Multidrug-resistant Human Breast Cancer Research Articles

Pilot study of jadomycin B pharmacokinetics and anti-tumoral effects in zebrafish larvae and mouse breast cancer xenograft models.

Despite numerous therapeutic options, multidrug resistance (MDR) remains an obstacle to successful breast cancer therapy. Jadomycin B, a natural product derived from Streptomyces venezuelae ISP5230, maintains cytotoxicity in MDR human breast cancer cells. Our objectives were to evaluate the pharmacokinetics, toxicity, anti-tumoral, and anti-metastatic effects of jadomycin B in zebrafish larvae and mice. In a zebrafish larval xenograft model, jadomycin B significantly reduced the proliferation of human MDA-MB-231 cells at or below its maximum tolerated dose (40 µm). In female Balb/C mice, a single intraperitoneal dose (6mg/kg) was rapidly absorbed with a maximum serum concentration of 3.4±0.27 µm. Jadomycin B concentrations declined biphasically with an elimination half-life of 1.7±0.058h. In the 4T1 mouse mammary carcinoma model, jadomycin B (12mg/kg every 12h from day 6 to 15 after tumor cell injection) decreased primary tumor volume compared to vehicle control. Jadomycin B-treated mice did not exhibit weight loss, nor significant increases in biomarkers of impaired hepatic (alanine aminotransferase) and renal (creatinine) function. In conclusion, jadomycin B demonstrated a good safety profile and provided partial anti-tumoral effects, warranting further dose-escalation safety and efficacy studies in MDR breast cancer models.

Effects of the surface charge of polyamidoamine dendrimers on cellular exocytosis and the exocytosis mechanism in multidrug-resistant breast cancer cells

BackgroundPolyamidoamine (PAMAM) dendrimer applications have extended from tumor cells to multidrug-resistant tumor cells. However, their transportation in multidrug-resistant tumor cells remains unclear. Herein, we investigated the exocytosis rule and mechanism of PAMAM dendrimers in multidrug-resistant tumor cells.ResultsUsing a multidrug-resistant human breast cancer cell model (MCF-7/ADR), we performed systematic analyses of the cellular exocytosis dynamics, pathways and mechanisms of three PAMAM dendrimers with different surface charges: positively charged PAMAM-NH2, neutral PAMAM-OH and negatively charged PAMAM-COOH. The experimental data indicated that in MCF-7/ADR cells, the exocytosis rate was the highest for PAMAM-NH2 and the lowest for PAMAM-OH. Three intracellular transportation processes and P-glycoprotein (P-gp) participated in PAMAM-NH2 exocytosis in MCF-7/ADR cells. Two intracellular transportation processes, P-gp and multidrug resistance (MDR)-associated protein participated in PAMAM-COOH exocytosis. P-gp and MDR-associated protein participated in PAMAM-OH exocytosis. Intracellular transportation processes, rather than P-gp and MDR-associated protein, played major roles in PAMAM dendrimer exocytosis. PAMAM-NH2 could enter MCF-7/ADR cells by forming nanoscale membrane holes, but this portion of PAMAM-NH2 was eliminated by P-gp. Compared with PAMAM-OH and PAMAM-COOH, positively charged PAMAM-NH2 was preferentially attracted to the mitochondria and cell nuclei. Major vault protein (MVP) promoted exocytosis of PAMAM-NH2 from the nucleus but had no effect on the exocytosis of PAMAM-OH or PAMAM-COOH.ConclusionsPositive charges on the surface of PAMAM dendrimer promote its exocytosis in MCF-7/ADR cells. Three intracellular transportation processes, attraction to the mitochondria and cell nucleus, as well as nuclear efflux generated by MVP led to the highest exocytosis observed for PAMAM-NH2. Our findings provide theoretical guidance to design a surface-charged tumor-targeting drug delivery system with highly efficient transfection in multidrug-resistant tumor cells. Especially, to provide more DNA to the nucleus and enhance DNA transfection efficiency in multidrug-resistant tumor cells using PAMAM-NH2, siRNA-MVP or an inhibitor should be codelivered to decrease MVP-mediated nuclear efflux.Graphical abstract

Hypoxia-sensitive micellar nanoparticles for co-delivery of siRNA and chemotherapeutics to overcome multi-drug resistance in tumor cells.

Recently, it has been discovered that the PEG layer on nanoparticle surface can create steric hindrance, preventing efficient cellular uptake of PEGylated nanoparticles. Thus, it would be ideal to have a nanoparticle system that sheds the PEG layer upon reaching the tumor microenvironment. Hypoxia, which is a hallmark of cancerous tumors, can be used as a trigger to shed the PEG layer from the nanoparticle surface. In this study, a hypoxia-sensitive PEG-azobenzene-PEI-DOPE (PAPD) construct, with an azobenzene group as a hypoxia-sensitive moiety, was prepared. The feasibility of co-delivering Doxorubicin (Dox) and anti-P-gp siRNA (siPgp) using the PAPD nanoparticles was evaluated in monolayers of the Adriamycin-resistant human ovarian cancer cell line, A2780 ADR, and in 3D spheroids of the multidrug-resistant human breast cancer cell line, MCF7 ADR. Under hypoxic conditions, the PAPD nanoparticles showed up to a 60% increase in cellular uptake by monolayers and a significantly greater tumor penetration in a spheroid model. siPgp, when delivered using PAPD nanoparticles, showed up to a 60% P-gp downregulation under hypoxic conditions. The combination of siPgp and Dox delivered using PAPD nanoparticles led to an 80% cytotoxicity in cell monolayers and 20% cytotoxicity in spheroids under hypoxic conditions. In this research, a novel hypoxia-sensitive nanoparticle system was developed that demonstrated improved delivery of an encapsulated cargo and augmented cytotoxicity on multidrug-resistant cancer cells under hypoxic conditions.

Three-dimensional tissue culture model of human breast cancer for the evaluation of multidrug resistance.

Multidrug resistance (MDR) is one of the major obstacles to improving outcomes of chemotherapy in tumour patients. However, progress has been slow to overcome this phenomenon due to the limitations of current cell/tissue models in recapitulating MDR behaviour of tumour cells in vitro. To address this issue, a more pathologically relevant, three-dimensional (3D) culture of human breast cancer cells was developed by seeding the adriamycin-resistant cells MCF-7R in silk-collagen scaffolds. The cultures of the parental cell line MCF-7 served as controls. Distinct growth profiles of MCF-7R and MCF-7 cells were observed when they were cultured in the scaffolds in comparison with those in the monolayer culture, including cell proliferation, cellular aggregate formation, and expression of drug resistance-related genes/proteins. Moreover, the 3D cultures of these cell lines especially the cultures of MCF-7R exhibited a significantly enhanced drug resistance evidenced by their increased IC50 values to the anticancer drugs and improved drug efflux capability. An altered cell cycle distribution and improved percentage of breast cancer stem cell (BCSC)-like cells was also found in the present study. This might play an important role in promoting the drug-resistance production in those 3D cultures. Thus, we established improved 3D cultures of MDR human breast cancer. It would provide a robust tissue model for use to evaluate the efficacy of anticancer drugs, explore mechanisms of MDR, and enrich BCSCs in vitro.

Small size mesoporous organosilica nanorods with different aspect ratios: Synthesis and cellular uptake

In the work, small size thioether-bridged mesoporous organosilica nanorod (MONRs) are successfully synthesized using cetyltrimethylammonium bromide (CTAB) as structure-directing agent and bis[3-(triethoxysilyl)propyl]tetrasulfide (TETS) and tetraethoxysilane (TEOS) as co-precursors. The MONRs have tunable aspect ratios of 2, 3, and 4 (denoted as MONRs-2, MONRs-3, and MONRs-4), small and controllable lengths (75–310nm), high surface area (570–870cm2g−1), uniform mesopores (2.4–2.6nm), large pore volume (0.34cm3g−1), and excellent biocompatibility. The uptake of the MONRs by multidrug resistant human breast cancer MDR-MCF-7 cells is related to their aspect ratios. The MONRs-3 shows a faster and higher cellular internalization compared to the MONRs-4 and MONRs-2, respectively. Thanks to the high cellular uptake, doxorubicin (DOX) loaded MONRs-3 show obviously improved chemotherapeutic effect on MDR-MCF-7 cancer cells. It is expected that the MONRs provide a useful platform for drug delivery and therapeutics.

Synthesis and in vitro biological evaluation of thiosulfinate derivatives for the treatment of human multidrug-resistant breast cancer

Organosulfur compounds derived from Allium vegetables have long been recognized for various therapeutic effects, including anticancer activity. Allicin, one of the main biologically active components of garlic, shows promise as an anticancer agent; however, instability makes it unsuitable for clinical application. The aim of this study was to investigate the effect of stabilized allicin derivatives on human breast cancer cells in vitro. In this study, a total of 22 stabilized thiosulfinate derivatives were synthesized and screened for their in vitro antiproliferative activities against drug-sensitive (MCF-7) and multidrug-resistant (MCF-7/Dx) human adenocarcinoma breast cancer cells. Assays for cell death, apoptosis, cell cycle progression and mitochondrial bioenergetic function were performed. Seven compounds (4b, 7b, 8b, 13b, 14b, 15b and 18b) showed greater antiproliferative activity against MCF-7/Dx cells than allicin. These compounds were also selective towards multidrug-resistant (MDR) cells, a consequence attributed to collateral sensitivity. Among them, 13b exhibited the greatest anticancer activity in both MCF-7/Dx and MCF-7 cells, with IC50 values of 18.54±0.24 and 46.50±1.98 μmol/L, respectively. 13b altered cellular morphology and arrested the cell cycle at the G2/M phase. Additionally, 13b dose-dependently induced apoptosis, and inhibited cellular mitochondrial respiration in cells at rest and under stress. MDR presents a significant obstacle to the successful treatment of cancer clinically. These results demonstrate that thiosulfinate derivatives have potential as novel anticancer agents and may offer new therapeutic strategies for the treatment of chemoresistant cancers.

A chemo/photo- co-therapeutic system for enhanced multidrug resistant cancer treatment using multifunctional mesoporous carbon nanoparticles coated with poly (curcumin-dithiodipropionic acid)

It is still a tremendous challenge to combat multidrug resistant (MDR) cancer up to now, due to cancer resistance to chemotherapeutic agents. Herein, we put a new strategy for effective treatment of MDR cancer by improving chemotherapeutic efficacy via chemosensitizer in combination with phototherapy. Our previous work has demonstrated poly (ethylene glycol) - poly (curcumin-dithiodipropionic acid) (PEG-PCDA) is a good pre-chemosensitizer and enhances the sensitivity of MDR cancer cells to doxorubicin (DOX). In this study, we firstly synthesized mesoporous carbon nanoparticles (MCNs) having excellent photothermal and photodynamic effects, which could load a high dose of hydrophobic drug and presented pH-responsive drug release characteristics. On this basis, we developed a multifunctional MCN based drug delivery system to take chemo/photo- co-therapy against MDR human breast cancer MCF-7/ADR cells. The MCN based drug delivery system loaded 36.4% DOX and was coated with 23.2% PEG-PCDA, which could take photothermal and photodynamic effects under near-infrared (NIR) irradiation and trigger drug release by pH, glutathione (GSH), and/or NIR irradiation, termed as PEG-PCDA/DOX@MCNs. Once the PEG-PCDA/DOX@MCNs had been delivered into MCF-7/ADR cells, DOX release was triggered by degradation of PEG-PCDA via GSH and weak acidic pH, and in combination with MCN yielded photothermal and photodynamic effects under NIR irradiation, PEG-PCDA/DOX@MCNs could reduce premature drug release and then enhance anti-MDR cancer efficacy.

A new NIR-triggered doxorubicin and photosensitizer indocyanine green co-delivery system for enhanced multidrug resistant cancer treatment through simultaneous chemo/photothermal/photodynamic therapy.

A new near-infrared (NIR) triggered chemotherapeutic agent doxorubicin (DOX) and photosensitizer indocyanine green (ICG) co-release system by aid of NIR induced photothermal effect of gold nanocages (AuNCs) and temperature sensitive phase-change property of 1-tetradecanol at its melting point of 39°C, was prepared, termed as DOX/ICG@biotin-PEG-AuNC-PCM, which could simultaneously exerted chemo/photothermal/photodynamic treatment on MDR human breast cancer MCF-7/ADR cells. DOX/ICG@biotin-PEG-AuNC-PCM exerted excellent anti-tumor effects under NIR irradiation, its IC50 against MCF-7/ADR cells was very low, only 0.48µg/mL, much smaller than that of free DOX (74.51μg/mL).

Study of Jadomycin Pharmacokinetics in Balb/C Mice

BackgroundJadomycins are natural product molecules derived from the soil bacteria Streptomyces venezuelae; jadomycins maintain their cytotoxicity in multidrug resistant (MDR) human and mouse breast cancer cell lines that overexpress ATP‐binding cassette (ABC) transporters. While effective in in vitro assays, jadomycins have not been studied in animal models.ObjectiveTo conduct the first in animal pharmacokinetic and safety studies of jadomycins B, S, and F in male and female Balb/C mice.MethodsJadomycins were administered intraperitoneally (IP) to male and female Balb/C mice at a 6mg/kg dose. In one group of mice (n = 5) up to four repeated saphenous vein blood samples (40 mL) were obtained after 15, 30, 60, and 90 minutes with terminal blood collection occurring at 120 minutes in order to characterize absorption and distribution phases. In a second group of mice saphenous vein blood samples were obtained at 2, 4, 6, 8 and 10 hours to characterize terminal elimination. Liver, kidney, lung and brains were collected after 2 hours and then at 8 or 10 hours (males and females respectively) to characterize jadomycin distribution to these tissues. Serum and tissue samples underwent extraction and jadomycin concentrations were then determined by mass spectrometry.ResultsThe concentration versus time profiles of jadomycins B, S and F were similar. They were absorbed rapidly after IP injection with peak concentrations in the 1–10 mM range observed after 15 minutes. This was followed by a rapid distribution phase (t1/2a = 20 – 40 min) and a slower terminal elimination (t1/2b = 1.5 – 2 hours). Jadomycins accumulated in the liver > kidney > lung and were not detectable in the brain. No metabolites were detected and no acute toxicity responses were observed.ConclusionsThese 1st in vivo studies of jadomycins reveal that jadomycins are safe at a 6 mg/kg IP dose and achieve concentrations in mouse serum that are above the IC50s (1–4 μM) for human and mouse breast cancer cells in vitro. Our results indicate that jadomycins are rapidly eliminated as unchanged drug and that two to three times daily dosing will be required for future tumor studies.Support or Funding InformationCancer Research Training Program (CRTP) through Beatrice Hunter Cancer Research Institute, Canadian Breast Cancer Foundation Atlantic (CBCF), Nova Scotia Health Research Foundation (NSHRF), and Dalhousie University

Development of novel application of 3,3′-diindolylmethane: sensitizing multidrug resistance human breast cancer cells to γ-irradiation

Context: Multidrug resistance (MDR) is known as a major obstacle to effective cancer therapy. The effects of irradiation on MDR in cancer cells had rarely been reported.Objective: The effect of 3,3′-diindolylmethane (DIM) sensitizing MDR human breast carcinoma to γ-irradiation was investigated.Materials and methods: MCF-7/ADR cells were exposed to different concentrations of DIM (0–30 μM) for 48 or 2 h before IR (γ-Co60, 10 Gy, room temperature) then cultured for 48 h. Cell survival was determined by MTT assay. Intracellular reactive oxygen spices (ROS) induced by DIM (20 and 30 μM, 2 h before irradiation) was measured by flow cytometry. Propidium iodide staining assay was used for cell cycle distribution studies; cell apoptosis was measured by flow cytometry and confocal microscopy.Results: DIM (20 and 30 μM, 2 h before irradiation) sensitized MCF-7/ADR cells to IR with survival rates decreased from 100% to 79% and 63%, respectively. DIM combined with γ-radiation demonstrated that the activity of G2/M phase cell cycle arresting with percentages enhanced from 9% to 49% and 52%. DIM can increase intracellular ROS generation by 1.45- and 1.55-times compared to control group. Significantly enhanced radiation-induced apoptosis by DIM was also observed.Discussion and conclusion: These data provide a rationale for the use of DIM as a promising radio-sensitizer to MDR cancer cells.

Alisol F 24 Acetate Enhances Chemosensitivity and Apoptosis of MCF-7/DOX Cells by Inhibiting P-Glycoprotein-Mediated Drug Efflux.

Multidrug resistance (MDR) is a prime reason for numerous failed oncotherapy approaches. In the present study, we investigated whether Alisol F 24 acetate (ALI) could reverse the MDR of MCF-7/DOX cells, a multidrug-resistant human breast cancer cell line. We found that ALI was a potent P-glycoprotein (P-gp) inhibitor, in the Caco-2-monolayer cell model. ALI showed a significant and concentration-dependent cytotoxic effect on MCF-7/DOX cells in combination with doxorubicin by increasing intracellular accumulation and inducing nuclear migration of doxorubicin. However, ALI had no such effect on MCF-7 cells. In addition, ALI also promoted doxorubicin-induced early apoptosis of MCF-7/DOX cells in a time-dependent manner. These results suggest that ALI can enhance chemosensitivity of doxorubicin and reinforce its anti-cancer effect by increasing its uptake, especially inducing its nuclear accumulation in MCF-7/DOX cells. Therefore, ALI could be developed as a potential MDR-reversing agent in cancer chemotherapy in further study.

Essential oils from Inula japonica and Angelicae dahuricae enhance sensitivity of MCF-7/ADR breast cancer cells to doxorubicin via multiple mechanisms

Ethnopharmacological relevanceAngelicae dahurica (Hoffm.) Benth. & Hook.f.ex Franch. & Sav combined with Pueraria and Gastrodia elata Bl. combined with Inula japonica Thunb. are widely used in herb-pairs of traditional chinese medicine. Previous studies have shown that Angelicae dahuricae essential oil (ADO) enhanced puerarin internalization into ABCB1-overexpressed Caco-2 cells. These findings suggest the possibility that essential oils may enhance the absorption via certain mechanisms related to ABCB1 and reverse multidrug resistance (MDR). Aim of the studyADO and essential oils from Inula japonica (IJO) may reverse ABCB1-mediated MDR, but this ability has not been investigated in detail in the well-established cancer cell lines. In this study, the underlying molecular mechanisms were further investigated to examine how IJO and ADO reverse MDR in the resistant human breast cancer cell line of MCF-7/ADR. Also this work may help uncover the conceivable compatibility mechanisms of above herb-pairs involved in ABCB1. Materials and methodsThe MDR human breast cancer MCF-7/ADR cells were treated with IJO, its sesquiterpene component isoalantolactone (ISO) or ADOat non- cytotoxic concentrations. The MDR ability was examined by measuring the sensitivity to doxorubicin (DOX), DOX accumulation and efflux, ABCB1 ATPase activity, ABCB1 expression, membrane fluidity, and stability and localization of lipid rafts and caveolae. Finally, the molecular modeling was performed to postulate how ISO interacts with ABCB1. ResultsTreating MCF-7/ADR cells with IJ oil, ISO or AD oil reversed MDR 2- to 3-fold, without affecting the sensitivity of the non-MDR parental cell line. Mechanistic studies showed that these oils down-regulated mRNA and protein expression of ABCB1, and reduced the stability of lipid rafts in the cell membrane, which has previously been shown to reduce ABCB1-mediated transport. On the other hand, IJO, ISO and ADO did not inhibit ABCB1 ATPase activity, and fluorescence polarization experiments showed that low concentrations of the oils did not appear to alter membrane fluidity, unlike some MDR-reversing agents, ISO showed a higher docking score than verapamil but lower than dofequidar and tariquidar. ConclusionsOur results suggest that IJO, ISO and ADO could reverse MDR by down-regulating ABCB1 expression and reducing lipid raft stability. These findings may be useful for developing safer and effective MDR reversal agents and also help find out the compatibility mechanisms.

Elevated STAT3 Signaling-Mediated Upregulation of MMP-2/9 Confers Enhanced Invasion Ability in Multidrug-Resistant Breast Cancer Cells.

The development of multidrug resistance greatly impedes effective cancer therapy. Recent advances in cancer research have demonstrated that acquisition of multidrug resistance by cancer cells is usually accompanied by enhanced cell invasiveness. Several lines of evidence indicated that cross activation of other signaling pathways during development of drug resistance may increase invasive potential of multidrug-resistant (MDR) cancer cells. However, the accurate mechanism of this process is largely undefined. In this study, to better understand the associated molecular pathways responsible for cancer progression induced by drug resistance, a MDR human breast cancer cell line SK-BR-3/EPR with P-glycoprotein overexpression was established using stepwise long-term exposure to increasing concentration of epirubicin. The SK-BR-3/EPR cell line exhibited decreased cell proliferative activity, but enhanced cell invasive capacity. We showed that the expression of metastasis-related matrix metalloproteinase (MMP)-2/9 was elevated in SK-BR-3/EPR cells. Moreover, SK-BR-3/EPR cells showed elevated activation of STAT3. Activation of STAT3 signaling is responsible for enhanced invasiveness of SK-BR-3/EPR cells through upregulation of MMP-2/9. STAT3 is a well-known oncogene and is frequently implicated in tumorigenesis and chemotherapeutic resistance. Our findings augment insight into the mechanism underlying the functional association between MDR and cancer invasiveness.

Breast cancer targeted chemotherapy based on doxorubicin-loaded bombesin peptide modified nanocarriers

Context: Breast cancer is the most common cancer in female population. Breast cancer chemotherapy using doxorubicin (DOX) is well illustrated. However, a significant obstacle for successful chemotherapy with DOX is multidrug resistant (MDR) in breast cancer cells. Targeted nanocarriers have emerged as frontier research for the improvement of cancer chemotherapy.Objective: Bombesin (Bn)-modified, DOX-loaded solid lipid nanoparticles (Bn-DOX/SLNs) were constructed. Doxorubicin-resistant MCF-7/MDR human breast cancer cells and the cancer animal models were applied for the evaluation of the in vitro and in vivo anti-tumor effect of Bn-DOX/SLNs.Methods: Bn-conjugated lipids were synthesized. DOX was then loaded into Bn-modified SLNs. The physicochemical properties of the Bn-DOX/SLNs were investigated by particle size and zeta potential measurement, drug loading and drug-entrapment efficiency, and in vitro drug release behavior. In vitro cytotoxicity against MCF-7/MDR cells was investigated, and in vivo anti-tumor of SLNs was evaluated in human breast cancer mice models.Results: Bn-DOX/SLNs showed an excellent in vitro cytotoxicity and in vivo anti-tumor effect both in MCF-7/MDR breast cancer cells and breast cancer animal model.Conclusion: The results demonstrated that Bn-DOX/SLNs reversed the resistance of doxorubicin, suggesting that chemotherapy using this kind of targeted nanocarriers may benefit human breast MDR cancer therapy.

IF7-Conjugated Nanoparticles Target Annexin 1 of Tumor Vasculature against P-gp Mediated Multidrug Resistance

Multidrug resistance is the main cause of clinical chemotherapeutic failure. Antiangiogenic cancer therapy with nanomedicine that allows the targeted delivery of antiangiogenic agents to tumor endothelial cells may contribute to innovative strategies for treating multidrug-resistant cancers. In this study, we developed a new nanodrug delivery system (nano-DDS), with improved antiangiogenic efficacy against multidrug resistant human breast cancer MCF-7/ADR cells. Here, the IF7 ligand was a peptide designed to bind the annexin 1 (Anxa 1), a highly specific marker of the tumor vasculature surface, with high affinity and specificity. IF7-conjugated Anxa 1-targeting nanoparticles containing paclitaxel (IF7-PTX-NP) allowed controlled drug release and displayed favorable prolonged circulation in vivo. IF7-PTX-NP was significantly internalized by human umbilical vein endothelial cells (HUVEC) through the IF7-Anxa 1 interaction, and this facilitated uptake enhanced the expected antiangiogenic activity of inhibiting HUVEC proliferation, migration, and tube formation in a Matrigel plug relative to those of Taxol and PTX-NP. As IF7-PTX-NP targeted the tumor vessels, more nanoparticles accumulated in MCF-7/ADR tumors, and more importantly, induced significant apoptosis of the tumor vascular endothelial cells and necrosis of the tumor tissues. Low dose paclitaxel (1 mg/kg) formulated in IF7-PTX-NP showed significant anticancer efficacy, delaying the growth of MCF-7/ADR tumors. The same efficacy was only obtained with an 8-fold dose of paclitaxel (8 mg/kg) as Taxol plus XR9576, a potent P-gp inhibitor. The anticancer efficacy of IF7-PTX-NP was strongly associated with the improved antiangiogenic effect, evident as a dramatic reduction in the tumor microvessel density and pronounced increase in apoptotic tumor cells, with no obvious toxicity to the mice. This nano-DDS, which targets the tumor neovasculature, offers a promising strategy for the treatment of multidrug-resistant cancer.

Salinomycin enhances doxorubicin-induced cytotoxicity in multidrug resistant MCF-7/MDR human breast cancer cells via decreased efflux of doxorubicin.

Salinomycin is a monocarboxylic polyether antibiotic, which is widely used as an anticoccidial agent. The anticancer property of salinomycin has been recognized and is based on its ability to induce apoptosis in human multidrug resistance (MDR). The present study investigated whether salinomycin reverses MDR towards chemotherapeutic agents in doxorubicin-resistant MCF-7/MDR human breast cancer cells. The results demonstrated that doxorubicin-mediated cytotoxicity was significantly enhanced by salinomycin in the MCF-7/MDR cells, and this occurred in a dose-dependent manner. This finding was consistent with subsequent observations made under a confocal microscope, in which the doxorubicin fluorescence signals of the salinomycin-treated cells were higher compared with the cells treated with doxorubicin alone. In addition, flow cytometric analysis revealed that salinomycin significantly increased the net cellular uptake and decreased the efflux of doxorubicin. The expression levels of MDR-1 and MRP-1 were not altered at either the mRNA or protein levels in the cells treated with salinomycin. These results indicated that salinomycin was mediated by its ability to increase the uptake and decrease the efflux of doxorubicin in MCF-7/MDR cells. Salinomycin reversed the resistance of doxorubicin, suggesting that chemotherapy in combination with salinomycin may benefit MDR cancer therapy.

CD44-engineered mesoporous silica nanoparticles for overcoming multidrug resistance in breast cancer

Multidrug resistance is a major impediment for the successful chemotherapy in breast cancer. CD44 is over-expressed in multidrug resistant human breast cancer cells. CD44 monoclonal antibody exhibits anticancer potential by inhibiting proliferation and regulating P-glycoprotein-mediated drug efflux activity in multidrug resistant cells. Thereby, CD44 monoclonal antibody in combination with chemotherapeutic drug might be result in enhancing chemosensitivity and overcoming multidrug resistance. The purpose of this study is to investigate the effects of the CD44 monoclonal antibody functionalized mesoporous silica nanoparticles containing doxorubicin on human breast resistant cancer MCF-7 cells. The data showed that CD44-modified mesoporous silica nanoparticles increased cytotoxicity and enhanced the downregulation of P-glycoprotein in comparison to CD44 antibody. Moreover, CD44-engineered mesoporous silica nanoparticles provided active target, which promoted more cellular uptake of DOX in the resistant cells and more retention of DOX in tumor tissues than unengineered counterpart. Animal studies of the resistant breast cancer xenografts demonstrated that CD44-engineered drug delivery system remarkably induced apoptosis and inhibited the tumor growth. Our results indicated that the CD44-engineered mesoporous silica nanoparticle-based drug delivery system offers an effective approach to overcome multidrug resistance in human breast cancer.

Germacrone reverses Adriamycin resistance through cell apoptosis in multidrug-resistant breast cancer cells.

Multidrug resistance (MDR) is a major obstacle to the chemotherapeutic treatment of breast cancer. Germacrone, the main component of Rhizoma Curcuma, has been shown to possess antitumor, anti-inflammatory and immunomodulatory properties. The aim of the present study was to investigate the effect of germacrone on MCF-7/Adriamycin (ADR) multidrug-resistant human breast cancer cells. The treatment of MCF-7/ADR cells with a combination of germacrone and ADR resulted in an increase in cytotoxicity compared with that of ADR alone, as determined using an MTT assay. Flow cytometric analysis revealed that germacrone promoted cell apoptosis in a dose-dependent manner, whilst treatment with germacrone plus ADR enhanced the apoptotic effect synergistically. Furthermore, the results from the western blot analysis demonstrated that augmenting ADR treatment with germacrone resulted in a reduction of anti-apoptotic protein expression levels (bcl-2) and enhancement of pro-apoptotic protein expression levels (p53 and bax) in MCF-7/ADR cells compared with the levels achieved by treatment with ADR alone. In addition, germacrone significantly reduced the expression of P-glycoprotein via the inhibition of the multidrug resistance 1 (MDR1) gene promoter. These findings demonstrate that germacrone has a critical role against MDR and may be a novel MDR reversal agent for breast cancer chemotherapy.

Reversal of doxorubicin resistance by guggulsterone of Commiphora mukul in vivo

Our previous study has shown co-administration of guggulsterone resulted in significant increase in chemosensitivity of multidrug-resistant human breast cancer MCF-7/DOX cells to doxorubicin (DOX) in vitro. The present study was designed to investigate whether guggulsterone had the similar modulatory activities in vivo. MCF-7/DOX and MCF-7 xenograft mice models were established. At the end of the experiment (day 28), doxorubicin treatment alone did not significantly inhibit tumor growth in MCF-7/DOX xenograft, indicating that it retained doxorubicin resistance. Whereas, doxorubicin treatment alone significantly inhibited tumor growth in MCF-7 xenograft, suggesting that it maintained doxorubicin sensitivity. When doxorubicin and guggulsterone were co-administrated, their antitumor activities were augmented in MCF-7/DOX xenograft. However, combination therapy did not enhance the antitumor effects of doxorubicin in MCF-7 xenograft. The expression of proliferative cell nuclear antigens PCNA and Ki67 after doxorubicin treatment alone was not significantly different from that of vehicle group in MCF-7/DOX xenograft. On the contrary, doxorubicin treatment alone significantly reduced PCNA and Ki67 expression in MCF-7 xenograft. Combination therapy also significantly reduced PCNA and Ki67 expression in MCF-7/DOX xenograft, compared to doxorubicin treatment alone. However, combination therapy did not enhance the inhibitory effects of doxorubicin on PCNA and Ki67 expression in MCF-7 xenograft. Examining the apoptotic index by TUNEL assay showed similar results. Further studies demonstrated the inhibitory effects of guggulsterone on Bcl-2 and P-glycoprotein expression were the possible reason to increase chemosensitivity of MCF-7/DOX cells to doxorubicin in vivo. Examining body weight, hematological parameters, hepatic, cardiac and gastrointestinal tracts histopathology revealed that no significant signs of toxicity were related to guggulsterone. Guggulsterone might reverse doxorubicin resistance in vivo, with no severe side effects.

Doxorubicin induces drug resistance and expression of the novel CD44st via NF-κB in human breast cancer MCF-7 cells

CD44, a major receptor for hyaluronan (HA), is a member of a class of adhesion molecules of unknown classification involved in cell proliferation, differentiation, migration, angiogenesis, and the presentation of specific cytokines to the corresponding receptors as well as in cell signaling transduction. It has recently been discovered that CD44, a marker of tumor stem cells, is involved in the drug resistance and invasion of multiple types of tumors. The 20exons in the CD44 gene that are alternatively spliced, give rise to many CD44 isoforms, possibly including tumor-specific sequences. Dozens of CD44 isoforms have been found, to date, and the standard CD44 (CD44s) isoform is the most common. We recently showed that a novel short-tail isoform of CD44 (CD44st) was expressed in multidrug-resistant human breast cancer MCF-7/Adr cells. Moreover, the novel CD44st was able to interact with HA and regulate the expression of matrix metalloproteinase (MMP)-2 and MMP-9, which increased the invasive capability of MCF-7 cells through the Ras/MAPK signaling pathway. In the present study, we verified that MCF-7 cells subjected to drug pressure develop multidrug resistance to doxorubicin, and the expression levels of multidrug resistance protein1 (MDR1), CD44st and nuclear factor-κB (NF-κB) mRNA and protein were gradually upregulated in a dose‑dependent manner in MCF-7 cells treated with doxorubicin. HA increases the secretion of MMP-2 and MMP-9 in multidrug-resistant MCF-7 cells and affected the invasive ability of MCF-7 cells through the upregulation of CD44st expression, and such an effect was blocked by the NF-κB-specific inhibitor BMS-345541.