This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nagy, P. Articles by Jovin, T. M. Search for Related Content PubMed PubMed Citation Articles by Nagy, P. Articles by Jovin, T. M.

Decreased Accessibility and Lack of Activation of ErbB2 in JIMT-1, a Herceptin-Resistant, MUC4-Expressing Breast Cancer Cell Line

¹ Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; ² Department of Biophysics and Cell Biology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary; ³ Laboratory of Cancer Biology, Institute of Medical Technology, Tampere University and Tampere University Hospital, Tampere, Finland; and ⁴ Department of Cell Biology and Anatomy, University of Miami, School of Medicine, Miami, Florida

Requests for reprints: Thomas M. Jovin, Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, Germany 37077. Phone: 49-551-2011381; Fax: 49-551-2011467; E-mail: tjovin{at}gwdg.de.

Overexpression of erbB2 in breast tumors is associated with poor prognosis and is a target of receptor-oriented cancer therapy. Trastuzumab (Herceptin), a monoclonal antibody against a membrane-proximal epitope in the extracellular region of erbB2, shows a therapeutic effect against a fraction of erbB2-amplified breast tumors. Unfortunately, resistance to Herceptin is common, and its cause is as yet unclear. Here we investigated the properties of erbB2 in a Herceptin-resistant cell line, JIMT-1, established from a breast cancer patient showing erbB2 gene amplification and primary resistance to Herceptin. The expression profile of erbB proteins, Herceptin-induced erbB2 internalization, and down-regulation in JIMT-1 were similar to those in Herceptin-sensitive lines. However, the mean number of Herceptin Mab binding sites in JIMT-1 was 1/5 that of the expressed erbB2 molecules, although 5% to 10% of the cells showed a 10-fold higher Herceptin binding than the main population. Herceptin Fab and Mab 2C4, an antibody binding to an epitope in the ectodomain further removed from the membrane, bound more efficiently to JIMT-1 cells than Herceptin Mab, implying that erbB2 was partly masked. The expression of MUC4, a membrane-associated mucin that according to reports contributes to the masking of membrane proteins, was higher in JIMT-1 than in Herceptin-sensitive lines, and its level was inversely correlated with the Herceptin binding capacity of single cells. Knockdown of MUC4 expression by RNA interference increased the binding of Herceptin. Western blotting showed a low level of proteolytic processing, shedding, and tyrosine phosphorylation of erbB2 in JIMT-1. The latter finding may explain its Herceptin-resistant phenotype characterizing both the low and high Herceptin binding subpopulations. We conclude that masking of erbB2 in JIMT-1 leads to diminished Herceptin binding and isolation of erbB2 from its normal interaction and activation partners.

Key Words: erbB2/HER2 • breast cancer • MUC4 • RNA interference • trastuzumab/Herceptin resistance

This article has been cited by other articles:

				A. Sapino, F. Montemurro, C. Marchio, G. Viale, J. Kulka, M. Donadio, A. Bottini, G. Botti, A. P. dei Tos, A. Bersiga, et al. Patients with advanced stage breast carcinoma immunoreactive to biotinylated Herceptin(R) are most likely to benefit from trastuzumab-based therapy: an hypothesis-generating study Ann. Onc., December 1, 2007; 18(12): 1963 - 1968. [Abstract] [Full Text] [PDF]

				M. Barok, J. Isola, Z. Palyi-Krekk, P. Nagy, I. Juhasz, G. Vereb, P. Kauraniemi, A. Kapanen, M. Tanner, G. Vereb, et al. Trastuzumab causes antibody-dependent cellular cytotoxicity-mediated growth inhibition of submacroscopic JIMT-1 breast cancer xenografts despite intrinsic drug resistance Mol. Cancer Ther., July 1, 2007; 6(7): 2065 - 2072. [Abstract] [Full Text] [PDF]

				G Valabrega, F Montemurro, and M Aglietta Trastuzumab: mechanism of action, resistance and future perspectives in HER2-overexpressing breast cancer Ann. Onc., June 1, 2007; 18(6): 977 - 984. [Abstract] [Full Text] [PDF]

				A. P. Singh, P. Chaturvedi, and S. K. Batra Emerging Roles of MUC4 in Cancer: A Novel Target for Diagnosis and Therapy Cancer Res., January 15, 2007; 67(2): 433 - 436. [Abstract] [Full Text] [PDF]

				V. Pino, V. P. Ramsauer, P. Salas, C. A. C. Carraway, and K. L. Carraway Membrane Mucin Muc4 Induces Density-dependent Changes in ERK Activation in Mammary Epithelial and Tumor Cells: ROLE IN REVERSAL OF CONTACT INHIBITION J. Biol. Chem., September 29, 2006; 281(39): 29411 - 29420. [Abstract] [Full Text] [PDF]

				S. Tamada, H. Shibahara, M. Higashi, M. Goto, S. K. Batra, K. Imai, and S. Yonezawa MUC4 Is a Novel Prognostic Factor of Extrahepatic Bile Duct Carcinoma. Clin. Cancer Res., July 15, 2006; 12(14): 4257 - 4264. [Abstract] [Full Text] [PDF]

				J. M. du Manoir, G. Francia, S. Man, M. Mossoba, J. A. Medin, A. Viloria-Petit, D. J. Hicklin, U. Emmenegger, and R. S. Kerbel Strategies for Delaying or Treating In vivo Acquired Resistance to Trastuzumab in Human Breast Cancer Xenografts Clin. Cancer Res., February 1, 2006; 12(3): 904 - 916. [Abstract] [Full Text] [PDF]

				R. Nahta, L. X.H. Yuan, B. Zhang, R. Kobayashi, and F. J. Esteva Insulin-like Growth Factor-I Receptor/Human Epidermal Growth Factor Receptor 2 Heterodimerization Contributes to Trastuzumab Resistance of Breast Cancer Cells Cancer Res., December 1, 2005; 65(23): 11118 - 11128. [Abstract] [Full Text] [PDF]