KB-V1 Cells Research Articles

A facile synthesis and biological activity of novel tetrahydrobenzo[4′,5′]thieno[3′,2′:5,6]pyrido[4,3- d]pyrimidin-4(3 H)-ones

The synthesis and biological activity of 2-substituted-8,9,10,11-tetrahydrobenzo[4′,5′]thieno[3′,2′:5,6] pyrido[4,3- d]pyrimidin-4(3 H)-ones are described. Bioassay results indicated that these compounds have antifungal activity against Botrytis cinerea at a concentration of 50 mg/L. In addition, compounds 5m and 5n were effective to both KB cells and their parent multidrug resistant KBv200 cells with the overexpression of ABCB1. For example, compound 5m showed the best inhibition against KB and KBv200 cells with IC 50 values of 17.4 and 25.4 μM, respectively.

Reversal effect of Raf-1/Mdr-1 siRNAs co-transfection on multidrug resistance in KBv200 cell line

Multidrug resistance (MDR) is a major barrier for chemotherapy of many cancers. Mdr-1 plays a key role in the development of MDR as extensively verified. However, the role of Raf-1 overexpression in the development of multidrug resistance in human squamous carcinoma (KBv200) cells remains largely unknown. The aim of this study was to investigate the correlation of Raf-1 overexpression with the development of multidrug resistance in KBv200 cells. Furthermore, we explored the reversal effect of Raf-1 siRNA transfection and Raf-1/Mdr-1 siRNAs co-transfection on the multidrug resistance of KBv200 cells and potential mechanism of reversing the multidrug resistance. MTT and flow cytometry assay were used to investigate the reversal effect of single transfection with either Raf-1 or Mdr-1 siRNA and double transfection with Raf-1/Mdr-1 siRNAs to vincristine of KBv200 cells. RT-PCR, immunofluorescence and Western Blot were used to detect mRNA and protein expression of Raf-1 and multidrug-resistant gene Mdr-1. The results of gene detection showed that the expression levels of both Raf-1 and Mdr-1 were greatly decreased upon Raf-1 silencing alone or in combination with Mdr-1 silencing. Raf-1 or Mdr-1 siRNA single transfection could reverse the multidrug resistance of KBv200 cells effectively. Compared with single transfection, Raf-1/Mdr-1 siRNAs co-transfection can significantly reduce IC(50) values and increase the apoptotic rates of KBv200 cells. The above results suggested that Raf-1 gene may be a novel target for reversing the multidrug resistance of human squamous carcinoma cells. Raf-1/Mdr-1 siRNAs co-transfection might be a promising approach to abrogate the multidrug resistance of cancer cells. The potential mechanism may be via inhibiting the multidrug-resistant gene Mdr-1 expression efficiently.

Sensitization of ABCB1 overexpressing cells to chemotherapeutic agents by FG020326 via binding to ABCB1 and inhibiting its function

The effectiveness of chemotherapeutic treatment is usually limited by the overexpression of adenosine triphosphate binding cassette (ABC) transporters, which mediate multidrug resistance (MDR) by acting as efflux pumps to remove chemotherapeutic agents from MDR cancer cells. Thus, the inhibition of ABC transporters may represent a promising strategy to reverse MDR. This study was to characterize the actions of FG020326, a newly synthesized triaryl-substituted imidazole derivative, to reverse MDR in vitro and in vivo. FG020326 significantly potentiated the cytotoxicity of paclitaxel, doxorubicin, and vincristine in the ABCB1 (P-glycoprotein, P-gp) overexpressing cells KBv200 and MCF-7/adr, but not in the ABCB1 negative parental cell lines KB and MCF-7. However, FG020326 did not alter the cytotoxicity of the aforementioned drugs in ABCC1 (MRP1), ABCC4 (MRP4), ABCG2 (BCRP) and LRP overexpressing cell lines, KB-CV60, NIH3T3/MRP4-2, S1-M1-80 and SW1573/2R120, respectively. FG020326, following p.o. administration, was present in concentrations sufficient for reversal of MDR in mice. The co-administration of FG020326 with paclitaxel or vincristine significantly enhanced the antitumor activity of these drugs without significantly increasing toxicity in the mice bearing the KBv200 cell xenografts. In addition, FG020326, at concentrations that reversed MDR, did not significantly affect the activity of CYP3A4 or alter the pharmacokinetic profile of paclitaxel after co-administration with paclitaxel. FG020326 produced a significant concentration-dependent displacement of [ 3H]azidopine and inhibition of efflux of drug from cells. Furthermore, FG020326 was co-localized with ABCB1 in cell membranes. Hence, FG020326 is characterized as a third generation MDR modulator that holds great promise for the treatment of cancer patients with ABCB1-mediated MDR.

Structure elucidation and NMR assignments for three anthraquinone derivatives from the marine fungus Fusarium sp. (No. ZH‐210)

The structure elucidations and complete (1)H and (13)C NMR assignments are reported for three new anthraquinone derivatives: Fusaquinon A (1), B (2), and C (3) isolated from the fermentation medium of the marine fungus Fusarium sp. (No. ZH-210). HREIMS, Fourier transform infrared absorption spectrometry (FT-IR), NMR experiments including gCOSY, gHMQC, gHMBC, and NOESY were used for the determination of the structures and NMR spectral assignments. Preliminary pharmacological test showed that they exhibited low cytotoxic activity towards KB, KBv200, and MCF-7 cell lines.

Reversal effect of resveratrol on chemotherapy resistance in KBv200 cell line and underlying mechanisms

To explore the reversal effect and potential mechanism of resveratrol on multidrug resistance of human oral epidermoid carcinoma KBv200 cells. MTT assay was used to investigate reversal index of resveratrol to vincristine, adriamycin and paclitaxel. Cell apoptosis were measured by flow cytometry. RT-PCR and Western blot were used to detect mRNA and protein expression of multidrug resistant 1 (MDR1) and B cell lymphoma leukemia-2 (Bcl-2). Resveratrol produced a synergistic effect with chemotherapeutics and obviously reversed the multidrug resistant phenotype of KBv200 cells. The reversal fold (RF) of 200 micromol/L resveratrol to vincristine, paclitaxel and adriamycin were 77.1, 61.3 and 5.9, respectively. The gene array results showed that resveratrol greatly downregulated expression levels of Bcl-2 and MDR1. After treated with 100 micromol/L, 200 micromol/L resveratrol, the expression level of Bcl-2 and MDR1 in KBv200 cells were markedly decreased in comparison with those untreated (t were 2.98, 3.51 and 3.12, 4.56, P < 0.05). Resveratrol can efficiently reverse multidrug resistance in KBv200 cells. The potential mechanism may be via inhibiting the multidrug resistant gene expressions and/or promoting cell apoptosis.

Bullatacin Triggered ABCB1‐Overexpressing Cell Apoptosis via the Mitochondrial‐Dependent Pathway

This paper was to explore bullatacin-mediated multidrug-resistant cell apoptosis at extremely low concentration. To investigate its precise mechanisms, the pathway of cell apoptosis induced by bullatacin was examined. Bullatacin causes an upregulation of ROS and a downregulation of ΔΨm in a concentration-dependent manner in ABCB1-overexpressing KBv200 cells. In addition, cleavers of caspase-9, caspase-3, and PARP were observed following the release of cytochrome c from mitochondria after bullatacin treatment. However, neither cleavage of caspase-8 nor change of expression level of bcl-2, bax and Fas was observed by the same treatment. Pretreating KBv200 cells with N-acetylcysteine, an antioxidant modulator, resulted in a significant reduction of ROS generation and cell apoptosis induced by bullatacin. Bullatacin-induced apoptosis was antagonized by z-LEHD-fmk, a caspase-9 inhibitor, but not by z-IETD-fmk, a caspase-8 inhibitor. These implied that apoptosis of KBv200 cells induced by bullatacin was associated with the mitochondria-dependent pathway that was limited to activation of apical caspase-9.

L1EPO, a Novel Podophyllotoxin Derivative Overcomes P-Glycoprotein-Mediated Multidrug Resistance in K562/A02 Cell Line

The ineffectiveness of anticancer drugs is frequently observed in cancer chemotherapy. The resistance of tumor cells to various cytotoxic drugs is defined as multidrug resistance (MDR). The purpose of our present study was to investigate the inhibitory effects of L1EPO synthesized by our group on P-glycoprotein (P-gp)-mediated MDR in K562/A02 and KBv200 cell lines, which expressed high levels of P-gp. Both the cytotoxicity of the compound and its ability to inhibit K562/A02 and KBv200 cells were determined by sulforhodamine B sodium salt (SRB) assay. Morphologic apoptosis was detected by Hoechst33342 staining assay. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect mdr-1 gene transcription, and Western blot assay was used to assess P-gp expression. Interestingly, we found that the K562/A02 cell line was rendered resistant toward Adriamycin but not towards L1EPO when compared with the parental cells. Furthermore, L1EPO could down-regulate the mdr-1 gene, and it reduced the expression of P-gp and displayed a perfect dose dependence. Moreover, it had less cytotoxicity in normal human cell lines (fibroblast, VEC), GI(50)>10 micromol/l. Consequently, L1EPO has the potential to overcome P-glycoprotein-mediated MDR in the K562/A02 cell line.

Lapatinib (Tykerb, GW572016) Reverses Multidrug Resistance in Cancer Cells by Inhibiting the Activity of ATP-Binding Cassette Subfamily B Member 1 and G Member 2

Lapatinib is active at the ATP-binding site of tyrosine kinases that are associated with the human epidermal growth factor receptor (Her-1 or ErbB1) and Her-2. It is conceivable that lapatinib may inhibit the function of ATP-binding cassette (ABC) transporters by binding to their ATP-binding sites. The aim of this study was to investigate the ability of lapatinib to reverse tumor multidrug resistance (MDR) due to overexpression of ABC subfamily B member 1 (ABCB1) and ABC subfamily G member 2 (ABCG2) transporters. Our results showed that lapatinib significantly enhanced the sensitivity to ABCB1 or ABCG2 substrates in cells expressing these transporters, although a small synergetic effect was observed in combining lapatinib and conventional chemotherapeutic agents in parental sensitive MCF-7 or S1 cells. Lapatinib alone, however, did not significantly alter the sensitivity of non-ABCB1 or non-ABCG2 substrates in sensitive and resistant cells. Additionally, lapatinib significantly increased the accumulation of doxorubicin or mitoxantrone in ABCB1- or ABCG2-overexpressing cells and inhibited the transport of methotrexate and E(2)17betaG by ABCG2. Furthermore, lapatinib stimulated the ATPase activity of both ABCB1 and ABCG2 and inhibited the photolabeling of ABCB1 or ABCG2 with [(125)I]iodoarylazidoprazosin in a concentration-dependent manner. However, lapatinib did not affect the expression of these transporters at mRNA or protein levels. Importantly, lapatinib also strongly enhanced the effect of paclitaxel on the inhibition of growth of the ABCB1-overexpressing KBv200 cell xenografts in nude mice. Overall, we conclude that lapatinib reverses ABCB1- and ABCG2-mediated MDR by directly inhibiting their transport function. These findings may be useful for cancer combinational therapy with lapatinib in the clinic.

Structure elucidation of two new xanthone derivatives from the marine fungus Penicillium sp. (ZZF 32#) from the South China Sea

Two new xanthones, 8-(methoxycarbonyl)-1-hydroxy-9-oxo-9H-xanthene-3-carboxylic acid (1) and dimethyl 8-methoxy-9-oxo-9H-xanthene-1,6-dicarboxylate (2) and one known xanthone methyl 8-hydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate (3) were isolated from the culture broth of the mangrove fungus Penicillium sp. (ZZF 32#) collected from the South China Sea. Their structures were established by comprehensive analysis of one-dimensional (1D) and two-dimensional (2D) NMR data. The structure of compound 3 was confirmed by X-ray crystallography, which led to the suggestion that janthinone (4) might have the same structure as 3. Compounds 1-3 were inactive against KB or KBv200 cells during cytotoxicity evaluations.

Reversal effect of resveratrol on multidrug resistance in KBv200 cell line

A multidrug-resistant clone of human oral epidermoid carcinoma KB cells was isolated by stepwise selection on exposure to increasing doses of vincristine. The final clone, KBv200, obtained after ethylmethane sulfonate mutagenesis showed 156-fold higher resistance to vincristine than KB cells. The cells were also cross-resistant to paclitaxel and adriamycin. The aim of this study was to explore the reversal effect and potential mechanism of resveratrol on KBv200 cells. MTT assay was used to investigate the reversal index of resveratrol to vincristine, adriamycin and paclitaxel. Cell apoptosis was measured by flow cytometry. RT-PCR and western blot were used to detect mRNA and protein expression of multidrug-resistant gene MDR1 and apoptosis-suppressing gene Bcl-2. Resveratrol produced a synergistic effect combined with the chemotherapeutic agents and reversed the multidrug-resistant phenotype of KBv200 cells. Flow cytometry confirmed that the percentage of apoptotic cell increased when KBv200 cells were exposed to resveratrol. The results of gene detection showed that the expression levels of MDR1 and Bcl-2 were decreased upon resveratrol treatment. Resveratrol can efficiently reverse multidrug resistance in KBv200 cells. The potential mechanism may be via inhibiting the multidrug-resistant gene expressions and/or promoting cell apoptosis.

1p31, 7q21 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine resistance of human cervical carcinoma KB cells

Vinblastine (VBL) is used to treat certain kinds of cancer including Hodgkin's lymphoma, lung cancer, breast cancer, testicular cancer and cervical carcinoma. However, the rapid development of resistance during therapy remains a major clinical challenge. In order to reverse cancer cell resistance, the goal of this study was to find differentially expressed genes and chromosomal alterations in multidrug resistant (MDR) KB-v1 cells, further to probe the relationship between drug resistance and differential genes, and chromosomal changes in MDR cancer cells. Comparative genomic hybridization (CGH) analysis of MDR KB-v1 and their parental KB-3-1 cells revealed chromosomal changes; microarray-based expression profiling was carried out by comparing the gene expressions of MDR KB-v1 cells and KB-3-1 cells. We have identified 3 chromosomal gains in regions of 1p31, 7q21 and 18q21 in MDR cells and 10 genes (CYR61, UGTREL7, MBD1, NARS, ATP5A1, ABCB1, ABCB4, PEG10, MCM7, SERPINE1) contained in these regions were also up-regulated in MDR KB-v1 cells. Forty-nine genes were down-regulated when KB-v1 cells were subjected to lower dose or depletion of the drug. We have confirmed some gene expression changes by reverse transcription-polymerase chain reaction and Northern blots. These are the first data describing the relationship of 1p31 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine-resistance. This study also demonstrates that the combination of CGH and cDNA microarray is a very useful tool to detect drug resistant targets in cancer treatment.

Isolation, structure elucidation, and mutagenicity of four alternariol derivatives produced by the mangrove endophytic fungus No. 2240

A new alternariol derivative, 2240B (1), together with alternariol (2), alternariol 4,10-dimethyl ether (3), and alternariol 4-methyl ether (4), was isolated from the ethyl acetate extract of the liquid medium GYT of No. 2240, the mangrove endophytic fungus from the South China Sea Coast. The structure of compound 1 was unambiguously elucidated as alternariol 4-methyl-10-acethyl ester by spectra including one/two-dimensional NMR, HREIMS, IR, and UV. The structures of compounds 2–4 were also established by spectroscopic analyses and comparison with related literature data. The anticancer tests showed that compounds 2 and 4 had strong activities against KB and KBv200 cells with IC50 values of 3.17, 3.12, and 4.82, 4.94 µg/mL, while compounds 1 and 3 exhibited weak activities against the two kinds of tumor lines with IC50 values of more than 50 µg/mL.

1H and 13C NMR assignments of three nitrogen containing compounds from the mangrove endophytic fungus (ZZF08)

A new natural product, named phomopsin A, 1-(meta-hydroxyphenyl)-4-hydroxy-3-isoquinolone (1), together with two known compounds cytochalasin H (2) and glucosylceramide (3), was isolated from the mangrove endophytic fungus Phomopsis sp. (ZZF08) obtained from the South China Sea coast. The structures were elucidated by 1D and 2D NMR experiments including COSY, HMQC, and HMBC. According to NMR and single-crystal X-ray diffraction, it was found that some assignments about (1)H and (13)C NMR data for cytochalasin H (2) were probably uncorrected in the previous reports. In our cytotoxicity assays, compound 1 showed moderate cytotoxicity toward KB cells with IC(50) at 28.0 microg ml(-1) and KBv200 cells with IC(50) at 16.8 microg ml(-1), and compound 2 exhibited strong cytotoxicity toward KB cells and KBv200 cells with IC(50) less than 1.25 microg ml(-1).

Reversal of P-glycoprotein-mediated multidrug resistance of cancer cells by five schizandrins isolated from the Chinese herb Fructus Schizandrae

Fructus Schizandrae (FS) is commonly used as a tonic in traditional Chinese medicine. Recently, FS was found to significantly improve liver dysfunction in chronic hepatitis patients. The present study was to assess the reversal effect of five schizandrins and crude extract from FS (named LCC) on multidrug resistance (MDR) of cancer cells, both in vitro and in vivo. Chemically, the five schizandins are derivatives of dibenzo-(a, c)-cyclooctene lignan with distinct structures differing from any known MDR reversal agents. A panel of sensitive and resistant cancer cell lines were treated with various concentrations of LCC and schizandrins. Drug sensitivity, accumulation of Doxorubicin (Dox), expression of P-glycoprotein and protein kinase C (PKC), and apoptosis were determined in vitro. The in vivo effect was tested in nude mice grafted with sensitive and resistant human epidermal cancer cell line to vincristine (VCR) (KB, KBv200). The tested five compounds at 25 muM showed various levels of MDR reversal activity, of which, schizandrin A (Sin A) was the most potent one. Sin A reversed VCR resistance in KBv200 cells, MCF-7/Dox cells and Bel7402 cells by 309-, 38-, and 84-folds, respectively. Also, Sin A reversed the resistance of Dox in the above cancer cell lines. LCC at 25 mug/ml reversed VCR resistance by 619-folds in KBv200, 181-folds in MCF-7/Dox cell line, and 1,563-folds in innate resistance of human hepatic cellular carcinoma Bel7402 cells to VCR. Furthermore, LCC and its active component Sin A potently reversed the cross-resistance to paclitaxel in those cell lines. Both Sin A and LCC markedly increased intracellular Dox accumulation and enhanced apoptosis, down-regulated Pgp protein and mRNA and total PKC expression in MDR cells. Coadministration of LCC (p.o.) significantly potentiated the inhibitory effect of VCR (i.p.) on tumor growth in nude mice bearing KBv200 xenograft. The LCC and its active component Sin A have remarkable reversal effect on MDR in cancer cells by inhibition of both the function and expression of Pgp and total PKC.

Flurazepam inhibits the P-glycoprotein transport function: An insight to revert multidrug-resistance phenotype

P-glycoprotein mediated drug transport may lead to a multidrug resistance phenotype often associated with a poor response to the successful treatment of a variety of human disorders. Several agents have been found to modulate P-glycoprotein drug resistance, most probably by blocking its transport function. The aim of this study was to examine the effects of some benzodiazepines (bromazepam, chlordiazepoxide, diazepam and flurazepam) able to bind to P-glycoprotein in proteoliposomes on its transport function and ATPase activity in the human cancer cell line, KB-V1. The toxicity of the benzodiazepines drugs towards KB-V1 cells was first evaluated and the non toxic drugs concentrations were used to assess the drug efflux and the ATPase activity. Using the flow cytometry approach, the accumulation and efflux of daunorubicin were followed by measuring the daunorubicin associated geometric mean fluorescence intensity. Vanadate was employed as a comparative inhibitory compound. Flurazepam was able to inhibit the daunorubicin efflux in 80%. ATPase activity determined by a colorimetric assay revealed that flurazepam inhibits the P-glycoprotein enzymatic activity, indicating coupling between drug transport and ATP hydrolysis. Bromazepam, chlordiazepoxide and diazepam behaved as activators of the P-glycoprotein ATPase activity, suggesting a role as transported substrates and did not interfere in the daunorubicin transport.

Folate‐functionalized polymeric micelles for tumor targeted delivery of a potent multidrug‐resistance modulator FG020326

To overcome multidrug resistance (MDR) existing in tumor chemotherapy, polymeric micelles encoded with folic acid on the micelle surface were prepared with the encapsulation of a potent MDR modulator, FG020326. The micelles were fabricated from diblock copolymers of poly(ethylene glycol) (PEG) and biodegradable poly(epsilon-caprolactone) (PCL) with folate attached to the distal ends of PEG chains. The folate-conjugated copolymers, folate-PEG-PCL, were synthesized by multistep chemical reactions. First, allyl-terminated copolymer (allyl-PEG-PCL) was synthesized through a ring-opening polymerization of epsilon-caprolactone in bulk employing monoallyl-PEG as a macroinitiator. Second, the allyl terminal groups of copolymers were converted into primary amino groups by a radical addition reaction, followed by conjugation of the carboxylic group of folic acid. In vitro studies at 37 degrees C demonstrated that FG020326 release from micelles at pH 5.0 was faster than that at pH 7.4. Cytotoxicity studies with MTT assays indicated that folate-functionalized and FG020326-loaded micelles resensitized the cells approximately five times more than their folate-free counterparts (p < 0.01) in human KB(v200) cells treated with vincristine (VCR). The in vitro Rhodamine 123 efflux experiment using MDR KB(v200) cells revealed that when cells were pretreated with folate-attached and FG020326-loaded micelles, the P-glycoprotein (P-gp) drug efflux function was significantly inhibited.

1H and 13C NMR assignments for five anthraquinones from the mangrove endophytic fungus Halorosellinia sp. (No. 1403)

We report the unambiguous assignments of the (1)H and (13)C NMR spectra of two new natural products, namely, 1,4,5,6,7,9-hexahydroxy-2-methoxy-7-methyl-5beta,9beta,8abeta, 6alpha,10aalpha-hexahydroanthracen-10 (10aH)-one (1) and 1,4,6-trihydroxy-2-methoxy-7-methylanthracene-9, 10-dione (2), together with three known anthraquinones. These compounds were all isolated from the marine endophytic fungus No. 1403 collected from the South China Sea. Compounds 3 and 4 were isolated from the marine fungus for the first time. The structures were elucidated by the spectroscopic methods 1D and 2D NMR including COSY, HMQC, HMBC and NOE, and HREIMS. In our cytotoxicity assays, compound 5 showed cytotoxicity toward KB and KBv-200 cells with IC(50) of 1.40 and 2.58 microg/ml, respectively. In addition, the plausible biogenic relationship of compounds 1, 2, 3 and 4 is discussed.

Anthracenedione derivative 1403P-3 induces apoptosis in KB and KBv200 cells via reactive oxygen species-independent mitochondrial pathway and death receptor pathway

Anthracenedione derivatives are potent cytotoxic agents to tumour cells. In this study, we investigated the anticancer activities of anthracenedione derivative 1403P-3 separated from the secondary metabolites of the mangrove endophytic fungus No. 1403. Our results demonatrated that 1403P-3 showed potent cytotoxicity not only to human epidermoid carcinoma drug-sensitive parental KB cells but also to multidrug resistant (MDR) KBv200 cells and the IC50 values were 19.66 and 19.27 μM, respectively. Further research indicated that 1403P-3 induced apoptosis in KB cells and KBv200 cells confirmed by Hoechst 33258 staining, detection of DNA fragmentation and cleavage of poly (ADP-ribose) polymerase (PARP). Furthermore, apoptosis triggered by 1403P-3 was characterized by the loss of mitochondrial membrane potential (ΔΨm), release of cytochrome c, cleavage of Bid, and activation of caspases-2, -3, -7, -8 and -9. Z-IETD-FMK, caspase-8 inhibitor could inhibit the activation of caspase-2 and cleavage of Bid induced by 1403P-3. However, activation of caspase-9 and cleavage of PARP caused by 1403P-3 were not inhibited by Z-IETD-FMK. Additionally, 1403P-3 did not influence the expression level of Bcl-2 and Bax. It is noteworthy that 1403P-3 decreased the generation of reactive oxygen species (ROS) in KB cells and KBv200 cells. DNA binding assay exhibited that apoptosis induced by 1403P-3 was not involved in intercalating to DNA. In summary, 1403P-3 induced apoptosis of KB cells and KBv200 cells through mitochondrial pathway and death receptor pathway. Furthermore, the mitochondrial pathway was independent of reactive oxygen species and activation of caspase-8.

Sipholenol A, a marine‐derived sipholane triterpene, potently reverses P‐glycoprotein (ABCB1)‐mediated multidrug resistance in cancer cells

Through extensive screening of marine sponge compounds, the authors have found that sipholenol A, a sipholane triterpene isolated from the Red Sea sponge, Callyspongia siphonella, potently reversed multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp). In experiments, sipholenol A potentiated the cytotoxicity of several P-gp substrate anticancer drugs, including colchicine, vinblastine, and paclitaxel, but not the non-P-gp substrate cisplatin, and significantly reversed the MDR of cancer cells KB-C2 and KB-V1 in a concentration-dependent manner. Furthermore, sipholenol A had no effect on the response to cytotoxic agents in cells lacking P-gp expression or expressing MDR protein 1 or breast cancer resistance protein. Sipholenol A (IC(50) > 50 microM) is not toxic to all the cell lines that were used, regardless of their membrane transporter status. Accumulation and efflux studies with the P-gp substrate [(3)H]-paclitaxel demonstrated that sipholenol A time-dependently increased the intracellular accumulation of [(3)H]-paclitaxel by directly inhibiting P-gp-mediated drug efflux. In addition, sipholenol A did not alter the expression of P-gp after treating KB-C2 and KB-V1 cells for 36 h and 72 h. However, it efficaciously stimulated the activity of ATPase of P-gp and inhibited the photolabeling of this transporter with its transport substrate [(125)I]-iodoarylazidoprazosin. Overall, the present results indicate that sipholenol A efficiently inhibits the function of P-gp through direct interactions, and sipholane triterpenes are a new class of potential reversing agents for treatment of MDR in P-gp-overexpressing tumors.

FG020326-loaded nanoparticle with PEG and PDLLA improved pharmacodynamics of reversing multidrug resistance in vitro and in vivo

FG020326, a novel imidazole derivative, is a potent multidrug-resistance (MDR) modulator in vitro and in vivo. However, FG020326 is insoluble. PEDLLA-FG020326 is a FG020326-loaded nanoparticle formed with diblock copolymers of poly (ethylene glycol)-block-poly (D,L-lactic acid) (PEG:PDLLA, PEDLLA) that can solubilize FG020326. This work was intended to evaluate the pharmacodynamics of PEDLLA-FG020326 on reversing MDR in vitro and in vivo. Cytotoxicity was determined by tetrazolium assay. The intracellular accumulation and efflux of doxorubicin (Dox) were detected by fluorescence spectrophotometry. The function of P-glycoprotein was examined by Rhodamine 123 (Rh123) accumulation detected by flow cytometry. The KBv200 cell xenograft model was established to investigate the effect of PEDLLA-FG020326 on reversing MDR in vivo. PEDLLA-FG020326 and FG020326 exhibited 56.4- and 35.9-fold activity in reversing KBv200 cells to vincristine (VCR) resistance, respectively and 14.98- and 7.64-fold to Dox resistance, respectively. PEDLLA-FG020326 was much stronger than FG020326, resulting in the increase of Dox and Rh123 accumulation and the decrease of intracellular Dox extrusion in KBv200 cells. Importantly, PEDLLA-FG020326 exhibited more powerful activity than FG020326 in enhancing the effect of VCR against KBv200 cell xenografts in nude mice, but did not appear more toxic. The pharmacodynamics of FG020326 was improved by incorporating it into a micellar nanoparticle formed with PEG-block-PDLLA copolymers.