification and follow-up of CML patients.

Radiation-induced gadd45 expression correlates with clinical response to radiotherapy of cervical carcinoma

BACKGROUND

Recent work has identified a category of genes devoted to the control of genomic stability and prevention of cellular evolution. They encode components of cell cycle checkpoint, i.e., regulatory pathways committed to ordered cell cycle transition and fidelity of replicated DNA under adverse environmental conditions, such as those following exposure to genotoxic agents. Gadd45 belongs to the class II family of DNA damage-inducible (DDI) gene, and its role in DNA repair has been proved in many experimental models. The aim of our study was to correlate gadd45 radio-induction with the responsiveness to radiotherapy of cervical carcinomas, a type of cancer most commonly treated with radiotherapy alone.

METHODS

By means of a competitive polymerase chain reaction strategy, we compared in 14 patients the gene expression levels before and during external beam radiotherapy, when a dose ranging from 18 to 25 Gy was delivered to the target.

RESULTS

We found a correlation between the lack of gadd45 induction and a good clinical response to radiotherapy, in terms of both local control and disease-free survival.

CONCLUSION

Our results support the measure of the induction of gadd45, and possibly of other genes required for regulated G1-S checkpoint, as a method useful for prognostic evaluation of cervical carcinoma patients.

Procedure for the quantitation of Gadd45 expression levels in clonal hematopoietic progenitor cells by competitive polymerase chain reaction

OBJECTIVE

The growth arrest and DNA damage-inducible (gadd) genes represent a family of stress-inducible genes that are coordinately regulated at transcriptional level. Gadd45, in particular, has been linked to a p53-dependent inducible network required for regulated transition from G1 to S phase of cell cycle following genotoxic insult and growth arrest treatments and has seemingly a pivotal role in DNA repair.

DESIGN AND METHODS

Here we show that competitive polymerase chain reaction (PCR) is an adequate method to quantitate gadd45 expression levels in hematopoietic progenitor cell line 32D, whose constitutive gene expression is very low.

RESULTS

The sensitivity and reproducibility of our strategy support its usefulness for clinical purposes, to assess the DNA repair capacity of highly purified early myeloid progenitors, whose failure may be responsible for either short-term chemotherapy side effects (bone marrow hypoplasia and peripheral blood cytopenia) or long-term consequences of antiblastic drugs (leukemia and myelodysplasia).

Long-term bone marrow cultures in Diamond-Blackfan anemia reveal a defect of both granulomacrophage and erythroid progenitors

The hematopoietic defect of Diamond-Blackfan anemia (DBA) results in selective failure of erythropoiesis. Thus far, it is not known whether this defect originates from an intrinsic impediment of hematopoietic progenitors to move forward along the erythroid pathway or to the impaired capacity of the bone marrow (BM) microenvironment to support proliferation and differentiation of hematopoietic cells. Reduced longevity of long-term bone marrow cultures, the most physiologic in vitro system to study the interactions of hematopoietic progenitors and hematopoietic microenvironment, is consistent with a defect of an early hematopoietic progenitor in DBA. However, stromal adherent layers from DBA patients generated in a long-term culture system, the in vitro counterpart of BM microenvironment, did not show evidence of any morphologic, phenotypic, or functional abnormality. Our major finding was an impaired capacity of enriched CD34+ BM cell fraction from DBA patients, cultured in the presence of normal BM stromal cells, to proliferate and differentiate along the erythroid pathway. A similar impairment was observed in some DBA patients along the granulomacrophage pathway. Our result points to an intrinsic defect of a hematopoietic progenitor with bilineage potential that is earlier than previously suspected as a relevant pathogenetic mechanism of the disease. The finding of impaired granulopoiesis in some DBA patients underlines the heterogeneity of this rare disorder.

Prior treatment with alpha-interferon does not adversely affect the outcome of allogeneic BMT in chronic phase chronic myeloid leukemia

BACKGROUND AND OBJECTIVE

Controlled clinical trials have shown that Interferon-alpha (IFN-alpha) is able to control myeloid proliferation and to suppress the Ph+ clonal hemopoiesis in early chronic phase chronic myeloid leukemia (CML): a growing number of patients are treated with this agent from diagnosis. However, if a CML patient has an HLA-identical sibling, bone marrow transplant (BMT) represents the best choice of treatment. Since IFN-alpha is known to modify the immunologic response and to increase marrow fibrosis, information is needed on the outcome of patients transplanted after IFN-alpha treatment.

DESIGN AND METHODS

We analyzed retrospectively 32 Ph+ CML patients submitted to BMT in the last 6 years in Institute "Serágnoli". All the patients were in 1st chronic phase, their median age was 37 years, the donors were HLA-identical (27/32) or 1 Ag-mismatched (5/32) siblings. Big BuCy was the conditioning regimen employed for all and GVHD prophylaxis was based on CsA in 4 patients and Csa+MTX in 28 patients; all patients received homogeneous pre and post-transplant supportive care, antimicrobial and antiviral prophylaxis. These patients were divided into 2 groups according to the treatment before BMT: 16 received IFN from diagnosis to BMT (mean dose 6.9 MU/daily) for at least 6 mos (mean 23 mos, range 8-75) and 16 received chemotherapy alone (hydroxyurea [HU]).

RESULTS

Hematological recovery was comparable in the two groups: time to 0.5 x 10(9)/L PMN was 20.5 days (range 11-32) in the IFN group and 20 days (range 10-32) in the HU group; time to 50 x 10(9)/L platelets was 28 days (range 20-117) in the IFN group and 27 days (range 20-112) in the HU group. The incidence of acute GVHD was not different in the two groups for any grade of the disease; in patients who survived more than 100 days, chronic GVHD occurred in the two groups with the same frequency. Seven patients died of transplant related mortality (TRM), 4 in the IFN group and 3 in the HU group. Hematological relapse was observed in only one case in the HU group; no cytogenetic relapse occurred. Disease free survivals at 7 years are 61% and 72%, respectively; the difference is not significant.

INTERPRETATIONS AND CONCLUSIONS

Notwithstanding the low number of patients included in this study, the data reported here confirm that prior treatment with alpha-IFN does not adversely affect transplant outcome.

Peripheral blood mobilization of hematopoietic stem cells: cytokine-mediated regulation of adhesive interactions within the hematopoietic microenvironment

Peripheral blood (PB) mobilization of hematopoietic progenitors, presently regarded as an alternative source of cells intended for autologous or allogeneic bone marrow (BM) transplantation, supports a role for cytokines in the regulated adhesion of hematopoietic compartments to the BM microenvironment. Two major consequences might result from cytokine-induced rearrangements of adhesive interactions within the hematopoietic tissue, both potentially relevant for clinical purposes of PB grafts. The first one, arising from abrogated adhesion of hematopoietic stem cells to their microenvironmental 'niche', which is critical for the maintenance of cell cycle quiescence and endurability, might result in some impairment of the long-term repopulating potential of PB grafts. The second and possibly more harmful one is due to the inability of the cytokine to distinguish between normal and transformed cells, and would likely result in graft contamination by tumor cells, increasing the metastasizing potential of hematological malignancies and solid tumors.

Study of second messenger levels and of sugar catabolism enzyme activities in transformed cells resistant to ionizing radiations

We measured the level of second messengers, the activity of carbohydrate metabolism enzymes, and the resistance to ionizing radiations in normal 32D hematopoietic cells, in v-erbB transformants and in spontaneous transformants. v-erbB and spontaneous transformants were resistant to radiations as compared with their normal counterpart. The second messenger diacylglycerol was elevated in radioresistant clones. Only v-erbB transformants showed increase of the activities of enolase and glucose-6-phosphate dehydrogenase. v-erbB-transformed NIH/3T3 cells, selected as control, showed identical correlation between radioresistance, increase of diacylglycerol, and of enolase and glucose-6-phosphate dehydrogenase activity. These results indicate that increase of diacylglycerol is correlated with resistance to the killing effect of ionizing radiations and could be proposed as a marker of radioresponse.

Erythropoietin increases the radioresistance of a clonal hematopoietic progenitor cell line expressing a transgene for the erythropoietin receptor

Erythropoietin (Epo) is a serum glycoprotein growth factor required for the survival, proliferation and differentiation of committed erythroid progenitor cells. In the present study, we sought to determine whether the action of Epo via its receptor is also implicated in the repair of radiation-induced cell damage. Overexpression of the Epo receptor (Epo-R) was achieved as a result of transfection of the 32D cl 3 clonal hematopoietic cell line. These clonal lines allowed us to investigate the effects of Epo on the radiation sensitivity in vitro of a clonal murine hematopoietic progenitor cell line. Low level expression of Epo-R on many hematopoietic cell types was thus circumvented. Ligand binding of Epo resulted in increased radioresistance of 32D cl 3 subclonal lines expressing the Epo-R transgene. The D0 of 32D Epo-R cells at 1.49 Gy/min was 1.33 Gy and n was 1.39. The D0 of parental clonal cell line 32D cl 3 cells at 1.49 Gy/min was 1.36 Gy and n was 1.39. In contrast, at the low dose rate of 0.0595 Gy/min, the D0 of 32D Epo-R cells was 2.0 Gy and n was 1.24, while parental clonal line 32D cl 3 showed a D0 of 1.35 Gy and n was 1.39. The increased radioresistance was statistically significant at low dose rate (p < 0.05). Combined exposure to Epo and interleukin 3 (IL-3) increased proliferation of 32D Epo-R cells but did not induce a detectable further increase in radioresistance. Temporal dissociation between growth factor-activated tyrosine phosphorylation of intracellular substrates, and the radioprotective effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of p210 bcr/abl increases hematopoietic progenitor cell radiosensitivity

PURPOSE

The cytogenetic finding of the Ph1+ chromosome and its molecular biologic marker bcr/abl gene rearrangement in cells from patients with chronic myeloid leukemia are associated with a proliferative advantage of the Ph1+ clone in vivo. Although the transition to the acute terminal phase or blastic crisis is often associated with additional cytogenetic abnormalities, the molecular events which correlate the initial cytogenetic lesion with the terminal phase are poorly understood. Defective cellular DNA repair capacity is often associated with chromosomal instability, increased mutation frequency, and biologic alterations.

METHODS AND MATERIALS

We, therefore, tested whether the protein product of the bcr/abl translocation (p210) could alter DNA repair after gamma-irradiation of murine cell lines expressing the bcr/abl cDNA.

RESULTS

The 32D cl 3 parent, 32D cl 3 pYN (containing the control vector plasmid) and each of two sources of 32D cl 3 cells expressing p210 bcr/abl cDNA (32D-PC1 cell line and 32D-LG7 subclone) showed a D0 of 1.62, 1.57, 1.16, and 1.27 Gy, respectively. Thus, expression of the p210 bcr/abl product induced a significant (p < 0.05) increase in radiosensitivity at the clinically relevant radiation therapy dose-rate (1.16 Gy/min). The increased radiosensitivity of p210 bcr/abl expressing cells persisted if cells were held before plating in a density-inhibited state for 8 hr after gamma-irradiation, indicating little effect on the repair of potentially lethal gamma-irradiation damage. The IL-3 dependent parent 32D cl 3 cells demonstrated programmed cell death in the absence of growth factor or following gamma-irradiation to 200 cGy. Expression of bcr/abl cDNA in the 32D-PC1 and 32D-LG7 sub clones abrogated IL-3 requirement of these cell lines and inhibited gamma-irradiation induced programmed cell death.

CONCLUSION

These data suggest a role for bcr/abl p210 in amplifying gamma-irradiation DNA damage or broadly inhibiting DNA repair, conditions that may stimulate further cytogenetic alterations in hematopoietic cells.

M-07e cell bioassay detects stromal cell production of granulocyte-macrophage colony stimulating factor and stem cell factor in normal and in Diamond-Blackfan anemia bone marrow

Ten healthy donors and four patients with Diamond-Blackfan anemia (DBA) have been investigated for granulocyte-macrophage colony stimulating factor (GM-CSF) and stem cell factor (SCF) production by bone marrow-enriched fibroblasts (BMEF) in a highly sensitive biological assay on growth factor-dependent M-07e cells. M-07e cells detected active soluble kit-ligand from normal bone marrow fibroblasts as well as from DBA BMEF which produce constitutively significant amounts of SCF. Interleukin 1 beta (IL-1 beta) induced a significant increase of soluble SCF from both normal and DBA BMEF. GM-CSF was undetectable in unstimulated cultures, while its production by bone marrow microenvironmental cells was documented for both normal and DBA patients after IL-1 beta stimulation in vitro.

Education literature for Hispanic patients

A patient tells his home health nurse through an interpreter that he does not understand the treatment consent form. The form is printed in English. The patient understands only Spanish. A young woman learned her child's home antibiotic therapy through a demonstration given in Spanish. She now wants to review the procedure to program the pump that controls the intravenous dose. The manual is printed in English. The young mother understands only Spanish. These examples reflect the growing communication problems facing home care workers who work in Hispanic communities.