Understanding Sorafenib-Induced Cardiovascular Toxicity: Mechanisms and Treatment Implications

Tyrosine kinase inhibitors (TKIs) have been recognized as crucial agents for treating various tumors, and one of their key targets is the intracellular site of the vascular endothelial growth factor receptor (VEGFR). While TKIs have demonstrated their effectiveness in solid tumor patients and increased life expectancy, they can also lead to adverse cardiovascular effects including hypertension, thromboembolism, cardiac ischemia, and left ventricular dysfunction. Among the TKIs, sorafenib was the first approved agent and it exerts anti-tumor effects on hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC) by inhibiting angiogenesis and tumor cell proliferation through targeting VEGFR and RAF. Unfortunately, the adverse cardiovascular effects caused by sorafenib not only affect solid tumor patients but also limit its application in curing other diseases. This review explores the mechanisms underlying sorafenib-induced cardiovascular adverse effects, including endothelial dysfunction, mitochondrial dysfunction, endoplasmic reticulum stress, dysregulated autophagy, and ferroptosis. It also discusses potential treatment strategies, such as antioxidants and renin-angiotensin system inhibitors, and highlights the association between sorafenib-induced hypertension and treatment efficacy in cancer patients. Furthermore, emerging research suggests a link between sorafenib-induced glycolysis, drug resistance, and cardiovascular toxicity, necessitating further investigation. Overall, understanding these mechanisms is crucial for optimizing sorafenib therapy and minimizing cardiovascular risks in cancer patients.

Acute heart failure following pazopanib treatment: a literature review featuring two case reports

Tyrosine kinase inhibitors (TKIs) have transformed cancer treatment but are associated with cardiovascular toxicity, including heart failure. This review examines the cardiotoxicity of pazopanib, a VEGFR-TKI, through two case reports and explores potential mechanisms. The importance of vigilant clinical monitoring to prevent cardiac dysfunction in cancer patients receiving pazopanib is emphasized. We present two cases of acute heart failure following pazopanib treatment. Case 1 involves a comorbidity-free, 62-year-old woman with metastatic renal cell carcinoma who experienced irreversible heart failure. In case 2, a 40-year-old woman with a history of anthracycline-containing chemotherapy developed reversible left ventricular systolic dysfunction following pazopanib discontinuation. Both patients received appropriate management for their heart failure symptoms. Case 1's condition rapidly deteriorated, leading to her unfortunate demise 3 months after starting pazopanib. In contrast, case 2's cardiac function improved after discontinuing pazopanib. The advent of TKIs has revolutionized cancer treatment, but their association with cardiovascular toxicity necessitates meticulous monitoring of patients. The cases presented here highlight the importance of recognizing and managing cardiotoxicity, particularly in patients without prior cardiovascular risk factors. Understanding the underlying mechanisms and risk factors for TKI-induced heart failure is crucial to optimize patient care and treatment outcomes. Oncologists should be vigilant in identifying clinical symptoms and closely monitoring cardiac function throughout TKI therapy.

Erlotinib combination with a mitochondria-targeted ubiquinone effectively suppresses pancreatic cancer cell survival

BACKGROUND

Pancreatic cancer is a leading cause of cancer-related deaths. Increased activity of the epidermal growth factor receptor (EGFR) is often observed in pancreatic cancer, and the small molecule EGFR inhibitor erlotinib has been approved for pancreatic cancer therapy by the food and drug administration. Nevertheless, erlotinib alone is ineffective and should be combined with other drugs to improve therapeutic outcomes. We previously showed that certain receptor tyrosine kinase inhibitors can increase mitochondrial membrane potential (Δψ_m), facilitate tumor cell uptake of Δψ_m-sensitive agents, disrupt mitochondrial homeostasis, and subsequently trigger tumor cell death. Erlotinib has not been tested for this effect.

AIM

To determine whether erlotinib can elevate Δψ_m and increase tumor cell uptake of Δψ_m-sensitive agents, subsequently triggering tumor cell death.

METHODS

Δψ_m-sensitive fluorescent dye was used to determine how erlotinib affects Δψ_m in pancreatic adenocarcinoma (PDAC) cell lines. The viability of conventional and patient-derived primary PDAC cell lines in 2D- and 3D cultures was measured after treating cells sequentially with erlotinib and mitochondria-targeted ubiquinone (MitoQ), a Δψ_m-sensitive MitoQ. The synergy between erlotinib and MitoQ was then analyzed using SynergyFinder 2.0. The preclinical efficacy of the two-drug combination was determined using immune-compromised nude mice bearing PDAC cell line xenografts.

RESULTS

Erlotinib elevated Δψ_m in PDAC cells, facilitating tumor cell uptake and mitochondrial enrichment of Δψ_m-sensitive agents. MitoQ triggered caspase-dependent apoptosis in PDAC cells in culture if used at high doses, while erlotinib pretreatment potentiated low doses of MitoQ. SynergyFinder suggested that these drugs synergistically induced tumor cell lethality. Consistent with in vitro data, erlotinib and MitoQ combination suppressed human PDAC cell line xenografts in mice more effectively than single treatments of each agent.

CONCLUSION

Our findings suggest that a combination of erlotinib and MitoQ has the potential to suppress pancreatic tumor cell viability effectively.

Artificial Intelligence and Machine Learning Methods to Evaluate Cardiotoxicity following the Adverse Outcome Pathway Frameworks

Cardiovascular disease is a leading global cause of mortality. The potential cardiotoxic effects of chemicals from different classes, such as environmental contaminants, pesticides, and drugs can significantly contribute to effects on health. The same chemical can induce cardiotoxicity in different ways, following various Adverse Outcome Pathways (AOPs). In addition, the potential synergistic effects between chemicals further complicate the issue. In silico methods have become essential for tackling the problem from different perspectives, reducing the need for traditional in vivo testing, and saving valuable resources in terms of time and money. Artificial intelligence (AI) and machine learning (ML) are among today's advanced approaches for evaluating chemical hazards. They can serve, for instance, as a first-tier component of Integrated Approaches to Testing and Assessment (IATA). This study employed ML and AI to assess interactions between chemicals and specific biological targets within the AOP networks for cardiotoxicity, starting with molecular initiating events (MIEs) and progressing through key events (KEs). We explored methods to encode chemical information in a suitable way for ML and AI. We started with commonly used approaches in Quantitative Structure-Activity Relationship (QSAR) methods, such as molecular descriptors and different types of fingerprint. We then increased the complexity of encoders, incorporating graph-based methods, auto-encoders, and character embeddings employed in neural language processing. We also developed a multimodal neural network architecture, capable of considering the complementary nature of different chemical representations simultaneously. The potential of this approach, compared to more conventional architectures designed to handle a single encoder, becomes apparent when the amount of data increases.

A strategy for low-cost portable monitoring of plasma drug concentrations using a sustainable boron-doped-diamond chip

On-site monitoring of plasma drug concentrations is required for effective therapies. Recently developed handy biosensors are not yet popular owing to insufficient evaluation of accuracy on clinical samples and the necessity of complicated costly fabrication processes. Here, we approached these bottlenecks via a strategy involving engineeringly unmodified boron-doped diamond (BDD), a sustainable electrochemical material. A sensing system based on a ∼1 cm² BDD chip, when analysing rat plasma spiked with a molecular-targeting anticancer drug, pazopanib, detected clinically relevant concentrations. The response was stable in 60 sequential measurements on the same chip. In a clinical study, data obtained with a BDD chip were consistent with liquid chromatography-mass spectrometry results. Finally, the portable system with a palm-sized sensor containing the chip analysed ∼40 μL of whole blood from dosed rats within ∼10 min. This approach with the 'reusable' sensor may improve point-of-monitoring systems and personalised medicine while reducing medical costs.

Three tyrosine kinase inhibitors cause cardiotoxicity by inducing endoplasmic reticulum stress and inflammation in cardiomyocytes

BACKGROUND

Tyrosine kinase inhibitors (TKIs) are anti-cancer therapeutics often prescribed for long-term treatment. Many of these treatments cause cardiotoxicity with limited cure. We aim to clarify molecular mechanisms of TKI-induced cardiotoxicity so as to find potential targets for treating the adverse cardiac complications.

METHODS

Eight TKIs with different levels of cardiotoxicity reported are selected. Phenotypic and transcriptomic responses of human cardiomyocytes to TKIs at varying doses and times are profiled and analyzed. Stress responses and signaling pathways that modulate cardiotoxicity induced by three TKIs are validated in cardiomyocytes and rat hearts.

RESULTS

Toxicity rank of the eight TKIs determined by measuring their effects on cell viability, contractility, and respiration is largely consistent with that derived from database or literature, indicating that human cardiomyocytes are a good cellular model for studying cardiotoxicity. When transcriptomes are measured for selected TKI treatments with different levels of toxicity in human cardiomyocytes, the data are classified into 7 clusters with mainly single-drug clusters. Drug-specific effects on the transcriptome dominate over dose-, time- or toxicity-dependent effects. Two clusters with three TKIs (afatinib, ponatinib, and sorafenib) have the top enriched pathway as the endoplasmic reticulum stress (ERS). All three TKIs induce ERS in rat primary cardiomyocytes and ponatinib activates the IRE1α-XBP1s axis downstream of ERS in the hearts of rats underwent a 7-day course of drug treatment. To look for potential triggers of ERS, we find that the three TKIs induce transient reactive oxygen species followed by lipid peroxidation. Inhibiting either PERK or IRE1α downstream of ERS blocks TKI-induced cardiac damages, represented by the induction of cardiac fetal and pro-inflammatory genes without causing more cell death.

CONCLUSIONS

Our data contain rich information about phenotypic and transcriptional responses of human cardiomyocytes to eight TKIs, uncovering potential molecular mechanisms in modulating cardiotoxicity. ER stress is activated by multiple TKIs and leads to cardiotoxicity through promoting expression of pro-inflammatory factors and cardiac fetal genes. ER stress-induced inflammation is a promising therapeutic target to mitigate ponatinib- and sorafenib-induced cardiotoxicity.

Cardiotoxicity of Selected Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitors in Patients with Renal Cell Carcinoma

Renal cell carcinoma (RCC) is one of the most frequent malignant neoplasms of the kidney. The therapeutic options available for the treatment of advanced or metastatic RCC include vascular endothelial growth factor receptor (VEGFR)-targeted molecules, for example, tyrosine kinase inhibitors (TKI). Various VEGFR-TKIs proved to be effective in the treatment of patients with solid tumours. The combination of two drugs may prove most beneficial in the treatment of metastatic RCC; however, it also enhances the risk of toxicity compared to monotherapy. Specific VEGFR-TKIs (e.g., sunitinib, sorafenib or pazopanib) may increase the rate of cardiotoxicity in metastatic settings. VEGF inhibitors modulate multiple signalling pathways; thus, the identification of the mechanism underlying cardiotoxicity appears challenging. VEGF signalling is vital for the maintenance of cardiomyocyte homeostasis and cardiac function; therefore, its inhibition can be responsible for the reported adverse effects. Disturbed growth factor signalling pathways may be associated with endothelial dysfunction, impaired revascularization, the development of dilated cardiomyopathy, cardiac hypertrophies and altered peripheral vascular load. Patients at high cardiovascular risk at baseline could benefit from clinical follow-up in the first 2-4 weeks after the introduction of targeted molecular therapy; however, there is no consensus concerning the surveillance strategy.

Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation

Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.

Mitochondrial Toxicity Associated with Imatinib and Sorafenib in Isolated Rat Heart Fibers and the Cardiomyoblast H9c2 Cell Line

Tyrosine kinase inhibitors (TKIs) are associated with cardiac toxicity, which may be caused by mitochondrial toxicity. The underlying mechanisms are currently unclear and require further investigation. In the present study, we aimed to investigate in more detail the role of the enzyme complexes of the electron transfer system (ETS), mitochondrial oxidative stress, and mechanisms of cell death in cardiac toxicity associated with imatinib and sorafenib. Cardiac myoblast H9c2 cells were exposed to imatinib and sorafenib (1 to 100 µM) for 24 h. Permeabilized rat cardiac fibers were treated with both drugs for 15 min. H9c2 cells exposed to sorafenib for 24 h showed a higher membrane toxicity and ATP depletion in the presence of galactose (favoring mitochondrial metabolism) compared to glucose (favoring glycolysis) but not when exposed to imatinib. Both TKIs resulted in a higher dissipation of the mitochondrial membrane potential in galactose compared to glucose media. Imatinib inhibited Complex I (CI)- and CIII- linked respiration under both conditions. Sorafenib impaired CI-, CII-, and CIII-linked respiration in H9c2 cells cultured with glucose, whereas it inhibited all ETS complexes with galactose. In permeabilized rat cardiac myofibers, acute exposure to imatinib and sorafenib decreased CI- and CIV-linked respiration in the presence of the drugs. Electron microscopy showed enlarged mitochondria with disorganized cristae. In addition, both TKIs caused mitochondrial superoxide accumulation and decreased the cellular GSH pool. Both TKIs induced caspase 3/7 activation, suggesting apoptosis as a mechanism of cell death. Imatinib and sorafenib impaired the function of cardiac mitochondria in isolated rat cardiac fibers and in H9c2 cells at plasma concentrations reached in humans. Both imatinib and sorafenib impaired the function of enzyme complexes of the ETS, which was associated with mitochondrial ROS accumulation and cell death by apoptosis.

Mitochondrial dynamics imbalance and mitochondrial dysfunction contribute to the molecular cardiotoxic effects of lenvatinib

Lenvatinib is a tyrosine kinase inhibitor (TKI) approved for the treatment of resistant differentiated thyroid cancer, advanced renal cell carcinoma, unresectable hepatocellular carcinoma, and endometrial carcinoma. Although it is successful in cancer treatment, it can cause life-threatening side effects such as cardiotoxicity. The molecular mechanism of cardiotoxicity caused by lenvatinib is not fully known. In this study, the molecular mechanism of lenvatinib's cardiotoxicity was investigated focusing on mitochondrial toxicity in the H9c2 cardiomyoblastic cell line. Lenvatinib inhibited cell viability at 48 and 72 h exposure with three selected concentrations (1.25 μM, 5 μM and 10 μM); and inhibited intracellular ATP after 72 h exposure compared to the control group. Mitochondrial membrane potential was decreased after 48 h and did not show significant changes after 72 h exposure. Evaluated with real-time PCR, mitochondrial dynamics (Mfn1, Mfn2, OPA1, DRP1, Fis1) expression levels after lenvatinib treatment significantly changed. Lenvatinib triggered the tendency from fusion to fission in mitochondria after 48 h exposure, and increased both fusion and fission after 72 h. The mtDNA ratio increased after 48 h and decreased after 72 h. ASK1, JNK and AMPKα2 increased. UCP2 showed downregulation, SOD2 level showed upregulation and Cat levels decreased after drug treatment. Nrf1 and Nrf2 also changed concentration-dependently. Protein carbonyl levels increased significantly after lenvatinib treatments indicating oxidative stress. The protein levels of the electron transport chain complexes, LONP1, UCP2, and P21 showed significant differences after lenvatinib treatment. The outcome of our study is expected to be a contribution to the understanding of the molecular mechanisms of TKI-induced cardiotoxicity.

Insulin Resistance and Pellino-1 Mediated Decrease in the Activities of Vasodilator Signaling Contributes to Sunitinib-Induced Hypertension

Antiangiogenic tyrosine kinases inhibitors induce hypertension, which may increase the incidents of cardiovascular complications and limit their use. However, the mechanisms by which usage of TKIs results in hypertension have not been fully understood. Here, we report the potential mechanisms of how sunitinib, a widely used TKI, induces hypertension. Male SD rats were randomly divided into control group and sunitinib-administrated group. We show that sunitinib administration for seven days caused a significant increase in artery blood pressure, along with glycerolipid metabolism abnormalities including decreased food intake and low body weight, hypoglycemia, hyperinsulinemia. Sunitinib administration also resulted in a significant increase in the levels of insulin autoantibody (IAA), cyclic adenosine monophosphate and free fatty acid in serum; whereas, sunitinib administration had no effects on serum glucagon levels. Sunitinib led to the decreased insulin sensitivity as determined by insulin tolerance test (ITT) and glucose tolerance test (GTT), reflecting insulin resistance occurred in sunitinib-treated rats. The results obtained from wire myograph assay in the mesenteric arteries show that endothelium-dependent relaxation, but not endothelium-independent relaxation, was impaired by sunitinib. Furthermore, western blot analysis revealed that the expressions levels of phosphorylated IRS-1, Pellino-1, AKT and eNOS were significantly attenuated by sunitinib in rat mesenteric artery tissues and in the sunitinib-treated primary cultured mesenteric artery endothelial cells. The levels of serum and endothelium-derived nitric oxide were also significantly decreased by sunitinib. Moreover, sunitinib-induced decrease in the expression levels of phosphorylated AKT and eNOS was further reduced by knocking down of Pellino-1 in MAECs. Our results suggest that sunitinib causes vascular dysfunction and hypertension, which are associated with insulin resistance- and Pellino-1-mediated inhibition of AKT/eNOS/NO signaling. Our results may provide a rational for preventing and/or treating sunitinib-induced endothelial dysfunction and hypertension.

Extended regorafenib treatment can be linked with mitochondrial damage leading to cardiotoxicity

Regorafenib (RGF) has a great success in the treatment of colorectal cancer, gastrointestinal stromal tumours and hepatocellular carcinoma by inhibiting angiogenic, stromal and oncogenic kinases. However, RGF can induce life-threatening cardiotoxicity including hypertension and cardiac ischemia/infarction. The molecular mechanism of the adverse effects has not been elucidated. Mitochondrial dysfunction is one of the major causes of cardiac diseases since cardiac cells highly need ATP for their contractility. Therefore, we aimed to investigate molecular mechanisms of RGF-induced cardiac adverse effects using H9c2 cell model by focusing on mitochondria. Cells were treated with 0-20 μM RGF for 48 and 72 h. According to our results, RGF inhibited cell proliferation and decreased the ATP content of the cells depending on the exposure time and concentration. Loss of mitochondrial membrane potential was also observed at high dose. Mitochondrial fusion/fission genes and antioxidant SOD2 (superoxide dismutase) gene expression levels increased at high doses in both treatments. Mitochondrial DNA content decreased as exposure time and concentration increased. Also, protein expression levels of mitochondrial complex I and V have reduced and stress protein HSP70 level has increased following RGF treatment. Structural abnormalities in mitochondria was seen with transmission electron microscopy at the applied higher doses. Our findings suggest that RGF-induced cardiotoxicity may be associated with mitochondrial damage in cardiac cells.

Cardiovascular toxicity induced by anti-VEGF/VEGFR agents: a special focus on definitions, diagnoses, mechanisms and management

INTRODUCTION

Vascular endothelial growth factor (VEGF) is a key target in cancer therapy. However, cardiovascular safety has been one of the most challenging aspects of anti-VEGF/VEGF receptor (VEGFR) agent development and therapy. While accurate diagnostic modalities for assessment of cardiac function have been developed over the past few decades, a lack of an optimal definition and precise mechanism still places a significant limit on the effective management of cardiovascular toxicity.

AREAS COVERED

Here, we report the cardiovascular toxicity profile associated with anti-VEGF/VEGFR agents and summarize the clinical diagnoses as well as management that are already performed in clinical practice or are currently being investigated. Furthermore, the review discusses the potential molecular toxicological mechanisms, which may provide strategies to prevent toxicity and drive drug discovery.

EXPERT OPINION

Cardiovascular toxicity associated with anti-VEGF/VEGFR agents has been a substantial risk for cancer treatment. To improve its management, the development of guidelines for prevention, monitoring and treatment of cardiovascular toxicity has become a hot topic. The summary of cardiovascular toxicity profile, mechanisms and management given in this review is not only significant for the optimal use of existing anti-VEGF/VEGFR agents to protect patients predisposed to cardiovascular toxicity but is also beneficial for drug development.

Integrated molecular signaling involving mitochondrial dysfunction and alteration of cell metabolism induced by tyrosine kinase inhibitors in cancer

Cancer cells have unlimited replicative potential, insensitivity to growth-inhibitory signals, evasion of apoptosis, cellular stress, and sustained angiogenesis, invasiveness and metastatic potential. Cancer cells adequately adapt cell metabolism and integrate several intracellular and redox signaling to promote cell survival in an inflammatory and hypoxic microenvironment in order to maintain/expand tumor phenotype. The administration of tyrosine kinase inhibitor (TKI) constitutes the recommended therapeutic strategy in different malignancies at advanced stages.

There are important interrelationships between cell stress, redox status, mitochondrial function, metabolism and cellular signaling pathways leading to cell survival/death. The induction of apoptosis and cell cycle arrest widely related to the antitumoral properties of TKIs result from tightly controlled events involving different cellular compartments and signaling pathways. The aim of the present review is to update the most relevant studies dealing with the impact of TKI treatment on cell function. The induction of endoplasmic reticulum (ER) stress and Ca²⁺ disturbances, leading to alteration of mitochondrial function, redox status and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways that involve cell metabolism reprogramming in cancer cells will be covered. Emphasis will be given to studies that identify key components of the integrated molecular pattern including receptor tyrosine kinase (RTK) downstream signaling, cell death and mitochondria-related events that appear to be involved in the resistance of cancer cells to TKI treatments.

Pazopanib-induced fatal heart failure in a patient with unresectable soft tissue sarcoma and review of literature

INTRODUCTION

Pazopanib, an oral multi-targeted tyrosine kinase inhibitor, is associated with improved outcomes in patients with unresectable or metastatic soft tissue sarcoma. Pazopanib may cause cardiotoxicity such as heart failure.

CASE REPORT

A 50-year-old female patient with no cardiovascular risk factors other than the previous treatment with adriamycin had a baseline left ventricular ejection fraction of 60%. She was receiving pazopanib 800 mg once daily for advanced leiomyosarcoma of the presacral area. On the 60th day of treatment, she presented with fatigue, palpitation, and exertional dyspnea for several days. Echocardiography was performed, and left ventricular ejection fraction was measured as 25%. Pazopanib-induced heart failure was considered and all other possible preliminary diagnoses were excluded.

MANAGEMENT AND OUTCOME

Pazopanib was stopped immediately. Bisoprolol fumarate 5 mg orally once daily, spironolactone 100 mg orally once daily, furosemide 40 mg orally once daily, and ramipril 2.5 mg orally once daily were started. The patient's symptoms partially improved. Second echocardiography was performed after 15 days, and left ventricular ejection fraction was measured as 35%. But, despite pazopanib was not resumed and cardiac support treatment was administered, she died four weeks after discontinuation of pazopanib due to heart failure.

DISCUSSION

Pazopanib-induced heart failure may be fatal. Physicians and patients should be aware of the cardiotoxicity risk when managing the use of pazopanib in soft tissue sarcoma.

Mitochondrial oxidative stress plays a critical role in the cardiotoxicity of sunitinib: Running title: Sunitinib and oxidative stress in hearts

Sunitinib is cardiotoxic, but the mechanisms are not entirely clear. We aimed to enlarge our knowledge about the role of mitochondria in cardiac toxicity of sunitinib in vitro and in vivo. For this reason, we studied the toxicity of sunitinib on cardiac H9c2 cells exposed for 24 h, permeabilized rat cardiac fibers exposed for 15 min and in mice treated orally with sunitinib for 2 weeks (7.5 mg/kg/day). In H9c2 cells exposed for 24 h, sunitinib was more cytotoxic under galactose (favoring mitochondrial metabolism) compared to glucose conditions (favoring glycolysis). Sunitinib dissipated the mitochondrial membrane potential starting at 10 μM under glucose and at 5 μM under galactose conditions. Sunitinib reduced activities of mitochondrial enzyme complexes of the electron transport chain (ETC), increased mitochondrial ROS accumulation and decreased the cellular GSH pool. Electron microscopy revealed swollen mitochondria with loss of cristae. Accordingly, sunitinib caused caspase 3 activation and DNA fragmentation in H9c2 cells. Co-exposure with mito-TEMPO (mitochondrial-specific ROS scavenger) for 24 h prevented ATP and GSH depletion, as well as the increases in H₂O₂ and caspase 3/7 activity observed with sunitinib. In mice, treatment with sunitinib for two weeks increased plasma concentrations of troponin I and creatine kinase MB, indicating cardiomyocyte damage. The activity of enzyme complexes of the ETCwas decreased, mitochondrial ROS were increased and cleavage of caspase 3 was increased, suggesting cardiomyocyte apoptosis. In conclusion, mitochondrial damage with ROS accumulation appears to be an important mechanism of cardiotoxicity associated with sunitinib, eventually leading to apoptotic cell death.

Personalized medicine in cardio-oncology: the role of induced pluripotent stem cell

Treatment of cancer has evolved in the last decade with the introduction of new therapies. Despite these successes, the lingering cardiotoxic side-effects from chemotherapy remain a major cause of morbidity and mortality in cancer survivors. These effects can develop acutely during treatment, or even years later. Although many risk factors can be identified prior to beginning therapy, unexpected toxicity still occurs, often with lasting consequences. Specifically, cardiotoxicity results in cardiac cell death, eventually leading to cardiomyopathy and heart failure. Certain risk factors may predispose an individual to experiencing adverse cardiovascular effects, and when unexpected cardiotoxicity occurs, it is generally managed with supportive care. Animal models of chemotherapy-induced cardiotoxicity have provided some mechanistic insights, but the precise mechanisms by which these drugs affect the heart remains unknown. Moreover, the genetic rationale as to why some patients are more susceptible to developing cardiotoxicity has yet to be determined. Many genome-wide association studies have identified genomic variants that could be associated with chemotherapy-induced cardiotoxicity, but the lack of validation has made these studies more speculative rather than definitive. With the advent of human induced pluripotent stem cell (iPSC) technology, researchers not only have the opportunity to model human diseases, but also to screen drugs for their efficacy and toxicity using human cell models. Furthermore, it allows us to conduct validation studies to confirm the role of genomic variants in human diseases. In this review, we discuss the role of iPSCs in modelling chemotherapy-induced cardiotoxicity.

Increased Afterload Augments Sunitinib-Induced Cardiotoxicity in an Engineered Cardiac Microtissue Model

Sunitinib, a multitargeted oral tyrosine kinase inhibitor, used widely to treat solid tumors, results in hypertension in up to 47% and left ventricular dysfunction in up to 19% of treated individuals. The relative contribution of afterload toward inducing cardiac dysfunction with sunitinib treatment remains unknown. We created a preclinical model of sunitinib cardiotoxicity using engineered microtissues that exhibited cardiomyocyte death, decreases in force generation, and spontaneous beating at clinically relevant doses. Simulated increases in afterload augmented sunitinib cardiotoxicity in both rat and human microtissues, which suggest that antihypertensive therapy may be a strategy to prevent left ventricular dysfunction in patients treated with sunitinib.

Systems pharmacological analysis of mitochondrial cardiotoxicity induced by selected tyrosine kinase inhibitors

Tyrosine kinase inhibitors (TKIs) are targeted therapies rapidly becoming favored over conventional cytotoxic chemotherapeutics. Our study investigates two FDA approved TKIs, DASATINIB; indicated for IMATINIB-refractory chronic myeloid leukemia, and SORAFENIB; indicated for hepatocellular carcinoma and advanced renal cell carcinoma. Limited but crucial evidence suggests that these agents can have cardiotoxic side effects ranging from hypertension to heart failure. A greater understanding of the underlying mechanisms of this cardiotoxicity are needed as concerns grow and the capacity to anticipate them is lacking. The objective of this study was to explore the mitochondrial-mediated cardiotoxic mechanisms of the two selected TKIs. This was achieved experimentally using immortalized human cardiomyocytes, AC16 cells, to investigate dose- and time-dependent cell killing, along with measurements of temporal changes in key signaling proteins involved in the intrinsic apoptotic and autophagy pathways upon exposure to these agents. Quantitative systems pharmacology (QSP) models were developed to capture the toxicological response in AC16 cells using protein dynamic data. The developed QSP models captured well all the various trends in protein signaling and cellular responses with good precision on the parameter estimates, and were successfully qualified using external data sets. An interplay between the apoptotic and autophagic pathways was identified to play a major role in determining toxicity associated with the investigated TKIs. The established modeling platform showed utility in elucidating the mechanisms of cardiotoxicity of SORAFENIB and DASATINIB. It may be useful for other small molecule targeted therapies demonstrating cardiac toxicities, and may aid in informing alternate dosing strategies to alleviate cardiotoxicity associated with these therapies.

Kinome and Transcriptome Profiling Reveal Broad and Distinct Activities of Erlotinib, Sunitinib, and Sorafenib in the Mouse Heart and Suggest Cardiotoxicity From Combined Signal Transducer and Activator of Transcription and Epidermal Growth Factor Receptor Inhibition

BACKGROUND

Most novel cancer therapeutics target kinases that are essential to tumor survival. Some of these kinase inhibitors are associated with cardiotoxicity, whereas others appear to be cardiosafe. The basis for this distinction is unclear, as are the molecular effects of kinase inhibitors in the heart.

METHODS AND RESULTS

We administered clinically relevant doses of sorafenib, sunitinib (cardiotoxic multitargeted kinase inhibitors), or erlotinib (a cardiosafe epidermal growth factor receptor inhibitor) to mice daily for 2 weeks. We then compared the effects of these 3 kinase inhibitors on the cardiac transcriptome using RNAseq and the cardiac kinome using multiplexed inhibitor beads coupled with mass spectrometry. We found unexpectedly broad molecular effects of all 3 kinase inhibitors, suggesting that target kinase selectivity does not define either the molecular response or the potential for cardiotoxicity. Using in vivo drug administration and primary cardiomyocyte culture, we also show that the cardiosafety of erlotinib treatment may result from upregulation of the cardioprotective signal transducer and activator of transcription 3 pathway, as co-treatment with erlotinib and a signal transducer and activator of transcription inhibitor decreases cardiac contractile function and cardiomyocyte fatty acid oxidation.

CONCLUSIONS

Collectively our findings indicate that preclinical kinome and transcriptome profiling may predict the cardiotoxicity of novel kinase inhibitors, and suggest caution for the proposed therapeutic strategy of combined signal transducer and activator of transcription/epidermal growth factor receptor inhibition for cancer treatment.

A Novel Positron Emission Tomography (PET) Approach to Monitor Cardiac Metabolic Pathway Remodeling in Response to Sunitinib Malate

Sunitinib is a tyrosine kinase inhibitor approved for the treatment of multiple solid tumors. However, cardiotoxicity is of increasing concern, with a need to develop rational mechanism driven approaches for the early detection of cardiac dysfunction. We sought to interrogate changes in cardiac energy substrate usage during sunitinib treatment, hypothesising that these changes could represent a strategy for the early detection of cardiotoxicity. Balb/CJ mice or Sprague-Dawley rats were treated orally for 4 weeks with 40 or 20 mg/kg/day sunitinib. Cardiac positron emission tomography (PET) was implemented to investigate alterations in myocardial glucose and oxidative metabolism. Following treatment, blood pressure increased, and left ventricular ejection fraction decreased. Cardiac [¹⁸F]-fluorodeoxyglucose (FDG)-PET revealed increased glucose uptake after 48 hours. [¹¹C]Acetate-PET showed decreased myocardial perfusion following treatment. Electron microscopy revealed significant lipid accumulation in the myocardium. Proteomic analyses indicated that oxidative metabolism, fatty acid β-oxidation and mitochondrial dysfunction were among the top myocardial signalling pathways perturbed. Sunitinib treatment results in an increased reliance on glycolysis, increased myocardial lipid deposition and perturbed mitochondrial function, indicative of a fundamental energy crisis resulting in compromised myocardial energy metabolism and function. Our findings suggest that a cardiac PET strategy may represent a rational approach to non-invasively monitor metabolic pathway remodeling following sunitinib treatment.

FGF2 Prevents Sunitinib-Induced Cardiotoxicity in Zebrafish and Cardiomyoblast H9c2 Cells

Sunitinib is used extensively in the treatment of metastatic renal cell carcinoma and imatinib-resistant gastrointestinal stromal tumors. However, the undesirable cardiotoxic effects of sunitinib, such as congestive heart failure and hypertension, limit its use in the clinical setting. As multiple receptor tyrosine kinases are inhibited by sunitinib, it raises a question as to which target mediates sunitinib-induced cardiotoxicity. Here, we reported that the injection of fibroblast growth factor 2 (FGF2) mRNA into one- to two-cell stage embryos protected against sunitinib-induced cardiotoxicity in zebrafish. In addition, FGF2 significantly prevented sunitinib-induced cardiotoxicity in cardiomyoblast H9c2 cells, possibly via activating the PLC-γ/c-Raf/CREB pathway. Importantly, FGF2 did not compromise the antitumor activity of sunitinib in Caki-1 and OS-RC-2 renal cell carcinoma cells. Molecular docking simulations further revealed an interaction between the tyrosine kinase domain of FGF receptor 1 (FGFR1) and sunitinib. Taken together, our results clearly demonstrated that FGF2 inhibition plays an important role in sunitinib-induced cardiotoxicity both in vitro and in vivo. This study also provided a basis for further research on sunitinib-induced cardiotoxicity and may allow rational design of new sunitinib derivatives with fewer or weak cardiotoxic effects.

Progress on the cardiotoxicity of sunitinib: Prognostic significance, mechanism and protective therapies

Tyrosine kinase inhibitors (TKIs) are multi-targeted anti-cancer agents effective in the treatment of renal cell carcinoma (RCC), imatinib-resistant gastrointestinal stromal tumor (GIST) and pancreatic cancer (PC). Targeting and inhibiting a wide range of oncogenically relevant receptor tyrosine kinases (RTKs), TKIs have been the golden standard treatment of several types of cancer. The cardiotoxicity of TKIs, however, has also emerged alongside their anti-cancer potencies and has attracted research attention. Over the past few years significant progress has been made in developing a deeper understanding of aspects such as extent of cardiotoxicity, prognostic implications and survival predictions, toxicological mechanisms, and potential cardioprotective therapies. In this review we focus on a typical TKI sunitinib and summarize the up-to-date knowledge of sunitinib-induced cardiac abnormalities reported in clinical studies, weighing their implications of prognostic values. We also examine recent findings in underlying mechanisms, and development of potential cardioprotective agents.

Non-proliferative and Proliferative Lesions of the Cardiovascular System of the Rat and Mouse

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Japan (JSTP), Europe (ESTP), Great Britain (BSTP) and North America (STP) to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The primary purpose of this publication is to provide a standardized nomenclature for characterizing lesions observed in the cardiovascular (CV) system of rats and mice commonly used in drug or chemical safety assessment. The standardized nomenclature presented in this document is also available electronically for society members on the internet (http://goreni.org). Accurate and precise morphologic descriptions of changes in the CV system are important for understanding the mechanisms and pathogenesis of those changes, differentiation of natural and induced injuries and their ultimate functional consequence. Challenges in nomenclature are associated with lesions or pathologic processes that may present as a temporal or pathogenic spectrum or when natural and induced injuries share indistinguishable features. Specific nomenclature recommendations are offered to provide a consistent approach.

Analysis of Tyrosine Kinase Inhibitor-Mediated Decline in Contractile Force in Rat Engineered Heart Tissue

Introduction

Left ventricular dysfunction is a frequent and potentially severe side effect of many tyrosine kinase inhibitors (TKI). The mode of toxicity is not identified, but may include impairment of mitochondrial or sarcomeric function, autophagy or angiogenesis, either as an on-target or off-target mechanism.

Methods and Results

We studied concentration-response curves and time courses for nine TKIs in three-dimensional, force generating engineered heart tissue (EHT) from neonatal rat heart cells. We detected a concentration- and time-dependent decline in contractile force for gefitinib, lapatinib, sunitinib, imatinib, sorafenib, vandetanib and lestaurtinib and no decline in contractile force for erlotinib and dasatinib after 96 hours of incubation. The decline in contractile force was associated with an impairment of autophagy (LC3 Western blot) and appearance of autophagolysosomes (transmission electron microscopy).

Conclusion

This study demonstrates the feasibility to study TKI-mediated force effects in EHTs and identifies an association between a decline in contractility and inhibition of autophagic flux.

Mitogen-activated protein kinases pathways mediate the sunitinib-induced hypertrophy in rat cardiomyocyte H9c2 cells

Sunitinib (SUN) is a multi-targeted tyrosine kinase inhibitor used for the treatment of gastrointestinal stromal tumors and renal cell carcinoma. Cardiotoxicity has been reported as a significant side effect associated with the SUN treatment, yet the mechanism is poorly understood. The main purpose of this study was to investigate the potential effects of SUN on cardiac hypertrophic genes and the role of mitogen-activated protein kinases (MAPKs) signaling pathway in rat cardiomyocyte H9c2 cell line. In the present study, real-time quantitative polymerase chain reaction showed that the treatment of H9c2 cells with increasing concentrations of SUN (0, 1, 2.5, and 5 µM) significantly induced hypertrophic gene markers, such as brain natriuretic peptides (BNP) and myosin heavy chain (β-MHC and α-MHC) in concentration- and time-dependent manners. The onset of mRNA induction was observed as early as 9 h and remained elevated for at least 18 h after treatment with SUN 5 µM. At the protein level, Western blot analysis showed that SUN increased BNP and β-MHC, while it inhibited α-MHC protein levels in a concentration-dependent manner. These SUN-mediated effects were associated with increase in cell size and hypertrophy by approximately 70 % at the highest concentration, 5 µM. Importantly, inhibition of the MAPK signaling pathway using SB203580 (p38 MAPK inhibitor), U0126 (extracellular signal-regulated kinase inhibitor), and SP600125 (c-Jun NH2-terminal kinase inhibitor) significantly potentiated the SUN-induced BNP and β-MHC mRNA levels, but did alter the α-MHC level. Whereas at the protein level, MAPK inhibitors generally decreased the SUN-induced BNP, whereas only SB and U0 increased β-MHC protein levels with no effect on α-MHC, which were associated with a significant decrease in cell size. Together, these results indicate that SUN induced hypertrophic gene expression through MAPK-dependent mechanisms.

Cardiac and vascular toxicities of angiogenesis inhibitors: The other side of the coin

Angiogenesis is one of the best-described tumor hallmarks. Targeting angiogenesis is becoming a successful strategy to suppress cancer growth. Vascular endothelial growth factor (VEGF), the fulcrum of angiogenesis, contributes to vascular and cardiac homeostasis. Angiogenesis inhibitors classically associated with vascular side effects are increasingly recognized for cardiac adverse effects as reflected by several meta-analyses. A global approach to these findings is a pressing need, and future strategies involving collaboration among different medical specialties are highly encouraged.

Strain echocardiography combined with pharmacological stress test for early detection of anthracycline induced cardiomyopathy

INTRODUCTION

Advances in echocardiography, including 2-D speckle tracking to quantitate myocardial strain and strain rate, have improved myocardial functional and mechanical evaluation and may provide a more sensitive assessment of cardiac functional and mechanical changes. Additionally, evaluating myocardial performance induced by a pharmacologic stress test (dobutamine infusion) may further improve the evaluation of potential changes in cardiac function. This study evaluates the use of 2-D speckle tracking strain echocardiography (2DSE) combined with a dobutamine stress test to detect doxorubicin induced cardiomyopathy in the rat.

METHODS

Rats were dosed once per week with 2 mg/kg doxorubicin for 6 weeks. Echocardiography was performed weekly at rest and during dobutamine infusion (20 mcg/kg/min IV).

RESULTS

Throughout the study there were no differences between control and doxorubicin treated groups at rest for radial strain, circumferential strain, fractional shortening (FS), or heart rate (HR). During dobutamine infusion, radial strain, circumferential strain, FS, and HR similarly increased significantly in both the control and doxorubicin treated groups at weeks 0, 1, and 2. At week 3 there was a significant attenuation of the increase in radial strain in the doxorubicin treated group, and at weeks 4 and 6 there was significant attenuation in radial strain and circumferential strain. No significant differences were detected in FS or HR between the two groups at any time points. Histology of the left ventricle at week 7 showed mild changes (mild cardiomyocyte vacuolation with minimal inflammation and no fibrosis) in the doxorubicin treated animals as compared to the control animals, which were consistent with mild doxorubicin induced injury.

DISCUSSION

These data suggest that 2 D speckle tracking strain echocardiography combined with dobutamine stress test can detect early changes in myocardial function and may be useful tools in early detection of drug-induced cardiac dysfunction.

Prevention of Pazopanib-Induced Prolonged Cardiac Repolarization and Proarrhythmic Effects

Background

Pazopanib (PZP) may induce prolonged cardiac repolarization and proarrhythmic effects, similarly to other tyrosine kinase inhibitors.

Objectives

To demonstrate PZP-induced prolonged cardiac repolarization and proarrhythmic electrophysiological effects and to investigate possible preventive effects of metoprolol and diltiazem on ECG changes (prolonged QT) in an experimental rat model.

Methods

Twenty-four Sprague-Dawley adult male rats were randomly assigned to 4 groups (n = 6). The first group (normal group) received 4 mL of tap water and the other groups received 100 mg/kg of PZP (Votrient^® tablet) perorally, via orogastric tubes. After 3 hours, the following solutions were intraperitoneally administered to the animals: physiological saline solution (SP), to the normal group and to the second group (control-PZP+SP group); 1 mg/kg metoprolol (Beloc, Ampule, AstraZeneca), to the third group (PZP+metoprolol group); and 1mg/kg diltiazem (Diltiazem, Mustafa Nevzat), to the fourth group (PZP+diltiazem group). One hour after, and under anesthesia, QTc was calculated by recording ECG on lead I.

Results

The mean QTc interval values were as follows: normal group, 99.93 ± 3.62 ms; control-PZP+SP group, 131.23 ± 12.21 ms; PZP+metoprolol group, 89.36 ± 3.61 ms; and PZP+diltiazem group, 88.86 ± 4.04 ms. Both PZP+metoprolol and PZP+diltiazem groups had significantly shorter QTc intervals compared to the control-PZP+SP group (p < 0.001).

Conclusion

Both metoprolol and diltiazem prevented PZP-induced QT interval prolongation. These drugs may provide a promising prophylactic strategy for the prolonged QTc interval associated with tyrosine kinase inhibitor use.

Development of cardiac hypertrophy by sunitinib in vivo and in vitro rat cardiomyocytes is influenced by the aryl hydrocarbon receptor signaling pathway

Sunitinib (SUN) is a new tyrosine kinase inhibitor that possesses both anti-angiogenic and anti-tumor activities. Although SUN has improved survival rate in cancer patients, cardiotoxicity has been reported as a significant side effect. Several studies suggested a role for the aryl hydrocarbon receptor (AhR) and its regulated genes such as cytochrome P4501A1 (CYP1A1) in the pathogenesis of heart failure and cardiac hypertrophy. To test the hypothesis that SUN induces cardiac hypertrophy through the modulation of AhR, Wistar albino rats were treated for 15 and 30 days with increasing doses of SUN (25, 50, and 100 mg/kg), whereas at the in vitro level, rat cardiomyocyte H9c2 cells were incubated with SUN (1, 2.5, and 5 μM). Thereafter, cardiac hypertrophy parameters were determined at the biochemical, histopathology, and gene expression levels. SUN treatment causes increase in cardiac enzymes, changes in histopathology, and induction in several hypertrophic markers. This was associated with proportional increase in the CYP1A1 gene in a concentration- and time-dependent manner. The direct involvement of AhR in the SUN-induced cardiac hypertrophy in H9c2 cells was supported by the ability of resveratrol, an AhR antagonist, to block the SUN-induced hypertrophy and the ability of SB203580, a novel AhR agonist, to potentiate SUN-induced hypertrophic genes. This is the first demonstration that SUN induces hypertrophic genes in vivo and in vitro rat cardiomyocyte through AhR/CYP1A1-mediated mechanism.

Tyrosine kinase inhibitor (TKI)-induced cardiotoxicity: approaches to narrow the gaps between preclinical safety evaluation and clinical outcome

Although therapies targeted to inhibit the activity of certain tyrosine kinases (TK) have helped advance cancer therapy in recent years, reports of cardiac toxicity following treatment with tyrosine kinase inhibitors (TKIs) were unexpected and not well predicted by preclinical studies. Such clinical findings exposed gaps in current preclinical drug testing for predicting the development of cardiac toxicities in humans. These gaps included a lack of a comprehensive TKI mechanism of action determination and appropriate cardiac functional evaluation. New preclinical approaches are suggested to address these issues. In addition to tyrosine kinase inhibition, other factors that may play a role in drug-induced cardiac effects should be assessed, such as unintended secondary targets of TKIs, toxic drug metabolites and drug accumulation in the heart. Both on-target and off-target toxic effects of TKIs on cultured cardiac myocytes have now been shown to be detectable, providing a rationale for using cardiomyocytes as a screening tool to study potential TKI-mediated cardiotoxicity. Incorporating isolated perfused heart methodology to chronic/subchronic rodent studies or including echocardiography in chronic large animal toxicity studies may improve the detection of changes in cardiac function over current methods, and they may eventually become a routine tool for screening drugs with suspected cardiotoxic potential. Further, assessing drug toxicity and efficacy together in an animal model of disease is highly informative for candidate drug selection, and should be encouraged to assess specific safety endpoints, such as cardiovascular function. Together, these approaches will help better close the gaps between preclinical testing and clinical outcomes.

Cancer therapy modulates VEGF signaling and viability in adult rat cardiac microvascular endothelial cells and cardiomyocytes

This work was motivated by the incomplete characterization of the role of vascular endothelial growth factor-A (VEGF-A) in the stressed heart in consideration of upcoming cancer treatment options challenging the natural VEGF balance in the myocardium. We tested, if the cytotoxic cancer therapy doxorubicin (Doxo) or the anti-angiogenic therapy sunitinib alters viability and VEGF signaling in primary cardiac microvascular endothelial cells (CMEC) and adult rat ventricular myocytes (ARVM). ARVM were isolated and cultured in serum-free medium. CMEC were isolated from the left ventricle and used in the second passage. Viability was measured by LDH-release and by MTT-assay, cellular respiration by high-resolution oxymetry. VEGF-A release was measured using a rat specific VEGF-A ELISA-kit. CMEC were characterized by marker proteins including CD31, von Willebrand factor, smooth muscle actin and desmin. Both Doxo and sunitinib led to a dose-dependent reduction of cell viability. Sunitinib treatment caused a significant reduction of complex I and II-dependent respiration in cardiomyocytes and the loss of mitochondrial membrane potential in CMEC. Endothelial cells up-regulated VEGF-A release after peroxide or Doxo treatment. Doxo induced HIF-1α stabilization and upregulation at clinically relevant concentrations of the cancer therapy. VEGF-A release was abrogated by the inhibition of the Erk1/2 or the MAPKp38 pathway. ARVM did not answer to Doxo-induced stress conditions by the release of VEGF-A as observed in CMEC. VEGF receptor 2 amounts were reduced by Doxo and by sunitinib in a dose-dependent manner in both CMEC and ARVM. In conclusion, these data suggest that cancer therapy with anthracyclines modulates VEGF-A release and its cellular receptors in CMEC and ARVM, and therefore alters paracrine signaling in the myocardium.

Molecular mechanisms of hypertension and heart failure due to antiangiogenic cancer therapies

Targeted antiangiogenic cancer therapies have revolutionized the treatment of highly vascularized cancers such as metastatic renal cell carcinoma and gastrointestinal stromal tumors. Such agents act by inhibiting the actions of proangiogenic growth factors and their receptor tyrosine kinases, which are known to be overexpressed in cancer. However, these factors also play an important role in normal cardiovascular physiology. This article summarizes the incidences of cardiovascular toxicities (namely hypertension and heart failure) associated with the most commonly used antiangiogenic therapies, and then presents data from preclinical and clinical studies to provide some insight into the underlying molecular mechanisms.

A novel preclinical strategy for identifying cardiotoxic kinase inhibitors and mechanisms of cardiotoxicity

RATIONALE

Despite intense interest in strategies to predict which kinase inhibitor (KI) cancer therapeutics may be associated with cardiotoxicity, current approaches are inadequate. Sorafenib is a KI of concern because it inhibits growth factor receptors and Raf-1/B-Raf, kinases that are upstream of extracellular signal-regulated kinases (ERKs) and signal cardiomyocyte survival in the setting of stress.

OBJECTIVES

To explore the potential use of zebrafish as a preclinical model to predict cardiotoxicity and to determine whether sorafenib has associated cardiotoxicity, and, if so, define the mechanisms.

METHODS AND RESULTS

We find that the zebrafish model is readily able to discriminate a KI with little or no cardiotoxicity (gefitinib) from one with demonstrated cardiotoxicity (sunitinib). Sorafenib, like sunitinib, leads to cardiomyocyte apoptosis, a reduction in total myocyte number per heart, contractile dysfunction, and ventricular dilatation in zebrafish. In cultured rat cardiomyocytes, sorafenib induces cell death. This can be rescued by adenovirus-mediated gene transfer of constitutively active MEK1, which restores ERK activity even in the presence of sorafenib. Whereas growth factor-induced activation of ERKs requires Raf, α-adrenergic agonist-induced activation of ERKs does not require it. Consequently, activation of α-adrenergic signaling markedly decreases sorafenib-induced cell death. Consistent with these in vitro data, inhibition of α-adrenergic signaling with the receptor antagonist prazosin worsens sorafenib-induced cardiomyopathy in zebrafish.

CONCLUSIONS

Zebrafish may be a valuable preclinical tool to predict cardiotoxicity. The α-adrenergic signaling pathway is an important modulator of sorafenib cardiotoxicity in vitro and in vivo and appears to act through a here-to-fore unrecognized signaling pathway downstream of α-adrenergic activation that bypasses Raf to activate ERKs.