Expression of L-3-Phosphoserine Phosphatase Is Regulated by Reconstituted Basement Membrane Elisabeth Strunck, 1 Kirsten Frank, Marselina I. Tan, 2 and Gu ¨ nter Vollmer 3 Institut fu ¨ r Molekulare Medizin, Medizinische Universita ¨t zu Lu ¨ beck, Ratzeburger Allee 160, D-23538 Lu ¨ beck, Germany Received January 12, 2001 Reconstituted basement membrane (Matrigel) pro- motes differentiation of endometrial adenocarcinoma cells in vitro. However, little is known about the mo- lecular basis of these in vitro differentiation pro- cesses. Using differential display RT-PCR to search for potential molecular markers we screened for genes which respond to contact to basement membrane by alteration of expression levels. Here we report that the cDNA MT32 represents an mRNA with a time depen- dent biphasic response pattern to contact to basement membrane. Characterizing MT32 revealed that the se- quence of MT32 is identical to L-3-phosphoserine phos- phatase. PCR analysis of L-3-phosphoserine phospha- tase expression surprisingly revealed at least three variants of this enzyme. In summary, and in view of the literature, L-3-phosphoserine phosphatase and po- tential variants or family members represent molecu- lar markers to study regulation of gene expression by components of the extracellular matrix. In conclusion, L-3-phosphoserine phosphatase(s) may be important in endometrial carcinogenesis since this enzyme syn- thesizes important metabolic intermediates which serve both as building blocks for peptide synthesis and for signal transducing molecules. © 2001 Academic Press For the carcinogenesis of the endometrium, over the years a lot of evidence has been accumulated, that in addition to genetic factors, epigenetic factors significantly contribute to the pathogenesis of this organ. If applying the generally accepted three step model of carcinogene- sis—initiation, promotion and progression—to the carci- nogenesis of the endometrium, epigenetic factors partic- ularly contribute to the last two steps. Most prominantly hormones, particularly estrogens, and growth factors are believed to be potent tumor promotors and their action may lead to tumor progres- sion (1, 2). In contrast, the contribution of components of the extracellular matrix and their interaction with normal and malignant epithelial endometrial cells to the process of carcinogenesis is comparatively poorly understood. The composition of the stromal ECM changes during the process of carcinogenesis resulting e.g., in a high expression of tenascin-C in tumors which is not detectable in the corresponding normal tissue (3, 4). Expression of integrin cell adhesion is altered in endometrial adenocarcinoma with a reduced frequency of expression of the  3 subunit and an increased fre- quency of expression of the  6 subunit if compared to the normal tissue (5). However, nothing is known about potential functional consequences of alterations of either composition of components of the ECM or their cellular receptors. To elucidate functional consequences of cell matrix interactions on target cells and to understand their underlying molecular mechanisms molecular markers are needed. The aim of our study was to use differential display of mRNA (DD RT-PCR) to identify genes the expression of which is regulated by contact of cells to reconstituted basement membrane. In vitro we and others have demonstrated that ECM profoundly influ- ences cell shape, cellular differentiation (6 – 8) and gene expression (9, 10). Comparing mRNA expression pattern of endometrial adenocarcinoma cells which have been cultured on conventional cell culture plastic and of endometrial adenocarcinoma cells which were cultured on reconstituted basement membrane by dif- ferential gene expression studies we identified several cDNAs representing mRNA species which were either up- or down-regulated in response to contact to base- ment membrane (9). However, the sequences of most of these cDNAs showed no homology to known genes, which made it difficult to use them as marker mole- cules. Here we report on the identification of MT32, a 1 Present address: Experimentelle Ana ¨ sthesie, Zentrum fu ¨ r Kli- nische Forschung, Breisacher Str. 66, 79106 Freiburg, Germany. 2 Present address: Bandung Institute of Technology, Department of Biology, JL. Ganesa 10, Bandung 40132, West Java, Indonesia. 3 To whom correspondence and reprint requests should be ad- dressed at present address: Molekulare Zellphysiologie und Endokri- nologie, Institut fu ¨ r Zoologie, Technische Universita ¨ t Dresden, Momm- senstr. 13, D-01062 Dresden, Germany. Fax: +49-351-4631922. E-mail: Guenter.Vollmer@mailbox.tu-dresden.de. Biochemical and Biophysical Research Communications 281, 747–753 (2001) doi:10.1006/bbrc.2001.4403, available online at http://www.idealibrary.com on 747 0006-291X/01 $35.00 Copyright © 2001 by Academic Press All rights of reproduction in any form reserved.