Toll-like receptor 3 regulates cord blood-derived endothelial cell function in vitro and in vivo.

Circulating endothelial progenitor cells (cEPC) are capable of homing to neovascularisation sites, in which they proliferate and differentiate into endothelial cells. Transplantation of cEPC-derived cells, in particular those isolated from umbilical cord blood (UCB), has emerged as a promising approach in the treatment of cardio-vascular diseases. After in vivo transplantation, these cells may be exposed to local or systemic inflammation or pathogens, of which they are a common target.

Localization of the NRAS:BCL-2 complex determines anti-apoptotic features associated with progressive disease in myelodysplastic syndromes.

We have previously demonstrated that two prognostic features of myelodysplastic syndromes (MDS) and acute myelogenous leukemia (AML), mutant NRAS and over-expressing BCL-2, cooperate physically and functionally in vivo. Screening of MDS patient bone marrow (BM) identified NRAS:BCL-2 co-localization in 64% cases, correlating with percentage BM blasts, apoptotic features and disease status (p<0.0001).

Tracking the extramedullary PML-RARα-positive cell reservoirs in a preclinical model: biomarker of long-term drug efficacy.

Using an acute promyelocytic leukemia (APL) preclinical model, we show that oncogene-specific PCR (Polymerase Chain Reaction)-based assays allow to evaluate the efficacy of immunotherapy combining all-trans retinoic acid (ATRA) and a DNA-based vaccine targeting the promyelocytic leukemia-retinoic acid receptor alpha (PML-RARα) oncogene. Kaplan-Meier survival analysis according to the peripheral blood PML-RARα normalized copy number (NCN) clearly shows that ATRA + DNA-treated mice with an NCN lower than 10 (43%) formed the group with a highly significant (p < 0.0001) survival advantage.

Bexarotene via CBP/p300 induces suppression of NF-κB-dependent cell growth and invasion in thyroid cancer.

Purpose: Retinoic acid (RA) treatment has been used for redifferentiation of metastatic thyroid cancer with loss of radioiodine uptake. The aim of this study was to improve the understanding of RA resistance and investigate the role of bexarotene in thyroid cancer cells.

Experimental Design: A model of thyroid cancer cell lines with differential response to RA was used to evaluate the biological effects of retinoid and rexinoid and to correlate this with RA receptor levels.

Epigenetic patterns of the retinoic acid receptor beta2 promoter in retinoic acid-resistant thyroid cancer cells.

Treatment with retinoic acid (RA) is effective to restore radioactive iodine uptake in metastases of a small fraction of thyroid cancer patients. In order to find predictive markers of response, we took advantage of two thyroid cancer cell lines, FTC133 and FTC238, with low RA-receptor (RAR)beta expression but differing in their response to RA. We report that in both cell lines, RA signalling pathways are functional, as transactivation of an exogenous RARbeta2 promoter is effective in the presence of pharmacological concentrations of all-trans RA, and enhanced in RA-resistant FTC238 cells after ectopical expression of RARbeta, suggesting a defective endogenous RARbeta2 promoter in these cells.

Apoptosis induction by retinoids in eosinophilic leukemia cells: implication of retinoic acid receptor-alpha signaling in all-trans-retinoic acid hypersensitivity.

Hypereosinophilic syndrome (HES) has recently been recognized as a clonal leukemic lesion, which is due to a specific oncogenic event that generates hyperactive platelet-derived growth factor receptor-alpha-derived tyrosine kinase fusion proteins. In the present work, the effect of retinoids on the leukemic hypereosinophilia-derived EoL-1 cell line and on primary HES-derived cells has been investigated. We show that all-trans-retinoic acid (ATRA) inhibits eosinophil colony formation of HES-derived bone marrow cells and is a powerful inducer of apoptosis of the EoL-1 cell line.

Cooperative action of 1alpha,25-dihydroxyvitamin D3 and retinoic acid in NB4 acute promyelocytic leukemia cell differentiation is transcriptionally controlled.

All-trans-retinoic acid (RA) and 1alpha,25-dihydroxyvitamin D3 (1,25D3) are involved in the control of hematopoiesis and have been suggested to play a role in cellular differentiation and are as such potent inducers of differentiation of myeloid leukemia cells. In this study, we show that, in promyelocytic NB4 cells, addition of 1,25D3 enhances terminal granulocytic RA-dependent differentiation concomitant with the enhanced activation of the RA transcriptional activity through an RARbeta promoter. By EMSA and ChIP assays, we further demonstrate that, while both VDR and RAR are bound to the RARbeta promoter in NB4 cells, addition of 1,25D3 increases VDR binding to this promoter, while that of RA induces the release of VDR and increases the binding of RAR.

1 alpha,25-dihydroxyvitamin D3 transrepresses retinoic acid transcriptional activity via vitamin D receptor in myeloid cells.

Granulocytes and monocytes originate from a common committed progenitor cell. Commitment to either granulocytic or monocytic lineage is triggered by specific extracellular signals involving cytokines or nuclear receptor ligands (all-trans-retinoic acid (RA) and 1 alpha,25-dihydroxyvitamin D(3)). Here we show that the stimulatory effect of 1 alpha,25-dihydroxyvitamin D(3) on the production of monocytic colonies (CFU-M) is accompanied by a repression of granulocytic colony (CFU-G) production.

Cyclin D3 is a cofactor of retinoic acid receptors, modulating their activity in the presence of cellular retinoic acid-binding protein II.

Ligand-induced transcription activation of retinoic acid (RA) target genes by nuclear receptors (retinoic acid (RAR) and retinoid X (RXR) receptors) depends on the recruitment of coactivators. We have previously demonstrated that the small 15-kDa cellular RA-binding protein II (CRABPII) is a coactivator present in the RA-dependent nuclear complex. As identifying cell-specific partners of CRABPII might help to understand the novel control of RA signaling, we performed a yeast two-hybrid screen of a hematopoietic HL-60 cDNA library using human CRABPII as bait and have subsequently identified human cyclin D3 as a partner of CRABPII.

Functional G-CSF pathways in t(8;21) leukemic cells allow for differentiation induction and degradation of AML1-ETO.

Introduction: Efficacy of differentiating agents requires that their specific cellular targets are still expressed and functional in the leukemic cells. One hypothesis to target sensitive cells is to select leukemic clones which harbor disrupted transcription factors. CBFalpha and CBFbeta are core-binding proteins which have been identified as transcription regulators of hematopoietic genes and shown to be altered in numerous leukemias.

The novel co-activator CRABPII binds to RARalpha and RXRalpha via two nuclear receptor interacting domains and does not require the AF-2 'core'.

We identify the RARalpha, RXRalpha and CRABPII domains required for the physical interaction of these proteins. On RARalpha and RXRalpha, the sequences correspond to the DEF and DE domains, respectively, but the interaction with CRABPII does not require the AF-2AD 'core'. On CRABPII, two interacting domains are identified (NRID1 and NRID2), one of which contains the only enhancement transactivation domain of CRABPII.

In vitro all-trans retinoic acid sensitivity of acute promyelocytic leukemia blasts: a novel indicator of poor patient outcome.

Acute promyelocytic leukemia (APL) blasts possess a unique sensitivity to the differentiating effects of all-trans retinoic acid (ATRA). Multicenter trials confirm that the combination of differentiation and cytotoxic therapy prolongs survival in APL patients. However relapses still occur, and exquisite adaptation of therapy to prognostic factors is essential to aim at a possible cure of the disease.

All trans retinoic acid abrogates spontaneous monocytic growth in juvenile chronic myelomonocytic leukaemia.

Introduction: All trans retinoic acid, the active metabolite of vitamin A, exerts profound effects on cell differentiation. On normal myeloid progenitors, retinoids switch the differentiation program of granulo-macrophagic progenitors towards the granulocytic lineage and consequently reduce CFU-M colony formation. Bone marrow and peripheral blood mononuclear cells from children with Juvenile Chronic Myelomonocytic Leukaemia show typical spontaneous monocytic growth.

Quantitation of minimal residual disease in acute promyelocytic leukemia patients with t(15;17) translocation using real-time RT-PCR.

We took advantage of a recently developed system allowing performance of real-time quantitation of polymerase chain reaction to develop a quantitative method of measurement of PML-RARalpha transcripts which are hallmarks of acute promyelocytic leukemia (APL) with t(15;17) translocation. Indeed, although quantitation of minimal residual disease has proved to be useful in predicting clinical outcome in other leukemias such as chronic myeloid leukemia or acute lymphoblastic leukemia, no quantitative data have been provided in the case of APL. We present here a method for quantitation of the most frequent subtypes of t(15;17) transcripts (namely bcr1 and bcr3).

Physical and functional interactions between cellular retinoic acid binding protein II and the retinoic acid-dependent nuclear complex.

Two sorts of proteins bind to, and mediate the developmental and homeostatic effects of, retinoic acid (RA): the RAR and RXR nuclear receptors, which act as ligand-dependent transcriptional regulators, and the cellular RA binding proteins (CRABPI and CRABPII). CRABPs are generally known to be implicated in the synthesis, degradation, and control of steady-state levels of RA, yet previous and recent data have indicated that they could play a role in the control of gene expression. Here we show for the first time that, both in vitro and in vivo, CRABPII is associated with RARalpha and RXRalpha in a ligand-independent manner in mammalian cells (HL-60, NB-4, and MCF-7).

Ligation of the CD44 adhesion molecule reverses blockage of differentiation in human acute myeloid leukemia.

Blockage in myeloid differentiation characterizes acute myeloid leukemia (AML); the stage of the blockage defines distinct AML subtypes (AML1/2 to AML5). Differentiation therapy in AML has recently raised interest because the survival of AML3 patients has been greatly improved using the differentiating agent retinoic acid. However, this molecule is ineffective in other AML subtypes.

Distinct sensitivity of neuroblastoma cells for retinoid receptor agonists: evidence for functional receptor heterodimers.

Retinoic acid (RA) plays a major role in embryogenesis of the nervous system and has been reported to induce differentiation in neuroblastoma cell lines. To identify RA signaling pathways involved in such differentiation processes, two RA-sensitive neuroblastoma cell lines (LA-N-5 and SH-SY5Y) were extensively studied. Northern blot experiments determined that of the three RAR mRNAs, only RARalpha was significantly expressed, with respectively weak or undetectable levels of RARgamma and RARbeta.

All-trans retinoic acid rapidly decreases cathepsin G synthesis and mRNA expression in acute promyelocytic leukemia.

The cells from patients with acute promyelocytic leukemia (AML M3) undergo terminal differentiation when treated with all-trans retinoic acid (ATRA). We have analyzed the expression of the mRNA for cathepsin G, a promyelocyte stage-specific transcript, in the leukemia and in retinoic acid responsive cell lines. We showed that the transcript is perpetually synthesized in patients' cells and that it rapidly disappears when the cells are treated with ATRA.

In vitro treatment with retinoids or the topoisomerase inhibitor, VP-16, evidences different functional apoptotic pathways in acute promyelocytic leukemic cells.

Understanding the mechanisms inherent to malignant cell eradication is a major determinant for cancer therapy. Recent data have demonstrated that apoptosis may be one of the mechanisms through which both cytotoxic and differentiating drugs may eliminate malignant cells. Treatment of acute promyelocytic leukemia (APL) by all-trans retinoic acid (ATRA) is the first model of differentiation therapy allowing achievement of more than 90% complete remission (CR).

Differential uptake of all-trans retinoic acid by acute promyelocytic leukemic cells: evidence for its role in retinoic acid efficacy.

All-trans retinoic acid (ATRA) has been demonstrated to be an efficient alternative to chemotherapy in the treatment of acute promyelocytic leukemia (APL or AML3). Complete remission is obtained by inducing granulocytic differentiation of the leukemic cells. To date, the exact mechanism through which ATRA exerts its differentiating effect is not known.

Induction of high-affinity GM-CSF receptors during all-trans retinoic acid treatment of acute promyelocytic leukemia.

Differentiation of normal myeloid cells is accompanied by the increase of high-affinity GM-CSF receptors necessary for progenitor proliferation/differentiation and mature neutrophil function. All-trans retinoic acid (ATRA) induces terminal differentiation of acute promyelocytic leukemia cells (AML3 subtype). We report in this study that AML3 cells, like other AML subtypes, harbor high-affinity GM-CSF R (n = 138.

Modulation of IL-8, IL-1 beta, and G-CSF secretion by all-trans retinoic acid in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a homogeneous subgroup of acute myeloid leukemias (AML) characterized by the presence of the t(15;17) translocation and the resulting PML/RAR alpha fusion proteins. To date APL is the only AML which is sufficiently sensitive to all-trans retinoic acid (ATRA) differentiating effect. We have recently reported that APL express and secrete hematopoietic growth factors (HGF) such as IL-1 beta, TNF alpha, and IL-6.

In vitro all-trans retinoic acid (ATRA) sensitivity and cellular retinoic acid binding protein (CRABP) levels in relapse leukemic cells after remission induction by ATRA in acute promyelocytic leukemia.

The current treatment of acute promyelocytic leukemia (APL, also called AML3 subtype) is focused on differentiating agents such as the vitamin A derivative all-trans retinoic acid (ATRA). This agent is a novel and very promising therapy for this disease characterized cytogenetically by a translocation t(15;17)(q21;q22) involving the alpha retinoic acid receptor on chromosome 17 and the PML gene on chromosome 15. Clinical trials have demonstrated that ATRA followed by or combined with conventional chemotherapy may be more beneficial than chemotherapy for inducing complete remission.

Hematopoietic growth factor expression and ATRA sensitivity in acute promyelocytic blast cells.

Acute promyelocytic leukemia (APL) is a homogeneous subgroup of acute myeloid leukemias (AMLs) characterized by the presence of the t(15,17) translocation and the resulting promyelocytic myeloid leukemia/retinoic acid receptor alpha (PML/RAR alpha) fusion proteins. To date APL is the only AML that is sufficiently sensitive to all-trans retinoic acid's (ATRA) differentiating effect. In vivo ATRA alone achieves complete remission in most APL patients.