1 Institute of Cancer Research, and Departments of 2 Surgery and 3 Clinical Pathology, University of Vienna, A-1090 Vienna, Austria
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Lung resistance-related protein (LRP) plays an important role in chemoresistance of tumor cells probably by altering nuclear-cytoplasmic transport processes. We analyzed the association between LRP expression and hepatocarcinogenesis in humans and rats by RT-PCR, immunoblotting, and immunohistochemistry. LRP was found in hepatocytes and bile epithelia of normal human and rat liver showing distinct interindividual variations. In human tissues, the LRP expression levels of dysplastic liver nodules, hepatocellular adenomas, and carcinomas were highly variable, including decreased but also distinctly increased staining intensities. Mean expression levels, however, were comparable to the surrounding tissue. Considerable levels of LRP mRNA and protein were also found in human hepatoma cell lines. To study LRP expression from the beginning of hepatocarcinogenesis onward, rats were subjected to a tumor initiation/promotion protocol leading to preneoplastic hepatocytes present as single cells or multicellular clones, followed by adenoma and carcinoma. All of the (pre)neoplastic rat liver lesions expressed, comparable to the surrounding tissue, considerable amounts of LRP. We conclude that LRP might be one mechanism involved in the intrinsically high but variable chemoresistance of normal and (pre)neoplastic hepatocytes.
vault particle; chemoresistance; human liver; hepatocellular carcinoma
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
LIVER CANCER IS AMONG THE seven leading causes of cancer deaths worldwide. Prognosis is usually poor, and no effective chemotherapeutic treatment is presently available (4, 15). One explanation may be that the major function of the liver is to process and detoxify numerous structurally diverse compounds (40). Drug metabolites are extruded from the hepatocytes by specific membrane proteins such as the multispecific organic anion transporters that comprise members of the multidrug resistance protein family (MRP), the bile acid transporter, ion-motive ATPases, and P-glycoprotein (21, 25). These transporters contribute to the broad chemoresistance of hepatocytes known as intrinsic multidrug resistance (MDR). The liver, like several other tissues, preserves protection mechanisms during malignant progression resulting in intrinsically drug-resistant tumors (12).
Additionally, to a protective function, MDR might also play a role in hepatocarcinogenesis. (Pre)malignant hepatocytes have been shown to acquire further resistance to cytotoxic agents by activation of P-glycoprotein and phase II detoxifying enzymes, including the placentar glutathione-S-transferase (GSTp) (10, 30, 35, 38). This might provide a selection advantage to the (pre)neoplastic hepatocytes in a toxic environment and thus drive the further development to malignant tumors (11, 32, 35, 37, 41).
A newly identified protein, called lung resistance-related protein (LRP) due to its discovery in a drug-resistant lung cancer cell line, has been associated with cellular chemoresistance (36). LRP, also known as major vault protein, is the main structural component of vaults, the largest ribonucleoprotein particles known so far. Besides multiple copies of LRP (100 kDa), the vault complex is composed of two proteins (p240 and p193) and an untranslated RNA (vRNA) molecule. The two larger protein components were identified as telomerase-associated protein-1 and as a new poly-ADP-ribose-polymerase (vault PARP) (22, 23). Vaults have been detected originally in preparations of coated vesicles from rat liver (20). The importance of LRP in detoxification processes is substantiated by the fact that it is highly expressed in epithelia potentially exposed to toxins (17). Scheffer et al. (36) and Berger et al. (2, 3) have shown a distinct correlation of LRP expression with chemoresistance against diverse antineoplastic drugs including platinum agents in various cancer cell lines derived from lung cancer, gliomas, and other tumors. Furthermore, a distinct LRP expression was found also in highly chemoresistant soft tissue leiomyosarcomas and malignant gastrointestinal stromal tumors (33). In several malignancies, LRP expression has predictive value for poor response to chemotherapy (36). LRP induction in colon cancer cells by sodium butyrate reduced nuclear accumulation of the anticancer drug doxorubicin (24). These results corroborate the hypothesis that vaults are involved in nucleocytoplasm transport (7).
The possible role of LRP for intrinsic or acquired MDR of hepatocytes and their (pre)malignant counterparts has not been extensively investigated so far. Two studies gave conflicting results about the expression and possible function of LRP in normal hepatocytes (17, 39). We therefore studied the extent of LRP expression in human and rat hepatocarcinogenesis. In both species we observed considerable levels of LRP in unaltered liver and all steps of liver (pre)neoplasia. Thus LRP vaults might be one factor contributing to the high intrinsic chemoresistance of liver tumor.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Animals and treatment. Male SPF Wistar rats, 3 wk old, were obtained from the Forschungsinstitut für Versuchstierzucht und Versuchstierhaltung (Himberg, Austria). Animals were kept under standardized conditions and were treated as described (26). Briefly, N-nitrosomorpholine (NNM; Sigma, St. Louis, MO), dissolved in PBS (pH 7.4), was given as a single dose of 250 mg NNM/10 ml solution/kg body wt by gavage. After a recovery period of 4 days, animals were treated with phenobarbital (Fluka, Buchs, Switzerland), which was admixed to the diet (Altromin 1321N; Altromin, Lage, Germany) at a daily dose of 50 mg/kg body wt. Controls received basal diet ad libitum. Animals were killed by decapitation under CO2 asphyxia. Time points of death were 91 and 266 days post-NNM treatment (for details see Ref. 26). The experiment was performed according to Austrian guidelines for animal care and protection.
Human liver samples.
Patients suffering from cirrhosis (n = 13) or
cholangiocellular carcinoma (n = 2) were subjected to
liver transplantation. Patients with dysplastic liver nodules
(n = 13), hepatocellular adenoma (n = 5), or carcinoma (n = 20) underwent liver surgery. Chemotherapy had not been applied before surgery. For causative factors
for the development of the lesions and diagnoses see Table 1. The classification of benign and
malignant liver lesions followed the International Working Party
(16) as well as Edmondson and Steiner (9),
respectively. Tissue samples were immediately fixed in 10% buffered
formaldehyde; additional samples were stored in liquid nitrogen.
|
Cell culture. Human hepatoma cell lines HepG2 (HB-8065), Hep2B2.1-7 (HB-8064), Chang liver (CCl-13) and WRL 68 (CL-48), obtained from the American Type Culture Collection (Manassas, VA), were maintained in vitro as described (13). The small-cell lung cancer cell line GLC-4 and its drug-resistant LRP-overexpressing subline GLC-4/ADR (42) were a gift of Dr. E. G. E. de Vries, University of Groningen, The Netherlands.
RT-PCR. RNA was extracted from cell lines and RT-PCR was performed as described previously (3). Two oligonucleotide primer sets were used: set I resulted in the amplification of a 284 bp PCR product specific for human LRP (GenBank accession no. X79882); primer set II specific for GAPDH (358 bp) was used as a housekeeping gene (3). Amplification products were separated by acrylamide gel electrophoresis and were stained with ethidium bromide. Dynamics of PCR amplification, as measured by ethidium bromide staining, was evaluated for both genes and revealed an optimum of 20 cycles for GAPDH and 28 cycles for LRP.
Immunoblotting.
Tissue samples or hepatoma cells were suspended in lysis puffer (50 mM
Tris, 300 mM NaCl, 0.5% Triton X at pH 7.6, containing several
protease inhibitors and PMSF) for 10 min at 4°C, frozen and thawed
three times, and centrifuged at 5,000 rpm for 15 min at 4°C.
Supernatant was separated by SDS-PAGE and transferred, detected, and
quantified using the Gel-Doc System from Bio-Rad (Munich, Germany) as
described (3). Primary antibodies (anti-LRP mouse
monoclonal antibody from Transduction Laboratories, Lexington, KY;
anti--actin, clone AC-15 from Sigma) were applied at a working dilution of 1:1,000.
Histology. Specimens of human liver, fixed in 4% buffered formaldehyde and rat liver tissue, fixed in Carnoy's solution, were processed as described (14). Serial sections were cut and stained with hematoxylin and eosin and for LRP. For rat samples, an additional section was stained for GSTp.
Immunostaining for LRP and GSTp. Primary antisera of mouse (LRP-56) or rat (LMR5) monoclonal antibodies raised against LRP (both Alexis Biochemicals, San Diego, CA) and rabbit polyclonal IgGs raised against rat Yp-subunit of GSTp (Biotrin International, Dublin, Ireland). Pretreatment and staining of tissue was described by Grasl-Kraupp et al. (14). Primary antibodies, diluted in BSA-TBS (2.5% BSA in 0.05 M Tris, 0.3 M NaCl, pH 7.6) (LRP-56 and LMR5: 1:10; Yp: 1:5,000), were applied overnight at 4°C. Secondary antibodies, diluted in BSA-TBS (biotinylated goat-anti-mouse IgG 1:200; biotinylated rabbit-anti-rat IgG 1:300; biotinylated goat-anti-rabbit 1:600; all from Dakopatts, Glostrup, Denmark) were used for 90 min at RT. Incubation with peroxidase-labeled streptavidin (1:300 in TBS, 45 min RT; Dakopatts) and diaminobenzidine (Sigma) was used for color development. Specificity of immunohistochemistry was confirmed by omitting the primary antibodies.
Quantitative evaluation of GSTp-positive foci. Preneoplastic rat liver foci were first identified in the GSTp-stained serial section and were then evaluated in the LRP-stained serial section (see Semiquantitative evaluation of immunoreactions) using two microscopes linked by a bridge for overprojection (Zeiss, Germany). Wherever indicated, we also determined the number of component cells per cross section of individual GSTp+ foci.
Semiquantitative evaluation of immunoreactions. LRP staining of each lesion was compared with the surrounding tissue showing mostly uniform staining. At least 1,000 cells in 5 different areas of lesions and their surroundings were evaluated. Intensity of staining within a lesion was categorized on an arbitrary scale of 0 to 2, where 0 = negative staining; 0.3 and 0.7 = weaker than surrounding tissue; 1 = equal to surrounding tissue; and 1.3, 1.7, and 2 = stronger than surrounding tissue. The extent of staining was estimated by the percentage of cells of a certain staining intensity. Intensity and extent of staining served to calculate the degree of LRP expression, e.g., 30% of the cells were grouped into staining category 0.3 and 70% of the cells into category 1 (0.3 × 0.3 = 0.09; 0.7 × 1 = 0.7; 0.09 + 0.7 = 0.79); the degree of staining was calculated to be 0.79, i.e., 79%, of the surrounding tissue.
Densitometrical analysis of immunoreactions.
Tumor and surrounding tissue were analyzed within the same section. The
microscope image (×40 objective; Olympus BH series) was detected by a
JVC color-video camera (type 3CCD) and transferred to the image
processor Lucia G/4.00 (Lucia, Prague; details:
http://www.lim.cz/). The digitized picture, corrected for
nonhomogeneous illumination, was transformed to an image of 768 × 512 pixels with a 16-bit gray resolution and possible gray values of
0-255 for each pixel. Transmission refers to the gray value
spectrum and expresses the light intensity measured. The optical
density (OD) is defined as the negative logarithm (base 10) of the
transmission. For each measurement, two points for OD-calibration were
chosen (the lightest and darkest point in the sample), whereby gray
value 0 means OD 10 and a gray value of 255 means OD 0. OD is evaluated
according to the following formula (-coefficient of the camera of
0.45 is included): OD =
log (pixelgray value + 0.5)/62.5.
Statistics. The significance of differences of means was calculated by Kruskal-Wallis or the Wilcoxon tests.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
LRP expression in nontumorous liver of humans and rats.
In immunostained sections of human and rat liver, LRP was found
exclusively in the cytoplasm of hepatocytes and bile epithelia, corresponding to the location of LRP in the cytoplasmic vesicle fraction (Fig. 1,
A-C). The staining intensity was most
prominent in the perivenous zone of the liver lobule and decreased
toward the periportal zone (Fig. 1A). Occasionally, single
hepatocytes with strong LRP expression were scattered throughout the
lobule (Fig. 1B). Immunostaining with two different
antibodies against LRP gave identical results as demonstrated in the
case of rat liver carcinoma (Fig. 1, H and
I).
|
|
Expression of LRP-mRNA in human hepatoma cell lines.
By RT-PCR, mRNA of LRP was detectable in all human hepatoma cells
tested showing marginal differences among the cell lines (Fig.
3A). Also, LRP protein was
present in all cell lines. The protein concentration was highest in
CCL-13 cells and lowest in Hep-G2 cells (Fig. 3B).
|
Expression of LRP in human benign and malignant hepatocellular
tumors.
All cases of benign and malignant hepatocellular tumors studied
displayed a positive immunoreaction for LRP in pre(malignant) cells.
Like in normal liver, LRP was found exclusively in the cytoplasm (Fig.
1, F and G). LRP-stained tissue sections were evaluated by both semiquantitative scoring and densitometry. Data obtained with the two methods correlated significantly (Fig.
4; Pearson's test:
r2 = 0.7127; P < 0.0001).
In Fig. 5 data from the densitometric evaluation are shown. Generally, adenomas and grade 1 carcinomas tended
to an enhanced, low grade dysplastic nodules and grade 2 carcinomas to
a decreased LRP expression compared with the surrounding tissue. High
grade dysplastic nodules and carcinomas grade 3 tended to decreased but
also intensely increase immunoreactions (Figs. 1G and 5).
The mean expression levels of both premalignant and malignant tissues
did, however, not differ significantly from the surrounding tissue.
|
|
Expression of LRP in GSTp+ preneoplasia,
hepatocellular adenoma, and carcinoma of the rat.
Details on the model system used for studying
hepatocarcinogenesis in the rat were published elsewhere
(26). GSTp staining was used to detect all stages of
hepatocarcinogenesis ranging from initiated single cells, multicellular
foci (Fig. 1, D and E), hepatocellular adenoma,
and finally, to carcinoma (Fig. 1, H and I).
Similar to the human situation, LRP was expressed in all (pre)malignant
stages of the rat liver analyzed. Immunostaining with two
different antibodies against LRP gave identical results. As one
example, serial sections of a rat liver carcinoma stained with the two
anti-LRP antibodies are shown (Fig. 1, H and I). Expression levels did not vary significantly between
(pre)malignant lesions and the adjacent tissue (Fig.
6).
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Expression of LRP, the major vault protein, was studied in unaltered and (pre)malignant hepatocytes, which are known for their intrinsic and acquired chemoresistance toward a great variety of cytotoxic agents. We found considerable expression of LRP in hepatocytes and bile duct epithelia in almost all liver samples studied. To this end, two papers reported somewhat conflicting results on the occurrence of LRP in human liver. Whereas a low expression of LRP in hepatocytes and a higher one in bile epithelia was reported (17), others (39) failed to detect LRP in the liver. Vaults were originally discovered in extracts from rat liver (20). Primary cultures of human hepatocytes treated with the hepatomitogens epidermal growth factor or hepatocyte growth factor stably expressed significant amounts of LRP mRNA. At the protein level, LRP-expression even tended to increase within 33 days of culture (34). These data suggest an inherent and pronounced expression of vaults in human hepatocytes, which may relate to the specific function of this organ for activation, metabolism, and excretion of xenobiotics and endogenous toxins.
In human and rat liver, we observed the highest LRP-expression in hepatocytes in the perivenous zone of the liver acinus. This contrasts to the intrahepatic distribution of P-glycoprotein being highest in the periportal and lowest in the perivenous zone and suggests different functions of these two protection proteins in normal liver (38). Periportal and perivenous hepatocytes differ in their biochemical capacity, reflecting different functions in normal liver physiology. Metabolic activities like utilization of glucose and amino acids as well as the synthesis of urea, cholesterol, and bile localize preferentially to the periportal area, whereas synthesis of glycogen, fatty acids, and glutamine, and xenobiotic metabolism predominate in the perivenous area (18). Thus vaults may fulfill a defined physiological function in the liver mainly executed by the hepatocytes within the perivenous area.
A distinct interindividual heterogeneity in the LRP level in liver tissues was detectable. This may be due to an inherent, genetically determined LRP expression pattern, as shown for many genes involved in chemoresistance and metabolism of xenobiotics and that often underlies the different interindividual sensitivities of humans against carcinogens and toxins (29). On the other side, many of the metabolic functions of the liver may be readily induced, e.g., on functional load, drug metabolism increases its capacity dramatically (40). Likewise, LRP expression in lung tumor cell lines (3) and 1 of 3 human hepatoblastoma xenocrafts (1) was upregulated by exposure to cytotoxic drugs and to benzo-a-pyrene, a genotoxic carcinogen occurring in tobacco smoke and smoked food products (6). Accordingly, the heterogeneity observed in our mainly cirrhotic, nonmalignant liver samples may also be based on exogeneous or endogeneous toxins, such as ethanol or accumulation of inflammatory intermediates. However, it appears to be independent of cirrhosis, because the two samples almost lacking LRP were also derived from patients suffering from cirrhosis due to ethanol abuse and Byler's disease, respectively. It will be interesting to investigate whether the interindividual differences in the LRP expression level in human liver are more or less constant or are changeable by the administration of various cytotoxic and noncytotoxic xenobiotics.
Intrinsic and acquired forms of MDR may underlie the limited success obtained by chemotherapeutic treatments against different types of malignant tumors including liver cancer (15, 33). Accordingly, in experimental hepatocarcinogenesis, MDR plays a key role in the development of tumors. In addition to the intrinsic chemoresistance of normal hepatocytes, (pre) malignant liver cells acquire further resistance to the cytotoxic/cytocidal effects of various hepatotoxins and hepatocarcinogens, e.g., acetylaminofluorene, nitrosamines, and aflatoxin B1 (11, 37). This resistance provides a selection advantage in a toxic environment, i.e., proliferation of normal hepatocytes is suppressed, whereas resistant cells in (pre)neoplasia multiply. As a result, tumor promotion and finally malignant progression may be accelerated. The biochemical basis for this phenomenon is an increase of metabolic pathways favoring inactivation and extrusion of toxic compounds, e.g., conjugation reactions by the GSTp and other GSH-transferases, or membrane transport by P-glycoprotein and MRP-family members (5, 8, 10, 11, 19, 31, 32, 37). Also, in humans, resistance to cytotoxins seems to be important for hepatocarcinogenesis. These toxins may stem from exogenous (ethanol, aflatoxin B1) and/or endogenous sources (enterotoxins, excessive storage of metabolic by-products, inflammatory by-products) (4). Our data suggest that LRP is not involved in the acquired forms of chemoresistance in hepatocarcinogenesis, because LRP expression was not generally upregulated in liver (pre)neoplasia. The variable expression of LRP in liver carcinomas may reflect the genetic instability within the tumor, rather than activation of a distinct program. Nevertheless, the level of LRP was high in most of the tumors, which is the first evidence that LRP may be involved in MDR of liver cancer, as observed in the clinical situation. Because LRP was inducible in one of three adriamycin-treated human hepatoblastoma xenocrafts (1) and in lung cancer cell lines (2), it appears likely that LRP is induced in (pre)malignant liver tissue by the administration of chemotherapeutic drugs. Data on the regulation of LRP in liver tissue might clarify the still enigmatic role of vaults in normal and tumor cell physiology.
In conclusion, our data derived from human and rat tissues demonstrate that LRP is expressed in normal and (pre)malignant hepatocytes. This suggests a possible function of LRP in the basal chemoprotection of benign and malignant liver tissue.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank Helga Koudelka and Juliana Krejsa for excellent technical assistance.
![]() |
FOOTNOTES |
---|
The present study was supported by the Herzfelder'sche Familienstiftung and by the Jubiläumsfonds der Österreichischen Nationalbank, Project No. 8817.
Address for reprint requests and other correspondence: W. Berger, Institute of Cancer Research, Div. of Applied and Exp. Oncology, Borschkegasse 8a, A-1090 Vienna, Austria (E-mail: walter.berger{at}univie.ac.at).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
July 25, 2002;10.1152/ajpgi.00195.2002
Received 22 May 2002; accepted in final form 21 July 2002.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Bader, P,
Fuchs J,
Wenderoth M,
von Schweinitz D,
Niethammer D,
and
Beck JF.
Altered expression of resistance associated genes in hepatoblastoma xenografts incorporated into mice following treatment with adriamycin or cisplatin.
Anticancer Res
18:
3127-3132,
1998[ISI][Medline].
2.
Berger, W,
Elbling L,
and
Micksche M.
Expression of the major vault protein LRP in human non-small-cell lung cancer cells: activation by short-term exposure to antineoplastic drugs.
Int J Cancer
88:
293-300,
2000[ISI][Medline].
3.
Berger, W,
Spiegl-Kreinecker S,
Buchroithner J,
Elbling L,
Pirker C,
Fischer J,
and
Micksche M.
Overexpression of the human major vault protein in astrocytic brain tumor cells.
Int J Cancer
94:
377-382,
2001[ISI][Medline].
4.
Bosch, FX,
Ribes J,
and
Borras J.
Epidemiology of primary liver cancer.
Semin Liver Dis
19:
271-285,
1999[ISI][Medline].
5.
Bradley, G,
Sharma R,
Rajalakshmi S,
and
Ling V.
P-glycoprotein expression during tumor progression in the rat liver.
Cancer Res
52:
5154-5161,
1992[Abstract].
6.
Cheng, SH,
Lam W,
Lee AS,
Fung KP,
Wu RS,
and
Fong WF.
Low-level doxorubicin resistance in benzo[a]pyrene-treated KB-3-1 cells is associated with increased LRP expression and altered subcellular drug distribution.
Toxicol Appl Pharmacol
164:
134-142,
2000[ISI][Medline].
7.
Chugani, DC,
Rome LH,
and
Kedersha NL.
Evidence that vault ribonucleoprotein particles localize to the nuclear pore complex.
J Cell Sci
106:
23-29,
1993
8.
Courtois, A,
Payen L,
Guillouzo A,
and
Fardel O.
Up-regulation of multidrug resistance-associated protein 2 (MRP2) expression in rat hepatocytes by dexamethasone.
FEBS Lett
459:
381-385,
1999[ISI][Medline].
9.
Edmondson, HA,
and
Steiner PE.
Primary carcinoma of the liver: a study of 100 cases among 48,000 necropsies.
Cancer
7:
462-503,
1954[ISI][Medline].
10.
Fairchild, CR,
Ivy SP,
Rushmore T,
Lee G,
Koo P,
Goldsmith ME,
Myers CE,
Farber E,
and
Cowan KH.
Carcinogen-induced mdr overexpression is associated with xenobiotic resistance in rat preneoplastic liver nodules and hepatocellular carcinomas.
Proc Natl Acad Sci USA
84:
7701-7705,
1987[Abstract].
11.
Farber, E,
and
Cameron R.
The sequential analysis of cancer development.
Adv Cancer Res
31:
125-226,
1980[Medline].
12.
Goldstein, LJ,
Galski H,
Fojo A,
Willingham M,
Lai SL,
Gazdar A,
Pirker R,
Green A,
Crist W,
Brodeur GM,
Lieber M,
Cossman J,
Gottesman MM,
and
Pastan I.
Expression of a multidrug resistance gene in human cancers.
J Natl Cancer Inst
81:
116-124,
1989[Abstract].
13.
Grasl-Kraupp, B,
Rossmanith W,
Ruttkay-Nedecky B,
Mullauer L,
Kammerer B,
Bursch W,
and
Schulte-Hermann R.
Levels of transforming growth factor beta and transforming growth factor beta receptors in rat liver during growth, regression by apoptosis and neoplasia.
Hepatology
28:
717-726,
1998[ISI][Medline].
14.
Grasl-Kraupp, B,
Waldhor T,
Huber W,
and
Schulte-Hermann R.
Glutathione S-transferase isoenzyme patterns in different subtypes of enzyme-altered rat liver foci treated with the peroxisome proliferator nafenopin or with phenobarbital.
Carcinogenesis
14:
2407-2412,
1993[Abstract].
15.
Hussain, SA,
Ferry DR,
El-Gazzaz G,
Mirza DF,
James ND,
McMaster P,
and
Kerr DJ.
Hepatocellular carcinoma.
Ann Oncol
12:
161-172,
2001[Abstract].
16.
International Working Party.
Terminology of nodular hepatocellular lesions.
Hepatology
22:
983-993,
1995[Medline].
17.
Izquierdo, MA,
Scheffer GL,
Flens MJ,
Giaccone G,
Broxterman HJ,
Meijer CJ,
van der Valk P,
and
Scheper RJ.
Broad distribution of the multidrug resistance-related vault lung resistance protein in normal human tissues and tumors.
Am J Pathol
148:
877-887,
1996[Abstract].
18.
Jungermann, K,
and
Kietzmann T.
Oxygen: modulator of metabolic zonation and disease of the liver.
Hepatology
31:
255-260,
2000[ISI][Medline].
19.
Kauffmann, HM,
Keppler D,
Kartenbeck J,
and
Schrenk D.
Induction of cMrp/cMoat gene expression by cisplatin, 2- acetylaminofluorene, or cycloheximide in rat hepatocytes.
Hepatology
26:
980-985,
1997[ISI][Medline].
20.
Kedersha, NL,
and
Rome LH.
Isolation and characterization of a novel ribonucleoprotein particle: large structures contain a single species of small RNA.
J Cell Biol
103:
699-709,
1986[Abstract].
21.
Keppler, D,
and
Arias IM.
Hepatic canalicular membrane. Introduction: transport across the hepatocyte canalicular membrane.
FASEB J
11:
15-18,
1997
22.
Kickhoefer, VA,
Siva AC,
Kedersha NL,
Inman EM,
Ruland C,
Streuli M,
and
Rome LH.
The 193-kD vault protein, VPARP, is a novel poly(ADP-ribose) polymerase.
J Cell Biol
146:
917-928,
1999
23.
Kickhoefer, VA,
Stephen AG,
Harrington L,
Robinson MO,
and
Rome LH.
Vaults and telomerase share a common subunit, TEP1.
J Biol Chem
274:
32712-32717,
1999
24.
Kitazono, M,
Sumizawa T,
Takebayashi Y,
Chen ZS,
Furukawa T,
Nagayama S,
Tani A,
Takao S,
Aikou T,
and
Akiyama S.
Multidrug resistance and the lung resistance-related protein in human colon carcinoma SW-620 cells.
J Natl Cancer Inst
91:
1647-1653,
1999
25.
Koepsell, H.
Organic cation transporters in intestine, kidney, liver, and brain.
Annu Rev Physiol
60:
243-266,
1998[ISI][Medline].
26.
Low-Baselli, A,
Huber WW,
Kafer M,
Bukowska K,
Schulte-Hermann R,
and
Grasl-Kraupp B.
Failure to demonstrate chemoprevention by the monoterpene perillyl alcohol during early rat hepatocarcinogenesis: a cautionary note.
Carcinogenesis
21:
1869-1877,
2000
27.
Lucia, M, (Lucia G)
Function Reference. Prague, Czechoslovakia: Laboratory Imaging, 1995.
28.
Lucia, M, (Lucia G)
User's Guide. Prague, Czechoslovakia: Laboratory Imaging, 1995.
29.
Meyer, UA,
and
Zanger UM.
Molecular mechanisms of genetic polymorphisms of drug metabolism.
Annu Rev Pharmacol Toxicol
37:
269-296,
1997[ISI][Medline].
30.
Nakatsukasa, H,
Silverman JA,
Gant TW,
Evarts RP,
and
Thorgeirsson SS.
Expression of multidrug resistance genes in rat liver during regeneration and after carbon tetrachloride intoxication.
Hepatology
18:
1202-1207,
1993[ISI][Medline].
31.
Payen, L,
Courtois A,
Vernhet L,
Guillouzo A,
and
Fardel O.
The multidrug resistance-associated protein (MRP) is over-expressed and functional in rat hepatoma cells.
Int J Cancer
81:
479-485,
1999[ISI][Medline].
32.
Pitot, HC.
Altered hepatic foci: their role in murine hepatocarcinogenesis.
Annu Rev Pharmacol Toxicol
30:
465-500,
1990[ISI][Medline].
33.
Plaat, BE,
Hollema H,
Molenaar WM,
Torn Broers GH,
Pijpe J,
Mastik MF,
Hoekstra HJ,
van den Berg E,
Scheper RJ,
and
van der Graaf WT.
Soft tissue leiomyosarcomas and malignant gastrointestinal stromal tumors: differences in clinical outcome and expression of multidrug resistance proteins.
J Clin Oncol
18:
3211-3220,
2000
34.
Runge, D,
Kohler C,
Kostrubsky VE,
Jager D,
Lehmann T,
Runge DM,
May U,
Stolz DB,
Strom SC,
Fleig WE,
and
Michalopoulos GK.
Induction of cytochrome P450 (CYP)1A1, CYP1A2, and CYP3A4 but not of CYP2C9, CYP2C19, multidrug resistance (MDR-1) and multidrug resistance associated protein (MRP-1) by prototypical inducers in human hepatocytes.
Biochem Biophys Res Commun
273:
333-341,
2000[ISI][Medline].
35.
Satoh, K,
Kitahara A,
Soma Y,
Inaba Y,
Hatayama I,
and
Sato K.
Purification, induction, and distribution of placental glutathione transferase: a new marker enzyme for preneoplastic cells in the rat chemical hepatocarcinogenesis.
Proc Natl Acad Sci USA
82:
3964-3968,
1985[Abstract].
36.
Scheffer, GL,
Schroeijers AB,
Izquierdo MA,
Wiemer EA,
and
Scheper RJ.
Lung resistance-related protein/major vault protein and vaults in multidrug-resistant cancer.
Curr Opin Oncol
12:
550-556,
2000[ISI][Medline].
37.
Schulte-Hermann, R.
Tumor promotion in the liver.
Arch Toxicol
57:
147-158,
1985[ISI][Medline].
38.
Silverman, JA,
and
Thorgeirsson SS.
Regulation and function of the multidrug resistance genes in liver.
Prog Liver Dis
13:
101-123,
1995[Medline].
39.
Sugawara, I,
Akiyama S,
Scheper RJ,
and
Itoyama S.
Lung resistance protein (LRP) expression in human normal tissues in comparison with that of MDR1 and MRP.
Cancer Lett
112:
23-31,
1997[ISI][Medline].
40.
Vessey, DA.
Metabolism of xenobiotics, 1996.
In: Hepatology. A Textbook of Liver Disease, edited by Zakim D,
and Boyler TD.. Philadelphia, PA: Saunders, 1996, p. 257-306.
41.
Yusuf, A,
Rao PM,
Rajalakshmi S,
and
Sarma DS.
Development of resistance during the early stages of experimental liver carcinogenesis.
Carcinogenesis
20:
1641-1644,
1999
42.
Zijlstra, JG,
de Vries EG,
and
Mulder NH.
Multifactorial drug resistance in an adriamycin-resistant human small cell lung carcinoma cell line.
Cancer Res
47:
1780-1784,
1987[Abstract].
|
HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Visit Other APS Journals Online |