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 Fukazawa, H. Articles by Uehara, Y. Search for Related Content PubMed PubMed Citation Articles by Fukazawa, H. Articles by Uehara, Y.

Departments of ¹ Bioactive Molecules and ² Safety Research on Blood and Biologics, National Institute of Infectious Diseases, Tokyo, Japan

Requests for reprints: Hidesuke Fukazawa, Department of Bioactive Molecules, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan. Phone: 81-3-5285-1111; Fax: 81-3-5285-1272. E-mail: fukazawa{at}nih.go.jp

Loss of contact with substratum triggers apoptosis in many normal cell types, a phenomenon termed anoikis. We reported previously that mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitors induced apoptosis in nonanchored MDA-MB231 and HBC4 human breast cancer cells, whereas anchored cells remained viable. Here, we report that activation of the BH3-only protein BimEL is the major mechanism for induction of anoikis sensitivity by MEK inhibitors in MDA-MB231 and HBC4 cells. On treatment with MEK inhibitors, BimEL in MDA-MB231 and HBC4 cells rapidly increased, irrespective of the state of anchorage. However, it translocated to mitochondria only in nonanchored cells, explaining why attached cells remain viable. MDA-MB231 and HBC4 cells had exceedingly low basal levels of BimEL compared with other breast cancer cells, suggesting that maintenance of low BimEL amount is important for survival of these cells. MEK inhibitors also induced the electrophoretic mobility shift of BimEL, indicative of reduced phosphorylation. In vitro, BimEL was phosphorylated by extracellular signal-regulated kinase on Ser⁶⁹, which resides in the BimEL-specific insert region. Using phosphospecific antibody against this site, we show that this residue is actually phosphorylated in cells. We also show that phosphorylation of Ser⁶⁹ promotes ubiquitination of BimEL. We conclude that MEK inhibitors sensitize MDA-MB231 and HBC4 cells to anoikis by blocking phosphorylation and hence degradation of BimEL, a mechanism that these cells depend on to escape anoikis.

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.

Received 5/26/04; revised 8/ 3/04; accepted 8/11/04.

This article has been cited by other articles:

				W. Zhang, G. Z. Cheng, J. Gong, U. Hermanto, C. S. Zong, J. Chan, J. Q. Cheng, and L.-H. Wang RACK1 and CIS Mediate the Degradation of BimEL in Cancer Cells J. Biol. Chem., June 13, 2008; 283(24): 16416 - 16426. [Abstract] [Full Text] [PDF]

				V. Labi, M. Erlacher, S. Kiessling, C. Manzl, A. Frenzel, L. O'Reilly, A. Strasser, and A. Villunger Loss of the BH3-only protein Bmf impairs B cell homeostasis and accelerates {gamma} irradiation-induced thymic lymphoma development J. Exp. Med., March 17, 2008; 205(3): 641 - 655. [Abstract] [Full Text] [PDF]

				N. Uehara, Y. Matsuoka, and A. Tsubura Mesothelin Promotes Anchorage-Independent Growth and Prevents Anoikis via Extracellular Signal-Regulated Kinase Signaling Pathway in Human Breast Cancer Cells Mol. Cancer Res., February 1, 2008; 6(2): 186 - 193. [Abstract] [Full Text] [PDF]

				N. T. Woods, H. Yamaguchi, F. Y. Lee, K. N. Bhalla, and H.-G. Wang Anoikis, Initiated by Mcl-1 Degradation and Bim Induction, Is Deregulated during Oncogenesis Cancer Res., November 15, 2007; 67(22): 10744 - 10752. [Abstract] [Full Text] [PDF]

				S. N. Anderson, D. L. Towne, D. J. Burns, and U. Warrior A High-Throughput Soft Agar Assay for Identification of Anticancer Compound J Biomol Screen, October 1, 2007; 12(7): 938 - 945. [Abstract] [PDF]