TLR3 agonism augments CD47 inhibition in acute myeloid leukemia.

CD47-SIRPa is a myeloid check point pathway that promotes phagocytosis of cells lacking markers for self-recognition. Tumor cells can overexpress CD47 and bind to SIRPa on macrophages, preventing phagocytosis. CD47 expression is enhanced and correlated with a negative prognosis in acute myeloid leukemia (AML), with its blockade leading to cell clearance. ALX90 is an engineered fusion protein with high affinity for CD47. Composed of the N-terminal D1 domain of SIRPα genetically linked to an inactive Fc domain from human immunoglobulin (Ig) G, ALX90 is designed to avoid potential toxicity of CD47-expressing red blood cells. Venetoclax (VEN) is a specific B-cell lymphoma-2 (BCL-2) inhibitor that can restore apoptosis in malignant cells. In AML, VEN is combined with azanucleosides to induce superior remission rates, however treatment for refractory/relapse is an unmet need. We questioned whether the anti-tumor activity of a VENbased regimen can be augmented through CD47 inhibition (CD47i) in AML and how this triplet may be enhanced. Human AML cell lines were sensitive to ALX90 and its addition increased efficacy of a VEN plus azacitidin (VEN+AZA) regimen in vivo. However, CD47i failed to clear bone marrow tumor burden in PDX models. We hypothesized that the loss of resident macrophages in the bone marrow in AML reduced efficiency of CD47i. Therefore, we attempted to enhance this medullary macrophage population with agonism of TLR3 via polyinosinic:polycytidylic acid (poly(I:C)), which led to expansion and activation of medullary macrophages in in vivo AML PDX models and potentiated CD47i. In summary, the addition of poly(I:C) can enhance medullary macrophage populations to potentiate the phagocytosis merited by therapeutic inhibition of CD47.

Assessment of the Impact of Carvedilol Administered Together with Dexrazoxan and Doxorubicin on Liver Structure and Function, Iron Metabolism, and Myocardial Redox System in Rats.

Late cardiotoxicity is a formidable challenge in anthracycline-based anticancer treatments. Previous research hypothesized that co-administration of carvedilol (CVD) and dexrazoxane (DEX) might provide superior protection against doxorubicin (DOX)-induced cardiotoxicity compared to DEX alone. However, the anticipated benefits were not substantiated by the findings. This study focuses on investigating the impact of CVD on myocardial redox system parameters in rats treated with DOX + DEX, examining its influence on overall toxicity and iron metabolism. Additionally, considering the previously observed DOX-induced ascites, a seldom-discussed condition, the study explores the potential involvement of the liver in ascites development. Compounds were administered weekly for ten weeks, with a specific emphasis on comparing parameter changes between DOX + DEX + CVD and DOX + DEX groups. Evaluation included alterations in body weight, feed and water consumption, and analysis of NADPH2, NADP+, NADPH2/NADP+, lipid peroxidation, oxidized DNA, and mRNA for superoxide dismutase 2 and catalase expressions in cardiac muscle. The iron management panel included markers for iron, transferrin, and ferritin. Liver abnormalities were assessed through histological examinations, aspartate transaminase, alanine transaminase, and serum albumin level measurements. During weeks 11 and 21, reduced NADPH2 levels were observed in almost all examined groups. Co-administration of DEX and CVD negatively affected transferrin levels in DOX-treated rats but did not influence body weight changes. Ascites predominantly resulted from cardiac muscle dysfunction rather than liver-related effects. The study's findings, exploring the impact of DEX and CVD on DOX-induced cardiotoxicity, indicate a lack of scientific justification for advocating the combined use of these drugs at histological, biochemical, and molecular levels.

Translational control of Ybx1 expression regulates cardiac function in response to pressure overload in vivo.

RNA-protein interactions are central to cardiac function, but how activity of individual RNA-binding protein is regulated through signaling cascades in cardiomyocytes during heart failure development is largely unknown. The mechanistic target of rapamycin kinase is a central signaling hub that controls mRNA translation in cardiomyocytes; however, a direct link between mTOR signaling and RNA-binding proteins in the heart has not been established. Integrative transcriptome and translatome analysis revealed mTOR dependent translational upregulation of the RNA binding protein Ybx1 during early pathological remodeling independent of mRNA levels. Ybx1 is necessary for pathological cardiomyocyte growth by regulating protein synthesis. To identify the molecular mechanisms how Ybx1 regulates cellular growth and protein synthesis, we identified mRNAs bound to Ybx1. We discovered that eucaryotic elongation factor 2 (Eef2) mRNA is bound to Ybx1, and its translation is upregulated during cardiac hypertrophy dependent on Ybx1 expression. Eef2 itself is sufficient to drive pathological growth by increasing global protein translation. Finally, Ybx1 depletion in vivo preserved heart function during pathological cardiac hypertrophy. Thus, activation of mTORC1 links pathological signaling cascades to altered gene expression regulation by activation of Ybx1 which in turn promotes translation through increased expression of Eef2.

Muscle-specific Cand2 is translationally upregulated by mTORC1 and promotes adverse cardiac remodeling.

The mechanistic target of rapamycin (mTOR) promotes pathological remodeling in the heart by activating ribosomal biogenesis and mRNA translation. Inhibition of mTOR in cardiomyocytes is protective; however, a detailed role of mTOR in translational regulation of specific mRNA networks in the diseased heart is unknown. We performed cardiomyocyte genome-wide sequencing to define mTOR-dependent gene expression control at the level of mRNA translation. We identify the muscle-specific protein Cullin-associated NEDD8-dissociated protein 2 (Cand2) as a translationally upregulated gene, dependent on the activity of mTOR. Deletion of Cand2 protects the myocardium against pathological remodeling. Mechanistically, we show that Cand2 links mTOR signaling to pathological cell growth by increasing Grk5 protein expression. Our data suggest that cell-type-specific targeting of mTOR might have therapeutic value against pathological cardiac remodeling.

The Lack of Synergy between Carvedilol and the Preventive Effect of Dexrazoxane in the Model of Chronic Anthracycline-Induced Cardiomyopathy.

The anticancer efficacy of doxorubicin (DOX) is dose-limited because of cardiomyopathy, the most significant adverse effect. Initially, cardiotoxicity develops clinically silently, but it eventually appears as dilated cardiomyopathy with a very poor prognosis. Dexrazoxane (DEX) is the only FDA-approved drug to prevent the development of anthracycline cardiomyopathy, but its efficacy is insufficient. Carvedilol (CVD) is another product being tested in clinical trials for the same indication. This study's objective was to evaluate anthracycline cardiotoxicity in rats treated with CVD in combination with DEX. The studies were conducted using male Wistar rats receiving DOX (1.6 mg/kg b.w. i.p., cumulative dose: 16 mg/kg b.w.), DOX and DEX (25 mg/kg b.w. i.p.), DOX and CVD (1 mg/kg b.w. i.p.), or a combination (DOX + DEX + CVD) for 10 weeks. Afterward, in the 11th and 21st weeks of the study, echocardiography (ECHO) was performed, and the tissues were collected. The addition of CVD to DEX as a cardioprotective factor against DOX had no favorable advantages in terms of functional (ECHO), morphological (microscopic evaluation), and biochemical alterations (cardiac troponin I and brain natriuretic peptide levels), as well as systemic toxicity (mortality and presence of ascites). Moreover, alterations caused by DOX were abolished at the tissue level by DEX; however, when CVD was added, the persistence of DOX-induced unfavorable alterations was observed. The addition of CVD normalized the aberrant expression of the vast majority of indicated genes in the DOX + DEX group. Overall, the results indicate that there is no justification to use a simultaneous treatment of DEX and CVD in DOX-induced cardiotoxicity.

Pevonedistat and azacitidine upregulate NOXA (PMAIP1) to increase sensitivity to venetoclax in preclinical models of acute myeloid leukemia.

Dysregulation of apoptotic machinery is one mechanism by which acute myeloid leukemia (AML) acquires a clonal survival advantage. B-cell lymphoma protein-2 (BCL2) overexpression is a common feature in hematologic malignancies. The selective BCL2 inhibitor, venetoclax (VEN) is used in combination with azacitidine (AZA), a DNAmethyltransferase inhibitor (DNMTi), to treat patients with AML. Despite promising response rates to VEN/AZA, resistance to the agent is common. One identified mechanism of resistance is the upregulation of myeloid cell leukemia-1 protein (MCL1). Pevonedistat (PEV), a novel agent that inhibits NEDD8-activating enzyme, and AZA both upregulate NOXA (PMAIP1), a BCL2 family protein that competes with effector molecules at the BH3 binding site of MCL1. We demonstrate that PEV/AZA combination induces NOXA to a greater degree than either PEV or AZA alone, which enhances VEN-mediated apoptosis. Herein, using AML cell lines and primary AML patient samples ex vivo, including in cells with genetic alterations linked to treatment resistance, we demonstrate robust activity of the PEV/VEN/AZA triplet. These findings were corroborated in preclinical systemic engrafted models of AML. Collectively, these results provide rational for combining PEV/VEN/AZA as a novel therapeutic approach in overcoming AML resistance in current therapies.

Monitoring Cell-Type-Specific Gene Expression Using Ribosome Profiling In Vivo During Cardiac Hemodynamic Stress.

RATIONALE: Gene expression profiles have been mainly determined by analysis of transcript abundance. However, these analyses cannot capture posttranscriptional gene expression control at the level of translation, which is a key step in the regulation of gene expression, as evidenced by the fact that transcript levels often poorly correlate with protein levels. Furthermore, genome-wide transcript profiling of distinct cell types is challenging due to the fact that lysates from tissues always represent a mixture of cells. OBJECTIVES: This study aimed to develop a new experimental method that overcomes both limitations and to apply this method to perform a genome-wide analysis of gene expression on the translational level in response to pressure overload. METHODS AND RESULTS: By combining ribosome profiling (Ribo-seq) with a ribosome-tagging approach (Ribo-tag), it was possible to determine the translated transcriptome in specific cell types from the heart. After pressure overload, we monitored the cardiac myocyte translatome by purifying tagged cardiac myocyte ribosomes from cardiac lysates and subjecting the ribosome-protected mRNA fragments to deep sequencing. We identified subsets of mRNAs that are regulated at the translational level and found that translational control determines early changes in gene expression in response to cardiac stress in cardiac myocytes. Translationally controlled transcripts are associated with specific biological processes related to translation, protein quality control, and metabolism. Mechanistically, Ribo-seq allowed for the identification of upstream open reading frames in transcripts, which we predict to be important regulators of translation. CONCLUSIONS: This method has the potential to (1) provide a new tool for studying cell-specific gene expression at the level of translation in tissues, (2) reveal new therapeutic targets to prevent cellular remodeling, and (3) trigger follow-up studies that address both, the molecular mechanisms involved in the posttranscriptional control of gene expression in cardiac cells, and the protective functions of proteins expressed in response to cellular stress.

Saraf-dependent activation of mTORC1 regulates cardiac growth.

Pathological cardiac hypertrophy is an independent risk for heart failure (HF) and sudden death. Deciphering signaling pathways regulating intracellular Ca2+ homeostasis that control adaptive and pathological cardiac growth may enable identification of novel therapeutic targets. The objective of the present study is to determine the role of the store-operated calcium entry-associated regulatory factor (Saraf), encoded by the Tmem66 gene, on cardiac growth control in vitro and in vivo. Saraf is a single-pass membrane protein located at the sarco/endoplasmic reticulum and regulates intracellular calcium homeostasis. We found that Saraf expression was upregulated in the hypertrophied myocardium and was sufficient for cell growth in response to neurohumoral stimulation. Increased Saraf expression caused cell growth, which was associated with dysregulation of calcium-dependent signaling and sarcoplasmic reticulum calcium content. In vivo, Saraf augmented cardiac myocyte growth in response to angiotensin II and resulted in increased cardiac remodeling together with worsened cardiac function. Mechanistically, Saraf activated mTORC1 (mechanistic target of rapamycin complex 1) and increased protein synthesis, while mTORC1 inhibition blunted Saraf-dependent cell growth. In contrast, the hearts of Saraf knockout mice and Saraf-deficient myocytes did not show any morphological or functional alterations after neurohumoral stimulation, but Saraf depletion resulted in worsened cardiac function after acute pressure overload. SARAF knockout blunted transverse aortic constriction cardiac myocyte hypertrophy and impaired cardiac function, demonstrating a role for SARAF in compensatory myocyte growth. Collectively, these results reveal a novel link between sarcoplasmic reticulum calcium homeostasis and mTORC1 activation that is regulated by Saraf.

Role of TGF-ß signaling in generation of CD39+CD73+ myeloid cells in tumors.

There is growing evidence that generation of adenosine from ATP, which is mediated by the CD39/CD73 enzyme pair, predetermines immunosuppressive and proangiogenic properties of myeloid cells. We have previously shown that the deletion of the TGF-ß type II receptor gene (Tgfbr2) expression in myeloid cells is associated with decreased tumor growth, suggesting protumorigenic effect of TGF-ß signaling. In this study, we tested the hypothesis that TGF-ß drives differentiation of myeloid-derived suppressor cells into protumorigenic terminally differentiated myeloid mononuclear cells (TDMMCs) characterized by high levels of cell-surface CD39/CD73 expression. We found that TDMMCs represent a major cell subpopulation expressing high levels of both CD39 and CD73 in the tumor microenvironment. In tumors isolated from mice with spontaneous tumor formation of mammary gland and conditional deletion of the type II TGF-ß receptor in mammary epithelium, an increased level of TGF-ß protein was associated with further increase in number of CD39(+)CD73(+) TDMMCs compared with MMTV-PyMT/TGFßRII(WT) control tumors with intact TGF-ß signaling. Using genetic and pharmacological approaches, we demonstrated that the TGF-ß signaling mediates maturation of myeloid-derived suppressor cells into TDMMCs with high levels of cell surface CD39/CD73 expression and adenosine-generating capacity. Disruption of TGF-ß signaling in myeloid cells resulted in decreased accumulation of TDMMCs, expressing CD39 and CD73, and was accompanied by increased infiltration of T lymphocytes, reduced density of blood vessels, and diminished progression of both Lewis lung carcinoma and spontaneous mammary carcinomas. We propose that TGF-ß signaling can directly induce the generation of CD39(+)CD73(+) TDMMCs, thus contributing to the immunosuppressive, proangiogenic, and tumor-promoting effects of this pleiotropic effector in the tumor microenvironment.

Abrogation of TGF beta signaling in mammary carcinomas recruits Gr-1+CD11b+ myeloid cells that promote metastasis.

Aberrant TGFbeta signaling is common in human cancers and contributes to tumor metastasis. Here, we demonstrate that Gr-1+CD11b+ myeloid cells are recruited into mammary carcinomas with type II TGF beta receptor gene (Tgfbr2) deletion and directly promote tumor metastasis. Gr-1+CD11b+ cells infiltrate into the invasive front of tumor tissues and facilitate tumor cell invasion and metastasis through a process involving metalloproteinase activity. This infiltration of Gr-1+CD11b+ cells also results in increased abundance of TGF beta 1 in tumors with Tgfbr2 deletion. The recruitment of Gr-1+CD11b+ cells into tumors with Tgfbr2 deletion involves two chemokine receptor axes, the SDF-1/CXCR4 and CXCL5/CXCR2 axes. Together, these data indicate that Gr-1+CD11b+ cells contribute to TGFbeta-mediated metastasis through enhancing tumor cell invasion and metastasis.

[Myocardial infarction in the course of digoxin and theophylline poisoning].

The aim of this paper is to present a case of the patient who was hospitalized in the Toxicology and Cardiology Department because of suicidal digoxin and theophylline intoxication. Both drugs have complicated mechanism of action and affect cardiovascular system differently, but both predispose to ventricular and supraventricular arrhythmias. In the presented patient conduction disorders, cardiac muscle repolarization disorders and ventricular arrhythmias typical to digoxin poisoning were observed. During hospitalization the patient experienced the ECG and biochemical abnormalities resulting from myocardial infarction. In our paper we have analyzed digoxin and theophylline mechanisms of action and possible impact of each of these drugs on the clinical symptoms that our patient presented.

Disruption of bone morphogenetic protein receptor 2 (BMPR2) in mammary tumors promotes metastases through cell autonomous and paracrine mediators.

Bone morphogenetic proteins (BMPs) are members of the TGF-ß superfamily of signaling molecules. BMPs can elicit a wide range of effects in many cell types and have previously been shown to induce growth inhibition in carcinoma cells as well as normal epithelia. Recently, it has been demonstrated that BMP4 and BMP7 are overexpressed in human breast cancers and may have tumor suppressive and promoting effects. We sought to determine whether disruption of the BMP receptor 2 (BMPR2) would alter mammary tumor progression in mice that express the Polyoma middle T antigen. Mice expressing Polyoma middle T antigen under the mouse mammary tumor virus promoter were combined with mice that have doxycycline-inducible expression of a dominant-negative (DN) BMPR2. We did not observe any differences in tumor latency. However, mice expressing the BMPR2-DN had a fivefold increase in lung metastases. We characterized several cell autonomous changes and found that BMPR2-DN-expressing tumor cells had higher rates of proliferation. We also identified unique changes in inflammatory cells and secreted chemokines/cytokines that accompanied BMPR2-DN-expressing tumors. By immunohistochemistry, it was found that BMPR2-DN primary tumors and metastases had an altered reactive stroma, indicating specific changes in the tumor microenvironment. Among the changes we discovered were increased myeloid derived suppressor cells and the chemokine CCL9. BMP was shown to directly regulate CCL9 expression. We conclude that BMPR2 has tumor-suppressive function in mammary epithelia and microenvironment and that disruption can accelerate mammary carcinoma metastases.

[The neurotoxicity of pyridinium metabolites of haloperidol]. / Neurotoksycznosc pirydyniowych metabolitów haloperydolu.

Haloperydol is a butyrophenone, typical neuroleptic agent characterized as a high antipsychotics effects in the treatment of schizophrenia and in palliative care to alleviation many syndromes, such as naursea, vomiting and delirium. Clinical problems occurs during and after administration of the drug are side effects, particularly extrapyrramidal symptoms (EPS). The neurotoxicity of haloperydol may be initiated by the cationic metabolites of haloperydol, HPP+, RHPP+, formed by oxidation and reduction pathways. These metabolites are transported by human organic cation transporters (hOCT) to several brain structures for exapmle, in substantia nigra, striatum, caudate nucleus, hippocampus. After reaching the dopaminergic neurons inhibits mitochondrial complex I, evidence for free radical involvement, thus leading to neurodegeneration.

Attenuated transforming growth factor beta signaling promotes metastasis in a model of HER2 mammary carcinogenesis.

INTRODUCTION: Transforming growth factor beta (TGFß) plays a major role in the regulation of tumor initiation, progression, and metastasis. It is depended on the type II TGFß receptor (TßRII) for signaling. Previously, we have shown that deletion of TßRII in mammary epithelial of MMTV-PyMT mice results in shortened tumor latency and increased lung metastases. However, active TGFß signaling increased the number of circulating tumor cells and metastases in MMTV-Neu mice. In the current study, we describe a newly discovered connection between attenuated TGFß signaling and human epidermal growth factor receptor 2 (HER2) signaling in mammary tumor progression. METHODS: All studies were performed on MMTV-Neu mice with and without dominant-negative TßRII (DNIIR) in mammary epithelium. Mammary tumors were analyzed by flow cytometry, immunohistochemistry, and immunofluorescence staining. The levels of secreted proteins were measured by enzyme-linked immunosorbent assay. Whole-lung mount staining was used to quantitate lung metastasis. The Cancer Genome Atlas (TCGA) datasets were used to determine the relevance of our findings to human breast cancer. RESULTS: Attenuated TGFß signaling led to a delay tumor onset, but increased the number of metastases in MMTVNeu/DNIIR mice. The DNIIR tumors were characterized by increased vasculogenesis, vessel leakage, and increased expression of vascular endothelial growth factor (VEGF). During DNIIR tumor progression, both the levels of CXCL1/5 and the number of CD11b+Gr1+ cells and T cells decreased. Analysis of TCGA datasets demonstrated a significant negative correlation between TGFBR2 and VEGF genes expression. Higher VEGFA expression correlated with shorter distant metastasis-free survival only in HER2+ patients with no differences in HER2-, estrogen receptor +/- or progesterone receptor +/- breast cancer patients. CONCLUSION: Our studies provide insights into a novel mechanism by which epithelial TGFß signaling modulates the tumor microenvironment, and by which it is involved in lung metastasis in HER2+ breast cancer patients. The effects of pharmacological targeting of the TGFß pathway in vivo during tumor progression remain controversial. The targeting of TGFß signaling should be a viable option, but because VEGF has a protumorigenic effect on HER2+ tumors, the targeting of this protein could be considered when it is associated with attenuated TGFß signaling.

Transforming growth factor beta receptor type III is a tumor promoter in mesenchymal-stem like triple negative breast cancer.

INTRODUCTION: There is a major need to better understand the molecular basis of triple negative breast cancer (TNBC) in order to develop effective therapeutic strategies. Using gene expression data from 587 TNBC patients we previously identified six subtypes of the disease, among which a mesenchymal-stem like (MSL) subtype. The MSL subtype has significantly higher expression of the transforming growth factor beta (TGF-ß) pathway-associated genes relative to other subtypes, including the TGF-ß receptor type III (TßRIII). We hypothesize that TßRIII is tumor promoter in mesenchymal-stem like TNBC cells. METHODS: Representative MSL cell lines SUM159, MDA-MB-231 and MDA-MB-157 were used to study the roles of TßRIII in the MSL subtype. We stably expressed short hairpin RNAs specific to TßRIII (TßRIII-KD). These cells were then used for xenograft tumor studies in vivo; and migration, invasion, proliferation and three dimensional culture studies in vitro. Furthermore, we utilized human gene expression datasets to examine TßRIII expression patterns across all TNBC subtypes. RESULTS: TßRIII was the most differentially expressed TGF-ß signaling gene in the MSL subtype. Silencing TßRIII expression in MSL cell lines significantly decreased cell motility and invasion. In addition, when TßRIII-KD cells were grown in a three dimensional (3D) culture system or nude mice, there was a loss of invasive protrusions and a significant decrease in xenograft tumor growth, respectively. In pursuit of the mechanistic underpinnings for the observed TßRIII-dependent phenotypes, we discovered that integrin-α2 was expressed at higher level in MSL cells after TßRIII-KD. Stable knockdown of integrin-α2 in TßRIII-KD MSL cells rescued the ability of the MSL cells to migrate and invade at the same level as MSL control cells. CONCLUSIONS: We have found that TßRIII is required for migration and invasion in vitro and xenograft growth in vivo. We also show that TßRIII-KD elevates expression of integrin-α2, which is required for the reduced migration and invasion, as determined by siRNA knockdown studies of both TßRIII and integrin-α2. Overall, our results indicate a potential mechanism in which TßRIII modulates integrin-α2 expression to effect MSL cell migration, invasion, and tumorigenicity.

The role of the SHH gene in prostate cancer cell resistance to paclitaxel.

BACKGROUND: The increased activity of the Sonic Hedgehog (SHH) pathway has been demonstrated in many types of cancer including prostate cancer (PCa). It has been shown that SHH pathway is involved in tumor angiogenesis and in regulation of metabolism of cancer stem cells. The increased activity of the SHH pathway is responsible for generation and maintenance of the multidrug resistance in cancer cells. A key role in the development of this insensitivity to cytotoxic drugs play ATP-binding cassette (ABC) transporters. METHODS: SHH encoding plasmid was stably transfected into PCa cell lines DU145 and LNCaP. The expression of SHH was silenced by shRNA and the level of SHH was tested by quantitative (q)PCR and western blot methods. The effect of SHH overexpression in cells after treatment with paclitaxel was measured by MTT assay, crystal violet assay and flow cytometry. The level of 44 ABC transporters was estimated by qPCR. RESULTS: Expression of exogenous SHH protein in DU145 and LNCaP cell lines enhanced their resistance to paclitaxel along with increased expression of ABC transporters transcripts. Paclitaxel treatment further enhanced the expression of increased ABC transporters transcripts in cells overexpressing SHH. CONCLUSIONS: Overexpression of SHH enhances PCa cell lines resistance to paclitaxel. Higher level of SHH leads to increase in ABC transporters expression in a manner dependent on paclitaxel.

Repair of leukemia-associated single nucleotide variants via interallelic gene conversion.

CRISPR-Cas9 is a useful tool for inserting precise genetic alterations through homology-directed repair (HDR), although current methods rely on provision of an exogenous repair template. Here, we tested the possibility of repairing heterozygous single nucleotide variants (SNVs) using the cell's own wild-type allele rather than an exogenous template. Using high-fidelity Cas9 to perform allele-specific CRISPR across multiple human leukemia cell lines as well as in primary hematopoietic cells from patients with leukemia, we find high levels of reversion to wild-type in the absence of exogenous template. Moreover, we demonstrate that bulk treatment to revert a truncating mutation in ASXL1 using CRISPR-mediated interallelic gene conversion (IGC) is sufficient to prolong survival in a human cell line-derived xenograft model (median survival 33 days vs 27.5 days; p = 0.0040). These results indicate that IGC can be applied to numerous types of leukemia and can meaningfully alter cellular phenotypes at scale. Because our method targets single-base mutations, rather than larger variants targeted by IGC in prior studies, it greatly expands the pool of risk-increasing genetic lesions which could potentially be targeted by IGC. This technique may reduce cost and complexity for experiments modeling phenotypic consequences of SNVs. The principles of SNV-specific IGC demonstrated in this proof-of-concept study could be applied to investigate the phenotypic effects of targeted clonal reduction of leukemogenic SNV driver mutations.

Lactate Utilization Enables Metabolic Escape to Confer Resistance to BET Inhibition in Acute Myeloid Leukemia.

Impairing the BET family coactivator BRD4 with small-molecule inhibitors (BETi) showed encouraging preclinical activity in treating acute myeloid leukemia (AML). However, dose-limiting toxicities and limited clinical activity dampened the enthusiasm for BETi as a single agent. BETi resistance in AML myeloblasts was found to correlate with maintaining mitochondrial respiration, suggesting that identifying the metabolic pathway sustaining mitochondrial integrity could help develop approaches to improve BETi efficacy. Herein, we demonstrated that mitochondria-associated lactate dehydrogenase allows AML myeloblasts to utilize lactate as a metabolic bypass to fuel mitochondrial respiration and maintain cellular viability. Pharmacologically and genetically impairing lactate utilization rendered resistant myeloblasts susceptible to BET inhibition. Low-dose combinations of BETi and oxamate, a lactate dehydrogenase inhibitor, reduced in vivo expansion of BETi-resistant AML in cell line and patient-derived murine models. These results elucidate how AML myeloblasts metabolically adapt to BETi by consuming lactate and demonstrate that combining BETi with inhibitors of lactate utilization may be useful in AML treatment. SIGNIFICANCE: Lactate utilization allows AML myeloblasts to maintain metabolic integrity and circumvent antileukemic therapy, which supports testing of lactate utilization inhibitors in clinical settings to overcome BET inhibitor resistance in AML. See related commentary by Boët and Sarry, p. 950.

Length variants of the 5' untranslated region of p53 mRNA and their impact on the efficiency of translation initiation of p53 and its N-truncated isoform ΔNp53.

Recently, we have determined the secondary structure of the 5'-terminal region of p53 mRNA that starts from the P1 transcription initiation site and includes two major translation initiation codons responsible for the synthesis of p53 and ΔNp53 isoform. Here, we showed that when this region was extended into 5' direction to the P0 transcription start site, the two characteristic hairpin motifs found in this region were preserved. Moreover, the presence of alternatively spliced intron 2 did not interfere with the formation of the larger hairpin in which the initiation codon for p53 was embedded. The impact of the different variants of p53 5'-terminal region, which start at P0 or P1 site and end with the initiation codon for p53 or ΔNp53, on the translation of luciferase reporter protein was compared. Strikingly, the efficiency of translation performed in rabbit reticulocyte lysate differed by two orders of magnitude. The toe-printing analysis was also applied to investigate the formation of the ribosomal complex on the model mRNA constructs. The relative translation efficiencies in HeLa and MCF-7 cells were similar to those observed in the cell lysate, although some differences were noted in comparison with cell-free conditions. The results were discussed in terms of the role of secondary structure folding of the 5'-terminal region of p53 mRNA in translation and possible modes of p53 and ΔNp53 translation initiation.

[Classical oxazaphosphorines--metabolism and therapeutic properties--new implications]. / Klasyczne oksazafosforinany--metabolizm i wlasciwosci terapeutyczne--nowe implikacje.

Cyclophosphamide (CPA) and ifosfamide (IFO) belong to oxazaphosphorine drugs and for a few decades have been widely used for treatment of solid tumours and haematological malignancies. Both drugs are administered in pharmacologically inactive form and require metabolic activation by cytochrome P-450 (CYP). Metabolic transformations taking place under the action of specific CYP isoenzymes lead to the formation of therapeutically essential metabolites and some toxic compounds affecting quality of therapy. The first stage of these conversions is connected with hydroxylation reactions occurring on the C-4 carbon atom within a ring and C-1 atoms of 2-chloroethyl chains. As a result of C-4 hydroxylation 4-hydroxy derivatives (4-OH-CPA and 4-OH-IFO) are formed and remain in tautomeric equilibrium with aldo compounds which in cancer cells spontaneously release cytotoxic phosphoramide mustards and urotoxic acrolein. At the same time hydroxychloroethyl compounds formed during hydroxylation of side-chains are unstable and collapse with the release of inter alia nephro- and neurotoxic chloroacetaldehyde (CAA). Due to formation of toxic metabolites it is essential to use some preventive agents such as mesna and recently examined agmatine. Since CPA and IFO are widely used anticancer drugs, their efficacy is limited not only by their toxicity but also due to occurring resistance. This resistance seems to be a result of changes of expression and activity of enzymes such as CYP and aldehyde dehydrogenase (ALDH) and increase of intracellular levels of glutathione (GSH) and glutathione S-transferase (GST). At present a few methods of overcoming this resistance are being examined including the use of metabolism modulators, antisense oligonucleotides selectively inhibiting gene expression, and introducing genes of some CYP isoenzymes to a cancer tissue.