Cytotoxic Activity Of Doxorubicin Research Articles

An In Vitro Examination of Whether Kratom Extracts Enhance the Cytotoxicity of Low-Dose Doxorubicin against A549 Human Lung Cancer Cells.

Doxorubicin is an effective chemotherapeutic agent in the treatment of solid hematological and non-hematological carcinoma. However, its long-term usage could result in side effects, such as cardiomyopathy, chronic heart failure, neurotoxicity and cancer cell resistance. In this study, we reported the sensitivity enhancement of A549 human lung cancer cells on doxorubicin at a low dose (0.1 ppm) in combination with 10-60 ppm of crude and alkaloid extracts derived from the leaves of Kratom (Mitragyna speciosa (Korth.) Havil. Rubiaceae). A549 cancer cell lines were insensitive to the crude extract containing low mitragynine (MG) (4-5%), while these cells were moderately inhibited by the alkaloid extract containing 40-45% MG (IC50 of 48-55 ppm). The alkaloid extract was found to inhibit A549 cancer cells via apoptosis as suggested by the higher relative fluorescence intensity with Annexin compared to that in propidium iodide (PI), i.e., a positive Annexin and a negative PI. The combination of crude extract and doxorubicin sensitized A549 cancer cells to doxorubicin by 1.3 to 2.4 times, while the combination with the alkaloid induced a 2.6- to 3.4-fold increase in sensitivity. The calculated combination index (CI) for doxorubicin with the crude and alkaloid extracts was 0.6 and 0.3, respectively, showing potential synergistic combinations to reduce the level of dosage of doxorubicin used in chemotherapy. In addition, the synergistic enhancement effect of crude extract on the cytotoxic activity of doxorubicin provides insights into the plausibility of non-alkaloids to influence the biological activities of Kratom.

Suppressive Effect of Chemically Induced Hypoxia on Glioblastoma Cell Proliferation.

Glioblastoma is a tumor characterized by pronounced hypoxia. Hypoxia produces diverse effects on tumor cells, and the results of experimental studies available so far are contradictory. In vitro hypoxia can be modeled in two ways: by reducing the level of atmospheric oxygen (physically induced hypoxia) or by using hypoxia-inducing chemicals such as cobalt chloride (II) (CoCl2) (chemically induced hypoxia). In the present work, we analyzed the effect of CoCl2 on the viability, proliferation, and apoptosis of cells of three glioblastoma cell lines: 1321N1, T98g, and U373 MG. It was shown that CoCl2 induced a dose-dependent decrease in cell viability and proliferation, and at high concentrations (200 and 400 μM) stimulated cell death. CoCl2 had no effect on the cytotoxic activity of doxorubicin in two cell lines T98g and U373 MG, and enhanced the effect of the chemotherapeutic agent on the 1321N1 cell line, though no synergistic cytotoxic effect of the two agents was observed.

Trojan-like doxorubicin and gold nanoparticle entrapped smart nanostructured lipid carriers for breast cancer synergistic chemo/photothermal therapy

Breast cancer is one of the fatal diseases renowned worldwide. Chemotherapy is not sufficient for the treatment of breast cancer in a significant number of cases. In this study, we present the doxorubicin (DOX) and gold nanoparticles (AuNPs) loaded nanostructured lipid carriers (DOX+AuNPs)@NLCs, designed for dual chemo/photothermal therapy. Different geometries of AuNPs (gold nanospheres (AuNSs), gold nanorods (AuNRs), and gold nanocubes (AuNCs)) were also loaded in NLCs to exploit their photothermal heating capacity and to conceptualize the most efficient combination of drug delivery system for combined therapy. The light-triggered on-demand release of DOX from NLCs was examined before and after NIR irradiation (808 nm). The highest heating potential was obtained via AuNRs with ∆T = 22 °C in 5 min with 19.5 µg Au/mg lipid. The cytotoxic effect of these formulations was evaluated on MDA-MB-231 breast cancer cells and the highest growth inhibition (81%) is achieved with (DOX+AuNRs)@NLC under 5 min NIR application. It is found that the geometry directly effects the photothermal capability of AuNPs, a synergistic interaction between cytotoxic action of DOX and local hyperthermia provided by AuNPs can significantly enhance the skills on the irreversible cellular damage and developed state-of-art formulations hold a great potential as a combined-cancer-therapy agent. Thus, this study offers promise for the development of a lipid-based nano-platform that is biocompatible, multifunctional, and can be utilized for combined therapy, with tunable properties.

Permeation enhancers loaded bilosomes for improved intestinal absorption and cytotoxic activity of doxorubicin

The clinical utility of doxorubicin is compromised due to dose related toxic side effects and limited oral bioavailability with no oral formulation being marketed. Enhancement of intestinal absorption and magnification of cytotoxicity can overcome these limitations. Accordingly, the objective was to probe penetration enhancers, bilosomes and their combinations for enhanced intestinal absorption and improved cytotoxicity of doxorubicin. Piperine and dipyridamole were tested as enhancers alone or encapsulated in bilosomes comprising Span60, cholesterol and bile salts. Bilosomes were nanosized spherical vesicles with negative zeta potential and were able to entrap doxorubicin with efficiency ranging from 45.3 % to 53 %. Intestinal absorption studies utilized in-situ rabbit intestinal perfusion which revealed site dependent doxorubicin absorption correlating with regional distribution of efflux transporters. Co-perfusion with the enhancer increased intestinal absorption with further augmentation after bilosomal encapsulation. The latter increased the % fraction absorbed by 4.5–6 and 1.8–2.5-fold from jejuno-ileum and colon, respectively, depending on bilosomes composition. Additionally, doxorubicin cytotoxicity against breast cancer cells (MCF-7) was significantly improved after bilosomal encapsulation and the recorded doxorubicin IC50 value was reduced from 13.3 μM to 0.1 μM for the best formulation. The study introduced bilosomes encapsulating absorption enhancers as promising carriers for enhanced cytotoxicity and oral absorption of doxorubicin.

Lubeluzole Repositioning as Chemosensitizing Agent on Multidrug-Resistant Human Ovarian A2780/DX3 Cancer Cells.

In a previous paper, we demonstrated the synergistic action of the anti-ischemic lubeluzole (Lube S) on the cytotoxic activity of doxorubicin (Dox) and paclitaxel in human ovarian cancer A2780 and lung cancer A549 cells. In the present paper, we extended in vitro the study to the multi-drug-resistant A2780/DX3 cell line to verify the hypothesis that the Dox and Lube S drug association may potentiate the antitumor activity of this anticancer compound also in the context of drug resistance. We also evaluated some possible mechanisms underlying this activity. We analyzed the antiproliferative activity in different cancer cell lines. Furthermore, apoptosis, Dox accumulation, MDR1 downregulation, ROS, and NO production in A2780/DX3 cells were also evaluated. Our results confirm that Lube S improves Dox antiproliferative and apoptotic activities through different mechanisms of action, all of which may contribute to the final antitumor effect. Moderate stereoselectivity was found, with Lube S significantly more effective than its enantiomer (Lube R) and the corresponding racemate (Lube S/R). Docking simulation studies on the ABCB1 Cryo-EM structure supported the hypothesis that Lube S forms a stable MDR1-Dox-Lube S complex, which hampers the protein transmembrane domain flipping and blocks the efflux of Dox from resistant A2780/DX3 cells. In conclusion, our in vitro studies reinforce our previous hypothesis for repositioning the anti-ischemic Lube S as a potentiating agent in anticancer chemotherapy.

Construction of a Novel Doxorubicin Nanomedicine Using Bindarit as a Carrier: A Multiscale Computer Simulation-Assisted Design-Based Study

Nanomedicines typically use polymeric materials or liposomes as carriers. This provides targeting advantages but may lead to a series of defects, such as low drug loading, high risk in terms of safety, and high production costs. Herein, we report a computer simulation-assisted designing method for the construction of a novel doxorubicin (DOX) nanomedicine without any polymer carriers. We used a small molecular drug, bindarit (BIN), as a carrier of DOX to provide synergistic antitumor effects. First, the intermolecular forces between DOX and BIN were calculated for evaluating the interaction and potential conformation of the DOX/BIN complex. Then, the potential assembly ability of the DOX/BIN complex was predicated here by using dissipative particle dynamic stimulation. These computational simulation results suggested that BIN could form an amphiphilic complex with DOX through π–π stacking, hydrogen bonding, and electrostatic interaction and then self-assemble to nanoaggregates at the mesoscopic scale. Under the computational guidance, doxorubicin/bindarit nanoparticles (DOX/BIN NPs) in a spherical morphology were successfully prepared, and these NPs possess the original cytotoxic activity of DOX. Thus, this multiscale computer simulation-assisted design strategy can serve as an effective approach to develop nanomedicines using small molecules as a carrier.

Cell surface Nucleolin represents a novel cellular target for neuroblastoma therapy

BackgroundNeuroblastoma (NB) represents the most frequent and aggressive form of extracranial solid tumor of infants. Nucleolin (NCL) is a protein overexpressed and partially localized on the cell surface of tumor cells of adult cancers. Little is known about NCL and pediatric tumors and nothing is reported about cell surface NCL and NB.MethodsNB cell lines, Schwannian stroma-poor NB tumors and bone marrow (BM)-infiltrating NB cells were evaluated for the expression of cell surface NCL by Flow Cytometry, Imaging Flow Cytometry and Immunohistochemistry analyses. The cytotoxic activity of doxorubicin (DXR)-loaded nanocarriers decorated with the NCL-recognizing F3 peptide (T-DXR) was evaluated in terms of inhibition of NB cell proliferation and induction of cell death in vitro, whereas metastatic and orthotopic animal models of NB were used to examine their in vivo anti-tumor potential.ResultsNB cell lines, NB tumor cells (including patient-derived and Patient-Derived Xenografts-PDX) and 70% of BM-infiltrating NB cells show cell surface NCL expression. NCL staining was evident on both tumor and endothelial tumor cells in NB xenografts. F3 peptide-targeted nanoparticles, co-localizing with cell surface NCL, strongly associates with NB cells showing selective tumor cell internalization. T-DXR result significantly more effective, in terms of inhibition of cell proliferation and reduction of cell viability in vitro, and in terms of delay of tumor growth in all NB animal model tested, when compared to both control mice and those treated with the untargeted formulation.ConclusionsOur findings demonstrate that NCL could represent an innovative therapeutic cellular target for NB.

Folic acid decoration of mesoporous silica nanoparticles to increase cellular uptake and cytotoxic activity of doxorubicin in human breast cancer cells

Breast cancer is the most frequent cancer among women and impacts over two million women each year. Although many different types of anticancer agents are available for breast cancer treatment, doxorubicin is one of the most widely used drug. However, doxorubicin related side effects such as heart failure and arrhythmia limit its usage. To overcome this limitation and improve doxorubicin effectiveness, pegylated liposomal doxorubicin formulation Doxil®/Caelyx® was developed. Although cardiotoxicity related side effects were reduced with liposomal doxorubicin formulations, a superior effect was not obtained and better approaches are still needed. In this study, it was aimed to develop a more effective doxorubicin formulation than Doxil® and to evaluate its anticancer activity. In order to achieve this goal, small sized mesoporous silica nanoparticles (MSNs) (~50 nm) were obtained, actively targeted with folic acid conjugation and loaded with doxorubicin. The obtained nanoparticles were fully characterized, conjugation was verified, and pH dependent drug release profile was shown. The nanoparticles’ anticancer activity was investigated in detail on the ZR-75-1 and T47-D breast cancer cell lines. Fluorescence microscope and flow cytometry studies revealed that the cellular uptake of doxorubicin could be enhanced with small sized MSNs. Moreover, folic acid conjugation made a tangible contribution to this effect. Additionally, similar results were also obtained in cytotoxicity studies on both cell lines. In conclusion, actively targeted small sized MSNs may be a promising approach to potentiate the anticancer effect of doxorubicin.

In vitro irradiation of doxorubicin with 18F-FDG Cerenkov radiation and its potential application as a theragnostic system.

Doxorubicin (DOX), an effective chemotherapeutic agent, has a wide excitation band centred at 480 nm. Cerenkov radiation (CR) is considered an internal light source in photodynamic therapy (PDT). DOX could be photoactivated by CR and thus, enhancing its cytotoxicity. In this work, 18F-FDG was used to evaluate the effect of Cerenkov radiation on DOX, in comparison to irradiation with a 450-nm laser beam, in terms of ROS production. The production of 1O2 and O2⁎- reactive species during DOX irradiation was detected indirectly by ABMA and DCPIP bleaching, respectively. The cytotoxic effect of the DOX / 18F-FDG CR system was evaluated in the T47D breast cancer cell line. The irradiation of DOX produced 1O2 and O2⁎- species using both 18F-FDG CR and a 450-nm laser beam. The majority reactive species produced in both cases was 1O2; a favourable result, given the greater cytotoxicity of this species. The viability of T47D cells in presence of DOX (5 nM), 18F-FDG (37.5 μCi) and DOX (5 nM)/18F-FDG (37.5 μCi) was (86 ± 9)%, (84 ± 8)% and (64 ± 5)%, respectively; these results suggest a synergistic cytotoxic effect derived from the cytotoxic activity of DOX and its photoactivation by 18F-FDG CR. It is worth noting that the system could be optimized in terms of DOX concentration and 18F-FDG activity for better results. Due to the fact that 18F-FDG is widely used in nuclear imaging, the DOX/18F-FDG system also possesses theragnostic characteristics. Thus, in this work, it is demonstrated that DOX can be used in a dual therapy system based on chemotherapy-PDT when 18F-FDG CR is used as a DOX excitation source.

Abstract 97: The effect of hyaluronan degradation on the uptake and cytotoxic activity of liposome-encapsulated doxorubicin in 3D tumor spheroid models

Abstract The accumulation of hyaluronan (HA) in the solid tumor microenvironment (TME) can be associated with poor prognosis in several human cancers. Accumulation of HA in the TME can increase interstitial pressure that compresses local blood vessels and impairs the access of anti-cancer therapy. In preclinical models, enzymatic degradation of HA by pegvorhyaluronidase alfa (PEGPH20; PVHA), a PEGylated form of recombinant human hyaluronidase PH20 (rHuPH20), is associated with decreased tumor interstitial pressure, improved tumor vascular perfusion, and increased access and anti-tumor efficacy of cytotoxic and immunotherapies. The functional effect of HA degradation on the TME has been mostly characterized in animal tumor models. Here, we describe the utilization of 3D tumor spheroid models to evaluate the effects of HA degradation on the cytotoxic effect of anti-cancer therapies. A number of commonly used human colorectal cancer (CRC) cell lines were assessed for HA accumulation and tumor spheroid morphology: HCT 116, HT-29 parental, and HT-29/HAS3 (HT-29 cells engineered to over-express hyaluronan synthase 3). CRC 3D tumor spheroid models were developed to evaluate the uptake and cytotoxic activity of liposome-encapsulated doxorubicin (DOX) using the IncuCyte® S3 Live-Cell Analysis System. The effect of HA degradation on DOX uptake and cytotoxic activity was initially tested with rHuPH20 treatment in all three models, and further evaluated with PVHA treatment in HT-29 parental and HT-29/HAS3 models. A dose-dependent uptake and cytotoxic activity of DOX was observed in HCT 116 tumor spheroids. HA degradation after rHuPH20 treatment enhanced DOX uptake by an average of 6.1% (up to 7.7%) and cytotoxicity by an average of 37.9% (up to 58.2%) over the 5-day duration of the experiment compared with DOX alone. Dose-dependent uptake and cytotoxic activity of DOX in HT-29/HAS3 tumor spheroids were enhanced with rHuPH20 treatment to a greater extent than in HT-29 parental tumor spheroids. Specifically, rHuPH20 treatment led to an average increase in DOX uptake of 9.2% (up to 14.6%) with HT-29/HAS3 spheroids and 2.6% (up to 5.1%) with HT-29 parental spheroids. The addition of rHuPH20 resulted in an average increase in DOX cytotoxicity of 101% (up to 227.6%) with HT-29/HAS3 spheroids and 24.9% (up to 63.9%) with HT-29 parental spheroids. Enhanced uptake and cytotoxic activity of DOX was also observed with PVHA treatment in HT-29 and HT-29/HAS3 models. These data corroborate our previous findings with in vivo tumor models, in which the combination of PVHA-mediated HA degradation and other anti-cancer therapies display enhanced anti-tumor activity compared with either agent alone. Further, 3D tumor spheroid models may be used to evaluate the effect of extracellular matrix remodeling such as HA degradation and serve as a bridge between 2D cell-based assays and in vivo tumor models. Citation Format: Feng Gao, Susan Zimmerman, Kelly Chen, Daniel C. Maneval, Chunmei Zhao. The effect of hyaluronan degradation on the uptake and cytotoxic activity of liposome-encapsulated doxorubicin in 3D tumor spheroid models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 97.

Antioxidant and Protective Effects of Schinus terebinthifolius Raddi Against Doxorubicin-Induced Toxicity.

Doxorubicin is an anticancer drug whose toxic effects on non-cancer cells are associated with increased oxidative stress. This study investigated the chemical composition, antioxidant activity of the methanolic extract of Schinus terebinthifolius Raddi leaves (MESL) as well as effects against doxorubicin-induced toxicity in human erythrocytes, K562 human erythroleukemia cells, and mouse hearts. The chemical composition indicated the presence of phenolic compounds, flavonoids, tannins, and ascorbic acid. MESL showed antioxidant activity by scavenging free radicals and inhibiting hemolysis and lipid peroxidation in human erythrocytes incubated with an oxidizing agent, and was able to increase the enzymatic activity of superoxide dismutase and glutathione peroxidase in human erythrocytes, without influencing the activity of enzyme catalase. The increase of oxidative hemolysis and malondialdehyde levels in erythrocytes incubated with doxorubicin was reduced by treatment with MESL. The cytotoxic activity of doxorubicin in erythroleukemia cells treated with MESL was unmodified. Additionally, the extract protected mice against the doxorubicin-induced cardiotoxicity. In conclusion, the MESL exhibits antioxidant activity, reducing doxorubicin-induced oxidative stress without changing the anticancer action of the drug, and protects against doxorubicin-induced cardiotoxicity. Hence, these findings suggest that these effects are via anti-oxidative by inhibiting free radicals, decreased oxidative stress, and increased antioxidant enzyme activity.

The Effect of Marigold Leaves and Doxorubicin Toward Cell Cycle and Apoptosis of T47D Cells

Doxorubicin is a commonly used chemotherapeutic agent in patients with breast cancer. The risk of side effect using of doxorubicin such as cardiomyopathy and congestive heart failure which can lead to death. One of the approach to overcome overloaded use of doxorubicin is the combined use with a chemopreventive agent (cochemotherapy), including the leaf extract of marigolds (Cosmos caudatus Kunth.). This research aims to reviewing the effect of the methanol extract of leaves of marigolds on the cytotoxic activity of doxorubicin in modulating cell cycle and apoptosis of breast cancer cells T47D. Determination of the cytotoxic activity of methanol extract of leaves of marigolds and doxorubicin as well as a combination of both conducted by MTT assay. modulation surveillance of cell cycle and apoptosis induction is done by using flowcytometry and analyzed by FACS Calibur program. Cytotoxicity assay single treatment of the methanol extract of leaves of marigolds produce use values of IC50 504,840 μg/ml, whereas IC50 values doxorubicin is 141,055 nM. The synergistic effect was shown a combination of methanol extract leaves marigolds and doxorubicin at concentrations of 84,17 μg/ml -23,5 nM; 84,17 μg/ml -47 nM; 126,25 μg/ml -23,5 nM; 252,5 μg/ml -35,25 nM and 252,5 μg/ml -71 nM with a combination index value (CI) consecutively of 0,5; 0,6; 0,6; 0,6 and 0,6. Observations modulation of cell cycle and apoptosis induction combination of methanol extract leaves marigolds and doxorubicin at concentrations of 84,17 μg/ml -23,5 nM, said that a combination of the methanol extract of leaves of marigolds and doxorubicin to inhibit the proliferation of cells in G2 / M phase and able to induce apoptosis of breast cancer cells T47D.Keywords: methanol extract of leaves of marigolds, doxorubicin, flowcytometry, cell cycle, apoptosis.

PGV-0 AND PGV-1 INCREASED APOPTOSIS INDUCTION OF DOXORUBICIN ON MCF-7 BREAST CANCER CELLS

As chemotherapeutic backbone for breast cancer therapy, doxorubicin showed various side effects and induced resistancy of breast cancer cells. Development of targeted therapy on breast cancer focused on combinatorial therapy of doxorubicin and molecular targeted agents. PGV-0 and PGV-1, a curcumin analogue showed potency as co-chemotherapeutic agent with doxorubicin. Our previous study of PGV-0 and PGV-1 showed cytotoxic activity in T47D cells. Therefore, the aim of this research is to examine the synergistic effect of PGV-0, PGV-1 on the cytotoxic activity of doxorubicin through cell cycle modulation and apoptotic induction on MCF-7 breast cancer cell lines. The cytotoxic assay of PGV-0, PGV-1, doxorubicin, and their combination were carried out by using MTT assay. Cell cycle distribution and apoptosis were determined by flowcytometer FACS-Calibur and the flowcytometry data was analyzed using Cell Quest program. Single treatment of PGV-0, PGV-1 and doxorubicin showed cytotoxic effect on MCF-7 with cell viability IC50 value 50 µM, 6 µM and 350 nM respectively. Single treatment of Doxorubicin 175 nM induced G2/M arrest. Single treatment of PGV-0 5 µM induced G2/M arrest while in higher dose 12.5 µM, PGV-0 induced apoptosis. Combination of doxorubicin 175 nM and PGV-0 5 µM induced apoptosis. Combination of doxorubicin 175 nM and PGV-0 12.5 µM also increased apoptosis induction. Single treatment of PGV-1 0.6 µM induced G1 arrest while in higher dose 1.5 µM, PGV-1 induced apoptosis. Combination of doxorubicin 175 nM and PGV-1 0.6 µM induced apoptosis. Combination of doxorubicin 175 nM and PGV-0 1.5 µM also increased apoptosis induction. PGV-0 and PGV-1 are potential to be delevoped as co-chemotherapeutic agent for breast cancer by inducing apoptosis and cell cycle modulation, but the molecular mechanism need to be explored detail. Key words: PGV-0, PGV-1, doxorubicin, co-chemotherapy, breast cancer, cell cycle arrest, apoptosis

Enhancement of the uptake and cytotoxic activity of doxorubicin in cancer cells by novel cRGD-semipeptide-anchoring liposomes.

Novel liposemipeptides hanging cyclic azabicycloalkane-RGD or aminoproline-RGD terminals were synthesized and incorporated into liposomal nanoparticles cAba/cAmpRGD-LNP5 3C/3D. Liposomes with similar composition and lacking semipeptide conjugates were constructed for comparison (LNP, 3A), and physical encapsulation of the anticancer doxorubicin drug in both targeted and untargeted liposomes was accomplished. Microstructural analysis performed by dynamic light scattering (DLS), small-angle neutron scattering (SANS), and electron paramagnetic resonance (EPR) revealed that the conjugated nanoparticles presented an average size of 80 nm and were constituted by 5 nm thick unilamellar liposome bilayer. Flow cytometry and fluorescent microscopy studies showed that 3C-DOXO and 3D-DOXO efficiently delivered the drug into the nuclei of both quiescent and proliferating cells even in a high serum concentration environment. The uptake of doxorubicin when carried by liposomes was faster than that of the free drug, and 30 min incubation was sufficient to load cell nuclei with doxorubicin. Targeted liposomes significantly induced cell death of human breast adenocarcinoma MCF7 cells (IC50 = 144 nM, 3C-DOXO; IC50 = 274 nM, 3D-DOXO), about 2- to 6-fold more potent than free doxorubicin or 3A-DOXO controls (IC50 = 527 and 854 nM, respectively). These results suggest that cAba/cAmpRGD liposomal nanoparticles hold promise for the rapid and efficient delivery of chemotherapeutic agents to αVβ3-expressing tumor cells.

Abstract PD5-3: Anti-metastatic activity, chemotherapeutic enhancement and therapeutic potential of targeting Hsp90 with ganetespib in triple negative breast cancer

Abstract Background: While the incidence of triple negative breast cancer (TNBC) is only 10-20%, these tumors show a disproportionate mortality for breast cancer patients. Due to a lack of effective molecular targets in this disease, therapeutic options are largely limited to systemic chemotherapeutic approaches which have shown disappointing efficacy in the metastatic setting. Here we undertook a comprehensive evaluation of the activity of the drug candidate, ganetespib, a potent inhibitor of heat shock protein 90 (Hsp90), in this malignancy. Methods: The sensitivity of TNBC cells to ganetespib was determined in viability assays using a panel of tumor lines. The effects of ganetespib exposure on client proteins and their effector pathways were examined by Western blot and reverse phase protein array analysis. The anti-metastatic activity of ganetespib was evaluated using a 4T1 metastasis model. Combinatorial drug analyses were performed with chemotherapeutic agents. DNA damage and cell cycle disruption were assessed using the comet assay, Western blotting and fluorescence microscopy. The in vivo efficacy of the compound, both as a single agent and in combination, was established using MDA-MB-231 xenograft models. Computed tomography scans were obtained for a metastatic TNBC patient undergoing ganetespib treatment. Results: Ganetespib reduced cell viability in TNBC cell lines with low nanomolar potency. Ganetespib treatment induced robust destabilization of multiple client proteins and oncogenic signaling pathways and suppressed lung metastasis in the experimental model. Ganetespib potentiated the cytotoxic activity of doxorubicin via enhanced DNA damage and mitotic arrest, conferring superior efficacy to the doxorubicin + cyclophosphamide (AC) regimen in MDA-MB-231 xenograft models. Ganetespib also promoted mitotic catastrophe and apoptosis in combination with taxanes in vitro, and these effects translated to significantly improved combinatorial activity in vivo. Marked tumor shrinkage of metastatic lung lesions was seen in the patient while on ganetespib monotherapy. Conclusion: The preclinical activity profile and clinical evidence of tumor regression suggest that ganetespib offers considerable promise as a new therapeutic candidate to target TNBC. In particular, the capacity of ganetespib to potentiate the activity of standard of care chemotherapeutics provides a rationale for the exploration of this agent in novel combinatorial treatment strategies for this disease. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD5-3.

Abstract 4389: E2F7 regulates sensitivity to the cytotoxic actions of anthracyclins in squamous cell carcinoma.

Abstract Squamous cell carcinoma (SCC) of the skin and head and neck region is a common and potentially fatal malignancy. Current chemotherapy treatments are generally not curative. Therefore, there is considerable need to develop new and targeted therapies to treat SCC. There is abundant data to show that E2Fs play an important role in many KC functions such as differentiation, growth and apoptosis. However, the identification of two new inhibitory forms of E2F, E2F7 and E2F8 has caused a rethink of our previous models. In this study, we examined the effects of E2F1, E2F7 and E2F8 on cytotoxic responses to chemotherapeutic agents. For in vitro experiments, we generated murine KCs from E2F7 fl/fl or E2F8 fl/fl mice that were made deficient in E2F7 and E2F8 following infection with Cre expressing adenoviral constructs. In addition, we had KCs generated from E2F1 KO mice. Our results showed that E2F8 deficient KCs displayed unaltered responses to 3 structurally different classes of chemotherapeutics represented by doxorubicin (anthracycline), cisplatin (platinum) or etoposide (topoisomerase II inhibitor). Similarly, E2F1 and E2F7-deficient KCs retained apoptotic responses to etoposide and cisplatin. In contrast, E2F7-deficient murine KCs were selectively sensitised to the cytotoxic actions of doxorubicin whilst E2F1-deficiency protected against doxorubicin. We showed that the sensitivity to doxorubicin was E2F7 specific since the reintroduction of E2F7 in E2F7 deficient KCs had a clear protective effect against doxorubicin. These results indicate that E2F7 regulate cytotoxic responses of SCC to doxorubicin, and doxorubicin toxicity is mediated, in part, by an E2F1-dependent mechanism. We also looked at the possible mechanism to drive E2F7-mediated doxorubicin induced cell death. Our results showed activation of caspase-3 in E2F7 deficient KCs mediates the doxorubicin-induced reduction in cell viability. Since E2F7 modulates sensitivity to doxorubicin, we looked at different SCC cells in their response to cytotoxic action of doxorubicin. The results suggested that SCC cells vary in their sensitivity to doxorubicin and this correlates with E2F7/E2F1 protein expression ratio in these SCC cells. The most sensitive SCC cell lines, KJD, had a very low E2F7/E2F1 ratio whilst the most insensitive SCC cell line, SCC25, had a very high E2F7/E2F1 ratio. These data showed that E2F7/E2F1 ratio is disrupted in SCC and this contributes to the insensitivity to cytotoxic actions of doxorubicin. Combined, these data indicate the existence of a novel, non-redundant and isoform-specific activities of E2F7 in KCs that have implications for our understanding of chemotherapeutic sensitivity in SCC. Our findings would suggest that if we sensitise SCC to the effects of anthracyclines, this would have a significant clinical value and add to therapeutic options available to treat SCC patients where there is a critical need. Citation Format: Mehlika Hazar Rethinam, Nicholas Saunders, Fiona Simpson. E2F7 regulates sensitivity to the cytotoxic actions of anthracyclins in squamous cell carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4389. doi:10.1158/1538-7445.AM2013-4389

The role of bioreductive activation of doxorubicin in cytotoxic activity against leukaemia HL60-sensitive cell line and its multidrug-resistant sublines

Clinical usefulness of doxorubicin (DOX) is limited by the occurrence of multidrug resistance (MDR) associated with the presence of membrane transporters (e.g. P-glycoprotein, MRP1) responsible for the active efflux of drugs out of resistant cells. Doxorubicin is a well-known bioreductive antitumour drug. Its ability to undergo a one-electron reduction by cellular oxidoreductases is related to the formation of an unstable semiquionone radical and followed by the production of reactive oxygen species. There is an increasing body of evidence that the activation of bioreductive drugs could result in the alkylation or crosslinking binding of DNA and lead to the significant increase in the cytotoxic activity against tumour cells. The aim of this study was to examine the role of reductive activation of DOX by the human liver NADPH cytochrome P450 reductase (CPR) in increasing its cytotoxic activity especially in regard to MDR tumour cells. It has been evidenced that, upon CPR catalysis, DOX underwent only the redox cycling (at low NADPH concentration) or a multistage chemical transformation (at high NADPH concentration). It was also found, using superoxide dismutase (SOD), that the first stage undergoing reductive activation according to the mechanism of the redox cycling had the key importance for the metabolic conversion of DOX. In the second part of this work, the ability of DOX to inhibit the growth of human promyelocytic-sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX) was studied in the presence of exogenously added CPR. Our assays showed that the presence of CPR catalysing only the redox cycling of DOX had no effect in increasing its cytotoxicity against sensitive and MDR tumour cells. In contrast, an important increase in cytotoxic activity of DOX after its reductive conversion by CPR was observed against HL60 as well as HL60/VINC and HL60/DOX cells.

Selective cytotoxicity of betulinic acid on tumor cell lines, but not on normal cells

Betulinic acid is a triterpene with selective cytotoxicity against melanoma, neuroectodermal and malignant brain tumor cell lines. In this study the betulinic acid activity was evaluated, in comparison with doxorubicin, on different human neoplastic and non-neoplastic cell lines and on proliferating normal lymphocytes. Growth inhibition was evident in all the neoplastic cell lines independently on p53 status and histotype. Antiproliferative activity of betulinic acid was related to a cytotoxic effect on two p53 wild-type and on one p53 mutant cell lines and to a cytostatic effect on one p53 mutant melanoma clone. At the same concentrations, normal cells were unaffected indicating a selective effect of this agent. A cytotoxic activity of doxorubicin was evident on all the tested systems. In vivo experiments, performed on one of these cell lines, confirmed the antineoplastic activity of this drug. These data support further preclinical studies of betulinic acid not confined to melanoma and neuroectodermal tumors independently of p53 status.

The effect of 5´-(N,N-dimethyl)-amiloride on cytotoxic activity of doxorubicin and vincristine in CEM cell lines

The effect of 5´-(N,N-dimethyl)-amiloride on cytotoxic activity of doxorubicin and vincristine in CEM cell lines

Modulation of cytotoxic drug activity by mitotane and lonidamine in human adrenocortical carcinoma cells.

The ability of mitotane, a DDT derivative with adrenotoxic activity, and lonidamine, an energolytic derivative of indazole-carboxylic acid, to modulate the cytotoxic activity of doxorubicin, epidoxorubicin, cisplatin and VP16 was investigated in a human adrenocortical carcinoma cell line (SW13). A marked variability in cellular response to a 1-h treatment with the individual anticancer agents was observed. The concentrations able to inhibit SW13 cell proliferation by 50% (IC50) were 0.45 microg/ml and 0.4 microg/ml for doxorubicin and epidoxorubicin, respectively, thus indicating a relative sensitivity to anthracyclines. Conversely, the SW13 cell line displayed a marked resistance to cisplatin (IC50, 13.9 microg/ml) and VP16 (IC50, 15 microg/ml). When cells were exposed to anticancer drugs and mitotane simultaneously or in sequence, a positive modulation of anthracycline cytotoxic effects was observed. Although to a lesser extent, mitotane also increased cisplatin activity. Conversely, no potentiation was observed when mitotane was combined with VP16. Lonidamine slightly increased the cytotoxicity of epirubicin and cisplatin as individual agents. Moreover, a supra-additive effect of the three-drug (epidoxorubicin-cisplatin-lonidamine) combination was observed.