Multidrug Resistance Gene Product Research Articles

The effects of MDR-1 gene polymorphisms on the clinical course of chronic hepatitis B infection

Aims: Chronic HBV infection is associated with high morbidity and mortality rate due to increased risk of hepatic cirrhosis and hepatocellular cancer. Treatment modilities and resistance is currently investigated. Several mechanisms were underlying in drug resistance. P-glycoprotein (P-gp), the product of multidrug resistance gene (MDR-1), is well-known mechanism of MDR phenotype. MDR gene C1236T polymorphism is associated with decreased p-gp function. The mutation of MDR gene can affect the clinical course of disease and response rate to treatment. It was aimed to investigate the relationship between MDR gene polymorphism and clinical course and treatment responses in chronic HBV infection in our study. Methods: A total of 90 (male/female:69/21) patients with chronic HBV infection under Lamivudine treatment was enrolled in this study. Mean ages were 49.8±12.6 (range:22-75) years. The patients were categorized as: Treatment responded (group 1: HBV-DNA is negative at 24th week) and treatment refractory (group 2: HBV-DNA is still positive after 24th week). Group 1 was consisted of 51 (M/F: 38/13) and group 2 was consisted of 39 (M/F: 31/9) patients. There was no significant difference between ages and genders of two groups. Histologic activity indexes (HAI), total bilirubin, AST and ALT levels, HBV-DNA titers were significantly higher in the patients in group 2 than group 1 (p<0.05). Results: Genotype distributions; homozygous CC genotype was in 8 (15.7%),heterozygous CT genotype was in 37 (%72.5), homozygous TT genotype wasin 6 (11.8%) in patients at group 1. Homozygous CC genotype was in 13 (33.3%), heterozygous CT genotype was in 21 (53.8%), homozygous TT genotype was in 5 (12.8%) in patients at group 2. CC genotype was more common in group 2 than group 1 (p=0.044). C and T alleles’ frequencies in the group 1 and 2 were 51.96% and 60.26%, 48.04% and 39.74%, respectively (p>0.05). The patients with YMDD mutation positive at group 2 (n:11), 5 (45%) had have CC genotype, 5 (45%) had have CT, 1 (9%) had have TT genotype.The patients with YMDD mutation negative at group 2 (n:8), 3 (37%) patients had have CC and 5 (63%) patients had have CT genotype. CC genotype was more common in the patients with YMDD mutation positive than group 1 (p=0.043). Moreover, CC genotype was more common in the patients with HBV-DNA positive at 12nd month of Lamivudine treatment than group 1 (p=0.042). Conclusion: Consequently; MDR-1 and p-gp polymorphisms are important factors in the clinical course of chronic HBV infection and may influence the treatment responses. In the current study, it was found that the CC genotype of MDR-1 gene C1236T was more common in the patients with lamivudine resistant HBV infection.

Phosphorylation of rpS3 by Lyn increases translation of Multi-Drug Resistance (MDR1) gene

Lyn, a tyrosine kinase that is activated by double-stranded DNA-damaging agents, is involved in various signaling pathways, such as proliferation, apoptosis, and DNA repair. Ribosomal protein S3 (RpS3) is involved in protein biosynthesis as a component of the ribosome complex and possesses endonuclease activity to repair damaged DNA. Herein, we demonstrated that rpS3 and Lyn interact with each other, and the phosphorylation of rpS3 by Lyn, causing ribosome heterogeneity, upregulates the translation of p-glycoprotein, which is a gene product of multi-drug resistance gene 1. In addition, we found that two different regions of the rpS3 protein are associated with the SH1 and SH3 domains of Lyn. An in vitro immunocomplex kinase assay indicated that the rpS3 protein acts as a substrate for Lyn, which phosphorylates the Y167 residue of rpS3. Furthermore, by adding various kinase inhibitors, we confirmed that the phosphorylation status of rpS3 was regulated by both Lyn and doxorubicin, and the phosphorylation of rpS3 by Lyn increased drug resistance in cells by upregulating p-glycoprotein translation.

Transwell-Hypoxia Method Facilitates the Outgrowth of 3D-Printed Collagen Scaffolds Loaded with Cryopreserved Patient-Derived Melanoma Explants.

A previous study from our laboratory demonstrated the effects of in vitro three-dimensional (3D)-printed collagen scaffolds on the maintenance of cryopreserved patient-derived melanoma explants (PDMEs). However, it remains unknown whether 3D-printed collagen scaffolds (3D-PCSs) can be harmonized with any external culture conditions to increase the growth of cryopreserved PDMEs. In this study, 3D-PCSs were manufactured with a 3DX bioprinter. The 3D-printed collagen scaffold-on-frame construction was loaded with fragments of cryopreserved PDMEs (approximately 1-2 mm). 3D-PCSs loaded with patient-derived melanoma explants (3D-PCS-PDMEs) were incubated using two types of methods: (1) in transwells in the presence of a low concentration of oxygen (transwell-hypoxia method) and (2) using a traditional adherent attached to the bottom flat surface of a standard culture dish (traditional flat condition). In addition, we used six different types of media (DMEM high glucose, MEM α, DMEM/F12, RPMI1640, fibroblast basal medium (FBM), and SBM (stem cell basal medium)) for 7 days. The results reveal that the culture conditions of MEM α, DMEM/F12, and FBM using the transwell-hypoxia method show greater synergic effects on the outgrowth of the 3D-PCS-PDME compared to the traditional flat condition. In addition, the transwell-hypoxia method shows a higher expression of the MMP14 gene and the multidrug-resistant gene product 1 (MDR1) than in the typical culture method. Taken together, our findings suggest that the transwell-hypoxia method could serve as an improved, 3D alternative to animal-free testing that better mimics the skin's microenvironment using in vitro PDMEs.

Gene Polymorphism of Tacrolimus-Metabolizing Enzymes Associated With Impaired Absorption of Tacrolimus Following Allogeneic Hematopoietic Stem Cell Transplantation: A Case Report

ObjectiveTo elucidate the mechanisms by which orally administered tacrolimus was not absorbed in a patient following allogeneic hematopoietic stem cell transplantation. Clinical CourseA 17-year-old girl with acute myeloid leukemia underwent HLA-haploidentical peripheral blood stem cell transplantation following fludarabine, busulfan, and total-body irradiation. Graft-vs-host disease prophylaxis was post-transplant cyclophosphamide, followed by intravenous tacrolimus and mycophenolate mofetil. When tacrolimus was switched to oral administration, its blood level declined rapidly, resulting in development of acute graft-vs-host disease, which was ameliorated by switching back to intravenous administration. Methods/ResultsTo elucidate if impaired tacrolimus absorption could be related to genetic polymorphism of tacrolimus-metabolizing enzymes, we analyzed gene polymorphisms of cytochrome P450 3A4, cytochrome P450 3A5, and multidrug resistance 1 (MDR1). The patient had wild-type cytochrome P450 3A4 (*1/*1) and variant-type cytochrome P450 3A5 (*3/*3), while MDR1 genes (2677A/G, 3435C/C) were wild-type. ConclusionWild-type MDR1 gene product P-glycoprotein expressed in the intestine reduces drug absorption from the gastrointestinal tract and may have contributed to low blood levels of tacrolimus in this patient when tacrolimus was orally administered.

Vimentin Protects Cells Against Doxorubicin and Vincristine

Vimentin is a class III IF protein that among other functions in the cells interacts with mitochondria causing the elevation of their membrane potential. This interaction may be very important although they are still poorly understood. In this study vimentin-null cells and derivative cell lines that express different mutant forms of human vimentin were used as a model to investigate the ability of this protein to provide the resistance of cells against antitumor drugs and its dependence on the interaction with mitochondria. The half maximal inhibitory concentration (IC50) of vincristine and doxorubicin, two commonly used anticancer drugs, demonstrated that drug resistance of the cells increases only with the vimentin forms that can bind mitochondria. Mutant forms of vimentin lacking the ability to bind mitochondria had no effect on drug resistance. The effect of vimentin on cell viability was observed in the presence of verapamil, the inhibitor of P-glycoprotein, product of Multi-Drug Resistance (MDR) gene. We propose that the interaction of mitochondria with vimentin protects and stabilizes these organelles in the stress conditions.

The implication of the Aryl Hydrocarbon Receptor (AhR) on the expression of Mdr1 induced by exposure to sodium arsenite on primary hepatocytes

Eighty percent of human ovarian and endometrial cancers express receptors for luteinizing hormone–releasing hormone (LHRH-R). These receptors can be used for targeted chemotherapy with agents such as AN-152, in which doxorubicin is linked to analog [D-Lys6]-LHRH. Direct receptor-mediated antiproliferative effects of AN-152 have been shown in vitro and in vivo. In LHRH-R positive cell lines, AN-152 was more effective than doxorubicin at equimolar concentrations. This study was designed to investigate the mechanism of action of AN-512 in ovarian and endometrial cancer cells in vitro.Three ovarian (SKOV-3, NIH:OVCAR-3, EFO-21) and 2 endometrial carcinoma cell lines (Ishikawa, HEC-1A) were evaluated for doxorubicin- or AN-152–induced apoptosis. Internalization and cytoplasmic release of AN-152 was monitored by confocal laser scanning microscopy and inhibited by chloroquine. Cleavage of doxorubicin from AN-152 was inhibited by carboxylesterase inhibitor, diisopropyl fluorophosphate (DFP). The surface expression of multidrug resistance-1 (MDR-1) gene product P-glycoprotein (Pgp) was measured by flow cytometry.Induction of apoptosis by AN-152 in LHRH-R positive Ishikawa, HEC-1A, EFO-21, and NIH:OVCAR-3 cells was significantly higher than that induced by doxorubicin, whereas the percentage of apoptotic cells in LHRH-R negative SKOV-3 was higher after treatment with doxorubicin. In EFO-21 cells, apoptosis induced by AN-152 was inhibited by pretreatment with chloroquine. Pretreatment with DFP increased AN-152–induced apoptosis in LHRH-R positive cells and reduced apoptosis in LHRH-R negative SKOV-3. Both AN-152 and doxorubicin induced surface expression of MDR-1 gene product Pgp, but the effect of AN-152 was smaller than that of doxorubicin. Pgp surface expression induced by AN-152 was inhibited by pretreatment with DFP.AN-152 is internalized through the LHRH-R and induces apoptosis in LHRH-R–positive human ovarian and endometrial cancer cell lines without activating the MDR-1 efflux pump system. The efficacy and specificity of AN-152 is inversely correlated with carboxylesterase activity.

Functional expression of P-glycoprotein in the hepatic canalicular membrane of developing rats

□ P-glycoprotein (P-gp), the multidrug resistance gene product, is expressed in a normal liver exclusively on the canalicular membrane of the hepatocyte. The objective of this study was to examine the effect of age on the P-gp transport system using canalicular membrane (cLPM) vesicles isolated from the liver of developing (22 days old) and adult rats. No differences in protein yield, intravesicular volumes, and enrichments of cLPM enzymes or enzymes representing contamination of subcellular organelles were found for vesicles isolated from both groups, demonstrating the isolation of similar cLPM vesicle preparations. The transport of daunomycin (DNM), a P-gp substrate, was used to study age-related functional differences in P-gp. DNM uptake in the presence of ATP was greater than uptake in the absence of ATP in both young and adult cLPM vesicles, showing that P-gp is functional in both groups. In young and adult groups only ATP was a potent stimulator of transport when compared with ATP degradation products and a nonhydrolyzable ATP analogue. Although ATP-dependent uptake tended to be greater in the adult compared to the young, there was no statistically significant difference in DNM kinetics (Vmax, km, γ) between groups. Canalicular membrane from the young rats showed decreased fluidity, as assessed by the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene; however there was no significant difference between groups. Examination of P-gp expression using the monoclonal antibody C219 revealed similar levels of expression in the young as in the adult. Our results suggest that P-gp in the bile canaliculus of developing rats is functional with similar levels of function and expression as observed in the adult.

Multidrug resistance gene and its relationship to ulcerative colitis and immune status of ulcerative colitis.

We examined the relationship among the multidrug resistance (MDR1) gene product P-glycoprotein (P-gp), ulcerative colitis, and immune status under ulcerative colitis. MDR1 P-gp expression and interleukin-8 levels in ulcerative colitis were determined using immunohistochemistry and a double-antibody sandwich avidin-biotin complex-enzyme-linked immunosorbent assay, respectively. Nitric oxide content and nitric oxide synthase activity in the colonic mucosa were determined using a colorimetric method; CD4(+) and CD25(+) T cell subset percentages in the peripheral blood were determined by flow cytometry. The positive expression rate of P-gp in patients with ulcerative colitis (17.4%) was significantly lower than that in the control group (31.4%). The expression rate decreased to 10.1, 9.2, and 8.3% after 12, 18, and 24 months of treatment, respectively, which were significantly lower than the expression rate before treatment (17.4%). P-gp expression levels during the remission phase and active phase of ulcerative colitis were 15.2 and 17.1%, respectively, which were significantly lower than that in normal controls (31.4%). Compared with P-gp-negative patients, nitric oxide content, nitric oxide synthase activity, and interleukin-8 levels were significantly higher in P-gp-positive patients with moderately active, severely active, early onset, chronic relapsing, chronic persistent, and acute fulminant ulcerative colitis. CD4(+) and CD25(+) T cell subsets were significantly lower in the peripheral blood of patients with severely active and acute fulminant ulcerative colitis than in control subjects. Expression of the multidrug resistance gene and its product P-gp was observed in normal colon tissues and may be closely related to ulcerative colitis.

Calcium channel blocker verapamil accelerates gambogic acid-induced cytotoxicity via enhancing proteasome inhibition and ROS generation

Verapamil (Ver), an inhibitor of the multidrug resistance gene product, has been proved to be a promising combination partner with other anti-cancer agents including proteasome inhibitor bortezomib. Gambogic acid (GA) has been approved for Phase II clinical trials in cancer therapy in China. We have most recently reported that GA is a potent proteasome inhibitor, with anticancer efficiency comparable to bortezomib but much less toxicity. In the current study we investigated whether Ver can enhance the cytotoxicity of GA. We report that (i) the combination of Ver and GA results in synergistic cytotoxic effect and cell death induction in HepG2 and K562 cancer cell lines; (ii) a combinational treatment with Ver and GA induces caspase activation, endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) production; (iii) caspase inhibitor z-VAD blocks GA+Ver-induced apoptosis but not proteasome inhibition; (iv) cysteine-containing compound N-acetylcysteine (NAC) prevents GA+Ver-induced poly(ADP-ribose) polymerase cleavage and proteasome inhibition. These results demonstrate that Ver accelerates GA-induced cytotoxicity via enhancing proteasome inhibition and ROS production. These findings indicate that the natural product GA is a valuable candidate that can be used in combination with Ver, thus representing a compelling anticancer strategy.

Inhibitory effects of mild hyperthermia plus docetaxel therapy on ER(+/−) breast cancer cells and action mechanisms

The purpose of this study was to verify that a combination of mild hyperthermia and docetaxel chemotherapy produces synergistic antitumor effects and to explore the action mechanisms of this treatment approach. The effects of docetaxel on the proliferation of cells from the estrogen receptor (ER)-positive human breast cancer cell line MCF-7 and the ER-negative human breast cancer cell line MDA-MB-453 were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and effective experimental concentrations of docetaxel were determined. The effects of mild hyperthermia plus docetaxel therapy on apoptosis rate in the MCF-7 and MDA-MB-453 human breast cancer cell lines were analyzed by using flow cytometry with Annexin-V fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining. The effects of these combined treatments on cell cycle progression in the MCF-7 and MDA-MB-453 human breast cancer cell lines were examined by using flow cytometry. The effects of these combined treatments on the expression of apoptosis-related proteins and proteins in the mitogen-activated protein kinase (MAPK) pathways were analyzed by using Western blotting. The effects of these combined treatments on the expression of the heat shock protein 70 (HSP70) and the multi-drug resistance (MDR) gene product P-glycoprotein (Pgp) were examined by using Western blotting. The results showed that the half-maximal inhibitory concentration (IC50) of docetaxel for MCF-7 and MDA-MB-453 cells was 19.57±1.12 and 21.64±2.31 μmol/L respectively. Mild hyperthermia with docetaxel therapy could increase apoptosis rate in the MCF-7 and MDA-MB-453 cells. Apoptosis rate in MCF-7 and MDA-MB-453 cells was increased from (23.66±3.59)% and (18.51±3.17)% in docetaxel treatment group to (47.12±6.73)% and (55.16±7.42)% in mild hyperthermia plus docetaxel group, indicating that the mild hyperthermia and docetaxel therapeutic approaches exhibited significant synergistic antitumor effects. Treatments of mild hyperthermia plus docetaxel induced G2/M cell cycle arrest in the MCF-7 and MDA-MB-453 cells. Western blotting demonstrated that proteins in the MAPK pathway were expressed at higher levels in docetaxel-treated cells following mild hypothermia than those in cells treated with docetaxel alone. As compared with blank control group, cells from the mild hyperthermia plus docetaxel group exhibited significantly decreased B-cell lymphoma 2 (Bcl-2) protein expression but slightly increased Bcl-2-associated X protein (Bax) expression. Western blotting results revealed that HSP70 and Pgp expression levels were significantly increased following mild hypothermia. It was concluded that treatments of mild hyperthermia plus docetaxel inhibited the proliferation of human breast cancer cells, promoted apoptosis of breast cancer cells, and produced synergistic antitumor effects.

Influences of “Spasmolytic Powder” on Pgp Expression of Coriaria Lactone-Kindling Drug-Resistant Epileptic Rat Model

The earliest records of traditional Chinese medicine (TCM) prevention and treatment of epilepsy dated back to famous "Huang Di Nei Jing." TCM "spasmolytic powder" (equal-ratio compatibility of scorpion and centipede) is a famous prescription which was recognized as a useful add-on drug for refractory epilepsy in clinical observations. Multidrug resistance gene (mdr1) product Pgp overexpression in blood-brain barrier and blood-cerebrospinal fluid barrier is well recognized as the drug resistance mechanism of refractory epilepsy. Here, we established the drug-resistant epilepsy Sprague-Dawley rat model induced by Coriaria Lactone and treated these rats with topiramate and verapamil and low dose, middle dose, and high dose of spasmolytic powder by intragastric administration for 1 week. Electroencephalogram, real-time PCR, and immunohistochemistry were respectively used to detect epileptic discharge frequencies and amplitudes and expression of mdrl mRNA and Pgp on hippocampus and temporal lobe of rats. The results showed that the seizure decreases significantly in the high- and middle-dose groups of spasmolytic powder and topiramate group; in addition, mdr1 mRNA and Pgp expressions on hippocampus and temporal lobe of these drug intervention groups were significantly less than the model group (P < 0.05). These findings indicate that inhibition of intracephalic Pgp expression is possibly one of mechanisms of spasmolytic powder treating refractory epilepsy.

Increases in Bioavailability of Poorly Absorbed Drug by Acylcarnitine

We examined the effect of acylcarnitines on the in situ bioavailability of lucifer yellow (LY) from the loops of small and large intestines of rats. The area under the blood concentration of LY versus time curve (AUC) from the jejunum was significantly increased by the treatments of the loop with 100 µM lauroylcarnitine (LC) or 100 µM palmitoylcarnitine (PC) (fourfold and 17-fold, respectively). No marked change in the expression of claudin-4 protein was observed by the treatments. On the contrary, the expression of P-glycoprotein (P-gp) was decreased by the treatment, more greatly by PC than by LC, suggesting that increases in the bioavailability of LY by LC and PC are associated with the decreased expression of P-gp in jejunum. The increase in the bioavailability was also observed for colon by the treatment of LC, but not that of PC. LC decreased the expression of claudin-4 protein, whereas PC decreased the expression of P-gp in colon. Therefore, LC and PC appear to have different impact on the intestinal transporters depending on the site (i.e., jejunum and colon).

Dietary fish oil regulates gene expression of cholesterol and bile acid transporters in mice

Fish oil rich in n-3 polyunsaturated fatty acids is known to affect hepatic lipid metabolism. Several studies have demonstrated that fish oil may affect the bile acid metabolism as well as lipid metabolism, whereas only scarce data are available. The aim of this study was to investigate the effect of fish oil on the gene expression of the transporters and enzymes related to bile acid as well as lipid metabolism in the liver and small intestine. Seven-week old male C57BL/6 mice were fed diets enriched in 10% soybean oil or 10% fish oil for 4 weeks. After 4 weeks, blood, liver and small intestine were obtained. Hepatic mRNA expression of lipids (Abcg5/8, multidrug resistance gene product 2) and bile acids transporters (bile salt export pump, multidrug resistance associated protein 2 and 3, organic solute transporter α) was induced in fish oil-fed mice. Hepatic Cyp8b1, Cyp27a1 and bile acid CoA : amino acid N-acyltransferase were increased in fish oil-fed mice compared with soybean-oil fed mice. Besides, intestinal cholesterol (Abcg5/8) and bile acid transporters (multidrug resistance associated protein 2 and organic solute transporter α) were induced in fish oil-fed mice. Fish oil induced the expression of cholesterol and bile acid transporters not only in liver but in intestine. The upregulation of Abcg5/g8 by fish oil is caused by an increase in cellular 27-HOC through Cyp27a1 induction. The hepatic induction of bile acid synthesis through Cyp27a1 may upregulate expression of bile acid transporters in both organs.

Calcium Channel Blocker Verapamil Enhances Reticulum Stress and Death Induced by Proteasome Inhibition in Myeloma Cells

The proteasome inhibitor bortezomib is clinically approved for the treatment of multiple myeloma. However, long-term remissions are difficult to achieve, and myeloma cells often develop secondary resistance to proteasome inhibitors. We recently demonstrated that the extraordinary sensitivity of myeloma cells toward bortezomib is dependent on their extensive immunoglobulin synthesis, thereby triggering the terminal unfolded protein response (UPR). Here, we investigated whether verapamil, an inhibitor of the multidrug resistance (MDR) gene product, can enhance the cytotoxicity of bortezomib. The combination of bortezomib and verapamil synergistically decreased the viability of myeloma cells by inducing cell death. Importantly, bortezomib-mediated activation of major UPR components was enhanced byverapamil. The combination of bortezomib and verapamil resulted in caspase activation followed by poly(ADP-ribose) polymerase cleavage, whereas nuclear factor κB (NF-κB) activity declined in myeloma cells. Also, we found reduced immunoglobulin G secretion along with increased amounts of ubiquitinylated proteins within insoluble fractions of myeloma cells when using the combination treatment. Verapamil markedly induced reactive oxygen species production and autophagiclike processes. Furthermore, verapamil decreased MDR1 expression. We conclude that verapamil increased the antimyeloma effect of bortezomib by enhancing ER stress signals along with NF-κB inhibition, leading to cell death. Thus, the combination of bortezomib with verapamil may improve the efficacy of proteasome inhibitory therapy.

Association of the colorectal cancer and MDR1 gene polymorphism in an Iranian population

The human multidrug resistance (MDR1) gene product P-glycoprotein is highly expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics, bacterial toxins, drugs and other biologically active compounds, possibly carcinogens. In this study, an association of MDR1 gene polymorphism and the occurrence of colorectal cancer were evaluated. In this case-control-designed 118 unrelated colorectal cancer and 137 sex-and-ages matched healthy controls were enrolled. The C3435T MDR1 gene polymorphism was identified using the polymerase chain reaction-restriction fragment length polymorphism method. Significantly increased frequencies of the 3435T allele and the 3435TT were observed in patients with colorectal cancer compared with controls (P = 0.03; OR, 95% CI; 1.46 for 3435T allele and P = 0.003; OR, 95% CI; 2.2 for 3435TT genotype). In contrast, frequency of genotype TT was significantly higher in controls compared to colorectal cancer (P = 0.006; OR, 95% CI; 0.49 for TC genotype). In this study suggest that C3435T MDR1 polymorphism has an association with colorectal cancer. The results support that the presence of allele C results in decreased susceptibility to colorectal cancer.

Hereditäre Defekte hepatobiliärer Transportproteine

Defects in transport proteins that are expressed at the hepatocyte canalicular membrane can cause severe impairment of hepatobiliary transport processes. Progressive familial intrahepatic cholestasis (PFIC) typically manifests in early childhood. Genetic variants in the aminophospholipid transporter FIC1 (ATP8B1 gene) cause PFIC1, characterized by elevated serum bile acids but normal or only mildly elevated gamma-GT levels. Benign recurrent intrahepatic cholestasis type 1 (BRIC1) is also caused by ATP8B1 mutations. Defects in the function of the bile salt efflux pump (BSEP; ABCB11) cause PFIC2 or BRIC2, depending on the degree of BSEP impairment. A common BSEP variant, the V444A polymorphism, is commonly found in various types of cholestatic liver injury, including drug-induced liver injury. Finally, dysfunction of the multidrug resistance gene product MDR3 (ABCB4) leads to PFIC3, characterized by low biliary phospholipids and high gamma-GT levels in serum due to bile duct injury. All three transporter genes are also associated with intrahepatic cholestasis of pregnancy. Treatment options include ursodeoxycholic acid for milder forms and liver transplantation for severe pediatric cases.

The Effects of Tamoxifen on Immunity

Tamoxifen is a widely known anti-estrogen which has been employed in adjuvant treatment of early-stage, estrogen-sensitive breast cancer for over 20 years. Less well known are the effects of tamoxifen on immune function, which we discuss here. We review the growing body of evidence which demonstrates immunomodulatory effects of tamoxifen, including in vitro and in vivo studies as well as observations made in breast cancer patients treated with tamoxifen. Taken together these studies suggest that tamoxifen is capable of inducing a shift from cellular (T-helper 1) to humoral (T-helper 2) immunity. Interestingly, the immunomodulatory effects of tamoxifen appear to be independent of the estrogen-receptor and may be mediated through the multidrug resistance gene product, Permeability-glycoprotein, for which a role in immunity has recently emerged. We furthermore discuss the clinical implications of the immunomodulatory effects of tamoxifen which are twofold. First, tamoxifen may be useful in the treatment of immune-mediated disorders, particularly of those arising from aberrant T-helper 1 cell activity, including allograft rejection, Crohn's disease, and Th1-mediated autoimmune conditions such as diabetes mellitus, scleroderma, and multiple sclerosis. Second, given that cellular T-helper 1 immunity is targeted against cancer cells, the tamoxifen-induced shift away from cellular immunity represents a significant step in fostering a cancerogenic environment. This may limit the anti-cancer effects of tamoxifen and thus explain why tamoxifen is inferior compared to other anti-estrogens in preventing disease recurrence in early-stage breast tumors.

An immunochemical analysis of multidrug resistance gene product P170 glycoprotein in human breast cancer tissues

e22206 Background: P-glycoprotein (gp170; encoded by the MDR1 gene (also known as PGY1) is a membrane protein capable of exporting a variety of anticancer drugs from cells. MDR1/gp170 expression has been studied in breast cancer, but the prevalence of this expression and its role in breast tumour drug resistance are unclear. To offer more effective and less toxic treatment, selecting therapies requires considering the patient and the clinical and molecular characteristics of the tumour. Our primary goal was to clarify the prevalence and clinical relevance of MDR1/gp170 expression in breast cancer patients in correlation with clinocopathologic features. Methods: In this study the expression of MDR1/gp170 protein has been investigated in a series of 40 human breast carcinomas. The immunoperoxidase antigen detection protocol, was employed using anti-p170 monoclonal antibodies (MoABs), (JSB 1 Monosan). Clinicopathologic findings, grade, and molecular markers (HER2, estrogen receptor (ER)alpha, ER beta, and progesterone receptor were also analyzed. Results: MoAB JSB-1 reacted strongly with the transmembranic antigen epitope. The proportion of breast tumours expressing MDR1/gp170 was 22% in Grade 1, 71% and 45.4% in Grade2 and Grade3 Itumors. There was no correlation with hormone receptor status, lymph node status and ΕΕR-2. Conclusions: The data of MDR-1 product expression by immunohistochemistry in breast cancer might suggest that an overexpression of this protein could constitute a hallmark of potential more aggressive phenotype for this type of neoplasia and a rapid method for pre-screening tumours for a constitutive multidrug resistance in order to orientate the cancer treatment. While the functional relevance of this expression remains to be established, it seems likely that MDR1/gp170 is an independent prognostic factor in breast tumours. No significant financial relationships to disclose.

0043 Expression of a multidrug resistance gene product p170 glycoprotein in neoplastic breast tissues

0043 Expression of a multidrug resistance gene product p170 glycoprotein in neoplastic breast tissues

Clinical significance of the expression of multidrug resistance gene products in colorectal carcinoma

Clinical significance of the expression of multidrug resistance gene products in colorectal carcinoma