ABSTRACT: Acute promyelocytic leukemia (APL) is a treatment success story. From a highly deadly disease it was turned into a highly curable disease by the introduction of differentiation-induction therapy with all-trans retinoic acid (ATRA) in the 1990's. During the last quarter of century, ATRA and other retinoids were used for the treatment and prevention of other cancers and even other diseases. The results were less spectacular, but nevertheless important. Progress has been made toward understanding the mechanism of action of retinoids in different physiological and pathological contexts. For some diseases, specific genetic backgrounds were found to confer responsiveness to retinoid therapy. Therapies that include retinoids and other modalities are very diverse and used both for combined targeting of multiple pathways and for diminishing toxicity.
Project description:Retinoids are a family of signaling molecules derived from vitamin A with well established roles in cellular differentiation. Physiologically active retinoids mediate transcriptional effects on cells through interactions with retinoic acid (RARs) and retinoid-X (RXR) receptors. Chromosomal translocations involving the RAR? gene, which lead to impaired retinoid signaling, are implicated in acute promyelocytic leukemia (APL). All-trans-retinoic acid (ATRA), alone and in combination with arsenic trioxide (ATO), restores differentiation in APL cells and promotes degradation of the abnormal oncogenic fusion protein through several proteolytic mechanisms. RAR? fusion-protein elimination is emerging as critical to obtaining sustained remission and long-term cure in APL. Autophagy is a degradative cellular pathway involved in protein turnover. Both ATRA and ATO also induce autophagy in APL cells. Enhancing autophagy may therefore be of therapeutic benefit in resistant APL and could broaden the application of differentiation therapy to other cancers. Here we discuss retinoid signaling in hematopoiesis, leukemogenesis, and APL treatment. We highlight autophagy as a potential important regulator in anti-leukemic strategies.
Project description:The acute promyelocytic leukemia (APL) subtype of acute myeloid leukemia (AML) is characterized by chromosomal translocations that result in fusion proteins, including the promyelocytic leukemia-retinoic acid receptor, alpha fusion protein (PML-RAR?). All-trans retinoic acid (atRA) treatment is the standard drug treatment for APL yielding cure rates > 80% by activating transcription and proteasomal degradation of retinoic acid receptor, alpha (RAR?). Whereas combination therapy with As2O3 has increased survival further, patients that experience relapse and are refractory to atRA and/or As2O3 is a clinically significant problem. BCL-2 family proteins regulate apoptosis and over-expression of anti-apoptotic B-cell leukemia/lymphoma 2 (BCL-2) family proteins has been associated with chemotherapeutic resistance in APL including impairment of the ability of atRA to induce growth arrest and differentiation. Here we investigated the novel BH3 domain mimetic, JY-1-106, which antagonizes the anti-apoptotic BCL-2 family members B-cell lymphoma-extra large (BCL-xL) and myeloid cell leukemia-1 (MCL-1) alone and in combination with retinoids including atRA, AM580 (RAR? agonist), and SR11253 (RAR? antagonist). JY-1-106 reduced cell viability in HL-60 cells alone and in combination with retinoids. The combination of JY-1-106 and SR11253 had the greatest impact on cell viability by stimulating apoptosis. These studies indicate that dual BCL-xL/MCL-1 inhibitors and retinoids could work cooperatively in leukemia treatment.
Project description:BACKGROUND:Acute promyelocytic leukemia (APL) is a highly curable disease when treated with all-trans retinoid acid (ATRA) and arsenic trioxide (ATO). The combination of ATO and ATRA has become the standard therapeutic protocol for induction therapy in non-high-risk APL. An oral arsenic realgar-indigo naturalis formula (RIF) has also showed high efficacy and it has a more convenient route of administration than the standard intravenous regimen. Unlike in previous trials, the arsenical agent was used simultaneously with ATRA during post-remission therapy in this trial. METHODS:This study was designed as a multicenter, randomized controlled trial. The trial has a non-inferiority design with superiority being explored if non-inferiority is identified. All patients receive ATRA-ATO during the induction therapy. After achieving hematologic complete remission (HCR), patients were randomly assigned (1:1) to receive treatment with ATRA-RIF (experimental group) or ATRA-ATO (control group) as the consolidation therapy. During the consolidation therapy, the two groups receive ATRA plus RIF or intravenous ATO 2?weeks on and 2 to ~?4?weeks off until molecular complete remission (MCR), then ATRA and oral RIF 2?weeks on and 2 to ~?4?weeks off giving a total of six courses. DISCUSSION:This trial aims to compare the efficacy of ATRA-ATO versus ATRA-RIF in non-high-risk patients with APL, to demonstrate that oral RIF application reduces the total hospitalization days and medical costs. The simple schedule was studied in this trial. TRIAL REGISTRATION:ClinicalTrials.gov, NCT02899169. Registered on 14 September 2016.
Project description:The success of all-trans retinoic acid (ATRA) in differentiation therapy for patients with acute promyelocytic leukemia (APL) highly encourages researches to apply this therapy to other types of acute myeloid leukemia (AML). However, AML, with the exception of APL, fails to respond to differentiation therapy. Therefore, research strategies to further sensitize cells to retinoids and to extend the range of AMLs that respond to retinoids beyond APLs are urgently needed. In this study, we showed that TAK165, a HER2 inhibitor, exhibited a strong synergy with ATRA to promote AML cell differentiation. We observed that TAK165 sensitized the AML cells to ATRA-induced cell growth inhibition, G0/G1 phase arrest, CD11b expression, mature morphologic changes, NBT reduction and myeloid regulator expression. Unexpectedly, HER2 pathway might not be essential for TAK165-enhanced differentiation when combined with ATRA, while the enhanced differentiation was dependent on the activation of the RAR?/STAT1 axis. Furthermore, the MEK/ERK cascade regulated the activation of STAT1. Taken together, our study is the first to evaluate the synergy of TAK165 and ATRA in AML cell differentiation and to assess new opportunities for the combination of TAK165 and ATRA as a promising approach for future differentiation therapy.
Project description:Despite All-trans retinoic acid (ATRA) has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological cancer, there remains a clinical challenge that many high-risk APL patients who fail to achieve a complete molecular remission or relapse and become resistant to ATRA. Herein, we report that 5-(4-methoxyphenethyl)-[1, 3] dioxolo [4, 5-j] phenanthridin-6(5H)-one (ZYH005) exhibits specific anticancer effects on APL and ATRA-resistant APL in vitro and vivo, while shows negligible cytotoxic effect on non-cancerous cell lines and peripheral blood mononuclear cells from healthy donors. Using single-molecule magnetic tweezers and molecule docking, we demonstrate that ZYH005 is a DNA intercalator. Further mechanistic studies show that ZYH005 triggers DNA damage, and caspase-dependent degradation of the PML-RARa fusion protein. As a result, APL and ATRA-resistant APL cells underwent apoptosis upon ZYH005 treatment and this apoptosis-inducing effect is even stronger than that of arsenic trioxide and anticancer agents including 5-fluorouracil, cisplatin and doxorubicin. Moreover, ZYH005 represses leukemia development in vivo and prolongs the survival of both APL and ATRA-resistant APL mice. To our knowledge, ZYH005 is the first synthetic phenanthridinone derivative, which functions as a DNA intercalator and can serve as a potential candidate drug for APL, particularly for ATRA-resistant APL.
Project description:The treatment of acute promyelocytic leukaemia (APL) has evolved dramatically over the past several decades, making the disease a highly curable form of acute leukaemia. The discoveries of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) were landmark events, leading to historic revolutions in the treatment of APL. One major change was from chemotherapy-based to chemotherapy-free treatment regimens, and the combination of ATRA plus ATO without chemotherapy has been recommended as the standard therapy for non-high-risk APL. The other major change was from the intravenous administration of medicine in the hospital to a largely home-based oral approach, which is a more cost-effective and convenient treatment model. In this review, we focus on the evolution of therapeutic approaches for APL, as well as the challenges that remain with the current approaches.
Project description:There is emerging evidence that, beyond their cholesterol-lowering properties, statins exhibit important antileukemic effects in vitro and in vivo, but the precise mechanisms by which they generate such responses remain to be determined. We have previously shown that statins promote differentiation of acute promyelocytic leukemia cells and enhance generation of all-trans retinoic acid (ATRA)-dependent antileukemic responses. We now provide evidence that statin-dependent leukemic cell differentiation requires engagement and activation of the c-Jun NH2-terminal kinase kinase pathway. In addition, in experiments, to define the molecular targets and mediators of statin-induced differentiation, we found a remarkable effect of statins on ATRA-dependent gene transcription, evidenced by the selective induction of over 400 genes by the combination of atorvastatin and ATRA. Altogether, our studies identify novel statin molecular targets linked to differentiation, establish that statins modulate ATRA-dependent transcription, and suggest that combined use of statins with retinoids may provide a novel approach to enhance antileukemic responses in acute promyelocytic leukemia and possibly other leukemias.
Project description:All-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO) administration leads to granulocytic maturation and/or apoptosis of acute promyelocytic leukemia (APL) cells mainly by targeting promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR?). Yet, ~10-15% of APL patients are not cured by ATRA- and ATO-based therapies, and a potential failure of ATRA and ATO in completely reversing PML/RAR?-driven oncogenic alterations has not been comprehensively examined. Here we characterized the in vivo primary responses of dysregulated genes in APL cells treated with ATRA and ATO using a GFP-labeled APL model. Although induced granulocytic differentiation of APL cells was evident after ATRA or ATO administration, the expression of the majority of dysregulated genes in the c-Kit+ APL progenitors was not consistently corrected. Irf8, whose expression increased along with spontaneous differentiation of the APL progenitors in vivo, represented such a PML/RAR?-dysregulated gene that was refractory to ATRA/ATO signaling. Interestingly, Irf8 induction, but not its knockdown, decreased APL leukemogenic potential through driving monocytic maturation. Thus, we reveal that certain PML/RAR?-dysregulated genes that are refractory to ATRA/ATO signaling are potentially crucial regulators of the immature status and leukemogenic potential of APL cells, which can be exploited for the development of new therapeutic strategies for ATRA/ATO-resistant APL cases.
Project description:Acute promyelocytic leukemia (APL) is often associated with activating FLT3 signaling mutations. These are highly related to hyperleukocytosis, a major adverse risk factor with chemotherapy-based regimens. APL is a model for oncogene-targeted therapies: all-trans retinoic acid (ATRA) and arsenic both target and degrade its ProMyelocytic Leukemia/Retinoic Acid Receptor ? (PML/RARA) driver. The combined ATRA/arsenic regimen now cures virtually all patients with standard-risk APL. Although FLT3-internal tandem duplication (ITD) was an adverse risk factor for historical ATRA/chemotherapy regimens, the molecular bases for this effect remain unknown. Using mouse APL models, we unexpectedly demonstrate that FLT3-ITD severely blunts ATRA response. Remarkably, although the transcriptional output of initial ATRA response is unaffected, ATRA-induced PML/RARA degradation is blunted, as is PML nuclear body reformation and activation of P53 signaling. Critically, the combination of ATRA and arsenic fully rescues therapeutic response in FLT3-ITD APLs, restoring PML/RARA degradation, PML nuclear body reformation, P53 activation, and APL eradication. Moreover, arsenic targeting of normal PML also contributes to APL response in vivo. These unexpected results explain the less favorable outcome of FLT3-ITD APLs with ATRA-based regimens, and stress the key role of PML nuclear bodies in APL eradication by the ATRA/arsenic combination.
Project description:In acute promyelocytic leukemia (APL), the translocation t(15;17) induces a block at the promyelocytic stage of differentiation in an all-trans-retinoic acid (ATRA)-responsive manner. Here we report that upon treatment with ATRA, t(15;17) cells (NB4) reveal a very rapid increase in protein level and binding activity of C/EBPbeta, a C/EBP family member, which was not observed in an ATRA-resistant NB4 cell line. We further provide evidence that ATRA mediates a direct increase of C/EBPbeta, only in PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha)-expressing cells. In addition, transactivation experiments indicate that the PML-RARA fusion protein, but not PML-RARA mutants defective in transactivation, strongly transactivates the C/EBPbeta promoter. These results suggest that PML-RARA mediates ATRA-induced C/EBPbeta expression. Finally, we demonstrate the importance of C/EBPbeta in granulocytic differentiation. We show that not only does C/EBPbeta induce granulocytic differentiation of non-APL myeloid cell lines independent of addition of ATRA or other cytokines, but also that C/EBPbeta induction is required during ATRA-induced differentiation of APL cells. Taken together, C/EBPbeta is an ATRA-dependent PML-RARA target gene involved in ATRA-induced differentiation of APL cells.