Drug repositioning strategy for the identification of novel telomere-damaging agents: A role for NAMPT inhibitors.

Drug repositioning strategy represents a valid tool to accelerate the pharmacological development through the identification of new applications for already existing compounds. In this view, we aimed at discovering molecules able to trigger telomere-localized DNA damage and tumor cell death. By applying an automated high-content spinning-disk microscopy, we performed a screening aimed at identifying, on a library of 527 drugs, molecules able to negatively affect the expression of TRF2, a key protein in telomere maintenance. FK866, resulting from the screening as the best candidate hit, was then validated at biochemical and molecular levels and the mechanism underlying its activity in telomere deprotection was elucidated both in vitro and in vivo. The results of this study allow us to discover a novel role of FK866 in promoting, through the production of reactive oxygen species, telomere loss and deprotection, two events leading to an accumulation of DNA damage and tumor cell death. The ability of FK866 to induce telomere damage and apoptosis was also demonstrated in advanced preclinical models evidencing the antitumoral activity of FK866 in triple-negative breast cancer-a particularly aggressive breast cancer subtype still orphan of targeted therapies and characterized by high expression levels of both NAMPT and TRF2. Overall, our findings pave the way to the development of novel anticancer strategies to counteract triple-negative breast cancer, based on the use of telomere deprotecting agents, including NAMPT inhibitors, that would rapidly progress from bench to bedside.

Proton Therapy, Magnetic Nanoparticles and Hyperthermia as Combined Treatment for Pancreatic BxPC3 Tumor Cells.

We present an investigation of the effects on BxPC3 pancreatic cancer cells of proton therapy combined with hyperthermia, assisted by magnetic fluid hyperthermia performed with the use of magnetic nanoparticles. The cells' response to the combined treatment has been evaluated by means of the clonogenic survival assay and the estimation of DNA Double Strand Breaks (DSBs). The Reactive Oxygen Species (ROS) production, the tumor cell invasion and the cell cycle variations have also been studied. The experimental results have shown that the combination of proton therapy, MNPs administration and hyperthermia gives a clonogenic survival that is much smaller than the single irradiation treatment at all doses, thus suggesting a new effective combined therapy for the pancreatic tumor. Importantly, the effect of the therapies used here is synergistic. Moreover, after proton irradiation, the hyperthermia treatment was able to increase the number of DSBs, even though just at 6 h after the treatment. Noticeably, the magnetic nanoparticles' presence induces radiosensitization effects, and hyperthermia increases the production of ROS, which contributes to cytotoxic cellular effects and to a wide variety of lesions including DNA damage. The present study indicates a new way for clinical translation of combined therapies, also in the vision of an increasing number of hospitals that will use the proton therapy technique in the near future for different kinds of radio-resistant cancers.

Radiosensitivity in patients affected by ARPC1B deficiency: a new disease trait?

Actin-related protein 2/3 complex subunit 1B (ARPC1B) deficiency is a recently described inborn error of immunity (IEI) presenting with combined immunodeficiency and characterized by recurrent infections and thrombocytopenia. Manifestations of immune dysregulation, including colitis, vasculitis, and severe dermatitis, associated with eosinophilia, hyper-IgA, and hyper-IgE are also described in ARPC1B-deficient patients. To date, hematopoietic stem cell transplantation seems to be the only curative option for patients. ARPC1B is part of the actin-related protein 2/3 complex (Arp2/3) and cooperates with the Wiskott-Aldrich syndrome protein (WASp) in the regulation of the actin cytoskeleton remodeling and in driving double-strand break clustering for homology-directed repair. In this study, we aimed to investigate radiosensitivity (RS) in ARPC1B-deficient patients to assess whether it can be considered an additional disease trait. First, we performed trio-based next-generation-sequencing studies to obtain the ARPC1B molecular diagnosis in our index case characterized by increased RS, and then we confirmed, using three different methods, an increment of radiosensitivity in all enrolled ARPC1B-deficient patients. In particular, higher levels of chromatid-type aberrations and γH2AX foci, with an increased number of cells arrested in the G2/M-phase of the cell cycle, were found in patients' cells after ionizing radiation exposition and radiomimetic bleomycin treatment. Overall, our data suggest increased radiosensitivity as an additional trait in ARPC1B deficiency and support the necessity to investigate this feature in ARPC1B patients as well as in other IEI with cytoskeleton defects to address specific clinical follow-up and optimize therapeutic interventions.

Factors influencing survival in metastatic castration-resistant prostate cancer therapy.

INTRODUCTION: The number of patients with metastatic castration-resistant prostate cancer (mCRPC) is expected to increase due to the long life expectancy of those with advanced disease who are also more commonly diagnosed today because of stage migration. Several compounds are available for treating these patients. AREAS COVERED: We reviewed currently available treatments for mCRPC, their mechanism of action and resistance, and we explored possible predictors of treatment success useful to predict survival in mCRPC patients. EXPERT OPINION: A combination of molecular, clinical, pathological, and imaging features is necessary to correctly estimate patients' risk of death. The combination of these biomarkers may allow clinicians to tailor treatments based on cancer history and patients' features. The search of predictive biomarkers remains an unmet medical need for most patients with mCRPC.

Micro-RNAs Predict Response to Systemic Treatments in Metastatic Renal Cell Carcinoma Patients: Results from a Systematic Review of the Literature.

Locally advanced or metastatic renal cell carcinomas (mRCCs) account for up to 15% of all kidney cancer diagnoses. Systemic therapies (with or without surgery) represent gold standard treatments, mostly based on tyrosine kinase inhibitors in association with immunotherapy. We provide an overview of the current knowledge of miRNAs as predictors of treatment resistance. A systematic review of the literature was carried out in January 2022 following the PICO methodology. Overall, we included seven studies-four testing plasmatic miRNAs, two exosomal miRNAs, and one urinary miRNA. A total of 789 patients were included (354 for plasmatic miRNAs, 366 for urinary miRNAs, and 69 for exosomal miRNAs). Several miRNAs were tested within the included studies, but six plasmatic (miR9-5-p¸ miR-192, miR193-3p, miR-501-3p¸ miR-221, miR-376b-3p) one urinary (miR-30a-5p), and three exosomal (miR-35-5p, miR-301a-3p, miR-1293) were associated with resistance to systemic treatments or treatment failure in mRCC patients. Results showed a fair accuracy of these biomarkers in predicting treatment resistance and overall survival. However, to date, the biomarkers tested have not been validated and their clinical uses are not recommended. Nevertheless, the literature results are encouraging; future large clinical trials are warranted to validate the effectiveness of these tools in clinical decision-making.

Intra-epithelial non-canonical Activin A signaling safeguards prostate progenitor quiescence.

The healthy prostate is a relatively quiescent tissue. Yet, prostate epithelium overgrowth is a common condition during aging, associated with urinary dysfunction and tumorigenesis. For over thirty years, TGF-ß ligands have been known to induce cytostasis in a variety of epithelia, but the intracellular pathway mediating this signal in the prostate, and its relevance for quiescence, have remained elusive. Here, using mouse prostate organoids to model epithelial progenitors, we find that intra-epithelial non-canonical Activin A signaling inhibits cell proliferation in a Smad-independent manner. Mechanistically, Activin A triggers Tak1 and p38 ΜAPK activity, leading to p16 and p21 nuclear import. Spontaneous evasion from this quiescent state occurs upon prolonged culture, due to reduced Activin A secretion, a condition associated with DNA replication stress and aneuploidy. Organoids capable to escape quiescence in vitro are also able to implant with increased frequency into immunocompetent mice. This study demonstrates that non-canonical Activin A signaling safeguards epithelial quiescence in the healthy prostate, with potential implications for the understanding of cancer initiation, and the development of therapies targeting quiescent tumor progenitors.

Analysis of Short-Term and Stable DNA Damage in Patients with Differentiated Thyroid Cancer Treated with 131I in Hypothyroidism or with Recombinant Human Thyroid-Stimulating Hormone for Remnant Ablation.

It is well known that ionizing radiation can induce genetic damage and that oxidative stress is a major factor inducing it. Our aim was to investigate whether thyroid remnant ablation with low activities of 131I (1,850 MBq) is associated with DNA damage by evaluating the CometAssay, micronuclei, and chromosome aberrations with multicolor fluorescent in situ hybridization. Methods: We studied 62 patients prepared with recombinant human thyroid-stimulating hormone (rhTSH) or by thyroid hormone withdrawal. In both groups, we analyzed stable and unstable genetic alterations before 131I therapy and 1 wk and 3 mo after 131I administration. We also correlated the genetic damage with several variables, including the degree of radiation-induced oxidative stress, genetic polymorphisms of enzymes involved in DNA repair, and antioxidative stress. Results: We found a comparable amount of DNA breaks evaluated by CometAssay and micronuclei testing in both groups of patients at different time points, but there was a significant increase in stable chromosome aberrations evaluated by multicolor fluorescent in situ hybridization (breaks and translocations) in patients prepared with thyroid hormone withdrawal. Overall, high chromosome damage was associated with higher retained body radioactivity and unfavorable gene polymorphism. A high level of free oxygen radicals and a low level of antioxidants were found in all patients at any time point. In particular, patients prepared with thyroid hormone withdrawal, at 3 mo, had significantly higher levels of free oxygen radicals than those prepared with rhTSH. Conclusion: An increase in stable chromosome aberrations with respect to baseline is detectable after administration of low doses of 131I in patients prepared with thyroid hormone withdrawal but not in patients prepared with rhTSH. The clinical significance of these chromosomal alterations remains to be determined.

Effects of the Combined Treatment with a G-Quadruplex-Stabilizing Ligand and Photon Beams on Glioblastoma Stem-like Cells: A Magnetic Resonance Study.

Glioblastoma multiforme is a malignant primary brain tumor with a poor prognosis and high rates of chemo-radiotherapy failure, mainly due to a small cell fraction with stem-like properties (GSCs). The mechanisms underlying GSC response to radiation need to be elucidated to enhance sensitivity to treatments and to develop new therapeutic strategies. In a previous study, two GSC lines, named line #1 and line #83, responded differently to carbon ions and photon beams, with the differences likely attributable to their own different metabolic fingerprint rather than to radiation type. Data from the literature showed the capability of RHPS4, a G-quadruplex stabilizing ligand, to sensitize the glioblastoma radioresistant U251MG cells to X-rays. The combined metabolic effect of ligand #190, a new RHPS4-derivative showing reduced cardiotoxicity, and a photon beam has been monitored by magnetic resonance (MR) spectroscopy for the two GSC lines, #1 and #83, to reveal whether a synergistic response occurs. MR spectra from both lines were affected by single and combined treatments, but the variations of the analysed metabolites were statistically significant mainly in line #1, without synergistic effects due to combination. The multivariate analysis of ten metabolites shows a separation between control and treated samples in line #1 regardless of treatment type, while separation was not detected in line #83.

Efficacy and safety of intravesical fibrin glue instillation for management of patients with refractory hemorrhagic cystitis: 12-months results. A promising therapy for hemorrhagic cystitis.

OBJECTIVES: Fibrin glue (FG) endo-vesical application seems to be a promising therapy for hemorrhagic cystitis (HC). We aimed to evaluate efficacy and safety of FG instillation in patients with HC. METHODS: Patients with HC not responsive to conventional treatments (bladder irrigation, catheterization, blood transfusions, hyperhydration and endoscopic coagulation) were treated with FG endo-vesical instillation (April 2017- December 2018). FG was prepared from 120 mL of patient blood with the Vivostat® system. After standard cystoscopy, bladder was insufflated with carbon dioxide (CO2) according to bladder compliance and autologous FG was applied to bladder wall and bleeding sites. RESULTS: Ten patients included with grade 2 or higher HC secondary to bone marrow graft for hematological diseases (30%) or to actinic cystitis caused by prostate cancer radiotherapy (RT) (70%). The median HC onset time after RT was 4.8 (IQR 3.9- 6.3) years and 35 (IQR 27.5-62.5) days after hematopoietic stem cell transplantation (HSCT). Five patients had a complete response after one treatment, three patients had clinical response (grade < 2 hematuria, amelioration of symptoms), one of them required catheterization and bladder irrigation. One patient required a second instillation of FG achieving a clinical response. No adverse events related to the procedure were recorded, however one patient died for causes not related to the procedure. Median Interstitial Cystitis Symptoms Index was 13.0 (IQR 11.0-15.0) pre-operatively and 4.0 (IQR 2.0-5.0) post-operatively. CONCLUSIONS: Our study showed that, even in hematological patients, autologous FG instillation maybe a safe, repeatable and effective treatment modality in patients with refractory HC.

The Multiple Facets of ATRX Protein.

ATRX gene codifies for a protein member of the SWI-SNF family and was cloned for the first time over 25 years ago as the gene responsible for a rare developmental disorder characterized by α-thalassemia and intellectual disability called Alpha Thalassemia/mental Retardation syndrome X-linked (ATRX) syndrome. Since its discovery as a helicase involved in alpha-globin gene transcriptional regulation, our understanding of the multiple roles played by the ATRX protein increased continuously, leading to the recognition of this multifaceted protein as a central "caretaker" of the human genome involved in cancer suppression. In this review, we report recent advances in the comprehension of the ATRX manifold functions that encompass heterochromatin epigenetic regulation and maintenance, telomere function, replicative stress response, genome stability, and the suppression of endogenous transposable elements and exogenous viral genomes.

A Tale of Ice and Fire: The Dual Role for 17ß-Estradiol in Balancing DNA Damage and Genome Integrity.

17ß-estradiol (E2) regulates human physiology both in females and in males. At the same time, E2 acts as a genotoxic substance as it could induce DNA damages, causing the initiation of cellular transformation. Indeed, increased E2 plasma levels are a risk factor for the development of several types of cancers including breast cancer. This paradoxical identity of E2 undermines the foundations of the physiological definition of "hormone" as E2 works both as a homeostatic regulator of body functions and as a genotoxic compound. Here, (i) the molecular circuitries underlying this double face of E2 are reviewed, and (ii) a possible framework to reconcile the intrinsic discrepancies of the E2 function is reported. Indeed, E2 is a regulator of the DNA damage response, which this hormone exploits to calibrate its genotoxicity with its physiological effects. Accordingly, the genes required to maintain genome integrity belong to the E2-controlled cellular signaling network and are essential for the appearance of the E2-induced cellular effects. This concept requires an "upgrade" to the vision of E2 as a "genotoxic hormone", which balances physiological and detrimental pathways to guarantee human body homeostasis. Deregulation of this equilibrium between cellular pathways would determine the E2 pathological effects.

Association of statin use and oncological outcomes in patients with first diagnosis of T1 high grade non-muscle invasive urothelial bladder cancer: results from a multicenter study.

BACKGROUND: We aimed to test the hypothesis that the immune-modulatory effect of statins may improve survival outcomes in patients with non-muscle invasive bladder cancer (NMIBC). We focused on a cohort of patients diagnosed with high risk NMIBC, that were treated with intravesical BCG immunotherapy. METHODS: We included patients at first diagnosis of T1 high grade NMIBC after transurethral resection of bladder (TURB). All procedures were performed at 18 different tertiary institutions between January 2002 and December 2012. Univariable and multivariable models were used to test differences in terms of residual tumor, disease recurrence, disease progression and overall mortality (OM) rates. RESULTS: Overall, 1510 patients with T1 high grade NMIBC at TURB were included in our analyses. Of these, 402 (26.6%) were statin users. At multivariable analysis, statin use was associated with a higher rate of high-grade BC at re-TURB (OR: 1.37, 95%CI: 1.04-1.78; P=0.022), while at follow-up it was not independently associated with OM (HR: 0.71, 95%CI: 0.50-1.03; P=0.068) and disease progression rates (HR: 0.97, 95%CI: 0.79-1.19; P=0.753). Conversely, statin use has been shown to be independently associated with a lower risk of recurrence (HR:0.80, 95%CI: 0.67-0.95; P=0.009). The median recurrence-free survival was 47 (95%CI 40-49) months for those classified as non-statin users vs. 53 (95%CI 48-68) months in those classified as statin users. CONCLUSIONS: Statin daily intake do not compromise oncological outcomes in high risk NMIBC patients treated with BCG. Moreover, statin may have a beneficial effect on recurrence rates in this cohort of patients.

Outcomes of Robot-assisted Partial Nephrectomy for Clinical T3a Renal Masses: A Multicenter Analysis.

BACKGROUND: Use of partial nephrectomy (PN) in T3 renal cell carcinoma (RCC) is controversial. OBJECTIVE: To evaluate quality outcomes of robot-assisted PN (RAPN) for clinical T3a renal masses (cT3aRM). DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective multicenter analysis of patients with cT3aN0M0 RCC who underwent RAPN. INTERVENTION: RAPN. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary endpoint was a trifecta composite outcome of negative surgical margins, warm ischemia time (WIT) ≤25 min, and no perioperative complications. The optimal outcome was defined as achieving this trifecta and ≥90% preservation of the estimated glomerular filtration rate (eGFR) and no stage upgrading of chronic kidney disease. Multivariable analysis (MVA) identified risk factors associated with lack of the optimal outcome. Kaplan-Meier analysis was conducted for survival outcomes. RESULTS AND LIMITATIONS: Analysis was conducted for 157 patients (median follow-up 26 mo). The median tumor size was 7.0 cm (interquartile range [IQR] 5.0-7.8) and the median RENAL score was 9 (IQR 8-10). Median estimated blood loss (EBL) was 242 ml (IQR 121-354) and the median WIT was 19 min (IQR 15-25). A total of 150 patients (95.5%) had negative margins. Complications were noted in 25 patients (15.9%), with 4.5% having Clavien grade 3-5 complications. The median change in eGFR was 7 ml/min/1.72 m2, with ≥90% eGFR preservation in 55.4%. The trifecta outcome was achieved for 64.3% and the optimal outcome for 37.6% of the patients. MVA revealed that greater age (odds ratio [OR] 1.06; p = 0.002), increasing RENAL score (OR 1.30; p = 0.035), and EBL >300 ml (OR 5.96, p = 0.006) were predictive of failure to achieve optimal outcome. The 5-yr recurrence-free survival, cancer-specific survival, and overall survival, were 82.1%, 93.3%, and 91.3%, respectively. Limitations include the retrospective design. CONCLUSIONS: RAPN for select cT3a renal masses is feasible and safe, with acceptable quality outcomes. Further investigation is requisite to delineate the role of RAPN in cT3a RCC. PATIENT SUMMARY: Robot-assisted partial nephrectomy in patients with stage 3a kidney cancer provided acceptable survival, functional, and morbidity outcomes in the hands of experienced surgeons, and may be considered as an option when clinically indicated.

The Nrf2 induction prevents ferroptosis in Friedreich's Ataxia.

Ferroptosis is an iron-dependent cell death caused by impaired glutathione metabolism, lipid peroxidation and mitochondrial failure. Emerging evidences report a role for ferroptosis in Friedreich's Ataxia (FRDA), a neurodegenerative disease caused by the decreased expression of the mitochondrial protein frataxin. Nrf2 signalling is implicated in many molecular aspects of ferroptosis, by upstream regulating glutathione homeostasis, mitochondrial function and lipid metabolism. As Nrf2 is down-regulated in FRDA, targeting Nrf2-mediated ferroptosis in FRDA may be an attractive option to counteract neurodegeneration in such disease, thus paving the way to new therapeutic opportunities. In this study, we evaluated ferroptosis hallmarks in frataxin-silenced mouse myoblasts, in hearts of a frataxin Knockin/Knockout (KIKO) mouse model, in skin fibroblasts and blood of patients, particularly focusing on ferroptosis-driven gene expression, mitochondrial impairment and lipid peroxidation. The efficacy of Nrf2 inducers to neutralize ferroptosis has been also evaluated.

Hadron Therapy, Magnetic Nanoparticles and Hyperthermia: A Promising Combined Tool for Pancreatic Cancer Treatment.

A combination of carbon ions/photons irradiation and hyperthermia as a novel therapeutic approach for the in-vitro treatment of pancreatic cancer BxPC3 cells is presented. The radiation doses used are 0-2 Gy for carbon ions and 0-7 Gy for 6 MV photons. Hyperthermia is realized via a standard heating bath, assisted by magnetic fluid hyperthermia (MFH) that utilizes magnetic nanoparticles (MNPs) exposed to an alternating magnetic field of amplitude 19.5 mTesla and frequency 109.8 kHz. Starting from 37 °C, the temperature is gradually increased and the sample is kept at 42 °C for 30 min. For MFH, MNPs with a mean diameter of 19 nm and specific absorption rate of 110 ± 30 W/gFe3o4 coated with a biocompatible ligand to ensure stability in physiological media are used. Irradiation diminishes the clonogenic survival at an extent that depends on the radiation type, and its decrease is amplified both by the MNPs cellular uptake and the hyperthermia protocol. Significant increases in DNA double-strand breaks at 6 h are observed in samples exposed to MNP uptake, treated with 0.75 Gy carbon-ion irradiation and hyperthermia. The proposed experimental protocol, based on the combination of hadron irradiation and hyperthermia, represents a first step towards an innovative clinical option for pancreatic cancer.

Could Bladder Multiparametric MRI Be Introduced in Routine Clinical Practice? Role of the New VI-RADS Score: Results From a Prospective Study.

BACKGROUND: The Vesical Imaging Reporting and Data System (VI-RADS) was recently introduced as a standardized approach to reporting multiparametric magnetic resonance imaging (mpMRI) for bladder cancer. We aimed to prospectively analyze its routine use and its diagnostic performance in discriminating non-muscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC). PATIENTS AND METHODS: A total of 38 patients with diagnosis of suspect bladder cancer at cystoscopy underwent bladder mpMRI before transurethral resection of the bladder (TURB). Bladder tumors were categorized according to the VI-RADS. After TURB, the VI-RADS score was compared with histological report for each lesion separately. Receiving operating characteristic and decision curve analyses were used to assess its accuracy and clinical utility. RESULTS: A total of 68 lesions were included, of which 7 (10.3%) were MIBC. The pooled accuracy was 90.0% (95% confidence interval [CI], 75.4%-98.7%). The best threshold was estimated as VI-RADS 4, showing a sensitivity of 85.7% (95% CI, 57.1%-100%) and a specificity of 86.9% (95% CI, 78.7%-95.1%). Decision curve analyses showed that using VI-RADS ≥4 improved the net benefit compared with any default strategy for threshold probabilities of MIBC up to ∼40%, which is a reasonable clinical threshold for planning further treatments. CONCLUSIONS: Our prospective study shows that the use of VI-RADS as a standardized reporting method is appealing and could be considered in clinical practice owing to its high accuracy.

Changes in the Expression of Pre-Replicative Complex Genes in hTERT and ALT Pediatric Brain Tumors.

Background: The up-regulation of a telomere maintenance mechanism (TMM) is a common feature of cancer cells and a hallmark of cancer. Routine methods for detecting TMMs in tumor samples are still missing, whereas telomerase targeting treatments are becoming available. In paediatric cancers, alternative lengthening of telomeres (ALT) is found in a subset of sarcomas and malignant brain tumors. ALT is a non-canonical mechanism of telomere maintenance developed by cancer cells with no-functional telomerase. Methods: To identify drivers and/or markers of ALT, we performed a differential gene expression analysis between two zebrafish models of juvenile brain tumors, that differ only for the telomere maintenance mechanism adopted by tumor cells: one is ALT while the other is telomerase-dependent. Results: Comparative analysis of gene expression identified five genes of the pre-replicative complex, ORC4, ORC6, MCM2, CDC45 and RPA3 as upregulated in ALT. We searched for a correlation between telomerase levels and expression of the pre-replicative complex genes in a cohort of paediatric brain cancers and identified a counter-correlation between telomerase expression and the genes of the pre-replicative complex. Moreover, the analysis of ALT markers in a group of 20 patients confirmed the association between ALT and increased RPA and decreased H3K9me3 localization at telomeres. Conclusions: Our study suggests that telomere maintenance mechanisms may act as a driver of telomeric DNA replication and chromatin status in brain cancers and identifies markers of ALT that could be exploited for precise prognostic and therapeutic purposes.

Expression of tert Prevents ALT in Zebrafish Brain Tumors.

The activation of a telomere maintenance mechanism (TMM) is an essential step in cancer progression to escape replicative senescence and apoptosis. Alternative lengthening of telomeres (ALT) is found in a subset of malignant brain tumors with poor outcomes. Here, we describe a model of juvenile zebrafish brain tumor that progressively develops ALT. We discovered that reduced expression of tert, linked to a widespread hypomethylation of the tert promoter and increase in Terra expression precedes ALT development. Surprisingly, expression of tert during juvenile brain tumor development led to reduced proliferation of tumor cells and prolonged survival. Most importantly, expression of tert reverted all ALT features and normalizes TERRA expression, promoted heterochromatin formation at telomeres, and attenuated telomeric DNA damage. These data suggest that the activity of telomerase goes beyond telomere maintenance and has profound consequences on genome stability.

G-quadruplex Stabilization Fuels the ALT Pathway in ALT-positive Osteosarcoma Cells.

Most human tumors maintain telomere lengths by telomerase, whereas a portion of them (10%-15%) uses a mechanism named alternative lengthening of telomeres (ALT). The telomeric G-quadruplex (G4) ligand RHPS4 is known for its potent antiproliferative effect, as shown in telomerase-positive cancer models. Moreover, RHPS4 is also able to reduce cell proliferation in ALT cells, although the influence of G4 stabilization on the ALT mechanism has so far been poorly investigated. Here we show that sensitivity to RHPS4 is comparable in ALT-positive (U2OS; SAOS-2) and telomerase-positive (HOS) osteosarcoma cell lines, unlinking the telomere maintenance mechanism and RHPS4 responsiveness. To investigate the impact of G4 stabilization on ALT, the cardinal ALT hallmarks were analyzed. A significant induction of telomeric doublets, telomeric clusterized DNA damage, ALT-associated Promyelocytic Leukaemia-bodies (APBs), telomere sister chromatid exchanges (T-SCE) and c-circles was found exclusively in RHPS4-treated ALT cells. We surmise that RHPS4 affects ALT mechanisms through the induction of replicative stress that in turn is converted in DNA damage at telomeres, fueling recombination. In conclusion, our work indicates that RHPS4-induced telomeric DNA damage promotes overactivation of telomeric recombination in ALT cells, opening new questions on the therapeutic employment of G4 ligands in the treatment of ALT positive tumors.

Inhibition of Bromodomain and Extraterminal Domain (BET) Proteins by JQ1 Unravels a Novel Epigenetic Modulation to Control Lipid Homeostasis.

The homeostatic control of lipid metabolism is essential for many fundamental physiological processes. A deep understanding of its regulatory mechanisms is pivotal to unravel prospective physiopathological factors and to identify novel molecular targets that could be employed to design promising therapies in the management of lipid disorders. Here, we investigated the role of bromodomain and extraterminal domain (BET) proteins in the regulation of lipid metabolism. To reach this aim, we used a loss-of-function approach by treating HepG2 cells with JQ1, a powerful and selective BET inhibitor. The main results demonstrated that BET inhibition by JQ1 efficiently decreases intracellular lipid content, determining a significant modulation of proteins involved in lipid biosynthesis, uptake and intracellular trafficking. Importantly, the capability of BET inhibition to slow down cell proliferation is dependent on the modulation of cholesterol metabolism. Taken together, these data highlight a novel epigenetic mechanism involved in the regulation of lipid homeostasis.