1. ¹Institute of Immunology, University of Witten/Herdecke, Stockumer Strasse 10, 58448 Witten, Germany
2. ²Institute for Clinical Chemistry and Laboratory Medicine, Westfälische-Wilhelms-University of Münster, Albert-Schweitzer-Strasse 33, 48129 Münster, Germany
3. ³Department of Cellular and Molecular Medicine, Howard Hughes Medical Institute, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093-0686, USA

Correspondence: Dr T Dittmar, E-mail: thomasd@uni-wh.de

Received 30 July 2003; Revised 16 October 2003; Accepted 24 October 2003.

Abstract

Due to its pivotal role in the growth factor-mediated tumour cell migration, the adaptor protein phospholipase C-1 (PLC-1) is an appropriate target to block ultimately the spreading of EGFR/c-erbB-2-positive tumour cells, thereby minimising metastasis formation. Here, we present an approach to block PLC-1 activity by using protein-based PLC-1 inhibitors consisting of PLC-1 SH2 domains, which were fused to the TAT-transduction domain to ensure a high protein transduction efficiency. Two proteins were generated containing one PLC-1-SH2-domain (PS1-TAT) or two PLC-1-SH2 domains (PS2-TAT). PS2-TAT treatment of the EGFR/c-erbB-2-positive cell line MDA-HER2 resulted in a reduction of the EGF-mediated PLC-1 tyrosine phosphorylation of about 30%, concomitant with a complete abrogation of the EGF-driven calcium influx. In addition to this, long-term PS2-TAT treatment both reduces the EGF-mediated migration of about 75% combined with a markedly decreased time locomotion of single MDA-HER2 cells as well as decreases the proliferation of MDA-HER2 cells by about 50%. Due to its antitumoral capacity on EGFR/c-erbB-2-positive breast cancer cells, we conclude from our results that the protein-based PLC-1 inhibitor PS2-TAT may be a means for novel adjuvant antitumour strategies to minimise metastasis formation because of the blockade of cell migration and proliferation.