Apatinib reduces liver cancer cell multidrug resistance by modulating NF-κB signaling pathway

Objectives:This investigation aimed to elucidate the inhibitory impact of apatinib on the multidrug resistance of liver cancer both in vivo and in vitro.Methods:To establish a Hep3B/5-Fu resistant cell line,5-Fu concentrations were gradually increased in the culture media.Hep3B/5-Fu cells drug resistance and its alleviation by apatinib were confirmed via flow cytometry and Cell Counting Kit 8(CCK8)test.Further,Nuclear factor kappa B(NF-κB)siRNA was transfected into Hep3B/5-Fu cells to assess alterations in the expression of multidrug resistance(MDR)-related genes and proteins.Nude mice were injected with Hep3B/5-Fu cells to establish subcutaneous xenograft tumors and then categorized into 8 treatment groups.The treatments included oxaliplatin,5-Fu,and apatinib.In the tumor tissues,the expression of MDRrelated genes was elucidated via qRT-PCR,immunohistochemistry,and Western blot analyses.Results:The apatinibtreated mice indicated slower tumor growth with smaller size compared to the control group.Both the in vivo and in vitro investigations revealed that the apatinib-treated groups had reduced expression of MDR genes GST-pi,LRP,MDR1,and p-p65.Conclusions:Apatinib effectively suppresses MDR in human hepatic cancer cells by modulating the expression of genes related to MDR,potentially by suppressing the NF-κB signaling pathway.

REVERSAL EFFECTS OF MIFEPRISTONE ON MULTIDRUG RESISTANCE(MDR) IN DRUG-RESISTANT BREAST CANCER CELL LINE MCF7/ADR IN VITRO AND IN VIVO

To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human breast cancer cell line MCF7/ADR and its mechanisms. Methods: Expression of MDR1 and MDR-associated protein(MRP) mRNA in MCF7/ADR cells was detected using reverse transcription- polymerase chain reaction(RT-PCR). Western blotting was used to assay the protein levels of P-glycoprotein (P-gp) and MRP. Intracellular rhodamine 123 retention and [3H]vincristine (VCR) accumulation were measured by flow cytometry and liquid scintillation counter, respectively. MTT reduction assay was used to determine the sensitivity of cells to the anticancer agent, adriamycin (ADR). Additionally, a MCF7/ADR cell xenograft model was established to assess the reversal effect of mifeprisone on MDR in MCF7/ADR cells in vivo. Results: Miferpristone dose-dependently down- regulated the expression of MDR1 and MRP mRNA in MCF7/ADR cells, accompanied by a significant decrease in the protein levels of P-gp and MRP. After exposure to 5, 10, and 20 mmol/L mifepristone, MCF7/ADR cells showed a 3.87-, 5.81-, and 7.40-fold increase in the accumulation of intracellular VCR(a known substrate of MRP), and a 2.14-, 4.39-, and 5.53-fold increase in the retention of intracellular rhodamine 123(an indicator of P-gp function), respectively. MTT analysis showed that the sensitivity of MCF7/ADR cells to ADR was enhanced by 7.23-, 13.62-, and 20.96-fold after incubation with mifepristone as above-mentioned doses for 96 h. In vivo, mifepristone effectively restored the chemosensitivity of MCF7/ADR cells to ADR. After 8 weeks of administration with ADR(2 mg穔g-1穌-1) alone or in combination with mifepristone(50 mg穔g-1穌-1), the growth inhibitory rate of xenografted tumors in nude mice was 8.08% and 37.25%, respectively. Conclusion: Mifepristone exerts potent reversal effects on MDR in MCF7/ADR cells in vitro and in vivo through down- regulation of MDR1/P-gp and MRP expression and inhibition of P-gp- and MRP-dependent drug efflux, thus increasing the sensitivity to anticancer drug.

The Activity of Erianin and Chrysotoxine from Dendrobium chrysotoxum to Reverse Multidrug Resistance in B16/h MDR-1 Cells

The ability of two dihydrostilbene derivatives erianin and chrysotoxine from Dendrobium chrysotoxum to reverse multidrug resistant (MDR) cells was investigated using murine B16 melanoma cells transfected with the human MDR 1 gene and crossresistant to vinblastine and adriamycin (B16/h MDR 1 cells). Both of the two compounds were shown to increase the accumulation of adriamycin, the P glycoprotein (P gp) substrate, in B16/h MDR 1 transfectants.

Synergistic Effect of Hyperthermia and Neferine on Reverse Multidrug Resistance in Adriamycin-resistant SGC7901/ADM Gastric Cancer Cells

Multidrug resistance（MDR） plays a major obstacle to successful gastric cancer chemotherapy.The purpose of this study was to investigate the MDR reversal effect and mechanisms of hyperthermia in combination with neferine（Nef） in adriamycin（ADM） resistant human SGC7901/ADM gastric cancer cells.The MDR cells were heated at 42℃ and 45℃ for 30 min alone or combined with 10 μg/mL Nef.The cytotoxic effect of ADM was evaluated by MTT assay.Cellular plasma membrane lipid fluidity was detected by fluorescence polarization technique.Intracellular accumulation of ADM was monitored with high performance liquid chromatography.Mdr-1 mRNA,P-glycoprotein（P-gp）,γH2AX expression and γH2AX foci formation were determined by real-time PCR,Western blot and immunocytochemical staining respectively.It was found that different heating methods induced different cytotoxic effects.Water submerged hyperthermia had the strongest cytotoxicity of ADM and Nef combined with hyperthermia had a synergistic cytotoxicity of ADM in the MDR cells.The water submerged hyperthermia increased the cell membrane fluidity.Both water submerged hyperthermia and Nef increased the intracellular accumulation of ADM.The water submerged hyperthermia and Nef down-regulated the expression of mdr-1 mRNA and P-gp.The water submerged hyperthermia could damage DNA and increase the γH2AX expression of SGC7901/ADM cells.The higher temperature was,the worse effect was.Our results show that combined treatment of hyperthermia with Nef can synergistically reverse MDR in human SGC7901/ADM gastric cancer cells.

Reversing multidrug resistance by RNA interference through the suppression of MDR1 gene in human hepatoma cells

AIM： To reverse the multidrug resistance （MDR） by RNA interference （RNAi）-mediated MDRI suppression in heparoma cells.METHODS： For reversing MDR by RNAi technology, two different short hairpin RNAs （shRNAs） were designed and constructed into pGenSil-1 plasmid, respectively. They were then transfected into a highly adriarnycin-resistant HepG2 hepatorna cell line （HepG2/ADM）. The RNAi effect on MDR was evaluated by real-time PCR, cell cytotoxicity assay and rhodarnine 123 （Rh123） efflux assy. RESULTS： The stably-transfected clones showed various degrees of reversal of MDR phenotype. Surprisingly, the MDR phenotype was completely reversed in two transfected clones. CONCLUSION： MDR can be reversed by the shRNAmediated MDRI suppression in HepG2/ADM cells, which provides a valuable clue to make multidrug-resistant hepatoma cells sensitive to anti-cancer drugs.

Reversal of Multidrug Resistance and Inhibition of Phosphorylation of AKT in Human Ovarian Cancer Cell Line by Wild-type PTEN Gene

The reversing effect of wild-type PTEN gene on resistance of C 13K cells to cisplatin and its inhibitory effect on the phosphorylation of protein kinase B （AKT） were studied. The expression of PTEN mRNA and protein in OV2008 cells and C13K cells were semi-quantitatively detected by using RT-PCR and Western blotting. Recombinant eukaryotic expression plasmid containing human wild-type PTEN gene was transfected into C13K cells by lipofectamine2000. The expression of PTEN mRNA was monitored by RT-PCR and the expression of PTEN, Akt, p-Akt protein were ana- lyzed by Western blotting in PTEN-transfected and non-transfected C13K cells. Proliferation and chemosensitivity of cells to DDP were measured by MTT, and cell apoptosis was detected by flow cytometry after treatment with cisplatin. The expression of PTEN mRNA and protein in OV2008 cells were significantly higher than those in C13K cells. After transfection with PTEN gene for 48 h, the expression of PTEN mRNA and protein in C 13K cells were 2.04 ± 0.10, 0.94± 0.04 respectively and the expression of p-Akt protein （ 0.94± 0.07） was lower than those in control groups （1.68 ±0.14, 1.66± 0.10） （P〈 0.05）. The IC50 of DDP to C 13 K cells transfected with PTEN （7.2± 0.3 la mol/L） was obviously lower than those of empty-vector transfected cells and non-transfected cells （12.7±0.4 lamol/1, 13.0±0.3 lamol/L） （P〈0.05）. The apopototis ratio of wild-type PTEN-transfected, empty vector transfected and non-transfected C13K cells were （41.65___0.87）%, （18.61 ±0.70）% and （15.28±0.80）% respectively, and the difference was statistically significant （P〈0.05）. PTEN gene plays an important role in ovarian cancer multidrug resistance. Transfection of PTEN could increase the expression of PTEN and restore drug sensitivity to cisplatin in human ovarian cancer cell line C 13K with multidrug-resistance by decreasing the expression of p-Akt.

Breast cancer resistance protein(BCRP/ABCG2):its role in multidrug resistance and regulation of its gene expression

Breast cancer resistance protein(BCRP)/ATP-binding cassette subfamily G member 2(ABCG2) is an ATP-binding cassette(ABC) transporter identified as a molecular cause of multidrug resistance(MDR) in diverse cancer cells.BCRP physiologically functions as a part of a self-defense mechanism for the organism;it enhances elimination of toxic xenobiotic substances and harmful agents in the gut and biliary tract,as well as through the blood-brain,placental,and possibly blood-testis barriers.BCRP recognizes and transports numerous anticancer drugs including conventional chemotherapeutic and targeted small therapeutic molecules relatively new in clinical use.Thus,BCRP expression in cancer cells directly causes MDR by active efflux of anticancer drugs.Because BCRP is also known to be a stem cell marker,its expression in cancer cells could be a manifestation of metabolic and signaling pathways that confer multiple mechanisms of drug resistance,self-renewal(stemness),and invasiveness(aggressiveness),and thereby impart a poor prognosis.Therefore,blocking BCRP-mediated active efflux may provide a therapeutic benefit for cancers.Delineating the precise molecular mechanisms for BCRP gene expression may lead to identification of a novel molecular target to modulate BCRP-mediated MDR.Current evidence suggests that BCRP gene transcription is regulated by a number of trans-acting elements including hypoxia inducible factor 1α,estrogen receptor,and peroxisome proliferator-activated receptor.Furthermore,alternative promoter usage,demethylation of the BCRP promoter,and histone modification are likely associated with drug-induced BCRP overexpression in cancer cells.Finally,PI3K/AKT signaling may play a critical role in modulating BCRP function under a variety of conditions.These biological events seem involved in a complicated manner.Untangling the events would be an essential first step to developing a method to modulate BCRP function to aid patients with cancer.This review will present a synopsis of the impact of BCRP-mediated MDR in cancer cells,and the molecular mechanisms of acquired MDR currently postulated in a variety of human cancers.

Overcoming drug efflux-based multidrug resistance in cancer with nanotechnology

Multidrug resistance(MDR),which significantly decreases the efficacy of anticancer drugs and causes tumor recurrence,has been a major challenge in clinical cancer treatment with chemotherapeutic drugs for decades.Several mechanisms of overcoming drug resistance have been postulated.Well known P-glycoprotein(P-gp) and other drug efflux transporters are considered to be critical in pumping anticancer drugs out of cells and causing chemotherapy failure.Innovative theranostic(therapeutic and diagnostic) strategies with nanoparticles are rapidly evolving and are anticipated to offer opportunities to overcome these limits.In this review,we discuss the mechanisms of drug efflux-mediated resistance and the application of multiple nanoparticle-based platforms to overcome chemoresistance and improve therapeutic outcome.

THE CORRELATION BETWEEN THE EXPRESSION OF MULTIDRUG RESISTANCE RELATED GENE AND CELL APOPTOSIS AND CLINICAL SIGNIFICANCE IN NON-SMALL CELL LUNG CANCER

Objective: To explore the correlation and clinical significance between expression of MDR (multidrug resistance) related gene MRP, MDR1, C-erbB-2 and cell apoptosis in non-small cell lung cancer (NSCLC). Methods: RT-PCR, Immunohistochemistry were used to examine the expression of mRNA and protein in the MDR and apoptosis related gene. Apoptosis cells were assayed by Terminal deoxynucleotidyl transferase (TdT)- mediated biotin dUTP nick end-labeling (TUNEL). Results: The positive rates of MRP, MDR1, C-erbB-2, bc1-2, C-myc mRNA in 63 cases NSCLC were 81.0% (51/63), 38.1%(24/63), 47.6%(30/63), 65.1%(41/63), 76.2%(48/63) respectively. Their levels were higher than those of corresponding proteins (74.6%, 34.9%, 46.0%, 61.9%, 71.4%, respectively). The significant association was found between the mRNA level and the protein expression (r =+0.764, P<0.02). The C-myc expression in 2 cases adjacent and benign lung tissue were light positive, and another 3 cases were negative. The positive correlation were demonstrated between C-myc and C-erbB-2 (r=+0.547, p=0.001) as well as bcl-2 and C-erbB-2 (r =+0.486, p=0.023) in NSCLC. There is no any correlation among bcl-2, C-myc and MRP or MDR1. There exists inverse correlation between apoptotic index and bcl-2 (r = -0.587, p = 0.017), and no any correlation among apoptotic index and MRP or MDR1 or C-erbB-2 or C-myc. The average apoptotic index were higher in the effective chemotherapy group (27.2( 2.1, 30.5(1.8) than that in the non-effective chemotherapy group (9.4( 1.3, 12.6( 2.4) with adenocarcinoma and squamous cell carcinoma (p =0.01, p=0.004). The positive rates of bcl-2, MRP, C-erbB-2 expression in the effective chemotherapy group (31.8%, 40.9%, 22.7%, respectively) were lower than those in the non-effective chemotherapy group (77.4%, 90.3%, 67.7%, respectively) (p=0.036, p=0.012, p=0.01), but MDR1 and C-myc expression have no any significant difference (p=0.067, p=0.282). The median survival time in the patients with coexpression of more than three MDR and/or apoptosis related genes are shorter (8.6 months) than that in those patients with coexpression of less than three MDR and/or apoptosis related genes (15.5 months)(p=0.01). Conclusion: The multidrug resistance in NSCLC is not only related to many drug resistance genes, but also involved in cell apoptosis and apoptosis related gene expression. The coexpression of MDR and apoptosis related gene is related to the survival time.

The expression and significance of the multidrug resistance-related proteins P-gp, MRP and LRP in human non-small cell lung cancer tissues

Objective: To explore the expression and significance of the multidrug resistance-related proteins P-glycopro-tein (P-gp), multidrug resistance-related protein (MRP), lung resistance protein (LRP) in human non-small cell lung cancer (NSCLC) tissues and paratumor tissues. Methods: Immunohistochemistry (IHC) was used to examine the expression level of proteins P-gp, MRP and LRP in 43 samples of NSCLC and 15 samples of paratumor tissues. Results: The expression rates of P-gp, MRP and LRP in 43 tumor tissues were 74.42% (32/43), 67.44% (29/43) and 88.37% (38/43), respectively, while in 15 paratumor tissues were 13.33% (2/15), 20.00% (3/15) and 6.67% (1/15), respectively. There was significant difference in the expression of proteins (P-gp, MRP and LRP) between lung cancer tissues and paratumor tissues (P < 0.05). The expres-sion of proteins P-gp, LRP in lung adenocarcinoma were higher than that in other pathological carcinomas (P < 0.05). The expression of protein MRP was not related to pathological type, clinical stage and classification of histodifferentiation (P > 0.05). Conclusion: Multidrug resistance is more common in NSCLC. The proteins of P-gp, MRP and LRP participated in the formation of multidrug resistance in lung cancer. Detection of multidrug resistance-related proteins in lung cancer tissues may be useful to choice drugs.

Chitosan/pshRNA Plasmid Nanoparticles Targeting MDR1 Gene Reverse Paclitaxel Resistance in Ovarian Cancer Cells

In order to investigate the effect of chitosan/pshRNA plasmid nanoparticles targeting MDR1 genes on the resistance of A2780/TS cells to paclitaxel, chitosan/pshRNA plasmid nanoparti- cles were synthesized by means of a complex coacervation technique and transfected into A2780/TS cells. The cells transfected with MDRl-targeted chitosan/pshRNA plasmid nanoparticles were experimental cells and the cells transfected with chitosan/pGPU6/GFP/Neo no-load plasmid nanoparticles served as negative control cells. Morphological features of the nanoparticles were observed under transmission electron microscope （TEM）. MDR1 mRNA expression was assessed by RT-PCR. Half-inhibitory concentration （IC50） ofpaclitaxel for A2780/TS cells was determined by MTT method. TEM showed that the nanoparticles were round-shaped, smooth in surface and the diameters varied from 80 to 120 nm. The MDR1 mRNA in the transfected cells was significantly decreased by 17.6%, 27.8% and 52.6% on the post-transfection day 2, 4 and 7 when compared with that in A2780/TS cells control （P〈0.05）. MTT assay revealed that the relative reversal efficiency was increased over time and was 29.6%, 51.2% and 61.3% respectively in the transfected cells 2, 4, 7 days after transfection and IC_50 （0.197±0.003, 0.144±0.001, 0.120±0.004） were decreased with difference being significant when compared with that in A2780/TS （0.269±0.003） cells control （P〈0.05）. It was concluded that chitosan/pshRNA plasmid nanoparticles targeting MDR1 can effectively reverse the paclitaxel resistance in A2780/TS cells in a time-dependent manner.

Natural Products Modulate the Multifactorial Multidrug Resistance of Cancer

Multidrug resistance (MDR) is a critical problem in cancer chemotherapy. Cancer cells can develop resistance not only to a single cytotoxic drug, but also to entire classes of structurally and functionally unrelated compounds. Several mechanisms can mediate the development of MDR, including increased drug efflux from the cells by ABC-transporters (ABCT), activation of metabolic enzymes, and defective pathways towards apoptosis. Many plant secondary metabolites (SMs) can potentially increase sensitivity of drug-resistant cancer cells to chemotherapeutical agents. The present thesis investigates the modulation of MDR by certain medicinal plants and their active compounds. The inhibition of ABCTs (P-gp/MDR1, MRP1, BCRP) and metabolic enzymes (GST and CYP3A4), and the induction of apoptosis are useful indicators of the efficacy of a potential medicinal drug. The focus of this study was the possible mechanisms of drug resistance including: expression of resistance proteins, activation of metabolic enzymes, and alteration of the apoptosis and how to overcome their resistance effect on cancer cells. The overall goal of this review was to evaluate how commonly used medicinal plants and their main active secondary metabolites modulate multidrug resistance in cancer cells in order to validate their uses as anticancer drugs, introduce new therapeutic options for resistant cancer, and facilitate the development of their anticancer strategies and/or combination therapies. In conclusion, SMs from medicinal plants exhibit multitarget activity against MDR-related proteins, metabolic enzymes, and apoptotic signaling, this may help to overcome resistance towards chemotherapeutic drugs.

Differential expression of breast cancer-resistance protein,lung resistance protein,and multidrug resistance protein 1 in retinas of streptozotocin-induced diabetic mice

AIM：To investigate the altering expression profiles of efflux transporters such as breast cancer-resistance protein（BCRP）,lung resistance protein（LRP）,and multidrug resistance protein 1（MDR1） at the inner blood-retinal barrier（BRB） during the development of early diabetic retinopathy（DR） and/or aging in mice.METHODS：Relative m RNA and protein expression profiles of these three efflux transporters in the retina during the development of early DR and/or aging in mice were examined.The differing expression profiles of Zonula occludens 1（ ZO-1） and vascular endothelial growth factor-A（ VEGFA） in the retina as well as the perfusion characterization of fluorescein isothiocyanate（FITC）-dextran and Evans blue were examined to evaluate the integrity of the inner BRB.RESULTS：There were significant alterations in these three efflux transporters＇ expression profiles in the m RNA and protein levels of the retina during the development of diabetes mellitus and/or aging.The development of early DR was confirmed by the expression profiles of ZO-1 and VEGFA in the retina as well as the compromised integrity of the inner BRB.CONCLUSION：The expression profiles of some efflux transporters such as BCRP,LRP,and MDR1 in mice retina during diabetic and/or aging conditions are tested,and the attenuated expression of BCRP,LRP,and MDR1 along with the breakdown of the inner BRB is found,which may be linked to the pathogenesis of early DR.

Photodynamic therapy of cancer-Challenges of multidrug resistance

Photodynamic therapy(PDT)of cancer is a two-step drug device combination modality,which involves the topical or systemie administration of a photosensitizer followed by light ilumnination of cancer site.In the presence of oxygen molecules,the light illmnination of photosensitizer(PS)can lead to the generation of cytotoxic reactive oxygen species(ROS)and consequently destroy cancer.Similar to many other anticancer therapies,PDT is also subject to intrinsic cancer resistance mediated by mutidrug resistance(MDR)mechanisms.This paper will review the recent progress in understanding the interaction between MDR transporters and PS uptalke.The strategies that can be used in a clinical setting to owercome or bypass MDR will also be discussed.

Inhibition of apoptosis-regulatory protein Siva-1 reverses multidrug resistance in gastric cancer by targeting PCBP1

Introduction:Siva-1,as a pro-apoptotic protein,has been shown to induce extensive apoptosis in a number of different cell lines.In our previous study,we showed that overexpressed Siva-1 decreased the apoptosis of gastric cancer cells.So,we believe that it can also work as an anti-apoptotic protein.The present study aimed to determine the specific role of Siva-1 in anticancer drug resistance in gastric cancer in vivo and in vitro and preliminarily reveal the mechanism.Materials and Methods:A vincristine-resistant MKN-28/VCR gastric cancer cell line with stably downregulated Siva-1 was established.The effect of Siva-1 downregulation on chemotherapeutic drug resistance was assessed by measuring the IC50 and pump rate of doxorubicin.Proliferation,apoptosis of cells,and cell cycle were detected via colony formation assay andflow cytometry,respectively.Additionally,migration and invasion of cells was detected via wound healing and transwell assays.Moreover,we determined in vivo effects of LV-Siva-1-RNAi on tumor size,and apoptotic cells in tumor tissues were detected using TUNEL and hematoxylin and eosin staining.Results:Siva-1 downregulation reduced the pump rate of doxorubicin and enhanced the response to drug treatment.Siva-1 negatively regulated proliferation and promoted apoptosis of cells by potentiality G2-M phase arresting.Inhibition of Siva-1 expression in MKN-28/VCR cells significantly weakened wound healing ability and decreased invasion ability.Poly(C)-binding protein 1(PCBP1)was identified as a Siva-1-interacting protein in yeast two-hybrid screening.Semiquantitative RT-PCR and western blotting revealed that Siva-1 downregulation could inhibit expression of PCBP1,Akt,and NF-κB and eventually decrease the expression of MDR1 and MRP1.Conclusion:The current study demonstrated that the downregulation of Siva-1,which functions as a regulator of MDR1 and MRP1 gene expression in gastric cancer cells by inhibiting PCBP1/Akt/NF-κB signaling pathway expression,enhanced the sensitivity of gastric cancer cells to certain chemotherapies.

REVERSION OF MULTIDRUG RESISTANCE IN THE P-GLYCOPROTEIN POSITIVE BREAST CANCER CELL LINE(MCF-7/ADR) BY INTRODUCTION OF HAMMERHEAD RIBOZYME

A hammerhead ribozyme which site-specifically cleaved the GUC position in canon 880 of the mdr1 mRNA was designed. The target site was chosen between the two ATP binding sites, which may be important for the function of the P-Gp as an ATP-dependent pump. A DNA sequence encoding the ribozyme gene was then incorporated into a eukaryotic expression vector (pH Apr-1 neo) and transfected into the breast cancer cell line MCF-7/Adr, which is resistant to adriamycin and expresses the MDR phenotype. The ribozyme was stably expressed in the cell line by the RNA dot blotting assay. The result of Northern blot assay showed that the expressed ribozyme could decrease the level of mdrl mRNA expression by 83. 5 %; and the expressed ribozyme could inhibite the formation of p-glycoprotein detected by immuno- cy-tochemistry assay and could reduce the cell’s resistance to adrimycin; this means that the resistant cells were 1 000-fold more resistant than the parental cell line(MCF-7), whereas those cell clones that showed ribozyme expression were only 6-fold more resistant than the parental cell line. These results show that a potentially useful tool is at hand which may inactivate MDR1 mRNA and revert the multidrug resistance phenotype.

In Vitro Study of Ultrasound on Multidrug Resistance in MDR Human Hepatoma HepG_2 Cells

OBJECTIVE The aim of the study was to examine the reversal effects of ultrasound （US） on the MDR in HepG2/ADM, a HepG2 cell line resistant to Adriamycin （ADM）, and to study the mechanism of US action.METHODS Using the MTT assay, the effects of US on MDR in HepG2/ADR cells were studied. Before and after the treatment with 0.5 W/cm^2 low intensity ultrasound （LIUS）, the expression of the MDR-related genes, mdrl, mrp and lrp was assayed with the reverse transcriptase polymerase chain reaction （RT-PCR） and the levels of their respective protein expression determined by flow cytometry. By using confocal laser scanning microscopy （CLSM）, we examined the intracellular daunorubicin （DNR） distribution, and the effects on the cells of treatment with US or DNR.RESULTS LIUS significantly reversed MDR in HepG2/ADR cells. After treatment with LIUS at 0.5 W/cm^2, chemosensitivity to ADM and DNR increased 3.35-fold and 2.81-fold, respectively. The reversal activity by LIUS plus verapamil （VER） was stronger than with either US or VER alone. After treatment with 0.5 W/cm^2, the expression of both the MDR1 and the MRP mRNA genes began to decline （P 〈 0.01 and P 〈 0.05, respectively）; the expression of LRP showed no significant changes. Changes in the expression of the P-glycoprotein （P-gp） and MRP were similar to those of their mRNA expressions. Results of the CLSM showed that administration of US （0. 5 W/cm^2） or VER （15.7 uM） with DNR to HepGa/ADM cells showed a significant change in the distribution of DNR in the cells.CONCLUSION Our results show that LIUS can reverse MDR. The reversal effects are stronger than those of either US or VER alone, when combined with VER administration. As LIUS is noninvasive causing no toxicity, it might have potential for clinical application. The reversal mechanism needs further study.

EXPRESSION OF MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN (MRP) AND ITS RELATIONSHIP WITH CLINICOPATHOLOGICAL FACTORS IN NON-SMALL CELL LUNG CANCER

Objective: To investigate the relationship between the expression of multidrug resistance-associated protein (MRP) and clinicopathological factors and prognosis. Methods: The expression of MRP in 62 cases with non-small cell lung cancer (NSCLC) was detected using immunohistochemistry method. The expression of MRP in 30 cases of NSCLC and corresponding normal lung tissues were detected using immunohistochemistry and Western Blot. Results: this study of tumor tissues confirmed the plasma membrane and/or cytoplasm locations of MRP. There was apparent difference between normal lung tissues and NSCLC in MRP. The survival analysis of 62 NSCLC showed that the mean survival time of the patients with negative MRP expression was 69.8117.41 months and that of patients with positive MRP expression, 25.384.46 months. Log-rank test suggested that the difference between them was significant (P=0.0156). It was also found that in squamous cell lung cancer the statistically significant difference between the mean survival time of patients with positive MRP expression and those with negative MRP expression (P=0.0153). Multivariate Cox model analysis suggested that the survival time was significantly related to expression of MRP (P=0.035) and lymphatic metastasis (P=0.038). Conclusion: MRP expression in NSCLC is significantly higher compared with normal lung tissues. The mean survival time of patients with negative MRP was relative longer and expression of MRP was an independent factor for prognosis.

Apoptosis Rate and Objective Diagnosis of Drug Resistance of Ovarian Cancer Cell Lines

Objective： To investigate whether the change of drug resistance degree could be evaluated by apoptotic rate in ovarian cancer cell lines. Methods： Human epithelia ovarian cancer cell line A2780 and its platinum （DDP） resistance cell line AD4 were used. They were divided into 4 groups respectively （A2780-DDP group, A2780-DDP＋VRM group, AD4-DDP group and AD4-DDP＋VRM group）. 3-（4, 5- dimethylthiazol-2-yl）-2, 5-diphenyl-2H-tetrazolium bromide （MTT） was used to measure the multiple of drug resistance. The expression of drug-resistance genes （mdrl, TopoⅡα and GSTπ） was detected by using reverse transcription polymerase chain reaction （RT-PCR）. Semi-quantity assay was proceed by rate the of multidrug resistance genes to G3 PDH gene. Apoptosis was measured by DNA gel electrophoresis and flow cytometry respectively. The advantages and disadvantage of evaluating drug-resistance with these three methods were analyzed. Results： The 50% inhibition concentration （IC50） of A2780 and AD4 was 19.2 μg/mL and 66 μg/mL respectively, and the resistance fold of the AD4 was 3.4. Some drug-resistance genes could be detected by RT-PCR in A2780 and AD4 cell lines. The expression of mdrl was only （0.09±0.03）×10^-2 ： 1 and （0.10±0.02） × 10^-2：1 respectively （rate to G3 PDH gene） with the difference being not significant between them. The expression of TopoⅡα in the A2780 cells was （2.60±0.12）×10^-2：1 and （0.11±0.03）× 10^-2：1 in the AD4 cells respectively with the difference between them being significant. On the contrary, the expression of GSTπ in A2780 cells was lower than in AD4 cells, and the ratio was （0.11±0.03）×10^-2：1 and （3.13±0.14）×10^-2：1 respectively with tile difference being significant between them. There was no significant difference among the genes expression after the drugs were given for 6 h, 12 h and 24 h. couldn＇t reflect the change of drug-resistance timely. DNA gel electrophoresis used to detect apoptosis was only a qualitative analysis. Different drug resistance degrees may be detected by flow cytometry as early as few hours after drugs were given, which realized the earlier and quantities detection of drug resistance. Conclusion： Detection of apoptosis with flow cytometry may not be affected by the variety of drug-resistance genes, suggested this was a general, quantitative and objective method to reflect drug resistance.

Nanotechnology-based combination therapy for overcoming multidrug-resistant cancer

Multidrug resistance(MDR) is a major obstacle to successful cancer treatment and is crucial to cancer metastasis and relapse.Combination therapy is an effective strategy for overcoming MDR. However, the different pharmacokinetic(PK) profiles of combined drugs often undermine the combination effect in vivo, especially when greatly different physicochemical properties(e.g.,those of macromolecules and small drugs) combine. To address this issue, nanotechnology-based codelivery techniques have been actively explored. They possess great advantages for tumor targeting, controlled drug release, and identical drug PK profiles. Thus,a powerful tool for combination therapy is provided, and the translation from in vitro to in vivo is facilitated. In this review, we present a summary of various combination strategies for overcoming MDR and the nanotechnology-based combination therapy.