Quantitative analysis of MDR1 (multidrug resistance) gene expression in human tumors by polymerase chain reaction

Compensatory expression of five chitin synthase genes, a response to stress stimuli, in Wangiella (Exophiala) dermatitidis, a melanized fungal pathogen of humans

Numerous chitin synthase structural (CHS) genes have been identified in fungi, and usually there are several CHS genes per species. Compensatory expression of one CHS gene in response to defects in other CHS genes has not been reported. Five chitin synthase structural (WdCHS) genes have been identified in the melanized human pathogen Wangiella dermatitidis: WdCHS1, WdCHS2, WdCHS3, WdCHS4 and WdCHS5. This study showed that increased WdCHS expression existed as a compensatory mechanism in response to stress induced by chitin synthase gene disruptions, or by exposure of the wild-type or two temperature-sensitive morphological mutants, for short or long periods, to 37 degrees C. In general, the compensatory responses varied with each WdCHS gene, and in accordance with the hypothesized functions of the chitin synthase (WdChsp) encoded. It is suggested that these compensatory responses indicate that WdCHS gene transcription in W. dermatitidis functions as part of a cell-wall integrity pathway in a manner similar to that recently described for Saccharomyces cerevisiae.

Modulation of P-glycoprotein expression and function by curcumin in multidrug-resistant human KB cells

Multidrug resistance (MDR) is a phenomenon that is often associated with decreased intracellular drug accumulation in the tumor cells of a patient, resulting from enhanced drug efflux. It is often related to the overexpression of P-glycoprotein (Pgp) on the surface of tumor cells, thereby reducing drug cytotoxicity. In this study, curcumin was tested for its potential ability to modulate the expression and function of Pgp in the multidrug-resistant human cervical carcinoma cell line KB-V1. Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) showed that treatment with 1, 5, and 10 microM curcumin for up to 72hr was able to significantly lower Pgp expression in KB-V1 cells. Curcumin (1-10 microM) decreased Pgp expression in a concentration-dependent manner and was also found to have the same effect on MDR1 mRNA levels. The effect of curcumin on Pgp function was demonstrated by rhodamine 123 (Rh123) accumulation and efflux in Pgp-expressing KB-V1 cells. Curcumin increased Rh123 accumulation in a concentration-dependent manner (1-55 microM) and inhibited the efflux of Rh123 from these cells, but did not affect the efflux of Rh123 from the wild-type drug-sensitive KB-3-1 cells. Treatment of drug-resistant KB-V1 cells with curcumin increased their sensitivity to vinblastine, which was consistent with an increased intracellular accumulation of Rh123. In addition, curcumin inhibited verapamil-stimulated ATPase activity and the photoaffinity labeling of Pgp with the prazosin analog [125I]iodoarylazidoprazosin in a concentration-dependent manner, demonstrating that curcumin interacts directly with the transporter. Thus, curcumin seems to be able to modulate the in vitro expression and function of Pgp in multidrug-resistant human KB-V1 cells. In summary, this study describes the duel modulation of MDR1 expression and Pgp function by the phytochemical curcumin, which may be an attractive new agent for the chemosensitization of cancer cells.

Expression of multidrug resistance genes MVP, MDR1, and MRP1 determined sequentially before, during, and after hyperthermic isolated limb perfusion of soft tissue sarcoma and melanoma patients

PURPOSE

Isolated, hyperthermic limb perfusion (ILP) with recombinant human tumor necrosis factor alpha and melphalan is a highly effective treatment for advanced soft tissue sarcoma (STS) and locoregional metastatic malignant melanoma. Multidrug resistance (MDR)-associated genes are known to be inducible by heat and drugs; expression levels of the major vault protein (MVP), MDR1, and MDR-associated protein 1 (MRP1) were determined sequentially before, during, and after ILP of patients.

PATIENTS AND METHODS

Twenty-one STS or malignant melanoma patients were treated by ILP. Tumor tissue temperatures were recorded continuously and ranged from 33.4 degrees C initially to peak values of 40.4 degrees C during ILP. Serial true-cut biopsy specimens from tumor tissues were routinely microdissected. Expression analyses for MDR genes were performed by real-time reverse transcriptase polymerase chain reaction and immunohistochemistry.

RESULTS

In 83% of the patients, MVP expression was induced during hyperthermic ILP. MVP-mRNA inductions often paralleled the increase in temperature during ILP. Increased MVP protein expressions either were observed simultaneously with the MVP-mRNA induction or were delayed until after the induction at the transcriptional level. Inductions of MDR1 and MRP1 were observed in only 13% and 27% of the specimens analyzed. Temperatures and drugs applied preferentially led to an induction of MVP and were not sufficient to induce MDR1 and MRP1 in the majority of tumors.

CONCLUSION

This study is the first to analyze the expression of MDR-associated genes sequentially during ILP of patients and demonstrates that treatment might lead to increased levels of MVP, whereas enhanced levels of MDR1 and MRP1 remain rare events.

Practical application of molecular genetic testing as an aid to the surgical pathologic diagnosis of sarcomas: a prospective study

The strong correlation of specific reciprocal translocations with individual tumor types and the demonstration that polymerase chain reaction (PCR)-based methods can detect translocations in tissue samples have stimulated interest in the role of molecular genetic testing in diagnostic surgical pathology. To evaluate the clinical utility of PCR-based molecular analysis of soft tissue neoplasms in routine surgical pathology, 131 consecutive soft tissue tumors submitted for molecular genetic testing at a tertiary care teaching hospital were prospectively analyzed over a 36-month period. RT-PCR was used to test tumor RNA for fusion transcripts characteristic of malignant round cell tumors (including Ewing sarcoma/primitive neuroectodermal tumor, desmoplastic small round cell tumor, and alveolar rhabdomyosarcoma), spindle cell tumors (including synovial sarcoma and congenital fibrosarcoma), and fatty tumors (myxoid liposarcoma). DNA sequence analysis was used to confirm the identity of all PCR products, and the PCR results were compared with the histopathologic diagnosis. We found that sufficient RNA for RT-PCR-based testing was recovered from 96% of the 131 cases and the percentage of tumors that tested positive for the associated characteristic fusion transcript was in general agreement with those reported in the literature. DNA sequence analysis of PCR products identified both variant transcripts and spurious PCR products, underscoring the value of product confirmation steps when testing formalin-fixed, paraffin-embedded tissue. Only in rare cases did testing yield a genetic result that was discordant with the histopathologic diagnosis. We conclude that PCR-based testing is a useful adjunct for the diagnosis of malignant small round cell tumors, spindle cell tumors, and other miscellaneous neoplasms in routine surgical pathology practice.

Biology and modulation of multidrug resistance (MDR) in hematological malignancies

Drug resistance is one of the most significant impediments in the treatment of hematological malignancies. There have been a number of studies on the incidence of P-GP expression in tumor cells or tissues, where detectable level of P-GP has been found in all types of hematological malignancies. P-GP expression and significance in the patients varies widely between reported studies on patients with different ages and different disease types. Some of this validation can be accounted for by the threshold used to consider a sample positive for P-GP. However, mdr-1 is likely important in determining therapeutic outcome in patients with AML, NHL, and MM, although there is a suggestion of a different "behavior" between adult and childhood AML. In contrast, the significant prognostic association with expression of MRP and LRP is not consistent with disease types and disease stages. Clinical trials of modulation of MDR have been limited by following major factors. One is inability of achieving adequate blood levels of the modulator to reverse MDR, and the other is presence of other resistance mechanisms in addition to P-GP. The fact that P-GP modulators alter the pharmacokinetics of anti-cancer drugs can potentially increase toxicities if the dose of anticancer drugs is not appropriately reduced. Recently, MDR modulators such as valspodar have demonstrated substantial inhibition of P-GP. In this presentation, a number of characteristics in VCR-resistant cells are reported. We demonstrate that acquisition of MDR or recovery from MDR phenotypes differ in one cell type to another, a marked correlation between P-GP and susuceptibility to oxygen radicals, and altered gene expression of cell membrane antigen and apoptosis cascade genes. The efficacy of immunotherapies depends on the altered or unchanged target molecules of MDR cells. Thus, immunotherapies or reversal agents that aim at these substances in tumor cells should be useful to overcome MDR phenotypes.

Astroglial expression of the P-glycoprotein is controlled by intracellular CNTF

BACKGROUND

The P-glycoprotein (P-gp), an ATP binding cassette transmembrane transporter, is expressed by astrocytes in the adult brain, and is positively modulated during astrogliosis. In a search for factors involved in this modulation, P-gp overexpression was studied in long-term in vitro astroglial cultures.

RESULTS

Surprisingly, most factors that are known to induce astroglial activation in astroglial cultures failed to increase P-gp expression. The only effective proteins were IFNgamma and those belonging to the IL-6 family of cytokines (IL-6, LIF, CT-1 and CNTF). As well as P-gp expression, the IL-6 type cytokines (but not IFNgamma) stimulated the expression of endogenous CNTF in astrocytes. In order to see whether an increased intracellular level of CNTF was necessary for induction of P-gp overexpression by IL-6 type cytokines, by the same cytokines analysis was carried out on astrocytes obtained from CNTF knockout mice. In these conditions, IFNgamma produced increased P-gp expression, but no overexpression of P-gp was observed with either IL-6, LIF or CT-1, pointing to a role of CNTF in the intracellular signalling pathway leading to P-gp overexpression. In agreement with this suggestion, application of exogenous CNTF (which is internalised with its receptor) produced an overexpression of P-gp in CNTF-deficient astrocytes.

CONCLUSION

These results reveal two different pathways regulating P-gp expression and activity in reactive astrocytes, one of which depends upon the intracellular concentration of CNTF. This regulation of P-gp may be one of the long searched for physiological roles of CNTF.

Downregulation of PGY1/MDR1 mRNA level in human KB cells by antisense oligonucleotide conjugates. RNA accessibility in vitro and intracellular antisense activity

Inhibition of PGY1/MDR1 (multidrug resistance gene 1) mRNA expression in multidrug resistant KB-8-5 cells by 5'-bis-pyrenyl-3'-aminohexyl oligodeoxyribonucleotide conjugates targeted to four sites of this mRNA has been investigated. Three of the tested oligonucleotide conjugates specifically inhibited the expression of PGY1/MDR1 mRNA as monitored by the RT-PCR assay. The oligonucleotide conjugate targeted to the region (+178; +194) of the PGY1/MDR1 mRNA decreased level of this mRNA to 10% compared to the control. Nuclease-resistant analogs of oligonucleotide, complementary to this MDR1 mRNA region therefore, might be considered as a prototype compounds for development of gene-targeted therapeutic agents for overcoming the MDR phenotype caused by the overexpression of the PGY1/MDR1 gene.

Human growth hormone gene transfer into tumor cells may improve cancer chemotherapy

Chemotherapy remains the main tool for the treatment of cancers, but is often hampered by tumor cell resistance. In this context, the transfer of genes able to accentuate the effect of anticancer drugs may constitute a useful approach, as exemplified by inactivation of nuclear factor (NF)-kappa B via direct transfer of a gene encoding a negative dominant of its natural inhibitor I kappa B, leading to improved response to cancer chemotherapy. Following our previous report that transfection of human growth hormone (hGH) gene into human monocytic cell lines may also inactivate NF-kappa B in another situation, we decided to test the consequences of hGH gene transfer on cancer treatments. We demonstrated that hGH-transfected human myeloid leukemia U937 cells were sensitized to an apoptotic signal mediated by the anticancer drugs. In parallel, we found that, by inhibiting degradation of I kappa B, hGH gene transfer diminished NF-kappa B entry into the nuclei of U937 cells exposed to daunorubicin. Finally, we report that hGH-transfected tumor cells engrafted in nude mice responded in vivo to chemotherapy with nontoxic doses of daunorubicin whereas, under the same conditions, control tumor cells remained insensitive. Overall, this study therefore suggests that hGH gene transfer may offer new therapeutic prospects in cancer therapy.

Cloning and characterization of a novel NMDA receptor subunit NR3B: a dominant subunit that reduces calcium permeability

We report the cloning and characterization of a novel NMDA receptor subunit cDNA, which encodes a predicted polypeptide of 1003 amino acids. Phylogenic analysis indicates that this new subunit is most closely related to NR3A. Therefore, we term it NR3B. Important functional domains of glutamate receptors, such as the ligand-binding domain, the channel pore, and the channel gate, are conserved in NR3B. NR3B mRNA was expressed highly in pons, midbrain, medulla, and the spinal cord, but at low levels in the forebrain and the cerebellum. Although NR3A mRNA expression decreases sharply after the second postnatal weeks, NR3B mRNA expression levels in whole brain were constant during postnatal development and into adult. Coimmunoprecipitation analysis showed that NR3B could form NMDA receptor complex with NR1a and NR2A subunits in heterologous cells. Although expression of NR3B alone did not reconstitute functional NMDA receptors, coexpression of NR3B reduced the Ca(2+) permeability of glutamate-induced currents in cells expressing NR1a and NR2A. These results indicate that NR3B is a dominant modulatory subunit that can modify the function of NMDA receptors. Since high Ca(2+) permeability of NMDA receptors is thought to be a key feature for NMDA receptors to play critical roles in neurodevelopment, synaptic plasticity, and neuronal death, NR3B may contribute to the regulation of these physiological and pathological processes.

Characterization of non-small-cell lung cancer cell lines established before and after chemotherapy

We established several in vitro drug-resistant cell lines after continuous, long-term exposure of each drug to elucidate mechanisms of drug resistance. Whether drug resistance in these in vitro resistant cell lines reflects clinical drug resistance still remains unanswered. In this study, a pair of lung cancer cell lines was established from one patient with squamous cell carcinoma of the lung, with one line being established before and one line after combination chemotherapy (cisplatin/ifosfamide/vindesine). Combination chemotherapy selected resistant EBC-2/R cells, which showed cross-resistance to 4-hydroxyifosfamide (3.2-fold), cisplatin (2.3-fold), and methotrexate (3.7-fold) and collateral sensitivity to vindesine (0.77-fold) compared with parent EBC-2 cells. EBC-2/R cells showed decrease in intracellular accumulation of cisplatin, increase in intracellular concentration of glutathione (GSH), and overexpression of multidrug resistance-associated protein (MRP) 3 when compared with EBC-2 cells. A single cycle of chemotherapy was not sufficient to select other mechanisms of drug resistance, such as multidrug resistance-1/P-glycoprotein, MRPs 1, 2, 4, and 5, lung resistance-related protein, metallothionein IIa, glutathione S-transferase pi, gamma-glutamylcysteine synthetase (light and heavy chain), and excision repair cross complementing 1. Sequentially we established two cell lines, which cell lines showed the differences of the cisplatin resistance, expression level of MRP3, intracellular GSH level and intracellular accumulation of cisplatin. A pair of cell lines will be useful to elucidate resistant mechanisms of cisplatin in heterogeneous lung cancer cells.

Impact of BCRP/MXR, MRP1 and MDR1/P-Glycoprotein on thermoresistant variants of atypical and classical multidrug resistant cancer cells

The impact of the ABC transporters breast cancer resistance protein/mitoxantrone resistance associated transporter (BCRP/MXR), multidrug resistance-associated protein 1 (MRP1) and multidrug resistance gene-1/P-glycoprotein (MDR1/PGP) on the multidrug resistance (MDR) phenotype in chemoresistance and thermoresistance was investigated in the parental human gastric carcinoma cell line EPG85-257P, the atypical MDR subline EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. Within the atypical MDR subline EPG85-257RNOV expression of BCRP/MXR and of MRP1 were clearly enhanced (vs. parental and classical MDR lines). MDR1/PGP expression was distinctly elevated in the classical MDR subline EPG85-257RDB (vs. parental and atypical MDR sublines). In all thermoresistant counterparts basal expression of BCRP/MXR, MRP1 and MDR1/PGP was increased relative to thermosensitive sublines. Although it could be shown that the overexpressed ABC transporters were functionally active, however, no decreased drug accumulations of doxorubicin, mitoxantrone and rhodamine 123 were observed. Thus, expression of BCRP/MXR, MRP1 and MDR1/PGP was found to be dependent on the appropriate type of chemoresistance; correlating with a classical or atypical MDR phenotype. Within the thermoresistant variants, however, the increase in ABC transporter expression did obviously not influence the MDR phenotype.

Cyclin D1 gene polymorphism is associated with an increased risk of urinary bladder cancer

Cyclin D1 is believed to play an important role in the genesis and/or progression of transitional cell cancer (TCC) of the urinary bladder. Cyclin D1 gene (CCND1) mRNA is alternatively spliced to produce two transcripts, and the splicing pattern may be modulated by a G to A single nucleotide polymorphism within the splice donor site of exon 4. This study was conducted to explore the association between the polymorphism and the susceptibility to and disease status of TCC of the bladder in 222 cases and 317 native Japanese controls. The relationship between the CCND1 polymorphism and the mRNA splicing pattern in TCC cells was evaluated by semi-quantitative reverse-transcription PCR. The CCND1 A allele was more frequently observed in the TCC group than the control group (P = 0.032) with a significant difference in the genotype frequency between the two groups (P = 0.029). The AA genotype was associated with a significantly higher risk of TCC compared with the AG+GG genotypes (adjusted odds ratio (aOR) = 1.76, 95% confidence interval (CI) = 1.09-2.84, P = 0.022). This association was observed more significantly in nonsmoking cases (aOR = 2.53; 95% CI = 1.28-4.51, P = 0.008). Looking at tumor grade, the presence of the A allele was associated with higher grade (= grade 3) tumors with a gene dosage effect (aOR = 1.77, CI = 1.16-2.69, P = 0.008). In tumor stage, although not significant, the AA + AG genotypes tended to be more frequently observed in cases with T1-4 tumors than those with Ta tumors (aOR = 1.94, 95% CI = 0.98-3.82, P = 0.057). The genotype seemed to influence the two alternatively spliced forms of the CCND1 mRNA because the ratio of the CCND1 transcript-b/transcript-a was significantly higher in cases with the AA genotype compared with those with the AG + GG genotypes. These data suggest that the CCND1 variant A allele may be associated with an increased risk of TCC of the bladder, especially in men without a history of smoking, and it may also have an effect on its disease status.

P-glycoprotein-actin association through ERM family proteins: a role in P-glycoprotein function in human cells of lymphoid origin

P-glycoprotein is a 170-kd glycosylated transmembrane protein, expressed in a variety of human cells and belonging to the adenosine triphosphate-binding cassette transporter family, whose membrane expression is functionally associated with the multidrug resistance phenotype. However, the mechanisms underlying the regulation of P-glycoprotein functions remain unclear. On the basis of some evidence suggesting P-glycoprotein-actin cytoskeleton interaction, this study investigated the association of P-glycoprotein with ezrin, radixin, and moesin, a class of proteins that cross-link actin filaments with plasma membrane in a human cell line of lymphoid origin and that have been shown to link other ion-pump-related proteins. To this purpose, a multidrug-resistant variant of CCRF-CEM cells (CEM-VBL100) was used as a model to investigate the following: (1) the cellular localizations of P-glycoprotein and ezrin, radixin, and moesin and their molecular associations; and (2) the effects of ezrin, radixin, and moesin antisense oligonucleotides on multidrug resistance and P-glycoprotein function. The results showed that: (1) P-glycoprotein colocalized and coimmunoprecipitated with ezrin, radixin, and moesin; and (2) treatment with antisense oligonucleotides for ezrin, radixin, and moesin restored drug susceptibility consistently with inhibition of both drug efflux and actin-P-glycoprotein association and induction of cellular redistribution of P-glycoprotein. These data suggest that P-glycoprotein association with the actin cytoskeleton through ezrin, radixin, and moesin is key in conferring to human lymphoid cells a multidrug resistance phenotype. Strategies aimed at inhibiting P-glycoprotein-actin association may be helpful in increasing the efficiency of both antitumor and antiviral therapies.

Molecular determinants of terminal growth arrest induced in tumor cells by a chemotherapeutic agent

Treatment with chemotherapy or radiation is not invariably cytotoxic to all tumor cells. Some of the cells that survive treatment recover and resume proliferation, whereas others undergo permanent growth arrest. To understand the nature of treatment-induced terminal growth arrest, colon carcinoma cells were exposed to doxorubicin, and surviving cells were separated into proliferating and growth-arrested populations. Only growth-arrested cells displayed phenotypic markers of cell senescence and failed to form colonies. Gene expression was compared between senescent and proliferating fractions of drug-treated cells by using cDNA microarray hybridization and reverse transcription-PCR. Drug-induced senescence was associated with inhibition of genes involved in cell proliferation and with coinduction of multiple intracellular and secreted growth inhibitors. Several tumor suppressors and other genes that are down-regulated in carcinogenesis were up-regulated in senescent tumor cells. Induction of most growth inhibitors was delayed but not abolished in cells with homozygous knockout of p53, in agreement with only limited p53 dependence of drug-induced terminal growth arrest. On the other hand, senescent cells overexpressed secreted proteins with antiapoptotic, mitogenic, and angiogenic activities, suggesting that drug-induced senescence is associated with paracrine tumor-promoting effects. About one-third of the genes up-regulated in senescent cells and almost all of the down-regulated genes showed decreased or delayed changes in p21(Waf1/Cip1/Sdi1)-deficient cells, indicating that p21 is a major mediator of the effects of p53 on gene expression. Elucidation of molecular changes in tumor cells that undergo drug-induced senescence suggests potential strategies for diagnostics and therapeutic modulation of this antiproliferative response in cancer treatment.

The expression of genes induced in melanocytes by exposure to 365-nm UVA: study by cDNA arrays and real-time quantitative RT-PCR

Ultraviolet A radiation (UVA; 320-400 nm) constitutes more than 90% of the terrestrial UV solar energy. This type of radiation generates reactive oxygen species and consequently induces DNA damage. UVA irradiation is now considered to be an important carcinogen agent especially in the development of melanoma. UVA radiation is known to activate several pathways in mammalian cells. We have used cDNA arrays to analyze differential gene expression in primary cultures of human melanocytes in response to 365-nm UVA. Among 588 genes studied, 11 were overexpressed. These genes included genes involved in cell cycle regulation (GADD45, CIP1/WAF1), in stress response (HSP70, HSP40, HSP86), in apoptosis (GADD153, tristetraproline) and genes encoding transcription factors (EGR-1, ETR-101, c-JUN, ATF4). This coordinate gene regulation was confirmed by real-time quantitative RT-PCR.

Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method

The two most commonly used methods to analyze data from real-time, quantitative PCR experiments are absolute quantification and relative quantification. Absolute quantification determines the input copy number, usually by relating the PCR signal to a standard curve. Relative quantification relates the PCR signal of the target transcript in a treatment group to that of another sample such as an untreated control. The 2(-Delta Delta C(T)) method is a convenient way to analyze the relative changes in gene expression from real-time quantitative PCR experiments. The purpose of this report is to present the derivation, assumptions, and applications of the 2(-Delta Delta C(T)) method. In addition, we present the derivation and applications of two variations of the 2(-Delta Delta C(T)) method that may be useful in the analysis of real-time, quantitative PCR data.

Expression of multidrug resistance-related genes in oral squamous cell carcinomas

To characterize the multidrug resistance (MDR) phenotype in human oral squamous cell carcinomas (OSCCs), the expression levels of four MDR-related genes (multidrug resistance, mdr1; multidrug resistance-associated protein, MRP; glutathione S-transferase-pi, GST-pi; and DNA topoisomerase II, topoII) were analyzed in OSCCs. Fifty-two OSCC tissues and 22 normal oral mucosal tissues were involved in this study. The expression of each gene was analyzed with a reverse-transcription polymerase chain reaction (RT-PCR) method using beta(2)m microglobulin (beta(2)m) mRNA as an endogenous control. The mean values of mdr1, MRP, GST-pi, and topoII gene expression relative to the beta(2)m gene in OSCC tissues were 0.37, 0.75, 0.66, and 1.11; those of normal oral mucosa were 0.40, 0.27, 0.62, and 0.91, respectively. The averaged expression levels of the MRP and topoII gene in OSCC tissues were higher than those of normal oral mucosas (P=0.001 and P=0.02, respectively). The expression levels of four MDR-related genes in OSCCs were not related with the degree of histologic cell differentiation, tumor stage, primary or recurred tumor, or the presence or absence of chemotherapy. Linear regression analysis showed a correlation between the expression levels of MRP and GST-pi in normal oral mucosas (r=0.596, P=0.003) and in OSCCs (r=0.287, P=0.039). The results suggest that MRP expression is activated during the tumorigenesis of OSCCs and that this may play a role in de novo drug resistance in OSCCs. These results should provide further insight into the complex role postulated for MDR-related genes in chemotherapy, carcinogenesis and tumor progression.

Paclitaxel and SN-38 overcome cisplatin resistance of ovarian cancer cell lines by down-regulating the influx and efflux system of cisplatin

Cisplatin (DDP) is one of the key drugs used to treat patients with ovarian cancer, although resistance to DDP can occur. Paclitaxel and SN-38 (an active metabolite of irinotecan (CPT-11)) are two drugs that are effective in patients with DDP-resistant ovarian cancer. To study how these drugs may overcome the intrinsic and / or acquired resistance of cancer cells to DDP, we investigated the effect of a combination of DDP with paclitaxel and a combination of DDP with SN-38 on three ovarian cancer cell lines, RTSG (intrinsically resistant cell line), KF (DDP-sensitive cell line), and KFra (acquired resistant cell line obtained from KF). We found that these combinations showed additive to synergistic antitumor activity. A time-dependent platinum (Pt) accumulation was observed in the DDP-sensitive KF cell line, while a decrease occurred in the KFra cell line. Little accumulation was observed in RTSG. Intracellular Pt accumulation was increased in all three cell lines by exposure to paclitaxel or SN-38. Ouabain, a Na(+),K(+)-ATPase inhibitor, decreased Pt accumulation in KF and KFra cell lines and inhibited the paclitaxel- and SN-38-induced increases in Pt accumulation in these cell lines. When we assessed the mRNA levels of the multidrug resistance-associated protein (MRP), which may be an efflux pump for DDP, the combination of paclitaxel or SN-38 with DDP down-regulated these levels, which are up-regulated by DDP alone. These results suggest that paclitaxel and SN-38 overcome DDP resistance of ovarian cell lines by controlling intracellular accumulation of DDP via both the influx and efflux systems.

Visceral primitive peripheral neuroectodermal tumors: a clinicopathologic and molecular study

Ewing sarcoma-primitive neuroectodermal tumor (EWS/PNET) belongs to the group of pediatric small round blue cell tumors; although EWS/PNET is classically a tumor of the soft tissue or bone in children and young adults, individual cases have been described in patients of all ages. A group of chromosomal translocations involving the EWS gene and a member of the Ets transcription factor family of genes has been detected in EWS/PNET, and heterogeneity in the precise breakpoint of the translocation has been shown to generate a group of related fusion transcripts that may have prognostic significance. Within the last decade, the clinicopathologic spectrum of EWS/PNET has been markedly expanded by recognition that the tumor may also have a visceral origin. To determine whether visceral EWS/PNET has the same pattern of genetic alterations and range of fusion transcripts as EWS/PNET of bone and soft tissue, we performed reverse-transcription polymerase chain reaction-based testing of formalin-fixed, paraffin-embedded tissue from a series of visceral tumors for which the diagnosis of EWS/PNET was well established. Together with additional cases compiled from the literature, EWS-Fli1 (or a related fusion transcript) was present in 18 of 19 visceral EWS/PNET, with a distribution of transcript types not statistically different from EWS/PNET of soft tissue and bone (P >.05, chi(2) test). These results firmly establish the genetic relationship between EWS/PNET of visceral sites, soft tissue, and bone.

Establishment and characterization of adriamycin-resistant human colorectal adenocarcinoma HCT-15 cell lines with multidrug resistance

The multidrug resistance (MDR) phenotype, either intrinsic and/or acquired, is discussed in relation to several MDR-associated markers such as P-glycoprotein (P-gp) encoded by mdr1, multidrug-resistance-associated protein (MRP) encoded by MRP and lung-resistance-associated protein (LRP) encoded by LRP. Well-characterized in vitro models are required to elucidate the mechanisms of MDR. The aim of the present study is the establishment of a drug-resistant subline from human colorectal adenocarcinoma HCT-15 that intrinsically expresses moderate levels of P-gp, MRP and LRP. Three adriamycin-resistant sublines (HCT-15/ADM1, HCT-15/ADM2 and HCT-15/ADM2-2) were established by stepwise exposure in growth medium that was supplemented with 25-200 ng/ml adriamycin-resulting in a 2.2- to 7.8-fold increase in IC(50) values by using the XTT assay. They were cross-resistant to MDR-related drugs, epirubicin, mitoxantrone, vincristine, etoposide and taxol, but not the MDR-unrelated drug, mytomycin C. The resistance to adriamycin was confirmed in vivo by a lack of sensitivity in athymic nude mice. Gene expression data for mdr1/P-gp, MRP/MRP and LRP/LRP on both mRNA and protein levels demonstrated that the molecules contributing to MDR in resistant sublines are mainly P-gp and partially MRP. The newly established adriamycin-resistant sublines of HCT-15 will provide clinically relevant tools to investigate how to overcome drug resistance and elucidate possible mechanisms of acquired MDR in human colon cancer.

Quantitative determination of gene expression in human lymphocytes assessed by reverse transcription-polymerase chain reaction coupled to high-performance liquid chromatography

Gene expression in human lymphocytes was assessed using reverse transcription and polymerase chain reaction amplification followed by ion-pair reversed-phase chromatography analysis. Competitive PCR was used to quantitate the desired cDNAs with a polivalent competitor adaptable to multiple novel mRNAs estimations with minor changes. Accuracy was 11.27+/- 11.87% (n = 7), as determined using standards. The coefficients of variation of the assessment of human OK12b were 7% (n = 6), 7.68 attmol/microg of total RNA, and 21% (n = 6), 0.93 attmol/microg of total RNA. Sample-to-sample variation in the reverse transcription and in the quantity and quality of RNA was attenuated by normalising results to beta-actin mRNA expression. The correlation between the OK12b/beta-actin ratio and competitive assessments of OK12b was 0.984, n = 6. The correlation between HPLC results and an independent method based on radionuclide uptake by the product, detected by electrophoretic separation, was 0.848, n = 10.

Cells from chronic myelogenous leukaemia patients at presentation exhibit multidrug resistance not mediated by either MDR1 or MRP1

Tetramethylrosamine (TMR) is excluded from P-glycoprotein (MDR1)-enriched cell lines, but it stains efficiently MDR1-poor parent lines. Application of the TMR resistance assay to cells obtained from chronic myelogenous leukaemia (CML) patients revealed, in all individuals, a significant resistance compared with healthy donors (P < 0.001). Cells from the same patients at later phases exhibited a further increase in TMR resistance. Doxorubicin was excluded from all cell samples obtained from CML patients at presentation. The resistance to TMR and doxorubicin was energy-dependent, and was not modulated by inhibitors of MDR1 and multidrug-resistance protein-1 (MRP1). Transcription of mRNAs suspected as relevant to multidrug resistance was assessed using comparative reverse transcription polymerase chain reaction. All cells from the CML patients transcribed high levels of MRP3, MRP4 and MRP5 compared with healthy donors. Low levels of MDR1, MRP1, MRP2, MRP6, lung resistance-related protein and anthracycline resistance-associated protein were equally transcribed in cells from healthy donors and CML patients. These results indicated that neither MDR1 nor MRP1 mediate the resistance in these cells. Our results shed light on a resistance mechanism operative in CML patients, which, together with the resistance to apoptosis, is responsible for the lack of response of CML patients to induction-type protocols used to treat acute myeloid leukaemia patients.

Expression of intercellular adhesion molecule-1 in the cortex of preserved rat kidneys

BACKGROUND

Prolonged cold ischemia has been shown to be an important factor in the development of posttransplant renal dysfunction. The exact mechanisms have not been completely defined. The expression of intercellular adhesion molecule-1 (ICAM-1) (CD 54) in rat kidneys stored in University of Wisconsin (UW) solution was studied in an attempt to correlate ischemia time with immunogenicity of the graft.

METHODS

Kidneys from male Lewis rats were perfused with UW solution, removed, and bathed in UW solution at 4 degrees C for 4, 12, 24, and 48 h. For the evaluation of expression of ICAM-1, immunohistochemical staining, Western blotting, and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) were performed.

RESULTS

Immunohistochemical staining in normal, nonischemic kidneys revealed that glomerular capillaries expressed ICAM-1 but that tubular cells did not. The preserved kidneys were analyzed by immunohistochemistry, Western blotting, and semiquantitative RT-PCR and showed increased transcription and expression of ICAM-1 in the cortex of the kidney. Expression reached a maximum at 24 h and declined at 48 h. The ICAM-1 protein expression in the preserved kidney cortex relative to control kidneys was increased at 4 h (1.68 +/- 0.60-fold of control kidneys, P = 0.06), 12 h (2.38 +/- 0.90-fold, P = 0.02), 24 h (3.70 +/- 1.29-fold, P = 0.01), and 48 h (2.00 +/- 0.54-fold, P = 0.01). The messenger RNA expression (the ratio of ICAM-1 to glyceraldehyde-3-phosphate dehydrogenase) in preserved kidneys cortex relative to control kidneys was increased at 4 h (1.19 +/- 0.14-fold of control kidneys), 12 h (1.38 +/- 0.16-fold), 24 h (1.77 +/- 0.29-fold), and 48 h (1.19 +/- 0.12-fold) (P < 0.05 for all time points).

CONCLUSIONS

We conclude that cold preservation of rat kidneys in UW solution induces increasing levels of ICAM-1 cell surface expression and gene transcription. Further study is necessary to determine if this increase in adhesion molecule expression increases the immunogenicity of the allograft and contributes to the development of posttransplant renal dysfunction.

Adenosine triphosphate-binding cassette superfamily transporter gene expression in severe male infertility

Cystic fibrosis transmembrane regulator (CFTR), multidrug-resistant (MDR)1, and multidrug resistance-associated (MRP) proteins belong to the ATP-binding cassette (ABC) transporter superfamily. A compensatory regulation of MDR1 and CFTR gene expression has been observed in CFTR knockout rodent intestine and in an epithelial cell line of human colon, whereas a high homology and similar anion binding site are shared by MRP and CFTR proteins. To provide better insight into the relationship among the expression behavior in vivo of the three genes in human testis, analysis of MDR1 and MRP gene expression in testicular biopsies was performed and related to the presence of CFTR gene mutations in congenital absence of the vas deferens (CAVD: n = 20) and non-CAVD (n = 30) infertile patients with azoospermia or severe oligozoospermia. A CFTR mutation analysis performed in both groups of patients supported the involvement of CFTR gene mutations in CAVD phenotype (85%) and in defective spermatogenesis (19%). Quantitative reverse transcription-polymerase chain reaction analysis of testicular tissue showed a CFTR-independent MDR1 and MRP gene expression in human testis, suggesting that the mechanisms underlying CFTR gene regulation in testis are different from those in intestine. These findings should contribute to the understanding of patterns of in vivo expression of CFTR, MDR1, and MRP genes in CFTR-related infertility.

SB203580, a specific inhibitor of p38-MAPK pathway, is a new reversal agent of P-glycoprotein-mediated multidrug resistance

P-glycoprotein (P-gp) is the plasma membrane transport pump responsible for efflux of chemotherapeutic agents from cells and is one of the systems that secures multidrug resistance (MDR) of neoplastic cells. In the present study, drug sensitive L1210 and multidrug resistant L1210/VCR (characterized by overexpression of P-gp) mouse leukemic cell lines were used as an experimental model. We have found that SB203580, a specific inhibitor of p38-MAPK pathway, significantly reduced the degree of the vincristine resistance in L1210/VCR cells. This phenomenon was accompanied by a decrease in the LC(50) value of vincristine from 3.203+/-0.521 to 0.557+/-0.082 microM. The LC(50) value of sensitive cells for vincristine was about 0.011 microM. The effect of SB203580 on L1210/VCR cells was associated with significantly increased intracellular accumulation of [3H]-vincristine in the concentration dependent manner. Prolonged exposure of resistant cells to 30 microM SB203580 did neither significantly influence the gene expression of P-gp, nor change the protein levels of p38-MAPK. Western blot analysis revealed that the MDR phenotype in L1210/VCR cells was associated with increased level and activity of cytosolic p38-MAPK. In resistant cells, the enhanced phosphorylation of both, p38-MAPK and ATF-2 (endogenous substrate for p38-MAPK) was found as well. In conclusion we could remark that SB203580, an inhibitor of p38 kinase pathway, reversed the MDR resistance of L1210/VCR cells. MDR phenotype of these cells is connected with increased levels and activities of p38-MAPK. These findings point to the possible involvement of the p38-MAPK pathway in the modulation of P-gp mediated multidrug resistance in the L1210/VCR mouse leukemic cell line. However, the mechanisms of SB203580 action should be further investigated.

Effect of P-glycoprotein expression on outcome in the Ewing family of tumors

This study was designed to determine the prognostic significance of multidrug resistance, mediated by P-glycoprotein (Pgp) expression, in Ewing sarcoma. The clinical and laboratory features, treatment protocol, and outcome of 75 patients with Ewing sarcoma or peripheral neuroectodermal tumor treated between 1972 and 1997 were reviewed. Pgp expression was tested with the monoclonal antibody JSB-1. Thirty-four (64%) of the 53 tissue samples from untreated patients stained positive for Pgp. Progression-free and overall survival were 44 and 59%, respectively, in patients with negative findings, and 28 and 41% in those with positive findings; neither difference was significant. Of the 12 relapsed patients, 6 (50%) expressed more Pgp after chemotherapy than at diagnosis and 4 (33%) expressed less. Within these subgroups, 5 out of 6 and 3 out of 4 died from the disease. No correlation was found between Pgp and known prognostic factors of Ewing tumors. Pgp expression is probably an intrinsic factor of Ewing tumors but has no correlation to prognosis.

Lipid metabolism and molecular changes in normal and atherosclerotic vessels

OBJECTIVES

a positive correlation between cholesterol esterification, acyl-CoA:cholesterol acyltransferase (ACAT), multidrug resistance (MDR1) gene expression and atherosclerotic lesions has been shown in human arteries. The objective of this study was to map the expression of MDR1, ACAT genes and the cholesteryl ester content in normal, atherosclerotic and varicose human vessels.

MATERIALS

vascular segments were obtained from seven cadaveric donors, 27 patients undergoing vascular surgery for severe atherosclerotic disease and 11 patients with saphenous vein varicosities.

METHODS

lipid analysis and RT-PCR of MDR1 and ACAT mRNAs were performed.

RESULTS

an increase in cholesteryl ester content and in ACAT and MDR1 expression was demonstrated in relation to the age in the arteries prone to atherosclerosis; this expression was maximal in arteries from symptomatic patients. In resistant arteries and in veins cholesteryl ester accumulation was rare and light, while ACAT and MDR1 expression was not related to the age of the subjects.

CONCLUSIONS

the results showed that an increase in MDR1 and ACAT expression may be responsible for the accumulation of cholesteryl esters as well as for cell growth rate acceleration in vessel sites prone to atherosclerosis.

A new quinoline derivative MS-209 reverses multidrug resistance and inhibits multiorgan metastases by P-glycoprotein-expressing human small cell lung cancer cells

Development of distant metastases and acquired multidrug resistance (MDR) are major problems in therapy for human small cell lung cancer (SCLC). MS-209 is a novel quinoline compound, which reverses P-glycoprotein (P-gp)-mediated MDR. We previously reported that MS-209 reversed in vitro MDR of human SCLC (SBC-3 / ADM and H69 / VP) cells expressing P-gp. In the present study, we determined the therapeutic effect of MS-209 in combination with chemotherapy against multiorgan metastases of MDR SCLC cells. SBC-3 / ADM cells expressing P-gp were highly resistant to etoposide (VP-16), adriamycin (ADM), and vincristine (VCR) in vitro, compared with parental SBC-3 cells lacking P-gp expression. MS-209 restored chemosensitivity of SBC-3 / ADM cells to VP-16, ADM, and VCR in a dose-dependent manner in vitro. Intravenous injection with SBC-3 or SBC-3 / ADM cells produced metastatic colonies in the liver, kidneys and lymph nodes in natural killer (NK) cell-depleted severe combined immunodeficiency (SCID) mice, though SBC-3 / ADM cells more rapidly produced metastases than did SBC-3 cells. Treatment with VP-16 and ADM reduced metastasis formation by SBC-3 cells, whereas the same treatment did not affect metastasis by SBC-3 / ADM cells. Although MS-209 alone had no effect on metastasis by SBC-3 or SBC-3 / ADM cells, combined use of MS-209 with VP-16 or ADM resulted in marked inhibition of metastasis formation by SBC-3 / ADM cells to multiple organs. These findings suggest that MS-209 reversed the MDR of SBC-3 / ADM cells, but not SBC-3 cells, growing in the various organs, and inhibited metastasis formation in vivo. Therefore, this chemosensitizing agent, MS-209, may be useful for treatment of refractory SCLC patients with multiorgan metastases.

MDR1 causes resistance to the antitumour drug miltefosine

Miltefosine (hexadecylphosphocholine) is used for topical treatment of breast cancers. It has been shown previously that a high percentage of breast carcinomas express MDR1 or MRP. We investigated the sensitivity of MDR1 -expressing cells to treatment with miltefosine. We show that cells overexpressing MDR1 (NCI/ADR-RES, KB-8-5, KB-C1, CCRF/VCR1000, CCRF/ADR5000) were less sensitive to miltefosine treatment when compared to the sensitive parental cell lines. HeLa cells transfected with MDR1 exhibited resistance to the compound, indicating that expression of this gene is sufficient to reduce the sensitivity to miltefosine. The resistance of MDR1-expressing cells to miltefosine was less pronounced than that to adriamycin or vinblastine. Expression of MDR2 did not correlate with the resistance to miltefosine. As shown by a fluorescence quenching assay using MIANS-labelled P-glycoprotein (PGP), miltefosine bound to PGP with a K(d)of approximately 7 microM and inhibited PGP-ATPase activity with an IC(50)of approximately 35 microM. Verapamil was not able to reverse the resistance to miltefosine. Concentrations of miltefosine up to approximately 60 microM stimulated, whereas higher concentrations inhibited the transport of [3H]-colchicine with an IC(50)of approximately 297 microM. Binding studies indicated that miltefosine seems to interact with the transmembrane domain and not the cytosolic nucleotide-binding domain of PGP. These data indicate that expression of MDR1 may reduce the response to miltefosine in patients and that this compound interacts with PGP in a manner different from a number of other substrates.

Reversal of vinblastine resistance in human leukemic cells by haloperidol and dihydrohaloperidol

Haloperidol, an antipsychotic, was investigated in cells overexpressing P-glycoprotein to detemine whether it was a clinically effective drug to reverse for reversing multidrug resistance (MDR) mediated by P-glycoprotein. A nontoxic concentration of haloperidol (1-30 microM) enhanced the cytotoxic effects of vinblastine (VBL) concentration-dependently in VBL-resistant human leukemia (K562/VBL) cells, but had no effect in the parent cells. Haloperidol also enhanced the cytotoxicities of epirubicin, doxorubicin and actinomycin D in the K562/VBL cells, but not those of idarubicin or cisplatin; this enhancement was less than that of the VBL toxicity in the VBL-resistant tumor line. Haloperidol increased the intracellular accumulation of VBL in the K562/VBL cells, and the binding of [3H]-azidopine to the cell-surface protein, P-glycoprotein, was inhibited by haloperidol in a concentration-dependent manner. Haloperidol was less potent than verapamil. Thus, haloperidol appeared to potentiate anticancer agents through the reversal of MDR by competitively inhibiting drug-binding to P-glycoprotein. In contrast, the main metabolite of haloperidol, dihydrohaloperidol, without antipsychotic activity, had less of an effect. Therefore, haloperidol might be useful in reversing drug-resistance.

Down-regulation of intrinsic P-glycoprotein expression in multicellular prostate tumor spheroids by reactive oxygen species

Intrinsic expression of the multidrug resistance (MDR) transporter P-glycoprotein (Pgp) may be regulated by reactive oxygen species (ROS). A transient expression of Pgp was observed during the growth of multicellular tumor spheroids. Maximum Pgp expression occurred in tumor spheroids with a high percentage of quiescent, Ki-67-negative cells, elevated glutathione levels, increased expression of the cyclin-dependent kinase inhibitors p27Kip1 and p21WAF-1 as well as reduced ROS levels and minor activity of the mitogen-activated kinase (MAPK) members c-Jun amino-terminal kinase (JNK), extracellular signal-regulated kinase ERK1,2, and p38 MAPK. Raising intracellular ROS by depletion of glutathione with buthionine sulfoximine (BSO) or glutamine starvation resulted in down-regulation of Pgp and p27Kip1, whereas ERK1,2 and JNK were activated. Down-regulation of Pgp was furthermore observed with low concentrations of hydrogen peroxide and epidermal growth factor, indicating that ROS may regulate Pgp expression. The down-regulation of Pgp following BSO treatment was abolished by agents interfering with receptor tyrosine kinase signaling pathways, i.e. the protein kinase C inhibitors bisindolylmaleimide I (BIM-1) and Ro-31-8220, the p21ras farnesyl protein transferase inhibitor III, the c-Raf inhibitor ZM 336372 and PD98059, which inhibits ERK1,2 activation. ROS involved as second messengers in receptor tyrosine kinase signaling pathways may act as negative regulators of Pgp expression.

Preliminary evaluation of caspases-dependent apoptosis signaling pathways of free and HPMA copolymer-bound doxorubicin in human ovarian carcinoma cells

The purpose of the study was to examine the role of caspases in signaling pathways of apoptosis induced by free doxorubicin (DOX) and HPMA copolymer-bound DOX (P(GFLG)-DOX) in human ovarian carcinoma cells. Sensitive A2780 and DOX resistant A2780/AD cells were exposed to different doses of drugs within 12, 18, 24 and 36 h. Caspase activity, expression of genes encoding human caspases 1-10, Apaf-1 and bcl-2 proteins and apoptosis were studied. In sensitive cells both free and P(GFLG)-DOX activated caspases 3, 7 and 9. In addition, P(GFLG)-DOX activated caspases 6 and 8. In resistant cells apoptosis induced by free DOX depended on the activation of caspases 2, 7 and 9, while caspase 3 was not involved; this explains the low degree of apoptosis induced by free DOX in resistant cells. P(GFLG)-DOX triggered the additional caspases 3, 6 and 8. A more pronounced degree of caspase activation and apoptosis after the action of P(GFLG)-DOX depended on the inhibition of bcl-2-encoded cellular defensive mechanisms and a more significant activation of Apaf-1. It was concluded that HPMA copolymer-bound DOX induced additional caspase-dependent apoptosis signaling pathways and the degree of the induction was higher, which led to more pronounced apoptosis when compared to free DOX.

Preliminary individual adjuvant therapy for gliomas based on the results of molecular biological analyses for drug-resistance genes

New adjuvant therapy individualized by the results of reverse transcription-polymerase chain reaction (RT-PCR) for drug-resistance genes has been used to treat malignant gliomas. Protocol studies for malignant gliomas were not so encouraging in their therapeutic results because of heterogeneity and the various drug-sensitivities of the tumors. Individualization of glioma therapy is recommended. Drug-resistance genes messenger ribonucleic acid (mRNA) expressions were investigated in drug-resistant human glioma cell lines derived from U87MG and 46 frozen samples of retrospectively examined neuroepithelial tumors (12 low grade neuroepithelial tumors, 16 Grade III gliomas, 11 glioblastomas, and 7 other malignant neuroepithelial tumors such as medulloblastomas and primitive neuroectodermal tumors) by RT-PCR with the specific primers for O6-methylguanine DNA methyltransferase (MGMT), multidrug-resistance gene 1 (MDR1), multidrug-resistance-associated protein (MRP), and glutathione-S-transferase-pi (GST-pi). Thirty-seven preliminary individual adjuvant therapies (IAT) based on RT-PCR results, mainly in MGMT expression, were performed on 30 consecutive patients with neuroepithelial tumors. In the retrospectively examined series, the initial response to 1-(4-amino-2-methyl-5-pyrimidynyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) was correlated most significantly to the MGMT mRNA expression among 11 independent prognostic factors (p = 0.0037) in multivariate logistic regression analysis. In the preliminary IAT, 17 of 32 evaluable therapies had a partial or complete response (53.1% response rate). Our IAT based on RT-PCR seemed to be more effective than conventional therapies for malignant gliomas.

Study of multi-drug resistant mechanisms in a taxol-resistant hepatocellular carcinoma QGY-TR 50 cell line

Cancer chemotherapy with taxol often fails due to acquired resistance of cancer cells, which is frequently associated with an overexpression of P-gp and alterations of beta-tubulin. A taxol-resistant cell line, QGY-TR50, derived from a human hepatocellular carcinoma (HCC) QGY-7703 cell line was used to investigate the mechanisms of taxol-resistance. QGY-TR50 cells showed more than 250-fold resistance to taxol and exhibited cross-resistance to other drugs including actinomycin D, doxorubicin, vinblastine, and vincristine. P-gp was highly expressed in QGY-TR50 cells. Expression levels of five human beta-tubulin isotypes (betaI-, betaII-,betaIII-, betaIva, and betaIvb-tubulin) were examined by real-time semi-quantitative PCR. Comparing with QGY-7703 cells, QGY-TR50 cells did not show any significant change in the expression levels of betaI-, betaIva, and betaIvb-tubulin. While a 1.2-fold increased in betaII-tubulin and a 0.5-fold decreased in betaIII-tubulin levels were observed. All results suggest that the P-glycoprotein could be one key factor involved in enhancing drug resistance in QGY-TR50 cells.

Retrovirus insertion and transcriptional activation of the multidrug-resistance gene in leukemias treated by a chemotherapeutic agent in vivo

To understand the molecular basis for multidrug-resistant (MDR) cancer cells in vivo, this study analyzed molecular changes of the mdr1a gene region in leukemia cells in mice during continuous treatment with vincristine. An inverse insertion of murine leukemia retrovirus (MuLV) into the 5'-flanking region of the mdr1a gene was found. This insertion was concomitantly accompanied by up-regulation of the mdr1a gene and the loss of chemosensitivity. Deletion of long-terminal repeat (LTR) sequences dramatically decreased the mdr1a promoter-driven reporter activity. The MuLV LTR insertion appears to exert its enhancer activity on mdr1a transcription during the appearance of MDR leukemia cells. Two mechanisms were postulated to explain the mdr1a gene activation by retrovirus insertion during in vivo chemotreatment: de novo insertion of MuLV induced by vincristine treatment and selection of a small fraction of pre-existing cells carrying MuLV insertion during vincristine treatment. No rearranged sequence was detected by polymerase chain reaction in parental cells. This result argued for the first mechanism. The randomly altered distribution of MuLV during repetitive chemotreatment might also be consistent with this hypothesis. On the other hand, the retrovirus insertion was detected at the same site of the mdr1a promoter region in 2 independent experiments, which suggests the second mechanism. It should be noted that in vivo chemotreatment using vincristine could generate the mdr1a-overexpressing cells through retrovirus insertion and the enhancer effect of the LTR.

Characterization of multidrug transporters in a normal renal tubular cell line resistant to doxorubicin. Multidrug transporters in the LLC-PK(1) cell line and its resistant counterpart

LLC-PK(1) is a proximal tubular cell line derived from normal pig kidney which has a structure and function similar to those of renal proximal tubular cells and which expresses baseline levels of P-glycoprotein. We isolated by drug selection a doxorubicin-resistant cell line (LLC-PK(1)/ADR) that exhibited a multidrug-resistant phenotype; this cell line was characterized by reduced intracellular drug concentrations, an increased drug extrusion, and increased expression of a 170-kDa P-glycoprotein detected by Western blot analysis with monoclonal antibody C219. In addition, an increased expression of MDR1 mRNA was seen by reverse transcriptase-polymerase chain reaction. These results suggest that it is possible to induce the overexpression of P-glycoprotein by chronic treatment with doxorubicin in a normal cell line that physiologically expresses low levels of this protein. This multi-resistant cell line could provide an interesting model for studying the role of P-glycoprotein and the consequence of its induction in a normal tissue.

Overcoming drug resistance in ovarian carcinoma

Advanced epithelial ovarian carcinoma is treated with cytoreductive surgery and combination chemotherapy with a platinum compound and paclitaxel. Despite this treatment strategy, most women eventually relapse and die of resistant disease. Preclinical studies have shown that alterations in drug accumulation, drug metabolism, DNA repair, cellular targets and/or cell survival pathways may cause this resistance. Clinical studies have employed modulators of resistance in combination with chemotherapy as a means to overcome drug resistance. The most extensively studied modulators, buthionine sulfoximine and valspodar, are involved in reversing resistance caused by glutathione and P-glycoprotein, respectively. A phase III study comparing paclitaxel and carboplatin with and without valspodar is ongoing. However, other approaches to overcoming drug resistance are necessary for the effective treatment of women with this disease.

Quantitative plasmid mixture analysis using the fluorogenic 5'-nuclease polymerase chain reaction assay

The fluorogenic 5'-nuclease polymerase chain reaction (PCR) assay has been shown to be useful for quantifying a given DNA target in a sample. Here we show how an existing PCR protocol can be amended for quantification by incorporating distinctive dual-labeled, sequence-specific oligonucleotide probes and resulting in a two- to threefold broader and more reliable dynamic range than that of conventional end-point analysis of PCR products. Moreover, we show a multiplex situation in which two targets, one normal and one mutated, can be amplified and quantified simultaneously and in the same reaction tube. Use of this novel approach for quantitative PCR applications eliminates the need for post-PCR processing and has clinical- and research-based diagnostic applications, particularly for measuring levels of mutations in a mixture.

Reversal effects of nomegestrol acetate on multidrug resistance in adriamycin-resistant MCF7 breast cancer cell line

BACKGROUND

Chemotherapy is important in the systematic treatment of breast cancer. To enhance the response of tumours to chemotherapy, attention has been focused on agents to reverse multidrug resistance (MDR) and on the sensitivity of tumour cells to chemical drugs. Hundreds of reversal drugs have been found in vitro, but their clinical application has been limited because of their toxicity. The reversal activity of progestogen compounds has been demonstrated. However, classical agents such as progesterone and megestrol (MG) also have high toxicity. Nomegestrol (NOM) belongs to a new derivation of progestogens and shows very low toxicity. We studied the reversal activity of NOM and compared it with that of verapamil (VRP), droloxifene (DRO), tamoxifen (TAM) and MG, and investigated the reversal mechanism, i.e. effects on the expression of the MDR1, glutathione S-transferase Pi (GSTpi), MDR-related protein (MRP) and topoisomerase IIalpha (TopoIIalpha) genes, as well as the intracellular drug concentration and the cell cycle. The aim of the study was to examine the reversal effects of NOM on MDR in MCF7/ADR, an MCF7 breast cancer cell line resistant to adriamycin (ADR), and its mechanism of action.

METHODS

MCF7/ADR cells and MCF7/WT, an MCF7 breast cancer cell line sensitive to ADR, were treated with NOM as the acetate ester. With an assay based on a tetrazolium dye [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide; MTT], the effects of various concentrations of NOM on MDR in MCF7/ADR cells were studied. Before and after the treatment with 5 microM NOM, the expression of the MDR-related genes MDR1, GSTpi, TopoIIalpha and MRP were assayed with a reverse transcriptase polymerase chain reaction (RT-PCR) immunocytochemistry assay. By using flow cytometry (FCM), we observed the intracellular ADR concentration and the effects of combined treatment with NOM and ADR on the cell cycle. Results collected were analysed with Student's t test.

RESULTS

NOM significantly reversed MDR in MCF7/ADR cells. After treatment NOM at 20, 10 and 5 microM, chemosensitivity to ADR increased 21-fold, 12-fold and 8-fold, respectively. The reversal activity of NOM was stronger than that of the precursor compound MG, and comparable to that of VRP. After treatment with 5 microM NOM, the expression of both the MDR1 and the GSTpi mRNA genes began to decline on the second day (P <0.05 and P <0.01, respectively), and reached the lowest level on the third day (both P <0.01); however, on the fifth day the expression levels began to increase again (both P <0.05). The expression of MRP and TopoIIalpha had no significant changes. Changes in the expression of P-glycoprotein (P-gp) and GSTpi were similar to those of their mRNA expressions, showing early declines and late increases. Two hours after treatment with 20, 10 and 5 microM NOM, the intracellular ADR concentration increased 2.7-fold, 2.3-fold and 1.5-fold respectively. However, NOM did not increase ADR accumulation in MCF7/WT cells. FCM data showed that after 48 h of combined administration of NOM (20 microM) and ADR (from low to high concentration), MCF7/ADR cells showed a gradual arrest at the G2M phase with increasing ADR dose. The arrest effect with combined drug treatment was stronger than that with the single ADR treatment.

CONCLUSION

MDR is the major mechanism of drug resistance in malignant tumour cells. To overcome MDR and to increase chemosensitivity, many reversal agents have been found. Most progestogen compounds have been demonstrated to have reversal effects, but we found no data on NOM, a new progestogen compound. Our results show that NOM has strong reversal activity. The reversal effects were stronger than those of the precursor compound, MG, and were comparable to that of VRP. Because NOM has low toxicity, it might have good prospects in clinical application. Using RT-PCR and immunocytochemistry assays, we studied the effects of NOM on MDR-related genes. The results were that NOM could markedly downregulate the mRNA and protein expression levels of MDR1 and GSTpi. TopoIIalpha and MRP gene expression showed no significant changes. It is known that P-gp induces MDR in tumour cells mainly by decreasing the intracellular drug concentration. After treatment with NOM, the intracellular drug concentration in MCF7/ADR cells increased significantly. Combined treatment with NOM and ADR induced arrest at the G2M phase. It is worth noting that NOM caused an early decrease and a late increase in the expression of some MDR-related genes in a time-dependent manner. The phenomena raise a question for the continued administration of reversal agents in clinics that merits further study. We demonstrate that NOM has strong reversal effects on MDR in MCF7/ADR cells. The reversal is via different routes, namely downregulating the mRNA and protein expression levels of MDR1 and GSTpi, increasing intracellular drug concentration and arresting cells at the G2M phase (NOM in combination with ADR). The reversal mechanism needs further study.

Coexpression patterns of EGFR, HER2, HER3 and HER4 in non-melanoma skin cancer

The receptor tyrosine kinases (RTKs) epidermal growth factor receptor (EGFR), HER2, HER3 and HER4 are involved in the pathogenesis of multiple human malignant neoplasias. However, their role in the carcinogenesis of basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) remains to be elucidated. In order to further define the role of these RTKs, 56 human skin tissue samples of normal skin, BCC and SCC were studied by conventional and differential and quantitative reverse transcriptase-polymerase chain reaction (rtPCR). EGFR and HER3 were predominantly expressed in the BCCs and SCCs, while HER2 was ubiquitously expressed. HER4 was not expressed in any sample. Since in vitro studies have provided compelling evidence that heterodimer formation of these receptors are associated with different signal transduction processes, coexpression patterns might be decisive for the induction and maintenance of a malignant phenotype. These results confirm this concept: isolated HER2 expression and EGFR/HER2 were predominantly found in normal skin, while HER2/HER3 and the triple expression of EGFR/HER2/HER3 were seen more frequently in the BCCs and SCCs compared with normal skin (50% and 40% compared with 26%, respectively). The activation of HER3, in addition to EGFR and HER2, might therefore be associated with the malignant phenotype. However, due to the small numbers in this study, further confirmation of the patterns is needed.

Intravenous injection of cycloheximide induces apoptosis and up-regulates p53 and Fas receptor expression in the rat liver in vivo

A single administration of protein synthesis inhibitor, cycloheximide (CHX) induces apoptosis of hepatocytes in vivo. We investigated the underlying mechanisms of this phenomenon and the role of p53 and Fas receptor using terminal dUTP nick end labeling (TUNEL), quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Rat liver tissue specimens were obtained at different time intervals after injection of CHX. The proportion of TUNEL-positive apoptotic hepatocytes increased with time and reached a plateau at 2.5h after the injection. The p53 and Fas receptor mRNAs and the proportion of immunoreactive p53-positive and Fas receptor-positive hepatocytes increased markedly with time from 1h after the administration. Since the time course of increased proportion of apoptotic hepatocytes does not parallel that of p53- or Fas receptor-positive hepatocytes and apoptotic hepatocytes appeared prior to up-regulation of p53 and Fas receptor expression, it is likely that the enhanced expression of p53 and Fas receptor is not involved directly in CHX-induced apoptosis of hepatocytes in vivo. Rats injected with a single intravenous dose of CHX, however, provide a simple and useful model for investigating the apoptotic machinery and the molecular mechanism of transcriptional up-regulation of p53 and Fas receptor in hepatocytes.

Malignant peripheral nerve sheath tumors with t(X;18). A pathologic and molecular genetic study

Spindle cell sarcomas often present the surgical pathologist with a considerable diagnostic challenge. Malignant peripheral nerve sheath tumor, leiomyosarcoma, fibrosarcoma, and monophasic synovial sarcoma may all appear similar histologically. The application of ancillary diagnostic modalities, such as immunohistochemistry and electron microscopy, may be helpful in the differentiation of these tumors, but in cases in which these adjunctive techniques fail to demonstrate any more definitive evidence of differentiation, tumor categorization may remain difficult. Cytogenetic and molecular genetic characterization of tumors have provided the basis for the application of molecular assays as the newest components of the diagnostic armamentarium. Because the chromosomal translocation t(X;18) has been observed repeatedly in many synovial sarcomas, it has been heralded as a diagnostic hallmark of synovial sarcoma. To formally test the specificity of this translocation for the diagnosis of synovial sarcoma, RNA extracted from formalin-fixed, paraffin-embedded tissue from a variety of soft tissue and spindle cell tumors was evaluated for the presence of t(X;18) by reverse transcriptase-polymerase chain reaction. Although 85% of the synovial sarcomas studied demonstrated t(X;18), 75% of the malignant peripheral nerve sheath tumors in our cohort also demonstrated this translocation. We conclude that the translocation t(X;18) is not specific to synovial sarcoma and discuss the implications of the demonstration of t(X;18) in a majority of malignant peripheral nerve sheath tumors.

The blood-brain barrier and oncology: new insights into function and modulation

The efficacy of chemotherapy for malignant primary or metastatic brain tumours is still poor. This is at least partly due to the presence of the blood-brain barrier (BBB). The functionality of the BBB can be explained by physicochemical features and efflux pump mechanisms. An overview of the literature is presented with emphasis on oncology. The BBB consists of capillary endothelial cells that lack fenestrations and are connected together with continuous tight junctions, with a high electrical resistance. Permeability of tight junctions can be increased in vitro by contraction of the cytoskeleton, caused by bradykinin agonists. Different efflux pumps are present in the BBB. Examples are P-glycoprotein (P-gp), organic anion transporters, (OAT) and multidrug-resistance-associated proteins (MRP)(1 and 3). These pumps act as a multi-specific efflux pump for various chemotherapeutic drugs. Experiments have shown that P-gp can be inhibited by different non-chemotherapeutic substrates such as cyclosporin A. The functionality in vivo of P-gp can be measured with positron emission tomography and [(11)C]-verapamil or with single photon emission computer tomography and(99m)Tc-sestamibi. MRP(1)and MRP(3)act as organic anion transporters that in vitro act as efflux pumps for substances that are conjugated or co-transported with glutathione and glucuronide, respectively. Methotrexate has been recently demonstrated to be transported by MRP(1)and MRP(3). Results of studies which demonstrate the clinical relevance and applicability of BBB modulators are eagerly awaited.

Chronic exposure of human ovarian carcinoma cells to free or HPMA copolymer-bound mesochlorin e6 does not induce P-glycoprotein-mediated multidrug resistance

The acquisition of multidrug resistance in human ovarian carcinoma A2780 cells was investigated after chronic exposure to free mesochlorin e6 monoethylenediamine (Mce6) and N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound Mce6 (P(GG)-Mce6). The dose that inhibits growth by 50% (IC50) was determined for free Mce6 (2.09 +/- 0.32 microM) and P(GG)-Mce6 (204.15 +/- 28.97 microM) to utilize similar effective doses of drug. A total of 14 drug exposures were performed over a period of 78 days. Cells were characterized by IC50 dose, MDR1 gene expression and anti-human P-glycoprotein (P-gp) antibody binding after each drug exposure. At the conclusion of the experiment, neither the A2780 cells habitually exposed to free Mce6 or P(GG)-Mce6 were significantly different than the control A2780 cells indicating cells did not acquire a MDR phenotype. The doxorubicin (DOX)-resistant A2780/AD cells served as a positive control.

Malignant peripheral nerve sheath tumors with t(X;18). A pathologic and molecular genetic study

Spindle cell sarcomas often present the surgical pathologist with a considerable diagnostic challenge. Malignant peripheral nerve sheath tumor, leiomyosarcoma, fibrosarcoma, and monophasic synovial sarcoma may all appear similar histologically. The application of ancillary diagnostic modalities, such as immunohistochemistry and electron microscopy, may be helpful in the differentiation of these tumors, but in cases in which these adjunctive techniques fail to demonstrate any more definitive evidence of differentiation, tumor categorization may remain difficult. Cytogenetic and molecular genetic characterization of tumors have provided the basis for the application of molecular assays as the newest components of the diagnostic armamentarium. Because the chromosomal translocation t(X;18) has been observed repeatedly in many synovial sarcomas, it has been heralded as a diagnostic hallmark of synovial sarcoma. To formally test the specificity of this translocation for the diagnosis of synovial sarcoma, RNA extracted from formalin-fixed, paraffin-embedded tissue from a variety of soft tissue and spindle cell tumors was evaluated for the presence of t(X;18) by reverse transcriptase-polymerase chain reaction. Although 85% of the synovial sarcomas studied demonstrated t(X;18), 75% of the malignant peripheral nerve sheath tumors in our cohort also demonstrated this translocation. We conclude that the translocation t(X;18) is not specific to synovial sarcoma and discuss the implications of the demonstration of t(X;18) in a majority of malignant peripheral nerve sheath tumors.

Quantitative reverse transcription-polymerase chain reaction to study mRNA decay: comparison of endpoint and real-time methods

Four quantitative reverse transcription-PCR (RT-PCR) methods were compared to evaluate the time course of mRNA formation and decay. Mouse fibroblasts (NIH 3T3) transfected with the human beta-globin open reading frame/c-myc 3'-untranslated region chimeric gene under control of the c-fos promoter (fos-glo-myc) were used for serum-inducible transcription. The amount of fos-glo-myc mRNA, relative to beta-actin, was measured by quantitative, RT-PCR at various times following the addition of serum to serum-starved fibroblasts transfected with the chimeric gene. Both endpoint (band densitometry and probe hybridization) and real-time (SYBR green and TaqMan) PCR methods were used to assay the identical cDNA. The real-time methods produced a 4- to 5-log dynamic range of amplification, while the dynamic range of the endpoint assays was 1-log. The real-time and probe hybridization assays produced a comparable level of sensitivity that was considerably greater than band densitometry. The coefficient of variation from 22 replicate PCR reactions was 14.2 and 24.0% for the SYBR green and TaqMan detection, respectively, and 44.9 and 45.1% for the band densitometry and probe hybridization assays, respectively. The rank order for the values of r(2) obtained from the linear regression of the first-order mRNA decay plots was SYBR green > TaqMan > probe hybridization > band densitometry. Real-time PCR is more precise and displays a greater dynamic range than endpoint PCR. Among the real-time methods, SYBR green and TaqMan assays produced comparable dynamic range and sensitivity while SYBR green detection was more precise and produced a more linear decay plot than TaqMan detection.