m6A RNA methylation contributes to translational control in heart failure progression

Background/Introduction

Heart failure, characterized by reduced cardiac function and left ventricular dilatation, is a leading cause of hospital admission and mortality. Among increased apoptosis and fibrosis, the progression of heart failure is accompanied by changes in gene expression. There is increasing evidence, that also epigenetic processes such as DNA and histone modifications, long non-coding RNAs and transcription factors orchestrate aberrant gene expression in heart failure. Among these epigenetic processes, N6-methyladenosine (m6A) is the most prevalent modification found in all classes of RNA. Such m6A patterns in for example mRNA can have influence on various mechanisms such as splicing, transport, storage or decay of mRNAs. Due to its reversible and dynamic nature regulated via methyltransferases (mainly the METTL3/METTL14/WTAP-complex) and demethylases (mainly FTO and ALkBH5) it adds a new layer of epigenetic regulation.

Purpose

Changes in epigenetic processes are important mechanisms in heart failure progression. We aimed to elucidate the potential role of m6A methylation in heart failure development.

Methods

We analysed m6A methylation in different stages of heart failure progression in mouse and human tissue via methylated RNA immunoprecipitation (meRIP) followed by next generation sequencing (NGS). With polysome fractionation followed by NGS, we studied a potential link between polysomal occupancy and m6a RNA methylation.

Results

We found that approximately one quarter of all RNA transcripts in healthy mouse and human tissue carry m6A RNA methylation. During progression to heart failure we found that changes in m6A methylation exceed changes in gene expression in both, mouse and human. RNAs with altered m6A levels were mainly linked to metabolic and regulatory pathways, whereas changes in expression represented changes in structural plasticity. Furthermore, we found a link between m6A RNA methylation and altered RNA translation. Interestingly, transcripts with unchanged expression level but a differential change in their methylation level also showed differential polysomal occupancy. We could show a corresponding change in protein level, which points to a potential new mechanism of transcription-independent modulation of translation. The importance of m6A methylation was furthermore confirmed in a cardiomyocyte specific knock-out of the RNA demethylase FTO in mice where it lead to impaired cardiac function compared to control mice.

Conclusions

We could show that the m6A landscape is altered in heart hypertrophy and heart failure. Methylation changes exceed expression changes in disease progression and lead to changes in protein abundance, which uncovers a new transcription-independent mechanism of translation regulation. Therefore, our data suggest that targeting epitranscriptomic mechansims, such as m6A methylation, might be a an interesting approach for thereapeutic interventions.

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): SFB 1002 Modulatory Units in Heart Failure

P1621m6A RNA-methylation in the progression of heart failure

Introduction

N6-Methyladenosine (m6A) is the most abundant modification of RNA and was found to be a dynamic and reversible process. It is found in many classes of RNA, such as mRNA, noncodingRNA (ncRNA) and microRNA (miR). mRNA methylation can affect splicing, transport and storage or decay, ncRNA methylation might influence signal transduction directly as well as it might affect miR interference. Deregulation of such epigenetic processes and aberrant gene expressions are important mechanisms in heart failure. Here we studied the potential relevance of m6A RNA-methylation in cardiac hypertrophy and heart failure development.

Methods and results

m6A RNA-methylation was analysed via methylated RNA immunoprecipitation (meRIP) and subsequent next generation sequencing (NGS). Our data shows that approximately one quarter of the transcripts in the healthy mouse (24.09%) and human heart (14.6%) exhibit m6A RNA-methylation. A mild positive correlation of m6A RNA-methylation at the 5'UTR and coding region with transcript level was observed while m6A RNA-methylation at the 3'UTR showed a mild negative correlation.

We analysed heart failure in mice and humans and observed that changes in m6A RNA-methylation exceed changes in gene-expression (in human data 1219 differentially methylated and 198 diff. expressed, with 30 showing changes in both methylation and expression; in mouse data 1135 diff. methylated and 127 diff. expressed, with 47 showing changes in both methylation and expression). In mouse and human heart failure, transcripts with altered m6A RNA-methylation were mainly linked to metabolic and regulatory pathways while changes in transcript level mainly represented changes in structural plasticity. In the diseased state m6A RNA-methylation showed no correlation to transcript level. To gain further insight into m6A mediated effects on the translational level, polysome-sequencing was applied. These data provide evidence that in the diseased heart changes in m6A RNA-methylation affect RNA translation, represented by a positive correlation (r=0.37, p=2.2e-16) of log2fc changes in translation and m6A methylation.

Conclusions

Our study describes m6A RNA-methylation at the genome-wide level in the human heart. The mouse model provides evidence that changes in m6A RNA-methylation plays an important role in heart failure development by affecting regulatory pathways distinct from those genes with altered expression levels. Our data suggest that modulation of epitranscriptomic processes such as m6A-methylation might be an interesting target for therapeutic interventions.

Acknowledgement/Funding

CRC 1002

P6344Volume overload-triggered pathological myocardial remodeling occurs in the absence of calcium/calmodulin-dependent protein kinase type II delta

Background

Calcium/calmodulin-dependent protein kinase type II delta (CamKIIδ), the predominant cardiac CaMKII isoform, has been implicated in the progression of myocardial infarction- and pressure overload-induced pathological remodeling and heart failure, but its role in volume overload (VO) has not been defined. We have previously reported an activation of CamKII during transition to HF in VO.

Purpose

Here, we analyzed the impact of CamKIIδ deletion in VO-triggered myocardial remodeling and heart failure development.

Methods

CaMKIIδ knockout (CaMKIIδ-KO) and wild-type (WT) littermates were exposed to aorto-caval shunt-induced VO, and the progression of myocardial remodeling was assessed by serial echocardiography, histological and molecular analyses.

Results

CaMKIIδ-KO and WT littermates exhibited similar mortality pattern in response to VO. Serial echocardiographic measurements showed a comparable eccentric myocardial remodeling, altered left ventricle geometry and perturbed ventricular function after shunt. At 12 weeks post-shunt both CaMKIIδ-KO and WT mice experienced comparable increases in relative heart weight, cardiomyocyte diameter, cardiac apoptosis, and hypertrophic genes expression.

Conclusion

We therefore conclude that CaMKIIδ signaling is dispensable for the progression of pathological cardiac remodeling induced by VO. This should be considered before CaMKII inhibition is approved therapeutically for HF treatment.

1180Cardiomyocyte-specific deletion of Brd4 induces hypertrophic cardiomyopathy and suggests a novel function for the chromatin reader as co-repressor in the healthy heart

Introduction

There is increasing evidence that epigenetic mechanisms such as histone modifications integrate stress stimuli into cellular responses during pathogenesis of heart failure (HF). The chromatin readers of the Bromo- and extraterminal domain (BET) family (BRD2, BRD3, BRD4) were reported to recognize acetylated histone tails and to promote transcription. Previously, BET inhibition by JQ1 was shown to displace BET readers from chromatin preventing pathologic remodelling after pressure overload (PO). This suggests a major role for BET proteins in HF development and demonstrates their therapeutic potential. However, JQ1 acts systemically and simultaneously inhibits all BET proteins making precise conclusions on functions of particular BET members in cardiac cells impossible. This work presents the first in vivo deletion of Brd4 in cardiomyocytes and its impact on the healthy and diseased murine heart.

Purpose

This study aims to analyse if deleting Brd4 in cardiomyocytes can protect the heart from pathologic remodelling after PO as observed with BET inhibition.

Methods

The αMHC-MerCreMer line and a conditional Brd4 allele were used to induce a knockout of Brd4 (Brd4 KO) in cardiomyocytes by tamoxifen application (i.p. 3x30 mg/kg/day) at postnatal week 5. Transverse aortic constriction (TAC) was used to induce PO in 8 weeks old mice. Global gene expression changes in Brd4 KO mice were analysed by mRNA sequencing.

Results

Adult Brd4 KO mice showed left ventricular (LV) wall thickening, increased LV mass, cardiomyocyte hypertrophy and mild interstitial fibrosis in comparison to control but lived for over 1 year and showed normal ejection fraction. Transcriptome analysis of Brd4 KO hearts revealed the induction of a pathologic gene program like the expression of fetal genes such as Myh7 or Acta1, Nppa, and Nppb and genes involved in extra cellular matrix organization. After TAC, Brd4 KO mice showed higher mortality with a median survival of 37 days in comparison to 132 days in the control group. However, Brd4 KO mice that survived the acute phase showed significantly higher ejection fraction than control 10 weeks after TAC. Despite the basal hypertrophy, Brd4 KO mice showed no further pathologic remodelling in response to PO and had significantly lower LV weights and diameters.

Conclusions

The development of concentric hypertrophy, expression of fetal genes, and fibrosis with preserved ejection fraction in Brd4 KO animals resemble typical characteristics of hypertrophic cardiomyopathy, and the increased mortality after TAC is likely due to diastolic dysfunction or arrythmias. However, surviving Brd4 KO mice show limited remodelling and partially preserved heart function suggesting cardio-protective potential as previously observed with BET inhibition. Together with relevant literature our findings suggest two distinct roles for Brd4, co-repression of hypertrophy genes in the healthy heart and their co-activation in response to stress.

Acknowledgement/Funding

German Research Foundation - Collaborative Research Center 1002

Docetaxel-carboplatin chemotherapy in combination with cetuximab in patients with locally advanced or metastasized non-small cell lung cancer (NSCLC): Interim results of the nonrandomized phase II study TaxErb

e19062

Background: Combination chemotherapy with carboplatin-docetaxel has been shown to be effective and safe for patients with locally advanced or metastasized NSCLC. The monoclonal anti-EGRF antibody cetuximab has the potential to improve response rates and survival without a substantial increase in toxicity when given in combination with chemotherapy. Methods: Open, non-controlled phase II study with a planned sample size of 70 pts. Pts with locally advanced or metastasized NSCLC, ECOG performance status ≤ 2 and no prior systemic chemotherapy were treated with carboplatin AUC5 (d 1) q4w for 4–6 cycles and docetaxel 35 mg/m2 (d1, 8, 15) q4w; cetuximab 400 / 250 mg/m2 (d 1) q1w until progression or intolerable toxicity (12 month max.). The primary endpoint was response rate defined as complete or partial remission according to RECIST. Secondary endpoints were toxicity, 1 year survival, median and progression free survival. Results: Subject of the interims analysis were 27 pts (25 stage IV, 2 stage IIIb). ECOG 0/1/2 was 33.3%/59.3%/3.7% (1 no data). 63% had prior surgery, 93% prior radiotherapy and all had adjuvant or inductive chemotherapy. Pts received a mean of 3 ± 1.4 cycles docetaxel-carboplatin-cetuximab. 49 adverse events were grade 1–2 and 12 grade 3–5. Skin toxicity (49%; 95%CI: 30%-68%; 41% G1/2, 8% G3/4), dyspnoea (35%; 95%CI: 17%-53%) and diarrhoea (23%; 95%CI: 7 %-39%; 19% G1/2, 4% G3) were most frequent. 11 pts (41%) had toxicity leading to dose reduction. 0 pts had complete and 11 pts had partial remission resulting in a response rate of 40.7% (95%CI: 22%-59%) based on intention to treat. 6 pts had stable disease (22.2%; 95%CI: 7%-38%). 5 pts were not evaluable for response. Conclusions: The combination of carboplatin-docetaxel-cetuximab has an overall acceptable tolerability. With a preliminary response rate of 40.7% the benefit risk assessment was found to be favourable and the study was continued.

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Dose-finding study of fixed dose gemcitabine and escalating doses of ifosfamide given on days 1 and 8 in patients with advanced non-small cell lung cancer

This is a dose-finding study of fixed dose gemcitabine and escalating doses of ifosfamide, in chemo naïve patients with advanced non-small cell lung cancer. The purpose of the study was to determine the optimal dosage and the maximal tolerated dose (MTD) of a specified schedule of gemcitabine and ifosfamide. Patients received gemcitabine 1250 mg/m2 and ifosfamide between 1.6 and 2.2 g/m2, intravenously, on days 1 and 8, repeated every 3 weeks for a maximum of four cycles.

RESULTS

Sixteen patients entered the study. Three patients were entered at the first dose level of ifosfamide (1.6 g/m2) and none experienced any dose limiting (DLT) toxicity. In dose level 2 (1.8 g/m2), two patients had grade IV haematological toxicities, but they reached 21 days without any other dose limiting toxicity (DLT). Three further patients entered at this level but they were withdrawn due to disease progression. The sixth patient entered without any DLT. Three patients entered dose level 3 (2.0 g/m2), without any grade IV toxicity. The first patient entered into dose level 4 (2.2 g/m2), had progressive disease within 21 days and was withdrawn and another three were entered and had no DLT during the first 21 days. Four (33%) of the patients had stable disease and 67% had progressive disease.

CONCLUSION

The MTD of the ifosfamide gemcitabine combination was not reached in the present study, as no DLT was observed. This combination at the dose levels of this protocol has little or no activity in patients with advanced NSCLC.

Phase I dose-escalating study of raltitrexed ('Tomudex') and cisplatin in metastatic non-small cell lung cancer

BACKGROUND

The aim of this Phase I, dose-escalation study was to determine the maximum tolerated dose (MTD), recommended dose (RD), and dose-limiting toxicity (DLT) of a raltitrexed ('Tomudex') and cisplatin combination in patients with previously untreated, metastatic non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients received raltitrexed (15-min intravenous infusion), followed by cisplatin (1-h intravenous infusion), every 3 weeks at escalating dose levels.

RESULTS

In total, 21 patients entered the study. No DLT was observed up to dose level 4 (raltitrexed 3.0 mg/m(2) plus cisplatin 80 mg/m(2)), or in the first 3 patients who received dose level 5 (raltitrexed 3.5 mg/m(2) plus cisplatin 80 mg/m(2)). However, 1 patient, entered at dose level 6 (raltitrexed 4.0 mg/m(2) plus cisplatin 80 mg/m(2)) experienced severe toxicity (including grade 3 diarrhea), and no further patients were recruited at this level. Of 4 additional patients who received raltitrexed 3.5 mg/m(2) plus cisplatin 80 mg/m(2), 3 also experienced DLTs. The most common adverse events included nausea/vomiting, asthenia, diarrhea, and hematologic toxicities. Of 19 patients evaluated for response, 3 achieved a partial response, 13 had stable disease, and 3 progressed.

CONCLUSIONS

The MTD is raltitrexed 3.5 mg/m(2) plus cisplatin 80 mg/m(2), and the RD for future studies is raltitrexed 3.0 mg/m(2) plus cisplatin 80 mg/m(2); DLTs were diarrhea and asthenia. The combination of raltitrexed and cisplatin shows clinical activity in patients with metastatic NSCLC.

Reduction of chemotherapy-induced febrile leucopenia by prophylactic use of ciprofloxacin and roxithromycin in small-cell lung cancer patients: an EORTC double-blind placebo-controlled phase III study

BACKGROUND

CDE (cyclophosphamide, doxorubicin, etoposide) is one of the standard chemotherapy regimens in the treatment of small-cell lung cancer (SCLC), with myelosuppression as dose-limiting toxicity. In this trial the impact of prophylactic antibiotics on incidence of febrile leucopenia (FL) during chemotherapy for SCLC was evaluated.

PATIENTS AND METHODS

Patients with chemo-naïve SCLC were randomized to standard-dose CDE (C 1,000 mg/m2 day 1, D 45 mg/m2 day 1, E 100 mg/m2 days 1-3. i.v., q 3 weeks, x5) or to intensified CDE chemotherapy (125% dose, q 2 weeks, x4, with filgrastim 5 microg/kg/day days 4-13) to assess the impact on survival (n = 240 patients). Patients were also randomized to prophylactic antibiotics (ciprofloxacin 750 mg plus roxithromycin 150 mg, bid. days 4-13) or to placebo in a 2 x 2 factorial design (first 163 patients). This manuscript focuses on the antibiotics question.

RESULTS

The incidence of FL during the first cycle was 25% of patients in the placebo and 11% in the antibiotics arm (P = 0.010; 1-sided), with an overall incidence through all cycles of 43% vs. 24% respectively (P = 0.007; 1-sided). There were less Gram-positive (12 vs. 4), Gram-negative (20 vs. 5) and clinically documented (38 vs. 15) infections in the antibiotics arm. The use of therapeutic antibiotics was reduced (P = 0.013; 1-sided), with less hospitalizations due to FL (31 vs. 17 patients, P = 0.013: 1-sided). However, the overall number of days of hospitalization was not reduced (P = 0.05; 1-sided). The number of infectious deaths was nil in the antibiotics vs. five (6%) in the placebo arm (P = 0.022; 2-sided).

CONCLUSIONS

Prophylactic ciprofloxacin plus roxithromycin during CDE chemotherapy reduced the incidence of FL, the number of infections, the use of therapeutic antibiotics and hospitalizations due to FL by approximately 50%, with reduced number of infectious deaths. For patients with similar risk for FL, the prophylactic use of antibiotics should be considered.