RAPID COMMUNICATION A. Kleber á R.W. Hartmann á J. Jose No effect of thromboxane A 2 on the attachment of tumor cell lines MDA MB 231, DU145, and U937 to the basement membrane in an in-vitro model Received: 25 June 2001 /Accepted: 10 July 2001 / Published online: 2 October 2001 Ó Springer-Verlag 2001 Abstract Purpose: A broad body of evidence indicates the involvement of P450 TxA 2 thromboxane A 2 syn- thetase) in tumor metastasis formation. A distinct function of the enzyme in this multistep process, how- ever, is still unknown. Therefore the eect of TxA 2 thromboxane A 2 ) on tumor cell adhesion to the base- ment membrane, a key event in metastasis formation, was investigated. Methods: A wide variety of compounds designed in our work group and identi®ed as P450 TxA 2 inhibitors were applied to several P450 TxA 2 -positive tumor cell lines to test their in¯uence on tumor cell ad- hesion. For this purpose an in-vitro basement membrane adhesion model with the matrix gel preparation Matrigel was used. Results: Most of the P450 TxA 2 inhibitors tested had no eect on cell adhesion. Although two compounds signi®cantly reduced tumor cell adhesion in a concentration-dependent manner, this was not related to P450 TxA 2 inhibition. Conclusion: These data indicate that TxA 2 might not be involved in the attachment of tumor cell lines to the basement membrane. Keywords P450 TxA 2 á Inhibitors á Metastasis á Tumor cell adhesion á Basement membrane Introduction Several lines of evidence strongly support the concept that TxA 2 contributes to metastasis. First, it has been reported that TxA 2 is increasingly produced in the tissue of metastatic lesions Castelli et al. 1989). Clinically, cancer patients with advanced diseases are characterized by a variety of thromboembolic disorders including thrombocytosis Grignani et al. 1986). Pharmacologi- cally, various P450 TxA 2 inhibitors and anticoagulants have demonstrated potent inhibitory eects on experi- mental metastasis Yokoyama et al. 1995). As these data were collected either in situ in humans or in vivo in an- imals, no dierentiation of the role of P450 TxA 2 in the complex process of metastasis was possible. P450 TxA 2 is a key enzyme of the arachidonic acid cascade and con- verts prostaglandin H 2 into TxA 2 , malondialdehyde, and heptadecanoic acid in a 1:1:1 ratio. The prostanoid TxA 2 is a potent inducer of platelet aggregation and a con- strictor of vascular and respiratory smooth muscles. The ability of a tumor cell to metastasize is deter- mined in part by its adhesive interactions with other cells and components of the extracellular matrix. Because of the multistep nature of the metastatic cascade it is ap- propriate to focus investigations on key positions. One critical event in the metastatic process is the adhesion to and the invasion through the basement membrane at the metastatic site. Therefore the object of this study was the investigation of the implication of TxA 2 in tumor cell adhesion to the basement membrane. In our group the rational design of P450 TxA 2 in- hibitors resulted in a wide variety of substrate mimetics, that inhibited TxA 2 formation in thrombocytes Leder- gerber et al. 1997; Hartmann and Frotscher 1999; Jacobs et al. 2000). Several compounds with low IC 50 values were tested for their ability to inhibit the adhesion of P450 TxA 2 -positive tumor cells MDA MB 231, DU145, and U937) to the basement membrane. For this purpose we used an in vitro model with the solubilized basement membrane preparation Matrigel Kleber et al. 2000). Materials and methods Cell lines U937 promonocytic human cell line) and DU145 epithelial-like, adherent cell line, established from a prostate adenocarcinoma me- tastasis) were obtained from the DSMZ Braunschweig, Germany). J Cancer Res Clin Oncol 2001) 127: 751±754 DOI 10.1007/s004320100283 A. Kleber á R.W. Hartmann á J. Jose &) Pharmazeutische und Medizinische Chemie, Naturwissenschaftlich-Technische FakultaÈt III, UniversitaÈt des Saarlandes, P.O. Box 151150, 66041 SaarbruÈcken, Germany E-mail: j.jose@rz.uni-sb.de Tel.: +49-681-3022294 Fax: +49-681-3024386