MDR1 Gene Expression Research Articles

A major compound isolated from Undaria Pinnatifida downregulates CYP3A4 and MDR1 expression by antagonizes pregnane X receptor activation

Pregnane X receptor (PXR) has been reported to regulate the expression of drug‐metabolizing enzymes, such as CYP3A4 and MDR1. A major carotenoid which isolated from brown sea algae, Undaria Pinnatifida, compound A, is a putative chemopreventive agent. In this study, we determined whether compound A may overcome inducer‐drug interaction through attenuation of rifampin‐induced CYP3A4 and MDR1 gene expression by PXR‐mediated pathways in HepG2 hepatoma cells. We found that compound A significantly attenuated rifampin‐induced CYP3A4 and MDR1 mRNA and CYP3A4 protein expression at 24 h of incubation. Mechanistically, compound A strongly attenuated the PXR‐mediated CYP3A4 promoter activity in HepG2 cells. In addition, compound A attenuated CAR‐and rPXR‐mediated CYP3A4 promoter activity in this cell line. Using the mammalian two‐hybrid assay, we found that compound A significantly decreased the interaction between PXR and SRC‐1, a PXR co‐activator. Thus, this compound A can decrease rifampin‐induced CYP3A4 and MDR1 expression through attenuation of PXR‐mediated CYP3A4 promoter activation and interaction between PXR and co‐activator. These findings could lead to potentially important new therapeutic and dietary approaches to reduce the frequency of adverse drug reactions.

Bioimaging Real-Time PXR-Dependent mdr1a Gene Regulation in mdr1a.fLUC Reporter Mice

The MDR1 gene encodes P-glycoprotein, a transmembrane drug efflux transporter that confers multidrug resistance in cancer cells and affects drug pharmacokinetics by virtue of its expression in the liver, kidney, and colon. Nuclear receptors human steroid and xenobiotic receptor (SXR) and constitutive androstane receptor (CAR) are possible master regulators of xenobiotic-inducible MDR1 expression in drug processing organs, but the mechanism of MDR1 regulation has yet to be directly demonstrated in vivo. Moreover, it has previously been impossible to determine the sustained or cumulative effect of repeated doses of xenobiotics on in vivo MDR1 expression. We previously reported a mouse model containing firefly luciferase (fLUC) knocked into the mdr1a genomic locus, allowing noninvasive bioimaging of intestinal mdr1a gene expression in live animals. In the current study, we crossed mdr1a.fLUC mice into the pxr knockout (pxr(-/-)) genetic background and injected mice with pregnenolone-16α-carbonitrile (PCN), a strong mouse pregnane X receptor (PXR) ligand, and two therapeutically relevant taxanes, paclitaxel and docetaxel. All three agents induced mdr1a.fLUC expression (bioluminescence), but only PCN and docetaxel appeared to act primarily via PXR. Luminescence returned to baseline by 24-48 hours after drug injection and was reinducible over two additional rounds of drug dosing in pxr(+/+) mice. TCPOBOP, a CAR ligand, modestly induced mdr1a.fLUC in pxr(+/+) and pxr(-/-) strains, consistent with CAR's minor role in mdr1a regulation. Collectively, these results demonstrate that the mdr1a.fLUC bioimaging model can capture changes in mdr1 gene expression under conditions of repeated xenobiotic treatment in vivo and that it can be used to probe the mechanism of gene regulation in response to different xenobiotic agents.

Emodin sensitizes the gemcitabine-resistant cell line Bxpc-3/Gem to gemcitabine via downregulation of NF-κB and its regulated targets

The aim of this study was to evaluate whether emodin can overcome the chemoresistance of the gemcitabine-resistant cancer cell line (Bxpc-3/Gem) in vitro. The cell line Bxpc-3/Gem was derived from the human pancreatic cancer cell line Bxpc-3. We found that Bxpc-3/Gem cells were characterized by a series of morphological changes with a resistance index of 43.51 comparing with the parental cell line. Emodin reduced Bxpc-3/Gem cell proliferation in a dose-dependent manner. Emodin and gemcitabine combination treatments resulted in decreased cell proliferation and increased apoptosis in Bxpc-3/Gem cells. In addition, combination treatments resulted in downregulation of gene and protein expression of MDR-1 (P-gp), NF-κB, XIAP, survivin, as well as inhibition of NF-κB activity and P-gp function. These observations suggest that emodin may sensitize the pancreatic cancer gemcitabine-resistant cell line Bxpc-3/Gem to gemcitabine therapy via inhibition of survival signaling.

Molecular and cellular effects of vitamin B12 in brain, myocardium and liver through its role as co-factor of methionine synthase

Vitamin B12 (cobalamin, cbl) is a cofactor of methionine synthase (MTR) in the synthesis of methionine, the precursor of the universal methyl donor S-Adenosylmethionine (SAM), which is involved in epigenomic regulatory mechanisms. We have established a neuronal cell model with stable expression of a transcobalamin-oleosin chimer and subsequent decreased cellular availability of vitamin B12, which produces reduced proliferation, increased apoptosis and accelerated differentiation through PP2A, NGF and TACE pathways. Anti-transcobalamin antibody or impaired transcobalamin receptor expression produce also impaired proliferation in other cells. Consistently, the transcription, protein expression and activity of MTR are increased in proliferating cells of skin and intestinal epitheliums, in rat intestine crypts and in proliferating CaCo2 cells, while MTR activity correlates with DNA methylation in rat intestine villi. Exposure to nitrous oxide in animal models identified impairment of MTR reaction as the most important metabolic cause of neurological manifestations of B12 deficiency. Early vitamin B12 and folate deprivation during gestation and lactation of a 'dam-progeny' rat model developed in our laboratory is associated with long-lasting disabilities of behavior and memory capacities, with persisting hallmarks related to increased apoptosis, impaired neurogenesis and altered plasticity. We found also an epigenomic deregulation of energy metabolism and fatty acids beta-oxidation in myocardium and liver, through imbalanced methylation/acetylation of PGC-1alpha and decreased expression of SIRT1. These nutrigenomic effects display similarities with the molecular mechanisms of fetal programming. Beside deficiency, B12 loading increases the expression of MTR through internal ribosome entry sites (IRES) and down-regulates MDR-1 gene expression. In conclusion, vitamin B12 influences cell proliferation, differentiation and apoptosis in brain. Vitamin B12 and folate combined deficiency impairs fatty acid oxidation and energy metabolism in liver and heart through epigenomic mechanisms related to imbalanced acetylation/methylation. Some but not all of these effects reflect the upstream role of vitamin B12 in SAM synthesis.

Role of Conventional Chemosensitivity Test and Tissue Biomarker Expression in Predicting Response to Treatment of Peritoneal Carcinomatosis From Colon Cancer

Background5-Fluorouracil- or oxaliplatin-based regimens are the treatments of choice in patients with PC from colon cancer. There are currently no useful preclinical evaluations to guide the decision-making process for tailored therapy. The aim of the present study was to compare the advantages and limits of a conventional in vitro chemosensitivity test with those of a panel of biomolecular markers in predicting clinical response to different drugs used to treat colon cancer-derived PC. Patients and MethodsFresh surgical biopsy specimens were obtained from 28 patients with peritoneal carcinomatosis from colon cancer. TS, TP, DPD, MDR1, MRP-1, MGMT, BRCA1, ERCC1, GSTP1, and XPD gene expression levels were determined by real-time reverse transcription polymerase chain reaction. An in vitro chemosensitivity test was used to define a sensitivity or resistance profile to the drugs used to treat each patient. ResultsExpression levels of the genes analyzed were generally poorly related to each other. TS and ERCC1 expression was inversely related to response to 5-FU-and/or oxaliplatin-containing regimens. Significant predictivity in terms of sensitivity but poor predictivity of resistance (56.2%) (P = .037) were observed for ERCC1 expression (90%), and high predictivity of resistance (100%) but very low predictivity of sensitivity (40%) (P = .014) were registered for TS. The best overall and significant predictivity was observed for chemosensitivity test results (62.5% sensitivity and 89% resistance; P = .005). ConclusionsSensitivity and resistance to drugs used in vivo was better defined by the chemosensitivity test than by biomarker expression.

Expression of multidrug resistance 1 and multidrug resistance-related protein 1 in C57BL/6 mice treated with benzene

ATP-binding cassette super family (ABC) proteins are considered key to oncology and pharmacology studies. We examined the effect of benzene on ABC pump protein levels in C57BL/6 mouse bone marrow mononuclear cells. After a 2-week gavage (200 mg/kg, 5 days per week), the number of peripheral leukocytes, lymphocytes and basophils dropped significantly; there was also a significant decrease in MDR1 and MRP1 gene expression. A significant reduction in expression of P-gp was found; however, there was no significant decrease in the expression of MRP1 and NF-κB p65. We conclude that regulation of membrane efflux transport protein could be a factor in benzene hematotoxicity.

Reversal of P-glycoprotein-mediated multidrug resistance of human hepatic cancer cells by Astragaloside II

Chemoresistance is the main obstacle encountered in cancer treatment and is frequently associated with multidrug resistance (MDR). Astragaloside is a saponin which is widely used in traditional Chinese medicine. It has been reported that Astragaloside has antitumour effects on hepatocellular carcinoma Bel-7402 cells in vitro and in vivo. The purpose of this study was to examine the effects of Astragaloside II on the reversal of MDR and its molecular mechanism in vitro. In this study, Bel-7402 and Bel-7402/FU cell lines were used as the experimental model. Drug sensitivity was determined using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, accumulation and efflux of Rh123 were analyzed by flow cytometer, the mRNA level of mdr1 was determined by RT-PCR and the protein levels of P-glycoprotein (P-gp) and mitogen-activated protein kinase were determined by Western blot. Astragaloside II (0.08 mg/ml) showed strong potency to increase 5-fluorouracil cytotoxicity toward 5-fluorouracil-resistant human hepatic cancer cells Bel-7402/FU. The mechanism of Astragaloside II on P-gp-mediated MDR demonstrated that Astragaloside II significantly increased the intracellular accumulation of rhodamine 123 via inhibition of P-gp transport function. Based on the analysis of P-gp and mdr1 gene expression using Western blot and RT-PCR, the results revealed that Astragaloside II could downregulate the expression of the P-gp and mdr1 gene. In addition, Astragaloside II suppressed phosphorylation of extracellular signal regulated kinase 1/2, p38 and c-Jun N-terminal kinase. The results suggested that Astragaloside II is a potent MDR reversal agent and may be a potential adjunctive agent for hepatic cancer chemotherapy.

Modulation of multidrug resistance gene expression in peripheral blood mononuclear cells of lung cancer patients and evaluation of their clinical significance

Multidrug resistance is one of the major obstacles to the successful treatment of non-small cell lung cancer (NSCLC). An ability to identify molecular markers of drug resistance in peripheral blood cells in order to better target treatment would therefore be extremely useful in selecting therapy protocols for patients. The aim of the present study was to evaluate whether expression of resistance genes (MDR1, MRP3 and LRP) can predict clinical outcome in NSCLC patients treated with paclitaxel and carboplatin. Peripheral blood samples were obtained from lung cancer patients before and after chemotherapy and expression of the resistance gene in polymononuclear cells was detected by real-time reverse-transcription polymerase chain reaction. The results were correlated with treatment response and overall survival, which was calculated according to the Kaplan-Meier method. MDR1 expression levels in PMNs rose rapidly within 24h post-administration of paclitaxel and carboplatin, whereas MRP and LRP expression levels remained unchanged. However, no significant correlation was observed between MDR1 expression and the patients' survival or treatment response. Modulation of MDR1 gene expression in PMNs after lung cancer treatment with paclitaxel and carboplatin cannot be used as a prognosis marker in these patients.

The Mevalonate Pathway and Downstream Signal Transducers As Therapeutic Targets to Overcome Multidrug Resistance in Chronic Lymphocytic Leukemia (CLL)

AbstractAbstract 3881 Background:The mutational status of tumor immunoglobulin heavy chain variable region (IGHV) is a reliable prognosticator in chronic lymphocytic leukemia (CLL): patients with unmutated (UM) IGHV have a worse prognosis than patients with mutated (M) IGHV. The tumor microenvironment actively supports the survival of CLL cells and confers a multidrug resistance (MDR) phenotype to CLL cells. MDR is due to the over-expression of membrane transporters, like P-glycoprotein (Pgp), which actively extrudes several anticancer drugs. Pgp is under the positive control of the transcription factor Hypoxia-Inducible-Factor-1-alfa (HIF-1α) which is activated by isoprenylated Ras/Rho-dependent downstream signaling pathways. Ras and Rho isoprenylation are regulated by the mevalonate (Mev) pathway activity suggesting that this pathway can be exploited as a metabolic checkpoint to regulate chemresistance. Aim:The aim of this study was twofold: 1) to investigate the correlation between chemoresistance and the activity of the Mev pathway and Ras/Rho-A downstream signaling pathways in purified M and UM CLL cells under basal conditions and after incubation with stromal cells; 2) to evaluate the chemosensitizing effects of agents specifically targeting the Mev pathway and downstream signaling pathways under the same culture conditions. Methods:M and UM CLL cells were cultured in the presence and in the absence of murine stromal cells (M210B4) and exposed to Zoledronic acid (ZA) (1 μmol/L), Simvastatine (Sim) (1 μmol/L), ERK1/2 kinase inhibitor PD98059 (10 μmol/L), HIF-1α inhibitor YC-1 (10 μmol/L) and Doxorubicine (Doxo) (1 μmol/L). The Mev pathway activity was measured by cells radiolabelling with [14C]-mevalonic acid and thin layer chromatography. Ras, ERK1/2 and Akt activity were detected by Western blot. Rho, Rho Kinase and HIF-1α activity were assessed by ELISA. Mdr1 expression was measured by Real Time-PCR. PgP activity was evaluated by measuring Doxo intracellular accumulation. Doxo cytotoxicity was assessed by annexin V and propidium iodide staining. Results:The Mev pathway is significantly more active in UM than in M CLL cells. This hypermetabolic activity translates into a higher activation of Ras/Akt and Rho/Rho kinase signaling pathways and higher expression of the phosphorylated active form of HIF-1α. HIF-1α activation positively regulates mdr1 gene expression in UM CLL cells leading to a more effective Doxo extrusion and therefore better survival upon Doxo exposure. M210B4 stromal cells further protect UM CLL cells from Doxo induced cell death by upregulating Mev pathway activity, HIF-1α/mdr1/PgP axis activation, and Doxo extrusion. Targeting the Mev pathway of UM cells with ZA and Mev reduces the basal activity of HIF-1α/mdr1/PgP axis and significantly increases Doxo retention and cytotoxicity. Similar effects are obtained with PD85 and YC1–10 which are specific inhibitors of the downstream molecules ERK-1/2 and HIF-1α, respectively. All these agents are able to overcome the protective effect exerted by stromal cells by significantly increasing PgP activity and Doxo-induced cell death. Conclusions:Our data demonstrate that the Ras- and Rho-dependent HIF-1α/mdr1/PgP axis is more active and associated with higher levels of MDR in UM compared with M CLL cells. Targeting the Mev pathway and/or downstream signalling pathways is a promising strategy to circumvent basal and stroma-mediated chemoresistance especially in UM CLL cells. Disclosures:Massaia:Novartis Farma S.p.A: Honoraria, Research Funding.

MDR1 gene expression in peripheral blood as a marker of treatment response in lung cancer.

96 Background: Non-small cell lung cancer (NSCLC) is sometimes chemoresistant and does not respond to treatment; several factors are involved in the development of chemoresistance, such as multidrug resistance (MDR) phenotype, mainly. Methods: We studied MDR1 gene expression in peripheral blood PMN of 23 patients with NSCLC, advanced stages in most of the cases, who had not received treatment previously, before (hour 0) and after (hour 6) paclitaxel-carboplatin treatment. RNA was obtained from PMN pellet by means of the protocol of trizol. RNA was checked with agarose gels, and later RT-PCR technique was carried out using specific primers. Expression levels were randomly distributed, so that overexpression under 3 was considered low level of expression, and overexpression above 4 was considered high level of expression. Results: After treatment, we found overexpression of MDR1 in 22 patients. High levels were found in 11 patients, and low levels were observed in the other 11 patients. No relation was found between this fact and the treatment response or survival rate. No significant differences in expression were found in the other variables: gender, tobacco habit, weight loss at the diagnosis, tumour staging, and tumor histology. Conclusions: We can conclude that MDR1 expression in peripheral blood is not a predictive factor for treatment response nor a prognostic factor of the disease. Despite these results, further studies are necessary on molecular biology of NSCLC in order to try to establish subgroups of patients based on genetic profiles, in which the use of microarrays could be very useful.

Therapeutic Delivery of siRNA Silencing HIF-1 Alpha with Micellar Nanoparticles Inhibits Hypoxic Tumor Growth

The particular characteristics of the tumor microenvironment have the potential to strongly promote tumor growth, metastasis and angiogenesis and induce drug resistance. Therefore, the development of effective, systemic therapeutic approaches specifically based on the tumor microenvironment is highly desirable. Hypoxia-inducible factor-1α (HIF-1α) is an attractive therapeutic target because it is a key transcription factor in tumor development and only accumulates in hypoxic tumors. We report here that a cationic mixed micellar nanoparticle (MNP) consisting of amphiphilic block copolymers poly(ε-caprolactone)-block-poly(2-aminoethylethylene phosphate) (PCL(29)-b-PPEEA(21)) and poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL(40)-b-PEG(45)) was a suitable carrier for HIF-1α siRNA to treat hypoxic tumors, which showed an average diameter of 58.0 ± 3.4 nm. The complex MNP(siRNA), formed by the interaction of MNP and siRNA, was transfected into PC3 prostate cancer cells efficiently, while the inhibition of HIF-1α expression by MNP loaded with HIF-1α siRNA (MNP(siHIF)) blocked PC3 cell proliferation, suppressed cell migration and disturbed angiogenesis under in vitro hypoxic mimicking conditions. It was further demonstrated that systemic delivery of MNP(siHIF) effectively inhibited tumor growth in a PC3 prostate cancer xenograft murine model without activating innate immune responses. Moreover, delivery of MNP(siHIF) sensitized PC3 tumor cells to doxorubicin chemotherapy in vitro and in vivo by downregulating MDR1 gene expression which was induced by hypoxia. The underlying concept of use of MNP(siHIF) to block HIF-1α holds promise as an example of a clinical approach using specific siRNA therapy for cancer treatment aimed at the hypoxic tumor microenvironment.

Hyaluronan-CD44v3 Interaction with Oct4-Sox2-Nanog Promotes miR-302 Expression Leading to Self-renewal, Clonal Formation, and Cisplatin Resistance in Cancer Stem Cells from Head and Neck Squamous Cell Carcinoma

Human head and neck squamous cell carcinoma (HNSCC) is a highly malignant cancer associated with major morbidity and mortality. In this study, we determined that human HNSCC-derived HSC-3 cells contain a subpopulation of cancer stem cells (CSCs) characterized by high levels of CD44v3 and aldehyde dehydrogenase-1 (ALDH1) expression. These tumor cells also express several stem cell markers (the transcription factors Oct4, Sox2, and Nanog) and display the hallmark CSC properties of self-renewal/clonal formation and the ability to generate heterogeneous cell populations. Importantly, hyaluronan (HA) stimulates the CD44v3 (an HA receptor) interaction with Oct4-Sox2-Nanog leading to both a complex formation and the nuclear translocation of three CSC transcription factors. Further analysis reveals that microRNA-302 (miR-302) is controlled by an upstream promoter containing Oct4-Sox2-Nanog-binding sites, whereas chromatin immunoprecipitation (ChIP) assays demonstrate that stimulation of miR-302 expression by HA-CD44 is Oct4-Sox2-Nanog-dependent in HNSCC-specific CSCs. This process results in suppression of several epigenetic regulators (AOF1/AOF2 and DNMT1) and the up-regulation of several survival proteins (cIAP-1, cIAP-2, and XIAP) leading to self-renewal, clonal formation, and cisplatin resistance. These CSCs were transfected with a specific anti-miR-302 inhibitor to silence miR-302 expression and block its target functions. Our results demonstrate that the anti-miR-302 inhibitor not only enhances the expression of AOF1/AOF2 and DNMT1 but also abrogates the production of cIAP-1, cIAP-2, and XIAP and HA-CD44v3-mediated cancer stem cell functions. Taken together, these findings strongly support the contention that the HA-induced CD44v3 interaction with Oct4-Sox2-Nanog signaling plays a pivotal role in miR-302 production leading to AOF1/AOF2/DNMT1 down-regulation and survival of protein activation. All of these events are critically important for the acquisition of cancer stem cell properties, including self-renewal, clonal formation, and chemotherapy resistance in HA-CD44v3-activated head and neck cancer.

Modulation of Drug Resistance in Ovarian Cancer Cells by Inhibition of Protein Kinase C-alpha (PKC-α) with Small Interference RNA (siRNA) Agents

To determine whether silence of PKC-α expression by small interference RNA (siRNA) might regulate MDR1 expression and reverse chemoresistance of ovarian cancer. We measured gene and protein expression of MDR1 and PKC-α in ovarian cancer cells and assessed their correlation with cell drug resistance. We also examined whether blocking PKC-α by RNA interference (RNAi) affected MDR1 expression and reversed drug resistance in drug sensitivity tests. The drug resistance cell lines, OV1228/DDP and OV1228/Taxol, had higher gene and protein expression of MDR1 and PKC-α than their counterpart sensitive cell line, OV1228. SiRNA depressed PKC-α gene protein expression, as well as MDR1 and protein expression and improved the drug sensitivity in OV1228/DDP and OV1228/Taxol cells. These results indicated that decreasing PKC-α expression with siRNA might be an effective method to improve drug sensitivity in drug resistant cells with elevated levels of PKC-α and MDR1. A new siRNA-based therapeutic strategy targeting PKC-α gene could be designed to overcome the chemoresistance of ovarian cancer.

Reversion of P-glycoprotein-mediated multidrug resistance by guggulsterone in multidrug-resistant human cancer cell lines

Multidrug resistance (MDR) presents a serious problem in cancer chemotherapy. Our previous studies have shown that guggulsterone could reverse MDR through inhibiting the function and expression of P-glycoprotein (P-gp). The present study is to further investigate the reversal effects of guggulsterone on MDR in drug-resistant cancer cell lines. The effects of guggulsterone on MDR1mRNA gene expression, intracellular pH, P-gp ATPase activity and glucosylceramide synthase (GCS) expression were assessed by RT-PCR, Laser Scanning Confocal Microscope using the pH-sensitive fluorescent probe BCECF-AM, Pgp-Glo assay system, and flow cytometric technology, respectively. The results showed that guggulsterone ranging from 2.5 to 80μM significantly promoted the activity of P-gp ATPase in a dose-dependent manner. The intracellular pH of K562/DOX cells was found to be higher than K562 cells. After treatment with guggulsterone (1, 3, 10, 30, 100μM), intracellular pH of K562/DOX cells decreased in a dose- and time-dependent manner. However, the present study revealed that guggulsterone ranging from 3 to 100μM had little influence on MDR1 gene expression in K562/DOX cells. Further, the isogenic doxorubicin-resistant MCF-7/DOX cells exhibited a 4.9-fold increase in GCS level as compared with parental MCF-7 human breast cancer cells. After treatment with guggulsterone (0.1, 1, 10μM) for 48h, MCF-7/DOX cells were found to have no change of GCS protein expression amount. Guggulsterone might be a potent MDR reversal agent, and its mechanism on MDR needs more research.

Increased expression and function of P-glycoprotein in peripheral blood CD56+ cells is associated with the chemoresistance of non-small-cell lung cancer

Chemoresistance is common among non-small-cell lung cancer (NSCLC), P-glycoprotein (P-gp), encoded by the human multi-drug-resistant MDR1 gene, and multidrug-resistance protein 1 (MRP1) might be major contributors. The aim of the present study was to develop an effective method to investigate the expression and function of P-gp in the peripheral CD56+ cells in order to clarify their correlation with the chemoresistance in NSCLC. Using microbead technology and a RT-qPCR methodology, we evaluated the expression levels of P-gp and MRP1 in the purified CD56+ cells in the chemoresistance and chemo-naive NSCLC patients compared with that in the healthy volunteers. Flow cytometric analysis was used to investigate the changes of P-gp function in the CD56+ cells between the three cohorts. The MDR1 gene expression was elevated markedly (twofold-tenfold), and P-gp function was increased in the chemoresistance cohort compared with the chemo-naive and the healthy cohorts; whereas there was only about two times averagely elevated for the MRP1 gene expression. No statistical significance (p > 0.05) was seen with respect to the expression of MDR1 and MRP1, the function of P-gp between the chemo-naive and the healthy cohorts. P-gp in peripheral CD56+ cells demonstrated possible clinical relevance as predictive biomarkers for the identification of chemoresistance in NSCLC, while MRP1 may not play a significant role in the drug resistance in NSCLC. The potential applications for this finding are provided evidence to screen the potential P-gp reversors and to diagnose and manage the chemoresistance in NSCLC patients.

UbcH10 expression provides a useful tool for the prognosis and treatment of non-small cell lung cancer

To investigate the expression pattern of UbcH10 in non-small cell lung cancer (NSCLC) and its correlations with clinicopathological features and prognostic value in NSCLC patients. The UbcH10 expression in NSCLC tissues, SK-MES-1, and A549 lung cancer cell lines was evaluated, and its correlation with clinicopathological features and prognostic value in NSCLC patients was examined by Kaplan-Meier analysis and Cox regression analysis. The biological effects of UbcH10 on the cell proliferation, cell cycle, and chemosensitivity to gemcitabine or paclitaxel in SK-MES-1 cells were examined upon the UbcH10 silencing. UbcH10 is overexpressed in poorly differentiated NSCLC samples than in well-differentiated ones, and its expression level was significantly higher in squamous cell carcinoma than that in adenocarcinoma. Higher UbcH10 expression was associated with a shorter postoperative survival time of NSCLC patients by Kaplan-Meier method and was found to be an independent risk factor that influences the postoperative survival time of NSCLC patients by Cox regression analysis. UbcH10 mRNA and protein expression were significantly upregulated in SK-MES-1 cells compared with A549 and MRC-5 cells. Suppression of UbcH10 expression in SK-MES-1 cells inhibited cell proliferation and increased chemosensitivity to gemcitabine or paclitaxel concomitant with decreased MDR1 gene expression. UbcH10 may play an important role in NSCLC carcinogenesis, and silencing UbcH10 may represent a potential therapeutic strategy for NSCLC.

Abstract A46: Tumor P-glycoprotein Correlates with Efficacy of PF-03758309 Against In Vitro and In Vivo models of Colorectal Cancer

Abstract Background: P-glycoprotein (Pgp), a member of the ATP-binding cassette (ABC) transporter family, is overexpressed in a number of cancers and some studies show that Pgp overexpression can be correlated to poor prognosis or therapeutic resistance. We aimed to elucidate if the efficacy of PF-03758309, a novel p-21 activated kinase inhibitor, could be predicted based on tumor Pgp/MDR1 expression. Methods: Based on in vitro proliferation data, a panel of cell lines were ranked as sensitive (IC50<15nM) or resistant (IC50> 1μM) and MDR1 (Pgp) gene array data evaluated for the cell lines. Pgp expression was determined by western blot. We then evaluated if Pgp inhibition would restore PF-03758309 activity in vitro. PF-03758309 activity was evaluated in vivo in murine cell line xenograft models and in primary patient derived explants (PDX). Mice were implanted with either tumor cell lines or a fragment of patient tumor tissue and when tumors reached 200–300 mm3, mice were treated with 25 mg/kg PF-03758309 orally, twice daily. On the last day of treatment, tumor and plasma were collected for PF-03758309 analysis. Gene array data and tumor and plasma concentrations were evaluated. Results: MDR1 gene expression correlated (spearman, p<0.01) with resistance to PF-03758309 treatment in vitro and the expression of Pgp on resistant cells was verified by western blotting. Furthermore, the inhibition of Pgp increased the sensitivity of “resistant” cells, bringing IC50s down to ∼2–200 nM. Eleven cell line xenografts were treated and the MDR1 gene expression was found to correlate (spearman, p = 0.02) with resistance measured by an increased %T/C (treated volume/control volume × 100%). Thirteen PDX models were treated and only two were found to be “sensitive” (%T/C < 50%). Gene array analysis has not yet been performed on PDX treated specimens and baseline specimen data cannot be used because of drift in MDR1 and ABCG2 expression found in these models at different passages. Preliminary tumor and plasma concentration data has been gathered for 2 sensitive and 3 resistant models (1 PDX sensitive, 1 cell line xenograft sensitive, 2 PDX resistant, 1 cell line xenograft resistant). Tumors that responded to treatment generally exhibited a higher tumor concentration level and a higher tumor:plasa ratio (p=0.07, p=0.04). Finally, a preliminary in vivo study demonstrated that inhibition of Pgp prior to administration of PF-03758309 increased the mean tumor:plasma ratio of PF-03758309. Conclusions: Numerous agents, approved and in development, are substrates for transporters, and it may not be clear yet the role that drug resistance transporters play in resistance to these therapies. In vitro and in vivo data strongly suggests that PF-03758309 efficacy may be influenced by the expression of the tumor multidrug resistance (MDR) protein, Pgp. Pgp mediated resistance has been studied for decades and efforts have been made at sensitizing tumors to compounds that are Pgp substrates by co-administration of Pgp inhibitors, to no avail. A possible alternative to Pgp reversal is simply using patient Pgp status as a negative selective parameter for therapy.

Hyperglycemia of tumor microenvironment modulates stage‐dependent tumor progression and multidrug resistance: implication of cell survival regulatory molecules and altered glucose transport

Using a murine tumor model, we demonstrate that tumor cells display a tumor stage-dependent differential glucose utilization associated with an altered GLUT-1 expression. Hyperglycemic tumor microenvironment modulates the tumorigenic ability, survival, apoptosis, and glucose utilization of tumor cells in late tumor-bearing stage accompanied by an altered tumor acidosis and expression of cell survival regulatory molecules: HIF-1α, p53, Bcl2, caspase-activated DNase, IL-4, IL-6, IL-10, IFN-γ, TGF-β, and VEGF. Glucose-exposed tumor cells of late tumor-bearing stage also show a declined susceptibility to the cytotoxic action of chemotherapeutic drugs: cisplatin and methotrexate, accompanied by an increased expression of MDR-1 gene. Taken together the results show that hyperglycemic tumor microenvironment differentially alters tumor growth depending on the stage of tumor progression.

Abstract 4228: Aryl hydrocarbon receptor nuclear translocator is associated with cisplatin resistance in cancer cells

Abstract The (ARNT) belongs to the basic-helix-loop-helix (bHLH) transcription factors containing Per-Arnt-Sim (PAS) domain. In addition to forming heterodimers with many other bHLH-PAS proteins, including the aryl hydrocarbon receptor (AhR) and hypoxia-inducible factor 1α, ARNT can also form homodimers. Our previous study had shown that ARNT is a new factor involved in EGF regulated COX-2 gene expression under normoxia involving tumorigenesis in cervical cancer tissues. Resistence to cisplatin is often observed in cervical cancer therapy. Here we showed that ARNT expression is critical for cisplatin resistance. Specifically, we showed that in HeLa cervical cancer lines, cisplatin decreased ARNT expression level. Over-expression of ARNT rendered HeLa cells resistant to cisplatin. In addition, inhibition of ARNT by small interfering RNA silencing increased cisplatin induced cell death by activation of caspase 3 and sensitized drug resistant cells to cisplatin. Using ARNT deficient and ARNT fully expressed cell lines showed that induction of apoptosis by cisplatin correlates with ARNT. Importantly down regulation of ARNT decreased drug efflux pump protein MDR1 expression, suggesting that MDR1 gene expression depends on ARNT activity. In conclusion, ARNT mediates the efflux of cisplatin and has a functional role in cervical cancer cell sensitivity to cisplatin. In a xenograft analysis of SCID mice, cisplatin also efficiently inhibited ARNT-deficient tumor formation. These results suggest that targeting ARNT could overcome cisplatin resistance in human cervical cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4228. doi:1538-7445.AM2012-4228

Diallyl sulfide, diallyl disulfide and diallyl trisulfide affect drug resistant gene expression in colo 205 human colon cancer cells in vitro and in vivo

To elevate chemo-resistance of human cancer cells is a major obstacle in the treatment and management of malignant cancers. Diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS) are presented in the Alliaceae family particularly in garlic. Although DAS, DADS and DATS have been shown to exhibit anticancer activities, there is little information on effects of these compounds on drug resistant genes in human colon cancer cells in vitro and in vivo. Herein, we are the first to show that DAS, DADS and DATS at 25μM for 24-h and 48-h incubations promoted expression of drug resistant genes in colo 205 human colon cancer cells. In vitro experiments indicated that DATS promoted gene expression of multidrug resistant 1 (Mdr1) (p<0.05), and DAS and DADS promoted MRP3 gene expression and DATS alone stimulated gene expression of multidrug resistance-associated protein-1 (MRP1) (p<0.05) in colo 205 cells. In vivo studies demonstrated that DADS and DATS induced Mdr1 and MRP1 gene expression (p<0.05). DADS promoted MRP3 gene expression (p<0.05) as well as DADS and DATS increased MRP4 and MRP6 gene expression (p<0.05) in the colo 205 xenograft mice. Based on our in vitro and in vivo results, diallyl polysulfides (DAS, DADS and DATS) affected the gene expression of the multidrug resistance in colo 205 human colon cancer cells in vitro and in vivo.