Reconstituted basement membrane (Matrigel) promotes differentiation of endometrial adenocarcinoma cells in vitro. However, little is known about the molecular basis of these in vitro differentiation processes. 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 dependent biphasic response pattern to contact to basement membrane. Characterizing MT32 revealed that the sequence of MT32 is identical to L-3-phosphoserine phosphatase. PCR analysis of L-3-phosphoserine phosphatase expression surprisingly revealed at least three variants of this enzyme. In summary, and in view of the literature, L-3-phosphoserine phosphatase and potential variants or family members represent molecular 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 synthesizes important metabolic intermediates which serve both as building blocks for peptide synthesis and for signal transducing molecules.