Dexrazoxane Protects against Myelosuppression from the DNA Cleavage–Enhancing Drugs Etoposide and Daunorubicin but not Doxorubicin

Exosome mimetics derived from bone marrow mesenchymal stem cells ablate neuroblastoma tumor in vitro and in vivo

PURPOSE

To develop exosome-mimetics derived from bone marrow mesenchymal stem cells (EM) as a novel nanoscale drug delivery system(nanoDDS) with improved tumor targeting activity, therapeutic effect, and biosafety, and to evaluate the therapeutic effect of doxorubicin loaded EM (EM-Dox) on neuroblastoma (NB) in vitro and in vivo.

METHODS

EM was prepared by serial extrusion of bone marrow mesenchymal stem cells (BMSCs), ammonium sulfate gradient method was used to promote the active loading of doxorubicin, and EM-Dox was obtained after removal of free doxorubicin by dialysis. The obtained EM and EM-Dox were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), Western Blot assay(WB), and the yield of exosomes and EM was further compared. Confocal fluorescent microscopy was used to verify the uptake of EM-Dox and free doxorubicin (Free-Dox) by NB cells. CCK-8 assay, cell cycle assay, and cell apoptosis assay were used to evaluate the antitumor effect of EM-Dox on NB cells in vitro. In addition, the targeted therapeutic effect and biosafety of EM-Dox against NB were evaluated in tumor-bearing nude mice.

RESULTS

TEM, NTA, and WB verified that both EM and EM-Dox feature highly similar morphology, size and marker protein expression in comparison with naturally occurred exosomes, but the particle size of EM-Dox increased slightly after loading doxorubicin. The protein yield and particle yield of EM-Dox were 16.8 and 26.3-folds higher than those of exosomes, respectively. Confocal fluorescent microscopy showed that EM and doxorubicin had a definite co-localization. EM-Dox was readily internalized in two well-established human NB cell lines. The intracellular content of doxorubicin in cells treated with EM-Dox was significantly higher than that treated with Free-Dox. CCK-8 assay and flow cytometry confirmed that EM-Dox could inhibit NB cell proliferation, induce G2/M phase cell cycle arrest, and promote NB cell apoptosis in vitro. In vivo bioluminescence imaging results demonstrated that EM-Dox effectively targets NB tumors in vivo. Compared with Free-Dox, EM-Dox had a significantly increased inhibitory effect against NB tumor proliferation and progression in vivo, without inducing any myocardial injury.

CONCLUSIONS

EM-Dox showed significantly increased anti-tumor activity in comparison with free doxorubicin in vitro and in vivo, and scalable EMs may represent a new class of NanoDDS that can potentially replace naturally occurred exosomes in preclinical or clinical translations.

Adapalene and Doxorubicin Synergistically Promote Apoptosis of TNBC Cells by Hyperactivation of the ERK1/2 Pathway Through ROS Induction

Doxorubicin is a commonly used chemotherapeutic agent to treat several malignancies, including aggressive tumors like triple-negative breast cancer. It has a limited therapeutic index owing to its extreme toxicity and the emergence of drug resistance. As a result, there is a pressing need to find innovative drugs that enhance the effectiveness of doxorubicin while minimizing its toxicity. The rationale of the present study is that combining emerging treatment agents or repurposed pharmaceuticals with doxorubicin might increase susceptibility to therapeutics and the subsequent establishment of improved pharmacological combinations for treating triple-negative breast cancer. Additionally, combined treatment will facilitate dosage reduction, reducing the toxicity associated with doxorubicin. Recently, the third-generation retinoid adapalene was reported as an effective anticancer agent in several malignancies. This study aimed to determine the anticancer activity of adapalene in TNBC cells and its effectiveness in combination with doxorubicin, and the mechanistic pathways in inhibiting tumorigenicity. Adapalene inhibits tumor cell growth and proliferation and acts synergistically with doxorubicin in inhibiting growth, colony formation, and migration of TNBC cells. Also, the combination of adapalene and doxorubicin enhanced the accumulation of reactive oxygen species triggering hyperphosphorylation of Erk1/2 and caspase-dependent apoptosis. Our results demonstrate that adapalene is a promising antitumor agent that may be used as a single agent or combined with present therapeutic regimens for TNBC treatment.

Identification of new halogen-containing 2,4-diphenyl indenopyridin-5-one derivative as a boosting agent for the anticancer responses of clinically available topoisomerase inhibitors

Based on previous reports on the significance of halogen moieties and the indenopyridin-5-one skeleton, we designed and synthesized a novel series of halogen (F-, Cl-, Br-, CF₃- and OCF₃-)-containing 2,4-diphenyl indenopyridin-5-ones and their corresponding -5-ols. Unlike indenopyridin-5-ols, most of the prepared indenopyridin-5-ones with Cl-, Br-, and CF₃- groups at the 2-phenyl ring conferred a strong dual topoisomerase I/IIα inhibitory effect. Among the series, para-bromophenyl substituted compound 9 exhibited the most potent topoisomerase inhibition and antiproliferative effects, which showed dependency upon the topoisomerase gene expression level of diverse cancer cells. In particular, as a DNA minor groove-binding non-intercalative topoisomerase I/IIα catalytic inhibitor, compound 9 synergistically promoted the anticancer efficacy of clinically applied topoisomerase I/IIα poisons both in vitro and in vivo, having the great advantage of alleviating poison-related toxicities.

Inhibition of Human Cervical Cancer Hela Cell Line by Meat-Derived Lactic Acid Bacteria of Lactobacillus plantarum IIA-1A5 and Lactobacillus acidophilus IIA-2B4

<b>Background and Objective:</b> Two Indonesian lactic acid bacteria of<i> L. plantarum </i>I IA-1A5 and <i>L. acidophilus </i>IIA-2B4 were previously isolated from beef with some functional probiotic properties. Nevertheless, the possibility of these strains to have anticancer activity remains unknown. Current study aimed to evaluate the inhibitory properties of intra-and extracellular protein extracts of these two strains against cervical cancer HeLa cells. <b>Materials and Methods:</b> The intracellular and extracellular proteins extract from <i>L. plantarum </i>IIA-1A5 and <i>L. acidophilus </i>IIA-2B4 were collected and designated as IP-LP, IP-LA, EP-LP and EP-LA, respectively. The effect of these extracts on the viability and morphology of HeLa cells were observed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and confocal microscopy, respectively. <b>Results:</b> Both IP-LP and IP-LA inhibited HeLa cells in a concentration-dependent manner, with IC<sub>50</sub> values of 352.62 and 120.97 μg mL<sup>1</sup>, respectively. Meanwhile, the inhibition activity was also observed for EP-LP and EP-LA, <i>albeit</i> very low. The inhibition effect was also confirmed by morphological analysis under confocal electron microscopy which showed the changes in the cell shapes and numbers. <b>Conclusion:</b> Altogether, for the first time this study proposed that the probiotic isolated from Indonesian beef are promising to inhibit cancer cell lines.

Extended release of perioperative immunotherapy prevents tumor recurrence and eliminates metastases

Cancer immunotherapy can confer durable benefit, but the percentage of patients who respond to this approach remains modest. The ability to concentrate immunostimulatory compounds at the site of disease can overcome local immune tolerance and reduce systemic toxicity. Surgical resection of tumors may improve the efficacy of immunotherapy by removing the concentrated immunosuppressive microenvironment; however, it also removes tumor-specific leukocytes as well as tumor antigens that may be important to establishing antitumor immunity. Moreover, surgery produces a transient immunosuppressive state associated with wound healing that has been correlated with increased metastasis. Using multiple models of spontaneous metastasis, we show that extended release of agonists of innate immunity-including agonists of Toll-like receptor 7/8 (TLR7/8) or stimulator of interferon genes (STING)-from a biodegradable hydrogel placed in the tumor resection site cured a much higher percentage of animals than systemic or local administration of the same therapy in solution. Depletion and neutralization experiments confirmed that the observed prevention of local tumor recurrence and eradication of existing metastases require both the innate and adaptive arms of the immune system. The localized therapy increased the numbers of activated natural killer (NK) cells, dendritic cells, and T cells and induced production of large amounts of type I interferons, thereby converting an immunosuppressive post-resection microenvironment into an immunostimulatory one. The results suggest that the perioperative setting may prove to be a useful context for immunotherapy, particularly when the release of the therapy is extended locally.

Ibudilast attenuates doxorubicin-induced cytotoxicity by suppressing formation of TRPC3 channel and NADPH oxidase 2 protein complexes

BACKGROUND AND PURPOSE

Doxorubicin is a highly effective anticancer agent but eventually induces cardiotoxicity associated with increased production of ROS. We previously reported that a pathological protein interaction between TRPC3 channels and NADPH oxidase 2 (Nox2) contributed to doxorubicin-induced cardiac atrophy in mice. Here we have investigated the effects of ibudilast, a drug already approved for clinical use and known to block doxorubicin-induced cytotoxicity, on the TRPC3-Nox2 complex. We specifically sought evidence that this drug attenuated doxorubicin-induced systemic tissue wasting in mice.

EXPERIMENTAL APPROACH

We used the RAW264.7 macrophage cell line to screen 1,271 clinically approved chemical compounds, evaluating functional interactions between TRPC3 channels and Nox2, by measuring Nox2 protein stability and ROS production, with and without exposure to doxorubicin. In male C57BL/6 mice, samples of cardiac and gastrocnemius muscle were taken and analysed with morphometric, immunohistochemical, RT-PCR and western blot methods. In the passive smoking model, cells were exposed to DMEM containing cigarette sidestream smoke.

KEY RESULTS

Ibudilast, an anti-asthmatic drug, attenuated ROS-mediated muscle toxicity induced by doxorubicin treatment or passive smoking, by inhibiting the functional interactions between TRPC3 channels and Nox2, without reducing TRPC3 channel activity.

CONCLUSIONS AND IMPLICATIONS

These results indicate a common mechanism underlying induction of systemic tissue wasting by doxorubicin. They also suggest that ibudilast could be repurposed to prevent muscle toxicity caused by anticancer drugs or passive smoking.

Doxorubicin Has Dose-Dependent Toxicity on Mouse Ovarian Follicle Development, Hormone Secretion, and Oocyte Maturation

Doxorubicin (DOX), one of the most commonly used anticancer medications, has been reported to affect fertility by damaging ovarian follicles; however, the dose-dependent toxicity of DOX on the dynamic follicle development and oocyte maturation has not been well-defined. Our objective is to determine the effects of human-relevant exposure levels of DOX on follicular functions across developmental time. In vitro cultured multilayered secondary mouse follicles were treated with DOX at 0, 2, 20, 100, and 200 nM for 24 h, and follicle development, hormone secretion, and oocyte maturation were analyzed. DOX caused dose-dependent toxicity on follicle growth, survival, and secretion of 17β-estradiol (E2). At 200 nM, DOX induced DNA damage and apoptosis in follicle somatic cells first and then in oocytes, which was correlated with the uptake of DOX first to the somatic cells followed by germ cells. Follicles treated with DOX at 0, 2, and 20 nM showed similar oocyte metaphase II (MII) percentages after in vitro oocyte maturation; however, 20 nM DOX significantly increased the number of MII oocytes with abnormal spindle morphology and chromosome misalignment. In an effort to harmonize the in vitro study to in vivo treatment, dose-dependent toxicity on oocyte meiotic maturation was found in 16-day-old CD-1 mice treated with DOX at 0, 0.4, 2, and 10 mg/kg, consistent with the in vitro oocyte maturation outcomes. Our study demonstrates that DOX has dose-dependent toxicity on ovarian follicle development, hormone secretion, and oocyte maturation, which are three key factors to support the female reproductive and endocrine functions.

Genetic background influences susceptibility to chemotherapy-induced hematotoxicity

Hematotoxicity is a life-threatening side effect of many chemotherapy regimens. While clinical factors influence patient responses, genetic factors may also play an important role. We sought to identify genomic loci that influence chemotherapy-induced hematotoxicity by dosing Diversity Outbred mice with one of three chemotherapy drugs; doxorubicin, cyclophosphamide or docetaxel. We observed that each drug had a distinct effect on both the changes in blood cell sub-populations and the underlying genetic architecture of hematotoxicity. For doxorubicin, we mapped the change in cell counts before and after dosing and found that alleles of ATP-binding cassette B1B (Abcb1b) on chromosome 5 influence all cell populations. For cyclophosphamide and docetaxel, we found that each cell population was influenced by distinct loci, none of which overlapped between drugs. These results suggest that susceptibility to chemotherapy-induced hematotoxicity is influenced by different genes for different chemotherapy drugs.

Utility of Dexrazoxane for the Attenuation of Epirubicin-Induced Genetic Alterations in Mouse Germ Cells

Dexrazoxane has been approved to treat anthracycline-induced cardiomyopathy and extravasation. However, the effect of dexrazoxane on epirubicin-induced genetic alterations in germ cells has not yet been reported. Thus, the aim of this study was to determine whether dexrazoxane modulates epirubicin-induced genetic damage in the germ cells of male mice. Our results show that dexrazoxane was not genotoxic at the tested doses. Furthermore, it protected mouse germ cells against epirubicin-induced genetic alterations as detected by the reduction in disomic and diploid sperm, spermatogonial chromosomal aberrations, and abnormal sperm heads. The attenuating effect of dexrazoxane was greater at higher dose, indicating a dose-dependent effect. Moreover, sperm motility and count were ameliorated by dexrazoxane pretreatment. Epirubicin induced marked biochemical changes characteristic of oxidative DNA damage including elevated 8-hydroxy-2'-deoxyguanosine levels and reduction in reduced glutathione. Pretreatment of mice with dexrazoxane before epirubicin challenge restored these altered endpoints. We conclude that dexrazoxane may efficiently mitigate the epirubicin insult in male germ cells, and prevent the enhanced risk of abnormal reproductive outcomes and associated health risks. Thus, pretreating patients with dexrazoxane prior to epirubicin may efficiently preserve not only sperm quality but also prevent the transmission of genetic damage to future generations.

Tertiary amine mediated targeted therapy against metastatic lung cancer

In this work, two tertiary amine-derived 4'-demethylepipodophyllotoxin (DMEP) conjugates (DC and DP) have been designed and synthesized using N,N,N'-trimethyl-N'-(4-carboxyl benzyl)-1,3-propanediamine (CPDM) and 4-(4-methylpiperazinomethyl)benzoic acid (PBA) as the targeting ligands. Both DC and DP exhibited strong in vitro cytotoxicity against small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cell lines. Cellular uptake efficiencies of DC and DP in human alveolar type II epithelial cells were significantly enhanced compared to DMEP and etoposide (VP-16), which were demonstrated to be concentration-, time- and energy-dependent. The active transport process of DC and DP might be mediated by organic cation transporters (OCTs). After systemic administration in mice, both DC and DP selectively accumulated in the lung, displaying the highest C_max and AUC_0-t values of all tested tissues. Compared with DMEP and VP-16, DC and DP remarkably reduced the lung weight and the number of lung metastases of B16 melanoma in mice, and further prolonged the survival of tumor-bearing mice. Also, DC and DP exhibited comparable levels of cell cycle arrest and cell apoptosis. Furthermore, DC and DP demonstrated minimum toxicity towards vital organs and reduced gastrointestinal injury compared to DMEP and VP-16. Taken together, tertiary amine-derived moieties such as CPDM and PBA represent an efficient yet safe strategy to achieve lung-targeted drug delivery.

Impact of dexrazoxane on doxorubicin-induced aneuploidy in somatic and germinal cells of male mice

PURPOSE

Despite dexrazoxane's increasing use in mitigating doxorubicin-induced cardiotoxicity, no data are available in the literature on the potential aneugenicity of drug combination. Therefore, detailed evaluation of aneugenic potential of this combination is essential to provide more insights into aneuploidy induction that may play a role in the development of secondary malignancies and reproductive toxicity after treatment with doxorubicin. Thus, our aim was to determine whether dexrazoxane has influence on the aneuploidy induced by doxorubicin in germinal and somatic cells of male mice.

METHODS

Sperm BrdU-incorporation assay, sperm FISH assay and the bone marrow micronucleus test complemented by FISH assay were used to determine aneuoploidy. Moreover, the formation of 8-OHdG, one of the oxidative DNA damage by-products, has been evaluated.

RESULTS

Dexrazoxane was not aneugenic at the doses tested. Pre-treatment of mice with dexrazoxane significantly reduced doxorubicin-induced aneuploidy in a dose-dependent manner. Doxorubicin induced marked biochemical alterations characteristic of oxidative DNA damage, and prior administration of dexrazoxane before doxorubicin challenge ameliorated this biochemical marker.

CONCLUSION

This study provides evidence that dexrazoxane has a protective role in the abatement of doxorubicin-induced aneuploidy. This activity resides, at least in part, in its radical scavenger activity. Thus, dexrazoxane can avert secondary malignancies and abnormal reproductive outcomes in cured cancer patients exposed to doxorubicin.

Chronic heart damage following doxorubicin treatment is alleviated by lovastatin

The anticancer efficacy of anthracyclines is limited by cumulative dose-dependent early and delayed cardiotoxicity resulting in congestive heart failure. Mechanisms responsible for anthracycline-induced heart damage are controversially discussed and effective preventive measures are preferable. Here, we analyzed the influence of the lipid lowering drug lovastatin on anthracycline-induced late cardiotoxicity three month after treatment of C57BL/6 mice with five low doses of doxorubicin (5×3mg/kg BW; i.p.). Doxorubicin increased the cardiac mRNA levels of BNP, IL-6 and CTGF, while the expression of ANP remained unchanged. Lovastatin counteracted these persisting cardiac stress responses evoked by the anthracycline. Doxorubicin-induced fibrotic alterations were neither detected by histochemical collagen staining of heart sections nor by analysis of the mRNA expression of collagens. Extensive qRT-PCR-array based analyses revealed a large increase in the mRNA level of heat shock protein Hspa1b in doxorubicin-treated mice, which was mitigated by lovastatin co-treatment. Electron microscopy together with qPCR-based analysis of mitochondrial DNA content indicate that lovastatin attenuates doxorubicin-stimulated hyperproliferation of mitochondria. This was not paralleled by increased expression of oxidative stress responsive genes or senescence-associated proteins. Echocardiographic analyses disclosed that lovastatin protects from the doxorubicin-induced decrease in the left ventricular posterior wall diameter (LVPWD), while constrictions in fractional shortening (FS) and ejection fraction (EF) evoked by doxorubicin were not amended by the statin. Taken together, the data suggest beneficial effects of lovastatin against doxorubicin-induced delayed cardiotoxicity. Clinical studies are preferable to scrutinize the usefulness of statins for the prevention of anthracycline-induced late cardiotoxicity.

Efficient pH dependent drug delivery to target cancer cells by gold nanoparticles capped with carboxymethyl chitosan

Doxorubicin (DOX) was immobilized on gold nanoparticles (AuNPs) capped with carboxymethyl chitosan (CMC) for effective delivery to cancer cells. The carboxylic group of carboxymethyl chitosan interacts with the amino group of the doxorubicin (DOX) forming stable, non-covalent interactions on the surface of AuNPs. The carboxylic group ionizes at acidic pH, thereby releasing the drug effectively at acidic pH suitable to target cancer cells. The DOX loaded gold nanoparticles were effectively absorbed by cervical cancer cells compared to free DOX and their uptake was further increased at acidic conditions induced by nigericin, an ionophore that causes intracellular acidification. These results suggest that DOX loaded AuNPs with pH-triggered drug releasing properties is a novel nanotheraputic approach to overcome drug resistance in cancer.

BaxΔ2 is a novel bax isoform unique to microsatellite unstable tumors

The pro-death Bcl-2 family protein and tumor suppressor Bax is frequently mutated in tumors with microsatellite instability (MSI). The mutation often results in a "Bax negative" phenotype and therefore is generally thought to be beneficial to the development of the tumor. Here, we report the identification of a novel Bax isoform, BaxΔ2, which is unique to microsatellite unstable tumors. BaxΔ2 is generated by a unique combination of a microsatellite deletion in Bax exon 3 and alternative splicing of Bax exon 2. Consistently, BaxΔ2 is only detected in MSI cell lines and primary tumors. BaxΔ2 is a potent cell death inducer but does not directly target mitochondria. In addition, BaxΔ2 sensitizes certain MSI tumor cells to a subset of chemotherapeutic agents, such as adriamycin. Thus, our data provide evidence that mutation and alternative splicing of tumor suppressors such as Bax are not always beneficial to tumor development but can be detrimental instead.

Effects of MnDPDP and ICRF-187 on Doxorubicin-Induced Cardiotoxicity and Anticancer Activity

Oxidative stress participates in doxorubicin (Dx)-induced cardiotoxicity. The metal complex MnDPDP and its metabolite MnPLED possess SOD-mimetic activity, DPDP and PLED have, in addition, high affinity for iron. Mice were injected intravenously with MnDPDP, DPDP, or dexrazoxane (ICRF-187). Thirty minutes later, mice were killed, the left atria were hung in organ baths and electrically stimulated, saline or Dx was added, and the contractility was measured for 60 minutes. In parallel experiments, 10 µM MnDPDP or MnPLED was added directly into the organ bath. The effect of MnDPDP on antitumor activity of Dx against two human tumor xenografts (MX-1 and A2780) was investigated. The in vitro cytotoxic activity was studied by co-incubating A2780 cells with MnDPDP, DPDP, and/or Dx. Dx caused a marked reduction in contractile force. In vivo treatment with MnDPDP and ICRF-187 attenuated the negative effect of Dx. When added directly into the bath, MnDPDP did not protect, whereas MnPLED attenuated the Dx effect by approximately 50%. MnDPDP or ICRF-187 did not interfere negatively with the anti-tumor activity of Dx, either in vivo or in vitro. Micromolar concentrations of DPDP but not MnDPDP displayed an in vitro cytotoxic activity against A2780 cells. The present results show that MnDPDP, after being metabolized to MnPLED, protects against acute Dx cardiotoxicity. Both in vivo and in vitro experiments show that cardioprotection takes place without interfering negatively with the anticancer activity of Dx. Furthermore, the results suggest that the previously described cytotoxic in vivo activity of MnDPDP is an inherent property of DPDP.

Dexrazoxane ameliorates doxorubicin-induced injury in mouse ovarian cells

Doxorubicin (DXR) is a frontline chemotherapy agent implicated in unintended ovarian failure in female cancer survivors. The fertility preservation techniques currently available for cancer patients are often time and cost prohibitive and do not necessarily preserve endocrine function. There are no drug-based ovary protection therapies clinically available. This study provides the first investigation using dexrazoxane (Dexra) to limit DXR insult in ovarian tissue. In KK-15 granulosa cells, a 3-h DXR treatment increased double-strand (ds) DNA breaks 40%-50%, as quantified by the neutral comet assay, and dose-dependent cytotoxicity. Dexra exhibited low toxicity in KK-15 cells, inducing no DNA damage and less than 20% cell loss. Cotreating KK-15 cells with Dexra prevented acute DXR-induced dsDNA damage. Similarly, Dexra attenuated the DXR-induced 40%-65% increase in dsDNA breaks in primary murine granulosa cells and cells from in vitro cultured murine ovaries. DXR can cause DNA damage either through a topoisomerase II-mediated pathway, based on DXR intercalation into DNA, or through oxidative stress. Cotreating KK-15 cells with 2 μM Dexra was sufficient to prevent DXR-induced, but not H(2)O(2)-induced, DNA damage. These data indicated the protective effects are likely due to Dexra's inhibition of topoisomerase II catalytic activity. This putative protective agent attenuated downstream cellular responses to DXR, preventing H2AFX activation in KK-15 cells and increasing viability as demonstrated by increasing the DXR lethal dose in KK-15 cells 5- to 8-fold (LD(20)) and primary murine granulosa cells 1.5- to 2-fold (LD(50)). These data demonstrate Dexra protects ovarian cells from DXR insult and suggest that it is a promising tool to limit DXR ovarian toxicity in vivo.

A marine anthraquinone SZ-685C overrides adriamycin-resistance in breast cancer cells through suppressing Akt signaling

Breast cancer remains a major health problem worldwide. While chemotherapy represents an important therapeutic modality against breast cancer, limitations in the clinical use of chemotherapy remain formidable because of chemoresistance. The HER2/PI-3K/Akt pathway has been demonstrated to play a causal role in conferring a broad chemoresistance in breast cancer cells and thus justified to be a target for enhancing the effects of anti-breast cancer chemotherapies, such as adriamycin (ADR). Agents that can either enhance the effects of chemotherapeutics or overcome chemoresistance are urgently needed for the treatment of breast cancer. In this context, SZ-685C, an agent that has been previously shown, as such, to suppress Akt signaling, is expected to increase the efficacy of chemotherapy. Our current study investigated whether SZ-685C can override chemoresistance through inhibiting Akt signaling in human breast cancer cells. ADR-resistant cells derived from human breast cancer cell lines MCF-7, MCF-7/ADR and MCF-7/Akt, were used as models to test the effects of SZ-685C. We found that SZ-685C suppressed the Akt pathway and induced apoptosis in MCF-7/ADR and MCF-7/Akt cells that are resistant to ADR treatment, leading to antitumor effects both in vitro and in vivo. Our data suggest that use of SZ-685C might represent a potentially promising approach to the treatment of ADR-resistant breast cancer.

Inhibition of Rac1 signaling by lovastatin protects against anthracycline-induced cardiac toxicity

Normal tissue damage limits the efficacy of anticancer therapy. For anthracyclines, the clinically most relevant adverse effect is cardiotoxicity. The mechanisms involved are poorly understood and putative cardioprotectants are controversially discussed. Here, we show that the lipid-lowering drug lovastatin protects rat H9c2 cardiomyoblasts from doxorubicin in vitro. Protection by lovastatin is related to inhibition of the Ras-homologous GTPase Rac1. It rests on a reduced formation of DNA double-strand breaks, resulting from the inhibition of topoisomerase II by doxorubicin. Doxorubicin transport and reactive oxygen species are not involved. Protection by lovastatin was confirmed in vivo. In mice, lovastatin mitigated acute doxorubicin-induced heart and liver damage as indicated by reduced mRNA levels of the pro-fibrotic cytokine connective tissue growth factor (CTGF) and pro-inflammatory cytokines, respectively. Lovastatin also protected from doxorubicin-provoked subacute cardiac damage as shown by lowered mRNA levels of CTGF and atrial natriuretic peptide. Increase in the serum concentration of troponin I and cardiac fibrosis following doxorubicin treatment were also reduced by lovastatin. Whereas protecting the heart from harmful doxorubicin effects, lovastatin augmented its anticancer efficacy in a mouse xenograft model with human sarcoma cells. These data show that statins lower the incidence of cardiac tissue injury after anthracycline treatment in a Rac1-dependent manner, without impairing the therapeutic efficacy.

Safety of concurrent administration of dexrazoxane and doxorubicin in the canine cancer patient

Doxorubicin may cause a rare but serious cardiotoxicity. Dexrazoxane is a cardioprotectant drug used to reduce the risk of cardiotoxicity in human patients. In this study, 25 tumour-bearing dogs were treated with concurrent doxorubicin and dexrazoxane. The total number of doses of dexrazoxane given was 54 (range 1-5 doses per dog, median 2 doses). Five dogs received more than 165 mg m(2) cumulative doxorubicin dose before starting dexrazoxane. Haematologic, gastrointestinal and cardiovascular toxicities were considered tolerable. The combination of doxorubicin with dexrazoxane was well tolerated with minimal side-effects in this patient cohort. Future studies are required to evaluate potential cardioprotective effects of dexrazoxane given concurrently with doxorubicin.

Scavenging effects of dexrazoxane on free radicals

Dexrazoxane (ICRF-187) has been clinically used to reduce doxorubicin-induced cardiotoxicity for more than 20 years. It has been proposed that dexrazoxane may act through its rings-opened hydrolysis product ADR-925, which can either remove iron from the iron-doxorubicin complex or bind to free iron, thus preventing iron-based oxygen radical formation. However, it is not known whether the antioxidant actions of dexrazoxane are totally dependent on its metabolization to its rings-opened hydrolysis product and whether dexrazoxane has any effect on the iron-independent oxygen free radical production. In this study, we examined the scavenging effect of dexrazoxane on hydroxyl, superoxide, lipid, DPPH and ABTS⁺ free radicals in vitro solution systems. The results demonstrated that dexrazoxane was an antioxidant that could effectively scavenge these free radicals and the scavenging effects of dexrazoxane did not require the enzymatic hydrolysis. In addition, dexrazoxane was capable to inhibit the generation superoxide and hydroxyl radicals in iron free reaction system, indicating that the antioxidant properties of dexrazoxane were not solely dependent on iron chelation. Thus the application of dexrazoxane should not be limited to doxorubicin-induced cardiotoxicity. Instead, as an effective antioxidant that has been clinically proven safe, dexrazoxane may be used in a broader spectrum of diseases that are known to be benefited by antioxidant treatments.

SZ-685C, a marine anthraquinone, is a potent inducer of apoptosis with anticancer activity by suppression of the Akt/FOXO pathway

BACKGROUND AND PURPOSE

The aims of this study were to investigate the anti-cancer activity of SZ-685C, an anthracycline analogue isolated from marine-derived mangrove endophytic fungi, and to explore the molecular mechanisms underlying such activity.

EXPERIMENTAL APPROACH

The effect of SZ-685C on the viability of cancer cell lines was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. SZ-685C-induced apoptosis was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay and analysis of caspase activation. The effect of SZ-685C on the Akt/FOXO pathway was studied using Western blotting analysis, and the in vivo anti-tumour efficacy was examined in an MDA-MB-435 breast cancer xenograft model.

KEY RESULTS

SZ-685C suppressed the proliferation of six cancer cell lines derived from human breast cancer, prostate cancer, glioma and hepatoma (IC(50) values ranged from 3.0 to 9.6 microM) and the growth of breast cancer xenografts in mice. SZ-685C had a direct apoptosis-inducing effect through both the extrinsic and intrinsic apoptotic pathways, as shown by activation of caspase-8 and 9 as well as effector caspase-3 and poly (ADP-ribose) polymerase. Phosphorylation of Akt and its downstream effectors, forkhead box protein O1 and forkhead box protein O3a, was down-regulated in SZ-685C-treated cancer cells. Furthermore, the pro-apoptotic protein Bim was up-regulated by SZ-685C treatment consistent with FOXO dephosphorylation.

CONCLUSIONS AND IMPLICATIONS

SZ-685C could induce apoptosis through the Akt/FOXO pathway, which consequently leads to the observed anti-tumour effect both in vitro and in vivo. Our data suggest that SZ-685C may be a potentially promising Akt inhibitor and anti-cancer drug candidate.

The dietary flavonoids myricetin and fisetin act as dual inhibitors of DNA topoisomerases I and II in cells

DNA topoisomerases (topos) are the target of several drugs commonly used in cancer chemotherapy; these drugs induce topo-DNA complexes with either topo I or topo II that eventually trigger cell death. The inhibition of these enzymes induces DNA alterations that may also lead to carcinogenic effects; indeed, an increased risk for developing leukemia has been observed in patients treated with some topo II inhibitors. Several flavonoids have been shown to interact with purified topo I and topo II, therefore suggesting that these compounds may possess both anticancer and carcinogenic activity. Because the activity of a drug on purified topoisomerases does not always represent the activity in the cell, the aim of this work is to evaluate the effects of several common dietary flavonoids on these enzymes in cells. Using the cell-based TARDIS assay, we have evaluated the effects of the flavonoids quercetin, apigenin, fisetin and myricetin on topo I and topo II in K562 human leukemia cells at several concentrations and exposure times. Quercetin and apigenin induced moderate levels of topo II-DNA complexes and did not induce topo I-DNA complexes in these cells. Fisetin induced neither topo I- nor topo II-DNA complexes, but behaved as a catalytic inhibitor of both enzymes. Myricetin induced high levels of topo-DNA complexes with both enzymes. In addition, murine embryo fibroblasts lacking topo IIbeta were resistant to myricetin-induced cell-growth inhibition, therefore suggesting that topo IIbeta is an important drug target for this flavonoid. These results support the idea that specific concentrations of some dietary flavonoids may produce topoisomerase-mediated carcinogenic and chemotherapeutic effects in vivo. The ability of myricetin to induce topo-DNA complexes with both topo I and topo II in leukemia cells may be therapeutically useful and deserves further study.

Evaluation of the topoisomerase II-inactive bisdioxopiperazine ICRF-161 as a protectant against doxorubicin-induced cardiomyopathy

Anthracycline-induced cardiomyopathy is a major problem in anti-cancer therapy. The only approved agent for alleviating this serious dose limiting side effect is ICRF-187 (dexrazoxane). The current thinking is that the ring-opened hydrolysis product of this agent, ADR-925, which is formed inside cardiomyocytes, removes iron from its complexes with anthracyclines, hereby reducing the concentration of highly toxic iron-anthracycline complexes that damage cardiomyocytes by semiquinone redox recycling and the production of free radicals. However, the 2 carbon linker ICRF-187 is also is a catalytic inhibitor of topoisomerase II, resulting in the risk of additional myelosuppression in patients receiving ICRF-187 as a cardioprotectant in combination with doxorubicin. The development of a topoisomerase II-inactive iron chelating compound thus appeared attractive. In the present paper we evaluate the topoisomerase II-inactive 3 carbon linker bisdioxopiperazine analog ICRF-161 as a cardioprotectant. We demonstrate that this compound does chelate iron and protects against doxorubicin-induced LDH release from primary rat cardiomyocytes in vitro, similarly to ICRF-187. The compound does not target topoisomerase II in vitro or in cells, it is well tolerated and shows similar exposure to ICRF-187 in rodents, and it does not induce myelosuppression when given at high doses to mice as opposed to ICRF-187. However, when tested in a model of chronic anthracycline-induced cardiomyopathy in spontaneously hypertensive rats, ICRF-161 was not capable of protecting against the cardiotoxic effects of doxorubicin. Modulation of the activity of the beta isoform of the topoisomerase II enzyme by ICRF-187 has recently been proposed as the mechanism behind its cardioprotection. This concept is thus supported by the present study in that iron chelation alone does not appear to be sufficient for protection against anthracycline-induced cardiomyopathy.

A mouse model for studying the interaction of bisdioxopiperazines with topoisomerase IIalpha in vivo

The bisdioxopiperazines such as (+)-(S)-4,4'-propylenedi-2,6-piperazinedione (dexrazoxane; ICRF-187), 1,2-bis(3,5-dioxopiperazin-1-yl)ethane (ICRF-154), and 4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione (ICRF-193) are agents that inhibit eukaryotic topoisomerase II, whereas their ring-opened hydrolysis products are strong iron chelator. The clinically approved analog ICRF-187 is a pharmacological modulator of topoisomerase II poisons such as etoposide in preclinical animal models. ICRF-187 is also used to protect against anthracycline-induced cardiomyopathy and has recently been approved as an antidote for alleviating tissue damage and necrosis after accidental anthracycline extravasation. This dual modality of bisdioxopiperazines, including ICRF-187, raises the question of whether their pharmacological in vivo effects are mediated through interaction with topoisomerase II or via their intracellular iron chelating activity. In an attempt to distinguish between these possibilities, we here present a transgenic mouse model aimed at identifying the contribution of topoisomerase IIalpha to the effects of bisdioxopiperazines. A tyrosine 165 to serine mutation (Y165S) in topoisomerase IIalpha, demonstrated previously to render the human ortholog of this enzyme highly resistant toward bisdioxopiperazines, was introduced at the TOP2A locus in mouse embryonic stem cells by targeted homologous recombination. These cells were used for the generation of transgenic TOP2A(Y165S/+) mice, which were demonstrated to be resistant toward the general toxicity of both ICRF-187 and ICRF-193. Hematological measurements indicate that this is most likely caused by a decreased ability of these agents to induce myelosuppression in TOP2A(Y165S/+) mice, highlighting the role of topoisomerase IIalpha in this process. The biological and pharmacological implications of these findings are discussed, and areas for further investigations are proposed.

Anticancer prodrugs of butyric acid and formaldehyde protect against doxorubicin-induced cardiotoxicity

Formaldehyde has been previously shown to play a dominant role in promoting synergy between doxorubicin (Dox) and formaldehyde-releasing butyric acid (BA) prodrugs in killing cancer cells. In this work, we report that these prodrugs also protect neonatal rat cardiomyocytes and adult mice against toxicity elicited by Dox. In cardiomyocytes treated with Dox, the formaldehyde releasing prodrugs butyroyloxymethyl diethylphosphate (AN-7) and butyroyloxymethyl butyrate (AN-1), but not the corresponding acetaldehyde-releasing butyroyloxydiethyl phosphate (AN-88) or butyroyloxyethyl butyrate (AN-11), reduced lactate dehydrogenase leakage, prevented loss of mitochondrial membrane potential (DeltaPsim) and attenuated upregulation of the proapoptotic gene Bax. In Dox-treated mice, AN-7 but not AN-88 attenuated weight-loss and mortality, and increase in serum lactate dehydrogenase. These findings show that BA prodrugs that release formaldehyde and augment Dox anticancer activity also protect against Dox cardiotoxicity. Based on these observations, clinical applications of these prodrugs for patients treated with Dox warrant further investigation.

The HSP90 and DNA topoisomerase VI inhibitor radicicol also inhibits human type II DNA topoisomerase

Radicicol derivatives are currently investigated as promising antitumoral drugs because they inhibit the activity of the molecular chaperone heat shock protein (HSP90), causing the destabilization and eventual degradation of HSP90 client proteins that are often associated with tumor cells. These drugs interact with the ATP-binding site of HSP90 which is characterized by a structural element known as the Bergerat fold, also present in type II DNA topoisomerases (Topo II). We have previously shown that radicicol inhibits archaeal DNA topoisomerase VI, the prototype of Topo II of the B family (present in archaea, some bacteria and all the plants sequenced so far). We show here that radicicol also inhibits the human Topo II, a member of the A family (comprising the eukaryotic Topo II, bacterial gyrase, Topo IV and viral Topo II), which is a major target for antitumoral drugs. In addition, radicicol prevents in vitro induction of DNA cleavage by human Topo II in the presence of the antitumoral drug etoposide. The finding that radicicol can inhibit at least two different antitumoral drug targets in human, and interferes with drugs currently used in cancer treatment, could have implications in cancer therapy.

Suppression of hepcidin during anemia requires erythropoietic activity

Hepcidin, the principal iron regulatory hormone, regulates the absorption of iron from the diet and the mobilization of iron from stores. Previous studies indicated that hepcidin is suppressed during anemia, a response that would appropriately increase the absorption of iron and its release from stores. Indeed, in the mouse model, hepcidin-1 was suppressed after phlebotomy or erythropoietin administration but the suppression was reversed by inhibitors of erythropoiesis. The suppression of hepcidin necessary to match iron supply to erythropoietic demand thus requires increased erythropoiesis and is not directly mediated by anemia, tissue hypoxia, or erythropoietin.

Experimental study of dexrazoxane–anthracycline combinations using the model of isolated perfused rat heart

We have studied the protective effect of dexrazoxane on the cardiac toxicity induced by the anthracyclines currently used in clinics, doxorubicin, epirubicin, daunorubicin and idarubicin, with special emphasis on determining the optimal dose of dexrazoxane. This was performed using the model of isolated perfused rat heart after 12-day combination treatment of anthracyclines used at equi-cardiotoxic doses, and dexrazoxane used at 10-fold or 20-fold the anthracycline dose. We have shown in this study that dexrazoxane by itself was not cardiotoxic, and was able to significantly reduce anthracycline cardiac toxicity without increasing the general toxicity induced by these drugs. Using dexrazoxane at 20 times the anthracycline dose provided a better cardioprotection than using it at 10 times the anthracycline dose; at the higher dexrazoxane dose, the functional cardiac parameters (developed pressure, contractility and relaxation) were not different from those recorded in control animals.

Combining Etoposide and Dexrazoxane Synergizes with Radiotherapy and Improves Survival in Mice with Central Nervous System Tumors

PURPOSE

The treatment of patients with brain metastases is presently ineffective, but cerebral chemoradiotherapy using radiosensitizing agents seems promising. Etoposide targets topoisomerase II, resulting in lethal DNA breaks; such lesions may increase the effect of irradiation, which also depends on DNA damage. Coadministration of the topoisomerase II catalytic inhibitor dexrazoxane in mice allows for more than 3-fold higher dosing of etoposide. We hypothesized that dexrazoxane combined with escalated etoposide doses might improve the efficacy of cerebral radiotherapy.

EXPERIMENTAL DESIGN

Mice with cerebrally inoculated Ehrlich ascites tumor (EHR2) cells were treated with combinations of etoposide + dexrazoxane + cerebral radiotherapy. Similar chemotherapy and radiation combinations were investigated by clonogenic assays using EHR2 cells, and by DNA double-strand break assay through quantification of phosphorylated histone H2AX (gammaH2AX).

RESULTS

Escalated etoposide dosing (90 mg/kg) combined with dexrazoxane (125 mg/kg) and cerebral radiotherapy (10 Gy x 1) increased the median survival by 60% (P = 0.001) without increased toxicity, suggesting that escalated etoposide levels may indeed represent a new strategy for improving radiotherapy. Interestingly, 125 mg/kg dexrazoxane combined with normal etoposide doses (34 mg/kg) also increased survival from radiotherapy, but only by 27% (P = 0.002). This indicates a direct dexrazoxane modulation of the combined effects of etoposide and radiation in brain tumors. Further, in vitro, concurrent dexrazoxane, etoposide, and irradiation significantly increased DNA double-strand breaks.

CONCLUSION

Combining etoposide (high or normal doses) and dexrazoxane synergizes with cerebral radiotherapy and significantly improves survival in mice with central nervous system tumors. This regimen may thus improve radiation therapy of central nervous system tumors.