Expression of the multidrug resistance-associated protein (MRP) gene in non-small-cell lung cancer

Meta-analysis of P53 expression and sensitivity to platinum-based chemotherapy in patients with non-small cell lung cancer

BACKGROUND

The relationship between p53 expression and chemosensitivity of non-small cell lung cancer (NSCLC) is unclear. This study aims to explore the correlation between p53 expression and sensitivity to platinum-based chemotherapy in patients with NSCLC.

METHODS

Pubmed, Web of Science, EMBASE, CNKI, China Wanfang databases were searched for studies on the relationship between the p53 expression and the chemosensitivity to platinum drugs in patients with NSCLC. The last search time was May 2020. Stata 15.0 software was used for statistical analysis.

RESULTS

A total of 21 studies were included, covering 1387 patients in total. The results showed that the pooled OR = 1.55 (95%CI: 1.05∼2.29, P < .05), for Asian population, the pooled OR = 1.67 (95%CI: 0.95∼3.09, P > .05), for Caucasian population, the pooled OR = 1.34 (95%CI: 0.74∼2.43), there was no significant difference between Asian and Caucasian. The results of subgroup analysis of publication year showed that, the pooled OR = 2.07 (95%CI: 1.39∼3.07, P < .01), the heterogeneity among the studies decreased remarkably after 2005. The subgroup analysis of advanced patients showed that the pooled OR = 1.93 (95%CI: 1.27∼2.93), the difference was statistically significant.

CONCLUSION

Patients with p53 negative expression is more sensitive to platinum-based chemotherapy than those with p53 positive expression in NSCLC, especially in advanced NSCLC.

Lactate-induced MRP1 expression contributes to metabolism-based etoposide resistance in non-small cell lung cancer cells

BACKGROUND

Metabolic reprogramming contributes significantly to tumor development and is tightly linked to drug resistance. The chemotherapeutic agent etoposide (VP-16) has been used clinically in the treatment of lung cancer but possess different sensitivity and efficacy towards SCLC and NSCLC. Here, we assessed the impact of etoposide on glycolytic metabolism in SCLC and NSCLC cell lines and investigated the role of metabolic rewiring in mediating etoposide resistance.

METHODS

glycolytic differences of drug-treated cancer cells were determined by extracellular acidification rate (ECAR), glucose consumption, lactate production and western blot. DNA damage was evaluated by the comet assay and western blot. Chemoresistant cancer cells were analyzed by viability, apoptosis and western blot. Chromatin immunoprecipitation (ChIP) was used for analysis of DNA-protein interaction.

RESULTS

Here we showed that exposure to chemotherapeutic drug etoposide induces an exacerbation of ROS production which activates HIF-1α-mediated the metabolic reprogramming toward increased glycolysis and lactate production in non-small cell lung cancer (NSCLC). We identified lactic acidosis as the key that confers multidrug resistance through upregulation of multidrug resistance-associated protein 1 (MRP1, encoded by ABCC1), a member of ATP-binding cassette (ABC) transporter family. Mechanistically, lactic acid coordinates TGF-β1/Snail and TAZ/AP-1 pathway to induce formation of Snail/TAZ/AP-1 complex at the MRP1/ABCC1 promoter. Induction of MRP1 expression inhibits genotoxic and apoptotic effects of chemotherapeutic drugs by increasing drug efflux. Furthermore, titration of lactic acid with NaHCO₃ was sufficient to overcome resistance.

CONCLUSIONS

The chemotherapeutic drug etoposide induces the shift toward aerobic glycolysis in the NSCLC rather than SCLC cell lines. The increased lactic acid in extracellular environment plays important role in etoposide resistance through upregulation of MRP expression. These data provide first evidence for the increased lactate production, upon drug treatment, contributes to adaptive resistance in NSCLC and reveal potential vulnerabilities of lactate metabolism and/or pathway suitable for therapeutic targeting. Video Abstract The chemotherapeutic drug etoposide induces metabolic reprogramming towards glycolysis in the NSCLC cells. The secreted lactic acid coordinates TGF-β1/Snail and TAZ/AP-1 pathway to activate the expression of MRP1/ABCC1 protein, thus contributing to chemoresistance in NSCLC.

Low dose HSP90 inhibition with AUY922 blunts rapid evolution of metastatic and drug resistant phenotypes induced by TGF-β and paclitaxel in A549 cells

OBJECTIVES

Despite advances in cancer treatment, drug resistance and metastasis continue to contribute to treatment failure. Since drug resistance and metastasis in cancer are features that often occur toward the late stages in the disease after withstanding numerous selective pressures, they may rely on a shared adaptive mechanism in order to persist. The heat shock response is one of the most well conserved adaptive responses to cellular stress found in nature. A major player in the heat shock response is HSP90, with some studies suggesting that it can facilitate the molecular evolution of drug resistance and metastasis in cancer. Non-small cell lung cancers (NSCLCs) are strongly associated with drug resistance and metastasis either at the time of diagnosis or early in the treatment process.

MATERIALS AND METHODS

We explored the role of HSP90 in the evolution of metastatic and drug resistant features in NSCLC by treating A549 cells with AUY922, a clinically relevant HSP90 inhibitor, and inducing metastatic and drug resistant phenotypes via treatment with TGF-β and paclitaxel, respectively. We measured phenotypic plasticity in E-Cadherin, a marker for epithelial to mesenchymal transition and two ABC transporters associated with drug resistant lung cancers.

RESULTS

We found that metastatic and efflux dependent drug resistant features negatively correlated with AUY922 treatment. We followed our results with functional assays relevant to metastasis and ABC transporters to confirm our results. Specifically we found the expression of E-cadherin was significantly increased in A549 cultures pretreated with AUY922 prior to exposure to paclitaxel, while expression of the drug transporters ABCB1 and ABCC1 was significantly reduced under similar conditions.

CONCLUSION

Together our data indicates that HSP90 inhibition with AUY922 can limit the acquisition of metastatic and drug resistant phenotypes in A549 cells at low, clinically appropriate doses.

FNDC5 promotes paclitaxel sensitivity of non-small cell lung cancers via inhibiting MDR1

Therapeutic benefits and clinical application of paclitaxel for treating non-small cell lung cancers (NSCLCs) are extremely hampered due to the chemoresistance. A recent study found that fibronectin type III domain-containing protein 5 (FNDC5) was downregulated in NSCLCs cells and negatively correlated with the clinicopathological characteristics in patients with NSCLCs. However, the role and potential molecular basis for FNDC5 in paclitaxel sensitivity of NSCLCs remain unclear. Paclitaxel-sensitive or resistant NSCLCs cell lines were exposed to small interfering RNA against FNDC5 (siFndc5) or recombinant irisin in the presence or absence of paclitaxel. NSCLCs cell lines have decreased FNDC5 expression compared with the normal human lung epithelial cells, which was further downregulated in paclitaxel-resistant cells. Irisin treatment suppressed, whereas Fndc5 silence promoted NSCLCs cells proliferation under basal conditions. Besides, we found that FNDC5 increased paclitaxel chemosensitivity in paclitaxel-sensitive or resistant NSCLCs cell lines via downregulating multidrug resistance protein 1 (MDR1). Further studies revealed that FNDC5 inhibited MDR1 expression via blocking nuclear factor-κB (NF-κB) activation. FNDC5 promotes paclitaxel sensitivity of NSCLCs cells via inhibiting NF-κB/MDR1 signaling, and FNDC5 might be a novel therapeutic target for the treatment of NSCLCs.

GLUL Ablation Can Confer Drug Resistance to Cancer Cells via a Malate-Aspartate Shuttle-Mediated Mechanism

Glutamate-ammonia ligase (GLUL) is important for acid-base homeostasis, ammonia detoxification, cell signaling, and proliferation. Here, we reported that GLUL ablation conferred resistance to several anticancer drugs in specific cancer cell lines while leaving other cell lines non-resistant to the same drugs. To understand the biochemical mechanics supporting this drug resistance, we compared drug-resistant GLUL knockout (KO) A549 non-small-cell lung carcinoma (NSCLC) cells with non-resistant GLUL KO H1299 NSCLC cells and found that the resistant A549 cells, to a larger extent, depended on exogenous glucose for proliferation. As GLUL activity is linked to the tricarboxylic acid (TCA) cycle via reversed glutaminolysis, we probed carbon flux through both glycolysis and TCA pathways by means of ¹³C5 glutamine, ¹³C5 glutamate, and ¹³C6 glucose tracing. We observed increased labeling of malate and aspartate in A549 GLUL KO cells, whereas the non-resistant GLUL KO H1299 cells displayed decreased ¹³C-labeling. The malate and aspartate shuttle supported cellular NADH production and was associated with cellular metabolic fitness. Inhibition of the malate-aspartate shuttle with aminooxyacetic acid significantly impacted upon cell viability with an IC₅₀ of 11.5 μM in resistant GLUL KO A549 cells compared to 28 μM in control A549 cells, linking resistance to the malate-aspartate shuttle. Additionally, rescuing GLUL expression in A549 KO cells increased drug sensitivity. We proposed a novel metabolic mechanism in cancer drug resistance where the increased capacity of the malate-aspartate shuttle increased metabolic fitness, thereby facilitating cancer cells to escape drug pressure.

Prognostic role of multidrug resistance-associated protein 1 expression and platelet count in operable non-small cell lung cancer

The overall survival rate of patients with non-small cell lung cancer (NSCLC) following resection remains poor due to the high rates of recurrence and metastasis. The investigation of novel biomarkers is clinically necessary to improve treatment strategies. Multidrug resistance-associated protein 1 (MRP1) and platelet count are linked to a poor prognosis in various types of cancer. However, it is unknown whether MRP1 or platelet count is a suitable prognostic indicator of NSCLC. In the present study, 427 patients with operable NSCLC were enlisted. The association of MRP1 expression and platelet count with clinical pathological factors and patient outcome was evaluated. MRP1 expression was found to be significantly associated with sex, histological type and tumor differentiation, while platelet count was significantly associated with smoking behavior, histological type and clinical stage. Platelet count was significantly higher in patients with negative MRP1 expression than in those with positive MRP1 expression. Survival analysis indicated that there was no association between MRP1 expression and disease-free survival (DFS) or overall survival (OS) time. In the patients with no lymph node metastasis, the OS time was significantly longer in patients with positive MRP1 expression than in those with negative expression. However, in the patients with lymph node metastasis, the DFS time was significantly shorter in patients with positive MRP1 expression than in those with negative expression. There was an association between the platelet count and DFS and OS times, which were significantly longer in patients with a normal platelet count than in those with thrombocytosis. In conclusion, MRP1 expression and platelet count are valuable independent prognostic biomarkers for survival in operable NSCLC.

Inducing cell death in vitro in cancer cells by targeted delivery of cytochrome c via a transferrin conjugate

One of the major drawbacks of many of the currently used cancer drugs are off-target effects. Targeted delivery is one method to minimize such unwanted and detrimental events. To actively target lung cancer cells, we have developed a conjugate of the apoptosis inducing protein cytochrome c with transferrin because the transferrin receptor is overexpressed by many rapidly dividing cancer cells. Cytochrome c and transferrin were cross-linked with a redox sensitive disulfide bond for the intra-cellular release of the protein upon endocytosis by the transferrin receptor. Confocal results demonstrated the cellular uptake of the cytochrome c-transferrin conjugate by transferrin receptor overexpressing A549 lung cancer cells. Localization studies further validated that this conjugate escaped the endosome. Additionally, an in vitro assay showed that the conjugate could induce apoptosis by activating caspase-3. The neo-conjugate not only maintained an IC50 value similar to the well known drug cisplatin (50 μM) in A549 cancer cells but also was nontoxic to the normal lung (MRC5) cells. Our neo-conjugate holds promise for future development to target cancers with enhanced transferrin receptor expression.

Multidrug resistance transporter profile reveals MDR3 as a marker for stratification of blastemal Wilms tumour patients

Wilms tumour (WT) is the most common renal tumour in children. Most WT patients respond to chemotherapy, but subsets of tumours develop resistance to chemotherapeutic agents, which is a major obstacle in their successful treatment. Multidrug resistance transporters play a crucial role in the development of resistance in cancer due to the efflux of anticancer agents out of cells. The aim of this study was to explore several human multidrug resistance transporters in 46 WT and 40 non-neoplastic control tissues (normal kidney) from patients selected after chemotherapy treatment SIOP 93–01, SIOP 2001. Our data showed that the majority of the studied multidrug resistance transporters were downregulated or unchanged between tumours and control tissues. However, BCRP1, MDR3 and MRP1 were upregulated in tumours versus control tissues. MDR3 and MRP1 overexpression correlated with high-risk tumours (SIOP classification) (p = 0.0022 and p < 0.0001, respectively) and the time of disease-free survival was significantly shorter in patients with high transcript levels of MDR3 (p = 0.0359). MDR3 and MRP1 play a role in drug resistance in WT treatment, probably by alteration of an unspecific drug excretion system. Besides, within the blastemal subtype, we observed patients with low MDR3 expression were significantly associated with a better outcome than patients with high MDR3 expression. We could define two types of blastemal WT associated with different disease outcomes, enabling the stratification of blastemal WT patients based on the expression levels of the multidrug resistance transporter MDR3.

Chemotherapy Resistance in Lung Cancer

Despite a growing interest in development of non-cytotoxic targeted agents, systemic chemotherapy is still the mainstay of treatment for both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). However, chemotherapy resistance limits our ability to effectively treat advanced lung cancer. Some lung tumors are intrinsically resistant to chemotherapy, and in virtually all cases, even the initial responders rapidly develop acquired resistance. While targeting histology could result in enhanced tumor sensitivity to a particular chemotherapeutic agent, better understanding of molecular determinants of chemotherapy sensitivity/resistance would be critically important. Development of predictive biomarkers to personalize chemotherapeutic agents and combining novel agents targeting specific resistance pathways with standard chemotherapy could be some promising strategies to overcome chemotherapy resistance in lung cancer. In this chapter, we will discuss some key mechanisms of resistance for commonly used chemotherapeutic agents in lung cancer.

MRP1 expression in bronchoalveolar lavage cells in subjects with lung cancer who were chronically exposed to arsenic

Alteration of multidrug resistance-associated protein-1 (MRP1) expression has been associated with certain lung diseases, and this protein may be pivotal in protecting the lungs against endogenous or exogenous toxic compounds. The aim of this study was to evaluate and compare the expression of MRP1 in bronchoalveolar cells from subjects with and without lung cancer who had been chronically exposed to arsenic through drinking water. MRP1 expression was assessed in bronchoalveolar cells in a total of 102 participants. MRP1 expression was significantly decreased in those with arsenic urinary levels >50 μg/L when compared with the controls. In conclusion, chronic arsenic exposure negatively correlates with the expression of MRP1 in BAL cells in patients with lung cancer.

MRP1 and its role in anticancer drug resistance

The phenomenon of multidrug resistance (MDR) in cancer is associated with the overexpression of the ATP-binding cassette (ABC) transporter proteins, including multidrug resistance-associated protein 1 (MRP1) and P-glycoprotein. MRP1 plays an active role in protecting cells by its ability to efflux a vast array of drugs to sub-lethal levels. There has been much effort in elucidating the mechanisms of action, structure and substrates and substrate binding sites of MRP1 in the last decade. In this review, we detail our current understanding of MRP1, its clinical relevance and highlight the current environment in the search for MRP1 inhibitors. We also look at the capacity for the rapid intercellular transfer of MRP1 phenotype from spontaneously shed membrane vesicles known as microparticles and discuss the clinical and therapeutic significance of this in the context of cancer MDR.

Multidrug resistance and cancer stem cells in neuroblastoma and hepatoblastoma

Chemotherapy is one of the major modalities in treating cancers. However, its effectiveness is limited by the acquisition of multidrug resistance (MDR). Several mechanisms could explain the up-regulation of MDR genes/proteins in cancer after chemotherapy. It is known that cancer stem cells (CSCs) play a role as master regulators. Therefore, understanding the mechanisms that regulate some traits of CSCs may help design efficient strategies to overcome chemoresistance. Different CSC phenotypes have been identified, including those found in some pediatric malignancies. As solid tumors in children significantly differ from those observed in adults, this review aims at providing an overview of the mechanistic relationship between MDR and CSCs in common solid tumors, and, in particular, focuses on clinical as well as experimental evidence of the relations between CSCs and MDR in neuroblastoma and hepatoblastoma. Finally, some novel approaches, such as concomitant targeting of multiple key transcription factors governing the stemness of CSCs, as well as nanoparticle-based approaches will also be briefly addressed.

MRP1 overexpression determines poor prognosis in prospectively treated patients with localized high-risk soft tissue sarcoma of limbs and trunk wall: an ISG/GEIS study

Patients with localized high-risk soft tissue sarcomas (STS) of the limbs and trunk wall still have a considerable metastatic recurrence rate of more than 50%, in spite of adjuvant chemotherapy. This drug-ceiling effect of chemotherapy in sarcoma setting could be explained, at least partially, by multidrug resistance (MDR) mechanisms. The aim of this study was to ascertain whether mRNA and protein expression of ABCB1 (P-glycoprotein), ABCC1 (MRP1), and GSTA1 (glutathione S-transferase pi) was prognostic in localized high-risk STS. Immunohistochemistry and reverse transcriptase-PCR studies were performed from biopsies at the time of diagnosis. Patients of this series were prospectively enrolled into a phase III trial that compared three versus five cycles of epirubicin plus ifosfamide. The series of 102 patients found 41 events of recurrence and 37 of death with a median follow-up of 68 months. In univariate analysis, variables with a statistically significant relationship with relapse-free survival (RFS) were: MRP1 expression (5-year RFS rate of 23% in positive cases and 63% in negative cases, P = 0.029), histology (5-year RFS rate of 74% in undifferentiated pleomorphic sarcoma and 43% in synovial sarcoma, P = 0.028), and ABCC1 expression (5-year RFS rate of 33% in overexpression and 65% in downregulation, P = 0.012). Combined ABCC1/MRP1 was the only independent prognostic factor for both RFS (HR = 2.704, P = 0.005) and overall survival (HR = 2.208, P = 0.029). ABCC1/MRP1 expression shows robust prognostic relevance in patients with localized high-risk STS treated with anthracycline-based chemotherapy, which is the standard front line treatment in STS. This finding deserves attention as it points to a new targetable protein in STS.

Positive expression of p53, c-erbB2 and MRP proteins is correlated with survival rates of NSCLC patients

The incidence of lung cancer is one of the leading causes of mortality. This study aimed to investigate the prognostic and predictive importance of p53, c-erbB2 and multidrug resistance proteins (MRP) expression and its correlation with clinicopathological characteristics of patients with non-small cell lung cancer (NSCLC). Expression of p53, c-erbB2 and MRP proteins in 152 tumor samples from resected primary NSCLCs was detected by immunohistochemical staining. The correlation of proteins, survival and clinicopathological characteristics was investigated in 152 patients undergoing potentially curative surgery. The positive rates of p53, c-erbB2 and MRP expression were 53.9 (82/152), 44.1 (67/152) and 43.4% (66/152), respectively. Overall survival rates of patients were markedly correlated with the overexpression of p53, c-erbB2 and MRP proteins. One, 2- and 3-year survival rates of patients exhibiting a positive expression of these proteins were 72.6, 54.8 and 32.2%, respectively. These rates were lower compared with those of patients with a negative expression of these proteins (92.1, 78.5 and 63.4%) (P=0.02, 0.01 or 0.00, respectively). Results of Cox's regression analysis showed that c-erbB2 expression and cell differentiation were independent prognostic factors in patients with NSCLC. These findings suggest that the positive expression of p53, c-erbB2 and MRP proteins is correlated with the survival rates of NSCLC patients. Detection of positive p53, c-erbB2 and MRP expression may be a useful predictive indicator of prognosis. Positive c-erbB2 expression is an independent prognostic factor, with a potential to be used as a predictive indicator of chemotherapy efficacy in NSCLC patients.

Drug Resistance Mechanisms in Non-Small Cell Lung Carcinoma

Lung cancer is the most commonly diagnosed cancer in the world. “Driver” and “passenger” mutations identified in lung cancer indicate that genetics play a major role in the development of the disease, progression, metastasis and response to therapy. Survival rates for lung cancer treatment have remained stagnant at ~15% over the past 40 years in patients with disseminated disease despite advances in surgical techniques, radiotherapy and chemotherapy. Resistance to therapy; either intrinsic or acquired has been a major hindrance to treatment leading to great interest in studies seeking to understand and overcome resistance. Genetic information gained from molecular analyses has been critical in identifying druggable targets and tumor profiles that may be predictors of therapeutic response and mediators of resistance. Mutated or overexpressed epidermal growth factor receptor (EGFR) and translocations in the echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) genes (EML4-ALK) are examples of genetic aberrations resulting in targeted therapies for both localized and metastatic disease. Positive clinical responses have been noted in patients harboring these genetic mutations when treated with targeted therapies compared to patients lacking these mutations. Resistance is nonetheless a major factor contributing to the failure of targeted agents and standard cytotoxic agents. In this review, we examine molecular mechanisms that are potential drivers of resistance in non-small cell lung carcinoma, the most frequently diagnosed form of lung cancer. The mechanisms addressed include resistance to molecular targeted therapies as well as conventional chemotherapeutics through the activity of multidrug resistance proteins.

Xenobiotic metabolism and disposition in human lung cell models: comparison with in vivo expression profiles

Numerous lung cell lines are currently used as in vitro models for pharmacological and toxicological studies. However, no exhaustive report about the metabolic capacities of these models in comparison with those of lung tissues is available. In the present study, we used a high-throughput quantitative real-time reverse transcription-polymerase chain reaction strategy to characterize the expression profiles of 380 genes encoding proteins involved in the metabolism and disposition of xenobiotics in 10 commonly used lung cell lines (A549, H292, H358, H460, H727, Calu-1, 16HBE, 1 HAEO, BEAS-2B, and L-132) and four primary cultures of human bronchial epithelial cells. Expression results were then compared with those previously obtained in human nontumoral and tumoral lung tissues. Our results revealed disparities in gene expression between lung cell lines or when comparing lung cell lines with primary cells or lung tissues. Primary cell cultures displayed the highest similarities with bronchial mucosa in terms of transcript profiling and therefore seem to be the most relevant in vitro model for investigating the metabolism and bioactivation of toxicants and drugs in bronchial epithelium. H292 and BEAS-2B cell lines, which exhibited the highest homology in gene expression pattern with primary cells and the lowest number of dysregulated genes compared with nontumoral lung tissues, could be used as surrogates for toxicological and pharmacological studies. Overall, our study should provide references for researchers to choose the most appropriate in vitro model for analyzing the cellular effects of drugs or airborne toxicants on the airway.

Induction of cell cycle arrest and apoptosis by ruthenium complex cis-(dichloro)tetramineruthenium(III) chloride in human lung carcinoma cells A549

Lung cancer is one of the leading causes of death in the world, and non-small cell lung carcinoma (NSCLC) accounts for approximately 75-85% of all lung cancers. In the present work, we studied the cytotoxic activity, cell cycle arrest and induction apoptosis of the compound cis-(dichloro)tetramineruthenium(III) chloride {cis-[RuCl(2)(NH(3))(4)]Cl} in human lung carcinoma tumor cell line A549. The results of MTT and trypan blue assays showed that cis-[RuCl(2)(NH(3))(4)]Cl causes reduction in the viability of A549 cells when treating with 95 and 383 μM of the compound for 48 and 72 h. Lower concentrations of the compound (19, 3.8 and 0.38 μM), however, only slightly affected cell viability. The IC(50) value for the compound was about 383 μM. Survival analysis of the A549 cells after treatment with ruthenium(III) compound using long term clonogenic assay showed that it reduced colony formation ability at concentrations of 0.38 and 3.8 μM, and at concentrations of 95 and 383 μM no colonies were observed. Cell cycle analysis showed that compound ruthenium led to an accumulation of A549 cells in S phase and increased in the sub-G1 peak. In addition, cis-(dichloro)tetramineruthenium(III) chloride treatment induced apoptosis, as observed by the increased numbers of annexin V-positive cells and increased messenger RNA expression of caspase-3.

ABCC1 polymorphism Arg723Gln (2168G> A) is associated with lung cancer susceptibility in a Chinese population

1. In a previous in vitro study, we showed that the Arg723Gln (2168G > A) polymorphism significantly ABCC1-induced multidrug resistance. The aim of the present study was to further investigate the association of this polymorphism with lung cancer susceptibility and chemotherapy response in a Chinese population. 2. A total of 77 lung cancer patients (54 men, 23 women) and 71 cancer-free controls (49 men, 22 women) were enrolled in the study. Genomic DNA was extracted from peripheral blood and all samples were genotyped using polymerase chain reaction-restriction fragment length polymorphism. 3. Individuals carrying the 723Gln (A) allele have a 3.4-fold increased risk (adjusted odds ratio (OR) 3.42; 95% confidence interval (CI) 1.29-9.06; P = 0.013) of lung cancer compared with wild-type individuals. Further stratified analysis indicated that older individuals (> 50 years) carrying the 723Gln (A) allele have the highest susceptibility to lung cancer (adjusted OR 4.10; 95% CI 1.25-13.48; P = 0.020). However, no substantial association was found between the Arg723Gln (2168G > A) polymorphism and chemotherapy response in Chinese lung cancer patients. 4. In conclusion, the Arg723Gln (2168G > A) polymorphism of ABCC1 appears to be a potential susceptibility marker for lung cancer in the Chinese population, especially in older people.

Combined use of anticancer drugs and an inhibitor of multiple drug resistance-associated protein-1 increases sensitivity and decreases survival of glioblastoma multiforme cells in vitro

Glioblastoma multiforme (GBM) is a brain tumour characterised by a remarkably high chemoresistance and infiltrating capability. To date, chemotherapy with temozolomide has contributed only poorly to improved survival rates in patients. One of the most important mechanisms of chemoresistance comes about through the activity of certain proteins from the ATP-binding cassette superfamily that extrudes antitumour drugs, or their metabolites, from cells. We identify an increased expression of the multiple drug resistance-associated protein 1 (Mrp1) in glioblastoma multiforme biopsies and in T98G and G44 cell lines. The activity of this transporter was also confirmed by measuring the extrusion of the fluorescent substrate CFDA. The sensitivity of GBM cells was low upon exposure to temozolomide, vincristine and etoposide, with decreases in cell viability of below 20% seen at therapeutic concentrations of these drugs. However, combined exposure to vincristine or etoposide with an inhibitor of Mrp1 efficiently decreased cell viability by up to 80%. We conclude that chemosensitization of cells with inhibitors of Mrp1 activity might be an efficient tool for the treatment of human GBM.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Establishment and characterization of a new drug surviving cell line Am1010, derived directly from muscle metastases of a human lung adenocarcinoma patient with multi-drug-resistance to cisplatin, taxol, and gefitinib

AIM

To Characterize a new human lung cancer cell line Am1010, derived from drug-surviving cells (DSCs).

METHODS

The Am1010 cell line was established after 4 cycles of chemotherapy from an arm muscle metastatic tumor of a patient diagnosed with lung adenocarcinoma. The cell line has been remained in continuous culture for more than one year during this study.

RESULTS

The Am1010 cell line demonstrated in vitro multi-drug-resistance to cisplatin, taxol, and gefitinib. The Am1010 cell doubling time without drug treatment was 42.395 h. The IC(50) value of cisplatin was 4.299 micromol/L and >10 micromol/L for the Am1010 and P0318 (a cell line derived from non-DSCs) cells, respectively. The IC(50) value of taxol was 0.067 micromol/L and >1 micromol/L for the Am1010 and P0318 cells, respectively. The IC(50) value of gefitinib was 15.233 micromol/L and >70 micromol/L for Am1010 and P0318 cells, respectively. 11 genes involved in the focal adhesion and cell adhesion pathways were found to be differentially expressed. The cells of Am1010 have a significantly larger chromosome number than most lung cancer cell lines.

CONCLUSION

This novel DSCs derived lung cancer cell line will be a valuable in vitro tool for the investigation of lung cancer drug resistance and metastasis.

Expression of MRP1, BCRP, LRP, and ERCC1 in advanced non-small-cell lung cancer: correlation with response to chemotherapy and survival

PURPOSE

We investigated the prognostic value of the expression of multidrug resistance protein-1 (MRP1), breast cancer resistance protein (BCRP), lung resistance-related protein (LRP), and excision repair cross-complementing group-1 (ERCC1) in patients with advanced non-small-cell lung cancer (NSCLC) treated with cisplatin-based chemotherapy.

PATIENTS AND METHODS

Semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR) was used for detecting the expression of MRP1, BCRP, LRP, and ERCC1 mRNA in 66 transbronchial biopsy (TBB) samples from untreated patients with advanced NSCLC. All of the patients received cisplatin-based chemotherapy. Response to chemotherapy, progression-free survival (PFS), and overall survival (OS) were compared in relation to expression of each gene and clinicopathologic factors.

RESULTS

Results showed that tumor stage (P = .028) and the expression of MRP1 (P = .046) and LRP (P = .012) correlated with response to chemotherapy. Poor performance status (PS; P = .016), advanced tumor stage (P = .004), and the high expression of MRP1 (P = .012) and LRP (P = .002) predicted poorer PFS. Performance status (P = .009); tumor stage (P = .003); and the expression of MRP1 (P = .017), LRP (P = .005), and ERCC1 (P = .002) were predictive for OS. In a Cox proportional hazards multivariable analysis, PS (P = .042), tumor stage (P = .007), and the expression of LRP (P = .011) and ERCC1 (P = .026) were identified as independent prognostic factors for OS.

CONCLUSION

Our data suggested that determination of MRP1, LRP, and ERCC1 mRNA expression using RT-PCR in TBB samples might be helpful in predicting outcome of patients with advanced NSCLC treated with cisplatin-based chemotherapy and in optimizing therapeutic strategy based on the expression of these genes.

Update information on drug metabolism systems--2009, part II: summary of information on the effects of diseases and environmental factors on human cytochrome P450 (CYP) enzymes and transporters

The present paper is an update of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 (CYP) enzymes and transporters. The data are presented in tabular form (Tables 1 and 2) and are a continuation of previously published summaries on the effects of drugs and other chemicals on CYP enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29(1-2), 413-580., Rendic, S. Drug Metab. Rev., 2002, 34(1-2), 83-448.). The collected information presented here is as stated by the cited author(s), and in cases when several references are cited the latest published information is included. Inconsistent results and conclusions obtained by different authors are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file, for information about file availability contact the corresponding author.

Association of expression of MRP1, BCRP, LRP and ERCC1 with outcome of patients with locally advanced non-small cell lung cancer who received neoadjuvant chemotherapy

PURPOSE

The aim of this study was to investigate prognostic value of multidrug resistance protein 1 (MRP1), breast cancer resistance protein (BCRP), lung resistance-related protein (LRP) and excision repair cross-complementing 1 (ERCC1) in patients with locally advanced non-small cell lung cancer (NSCLC) who received neoadjuvant cisplatin-based chemotherapy.

METHODS

Transbronchial biopsy (TBB) specimens from 46 patients with stage IIIA (N(2)) NSCLC were collected to determine the expression level of MRP1, BCRP, LRP and ERCC1 mRNA by semiquantitative RT-PCR. The expression level of each gene was analyzed in relation to histopathologic response to chemotherapy, and tumor-free survival (TFS) and overall survival.

RESULTS

Patients with MRP1 or LRP low expression had a significantly better histopathologic response (P=0.032 and 0.006), and a significantly longer TFS (P=0.043 and 0.025) and overall survival (P=0.019 and 0.013) than those with MRP1 or LRP high expression. Patients with ERCC1 low expression had a significantly longer overall survival (P=0.007), but not TFS (P=0.094) than those with ERCC1 high expression. In multivariate analysis, LRP low expression was a significantly favorable factor for TFS (P=0.027), and LRP and ERCC1 were significantly favorable factors for overall survival (P=0.012 and 0.032).

CONCLUSION

Assessment of MRP1 and LRP mRNA expression in TBB specimens may predict histopathologic response and survival in locally advanced NSCLC patients who received neoadjuvant cisplatin-based chemotherapy. ERCC1 expression was predictive for overall survival.

Multidrug-resistant protein-3 gene regulation by the transcription factor Nrf2 in human bronchial epithelial and non-small-cell lung carcinoma

Multidrug-resistant proteins (MRPs) are members of the ATP-binding cassette superfamily that facilitate detoxification by transporting toxic compounds, including chemotherapeutic drugs, out of cells. Chemotherapy, radiation, and other xenobiotic stresses have been shown to increase levels of select MRPs, although the underlying mechanism remains largely unknown. Additionally, MRP3 is suspected of playing a role in the drug resistance of non-small-cell lung carcinoma (NSCLC). Analysis of the MRP3 promoter revealed the presence of multiple putative electrophile-responsive elements (EpREs), sequences that suggest possible regulation of this gene by Nrf2, the key transcription factor that binds to EpRE. The goal of this investigation was to determine whether MRP3 induction was dependent upon the transcription factor Nrf2. Keap1, a key regulator of Nrf2, sequesters Nrf2 in the cytoplasm, preventing entry into the nucleus. The electrophilic lipid peroxidation product 4-hydroxy-2-nonenal (HNE) has been shown to modify Keap1, allowing Nrf2 to enter the nucleus. We found that HNE up-regulated MRP3 mRNA and protein levels in cell lines with wild-type Keap1 (the human bronchial epithelial cell line HBE1 and the NSCLC cell line H358), but not in the Keap1-mutant NSCLC cell lines (A549 and H460). Cell lines with mutant Keap1 had constitutively higher MRP3 that was not increased by HNE treatment. In HBE1 cells, silencing of Nrf2 with siRNA inhibited induction of MRP3 by HNE. Finally, we found that silencing Nrf2 also increased the toxicity of cisplatin in H358 cells. The combined results therefore support the hypothesis that MRP3 induction by HNE involves Nrf2 activation.

Modulation of Oral Drug Bioavailability: From Preclinical Mechanism to Therapeutic Application

Currently, more than one fourth of all anticancer drugs are developed as oral formulations, and it is expected that this number will increase substantially in the near future. To enable oral drug therapy, adequate oral bioavailability must be achieved. Factors that have proved to be important in limiting the oral bioavailability are the presence of ATP-binding cassette drug transporters (ABC transporters) and the cytochrome P450 enzymes. We discuss the tissues distribution and physiological function of the ABC transporters in the human body, their expression in tumors, currently known polymorphisms and drugs that are able to inhibit their function as transporter. Furthermore, the role of the ABC transporters and drug-metabolizing enzymes as mechanisms to modulate the pharmacokinetics of anticancer agents, will be reviewed. Finally, some clinical examples of oral drug modulation are discussed. Among these examples are the coadministration of paclitaxel with CsA, a CYP3A4 substrate with P-glycoprotein (P-gp) modulating activity, and topotecan combined with the BCRP/P-gp transport inhibitor elacridar. Both are good examples of improvement of oral drug bioavailability by temporary inhibition of drug transporters in the gut epithelium.

Basal cytokeratin expression in relation to biological factors in breast cancer

The objective of this study was to determine the predictive impact of several established tumor biological markers and clinicopathological findings for basal-like carcinoma. Expression was determined by immunohistochemistry using antibodies to cytokeratins 5/6, 14, and 17, and the cases were divided into basal-like carcinoma and non basal-like carcinoma. These subgroups were compared in terms of biological markers (HER2, estrogen receptor, progesterone receptor, Ki-67, P-53, and P-glycoprotein) and clinicopathological behavior. Of the 49 basal-like carcinoma cases, 25(51.0%) were P-53-positive, whereas 100 (35.9%) of the 278 non basal-like carcinoma cases were P-53-positive. A high ratio of nuclear Ki-67 expression was detected in 39 (79.6%) of 49 basal-like carcinoma cases and was significantly more common than in non basal-like carcinoma cases (81/278, 29.1%). P-glycoprotein expression was identified in 29 (59.2%) of 49 basal-like carcinomas but only 85 (30.6%) of 278 non basal-like carcinomas. We observed high levels of P-53, Ki-67, and P-glycoprotein, with the reduction or loss of estrogen receptor, progesterone receptor, and HER2 being more obvious, in basal-like carcinomas than in non basal-like carcinomas. Our findings provide further evidence that basal-like carcinoma has different mechanisms of histogenesis.

Multidrug resistance proteins do not predict benefit of adjuvant chemotherapy in patients with completely resected non-small cell lung cancer: International Adjuvant Lung Cancer Trial Biologic Program

PURPOSE

The purpose of our study was to determine whether multidrug resistance proteins (MRP) are of prognostic and/or predictive value in patients who were enrolled into the International Adjuvant Lung Cancer Trial (IALT).

EXPERIMENTAL DESIGN

Expression of MRP1 and MRP2 was immunohistochemically assessed in tumor specimens obtained from 782 IALT patients. Prognostic and predictive analyses were based on Cox models adjusted for clinical and pathologic variables.

RESULTS

MRP1 expression was considered positive in 364 (47%) patients and MRP2 expression in 313 (40%) patients. MRP2-positive patients had a significantly shorter overall survival than MRP2-negative patients in the total patient population [adjusted hazard ratio for death, 1.37; 95% confidence interval (95% CI), 1.09-1.72; P = 0.007]. There was no significant association between MRP1 expression and overall survival. Neither MRP1 nor MRP2 predicted response to adjuvant cisplatin-based chemotherapy.

CONCLUSIONS

MRP2 expression is an independent prognostic factor in patients with completely resected non-small cell lung cancer but neither MRP1 nor MRP2 was of predictive value in patients enrolled into the IALT.

Multidrug resistance mediated by ABC transporters in osteosarcoma cell lines: mRNA analysis and functional radiotracer studies

Drug resistance remains a significant impediment to successful chemotherapy and constitutes a major prognostic factor in osteosarcoma (OS) patients. This study was designed to identify the role and prognostic significance of multidrug-resistance (MDR)-related transporters, such as multidrug resistance protein 1 (MDR1), multidrug-resistance-associated protein (MRP1) and breast-cancer-related protein (BCRP), in OS using cationic lipophilic radiotracers. We evaluated the chemosensitivity of four OS cell lines (Saos-2, 143B, MNNG/HOS and U-2OS) to doxorubicin (DOX), cisplatin (CIS) and methotrexate. The expression of MDR-related transporters was analyzed at mRNA level by quantitative polymerase chain reaction and at functional level by 99mTc sestamibi and 99mTc tetrofosmin. The effectiveness of MDR modulators [cyclosporin A (CsA) and imatinib] on transporter inhibition and on the reversal of resistance was also assessed. MNNG/HOS and U-2OS cells expressing high levels of MDR1 were highly resistant to DOX and showed reduced accumulation and higher efflux for radiotracers. Although MRP1 was uniformly expressed in all cells, only U-2OS was resistant to CIS. CsA restored sensitivity to DOX and CIS, and enhanced the accumulation and efflux half-life of radiotracers in MDR1-expressing cell lines. The chemosensitivity of OS cells to DOX was strongly dependent on mRNA MDR1 expression and could be circumvented by adding CsA. The kinetic parameters of radiotracers correlated with MDR1 expression levels, hence predicting DOX resistance. We concluded that sensitivity to chemotherapy is strongly dependent on the expression of MDR1 transporter and that radiotracer studies could prove clinically useful in predicting chemotherapy response and in evaluating the efficacy of MDR-reversing agents.

Transmembrane transport of endo- and xenobiotics by mammalian ATP-binding cassette multidrug resistance proteins

Multidrug Resistance Proteins (MRPs), together with the cystic fibrosis conductance regulator (CFTR/ABCC7) and the sulfonylurea receptors (SUR1/ABCC8 and SUR2/ABCC9) comprise the 13 members of the human "C" branch of the ATP binding cassette (ABC) superfamily. All C branch proteins share conserved structural features in their nucleotide binding domains (NBDs) that distinguish them from other ABC proteins. The MRPs can be further divided into two subfamilies "long" (MRP1, -2, -3, -6, and -7) and "short" (MRP4, -5, -8, -9, and -10). The short MRPs have a typical ABC transporter structure with two polytropic membrane spanning domains (MSDs) and two NBDs, while the long MRPs have an additional NH2-terminal MSD. In vitro, the MRPs can collectively confer resistance to natural product drugs and their conjugated metabolites, platinum compounds, folate antimetabolites, nucleoside and nucleotide analogs, arsenical and antimonial oxyanions, peptide-based agents, and, under certain circumstances, alkylating agents. The MRPs are also primary active transporters of other structurally diverse compounds, including glutathione, glucuronide, and sulfate conjugates of a large number of xeno- and endobiotics. In vivo, several MRPs are major contributors to the distribution and elimination of a wide range of both anticancer and non-anticancer drugs and metabolites. In this review, we describe what is known of the structure of the MRPs and the mechanisms by which they recognize and transport their diverse substrates. We also summarize knowledge of their possible physiological functions and evidence that they may be involved in the clinical drug resistance of various forms of cancer.

Flavonoid-drug interactions: effects of flavonoids on ABC transporters

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and a high intake of flavonoids has been associated with a reduced risk of cancer, cardiovascular diseases, osteoporosis and other age-related degenerative diseases. Due to an increased public interest in alternative medicine and disease prevention, the use of herbal preparations containing high doses of flavonoids for health maintenance has become very popular, raising the potential for interactions with conventional drug therapies. This review will summarize the current literature regarding the interactions of flavonoids with ATP-binding cassette (ABC) efflux transporters, mainly P-glycoprotein, MRP1, MRP2 and BCRP and discuss the potential consequences for flavonoid-drug transport interactions.

Doxorubicin induces expression of multidrug resistance-associated protein 1 in human small cell lung cancer cell lines by the c-jun N-terminal kinase pathway

Multidrug resistance (MDR) is a major impediment to successful chemotherapy for lung cancer. Overexpression of multidrug resistance-associated protein 1 (MRP1) appears to be involved in MDR development in lung cancer cells. A number of chemotherapeutic agents including doxorubicin (DOX) were reported to induce MRP1 expression in human lung cancer cells. In our study, we investigated the mechanism by which DOX induces MRP1 expression in human small cell lung cancer (SCLC) cell lines, GLC4 and NCI-H82. These cells expressed MRP1 protein at low levels and were sensitive to DOX. Doxorubicin at 50 nM induced a marked increase in MRP1 expression in 24 hr, and stimulated c-jun N-terminal kinase (JNK) activity. Treatment with a JNK inhibitor, SP600125, significantly inhibited MRP1 induction. Furthermore, transfection with JNK1 and JNK2 antisense oligonucleotides markedly inhibited DOX-induced MRP1 expression. Chromatin immunoprecipitation assays revealed an enhanced recruitment of phosphorylated c-jun to the MRP1 promoter containing the AP-1 site upon DOX stimulation, which was inhibited by pretreatment with SP600125. Surprisingly, GLC4 cells exposed to DOX for 24 hr maintained increased MRP1 expression and resistance to DOX for at least 3 weeks. Pretreatment with SP600125 before DOX stimulation blocked the appearance of the MDR phenotype as well as MRP1 induction in GLC4 cells. These findings suggest that JNK activation may play an essential role for the induction of MRP1 protein in human SCLC cells by chemotherapeutic agents and that combined treatment of a JNK inhibitor with anticancer drugs may prevent the development of MDR by the abrogation of MRP1 induction.

Multidrug resistance markers P-glycoprotein, multidrug resistance protein 1, and lung resistance protein in non-small cell lung cancer: prognostic implications

PURPOSE

The aim of this retrospective study was to comparatively investigate the expression of the three drug-resistance genes P-glycoprotein (P-gp), multidrug-resistance protein 1 (MRP1), and lung resistance protein (LRP), in non-small cell lung cancer (NSCLC) tissues, and to assess possible associations with clinicopathologic features.

METHODS

Tumor specimens from 126 patients were analyzed by immunohistochemistry and, in selected cases, by reverse transcriptase polymerase chain reaction (RT-PCR), and data were statistically analyzed by SPSS.

RESULTS

The mean expression levels of tumor tissues in the case of P-gp and LRP did not exceed the one of normal epithelia, while MRP1 was significantly enhanced in NSCLC. A weak association was observed between higher grading and P-glycoprotein expression (p <0.08) as well as lower grading and MRP1 expression in the case of adenocarcinoma (p <0.05). MRP1 levels were highest in TNM stage I and declined with advanced stage (p <0.03). A significant association was found between high MRP1 levels and longer overall survival (N =115, p <0.04), which was highly significant in the patient group never treated with chemotherapy (N =77; p <0.007). P-gp expression was enhanced in those patients who had received chemotherapy before surgery (p <0.05).

CONCLUSIONS

Our data point towards a major role of MRP1 in the intrinsic treatment resistance of NSCLC and suggest, in addition, a significant activation of P-gp expression during chemotherapy.

Multidrug resistance-associated protein (MRP1) is overexpressed in DNA aneuploid carcinomatous cells in non-small cell lung cancer (NSCLC)

Resistance to chemotherapy is intrinsically present in most nonsmall-cell lung carcinomas (NSCLC). No parameter has yet been determined to predict the response to chemotherapy. However, MRP1 (multidrug resistance-associated protein) is suspected to play an important role in resistance to treatment. The genetic basis for this resistance is not clearly understood, but it could result from chromosome reassortments catalyzed by aneuploidy. The aim of this study was to investigate MRP1 expression concurrently to DNA ploidy analysis in order to evaluate the link between MRP1 expression and chromosome 16 (MRP1 gene location) aberrations in NSCLC before treatment. Eighty-four surgical tumor specimens, 18 selected samples containing more than 80% of carcinomatous cells and 11 samples from normal bronchial epithelium were studied. Samples were stained by MRP1 FITC indirect staining and propidium iodide and analyzed by Flow Cytometry. Fifty tumors contained at least 1 DNA-aneuploid clone and the percentage of MRP1-positive cells was higher in DNA-aneuploid cells (p = 0.0003). All tumors expressed MRP1, but the level of expression was 3-fold higher in DNA-aneuploid cells than in DNA-diploid cells (normal bronchial cells as well as carcinomatous cells) (p < 0.0001). FISH analysis of 24 tumor imprints using a chromosome 16 alpha-satellite centromere probe demonstrated significantly more frequent gain of chromosome 16 in DNA-aneuploid tumors. These results suggest that MRP1 overexpression in NSCLC could be a consequence of chromosome 16 reassortments catalyzed by aneuploidy and that DNA-aneuploid tumors could require different treatment modalities from those applied to DNA-diploid tumors.

Alternative Splicing of theMultidrug Resistance Protein 1/ATP Binding Cassette Transporter SubfamilyGene in Ovarian Cancer Creates Functional Splice Variants and Is Associated with Increased Expression of the Splicing Factors PTB and SRp20

PURPOSE

Overexpression of multidrug resistance protein 1 (MRP1) confers resistance to a range of chemotherapeutic agents in cell lines and could be involved in clinical drug resistance of some tumor types also. We examined MRP1 expression in a small series of untreated human ovarian tumors and matched normal tissues.

EXPERIMENTAL DESIGN

We analyzed ten pairs of snap-frozen ovarian tumor and matched normal total ovarian tissues from the same patients for expression of MRP1 by reverse transcription-PCR. Amplified PCR products were sequenced to reveal splicing events of MRP1. MRP1 splice variants were expressed as enhanced green fluorescent fusion proteins in HEK293T cells to demonstrate their localization in the cell and their activity in conferring resistance to doxorubicin. The expression of splicing factors PTB and SRp20 was examined by Western blot.

RESULTS

MRP1 was expressed in all 10 of the pairs of specimens. Multiple MRP1 cDNA fragments of various sizes were amplified between exons 10 and 19. Of interest, more MRP1 cDNA fragments were detected in ovarian tumors than in matched normal tissues in 9 of 10 pairs. We identified 10 splicing forms between exons 10 and 19 of the MRP1 gene with exon skipping ranging from 1 to 7. Amplification of the entire coding region of MRP1 from 1 ovarian tumor revealed >20 splice variants. We found whole and partial exon skipping and partial intron inclusion in these splice variants. We expressed 3 of these MRP1 splice variants in HEK293T cells and found that they appeared to localize to the plasma membrane and were functional in conferring resistance to doxorubicin. In addition, we identified a few nucleotide variations in this gene. To understand the basis for increased splice variants in the tumors, we examined splicing factor expression in these tissues. Western blot analysis revealed that two splicing factors, PTB and SRp20, were overexpressed in most ovarian tumors compared with their matched normal ovarian tissues. Importantly, overexpression of both of these splicing factors was associated with the increased number of MRP1 splicing forms in the ovarian tissues.

CONCLUSION

The MRP1 gene undergoes alternative splicing at a higher frequency in ovarian tumors than in matched normal tissues. Some of these splice variants confer resistance to doxorubicin. Expression of splicing factors PTB and SRp20 is strongly associated with the alternative splicing of the MRP1 gene.

Glutathione conjugates and their synthetic derivatives as inhibitors of glutathione-dependent enzymes involved in cancer and drug resistance

Alterations in levels of glutathione (GSH) and glutathione-dependent enzymes have been implicated in cancer and multidrug resistance of tumor cells. The activity of a number of these, the multidrug resistance-associated protein 1, glutathione S-transferase, DNA-dependent protein kinase, glyoxalase I, and gamma-glutamyl transpeptidase, can be inhibited by GSH-conjugates and synthetic analogs thereof. In this review we focus on the function of these enzymes and carriers in cancer and anti-cancer drug resistance, in relation to their inhibition by GSH-conjugate analogs.

The expression of P-glycoprotein and multidrug resistance proteins 1 and 2 (MRP1 and MRP2) in human malignant mesothelioma

BACKGROUND

Malignant mesothelioma is a malignancy with a primary resistance to chemo- and radiotherapies for reasons which are still unclear. Multidrug resistance proteins might explain the observed resistance, but no studies have assessed their expression in mesothelioma.

PATIENTS AND METHODS

Immunohistochemical expression of P-glycoprotein (P-gp), and the multidrug resistance proteins 1 and 2 (MRP1 and MRP2) were investigated in 36 cases of malignant mesothelioma and in samples from normal mesothelium.

RESULTS

P-gp immunopositivity was found in 61%, MRP1 immunopositivity in 58% and MRP2 positivity in 33% of the cases. Normal mesothelium did not express these multidrug-resistant proteins. There was a significant association between P-gp and MRP2 (P = 0.022) expression. No or weak P-gp, MRP1 or MRP2 immunostaining was significantly more frequent in sarcomatoid mesothelimas than in epithelial or biphasic mesotheliomas (P = 0.031, P = 0.034 and P = 0.024, respectively). There was no significant association between patient survival and expression of the multidrug-resistant proteins.

CONCLUSIONS

The results show that P-gp, MRP1 and MRP2 are induced and expressed in malignant mesothelial cells. Regardless of their expression no association with survival of the patients was seen, suggesting that the primary resistance of malignant mesotheliomas is not solely dependent on their expression or function.

Reversal of cisplatin and multidrug resistance by ribozyme-mediated glutathione suppression

gamma-Glutamylcysteine synthetase (gamma-GCS) is a key enzyme in glutathione (GSH) synthesis, and is thought to play a significant role in intracellular detoxification, especially of anticancer drugs. Increased levels of GSH are commonly found in the drug-resistant human cancer cells. We designed a hammerhead ribozyme against gamma-GCS mRNA (anti-gamma-GCS Rz), which specifically down-regulated gamma-GCS gene expression in the HCT-8 human colon cancer cell line. The aim of this study was to reverse the cisplatin and multidrug resistance for anticancer drugs. The cisplatin-resistant HCT-8 cells (HCT-8DDP cells) overexpressed MRP and MDR1 genes, and showed resistance to not only cisplatin (CDDP), but also doxorubicin (DOX) and etoposide (VP-16). We transfected a vector expressing anti-gamma-GCS Rz into the HCT-8DDP cells (HCT-8DDP/Rz). The anti-gamma-GCS Rz significantly suppressed MRP and MDR, and altered anticancer drug resistance. The HCT-8DDP/Rz cells were more sensitive to CDDP, DOX and VP-16 by 1.8-, 4.9-, and 1.5-fold, respectively, compared to HCT-8DDP cells. The anti-gamma-GCS Rz significantly down-regulated gamma-GCS gene expression as well as MRP/MDR1 expression, and reversed resistance to CDDP, DOX and VP-16. These results suggested that gamma-GCS plays an important role in both cisplatin and multidrug resistance in human cancer cells.

Assessment of IAP (inhibitor of apoptosis) proteins as predictors of response to chemotherapy in advanced non-small-cell lung cancer patients

BACKGROUND

Expression of inhibitor of apoptosis family proteins (IAPs) has been shown in vitro to decrease chemosensitivity through caspase inhibition. However, the role of IAPs as predictors of response to chemotherapy in cancer patients remains to be determined.

PATIENTS AND METHODS

Using immunohistochemistry, we assessed the expression of the IAP proteins c-IAP1, c-IAP2, and XIAP on tumors from 55 patients with advanced non-small-cell lung cancer (NSCLC) treated with chemotherapy, and correlated that with the observed response to chemotherapy, time to progression and overall survival.

RESULTS

Differences were observed in the pattern of staining among the IAP proteins. The expression of c-IAP2 and XIAP was exclusively cytoplasmic. whereas c-IAP1 also displayed nuclear staining. The median expression of tumor cells for c-IAP1, c-IAP2, and XIAP was 70%, 45%, and 25%, respectively, and a correlation was observed between c-IAP1 and c-IAP2 (P = 0.004), and c-IAP1 and XIAP expression (P = 0.013). However, no association was seen between the expression of these proteins and sex, age, tumor size, stage, histology and grade of differentiation. Interestingly, expression of c-IAP1, c-IAP2, and XIAP did not predict response to chemotherapy. In addition, the expression of IAPs had no impact on the time to progression or overall survival of this group of patients.

CONCLUSIONS

Our results indicate that: 1) there are differences in the level of expression and in the subcellular distribution of c-IAP1, c-IAP2, and XIAP in tumors derived from NSCLC patients. 2) The expression of c-IAP1, c-IAP2 and XIAP does not predict the response to chemotherapy in patients with advanced NSCLC. 3) The relation between expression of IAPs and chemosensitivity in cancer patients may be more complex than anticipated by in vitro data.

Topoisomerase IIalpha and other drug resistance markers in advanced non-small cell lung cancer

Resistance to chemotherapy is common in non-small cell lung cancer. The aim of this study was to investigate the prognostic impact of in vitro established drug resistance markers on the response to chemotherapy in patients with advanced non-small cell lung cancer. Samples of 38 patients were analyzed by immunohistochemical staining, for topoisomerase IIalpha and IIbeta, Ki-67, MRP and LRP. In addition, mutation analysis of the topoisomerase IIalpha gene, the B/DNBS and the Tyr804 region, was performed. Lung tumor biopsies were taken prior for treatment with one of the following regimens; cisplatin/paclitaxel, cisplatin/VM26 or VP16, or carboplatin/VP16/ifosfamide. Seventeen patients obtained a partial response, 12 had stable disease and nine patients had progressive disease. None of the investigated markers was related with overall response rate. In one sample a point mutation in the B/DNBS region of the topo IIalpha gene was detected which substitutes IIe(510) with Val. This tumor had a partial response to four courses of cisplatin/VP16 treatment. The survival analysis showed that the patients with high topo IIalpha expressing tumors had a significantly worse survival compared with the patients with low or intermediate topo IIalpha expressing tumors. In conclusion, no relation was observed between expression of topoisomerase IIalpha, IIbeta, Ki-67, MRP or LRP and response rate. Furthermore, worse survival was seen in patients with high topoisomerase IIalpha expressing tumors. In one tumor sample, a newly described mutation in the B/DNBS region of the topo IIalpha gene was detected, which does not appear to be related to drug resistance.

Development of multidrug-resistance convertors: sense or nonsense?

This review describes the clinical relevance of the two drug transporters P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP) and the in vitro phenomenon which is referred to as multidrug resistance (MDR). The attempts to try to block these resistance mechanisms are summarized with specific attention for the intentionally designed "second generation" MDR-convertors. Potential explanations of the limited clinical success rate are given and recommendations for the design of future studies provided.

p53-regulated GML gene expression in non-small cell lung cancer. a promising relationship to cisplatin chemosensitivity

The GML gene (glycosylphosphatidylinositol-anchored molecule-like protein gene) is a novel gene specifically induced by wild-type p53, which may participate in cell cycle control or the cell apoptotic pathway. Recent experiments suggest that the expression of this novel gene in cancer cells is closely associated with sensitivity to certain anticancer drugs. To elucidate the role of the gene expression in cisplatin (CDDP) chemosensitivity of non-small cell lung cancer (NSCLC), 30 surgically resected materials were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). GML gene expression was detected in 9 (30%) samples. Its incidence was significantly higher in immunohistochemically p53-negative (P=0.040) or wild-type p53 tissues (P=0.041). On in vitro chemosensitivity testing using 29 primary tissues, six samples with GML gene expression showed good sensitivity to CDDP. In particular, in tissues with immunohistochemically p53-negative accumulation, those with GML gene expression showed significantly better in vitro sensitivity to CDDP (P=0.012). Clinically a good response to CDDP-based chemo(thermo)therapy for NSCLC patients with tumour residue or recurrence, was observed only in those with p53-negative accumulation and GML gene expression, in agreement with in vitro results. Thus, although the number of tested samples was small, GML gene expression is commonly detected in immunohistochemically p53-negative NSCLCs in close association with good sensitivity to CDDP. GML gene expression analysis may serve as a predictor of CDDP-based chemotherapy for patients with NSCLC.

Multidrug resistance in non-small-cell lung cancer

Resistance to cytotoxic drugs is an important cause of treatment failure. The causes are complex and may be determined by a combination of the tumour characteristics, such as the proportion of resting cells, adequacy of blood supply, and specific cellular mechanisms, as in the multidrug resistance phenotype. In lung cancer four types of multidrug resistance have been defined on the basis of the cellular drug targets involved, i.e., classical multidrug resistance (MDR), non-P-glycoprotein MDR (also called MRP), atypical MDR (mediated through altered expression of topoisomerases II) and lung resistance-related protein. In lung cancer the role of the different forms of multidrug resistance is complex and only partially understood.