Treatment Of Multidrug-resistant Tumors Research Articles

Overexpression of Glutathione S-Transferases in Human Diseases: Drug Targets and Therapeutic Implications.

Glutathione S-transferases (GSTs) are a major class of phase II metabolic enzymes. Besides their essential role in detoxification, GSTs also exert diverse biological activities in the occurrence and development of various diseases. In the past few decades, much research interest has been paid to exploring the mechanisms of GST overexpression in tumor drug resistance. Correspondingly, many GST inhibitors have been developed and applied, solely or in combination with chemotherapeutic drugs, for the treatment of multi-drug resistant tumors. Moreover, novel roles of GSTs in other diseases, such as pulmonary fibrosis and neurodegenerative diseases, have been recognized in recent years, although the exact regulatory mechanisms remain to be elucidated. This review, firstly summarizes the roles of GSTs and their overexpression in the above-mentioned diseases with emphasis on the modulation of cell signaling pathways and protein functions. Secondly, specific GST inhibitors currently in pre-clinical development and in clinical stages are inventoried. Lastly, applications of GST inhibitors in targeting cell signaling pathways and intracellular biological processes are discussed, and the potential for disease treatment is prospected. Taken together, this review is expected to provide new insights into the interconnection between GST overexpression and human diseases, which may assist future drug discovery targeting GSTs.

A Dual Concentration-Tailored Cytokine-Chemo Nanosystem to Alleviate Multidrug Resistance and Redirect Balance of Cancer Proliferation and Apoptosis.

Cancer multidrug resistance (MDR) is an important factor that severely affects the chemotherapeutic efficacy. Among various methods to bypass MDR, usage of cytokines, such as tumor necrosis factor alpha (TNFα) is attractive, which exerts antitumor effects of immunotherapeutic response and apoptotic/proinflammatory pathways. Nevertheless, the challenges remain how to implement targeted delivery of TNFα to reduce toxicity and manifest the involved signaling mechanism that subdues MDR. We synthesized a multifunctional nanosytem, in which TNFα covalently bound to doxorubicin (Dox)-loaded pH-responsive mesoporous silica nanoparticles (MSN) through bi-functional polyethylene glycol (TNFα-PEG-MSN-Hydrazone-Dox) as a robust design to overcome MDR. The salient features of this nanoplatform are: 1) by judicious tailoring of TNFα concentration conjugated on MSN, we observed it could lead to a contrary effect of either proliferation or suppression of tumor growth; 2) the MSN-TNFα at higher concentration serves multiple functions, besides tumor targeting and inducer of apoptosis through extrinsic pathway, it inhibits the expression level of p-glycoprotein (P-gp), a cell membrane protein that functions as a drug efflux pump; 3) the enormous surface area of MSN provides for TNFα functionalization, and the nanochannels accommodate chemotherapeutics, Dox; 4) targeted intracellular release of Dox through the pH-dependent cleavage of hydrazone bonds induces apoptosis by the specific intrinsic pathway; and 5) TNFα-PEG-MSN-Hydrazone-Dox (MSN-Dox-TNFα) could infiltrate deep into the 3D spheroid tumor model through disintegration of tight junction proteins. When administered intratumorally in a Dox-resistant mouse tumor model, MSN-Dox-TNFα exhibited a synergistic therapeutic effect through the collective performances of TNFα and Dox. We hereby develop and demonstrate a multifunctional MSN-Dox-TNFα system with concentration-tailored TNFα that can abrogate the drug resistance mechanism, and significantly inhibit the tumor growth through both intrinsic and extrinsic apoptosis pathways, thus making it a highly potential nanomedicine translated in the treatment of MDR tumors.

PX478-loaded silk fibroin nanoparticles reverse multidrug resistance by inhibiting the hypoxia-inducible factor

Multidrug resistance (MDR) is the main cause of clinical chemotherapy failure, and new strategies to overcome MDR are needed. We report multi-responsive silk fibroin nanoparticles (SFNs) co-loaded with the chemotherapeutic drug doxorubicin (DOX) and PX478 (a hypoxia-inducible factor inhibitor), which was functionalized with folic acid (FA). This combination could actively target tumor cells and respond to the release of PX478, inhibit the hypoxia-inducible factor (HIF) gene and its related downstream drug-resistant target genes. The FA-PX478-DOX-SFNs (F-P-D-S) combination showed accelerated drug release profiles in the media simulating the tumor microenvironment, which had acidic pH, high levels of reactive oxygen species and high levels of glutathione. Compared with PX478-DOX-SFNs (P-D-S) without targeted modification, the cellular uptake rate of F-P-D-S increased. In addition, F-P-D-S quickly achieved lysosomal escape, enabling DOX to rapidly enter the nucleus to kill the drug-resistant cells. A cytotoxicity test indicated that the IC50 of DOX against MCF-7/ADR cells was 1.0 μg/mL in F-P-D-S, which was 26 times lower than that of free DOX (25.6 μg/mL). F-P-D-S significantly down-regulated HIF-1α, MDR1, VEGF and GLUT-1 and P-gp protein to overcome multidrug resistance. This effective synergistic chemotherapy strategy for HIF inhibition has potential for use in the treatment of multidrug-resistant tumors.

Medicinal plants and phytochemicals against multidrug-resistant tumor cells expressing ABCB1, ABCG2, or ABCB5: a synopsis of 2 decades

Multidrug resistance is a major factor causing the failure of cancer chemotherapy. Efflux pumps of the ATP-binding cassette (ABC) transporter family expel a large array of diverse anticancer drugs out of tumor cells thereby rendering them unresponsive to drug treatment. During the past 2 decades, we focused on three ABC transporters, i.e. P-glycoprotein (MDR1/ABCB1), breast cancer resistance protein (BCRP/ABCG2), and ABCB5 with the aim to find natural products with activity against multidrug-resistant cells. We investigated more than 102 cytotoxic medicinal plants and more than 228 isolated cytotoxic phytochemicals with defined chemical structures from 16 countries in Africa, Near East, Asia, and Europe for their activity to kill multidrug-resistant cells. A synopsis of these results is given in this review article. ABCB1-, ABCG2- or ABCB5-expressing cells were moderately or strongly cross-resistant to a considerable portion of plant extracts or phytochemicals, making them less suitable for the treatment of multidrug resistant tumors. While another large portion of compounds inhibited sensitive and multidrug-resistant cells with similar efficacy, a small fraction of medicinal plants and phytochemicals (3–8%) suppressed multidrug-resistant cells with even much better efficacy as their drug-sensitive counterparts. This hypersensitivity phenomenon is termed “collateral sensitivity”. These compounds may be exquisitely suited to kill otherwise resistant and refractory tumors. Molecular modes of action of collateral sensitivity as well as possibilities for further drug development, chemical derivatization of natural lead compounds and rationale phytotherapy are discussed.

Repurposing old drugs to fight multidrug resistant cancers.

Overcoming multidrug resistance represents a major challenge for cancer treatment. In the search for new chemotherapeutics to treat malignant diseases, drug repurposing gained a tremendous interest during the past years. Repositioning candidates have often emerged through several stages of clinical drug development, and may even be marketed, thus attracting the attention and interest of pharmaceutical companies as well as regulatory agencies. Typically, drug repositioning has been serendipitous, using undesired side effects of small molecule drugs to exploit new disease indications. As bioinformatics gain increasing popularity as an integral component of drug discovery, more rational approaches are needed. Herein, we show some practical examples of in silico approaches such as pharmacophore modelling, as well as pharmacophore- and docking-based virtual screening for a fast and cost-effective repurposing of small molecule drugs against multidrug resistant cancers. We provide a timely and comprehensive overview of compounds with considerable potential to be repositioned for cancer therapeutics. These drugs are from diverse chemotherapeutic classes. We emphasize the scope and limitations of anthelmintics, antibiotics, antifungals, antivirals, antimalarials, antihypertensives, psychopharmaceuticals and antidiabetics that have shown extensive immunomodulatory, antiproliferative, pro-apoptotic, and antimetastatic potential. These drugs, either used alone or in combination with existing anticancer chemotherapeutics, represent strong candidates to prevent or overcome drug resistance. We particularly focus on outcomes and future perspectives of drug repositioning for the treatment of multidrug resistant tumors and discuss current possibilities and limitations of preclinical and clinical investigations.

The effective treatment of multi-drug resistant tumors with self-assembling alginate copolymers

Alginates of two different chain lengths were alkyne functionalized on the hydroxyl group, leaving all carboxylic groups intact.

Technetium and Rhenium Schiff Base Compounds for Nuclear Medicine: Syntheses of Rhenium Analogues to 99mTc-Furifosmin.

Rhenium, the third-row congener of technetium, is often used to develop the macroscopic chemistry of potential 99mTc diagnostic radiopharmaceuticals. The rhenium analogues to 99mTc-furifosmin are being developed for potential radiotherapy of multidrug-resistant tumors. Complexes of the form trans-[MIII(PR3)2(N2O2-Schiff base)]+ are of interest for the potential imaging and treatment of multidrug-resistant tumors. Reaction of the tetradentate Schiff ligand 4,4'-[(1 E,1' E)-[ethane-1,2-diylbis(azanylylidene)]bis(methanylylidene)]bis(2,2,5,5-tetramethyl-2,5-dihydrofuran-3-ol) (tmf2enH2) with the M(V) starting materials ( nBu4N)[TcOCl4] and ( nBu4N)[ReOCl4] gave the monomeric products trans-[TcOCl(tmf2en)] and trans-[ReOCl(tmf2en)], respectively. Reduction of in situ formed trans-[ReOCl(tmf2en)] by various tertiary phosphines yielded disubstitued Re(III) products of the general type trans-[ReIII(PR3)2(tmf2en)]+. The rhenium(III) compounds were found to be water-soluble and stable in aqueous solution. Reversible ReIII/ReIV and ReIII/ReII redox processes were observed at about 0.8-0.9 and -0.65 to -0.8 V, respectively, for each of the rhenium(III) species. Reaction of in situ formed trans-TcOCl(tmf2en) with triethylphosphine yielded the reduced, disubstituted trans-[Tc(PEt3)2(tmf2en)]PF6. A reversible TcIII/TcII redox couple was observed for the technetium(III) species, about 200 mV less negative than their rhenium(III) analogues, in addition to an irreversible TcIII/TcIV process. All compounds were characterized using conventional spectroscopic techniques, single-crystal X-ray crystallography, and cyclic voltammetry.

Abstract 4851: Potent cell cycle inhibitors suitable for treatment of multidrug-resistant tumors

Abstract We have developed a class of small-molecule cytotoxic compounds that are highly potent in an in vitro tubulin polymerization assay. Preclinical studies show that these drug candidates are potent against a range of cancer cell lines and may be well suited for the treatment of hematologic or solid tumors resistant to existing chemotherapy agents. We will present data on representative members of this class that inhibit cancer cell growth at nanomolar concentrations and are potent against a variety of cancer cell lines, including liver, breast, ovarian, and lung. The compounds induce cell cycle arrest in the G2M state within 24 hours with cell death occurring over multiple days. These tubulin inhibitors also behave as potent antiangiogenesis agents and inhibit endothelial tube formation in HUVEC cells at nanomolar concentrations. Functional assays using efflux pump inhibitors show that, compared to many major chemotherapy agents, our class of drug candidates is significantly less affected by the efflux pumps MDR1 and MRP1, which are commonly overexpressed as a mechanism of multidrug resistance. Our compounds show comparable potency against wild-type and cell lines developed to be resistant to other cancer drugs, while the potency of clinically relevant compounds such as paclitaxel or doxorubicin is reduced between 80x and about 3000x in the same assay. This feature suggests that our tubulin inhibitors may be active against tumors that are resistant to common cancer drugs. Overexpression of the β-III isotype of tubulin, which is known to occur in many aggressive and metastatic tumors, is another clinically relevant mechanism of resistance to microtubule-targeting anticancer agents. It has been correlated with significantly lower response to docetaxel-based chemotherapy in a number of cancers and is considered an indicator of resistance to paclitaxel and vinorelbine. We will present preclinical data showing that our compounds have similar activity against cells showing normal levels and those highly overexpressing β-III tubulin. The compounds display good in vitro physicochemical properties as well as favorable in vivo pharmacokinetics. In addition, we will present in vivo tolerability and efficacy data in mice. The ability of this class of tubulin inhibitors to maintain their efficacy across multiple drug-resistant cancer cell lines makes them attractive candidates for development as chemotherapy agents. In particular, a new anticancer agent that is less susceptible to major transporters and retains its potency when β-III tubulin is overexpressed could lead to more effective precision second-line therapy. Citation Format: Mohan Sivaraja, Sivan Sizikov, Nilantha Sirisoma, Tamari Kirtadze, Madhuri Chattopadhyay, Makena Ewald, Subhadra Dash, Anne Wong, Georg Neckermann, Elaine To, Stephanie Chang, Timothy P. Shiau, David C. Williams, Kevin M. Short, Angels Estiarte, Anirban Datta, David B. Kita. Potent cell cycle inhibitors suitable for treatment of multidrug-resistant tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4851.

Targeted Delivery of Cabazitaxel by Conjugation to Albumin-PEG-folate Nanoparticles Using a Cysteine-acrylate Linker and Simple Synthesis Conditions.

Cabazitaxel (CBZ) is a new taxane approved by FDA for treatment of castration- resistant prostate cancer not responding to docetaxel. However, CBZ is not a suitable substrate for p-glycoprotein 60, an efflux pump which transports anticancer drugs out of malignant cells and is therefore a promising drug for treatment of multidrug resistant tumors. Similar to other taxanes, the presence of Tween 80 in the CBZ formulation shows that it is insoluble in water. In order to increase the solubility and circulation time of this drug, CBZ-human serum albumin (HSA) conjugate was synthesized. The designed linker was composed of methacrylic acid and N-acetyl cysteine to increase the solubility of CBZ and to increase the efficiency of conjugation. Targeting was performed by poly(ethylene glycol)-folic acid amide bound formation with carboxyl groups of HSA during in the step of nanoparticle formation. Cytotoxicity of nanoparticles was evaluated in vitro on HT-29, as a folate negative cell line, and MDA-MB-231, as a folate positive cell line. H-NMR, Gel Permeation Chromatography, High Pressure Liquid Chromatography and UV spectrophotometry analysis confirmed the composition of conjugates. The resulting nanoparticles had a spherical shape, narrow size distribution and mean diameter of 138 nm. The efficiency of conjugation was 41.6 %. The IC50 of CBZ in targeted nanoparticles was 10.1 and 17.4% lower than that of the free CBZ for HT-29 and MDA-MB-231 cells, respectively. This designed drug delivery system was more water-soluble and had enhanced in vitro characteristics and higher cytotoxic activity on cancer cells.

Cremophor EL Alters the Plasma Protein Binding and Pharmacokinetic Profile of Valspodar in Rats.

Cremophor EL is a nonionic surfactant widely used in pharmaceutical formulations. Nonetheless, there are several reports on the influence of this excipient on the protein binding, pharmacokinetics, and pharmacodynamics of drugs. Valspodar is an investigational non-immunosuppressive derivative of cyclosporine A, used in clinical trials for treatment of multidrug resistant tumors. The formulation of valspodar (Amdray®) contains cremophor EL and ethanol as solubilizing agents. The main aim of the current study was to assess the plasma protein binding (in vitro) and the pharmacokinetic profile of valspodar in the cremophor EL-based formulation in comparison to a cremophor EL-free formulation following intravenous (i. v.) administration to rats. Valspodar dissolved in PEG 400/ethanol (diluted in Dextrose 5%) was used as the cremophor EL-free formulation. The in vitro plasma unbound fraction (f u) of valspodar in the cremophor EL formulation was 2.3-fold higher than the PEG 400/ethanol formulation. Following a single i. v. dose of 5 mg/kg, valspodar in the cremophor EL-based formulation had around 50% lower plasma AUC compared to the PEG 400/ethanol formulation. Moreover, the cremophor EL formulation had significantly higher volume of distribution and clearance in comparison to the PEG 400-based formulation. The results highlight the significance of excipient-drug interaction that should not be overlooked during the early stages of drug development.

A novel compound RY10-4 downregulates P-glycoprotein expression and reverses multidrug-resistant phenotype in human breast cancer MCF-7/ADR cells

P-glycoprotein (P-gp), an important efflux transporter, is encoded by the MDR1 class of genes and is a major element of the multidrug resistance (MDR) phenomenon in breast cancers. The most common approved cause of MDR in cancer tissues is the over-expression of P-gp. At present, a novel potent anti-tumor compound RY10-4 has been synthesized by our team, which has a similar structure close to protoapigenone. We chose MCF-7/ADR cells, an adriamycin (ADR) – selected human breast tumor cell line with the MDR phenotype, to study the anticancer features of this novel compound in our experiments. In cytotoxicity and apoptosis tests, it was shown that RY10-4 significantly inhibited cell growth, induced apoptosis, potentiated ADR cytotoxicity and restored chemotherapy sensitivity in the MDR cancer cells. Furthermore, our results suggested that RY10-4 reversed MDR partially by down-regulation of P-gp and MDR1 expressions in the MCF-7/ADR cell line. Besides, it is seen that RY10-4 could reduce the intracellular ATP level. Our studies give the theoretical basis for the possible clinical applications of RY10-4 alone or in combination with other chemotherapeutic drugs in the treatment of MDR tumors.

D-α-tocopherol polyethylene glycol succinate-based redox-sensitive paclitaxel prodrug for overcoming multidrug resistance in cancer cells.

To overcome the multidrug resistance (MDR) of P-glycoprotein (P-gp) substrate anticancer drugs, such as paclitaxel (PTX), a novel dual-functional prodrug, D-α-tocopherol polyethylene glycol succinate (TPGS) based PTX prodrug (TPGS-S-S-PTX), was synthesized here to fulfill the synergistic effect of P-gp inhibiting and intracellular redox-sensitive release. The prodrug could self-assemble into stable micelles in physiological environment with a diameter of ∼140 nm, while it disassociated in reductive condition and released PTX and TPGS active derivatives rapidly. High cell cytotoxicity in PTX-resistant human ovarian cell line A2780/T was observed with enhanced PTX accumulation due to the P-gp inhibition by the TPGS moiety. The IC50 of TPGS-S-S-PTX was 55% and 91% more effective than that of Taxol (clinical formulation of PTX) and uncleavable TPGS-C-C-PTX prodrug, respectively. This was found to be related with the increased apoptosis/necrosis and cell arrest in G2/M phase. In vivo evaluation of the TPGS-S-S-PTX prodrug exhibited an extended half-life, increased AUC (area under the concentration-time curve), enhanced tumor distribution and significant tumor growth inhibition with reduced side effects as compared to Taxol and TPGS-C-C-PTX. This prodrug has great potential in improving efficiency in the treatment of MDR tumors.

Drug-loaded gold plasmonic nanoparticles for treatment of multidrug resistance in cancer

To investigate the possibility of treating multidrug-resistant tumors with targeted chemo-photothermal treatment, we conducted in vitro and in vivo studies using a doxorubicin (DOX)-resistant DLD-1 cell line (DLD-1/DOX) and nude mice with human xenograft tumors, respectively. The chemo-photothermal treatment consisted of DOX-loaded-poly(lactic-co-glycolic acid)–Au half-shell nanoparticles with targeting moieties of anti-death receptor-4 monoclonal antibody conjugated to the Au surface. The cells or xenografted tumors treated with nanoparticles were exposed to near infrared light for 10 min, which caused an increase in temperature to 45 °C. Chemo-photothermal treatment resulted in a large reduction in the rate of tumor xenograft growth on DLD-1/DOX tumor-bearing mice with a much smaller dose of DOX than conventional DOX chemotherapy. These results demonstrate that targeted chemo-photothermal treatment can provide high therapeutic efficacy and low toxicity in the treatment of multidrug-resistant tumors.

Effects of 3β-Acethyl Tormentic Acid (3ATA) on ABCC Proteins Activity

Multidrug resistance (MDR) is considered the main cause of cancer chemotherapy failure and patient relapse. The active drug efflux mediated by transporter proteins of the ABC (ATP-binding cassette) family is the most investigated mechanism leading to MDR. With the aim of inhibiting this transport and circumventing MDR, a great amount of work has been dedicated to identifying pharmacological inhibitors of specific ABC transporters. We recently showed that 3β-acetyl tormentic acid (3ATA) had no effect on P-gp/ABCB1 activity. Herein, we show that 3ATA strongly inhibited the activity of MRP1/ABCC1. In the B16/F10 and Ma104 cell lines, this effect was either 20X higher or similar to that observed with MK571, respectively. Nevertheless, the low inhibitory effect of 3ATA on A549, a cell line that expresses MRP1-5, suggests that it may not inhibit other MRPs. The use of cells transfected with ABCC2, ABCC3 or ABCC4 showed that 3ATA was also able to modulate these transporters, though with an inhibition ratio lower than that observed for MRP1/ABCC1. These data point to 3ATA as a new ABCC inhibitor and call attention to its potential use as a tool to investigate the function of MRP/ABCC proteins or as a co-adjuvant in the treatment of MDR tumors.

Up‐regulation of CD147 and matrix metalloproteinase‐2, ‐9 induced by P‐glycoprotein substrates in multidrug resistant breast cancer cells

Treatment of animals bearing multidrug resistant (MDR) tumor cells with P-glycoprotein (P-gp) substrates could worsen host survival. It is assumed that this is due to increased tumor metastasis. To clarify the mechanism(s) underlying this observation, the MDR human breast cancer cell line, MCF-7/AdrR, and its sensitive parental line, MCF-7, was treated with various concentrations of P-gp substrate drugs (vincristine, paclitoxel, adriamycin) and a P-gp non-substrate drug (bleomycin) in serum-free media. Increased production of CD147, and matrix metalloproteinases (MMP)-2, -9 was observed only in MDR cancer cells exposed to P-gp substrates, as determined using real-time polymerase chain reaction, western blotting and zymography. Correspondingly, P-gp substrates significantly enhanced the in vitro invasion abilities of MCF-7/Adr cells. It was also found that the drug-induced promotion of CD147, and MMP-2, -9 was consistent with increased expression of epidermal growth factor receptor (EGFR) and that inhibition of either EGFR or P-gp activity could significantly interrupt the downstream effects, and so inhibit in vitro invasion abilities motivated by P-gp substrates. These results imply that treatment of MDR tumors with P-gp substrates could adversely affect therapeutic outcomes through modulating the production of CD147, MMP-2, -9, and EGFR, and suggest that this effect may be initiated by the transporter function of P-gp.

Strategies for Inhibition of P-Glycoproteins for Effective Treatment of Multidrug Resistance Tumors

Strategies for Inhibition of P-Glycoproteins for Effective Treatment of Multidrug Resistance Tumors

In vitro and in vivo evaluation of WK‐X‐34, a novel inhibitor of P‐glycoprotein and BCRP, using radio imaging techniques

Overexpression of the multidrug resistance proteins P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) results in treatment failure of many malignancies including ovarian cancer. Dual inhibition of Pgp and BCRP may restore the sensitivity of resistant cells to anticancer drugs. We report the synthesis and characterization of a novel anthranilic-acid based Pgp and BCRP modulator, WK-X-34. In vitro inhibition of Pgp activity was evaluated using 99mTc-Sestamibi and daunorubicin accumulation in Pgp overexpressing human ovarian cancer cells (A2780/Adr) and its sensitive counterpart (A2780/wt). Interaction with BCRP was examined with a mitoxantrone-efflux assay in BCRP-overexpressing MCF7/mx cells, with flow cytometry. Interactions with the multidrug resistance associated proteins (MRP) were evaluated in transfected MRP1, MRP2 and MRP3 cell lines, using a 5-CFDA efflux assay. In vivo 99mTc-Sestamibi imaging of human ovarian cancer xenografts was used to evaluate the in vivo efficacy of WK-X-34 in mice. Daunorubicin accumulation in A2780/Adr cells was inhibited by WK-X-34 at nanomolar concentrations (IC50: 82.1 +/- 6 nM). WK-X-34 inhibited mitoxantrone accumulation in BCRP-overexpressing cells at micromolar concentrations (IC50 = 26.5 +/- 4.6 microM), whereas WK-X-34 did not significantly alter 5-CFDA accumulation in MRP transfected cells. In vivo, uptake of 99mTc-Sestamibi was significantly increased in A2780/Adr xenograft tumors, brain and intestine (AUCs(0-4h) 136%, 147% and 138%; p < 0.05) in mice dosed with WK-X-34 (20 mg/kg i.p.). WK-X-34 selectively modulates Pgp and BCRP in vitro and in vivo in multidrug resistant ovarian cancer cells, and thus may have potential utility in the treatment of multidrug resistant tumors.

YM-231146, a Novel Orally Bioavailable Inhibitor of Vascular Endothelial Growth Factor Receptor-2, Is Effective against Paclitaxel Resistant Tumors

Chemotherapy using anticancer drugs induces serious the problem of multidrug resistance (MDR) in the cancer cells. In contrast, endothelial cells so rarely acquire MDR that antiangiogenesis therapy has recently been considered as an effective means for cancer chemotherapy. We screened compounds in the chemical library to find a novel and orally active antitumor agent with vascular endothelial growth factor receptor-2 tyrosine kinase (VEGF-R2 TK) inhibition. The result was YM-231146 (IC50=0.080 microM). YM-231146 inhibited VEGF-stimulated proliferation, VEGF-R2 autophosphorylation, and vessel sprout formation of human vascular endothelial cells at concentrations between 0.15-0.30 microM. However, YM-231146 did not inhibit cancer cell proliferation at these concentrations (IC50>5 microM). In the in vivo studies, once-daily oral dosing of YM-231146 to human cancer xenografts elicited antitumor activity at doses of 3-100 mg/kg. Moreover, YM-231146 completely inhibited tumor growth of paclitaxel-resistant cancer cells without decreasing body weight at a dose of 100 mg/kg. These results suggest that YM-231146 is a novel orally bioavailable inhibitor of VEGF-R2 that would be useful for the treatment of multidrug resistant tumors.

Aglycone Protopanaxadiol, a ginseng saponin inhibits P-glycoprotein and sensitizes chemotherapy drugs on multidrug resistant cancer cells

9663 Background:Aglycone Protopanaxadiol (aPPD) is an aglycone derivative of ginseng saponins. Our previous work showed that a natural ginseng product CARESENG™ containing mainly aPPD induced cell apoptosis through various signal pathways including caspases. CARESENG™ also enhances the sensitivity of multidrug resistant cancer cells to various chemotherapy drugs. P-glycoprotein (P-gp, MDR1) is one of the major causes of multidrug resistance of many tumor cells. Blocking the function of P-gp may enhance efficacy of chemotherapy. In the present study, we investigated the possible mechanism of chemosensitizing effect of purified aPPD compound as well as CARESENG™. Methods:Breast cancer cell MCF-7adr and leukemia cell line P388adr, both overexpressing P-gp, were used to test the interaction between the compound and P-gp. Calcein-AM, a P-gp substrate, efflux assay was used to measure function of P-gp. Membrane preparation was also used to measure the ATPase activity of P-gp in the presence of aPPD or verapamil. Results:Our results demonstrated that 70uM aPPD could significantly block P-gp function on both MCF-7adr and P388adr cells showing increased intracellular concentrations of calcein-AM. Furthermore, the maximum effects of aPPD and verapamil on P-gp inhibition was additive when treated together on P388adr cells. On the other hand, aPPD had no effect on ATPase activity of P-gp while verapamil increased it by more than 2-fold. 20uM of aPPD completely reversed P-gp induced drug resistant to Taxol or Doxorubicin on MCF-7adr cells. CARESENG™ gave rise to similar results in all the above experiments. Conclusions: These results suggest that aPPD is an effective P-gp blocker with a mechanism different from that of verapamil. Given extremely low toxicity of the compound, aPPD is a potential candidate of chemosensitizer for treatment of multidrug resistant tumors. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration PanaGin Pharmaceuticals PanaGin Pharmaceuticals PanaGin Pharmaceuticals

Aglycone Protopanaxadiol, a ginseng saponin inhibits P-glycoprotein and sensitizes chemotherapy drugs on multidrug resistant cancer cells

9663 Background:Aglycone Protopanaxadiol (aPPD) is an aglycone derivative of ginseng saponins. Our previous work showed that a natural ginseng product CARESENG™ containing mainly aPPD induced cell apoptosis through various signal pathways including caspases. CARESENG™ also enhances the sensitivity of multidrug resistant cancer cells to various chemotherapy drugs. P-glycoprotein (P-gp, MDR1) is one of the major causes of multidrug resistance of many tumor cells. Blocking the function of P-gp may enhance efficacy of chemotherapy. In the present study, we investigated the possible mechanism of chemosensitizing effect of purified aPPD compound as well as CARESENG™. Methods:Breast cancer cell MCF-7adr and leukemia cell line P388adr, both overexpressing P-gp, were used to test the interaction between the compound and P-gp. Calcein-AM, a P-gp substrate, efflux assay was used to measure function of P-gp. Membrane preparation was also used to measure the ATPase activity of P-gp in the presence of aPPD or verapamil. Results:Our results demonstrated that 70uM aPPD could significantly block P-gp function on both MCF-7adr and P388adr cells showing increased intracellular concentrations of calcein-AM. Furthermore, the maximum effects of aPPD and verapamil on P-gp inhibition was additive when treated together on P388adr cells. On the other hand, aPPD had no effect on ATPase activity of P-gp while verapamil increased it by more than 2-fold. 20uM of aPPD completely reversed P-gp induced drug resistant to Taxol or Doxorubicin on MCF-7adr cells. CARESENG™ gave rise to similar results in all the above experiments. Conclusions: These results suggest that aPPD is an effective P-gp blocker with a mechanism different from that of verapamil. Given extremely low toxicity of the compound, aPPD is a potential candidate of chemosensitizer for treatment of multidrug resistant tumors. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration PanaGin Pharmaceuticals PanaGin Pharmaceuticals PanaGin Pharmaceuticals