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Human Glioblastoma Cell Lines: Levels of Low-Density Lipoprotein Receptor and Low-Density Lipoprotein Receptor-related Protein¹

Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 [L. M., E. A. B., K. A. B., L. J. K., T. M. F.], and Brain Tumor Research Center, University of California, San Francisco, California 94143 [D. F. D.]

	ABSTRACT

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The status of the low-density lipoprotein (LDL) receptor and LDL receptor-related protein (LRP) in seven human glioma cell lines was evaluated to extend our knowledge of human glioblastoma multiforme tumor metabolism for future drug design. Cell lines SF-767, SF-763, A-172, U-87 MG, U-251 MG, U-343 MG, and SF-539 were used. Binding of ¹²⁵I-labeled LDL to these cells at 4°C was carried out to determine the number of LDL receptors on cells and the affinity of LDL for these receptors. The content of LRP was measured by immunoblotting. The presence of specific saturable LDL receptors was proven in six of the cell lines investigated. SF-767 cells revealed high-affinity LDL binding (equilibrium dissociation constant, K_d = 7 nM) and maximum binding capacity approximating 300,000 receptors/cell. Most of the remaining cell lines had relatively lower affinity (K_d = 38–62 nM) but also had very high numbers of receptors (128,000–950,000/cell). All cell lines exhibited LRP, but the expression was variable. The cell lines SF-539, U-87 MG, and U-343 MG were particularly rich in this protein. The data suggest that glioblastoma cells have high numbers of LDL receptors; however, there is considerable variation in binding affinity. Overall, this finding suggests that LDL receptors on glioblastoma cells could potentially be useful for targeting antitumor agents. LRP, a multifunctional receptor expressed on glioblastoma cells, also has the possibility for serving as a therapeutic target.

	INTRODUCTION

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Malignant gliomas constitute 35–45% of primary brain tumors. Glioblastoma multiforme tumors are gliomas of highest malignancy (grade IV), characterized by uncontrolled, aggressive cell proliferation and infiltrative growth within the brain and general resistance to conventional treatment. Despite efforts to improve therapies or to develop new ones, the outcome of treatment for malignant gliomas is very modest (median survival after therapy is about 10 months; Ref. 1 ).

Increased cell proliferation and growth is associated with high turnover of cell cholesterol for membrane growth. Cells requiring cholesterol for membrane synthesis may take up plasma LDL³ , the main cholesterol carrier in blood, via receptor-mediated endocytosis (2) , or they may initiate de novo synthesis of cholesterol. There is a body of evidence demonstrating that some types of cancer cells have high LDL requirements together with depletion of LDL in the blood of cancer patients. The latter is thought to be due to elevated LDL receptor levels on rapidly growing tumor cells (for review, see Ref. 3 ). Among types of tumors known to require high amounts of LDL are some types of leukemia (4 , 5) , cancers of gynecological origin (6) , and lung tumor tissues (7 , 8) . It has been suggested that LDL may serve as a selective vehicle for delivery of therapeutic compounds into tumor cells.

There is a paucity of information on the presence and function of LDL receptors in brain cells, both normal and malignant (9, 10, 11) . Using immunocytochemical techniques for LDL receptor localization in monkey and rat brain, Pitas et al. (11) reported relatively few LDL receptors in neurons and glial cells. Staining was most pronounced in astrocytes. Rudling et al. (9) , using homogenates from human intracranial tumors and surrounding normal tissue, evaluated LDL receptor function by a ¹²⁵I-labeled LDL binding assay. LDL receptor binding was highly variable between tumor tissue and normal brain tissue. These studies are potentially confounded by the possibility that the normal tissue surrounding the tumors may have undergone nonspecific changes due to edema or the release of cytokines.

We have previously reported (12) that boronated protoporphyrin that associates with LDL is endocytosed into the human glioblastoma cell line SF-767. Fluorescence microscopy demonstrated that the boronated protoporphyrin-LDL complexes were delivered to lysosomes, suggesting a LDL receptor mechanism. In the present study, we set out to demonstrate that uptake of LDL by SF-767 cells was by a high-affinity saturable LDL receptor mechanism and to estimate the number of LDL receptors on these cells. In the present study, we also determined whether the presence of high-affinity LDL receptors was a general feature of glioblastoma cells; therefore, six other cell lines were evaluated for their ability to bind LDL.

Another member of the LDL receptor family, LRP (13) , is known to be involved in processes of cholesterol homeostasis in the central nervous system (for reviews, see Refs. 14 and 15 ). This multifunctional receptor endocytoses several structurally and functionally distinct ligands, including apo E, which can potentially target cholesterol to LRP-containing cells (16) . In addition to determining the LDL receptor status of glioblastoma cells, we addressed the question whether these cells also possessed LRP; the latter was achieved by using immunoblotting techniques.

	MATERIALS AND METHODS

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Cell Culture.
Seven human glial tumor cell lines (SF-767, SF-763, A-172, U-87 MG, U-251 MG, U-343 MG, and SF-539) were obtained from the tissue bank of the Brain Tumor Research Center (University of California–San Francisco, San Francisco, CA) and have been described previously (17 , 18) . All of the lines originated from grade IV human glioblastoma biopsy specimens. The growth characteristics of the cell lines are shown in Table 1 . The cells were grown in Eagle’s MEM supplemented with 10% fetal bovine serum (Hyclone Laboratories, Logan, UT) and antibiotics [1% fungizone (Life Technologies, Inc., Gaithersburg, MD) and 50 mg/l gentamicin (Sigma Chemical Co., St. Louis, MO)]. Cultures were passaged twice a week to maintain the cells in exponential growth. Twenty-four h before carrying out LDL-binding studies, cells were switched to LPDS; under these conditions, doubling time was reduced 40–60%.

LDLs were labeled with ¹²⁵I (Amersham Pharmacia Biotech, Piscataway, NJ) using IODO-BEADS (Pierce Chemical Co., Rockford, IL) according to manufacturer’s instructions, applying conditions according to Brown and Goldstein (22) . Iodination was performed in 100 mM PBS (pH 6.5) for 20 min at room temperature. ¹²⁵I-labeled LDL was then dialyzed in a Slide-A-Lyzer (Pierce Chemical Co.) against PBS (pH 7.4) and diluted with native LDL to give a final specific activity of about 500 cpm/ng. Both native and iodinated LDLs were kept refrigerated and used in binding experiments within 1 month.

Preparation of LPDS.
After ultracentrifugation at d 1.215 g/ml, lipoproteins were removed by aspiration, and the remaining bottom fraction (i.e., LPDS) was dialyzed against saline. After adjusting to initial volume, plasma was converted to serum by incubation for 24 h at 4°C with thrombin (final concentration 10 US units/ml). The resulting clot was removed by centrifugation. LPDS was sterile filtered and kept in aliquots at -20°C until used.

¹²⁵I-labeled Binding to Glioblastoma Multiforme Cells.
Exponentially growing cells were seeded (day 1) at a concentration of approximately 1 x 10⁵ cells/well into 6-well plates (35-mm wells; 2 ml of medium/well). On day 3, the cells were rinsed with PBS and then provided with fresh LPDS-medium [10% LPDS, 25 mM Hepes (pH 7.4), and 50 mg/l gentamicin in MEM]. Twenty-four h later (day 4), the binding experiments were carried out (the cells were 60–80% confluent).

The binding studies at 4°C were performed essentially as described by Innerarity et al. (23) . Cells were precooled on ice for 15 min, and then the medium in each well was replaced with 1 ml of chilled (4°C) LPDS-medium containing varying concentrations of ¹²⁵I-labeled LDL (in a range of 1–120 µg/ml) to measure total binding (in duplicate), or ¹²⁵I-labeled LDL and 50-fold excess of native LDL (single well/concentration) to obtain information on nonspecific binding. The cells were incubated at 4°C for 4 h, after which the medium was removed (free ¹²⁵I-labeled LDL) and cell monolayers were solublized after careful rinsing.

Cell protein was measured (20) , and ¹²⁵I-labeled LDL binding was determined by -counting (bound ¹²⁵I-labeled LDL values). The difference between total binding and nonspecific binding provides information on the saturable, specific binding of LDL to cells.

The binding curves for SF-767 cells were linearized by Scatchard analysis (24) , from which both K_d (equilibrium dissociation constant) and B_max (maximum binding capacity in ng/mg cell protein) were obtained. The number of receptors/cell was then calculated using molecular weight of apo B 500 kDa and number of cells/well after binding. The data were expressed as means ± SE. Cell lines were first assayed for LDL binding in the range of 1–40 µg/ml ¹²⁵I-labeled LDL on at least two separate occasions; cell lines not demonstrating saturation at 40 µg/ml were then assayed in the range of 2–120 µg/ml ¹²⁵I-labeled LDL. The data reported here are those obtained with cells incubated with 2–120 µg/ml ¹²⁵I-labeled LDL.

Western Blot for LRP.
Glioma cells grown in LPDS medium were washed three times with PBS, harvested from flasks by scraping, and pelleted (yield about 5 x 10⁶ cells/cell line). HepG2 cells (used as a LRP reference), grown as described previously (25) , were also harvested. Cell pellets were frozen (-80°C) for later use.

Cells were lysed in 100 mM Tris-HCl buffer (pH 6.8) containing 2% SDS, 10% glycerol, and a mixture of protease inhibitors [5 mM phenyl-methane-sulfonyl fluoride, 7 µg/ml aprotinin, and complete protease inhibitor mixture (1 tablet/10 ml; Boehringer Mannheim, Indianapolis, IN)]. Cell pellets were mixed vigorously for 10 min in lysis buffer, heated at 100°C for 5 min, and then centrifuged to obtain clear lysate. After protein determination (20) , lysates were aliquoted and stored at -20°C.

Equivalent amounts of protein (20 µg/lane) were subjected to SDS-PAGE (21) under nonreducing conditions, using 4–20% gradient polyacrylamide gels (Novex, San Diego, CA). Proteins were transblotted to nitrocellulose and probed with anti-LRP antibody, which recognizes the 500-kDa extracellular portion of LRP (8G1), kindly provided by Dr. Dudley K. Strickland (American Red Cross, Rockville, MD). Rabbit liver membranes (26) were used as a standard to confirm the position of LRP. Antibody binding was detected by chemifluorescence (ECL Plus; Amersham Pharmacia Biotech), and relative intensity of bands was quantified using the Phosphor/fluor Imager (Bio-Rad Laboratories).

	RESULTS

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The specific binding of LDL to SF-767 cells at 4°C is shown in Fig. 1A . The data indicate that saturation of LDL receptors is achieved at 20 µg/ml. ¹²⁵I-labeled LDL binds to these cells with high affinity (Fig. 1B) with a calculated K_d of 7 nM. From the Scatchard plot analysis we calculate that the maximum binding capacity is 300,000 receptors/cell (Table 2) . To determine whether other glioma cell lines had similar LDL binding capacity as SF 767 cells, 4°C binding studies were carried out on the cells shown in Table 2 . Compared with SF-767 cells, all other glioma cells had at least an order of magnitude lower binding affinity; however, two cell lines, SF-763 and A-172, had extremely high numbers of receptors (923,000–950,000 receptors/cell), suggesting these cells possessed large numbers of low-affinity receptors. Cell lines U-251 MG, U-343 MG, and SF-539 have receptor numbers more similar to that of SF-767 but have lower binding affinity than SF-767. One cell line, U-87 MG, had no detectable high-affinity receptors, and binding was solely nonspecific. To test whether U-87 MG cells express LDL receptor protein, cells were solublized and protein was electrophoresed on SDS-PAGE under reducing conditions and probed with anti-LDL receptor antibody (kindly provided by Dr. Janet Boyles). The U-87 MG cells were compared with human HepG2 cells known to have LDL receptor activity. Based on this analysis, U-87 MG cells had 2-fold greater LDL receptor content than HepG2 cells (data not shown), indicating that, although specific binding was not evident, LDL receptor protein was present. During LDL-binding incubations, U-87 MG cells become rounded, suggesting that the lack of receptor activity may reflect a change in LDL receptor conformation in the morphologically altered cells.

View larger version (21K): [in this window] [in a new window] [Download PPT slide]   Fig. 1. 125I-labeled LDL binding to SF-767 cells. A, the cells were incubated at 4°C for 4 h with increasing amounts of 125I-labeled LDL in the absence (total binding) or presence (nonspecific binding) of 50-fold excess of unlabeled LDL. Specific binding was calculated by subtracting nonspecific from total binding. The figure is a representative example of four experiments. B, Scatchard plot of the specific binding. Bound/free represents 125I-labeled LDL bound (ng/mg of cell protein) divided by the amount of 125I-labeled LDL present in medium during binding (ng/ml). The plot indicates high-affinity binding (Kd = 6.98 nM) of LDL to SF-767 cells.

View larger version (29K): [in this window] [in a new window] [Download PPT slide]   Fig. 2. Western blot analysis for LRP on HepG2 (used as a LRP-containing standard) and seven glioblastoma cell lines. Equivalent amount of cell lysates (20 µg protein/lane) were subjected to 4–20% SDS-PAGE under nonreducing conditions and transferred to nitrocellulose membrane. LRP was detected by an antibody directed against the external subunit of the receptor [1:1000 dilution in 10 mM Tris-HCl and 150 mM NaCl (pH 7.4), with 0.05% Tween 20] and revealed by immunofluorescence.

	DISCUSSION

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Large numbers of high-affinity LDL receptors have been described in primary culture of rat glial cells obtained from brains of rat pups, 1–2 days of age (28) , suggesting that, in rapidly growing rat brains, cholesterol requirement is likely to be high as in the case of many tumor cells. Although there is a paucity of information on LDL receptor affinity and number on glioblastoma multiforme cells, earlier studies have demonstrated binding (29) and internalization (30) of LDL to U-251 MG cells. The present study unequivocally demonstrates that SF-767 cells possess large numbers of high-affinity LDL binding sites, thus explaining our previous observation of time- and concentration-dependent uptake of boronated protoporphyrin into lysosomes (12) . This compound is associated with LDL and is, thus, transported into cells via the LDL receptor. Our study also shows that glioblastoma cell lines, in general, seem to possess large numbers of LDL receptors, albeit there is a wide spectrum in binding affinity. We cannot rule out that some of this variability may be attributable to cell passage number. Alternatively, differences in binding affinity may reflect changes in plasma membrane lipid composition, which could alter LDL receptor conformation and subsequent LDL binding. The SF-767 cell line revealed high binding affinity comparable with the binding affinity described by Brown and Goldstein (22) for human skin fibroblasts, K_d = 7.0 nM for SF-767 cell line versus 4.5 nM for fibroblasts. In conjunction with their high binding affinity, the SF-767 cells also had large numbers of LDL receptors, 300,000/cell. In contradistinction to the SF-767 cells, the majority of glioblastoma cells in the current study had relatively lower binding affinity, K_d = 38–62 nM, but high numbers of receptors (128,000–950,000/cell). These K_d values are comparable with K_d of HepG2 cells (30 nM) (25) . Our data suggest that the LDL receptor is up-regulated in glioblastoma cells, which is consistent with the observation that during early development of the rat, when glial cells are rapidly growing, there is a substantial increase in LDL receptors compared with adult glial cells, which have little or no LDL receptors (11 , 28) . Because our study indicates that glioblastoma cell lines have large numbers of receptors, the LDL receptor could potentially be useful for targeting antitumor drugs to glioblastoma cells using LDL as the transport vehicle.

LRP is a multiligand receptor, which has the capacity to bind and internalize apo E-containing lipoproteins and, hence, is an alternative route for the uptake of cholesterol into cells. Unlike the LDL receptor, which is not readily detectable in neurons and glial cells in normal brain (11) , LRP is found in high abundance in neurons but not in glial cells (31, 32, 33, 34) . Interestingly, neoplastic transformation of glial cells is associated with an increased expression of LRP in glial cells compared with normal tissue (31) . Moreover, Yamamoto et al. (35) , demonstrated in neoplastic glioblastoma cells compared with low-grade astrocytomas that LRP expression was intense in the former cells and almost undetectable in the latter. This suggests that LRP expression may be regulated by the growth rate of the cells. It was previously reported that LRP is abundant in the glioblastoma cell lines U-87 MG (36) and A-172 and U-251 MG (35) . Our studies confirm these findings and extend the observations to four additional cell lines (SF-767, SF-539, SF-763, and U-343 MG). Our data, together with that of others, strongly suggest that up-regulation of LRP may be a significant feature of glioblastoma cells. The present study indicates, however, that there is no apparent association between LDL receptor number and relative LRP expression because the cells with the highest number of LDL receptors (SF-763 and A-172) had relatively low LRP expression.

	ACKNOWLEDGMENTS

 
We thank Dr. Scott Taylor for helpful discussion of this manuscript.

	FOOTNOTES

 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Supported by the Director, Office of Energy Research, Office of Laboratory Policy and Infrastructure Management, of the United States Department of Energy under contract DE-ACO3-76SF00098 and by NIH Grants HL-18574 (to T. M. F.) and CA-13525 (to D. F. D.). Preliminary data were presented at the 8th International Symposium on Neutron Capture Therapy for Cancer, San Diego, California, 1998.

² To whom requests for reprints should be addressed, at Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS: 1-315A, Berkeley, CA 94720. Phone: (510) 486-5567; Fax: (510) 486-4750; E-mail: TMForte{at}lbl.gov

³ The abbreviations used are: LDL, low-density lipoprotein; LRP, LDL receptor-related protein; LPDS, lipoprotein-deficient serum; apo, apolipoprotein.

Received 9/ 7/99. Accepted 2/18/00.

	REFERENCES

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1. Leibel S. A. Primary and metastatic brain tumors in adults Leibel S. A. Phillips T. L. eds. . Textbook of Radiation Oncology, : 293-323, W. B. Saunders Company Philadelphia 1998.
2. Brown M. S., Goldstein J. L. A receptor-mediated pathway for cholesterol homeostasis. Science (Washington DC), 232: 34-47, 1986.[Free Full Text]
3. Firestone R. A. Low-density lipoprotein as a vehicle for targeting antitumor compounds to cancer cells. Bioconjugate Chem., 5: 105-113, 1994.[Medline]
4. Vitols S., Gahrton G., Öst Å., Peterson C. Elevated low density lipoprotein receptor activity in leukemic cells with monocytic differentiation. Blood, 63: 1186-1193, 1984.[Abstract/Free Full Text]
5. Vitols S., Gahrton G., Björkholm M., Peterson C. Hypocholesterolaemia in malignancy due to elevated low-density-lipoprotein-receptor activity in tumour cells: evidence from studies in patients with leukaemia. Lancet, 2: 1150-1153, 1985.[Medline]
6. Gal D., MacDonald P. C., Porter J. C., Simpson E. R. Cholesterol metabolism in cancer cells in monolayer culture. III. Low-density lipoprotein metabolism. Int. J. Cancer, 28: 315-319, 1981.[Medline]
7. Vitols S., Peterson C., Larsson O., Holm P., Åberg B. Elevated uptake of low density lipoproteins by human lung cancer tissue in vivo. Cancer Res., 52: 6244-6247, 1992.[Abstract/Free Full Text]
8. Lundberg B. Preparation of drug-low density lipoprotein complexes for delivery of antitumoral drugs via the low density lipoprotein pathway. Cancer Res., 47: 4105-4108, 1987.[Abstract/Free Full Text]
9. Rudling M. J., Angelin B., Peterson C. O., Collins V. P. Low density lipoprotein receptor activity in human intracranial tumors and its relation to the cholesterol requirement. Cancer Res., 50: 483-487, 1990.[Abstract/Free Full Text]
10. Leppälä J., Kallio M., Nikula T., Nikkinen P., Liewendahl K., Jääskeläinen J., Savolainen S., Gyling H., Hiltunen J., Callaway J., Kahl S., Färkkilä M. Accumulation of ^99mTc-low-density lipoprotein in human malignant glioma. Br. J. Cancer, 71: 383-387, 1995.[Medline]
11. Pitas R. E., Boyles J. K., Lee S. H., Hui D., Weisgraber K. H. Lipoproteins and their receptors in the central nervous system. J. Biol. Chem., 262: 14352-14360, 1987.[Abstract/Free Full Text]
12. Callahan D. E., Forte T. M., Afzal S. M. J., Deen D. F., Kahl S. B., Bjornstad K. A., Bauer W. F., Blakely E. A. Boronated protoporphyrin (BOPP): localization in lysosomes of the human glioma cell line SF-767 with uptake modulated by lipoprotein levels. Int. J. Radiat. Oncol. Biol. Phys., 45: 761-771, 1999.[Medline]
13. Herz J., Hamann U., Rogne S., Myklebost O., Gausepohl H., Stanley K. K. Surface location and high affinity for calcium of a 500-kDa liver membrane protein closely related to the LDL-receptor suggest a physiological role as lipoprotein receptor. EMBO J., 7: 4119-4127, 1988.[Medline]
14. Krieger M., Herz J. Structures and functions of multiligand lipoprotein receptors: macrophage scavenger receptor and LDL receptor-related protein (LRP). Annu. Rev. Biochem., 63: 601-637, 1994.[Medline]
15. Mahley R. W. Heparan sulfate proteoglycan/low density lipoprotein receptor-related protein pathway involved in type III hyperlipoproteinemia and Alzheimer’s disease. Isr. J. Med. Sci., 32: 414-429, 1996.[Medline]
16. Kowal R. C., Herz J., Goldstein J. L., Esser V., Brown M. S. Low density lipoprotein receptor-related protein mediates uptake of cholesteryl esters derived from apoprotein E-enriched lipoproteins. Proc. Natl. Acad. Sci. USA, 86: 5810-5814, 1989.[Abstract/Free Full Text]
17. Mohapatra G., Kim D. H., Feuerstein B. G. Detection of multiple gain and losses of genetic material in ten glioma cell lines by comparative genomic hybridization. Genes Chromosomes Cancer, 13: 86-93, 1995.[Medline]
18. Basu H. S., Pellarin M., Feuerstein B. G., Shirahata A., Samejima K., Deen D. F., Marton L. J. Interaction of a polyamine analogue, 1,19-bis-(ethylamine)-5,10,15-triazanonadecane (BE-4–4-4–4), with DNA and effect on growth, survival, and polyamine levels in seven human brain tumor cell lines. Cancer Res., 53: 3948-3955, 1993.[Abstract/Free Full Text]
19. Goldstein J. L., Basu S. K., Brown M. S. Receptor-mediated endocytosis of low-density lipoprotein in cultured cells. Methods Enzymol., 98: 241-260, 1983.[Medline]
20. Markwell M. K., Haas S. M., Bieber L. L., Tolbert N. E. A modification of the Lowry protein procedure to simplify determination in membrane and lipoprotein samples. Anal. Biochem., 87: 206-210, 1978.[Medline]
21. Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature (Lond.), 227: 680-685, 1970.[Medline]
22. Brown M. S., Goldstein J. L. Familial hypercholesterolemia: defective binding of lipoproteins to cultured fibroblasts associated with impaired regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Proc. Natl. Acad. Sci. USA, 71: 788-792, 1974.[Abstract/Free Full Text]
23. Innerarity T. L., Pitas R. E., Mahley R. W. Lipoprotein-receptor interactions. Methods Enzymol., 129: 542-564, 1986.[Medline]
24. Kenakin, T. Pharmacologic Analysis of Drug-Receptor Interaction, Ed. 2. New York: Raven Press, 1993.
25. Hara S., McCall M. R., Forte T. M. Re-uptake of nascent low-density lipoproteins by HepG2 cells. Biochim. Biophys. Acta, 1168: 199-204, 1993.[Medline]
26. Maletínská L., Slaninová J., Kunes J., Zelezná B. Direct evidence for an angiotensin AT₁ receptor type in rat vas deferens. Eur. J. Pharmacol., 351: 371-375, 1998.[Medline]
27. Roheim P. S., Carey M., Forte T. M., Vega G. L. Apolipoproteins in human cerebrospinal fluid. Proc. Natl. Acad. Sci. USA, 76: 4646-4649, 1979.[Abstract/Free Full Text]
28. Jung-Testas I., Weintraub H., Dupuis D., Eychenne B., Baulieu D-E., Robel P. Low density lipoprotein-receptors in primary cultures of rat glial cells. J. Steroid Biochem. Mol. Biol., 42: 597-605, 1992.[Medline]
29. Murakami M., Yshio Y., Mihara Y., Kuratsu J-I., Horiuchi S., Morino Y. Cholesterol uptake by human glioma cells via receptor-mediated endocytosis of low-density lipoprotein. J. Neurosurg., 73: 760-767, 1990.[Medline]
30. Rudling M. J., Collins V. P., Peterson C. O. Delivery of aclacinomycin A to human glioma cells in vitro by the low-density lipoprotein pathway. Cancer Res., 43: 4600-4605, 1983.[Abstract/Free Full Text]
31. Lopes M. B. S., Bogaev C. A., Gonias S. L., VandenBerg S. R. Expression of ₂-macroglobulin is increased in reactive and neoplastic glial cells. FEBS Lett., 338: 301-305, 1994.[Medline]
32. Wolf B. B., Lopes M. B. S., VandenBerg S. R., Gonias S. L. Characterization and immunohistochemical localization of ₂-macroglobulin receptor (low-density lipoprotein receptor-related protein) in human brain. Am. J. Pathol., 141: 37-42, 1992.[Abstract]
33. Fabrizi C., Businaro R., Persichini T., Fumagalli L., Lauro G. M. The expression of the LDL receptor-related protein (LRP) correlates with the differentiation of human neuroblastoma cells. Brain Res., 776: 154-161, 1997.[Medline]
34. Tooyama I., Kawamata T., Akiyama H., Kimura H., Moestrup S. K., Gliemann J., Matsuo A., McGeer P. L. Subcellular localization of the low density lipoprotein receptor-related protein (₂-macroglobulin receptor) in human brain. Brain Res., 691: 235-238, 1995.[Medline]
35. Yamamoto M., Ikeda K., Ohshima K., Tsugu H., Kimura H., Tomonaga M. Increased expression of low density lipoprotein receptor-related protein/₂-macroglobulin receptor in human malignant astrocytomas. Cancer Res., 57: 2799-2805, 1997.[Abstract/Free Full Text]
36. Bu G., Maksymovitch E. A., Geuze H., Schwartz A. L. Subcellular localization and endocytic function of low density lipoprotein receptor-related protein in human glioblastoma cells. J. Biol. Chem., 269: 29874-29882, 1994.[Abstract/Free Full Text]

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