Topoisomerase II alpha and beta (TOP2A and TOP2B) isoenzymes perform essential and non-redundant cellular functions. Anthracyclines induce their potent anti-cancer effects primarily via TOP2A, but at the same time they induce a dose limiting cardiotoxicity through TOP2B. Here we describe the development of the obex class of TOP2 inhibitors that bind to a previously unidentified druggable pocket in the TOP2 ATPase domain to act as allosteric catalytic inhibitors by locking the ATPase domain conformation with the capability of isoform-selective inhibition. Through rational drug design we have developed topobexin, which interacts with residues that differ between TOP2A and TOP2B to provide inhibition that is both selective for TOP2B and superior to dexrazoxane. Topobexin is a potent protectant against chronic anthracycline cardiotoxicity in an animal model. This demonstration of TOP2 isoform-specific inhibition underscores the broader potential to improve drug specificity and minimize adverse effects in various medical treatments.

• MeSH
• Anthracyclines * adverse effects   pharmacology   MeSH
• DNA Topoisomerases, Type II * metabolism   chemistry   MeSH
• Topoisomerase II Inhibitors * pharmacology   chemistry   MeSH
• Cardiotonic Agents * pharmacology   chemistry   MeSH
• Cardiotoxicity * prevention & control   MeSH
• Humans MeSH
• Mice MeSH
• Poly-ADP-Ribose Binding Proteins antagonists & inhibitors   metabolism   chemistry   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anthracyclines * MeSH
• DNA Topoisomerases, Type II * MeSH
• Topoisomerase II Inhibitors * MeSH
• Cardiotonic Agents * MeSH
• Poly-ADP-Ribose Binding Proteins MeSH
• TOP2A protein, human MeSH Browser
• TOP2B protein, human MeSH Browser

Anthracyclines, such as doxorubicin (adriamycin), daunorubicin, or epirubicin, rank among the most effective agents in classical anticancer chemotherapy. However, cardiotoxicity remains the main limitation of their clinical use. Topoisomerase IIβ has recently been identified as a plausible target of anthracyclines in cardiomyocytes. We examined the putative topoisomerase IIβ selective agent XK469 as a potential cardioprotective and designed several new analogs. In our experiments, XK469 inhibited both topoisomerase isoforms (α and β) and did not induce topoisomerase II covalent complexes in isolated cardiomyocytes and HL-60, but induced proteasomal degradation of topoisomerase II in these cell types. The cardioprotective potential of XK469 was studied on rat neonatal cardiomyocytes, where dexrazoxane (ICRF-187), the only clinically approved cardioprotective, was effective. Initially, XK469 prevented daunorubicin-induced toxicity and p53 phosphorylation in cardiomyocytes. However, it only partially prevented the phosphorylation of H2AX and did not affect DNA damage measured by Comet Assay. It also did not compromise the daunorubicin antiproliferative effect in HL-60 leukemic cells. When administered to rabbits to evaluate its cardioprotective potential in vivo, XK469 failed to prevent the daunorubicin-induced cardiac toxicity in either acute or chronic settings. In the following in vitro analysis, we found that prolonged and continuous exposure of rat neonatal cardiomyocytes to XK469 led to significant toxicity. In conclusion, this study provides important evidence on the effects of XK469 and its combination with daunorubicin in clinically relevant doses in cardiomyocytes. Despite its promising characteristics, long-term treatments and in vivo experiments have not confirmed its cardioprotective potential.

• Keywords
• XK469, anthracyclines, cardiotoxicity, dexrazoxane, topoisomerase II,
• MeSH
• Anthracyclines * toxicity   therapeutic use   MeSH
• Quinoxalines * MeSH
• Daunorubicin toxicity   therapeutic use   MeSH
• DNA Topoisomerases, Type II metabolism   therapeutic use   MeSH
• Doxorubicin toxicity   MeSH
• Topoisomerase II Inhibitors * toxicity   therapeutic use   MeSH
• Cardiotoxicity MeSH
• Rabbits MeSH
• Rats MeSH
• DNA Damage MeSH
• Antibiotics, Antineoplastic toxicity   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anthracyclines * MeSH
• Quinoxalines * MeSH
• Daunorubicin MeSH
• DNA Topoisomerases, Type II MeSH
• Doxorubicin MeSH
• Topoisomerase II Inhibitors * MeSH
• Antibiotics, Antineoplastic MeSH
• XK 469 MeSH Browser

The bisdioxopiperazine topoisomerase IIβ inhibitor ICRF-193 has been previously identified as a more potent analog of dexrazoxane (ICRF-187), a drug used in clinical practice against anthracycline cardiotoxicity. However, the poor aqueous solubility of ICRF-193 has precluded its further in vivo development as a cardioprotective agent. To overcome this issue, water-soluble prodrugs of ICRF-193 were prepared, their abilities to release ICRF-193 were investigated using a novel UHPLC-MS/MS assay, and their cytoprotective effects against anthracycline cardiotoxicity were tested in vitro in neonatal ventricular cardiomyocytes (NVCMs). Based on the obtained results, the bis(2-aminoacetoxymethyl)-type prodrug GK-667 was selected for advanced investigations due to its straightforward synthesis, sufficient solubility, low cytotoxicity and favorable ICRF-193 release. Upon administration of GK-667 to NVCMs, the released ICRF-193 penetrated well into the cells, reached sufficient intracellular concentrations and provided effective cytoprotection against anthracycline toxicity. The pharmacokinetics of the prodrug, ICRF-193 and its rings-opened metabolite was estimated in vivo after administration of GK-667 to rabbits. The plasma concentrations of ICRF-193 reached were found to be adequate to achieve cardioprotective effects in vivo. Hence, GK-667 was demonstrated to be a pharmaceutically acceptable prodrug of ICRF-193 and a promising drug candidate for further evaluation as a potential cardioprotectant against chronic anthracycline toxicity.

• MeSH
• Anthracyclines adverse effects   MeSH
• Dexrazoxane chemistry   pharmacology   MeSH
• Diketopiperazines chemistry   pharmacology   MeSH
• DNA Topoisomerases, Type II metabolism   MeSH
• Topoisomerase II Inhibitors chemistry   pharmacology   MeSH
• Myocytes, Cardiac drug effects   metabolism   MeSH
• Cardiotonic Agents chemistry   pharmacology   MeSH
• Cardiotoxicity drug therapy   metabolism   MeSH
• Rabbits MeSH
• Piperazine chemistry   pharmacology   MeSH
• Prodrugs chemistry   pharmacology   MeSH
• Razoxane chemistry   pharmacology   MeSH
• Water chemistry   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione MeSH Browser
• Anthracyclines MeSH
• Dexrazoxane MeSH
• Diketopiperazines MeSH
• DNA Topoisomerases, Type II MeSH
• Topoisomerase II Inhibitors MeSH
• Cardiotonic Agents MeSH
• Piperazine MeSH
• Prodrugs MeSH
• Razoxane MeSH
• Water MeSH

Modern diagnostic strategies for early recognition of cancer therapeutics-related cardiac dysfunction involve cardiac troponins measurement. Still, the role of other markers of cardiotoxicity is still unclear. The present study was designed to investigate dynamics of response of human cardiomyocytes derived from induced pluripotent stem cells (hiPCS-CMs) to doxorubicin with the special emphasis on their morphological changes in relation to expression and organization of troponins. The hiPCS-CMs were treated with doxorubicin concentrations (1 and 0.3 µM) for 48 h and followed for next up to 6 days. Exposure of hiPCS-CMs to 1 µM doxorubicininduced suppression of both cardiac troponin T (cTnT) and cardiac troponin I (cTnI) gene expression. Conversely, lower 0.3 µM doxorubicin concentration produced no significant changes in the expression of aforementioned genes. However, the intracellular topography, arrangement, and abundance of cardiac troponin proteins markedly changed after both doxorubicin concentrations. In particular, at 48 h of treatment, both cTnT and cTnI bundles started to reorganize, with some of them forming compacted shapes extending outwards and protruding outside the cells. At later intervals (72 h and onwards), the whole troponin network collapsed and became highly disorganized following, to some degree, overall changes in the cellular shape. Moreover, membrane permeability of cardiomyocytes was increased, and intracellular mitochondrial network rearranged and hypofunctional. Together, our results demonstrate complex effects of clinically relevant doxorubicin concentrations on hiPCS-CM cells including changes in cTnT and cTnI, but also in other cellular compartments contributing to the overall cytotoxicity of this class of cytostatics.

• Keywords
• cardiotoxicity, doxorubicin, hiPCS-CMs, mitochondria, morphology, troponins,
• MeSH
• Cell Line MeSH
• Doxorubicin pharmacology   toxicity   MeSH
• Induced Pluripotent Stem Cells cytology   drug effects   MeSH
• Myocytes, Cardiac cytology   drug effects   metabolism   MeSH
• Cardiotoxicity MeSH
• Humans MeSH
• Antineoplastic Agents pharmacology   toxicity   MeSH
• Troponin metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Doxorubicin MeSH
• Antineoplastic Agents MeSH
• Troponin MeSH

Chronic anthracycline cardiotoxicity is a serious clinical issue with well characterized functional and histopathological hallmarks. However, molecular determinants of the toxic damage and associated myocardial remodeling remain to be established. Furthermore, details on the different propensity of the left and right ventricle (LV and RV, respectively) to the cardiotoxicity development are unknown. Hence, the aim of the investigation was to study molecular changes associated with remodeling of the LV and RV in chronic anthracycline cardiotoxicity and post-treatment follow up. The cardiotoxicity was induced in rabbits with daunorubicin (3 mg/kg/week for 10 weeks) and animals were sacrificed either at the end of the treatment or after an additional 10 weeks. Daunorubicin induced severe and irreversible cardiotoxicity associated with LV dysfunction and typical morphological alterations, whereas the myocardium of the RV showed only mild changes. Both ventricles also showed different expression of ANP after daunorubicin treatment. Daunorubicin impaired the expression of several sarcomeric proteins in the LV, which was not the case of the RV. In particular, a significant drop was found in titin and thick filament proteins at both mRNA and protein level and this might be connected with persistent LV down-regulation of GATA-4. In addition, the LV was more affected by treatment-induced perturbations in calcium handling proteins. LV cardiomyocytes showed marked up-regulation of desmin after the treatment and vimentin was mainly induced in LV fibroblasts, whereas only weaker changes were observed in the RV. Remodeling of extracellular matrix was almost exclusively found in the LV with particular induction of collagen I and IV. Hence, the present study describes profound molecular remodeling of myocytes, non-myocyte cells and extracellular matrix in response to chronic anthracycline treatment with marked asymmetry between LV and RV.

• MeSH
• Anthracyclines toxicity   MeSH
• Daunorubicin pharmacology   MeSH
• Echocardiography MeSH
• Immunohistochemistry MeSH
• Intermediate Filaments metabolism   MeSH
• Rabbits MeSH
• Real-Time Polymerase Chain Reaction MeSH
• Myocardium metabolism   MeSH
• Ventricular Remodeling drug effects   physiology   MeSH
• Transcription Factors metabolism   MeSH
• Troponin T metabolism   MeSH
• Blotting, Western MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anthracyclines MeSH
• Daunorubicin MeSH
• Transcription Factors MeSH
• Troponin T MeSH

SIGNIFICANCE: Anthracyclines (doxorubicin, daunorubicin, or epirubicin) rank among the most effective anticancer drugs, but their clinical usefulness is hampered by the risk of cardiotoxicity. The most feared are the chronic forms of cardiotoxicity, characterized by irreversible cardiac damage and congestive heart failure. Although the pathogenesis of anthracycline cardiotoxicity seems to be complex, the pivotal role has been traditionally attributed to the iron-mediated formation of reactive oxygen species (ROS). In clinics, the bisdioxopiperazine agent dexrazoxane (ICRF-187) reduces the risk of anthracycline cardiotoxicity without a significant effect on response to chemotherapy. The prevailing concept describes dexrazoxane as a prodrug undergoing bioactivation to an iron-chelating agent ADR-925, which may inhibit anthracycline-induced ROS formation and oxidative damage to cardiomyocytes. RECENT ADVANCES: A considerable body of evidence points to mitochondria as the key targets for anthracycline cardiotoxicity, and therefore it could be also crucial for effective cardioprotection. Numerous antioxidants and several iron chelators have been tested in vitro and in vivo with variable outcomes. None of these compounds have matched or even surpassed the effectiveness of dexrazoxane in chronic anthracycline cardiotoxicity settings, despite being stronger chelators and/or antioxidants. CRITICAL ISSUES: The interpretation of many findings is complicated by the heterogeneity of experimental models and frequent employment of acute high-dose treatments with limited translatability to clinical practice. FUTURE DIRECTIONS: Dexrazoxane may be the key to the enigma of anthracycline cardiotoxicity, and therefore it warrants further investigation, including the search for alternative/complementary modes of cardioprotective action beyond simple iron chelation.

• MeSH
• Antioxidants chemistry   pharmacology   MeSH
• Anthracyclines adverse effects   chemistry   pharmacology   MeSH
• Chelating Agents adverse effects   chemistry   pharmacology   MeSH
• Cardiotonic Agents adverse effects   chemistry   pharmacology   MeSH
• Metals adverse effects   MeSH
• Humans MeSH
• Myocardium metabolism   MeSH
• Oxidation-Reduction MeSH
• Oxidative Stress * MeSH
• Antineoplastic Agents adverse effects   chemistry   pharmacology   MeSH
• Razoxane adverse effects   chemistry   pharmacology   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Signal Transduction * MeSH
• Heart drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Antioxidants MeSH
• Anthracyclines MeSH
• Chelating Agents MeSH
• Cardiotonic Agents MeSH
• Metals MeSH
• Antineoplastic Agents MeSH
• Razoxane MeSH
• Reactive Oxygen Species MeSH

BACKGROUND: Dexrazoxane (DEX, ICRF-187) is the only clinically approved cardioprotectant against anthracycline cardiotoxicity. It has been traditionally postulated to undergo hydrolysis to iron-chelating agent ADR-925 and to prevent anthracycline-induced oxidative stress, progressive cardiomyocyte degeneration and subsequent non-programmed cell death. However, the additional capability of DEX to protect cardiomyocytes from apoptosis has remained unsubstantiated under clinically relevant in vivo conditions. METHODS: Chronic anthracycline cardiotoxicity was induced in rabbits by repeated daunorubicin (DAU) administrations (3 mg kg(-1) weekly for 10 weeks). Cardiomyocyte apoptosis was evaluated using TUNEL (terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling) assay and activities of caspases 3/7, 8, 9 and 12. Lipoperoxidation was assayed using HPLC determination of myocardial malondialdehyde and 4-hydroxynonenal immunodetection. RESULTS: Dexrazoxane (60 mg kg(-1)) co-treatment was capable of overcoming DAU-induced mortality, left ventricular dysfunction, profound structural damage of the myocardium and release of cardiac troponin T and I to circulation. Moreover, for the first time, it has been shown that DEX affords significant and nearly complete cardioprotection against anthracycline-induced apoptosis in vivo and effectively suppresses the complex apoptotic signalling triggered by DAU. In individual animals, the severity of apoptotic parameters significantly correlated with cardiac function. However, this effective cardioprotection occurred without a significant decrease in anthracycline-induced lipoperoxidation. CONCLUSION: This study identifies inhibition of apoptosis as an important target for effective cardioprotection against chronic anthracycline cardiotoxicity and suggests that lipoperoxidation-independent mechanisms are involved in the cardioprotective action of DEX.

• MeSH
• Anthracyclines antagonists & inhibitors   toxicity   MeSH
• Apoptosis drug effects   MeSH
• Myocytes, Cardiac cytology   drug effects   MeSH
• Cardiotonic Agents pharmacology   MeSH
• Cardiotoxins antagonists & inhibitors   toxicity   MeSH
• Rabbits MeSH
• Heart Diseases chemically induced   pathology   prevention & control   MeSH
• Razoxane pharmacology   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anthracyclines MeSH
• Cardiotonic Agents MeSH
• Cardiotoxins MeSH
• Razoxane MeSH