Discovery of aromatic amides with triazole-core as potent reversal agents against P-glycoprotein-mediated multidrug resistance

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is a major impediment for clinical cancer therapy. 19 novel aromatic amides with triazole-core as MDR reversal agents were designed and synthesized via click chemistry to reverse MDR. Among them, compound 42 was identified as the most promising candidate with high potency (EC₅₀ = 78.1 ± 5.4 nM), low cytotoxity (SI > 1282) and persistent duration in reversing doxorubicin (DOX) resistance in K562/A02 cells. 42 also enhanced the potency of other P-gp associated cytotoxic agents with different structures. In further study, remarkably increased intracellular accumulation of Rh123 and DOX in K562/A02 cells was achieved by compound 42, while CYP3A4 activity had no change by compound 42. These results indicate that compound 42 as a relatively safe modulator of P-gp-mediated MDR has good potential for further development.     

Design,synthesis and evaluation of novel triazole core based P-glycoprotein-mediated multidrug resistance reversal agents

A novel series of triazol-N-ethyl-tetrahydroisoquinoline based compounds were designed and synthesized via click chemistry. Most of the synthesized compounds showed P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) reversal activities. Among them, compound 7 with little cytotoxicity towards GES-1 cells (IC₅₀ >80 μM) and K562/A02 cells (IC₅₀ >80 μM) exhibited more potency than verapamil (VRP) on increasing anticancer drug accumulation in K562/A02 cells. Moreover, compound 7 could significantly reverse MDR in a dose-dependent manner and also persist longer chemo-sensitizing effect than VRP with reversibility. Further mechanism studies revealed that compound 7 in reversing MDR revealed that it could remarkably increase the intracellular accumulation of both rhodamine-123 (Rh123) and adriamycin (ADM) in K562/A02 cells as well as inhibit their efflux from the cells. These results suggested that compound 7 showed more potency than the classical P-gp inhibitor VRP under the same conditions, which may be a promising P-gp-mediated MDR modulator for further development.     

Design and synthesis of tetrahydroisoquinoline derivatives as potential multidrug resistance reversal agents in cancer

Exploration for new MDR-modulator utilizing tetrahydroisoquinoline as scaffold disclosed 6,7-dimethoxy-1-(3,4-dimethoxy)benzyl-2-(N-n-octyl-N'-cyano)guanyl-1,2,3,4-tetrahydroisoquinoline (7) as a readily accessible medicinal lead. Compound 7 possessed potent MDR reversal activity in the range of the reference compound verapamil, and had not cardiovascular activity compared to verapamil.     

Synthesis and evaluation of substituted dibenzo[c,e]azepine-5-ones as P-glycoprotein-mediated multidrug resistance reversal agents

A series of substituted dibenzo[c,e]azepine-5-ones (7a-h) were synthesized and evaluated as P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) reversal agents. The most potent compound 7h could significantly and selectively enhance the chemo-sensitivity of drug-resistant K562/A02 cells to the cytotoxic effect of adriamycin (ADR) in a dose-dependent manner. Further studies indicated that 7h could markedly increase intracellular accumulation of both rhodamine 123 and ADR in K562/A02 cells and inhibit their efflux from the cells. And 7h had little effect on the levels of P-gp mRNA and protein in K562/A02 cells. These results suggest that the anti-MDR effect of 7h might be attributed to the inhibition of drug efflux function of P-gp, leading to the increased drug accumulation in K562/A02 cells, and thus the compound could be served as a lead for developing P-gp-mediated MDR reversal agents.     

Synthesis and biological activity of 4-alkoxy chalcones: potential hydrophobic modulators of P-glycoprotein-mediated multidrug resistance

A series of 4-alkoxy-2′,4′,6′-trihydroxychalcones have been synthesized and evaluated for their ability to inhibit P-glycoprotein-mediated multidrug resistance (MDR) by direct binding to a purified protein domain containing an ATP-binding site and a modulator-interacting region. The introduction of hydrophobic alkoxy goups at position 4 led to much more active compounds as compared to the parent chalcone. The binding affinity increased as a function of the chain length, up to the octyloxy derivative for which a K_D of 20 nM was obtained.     

Cytokine-mediated reversal of multidrug resistance

The occurrence of the multidrug resistance phenotype still represents a limiting factor for successful cancer chemotherapy. Numerous efforts have been made to develop strategies for reversal and/or modulation of this major therapy obstacle through targeting at different levels of intervention. The phenomenon of MDR is often associated with overexpression of resistance-associated genes. Since the classical type of MDR in human cancers is mainly mediated by the P-glycoprotein encoded by the multidrug resistance gene 1, mdr1, the majority of reversal approaches target the expression and/or function of the mdr1 gene/P-glycoprotein. Due to the fact that the multidrug phenotype always represents the net effect of a panel of resistance-associated genes/gene products, other resistance genes, e.g. those encoding the multidrug resistance-associated protein MRP or the lung resistance protein LRP, were included in the studies. Cytokines such as tumor necrosis factor α and interleukin-2 have been shown to modulate the MDR phenotype in different experimental settings in vitro and in vivo. Several studies have been performed to evaluate their potential as chemosensitizers of tumor cells in the context of a combined application of MDR-associated anticancer drugs like doxorubicin and vincristine with cytokines. Moreover, the capability of cytokines to modulate the expression of MDR-associated genes was demonstrated, either by external addition or by transduction of the respective cytokine gene. Knowledge of the combination effects of cytokines and cytostatics and its link to their MDR-modulating capacity may contribute to a more efficient and to a more individualized immuno-chemotherapy of human malignancies. This revised version was published online in August 2006 with corrections to the Cover Date.     

New artesunic acid homodimers: Potent reversal agents of multidrug resistance in leukemia cells

To evade the problem of multidrug resistance, hybridization of natural products in dimers is considered as an effective method. After the successful synthesis of three artesunic acid homodimers connected by different types of chemical linkers, we analyzed their activity against human CCRF-CEM and multidrug-resistant p-glycoprotein-overexpressing CEM/ADR 5000 leukemia cells and observed, that multidrug resistant cells were not cross-resistant to the new compounds. Collateral sensitivity was observed for artesunic acid homodimer 2. The obtained results deliver valuable information about the linker's structure which is required for homodimers to be highly cytotoxic.     

A novel class of highly potent multidrug resistance reversal agents: Disubstituted adamantyl derivatives

Novel disubstituted adamantyl derivatives were synthesized and evaluated in a P-glycoprotein dependent multidrug resistance cancer cell line. The hit to lead optimization provided potent MDR reversal agents. Some potent adamantyl derivatives were more than 10-fold more potent than verapamil without considerable intrinsic cytotoxicity. The 3-trifluorophenyl derivative 14f did not affect the metabolism of CYP450 3A4, whereas most of MDR revertants had a weak inhibitory effect.     

Papyriferic acid derivatives as reversal agents of multidrug resistance in cancer cells

Forty-one derivatives of papyriferic acid were prepared based on our previous finding that methyl papyriferate (3) showed potent reversing effect on cytotoxicity of colchicine against multidrug resistance (MDR) human cancer cells (KB-C2), and evaluated for their cytotoxicity and effect on reversing P-gp-mediated MDR against KB-C2 cells. 3-O-(Morpholino-β-oxopropanoyl)-12β-acetoxy-3α,25-dihydroxy-(20S,24R)-epoxydammarane (37) significantly increased the sensitivity of colchicine against KB-C2 cells by 185-fold at 5 μg/mL (7.4 μM), and the cytotoxicity of colchicine was recovered to nearly that of sensitive (KB) cells. The other several new amide derivatives also exhibited potent reversal activity comparable to or more potent than methyl papyriferate and verapamil.     

Radiopharmaceuticals for assessment of multidrug resistance P-glycoprotein-mediated drug transport activity

Multidrug resistance (MDR) mediated by overexpression of MDR1 P-glycoprotein (Pgp) is one of the best characterized transporter-mediated barriers to successful chemotherapy in cancer patients. Thus, noninvasive interrogation of Pgp-mediated transport activity in vivo would be beneficial in guiding therapeutic choices. Both small organic medicinals as well as metal complexes characterized as transport substrates for Pgp are amenable to incorporation of PET or SPECT radionuclides and may enable noninvasive imaging of Pgp in cancer patients. Toward this objective, clinically approved agents, exemplified by (99m)Tc-Sestamibi and (99m)Tetrofosmin, have already shown promise for the functional evaluation of Pgp-mediated transport activity in human tumors in vivo. In addition, selected agents from an upcoming class of substituted Schiff-base gallium(III) complexes containing an N(4)O(2) donor core in their organic scaffold and capable of generating both SPECT and PET radiopharmaceuticals have also been shown to be promising for noninvasive assessment of Pgp activity in vitro and in vivo.     

Prolongation of pentoxifylline aliphatic side chain positively affects the reversal of P-glycoprotein-mediated multidrug resistance in L1210/VCR line cells

We reported previously that derivatives of pentoxifylline (PTX) reverse multidrug resistance (MDR) in P-glycoprotein (P-gp) positive L1210/VCR cells. Based on the results of a recent study using 25 N-alkylated methylxanthines with carbohydrate side-chains of various lengths, we formulated the following design criteria for a methylxanthine molecule to effectively reverse P-gp mediated MDR: i) a massive substituent at the N1 position is crucial for MDR reversal potency; ii) elongation of the substituents at the N3 and N7 positions (from methyl to propyl) increases the efficacy of a xanthine to reverse MDR; iii) elongation of the substituent at the C8 position (from H to propyl) decreases the efficacy of a xanthine to reverse MDR. Based on these criteria, we synthesized and tested for potency to reverse MDR a new PTX derivative, 1-(10-undecylenyl)-3-heptyl-7-methyl xanthine (PTX-UHM), with prolonged substituents at the N1 and N3 positions. The derivative was obtained by alkylation of 3-heptyl-7-methyl xanthine with 1-methylsulfonyloxy-10-undecylenyl. NMR and IR structural analyses proved the identity of the product. Cytotoxicity study showed that PTX-UHM is only slightly more toxic to L1210/VCR cells than PTX. We found that both PTX-UHM and PTX were able to reverse vincristine resistance of L1210/VCR cells, yet PTX-UHM was significantly more efficient in the reversal than PTX.     

Synthesis and biological evaluation of taxinine analogues as orally active multidrug resistance reversal agents in cancer

Three novel taxinine analogues were prepared and tested for their activity as multidrug resistance (MDR) reversal agents in comparison with verapamil. In vitro testing demonstrated that compounds 8-10 possess MDR-reversal activity in the KB/V cell line. Half-hour after treatment with 5, 10, and 20 micromol/L compound 9, the intracellular rhodamine123 concentration increased 2.3, 2.9, and 3.2-fold, respectively, higher than 1.88-fold of 10 micromol/L verapamil in KB/V cell line. In vivo studies with VCR-resistant KB/V tumor xenografts showed that compound 9 in combination with VCR significantly inhibited tumor growth. Treatment with VCR or 9 alone did not result in growth inhibition. These results reveal that three taxinine analogues are good modifiers of MDR in tumor cells.     

Analogues of tetramethylrosamine as transport molecules for and inhibitors of P-glycoprotein-mediated multidrug resistance

Tetramethylrosamine and its thio- and seleno- analogues (TMR-O, TMR-S, and TMR-Se, respectively) were examined for their ability to be transported by Pgp into chemo-resistant CR1R12 cells. Verapamil (7 x 10(-6)M) enhanced the uptake of TMR-O and TMR-S into CR1R12 cells compared to those cultures not previously exposed to verapamil. The uptake of TMR-O and TMR-S in CR1R12 cells in the presence of 7 x 10(-6)M verapamil was equivalent to its uptake in the chemo-sensitive parent cell line AUXB1 in the absence or presence of verapamil. None of the TMR analogues were effective alone as photosensitizers of CR1R12 cells. However, when either TMR-S or TMR-Se was added to CR1R12 cells after 7 x 10(-6)M verapamil exposure for 2h, irradiation of cultures with 5.0J cm(-2) of 350-750 nm light caused significant phototoxicity. TMR-O showed no significant phototoxicity in the presence of verapamil. Chemo-sensitive AUXB1 cells are equally susceptible to phototoxicity using TMR-Se with or without previous exposure to verapamil. The Pgp modulators verapamil and CsA increased the uptake of CAM into CR1R12. Exposure of CR1R12 cells to TMR-S or TMR-Se for 2h in the dark resulted in no significant change in the intracellular accumulation of CAM. However, 1h of light exposure after incubation of cells with TMR-S or TMR-Se resulted in an up to 2-fold increase in CAM uptake.     

Design and synthesis of an optimized positional scanning library of peptoids: identification of novel multidrug resistance reversal agents

Herein is reported the optimized solid-phase synthesis of a library of 5,120 trimeric N-alkylglycines (peptoids) using the positional scanning format and the submonomer strategy. Diversity at the N-terminal position was generated from 20 commercially available primary amines, whereas 16 primary amines were employed for the middle and C-terminal positions of the trimers. Formation of undesirable side-products observed in a previous library synthesis (Humet, M. et al. J. Comb. Chem. 2003, 5, 597-605) was averted by restricting the use of primary amines functionalized with tertiary amino groups to the third amination step. Screening of the new library for the identification of chemosensitizers yielded two peptoids, compounds 1 and 2, with potent in vitro activity as multidrug resistance (MDR) reversal agents. The structures of the lead peptoids are consistent with a pharmacophore model generated from the interaction of various known inhibitors with the MDR-implicated transmembrane glycoprotein P-gp.     

Synthesis of curcumin mimics with multidrug resistance reversal activities

In order to discover novel multidrug resistance (MDR) reversal agents for efficient cancer chemotherapy, the unsymmetrical curcumin mimics with various amide moieties (6-19) were synthesized and evaluated their MDR reversal activities in MDR cell line KBV20C. Among the tested compounds, 13, 16, and 17 showed potent MDR reversal activities by inhibiting drug efflux function of P-glycoprotein in KB20C cells, and almost recovered the cytotoxicity of vincristine and paclitaxel against KBV20C cell to the degree of potency against drug sensitive KB cells.     

Synthesis and evaluation of furoxan-based nitric oxide-releasing derivatives of tetrahydroisoquinoline as anticancer and multidrug resistance reversal agents

Multidrug resistance in tumor cells poses a major obstacle to efficient chemotherapy. Several types of agents have been recognized as multidrug resistance inhibitors, among which the tetrahydroisoquinolines is the most studied. In current study 16 furoxan-based nitric oxide-releasing derivatives of tetrahydroisoquinoline were synthesized. Their cytotoxic activities and effects in reversing multidrug resistance have been evaluated. The results revealed that these compounds had moderate cytotoxic effects. Compounds 7a-f, 7h, and 7l showed higher cytotoxicities than the rest, but lower than adriamycin on K562 cell line. Compounds 7d, 7f, and 7l exhibited potent MDR reversal activities on K562/A02 cell line. The accumulation assay indicated that compounds 7d, 7f, and 7l significantly increased the intracellular accumulation of rhodamine123 in K562/A02 cells. Furthermore, these three compounds produced high concentrations of NO in K562/A02 cells. Potentially, the high concentrations of NO produced by NO donor moieties will lead to an increased cytotoxicity to K562/A02 cells. Our results suggested that compounds 7d, 7f, and 7l had anticancer effects, as well as multidrug resistance reversal effects.     

Euphorbia and Momordica metabolites for overcoming multidrug resistance

Multidrug resistance (MDR) is the major obstacle for cancer chemotherapy. MDR is a multifactorial phenomenon that can result from several mechanisms, including an increased drug efflux, due to overexpression of P-glycoprotein (P-gp) that transports anticancer drugs out of the cells. Thus, the role of this transporter has made it a therapeutic target and the development of P-gp modulators considered among the most realistic approaches for overcoming P-gp-mediated MDR. Many other strategies have been proposed. One of them is the identification of compounds that selectively kill multidrug resistant cells. In our search for MDR modulators from plants, the P-gp inhibition ability of a large number of compounds on resistant cancer cells was evaluated. These compounds, presented in this review, comprise mainly diterpenes, triterpenes and phenolic derivatives. The most relevant results were obtained from two sets of compounds: macrocyclic diterpenes with the jatrophane and lathyrane scaffold, and triterpenes of the cucurbitane-type isolated from Euphorbia species and Momordica balsamina L., respectively. Additionally, some of those macrocyclic diterpenes, and ent-abietane diterpenic lactones, also isolated from Euphorbia species, were found to be selectively toxic to drug-resistant phenotypes.     

一株猪源鼠伤寒沙门氏菌的耐药性鉴定及其消除

猪源鼠伤寒沙门氏菌临床分离株17Y,检测其对19种抗生素的耐药性,结果耐14种抗生素。用高温及高浓度SDS处理后,获得对11种抗生素的敏感性,该菌株命名为17S1。PCR检测证明,大部分耐药基因存在于质粒上,包括I型整合子携带耐药基因,且随着质粒的消除而被消除。所鉴定的耐药基因有blaTEM、blaOXA-1、cat1、tet(B)、aacC2、aadA8b、dhfrXⅡ和sul1等。喹诺酮类药物的靶基因gyrA与parC位于染色体上。GyrA在耐药决定区第87位氨基酸突变(N78D),导致了喹诺酮类药物的耐药性逆转。敏感菌中扩增不到质粒毒力基因spv与rck。耐药性消除后的菌株17S1对小鼠的毒力降低(LD50增加10倍),在小鼠体内的增长与散速度也显著降低(P<0.05)。以上证据表明,鼠伤寒沙门氏菌的多重耐药性主要由质粒决定,研究开发新型质粒消除剂将对克服鼠伤寒沙门氏菌多重耐药性具有重要意义。     

Reversal of P-glycoprotein-mediated multidrug resistance by doxorubicin and quinine co-loaded liposomes in tumor cells

Multidrug resistance (MDR) is a major obstacle to successful clinical cancer chemotherapy. Currently, there is still unsatisfactory demand for innovative strategies as well as effective and safe reversing agent to overcome MDR. In this study, we developed a novel nanoformulation, in which doxorubicin hydrochloride (DOX) and quinine hydrochloride (QN) were simultaneously loaded into liposomes by a pH-gradient method for overcoming MDR and enhancing cytotoxicity in a doxorubicin-resistant human breast cancer cell line (MCF-7/ADR). The various factors were investigated to optimize the formulation and manufacturing conditions of DOX and QN co-loaded liposomes (DQLs). The DQL showed uniform size distribution and high encapsulation efficiency (over 90%) for both the drugs. Furthermore, DQLs significantly displayed high intracellular accumulation and potential of MDR reversal capability in MCF-7/ADR cells through the cooperation of DOX with QN, in which QN played the role as a MDR reversing agent. The IC₅₀ of DQL0.5:1 with the DOX/QN/SPC weight ratio of 0.5:1:50 was 1.80?±?0.03?μg/mL, which was 14.23 times lower than that of free DOX in MCF-7/ADR cells. And the apoptotic percentage induced by DQL0.5:1 was also increased to 62.2%. These findings suggest that DQLs have great potential for effective treatment of MDR cancer.