The SIRT1/TP53 axis is activated upon B-cell receptor triggering via miR-132 up-regulation in chronic lymphocytic leukemia cells

A molecular circuit linking the BCR to the NAD biosynthetic enzyme NAMPT is an actionable target in Richter syndrome

ABSTRACT

This works defines, to the best of our knowledge, for the first time a molecular circuit connecting nicotinamide mononucleoside phosphoribosyl transferase (NAMPT) activity to the B-cell receptor (BCR) pathway. Using 4 distinct xenograft models derived from patients with Richter syndrome (RS-PDX), we show that BCR cross-linking results in transcriptional activation of the nicotinamide adenine dinucleotide (NAD) biosynthetic enzyme NAMPT, with increased protein expression, in turn, positively affecting global cellular NAD levels and sirtuins activity. NAMPT blockade, by using the novel OT-82 inhibitor in combination with either BTK or PI3K inhibitors (BTKi or PI3Ki), induces rapid and potent apoptotic responses in all 4 models, independently of their mutational profile and the expression of the other NAD biosynthetic enzymes, including nicotinate phosphoribosyltransferase. The connecting link in the circuit is represented by AKT that is both tyrosine- and serine-phosphorylated by PI3K and deacetylated by sirtuin 1 and 2 to obtain full kinase activation. Acetylation (ie, inhibition) of AKT after OT-82 administration was shown by 2-dimensional gel electrophoresis and immunoprecipitation. Consistently, pharmacological inhibition or silencing of sirtuin 1 and 2 impairs AKT activation and induces apoptosis of RS cells in combination with PI3Ki or BTKi. Lastly, treatment of RS-PDX mice with the combination of PI3Ki and OT-82 results in significant inhibition of tumor growth, with evidence of in vivo activation of apoptosis. Collectively, these data highlight a novel application for NAMPT inhibitors in combination with BTKi or PI3Ki in aggressive lymphomas.

MiRNAs and circRNAs for the Diagnosis of Anthracycline-Induced Cardiotoxicity in Breast Cancer Patients: A Narrative Review

Breast cancer (BC) is the most frequent type of female cancer with increasing incidence in recent years. Doxorubicin (DOX) is an important backbone chemotherapy in BC, responsible for cardiotoxicity (CTX) in about 9% of treated women within the first year. Biomarkers of early CTX diagnosis are essential to avoid complicated DOX-related cardiac diseases. Traditional serum biomarkers are either poorly sensitive with transient elevation, and even absent if investigated outside their diagnostic window, or arise only in late-stage CTX. Emerging biomarkers such as non-coding RNA (ncRNA) have been recently investigated in DOX-related CTX. In our review, we revised the role of microRNAs, the most studied type of ncRNA, both in animal and human models, highlighting the interesting but often contrasting results. Moreover, we reviewed a novel class of ncRNA, circular RNA (circRNA), focusing on their modulatory mechanisms also involving microRNAs. MicroRNA and circRNA are players in a wide homeostatic balance with their perturbation representing a possible compensation for DOX damage. Further studies are required to assess the modalities of early detection of their variation in BC patients suffering from heart disease induced by DOX treatment.

B Cell Receptor signaling and genetic lesions in TP53 and CDKN2A/CDKN2B cooperate in Richter Transformation

B cell receptor (BCR) signals play a critical role in the pathogenesis of chronic lymphocytic leukemia (CLL), but their role in regulating CLL cell proliferation has still not been firmly established. Unlike normal B cells, CLL cells do not proliferate in vitro upon engagement of the BCR, suggesting that CLL cell proliferation is regulated by other signals from the microenvironment, such as those provided by Toll-like receptors or T cells. Here, we report that BCR engagement of human and murine CLL cells induces several positive regulators of the cell cycle, but simultaneously induces the negative regulators CDKN1A, CDKN2A and CDKN2B, which block cell cycle progression. We further show that introduction of genetic lesions that downregulate these cell cycle inhibitors, such as inactivating lesions in CDKN2A, CDKN2B and the CDKN1A regulator TP53, leads to more aggressive disease in a murine in vivo CLL model and spontaneous proliferation in vitro that is BCR-dependent but independent of costimulatory signals. Importantly, inactivating lesions in CDKN2A, CDKN2B and TP53 frequently co-occur in Richter syndrome, and BCR stimulation of human Richter syndrome cells with such lesions is sufficient to induce proliferation. We also show that tumor cells with combined TP53 and CDKN2A/2B abnormalities remain sensitive to BCR inhibitor treatment and are synergistically sensitive to the combination of a BCR and CDK4/6 inhibitor both in vitro and in vivo. These data provide evidence that BCR signals are directly involved in driving CLL cell proliferation and reveal a novel mechanism of Richter transformation.

MicroRNA‑132 promotes oxidative stress‑induced pyroptosis by targeting sirtuin 1 in myocardial ischaemia‑reperfusion injury

The present study aimed to investigate the roles of miR‑132 in myocardial ischaemia/reperfusion (I/R) injury and the underlying mechanisms. The myocardial I/R model was established using C57BL/J6 mice. Haematoxylin and eosin staining was performed to observe the injury of myocardial tissues. Commercial kits were used to measure the levels of serum myocardial enzymes and inflammatory factors. The in vitro I/R model was established by the hypoxia/reoxygenation method using H9C2 cells. A dual luciferase reporter assay was used to confirm the binding of miR‑132 and sirtuin 1 (SIRT1). Cell pyroptosis was determined using flow cytometry. Reverse transcription‑quantitative PCR was performed to determine the expression of miR‑132, SIRT1 and inflammatory factors. The levels of peroxisome proliferator‑activated receptor gamma coactivator (PGC)‑1α/nuclear factor erythroid‑2‑related factor 2 (Nrf2) signalling, oxidative stress and pyroptosis‑related proteins were detected by western blotting. Apparent histologic injury and elevated levels of serum myocardial enzymes and inflammatory factors were observed in the myocardial I/R model. miR‑132 was significantly upregulated and SIRT1 was markedly downregulated in I/R myocardial tissues. miR‑132 directly targeted SIRT1 and negatively regulated the expression of SIRT1. PGC‑1α, Nrf2, endothelial nitric oxide synthase and superoxide dismutase levels were significantly decreased, while inducible nitric oxide synthase and malondialdehyde levels were significantly increased by I/R induction. The pyroptosis‑related proteins NLRP3, caspase‑1 and interleukin (IL)‑1β were also significantly elevated by I/R induction. Inhibition of miR‑132 activated PGC‑1α/Nrf2 signalling and inhibited oxidative stress and the expression of the pyroptosis‑related proteins NLRP3, caspase‑1 and IL‑1β, which were all reversed by inhibiting SIRT1 with EX527. The findings of the present study indicated that inhibition of miR‑132 may ameliorate myocardial I/R injury by inhibiting oxidative stress and pyroptosis through activation of PGC‑1α/Nrf2 signalling by targeting SIRT1.

Role of SIRT1 in hematologic malignancies

Sirtuin 1 (SIRT1) is a protein deacetylase, which regulates various physiological activities by deacetylating different protein substrates. An increasing number of studies have revealed critical roles of SIRT1 in different aspects of cancers including metabolism, proliferation, genomic instability, and chemotherapy resistance. Depending on the protein targets in a certain oncogenic context, SIRT1 may play a unique role in each individual blood cancer subtype. Our previous work showed that activation of SIRT1 in primitive leukemia cells of acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML) promotes disease maintenance. On the other hand, an SIRT1 agonist was shown to disrupt maintenance of myelodysplastic syndrome (MDS) stem cells and holds promise as a potential therapeutic approach. Herein, we present a concise summary of the different functions of SIRT1 in hematologic malignancies.

Dual Deletion of the Sirtuins SIRT2 and SIRT3 Impacts on Metabolism and Inflammatory Responses of Macrophages and Protects From Endotoxemia

Sirtuin 2 (SIRT2) and SIRT3 are cytoplasmic and mitochondrial NAD-dependent deacetylases. SIRT2 and SIRT3 target proteins involved in metabolic, proliferation and inflammation pathways and have been implicated in the pathogenesis of neurodegenerative, metabolic and oncologic disorders. Both pro- and anti-inflammatory effects have been attributed to SIRT2 and SIRT3, and single deficiency in SIRT2 or SIRT3 had minor or no impact on antimicrobial innate immune responses. Here, we generated a SIRT2/3 double deficient mouse line to study the interactions between SIRT2 and SIRT3. SIRT2/3^−/− mice developed normally and showed subtle alterations of immune cell populations in the bone marrow, thymus, spleen, blood and peritoneal cavity that contained notably more anti-inflammatory B-1a cells and less NK cells. In vitro, SIRT2/3^−/− macrophages favored fatty acid oxidation (FAO) over glycolysis and produced increased levels of both proinflammatory and anti-inflammatory cytokines. In line with metabolic adaptation and increased numbers of peritoneal B-1a cells, SIRT2/3^−/− mice were robustly protected from endotoxemia. Yet, SIRT2/3 double deficiency did not modify endotoxin tolerance. Overall, these data suggest that sirtuins can act in concert or compensate each other for certain immune functions, a parameter to be considered for drug development. Moreover, inhibitors targeting multiple sirtuins developed for clinical purposes may be useful to treat inflammatory diseases.

Sinomenine Induces G1-Phase Cell Cycle Arrest and Apoptosis in Malignant Glioma Cells Via Downregulation of Sirtuin 1 and Induction of p53 Acetylation

Sinomenine, a bioactive alkaloid isolated from the traditional Chinese herb Sinomenium acutum, possesses antiinflammatory, antinociceptive, antifibrotic, and antitumorigenic properties. In this work, we sought to explore the biological effects of sinomenine on glioma cells. It was found that sinomenine caused a concentration-dependent inhibition of viability in both U87 and U251 glioma cells. Sinomenine at 16 μmol/L caused 55% to 60% reduction in the proliferation of U87 and U251 cells. Moreover, sinomenine treatment induced a G0/G1 cell cycle arrest and apoptosis. Mechanistically, sinomenine promoted p53 expression and acetylation and reduced the expression of sirtuin 1. Ectopic expression of sirtuin 1 significantly prevented sinomenine-induced p53 acetylation and growth suppression in glioma cells. Moreover, sinomenine inhibited the growth of U87 xenograft tumors in vivo and raised the p53 protein expression. Collectively, sinomenine shows antiproliferative effects against glioma cells which is mediated through downregulation of sirtuin 1 and induction of p53 activity.

Targeting Sirt-1 controls GVHD by inhibiting T-cell allo-response and promoting Treg stability in mice

Graft-versus-host disease (GVHD) remains one of the major complications after allogeneic bone marrow transplantation (allo-BMT). Sirtuin-1 (Sirt-1) plays a crucial role in various biological processes including cellular senescence, metabolism, and inflammatory responses. Sirt-1 deacetylation regulates different transcription factors that are important for modulating immune responses. In the current study, we addressed the role of Sirt-1 in GVHD induction by employing Sirt-1 conditional knockout mice as well as a pharmacological Sirt-1 inhibitor. Using major histocompatibility complex (MHC)-mismatched and MHC-matched murine BMT models, we found that Sirt-1^-/- T cells had a reduced ability to induce acute GVHD (aGVHD) via enhanced p53 acetylation. Sirt-1-deficient T cells also promoted induced regulatory T cell (iTreg) differentiation and inhibited interferon-γ production after allo-BMT. Sirt-1 deletion in iTregs increased Foxp3 stability and restrained iTreg conversion into pathogenic T cells. Furthermore, we found that administration with a Sirt-1 inhibitor, Ex-527, significantly improved recipient survival and clinical scores, with no signs of tumor relapse. These results indicate that Sirt-1 inhibition can attenuate GVHD while preserving the graft-versus-leukemia effect. Consistently, Sirt-1-deficient T cells also displayed a remarkably reduced ability to induce chronic GVHD (cGVHD). Mechanistic studies revealed that Sirt-1 deficiency in T cells enhanced splenic B-cell reconstitution and reduced follicular T helper cell development. Sirt-1 deficiency in T cells modulated donor B-cell responses reducing both B-cell activation and plasma cell differentiation. In addition, therapeutic Sirt-1 inhibition could both prevent cGVHD and reduce established cGVHD. In conclusion, Sirt-1 is a promising therapeutic target for the control of aGVHD and cGVHD pathogenesis and possesses high potential for clinical application.

Bromodomain and extra-terminal domain inhibition modulates the expression of pathologically relevant microRNAs in diffuse large B-cell lymphoma

Aberrant changes in microRNA expression contribute to lymphomagenesis. Bromodomain and extra-terminal domain inhibitors such as OTX015 (MK-8628, birabresib) have demonstrated preclinical and clinical activity in hematologic tumors. MicroRNA profiling of diffuse large B-cell lymphoma cells treated with OTX015 revealed changes in the expression levels of a limited number of microRNAs, including miR-92a-1-5p, miR-21-3p, miR-155-5p and miR-96-5p. Analysis of publicly available chromatin immunoprecipitation sequencing data of diffuse large B-cell lymphoma cells treated with bromodomain and extra-terminal domain (BET) inhibitors showed that the BET family member BRD4 bound to the upstream regulatory regions of multiple microRNA genes and that this binding decreased following BET inhibition. Alignment of our microRNA profiling data with the BRD4 chromatin immunoprecipitation sequencing data revealed that microRNAs downregulated by OTX015 also exhibited reduced BRD4 binding in their promoter regions following treatment with another bromodomain and extra-terminal domain inhibitor, JQ1, indicating that BRD4 contributes directly to microRNA expression in lymphoma. Treatment with bromodomain and extra-terminal domain inhibitors also decreased the expression of the arginine methyltransferase PRMT5, which plays a crucial role in B-cell transformation and negatively modulates the transcription of miR-96-5p. The data presented here indicate that in addition to previously observed effects on the expression of coding genes, bromodomain and extra-terminal domain inhibitors also modulate the expression of microRNAs involved in lymphomagenesis.

A B-cell receptor-related gene signature predicts survival in mantle cell lymphoma: results from the Fondazione Italiana Linfomi MCL-0208 trial

Mantle cell lymphoma patients have variable clinical courses, ranging from indolent cases that do not require immediate treatment to aggressive, rapidly progressing diseases. Thus, diagnostic tools capable of stratifying patients according to their risk of relapse and death are needed. This study included 83 samples from the Fondazione Italiana Linfomi MCL-0208 clinical trial. Through gene expression profiling and quantitative real-time PCR we analyzed 46 peripheral blood and 43 formalin-fixed paraffin-embedded lymph node samples. A prediction model to classify patients was developed. By analyzing the transcriptome of 27 peripheral blood samples, two subgroups characterized by a differential expression of genes from the B-cell receptor pathway (B-cell receptor^low and B-cell receptor^high) were identified. The prediction model based on the quantitative real-time PCR values of six representative genes (AKT3, BCL2, BTK, CD79B, PIK3CD, and SYK), was used to classify the 83 cases (43 B-cell receptor^low and 40 B-cell receptor^high). The B-cell receptor^high signature associated with shorter progression-free survival (P=0.0074), selected the mantle cell lymphoma subgroup with the shortest progression-free survival and overall survival (P=0.0014 and P=0.029, respectively) in combination with high (>30%) Ki-67 staining, and was an independent predictor of short progression- free survival along with the Mantle Cell Lymphoma International Prognostic Index-combined score. Moreover, the clinical impact of the 6- gene signature related to the B-cell receptor pathway identified a mantle cell lymphoma subset with shorter progression-free survival intervals also in an external independent mantle cell lymphoma cohort homogenously treated with different schedules. In conclusion, this 6-gene signature associates with a poor clinical response in the context of the MCL- 0208 clinical trial. (clinicaltrials.gov identifier: 02354313).

High expression of MAP7 predicts adverse prognosis in young patients with cytogenetically normal acute myeloid leukemia

Microtubule-associated protein 7 (MAP7) plays an important role in cancer cells. In this study, we identified the prognostic significance of MAP7 expression in cytogenetically normal acute myeloid leukemia (CN-AML) patients (aged <60 years) based on several microarray datasets. In the first group (n = 129), high MAP7 expression (MAP7^high) was associated with adverse overall survival (OS; P = 0.0441) and event-free survival (EFS; P = 0.0114) compared with low MAP7 expression (MAP7^low). In addition, the prognostic significance of MAP7 was confirmed by European Leukemia Net (ELN) intermediate-I genetic categories and multivariable analysis. In the second independent group of CN-AML patients (aged <60 years), MAP7^high was also associated with adverse OS (n = 88, OS; P = 0.00811). To understand the inherent mechanisms of MAP7's prognosis, we investigated genome-wide gene/microRNA expression signatures associated with MAP7 expression. Several known oncogenic genes/microRNAs and anti-oncogenic genes/microRNAs were disordered in MAP7^high CN-AML patients. In conclusion, MAP7^high is an adverse prognostic biomarker for CN-AML, which may be attributed to the distinctive genome-wide gene/microRNA expression and related cell signaling pathways.