Evidence of the selective alteration of anthracycline activity due to modulation by ICRF-187 (ADR-529)

Effects of Repeated Administration of Dithiol Chelating Agent - Sodium 2,3-Dimercapto-1-propanesulphonate (DMPS) - On Biochemical and Haematological Parameters in Rabbits

The effects of weekly intravenously administered a dithiol chelating agent - sodium 2,3-dimercaptopropanesulphonate (DMPS) - in a single dose of 50 mg/kg/week for 10 weeks on biochemical and haematological parameters were studied in rabbits. DMPS was well tolerated, an increase in body weight was similar in the DMPS-treated and control animals. DMPS caused significant decrease in plasma calcium and vitamin E concentrations at the end of the experiment. No significant differences in haematological parameters between the DMPS and control groups were observed. A significant decrease in magnesium content in myocardial tissue was observed in the DMPS-treated rabbits. The above-mentioned biochemical changes should be taken into account in studies of possible chelating and radical scavenging effects of DMPS in various pathological conditions.

Multicenter randomized phase III study of the cardioprotective effect of dexrazoxane (Cardioxane®) in advanced/metastatic breast cancer patients treated with anthracycline-based chemotherapy

BACKGROUND

Anthracycline-induced cardiotoxicity has led to the adoption of empirical dose limits that may restrict continued use of anthracyclines among patients who might benefit. Dexrazoxane, a cardioprotective agent, has been shown to reduce the risk of anthracycline-associated cardiotoxicity when given from first dose of anthracycline. This study sought to confirm the benefit of dexrazoxane in patients at high risk of cardiotoxicity due to prior anthracycline use.

PATIENTS AND METHODS

A total of 164 female breast cancer patients, previously treated with anthracyclines, received anthracycline-based chemotherapy either with (n = 85) or without (n = 79) dexrazoxane for a maximum of six cycles.

RESULTS

Compared with those receiving anthracycline alone, patients treated with dexrazoxane experienced significantly fewer cardiac events (39% versus 13%, P < 0.001) and a lower and less severe incidence of congestive heart failure (11% versus 1%, P < 0.05). Tumor response rate was unaffected by dexrazoxane therapy. The frequency of adverse events was similar between groups and there were no significant between-group differences in the number of dose modifications/interruptions.

CONCLUSION

Dexrazoxane significantly reduced the occurrence and severity of anthracycline-induced cardiotoxicity in patients at increased risk of cardiac dysfunction due to previous anthracycline treatment without compromising the antitumor efficacy of the chemotherapeutic regimen.

Desferal inhibits breast tumor growth and does not interfere with the tumoricidal activity of doxorubicin

Desferal is a clinically approved iron chelator used to treat iron overload. Doxorubicin is an anthracycline cancer chemotherapy drug used in the treatment of breast cancer. It can undergo redox cycling in the presence of iron to produce reactive oxygen species. The oxidant-generating activity of doxorubicin is thought to be responsible for the cardiotoxic side effects of the drug, but it is unclear whether it is also required for its anti-tumor activity. To test whether an iron-chelating antioxidant would interfere with the tumor-killing activity of doxorubicin, nude mice were transplanted with xenografts of human breast cancer MDA-MB 231 cells and then treated with doxorubicin and/or desferal. Not only did desferal not interfere with the anti-tumor activity of doxorubicin, it inhibited tumor growth on its own. In vitro studies confirmed that desferal inhibits breast tumor growth. However, it did not induce apoptosis, nor did it induce cell cycle arrest. Instead, desferal caused cytostasis, apparently through iron depletion. The cytostatic activity of desferal was partially ameliorated by pretreatment with iron-saturated transferrin, and transferrin receptor expression on breast cancer cells nearly doubled after exposure to desferal. In contrast to its effect on tumor cells, desferal did not inhibit growth of normal breast epithelial cells. The data indicate that the anti-tumor activity of doxorubicin is not dependent on iron-mediated ROS production. Furthermore, desferal may have utility as an adjunctive chemotherapy due to its ability to inhibit breast tumor growth and cardiotoxic side effects without compromising the tumor-killing activity of an anthracycline chemotherapy drug.

Antarth, a polyherbal preparation protects against the doxorubicin-induced toxicity without compromising its Antineoplastic activity

Doxorubicin (DOX), an anthracycline drug widely used for the treatment of various cancers, causes a cumulative dose-dependent cardiotoxicity that is characterized by an irreversible dilated cardiomyopathy and congestive heart failure. Antarth (ANT) a polyherbal preparation was evaluated for its cardioprotective properties against doxorubicin-induced cardiotoxicity in mice. Mice were treated with 25 mg/kg ANT orally once daily for 5 consecutive days before a single intraperitoneal injection of 15 mg/kg doxorubicin. The animals were killed 30 h after DOX treatment. DOX induced a significant elevation in the serum levels of glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), creatine kinase (CK-MB) and lactate dehydrogenase (LDH), indicating its acute cardiotoxicity. The treatment of mice with ANT before DOX administration significantly reduced the serum levels of GPT, GOT, CK-MB and LDH indicating that ANT protected against the DOX-induced cardiotoxicity. Pretreatment of mice with 25 mg/kg ANT inhibited the DOX-induced decline in the antioxidant status. Intraperitoneal injection of 1.25 mg/kg DOX once daily for 9 consecutive days significantly improved the survival of mice bearing Ehrlich ascites carcinoma (EAC). Treatment of EAC with 25 mg/kg ANT alone did not affect the anticancer activity of DOX since ANT did not alter the tumor cell growth, the median survival time and average survival time of tumor bearing mice. The present study demonstrates that ANT protects mice against DOX-induced cardiotoxicity, without compromising the antineoplastic activity of DOX.

A comparative study between catalase gene therapy and the cardioprotector monohydroxyethylrutoside (MonoHER) in protecting against doxorubicin-induced cardiotoxicity in vitro

Cardiotoxicity is the main dose-limiting side effect of doxorubicin in the clinic. Being a free radical producer, doxorubicin affects the heart specifically because of its low antioxidant capacity. Among those antioxidants, catalase is present in very low levels in the heart compared to other organs. Since catalase is an essential enzyme in detoxifying hydrogen peroxide, the aim of the present study was to investigate the protective effect of catalase as delivered by an adenovirus vector against doxorubicin-induced cardiotoxicity in cultured neonatal rat cardiac myocytes (NeRCaMs). 7-Monohydroxyethylrutoside (MonoHER), a potent cardioprotector currently under clinical investigations, was included in the study as a reference. Neonatal rat cardiac myocytes were infected with different multiplicity of infections (MOIs) of adenovirus encoding catalase (AdCat). A control infection with an adenovirus vector encoding a nonrelated protein was included. The activity and content of catalase in infected cells were determined during 3 days postinfection. One group of NeRCaMs was infected with AdCat before treatment with doxorubicin (0–50 μM). The second and third group were treated with doxorubicin (0–50 μM) with and without 1 mM monohydroxyethylrutoside (monoHER), respectively. The LDH release and viability of treated cells were measured 24 and 48 h after doxorubicin treatment. The beating rate was followed in three other groups of cells receiving the same treatments within 3 days after doxorubicin (0–100 μM) treatment. Catalase activity increased in AdCat-infected cells, with different MOIs, starting from the second day after infection as compared to the mock-infected cells (P<0.03). At the third day of infection, an MOI of more than 50 caused cytopathic effects, which hampered the use of higher viral titres. With an MOI of 50, catalase activity increased 3.5-fold in AdCat-infected cells 3 days postinfection (P=0.021) compared to mock-infected cells. The beating rate and survival of NeRCaMs decreased in a concentration and time-dependent manner after doxorubicin treatment (P<0.0005). This cytotoxicity was associated with an increase in the LDH release from the treated cells (P<0.0005). The cells stopped beating 24 h after treatment with >50 μM doxorubicin. A 3.5-fold increase in the activity of catalase did not protect NeRCaMs against any of the cytotoxic effects of doxorubicin on NeRCaMs. In contrast, monoHER (1 mM) significantly protected NeRCaMs against the lethal effects of doxorubicin on the survival, LDH release and the beating rate of NeRCaMs (P<0.004) during 48 h after doxorubicin treatment. This protection resulted in a prolongation of the beating of doxorubicin-treated cells after the end of the experiment (i.e. >72 h). The present study (1) illustrates that the cytotoxicity of high MOI of AdCat (>50) limited the possibility to increase catalase activity more than 3.5-fold, which was not enough to protect infected NeRCaMs against doxorubicin-induced cardiotoxicity and (2) confirms the efficacy of monoHER as a cardioprotector. Thus, the use of monoHER proves more suitable for the prevention of doxorubicin-induced cardiotoxicity than catalase gene transfer employing adenovirus vectors.

The protective effect of cardiac gene transfer of CuZn-sod in comparison with the cardioprotector monohydroxyethylrutoside against doxorubicin-induced cardiotoxicity in cultured cells

Doxorubicin-induced cardiotoxicity is related to its production of free radicals that specifically affect heart tissue because of its low antioxidant status. Monohydroxyethylrutoside (monoHER), a potent antioxidant flavonoid, is under development as a protector against doxorubicin-induced cardiotoxicity. The overexpression of high levels of superoxide dismutase (sod) protects against free radical damage in transgenic mice. Seeking alternatives besides the few cardioprotectors that are presently under investigation, the aim of the present study was to investigate the protective effect of cardiac gene transfer of CuZn-sod compared with that of the presently most promising cardioprotector monoHER against doxorubicin-induced cardiotoxic effects on neonatal rat cardiac myocytes (NeRCaMs) in vitro. NeRCaMs were infected with different multiplicity of infections (MOIs) of adenovirus encoding CuZn-sod (AdCuZn-sod). A control infection with an adenovirus vector encoding a nonrelated protein was included. The overexpression of CuZn-sod was characterized within 3 days postinfection. For doxorubicin treatment, NeRCaMs were divided into three groups. The first group was infected with AdCuZn-sod before treatment with doxorubicin (0-50 microM). The second and third groups were treated with doxorubicin (0-50 microM) alone and with 1 mM monoHER, respectively. The LDH release and survival of treated cells were measured 24 and 48 hours after doxorubicin treatment. The beating rate was followed during the 3 days after doxorubicin (0-100 microM) treatment. At the third day after infection with an MOI of 25 plaque-forming unit (PFU) of AdCuZn-sod/cell, the activity of CuZn-sod significantly increased (five-fold, P=.029). Higher MOI produced cytopathic effects (CPEs). Doxorubicin alone produced significant concentration- and time-dependent reduction in NeRCaMs beating rate and survival (P < .0005). Doxorubicin (> or =50 microM)-treated cells ceased to beat after 24 hours. This cytotoxicity was associated with an increase in the LDH release from the treated cells (P <.0005). The five-fold increase in the activity of CuZn-sod did not protect against any of the cytotoxic effects of doxorubicin on NeRCaMs. In contrast, monoHER (1 mM) protected against the lethal effects of doxorubicin on the survival, LDH release and the beating rate of NeRCaMs (P <.004) during 48 hours after doxorubicin treatment. Doxorubicin-treated (< or =100 microM) cells continued beating for >72 hours in the presence of monoHER. The present study showed the lack of adenoviral CuZn-sod gene-transfer to protect myocardiocytes against doxorubicin-induced toxicity and confirms the efficacy of monoHER cardioprotection. Thus, a gene-therapy strategy involving overexpression of CuZn-sod to protect against doxorubicin-induced cardiotoxicity is not feasible with the currently available adenovirus vectors.

Catalytic inhibitors of DNA topoisomerase II

Catalytic inhibitors of mammalian DNA topoisomerase II have been found recently in natural and synthetic compounds. These compounds target the enzyme within the cell and inhibit various genetic processes involving the enzyme, such as DNA replication and chromosome dynamics, and thus proved to be good probes for the functional analyses of the enzyme in a variety of eukaryotes from yeast to mammals. Catalytic inhibitors were shown to be antagonists against topoisomerase II poisons. Thus bis(2,6-dioxopiperazines) have a potential to overcome cardiac toxicity caused by potent antitumor anthracycline antibiotics such as doxorubicin and daunorubicin. ICRF-187, a (+)-enantiomer of racemic ICRF-159, has been used in clinics in European countries as cardioprotector. Furthermore, bis(2,6-dioxopiperazines) enhance the efficacy of topoisomerase II poisons by reducing their side effects in preclinical and clinical settings. Bis(2,6-dioxopiperazines) per se among others have antitumor activity, and one of their derivatives, MST-16 or Sobuzoxane, bis(N1-isobutyloxycarbonyloxymethyl-2, 6-dioxopiperazine), has been developed in Japan as an anticancer drug used for malignant lymphomas and adult T-cell leukemia in clinics.

Bis(2,6-dioxopiperazines), catalytic inhibitors of DNA topoisomerase II, as molecular probes, cardioprotectors and antitumor drugs

Bis(2,6-dioxopiperazines) and other catalytic inhibitors of mammalian DNA topoisomerase II have recently been found in natural and synthetic compounds. These compounds target the enzyme within the cell and inhibit various genetic processes involving the enzyme such as DNA replication and chromosome dynamics and thus proved to be good probes for the functional analyses of the enzyme in a variety of eucaryotes from yeast to mammals. Catalytic inhibitors were shown to be antagonists against topoisomerase II poisons under some conditions, but to be synergistic under others. Bis(2,6-dioxopiperazines) have a potential to overcome cardiac toxicity caused by potent antitumor anthracycline antibiotics such as doxorubicin and daunorubicin. ICRF-187, +enantiomer of racemic ICRF-159, has been used in EU countries as cardioprotector in cancer clinics. Furthermore, bis(2,6-dioxopiperazines) enhance the efficacy of antitumor topoisomerase II poisons, e.g. anthracycline antibiotics such as daunorubicin and doxorubicin, by reducing their side effects and by allowing dose escalation of the antitumor drugs in preclinical and clinical settings. Besides bis(2,6-dioxopiperazines) per se having antitumor activity, and one of their derivatives, MST-16 or sobuzoxane, bis(N1-isobutyloxycarbonyloxymethyl-2,6-dioxopiperazine), has been developed in Japan and used in clinics as anticancer drug for malignant lymphomas and adult T-cell leukemia (ATL). Further developments of bis(2,6-dioxopiperazines) as antimetastatic agents are expected.

Anthracyclines in haematology: preclinical studies, toxicity and delivery systems

The anthracyclines are widely used in the treatment of haematological and non-haematological malignancy and there is now more than 30 years' clinical experience with these agents but despite this, their mechanism of action is incompletely understood. The anthracyclines have been shown to intercalate with DNA and indirectly inhibit the activity of the enzyme topoisomerase II, resulting in DNA strand breaks. More recently, workers have focused on induction of apoptosis and have shown that daunorubicin stimulates production of the apoptotic mediator, ceramide and that the activity of doxorubicin can be blocked by inhibitors of CD95 (fas). One of the major problems with anthracycline therapy is the development of resistance which may be mediated by p-glycoprotein or by other mechanisms. Much recent research has concentrated on methods to modulate the drug-resistant phenotype and these include development of new analogues and use of specific reversal agents. The toxicity profile of the anthracyclines includes bone marrow suppression, severe local reaction following extravasation, radiation recall, alopecia, gastrointestinal and hepatic effects, development of secondary malignancies and significant cardiac toxicity. The risk factors for the development of anthracycline-related cardiac toxicity are well documented and several methods have been exploited in attempts at prevention. Finally, a number of drug delivery systems have been developed in order to improve therapeutic response and reduce toxicity to normal tissues, including the use of liposomal preparations.

Monohydroxyethylrutoside as protector against chronic doxorubicin-induced cardiotoxicity

1. The clinical use of the antitumour agent, doxorubicin, is largely limited by the development of a cumulative dose-related cardiotoxicity. This toxicity is generally believed to be caused by the formation of oxygen free radicals. In earlier studies it was established that flavonoids, naturally occurring antioxidants, can provide some degree of protection. In this study we investigated whether 7-monohydroxyethylrutoside (monoHER), a powerful antioxidative flavonoid with extremely low toxicity, can provide protection to an extent comparable to the clinically successful Cardioxane (ICRF-187). 2. Balb/c mice of 20-25 g were equipped i.p. with a telemeter to measure ECG. They were given 6 i.v. doses of doxorubicin (4 mg kg-1) at weekly intervals. ICRF-187 (50 mg kg-1) or monoHER (500 mg kg-1) were administered i.p. 1 h before doxorubicin administration. In the 2 monoHER groups the treatment continued with either 1 or 4 additional injections per week. A saline and monoHER treated group served as controls. After these 6 weeks, they were observed for another 2 weeks. 3. At the end of this study (week 8) the ST interval had increased by 16.7 +/- 2.7 ms (mean +/- s.e. mean) in doxorubicin-treated mice. At that time, the ST interval had increased by only 1.8 +/- 0.9 ms in ICRF-187 co-mediated mice and in monoHER co-medicated mice by only 1.7 +/- 0.8 and 5.1 +/- 1.7 ms (5- and 2-day schedule, respectively, all P < 0.001 relative to doxorubicin and not significantly different from control). The ECG of the control animals did not change during the entire study. The QRS complex did not change in either group.4. It can be concluded that monoHER protects against doxorubicin-induced cardiotoxicity and merits further evaluation in this respect.

Modulation of the in vitro cardiotoxicity of doxorubicin by flavonoids

Cancer therapy with the anthracycline doxorubicin (Dox) is limited by cardiomyopathy, which develops in animals and patients after cumulative dosing. Generation of free radicals by Dox may be involved in this cardiotoxicity. Dox binds strongly to metal ions, especially iron(III). This Dox-metal complex stimulates the generation of free radicals through self-reduction of the complex. We investigated the possibility of inhibiting Dox-induced cardiotoxicity by scavenging of free radicals and/or chelating metal ions. The effects of Dox, both alone and in combination with iron-chelating agents, were studied on inotropy of the isolated mouse left atrium, lipid peroxidation (LPO) in cardiac microsomal membranes, ferricytochrome c (cyt.c3+) reduction, and oxygen consumption. The flavonoids 7-monohydroxyethylrutoside (mono-HER) and 7,3',4'-trihydroxyethylrutoside (tri-HER) and the ethylenediaminetetraacetic acid (EDTA) analogue ICRF-198 and its precursor ICRF-187 were used as iron-chelating agents. The latter were used for comparison since ICRF-187 has been reported to inhibit the cardiotoxic effects of Dox both in vitro and in vivo. Only the flavonoids could inhibit the negative inotropic effect of Dox (35 microM) on the mouse left atrium; in the presence of tri-HER (500 microM) the beating force decreased by 18% instead of 50%, whereas mono-HER completely prevented the Dox-induced negative inotropic effect. ICRF-198 and both flavonoids (500 microM) completely inhibited Dox (35 microM)-induced LPO, whereas ICRF-187 provided 65% inhibition. The observation that both cyt.c3+ reduction and oxygen consumption induced by the Dox-iron(III) complex (50/16.6 microM Dox3Fe3+) could be inhibited by superoxide dismutase proved the involvement of superoxide anions (O2-.). The iron-chelating agents (50 microM) inhibited cyt.c3+ reduction by 91% (mono-HER), 43% (tri-HER), and 100% (ICRF-198). Only mono-HER and ICRF-198 (50 microM) were capable of inhibiting the oxygen consumption by 70% and 43%, respectively. It is concluded that flavonoids offer a good perspective for further studies on the prevention of Dox-induced cardiomyopathy.

Anthracyclines and the heart

Images

Antagonistic effect of the cardioprotector (+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane (ICRF-187) on DNA breaks and cytotoxicity induced by the topoisomerase II directed drugs daunorubicin and etoposide (VP-16)

The effect of the bisdioxopiperazine cardioprotector ICRF-187 (ADR-529, dexrazoxan) on drug-induced DNA damage and cytotoxicity was studied. Using alkaline elution assays, ICRF-187 in a dose-dependent manner inhibited the formation of DNA single strand breaks (SSBs) as well as DNA-protein cross-links induced by drugs such as VP-16 (etoposide), m-AMSA [4'-(9-acridinylamino)-methanesulfon-m-anisidide], daunorubicin and doxorubicin (Adriamycin) which are known to stimulate DNA-topoisomerase II cleavable complex formation. Thus, 50% inhibition of DNA SSBs induced by 5 microM doxorubicin occurred already at equimolar ICRF-187. In contrast, ICRF-187 did not affect DNA SSBs induced by H2O2. In clonogenic assay, ICRF-187 in non-toxic doses antagonized both VP-16 and daunorubicin cytotoxicity in a dose-dependent manner. Our results indicate that the previously described acute in vivo protection by ICRF-187 against anthracycline toxicity may be due to inhibition of topoisomerase II activity. The antagonistic effect of ICRF-187 on daunorubicin cytotoxicity should be taken into consideration when planning clinical trials.