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Clinical Cancer Research Vol. 8, 615-619, February 2002
© 2002 American Association for Cancer Research

Cell Biology

Automated Electrorotation to Reveal Dielectric Variations Related to HER-2/neu Overexpression in MCF-7 Sublines1

Massimo Cristofanilli2, Giovanni De Gasperis, Lisha Zhang, Mien-Chie Hung, Peter R. C. Gascoyne and Gabriel N. Hortobagyi

Departments of Breast Medical Oncology [M. C., G. N. H.], Experimental Pathology [G. D. G., P. R. C. G.], and Tumor Biology [L. Z., M. C. H.], The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030


   ABSTRACT
Top
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Purpose: Electrorotation (ROT) is a technique that allows for determination of the dielectric properties of living cells when exposed to a rotating electric field. We evaluated the ROT behavior of MCF/neo and p185neu transfectancts MCF/HER2–11 and MCF/HER2–18 to investigate whether differences in HER-2/neu expression were associated with differences in dielectric properties in these cells.

Experimental Design: P185neu was measured by Western blotting in MCF/neo cells and HER-2/neu transfectants MCF/HER2–11 and MCF/HER2–18. ROT spectra and cell membrane-specific capacitance were obtained for each cell line.

Results: The mean cell membrane-specific capacitance values for MCF/neo, MCF/HER2–11, and MCF/HER2–18 were 2.09, 1.70, and 2.56 µF/cm2, respectively. The mean specific capacitance for MCF/neo was significantly different from that for MCF/HER2–11 (P = 0.006) and that for MCF/HER2–18 (P = 0.007).

Conclusions: ROT is sufficiently sensitive to detect variations in dielectric properties in breast cancer cell lines overexpressing p185neu. These differences may be related to the morphological alterations determined by HER-2/neu overexpression.


   INTRODUCTION
Top
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Cell separation techniques are fundamental in cell biology and have application to molecular diagnostics and therapeutics. The ability to effectively isolate and characterize single cells from a heterogeneous population (1, 2, 3, 4) represents the most limiting factor to the widespread utilization of many current sorting technologies (5, 6, 7, 8) . Improvements in cell-sorting methods depend on the use of novel cellular properties able to discriminate among cell types and manipulate selective cells. One such property, dielectric affinity, can be exploited for cell separation (3 , 9) .

A cell suspended in a medium with different dielectric properties becomes electrically polarized when subjected to an electric field. Interaction between this induced polarization and the field produces various electrokinetic effects (9, 10, 11, 12) , e.g., a spatially inhomogeneous field will exert a lateral dielectrophoretic force on an uncharged particle, directing it away from regions of high electric field strength. A rotating field, in contrast, will induce the particle to spin, a phenomenon called ROT.3

Cellular ROT involves using a rotating electric field generated by a four-electrode arrangement to induce isolated single cells to rotate (13 , 14) . The direction and rate of the spin strongly depend on the frequency and spatial configuration of the field and on the dielectric properties of the suspending medium and the cells. This noninvasive technique can be used to characterize the dielectric properties of individual living cells. Because it can discriminate between single cells, ROT can be used to characterize the dielectric properties of cell subpopulations that can be differentiated within a cell mixture through size, morphology, staining susceptibility, and other biological criteria (15, 16, 17, 18) . For this reason, ROT is an ideal tool for defining the operating parameters for dielectrophoretic cell-sorting devices, in which cell types with different properties are physically separated and purified according to their dielectric properties. An example is the successful separation of human breast cancer cells and leukemia cells from diluted human blood after ROT characterization of the different cell types (3 , 19) . Significantly, cells separated this way do not seem to be damaged by the field exposure, as demonstrated by their ability to reestablish growth with minimal loss afterward (20 , 21) .

The relationship between dielectric characteristics and human HER-2/neu (c-erbB-2) gene expression is of interest to us because HER-2/neu is amplified in many adenocarcinomas, overexpressed in ~30% of primary breast carcinomas, and considered an important prognostic factor (22) . In vitro and in vivo experiments have demonstrated that overexpression of the normal HER-2/neu gene product, p185neu, results in changes in cell morphology and manifestation of the tumorigenic phenotype in various cell lines (23 , 24) .

We evaluated the ROT behavior of MCF/neo and p185neu transfectancts MCF/HER2–11 and MCF/HER2–18 to investigate whether differences in HER-2/neu expression were associated with differences in dielectric properties in these cells.


   MATERIALS AND METHODS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Cell Lines and Culture.
Human breast cancer sublines MCF/neo, MCF/HER2–11, and MCF/HER2–18 were provided by Dr. Christopher C. Benz (23) . MCF/neo expressed a neomycin phosphotransferase gene (neo), and stable transfectants MCF/HER2–11 and MCF/HER2–18 expressed full-length HER-2/neu cDNA, under SV40 promoter control. MCF/HER2–11 and MCF/HER2–18 transfectants are known to express, respectively, 20 and 45 times the level of surface receptor than parental MCF-7 cells or the MCF/neo control subline.

Cells were grown in DMEM-F12 medium supplemented with 10% fresh bovine serum and 100 units/ml penicillin and maintained in a humidified incubator with 5% CO2/95% air at 37°C.

Cell Preparation.
Cells were collected 48–72 h after seeding at ~80% confluence by exposing the monolayer to 0.1% trypsin for 3–5 min. Cells were then suspended in serum-supplemented medium to neutralize the trypsin. Cell suspensions had >95% viability, as determined by trypan blue dye exclusion.

Harvested cells, in complete culture medium, were diluted to ~5 x 104/ml with isotonic, 8.5% sucrose, plus 0.3% dextrose buffer. To minimize the influence of plasma membrane conductivity, sample conductivity was adjusted with culture medium to 56 mS/m as verified with a Cole-Parmer conductivity meter (Vernon Hill, IL).

Western Blot Analysis.
Cells were lysed with 100 µl of PBS containing 0.1% Triton. Protein content of the lysates was determined using a modified Bradford protein assay (Bio-Rad Laboratories, Richmond, CA). Protein (~30 µg) from each lysate was loaded onto a 15% SDS gel, and the sample was resolved by SDS-PAGE. HER-2/neu was detected with commercially available anti-HER-2/neu antibodies, c-neu-Ab-3 (Oncogene Science, Inc., Manhasset, NY) against the p185 protein (p185neu). The blots were incubated with horseradish peroxidase-conjugated goat antimouse IgG (Boehringer-Mannheim, Indianapolis, IN), and the p185 was detected with the enhanced chemiluminescence system. Actin was used as a control.

ROT Measurement System.
The four main components of the ROT measurement system were a signal generator, an imaging system, an optical system, and a ROT chamber, described previously in details (Ref. 25 ; Fig. 1Citation ).



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  		Fig. 1. Representation of the experimental set-up of the ROT system (see text for details).

 
Electrical fields were generated by applying four sine waves in phase quadrature to an electrode array in the ROT chamber of the signal generator. A custom-built, directfrequency synthesizer (N64001–200DDFS-4CH; Neos Technologies, Melbourne, FL) provided signals with a frequency range of 0.5 Hz to 250 MHz and a power output of <=500 mW over a bandwidth of 1 kHz to 200 MHz. The four output channels were phased at 0, 90, 180, and 270 degrees, with a tolerance of ±3 degrees.

The hardware for the imaging system was based on a single-CPU motherboard (Pentium Pro 200 MHz; Asus Computer International, San Jose, CA) and a PCI Matrox Genesis imaging platform coupled with the Matrox MIL-32 version 4.02 of the real-time imaging library (Matrox Electronic Systems, Ltd, Dorval, Canada). A specific machine-vision algorithm has been developed to achieve the real-time measurement of ROT spectra. The estimated sampling rate for real-time ROT for this system was 12 Hz (focused on a single cell).

The optical system consisted of an inverted microscope (Nikon DIAPHOT-TMD) equipped with an x60/0.7 numerical-aperture, long working distance objective lens. In our system, a charge-coupled device XC-77 camera (Hamamatsu Corp., Bridgewater, NJ) acquired the images from the microscope for the frame grabber. A Laser Tweezers system that used a 100-mW, solid-state laser diode that emitted light at 830 nm was incorporated into the microscope (Cell Robotics, Albuquerque, NM). Laser tweezers were used to drag cells of interest into the center of the electrode array. Once in position for measurement, the laser tweezers could be turned off or used to hold the cell slightly above the electrode array so that the cell’s ROT was not slowed by frictional contact with the chamber bottom. The laser tweezers lend the important capability of allowing cells from a larger field of cells to be selected for measurement and moved to the measurement zone. Cells were exposed to the laser tweezers for not >5 min.

The ROT electrodes in the rotation chamber were patterned by photolithography on sputtered, thin films of gold (150 nm) over titanium (50 nm) and supported on glass slides. Electrodes had second-order polynomial geometry and an inner diameter of 400 µm. The applied-field amplitude was kept constant at 1 V rms. The maximum instantaneous AC field-induced potential across the cell membrane was <50 mV.

ROT was measured by placing cells in a rotating electric field and inducing them to rotate on an essentially stationary axis. The automated ROT measurement system allowed the full ROT spectrum in the range 1 kHz to 200 MHz to be obtained for each cell in <3 min (26) . We performed at least 25 measurements for each cell type. Dielectric parameters for each cell type were obtained by fitting the measured spectra to the simple shell model (9 , 15) .

Results were reported as mean and median Cspec in µF/cm2. Statistical comparison among cell types was performed using the Student t test.


   RESULTS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Western blot analysis confirmed that MCF/HER2–11, MCF/HER2–18, and MCF/neo control cells expressed different amounts of p185neu (Fig. 2)Citation .



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  		Fig. 2. Western blot analysis demonstrating differences in the levels of p185neu expression among MCF-7, MCF-neo (MCF), MCF/HER2–11 (MCF 11), and MCF/HER2–18 (MCF 18) cells.

 
ROT spectra for the three cell lines showed antifield rotation (against the direction of the field spin) in the kHz range and cofield rotation in the MHz range. Antifield and cofield peaks (Fig. 3)Citation and distributions were different for the three cell lines investigated, and an analysis of the spectra was conducted to determine the mean cell dielectric parameters and their distributions for the different cell types. The spectral features that are determined by the cell dielectric properties are the frequencies of the cofield and antifield rotation peaks and the frequency at which the rotation crosses from a negative to a positive sense. The scaling height of the rotation spectra does not impact the cell parameters. It should also be noted that at low frequencies (in the kHz range), the applied electrical field is mainly dropped across the plasma membrane, which behaves as a poorly conducting sphere with a high permitivity. On the contrary, at high frequencies (in the MHz range), the applied field gradually penetrates into the cell, which then behaves as a conducting sphere having the permitivity of the cell’s cytoplasmic components (27, 28, 29) .



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  		Fig. 3. ROT spectra for three cell lines suspended in sucrose/dextrose medium of conductivity 56 mS/m. Analysis of the ROT spectra of MCF/neo (^), MCF/HER2–11 (*), and MCF/HER2–18 (+) cells demonstrates variation in cofield rotation (positive deflection) and antifield rotation (negative deflection).

 
The ROT spectra analysis demonstrated that MCF/HER2–11 and MCF/HER2–18 had similar rotational patterns, whereas the MCF/neo showed a different distribution (Fig. 3)Citation . Furthermore, regarding the cell dielectric parameters, we demonstrated that variations in antifield and cofield rotation peaks translated into differences in dielectric properties between MCF/neo and MCF/HER2–11 cells and between MCF/neo and MCF/HER2–18 cells. The mean Cspec values for MCF/neo, MCF/HER2–11, and MCF/HER2–18 were 2.09, 1.70, and 2.56 µF/cm2, respectively. The mean Cspec for MCF/neo was significantly different from those of MCF/HER2–11 (P = 0.006) and MCF/HER2–18 (P = 0.007; Table 1Citation ).


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  		Table 1 Mean Cspec for the three breast cancer cell lines

 

   DISCUSSION
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
An electric field induces image charges at the interface between a liquid and a suspended body with different dielectric properties (16) . If the fields rotate, these charges travel synchronously but lag behind the rotating field because of charge relaxation in the body and surrounding medium (17 , 18 , 20, 21, 22, 23, 24, 25, 26, 27, 28) . The permanent angular displacement between the rotating field vector and the images charges leads to a torque on the cell and induces rotation. When exposed to these rotating fields, cells can be driven either with or against the direction of field rotation (cofield versus antifield rotation; Refs. 16 , 27 , and 28 ). The direction of the spin depends on the polarizability of the cell relative to the surrounding medium. The polarizability of the cell is in turn related to the dielectric properties of the cells’ various "membranous" components (cell membrane, cytoplasm, and vacuoles; Refs. 27, 28, 29 ). The sensitivity of ROT to the modifications in permeability and electrical charge of the various membrane compartments of the cells (e.g., the cell membrane) should constitute an ideal tool to investigate transformed cells.

The sensitivity of this technique was described in detail by sophisticated earlier studies conducted by Huang et al. (30) with DS19 murine erythroleukemia and six M2 rat kidney cells, which were dielectric property and examined as a function of differentiation induced by chemical means and by temperature, respectively. These cell types exhibited changes in cell surface morphology that resulted in an alteration of the surface area of the membrane, which correlated with changes in cell membrane capacitance observed by ROT (30) . To demonstrate that cell surface morphology explained the dielectric changes, DS19 and MDA 435 cells were exposed to buffers that ranged in osmolarity from 150 mOs to 450 mOs. Cell volume, as determined by measurements obtained with different modalities, including routine light microscope, Coulter sizing, and electron microscopy, varied proportionately with the osmotic changes and cell surface morphology. Membrane capacitance, determined by ROT, mirrored the cell membrane changes exactly, showing that membrane morphology plays a dominant role in the dielectric behavior of cells. Changes in the cell surface morphology of harvested cells were similar to changes seen in monolayer cultures (30) .

Our investigation focused on using ROT to detect differences in dielectric properties that have occurred in MCF-7 sublines as a consequence of overexpression of the HER-2/neu oncogene. HER2/neu has extensive structural homology to the human epidermal growth factor (31, 32, 33) , and both p185neu and epidermal growth factor possess an intracellular region containing a tyrosine kinase domain, a hydrophobic transmembrane-spanning sequence, and an extracellular portion containing two cysteine-rich clusters. Overexpressed p185neu has been shown to transform mammalian cells and induce morphological changes (23 , 24 , 31) . Transfection of the HER-2/neu oncogene in the MCF-7 is in fact associated with transformation and modifications in the morphology of the cells (23 , 34) . Our results suggest that overexpression of p185neu modifies the dielectric properties of the cells. These modifications, which affect cofield and antifield rotation, are related to the morphological transformation and related variation in electric permitivity of the various membranous components affected by the oncogene’s expression (23 , 24 , 34) . It is intuitive that the use of ROT, along with immunohistochemistry and more descriptive technologies like electron microscopy, can contribute to the definition of the chronology of morphological and biological modifications associated with the transformed phenotype.

Our results indicate that the magnitude of modifications in dielectric properties are not dependent on the level of HER-2/neu overexpression, as demonstrated by the differences measured between MCF/neo and the two sublines transfected with HER-2/neu. However, this study was not designed to address this issue. A more detailed description of the molecular and morphological events associated with the different levels of p185neu overexpression (e.g., cell-cycle regulation and the consequent transformation process; Ref. 34 ) will possibly clarify the presence of a dose-dependent phenomenon.

In summary, ROT appears to be an extremely sensitive technology capable of detecting variations in dielectric properties among breast cancer cell lines that differ in their levels of p185neu expression (23) . These results suggest the possibility of using ROT for the characterization of HER-2/neu overexpressing "living" breast cancer cells. This novel approach may provide a more sensitive tool for the description of the biology of these tumors compared with the available methods represented by immunohistochemistry and fluorescence in situ hybridization, requiring extensive tissue processing (35) .


   ACKNOWLEDGMENTS
 
We thank Dr. Xiaobo Wang for insightful discussions and constructive support and Drs. Eun Lee and Simon Kwong for assistance with the tissue culture and Western blot analyses.


   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 in part by the Nellie B. Connely Breast Cancer Research Fund. Back

2 To whom requests for reprints should be addressed, at Department of Breast Medical Oncology, Box 424, The University of Texas, M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030. Phone: (713) 792-2817; Fax: (713) 794-4385; E-mail: mcristof{at}mdanderson.org Back

3 The abbreviations used are: ROT, electrorotation; Cspec, cell membrane-specific capacitance. Back

Received 1/31/01; revised 11/27/01; accepted 11/29/01.


   REFERENCES
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Siggelkow H., Hilmes D., Robenstorff K., Kurre W., Engel I., Hufner M. Analysis of human primary bone cells by fluorescence activated cell scanning: methodological problems and preliminary results. Clin. Chim. Acta, 272: 111-125, 1998.[CrossRef][Medline]
  2. Berteau P., Dumas F., Gala J. L., Eschwege P., Lacour B., Philippe M., Loric S. Molecular detection of circulating prostate cells in cancer II: comparison of prostate epithelial cells isolation procedures. Clin. Chem., 44: 1750-1753, 1998.[Free Full Text]
  3. Cheng J., Sheldom E. L., Wu L., Haller M. J. Isolation of cultured cervical carcinoma cells mixed with peripheral blood cells on a bioelectronic chip. Anal. Chem., 70: 2321-2326, 1998.[Medline]
  4. Gimsa J., Wachner D. A unified resistor-capacitor model for impedance, dielectrophoresis, electrorotation, and induced transmembrane potential. Biophys. J., 75: 1107-1116, 1998.[Abstract/Free Full Text]
  5. Seidl J., Knuechel R., Kunz-Schughart L. A. Evaluation of membrane physiology following fluorescence activated or magnetic cell separation. Cytometry, 36: 102-111, 1999.[CrossRef][Medline]
  6. Engel H., Kleespies C., Friedrich J., Breidenbach M., Kallenborn A., Schondorf T., Kolhagen H., Mallmann P. Detection of circulating tumor cells in patients with breast or ovarian cancer by molecular cytogenetics. Br. J. Cancer, 81: 1165-1173, 1999.[CrossRef][Medline]
  7. Holmes P., Al-Rubeai M. Improved cell line development by a high throughput affinity capture surface display technique to select for high secretors. J. Immunol. Methods, 230: 141-147, 1999.[CrossRef][Medline]
  8. Herault O., Colombat P., Domenech J., Degenne M., Bremond J. L., Sensebe L., Bernard M. C., Binet C. A rapid single-laser flow cytometry method for discrimination of early apoptotic cells in a heterogeneous cell population. Br. J. Haematol., 104: 530-537, 1999.[CrossRef][Medline]
  9. Wang X-B., Huang Y., Gascoyne P. R., Becker F. F., Holzel R., Pethig R. Changes in Friend murine erythroleukemia cell membranes during induced differentiation determined by electrorotation. Biochim. Biophys. Acta, 1193: 330-344, 1994.[Medline]
  10. Wang X-B., Hughes M. P., Huang Y., Becker F. F., Gascoyne P. R. Non-uniform spatial distributions of both the magnitude and phase of AC electric fields determine dielectric forces. Biochim. Biophys. Acta, 1243: 185-194, 1995.[Medline]
  11. Fuhr G. T., Schnelle T., Muller H., Glasser H., Lisec T., Wagner B. Positioning and manipulation of cells and microparticles using miniaturized electric field traps and travelling waves. Sensors Mater, 7: 131-146, 1995.
  12. Wang X-B., Huang Y., Wang X., Becker F. F., Gascoyne P. R. C. Dielectric manipulation of cells with spiral electrodes. Biophys. J., 73: 1118-1129, 1997.[Abstract/Free Full Text]
  13. Arnold W. M., Zimmermann U. Rotation of an isolated cell in a rotating electrical field. Naturwissenschaften, 69: 297 1982.[CrossRef][Medline]
  14. Arnold W. M., Zimmermann U. Rotating field induced rotation and measurement of the membrane capacitance of single mesophyll cells of Avena sativa. Z Naturforsch [C], 37: 908-915, 1982.
  15. Huang Y., Pethig R., Holzel R., Wang X-B. Differences in the AC electrodynamics of viable and nonviable yeast cells determined through combined dielectrophoresis and electrorotation studies. Phys. Med. Biol., 37: 1499-1517, 1992.[CrossRef][Medline]
  16. Mischel M., Voss A., Pohl H. A. Cellular spin resonance in rotating electric field. J. Biol. Phys., 10: 223-226, 1982.[CrossRef]
  17. Yang J., Huang Y., Wang X-B., Becker F. F., Gascoyne P. R. Differential analysis of human leukocytes by dielectrophoretic field-flow fractionation. Biophys. J., 78: 2680-2689, 2000.[Abstract/Free Full Text]
  18. Engel J., Donath E., Gimsa J. Electrorotation of red cells after electroporation. Stud. Biophys., 125: 53-62, 1988.
  19. Becker F. F., Wang X-B., Huang Y., Pethig R., Vykouka I. J., Gascoyne P. R. C. Separation of human breast cancer cells from blood by differential dielectric affinity. Proc. Natl. Acad. Sci. USA, 92: 860-864, 1995.[Abstract/Free Full Text]
  20. Wang X-B., Yang J., Gascoyne P. R. C. Role of peroxide in AC electrical field exposure effects on Friend murine erythroleukemia cells during dielectrophoretic manipulations. Biochim. Biophys. Acta, 1426: 53-68, 1999.[Medline]
  21. Archer S., Li T. T., Evans A. T., Britland S. T., Morgan H. Cell reactions to dielectrophoretic manipulations. Biochem. Biophys. Res. Commun., 257: 687-698, 1999.[CrossRef][Medline]
  22. Toikkanen S., Helin H., Isola J., Joensuu H. Prognostic significance of HER-2 oncoprotein expression in breast cancer: a 30-year follow-up. J. Clin. Oncol., 10: 1044-1048, 1992.[Abstract]
  23. Benz C. C., Scott G. K., Sarup J. C., Johnson R. M., Tripathy D., Coronado E., Shepard M. H., Osborne C. K. Estrogen-dependent, tamoxifen-resistant tumorigenic growth of MCF-7 cells transfected with HER2-neu. Breast Cancer Res. Treat., 24: 85-95, 1992.[CrossRef][Medline]
  24. Pierce J. H., Arnstein P., DiMarco E., Artip J., Kraus M. H., Lonardo F., DiFiore P. P., Aaronson S. A. Oncogenic potential of erbB-2 in human mammary epithelial cells. Oncogene, 6: 1189-1194, 1991.[Medline]
  25. De Gasperis G., Wang X-B., Yang J., Becker F. F., Gascoyne P. R. C. Automated electrorotation: dielectric characterization of living cells by real-time motion estimation. Meas. Sci. Technol., 9: 1-12, 1998.
  26. Gascoyne P. R. C., Becker F. F., Wang X-B. Numerical analysis of the influence of experimental conditions on the accuracy of dielectric parameters derived from electrorotation measurements. Bioelectrochem. Bioenerg., 36: 115-125, 1995.[CrossRef]
  27. Arnold W. M., Zimmerman U. Electrorotation: development of a technique for dielectric measurements on individual cells and particles. J. Electrostatics, 21: 151-191, 1988.
  28. Fuhr G., Glaser R., Hagedorn R. Rotation of dielectrics in a rotating electric high-frequency field. Model experiments and theoretical explanation of the rotation effect of living cells. Biophys. J., 49: 395-402, 1986.[Abstract/Free Full Text]
  29. Schnelle T., Muller T., Hagedorn R., Voight A., Fuhr G. Single micro electrode dielectrophoretic tweezers for manipulations of suspended cells and particles. Biochim. Biophys. Acta, 1428: 99-105, 1999.[Medline]
  30. Huang Y., Wang X-B., Becker F. F., Gascoyne P. R. C. Membrane changes associated with the temperature-sensitive P85gag-mos-dependent transformation of rate kidney cells as determined by dielectrophoresis and electrorotation. Biochim. Biophys. Acta, 1282: 76-84, 1996.[Medline]
  31. Hudziak R. M., Schlessinger J., Ullrich A. Increased expression of the putative p185 HER2 causes transformation and tumorigenesis of the NIH 3T3 cells. Proc. Natl. Acad. Sci. USA, 84: 7159-7163, 1987.[Abstract/Free Full Text]
  32. Hung M. C., Schechter A. L., Chevray P-Y. M., Stern D. F., Weinberg R. A. Molecular cloning of the neu gene: absence of gross structural alteration in oncogenic alleles. Proc. Natl. Acad. Sci. USA, 83: 261-264, 1986.[Abstract/Free Full Text]
  33. Coussens L., Yang-Feng T. L., Liao Y-C., Chen E., Gray A., McGrath J., Seeburg P. H., Libermann T. A., Schlessinger J., Francke U. Tyrosine kinase receptor with extensive homology to EGF receptor shares chromosomal location with neu oncogene. Science (Wash. DC), 230: 1132-1139, 1985.[Abstract/Free Full Text]
  34. Kiyokawa N., Yan D. H., Brown M. E., Hung M. C. Cell cycle-dependent regulation of p185neu: a relationship between disruption of this regulation and transformation. Proc. Natl. Acad. Sci. USA, 92: 1092-1096, 1995.[Abstract/Free Full Text]
  35. Buehler H., Bangemann N., Evers K., Becker C., Schaller G. Effective HER-2/neu diagnosis in breast cancer by a combination of immunohistochemistry and FISH. Proc. Am. Soc. Clin. Oncol., 19: 76a 2000.



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