Experimental Cell Research 180 (1989) 20-29 Retinoic Acid Induces a Specific Membrane Glycoprotein in Human Epithelial Cell Lines ODDMUND BAKKE*,‘*’ and TERJE ESPEVIKt *Biotechnology Group, SINTEF, Trondheim, and ‘Cell Research Laboratory, Inslitute of Cancer Research, University of Trondheim. Trondheim, Norway Retinoic acid (RA) inhibits growth, increases the cytokeratin content, and alters the cytoskeleton of the human cervical cell line NHIK 3025. Using RA-treated NHIK 3025 cells as immunogen we prepared murine monoclonal antibodies (IgGl) which recognized an RA-induced cell-surface antigen which could not be detected in untreated NHIK 3025 cells. Analysis of the Triton soluble proteins by SDS-gel electrophoresis and immunoblot- ting revealed that the cell-surface antigen is a I40-kDa glycoprotein (gpl40). gpl4O was also shown to be induced by RA in HeLa S3 cells and constitutively expressed in the human trophoblast cell line BeWo. gpl40 was also detected in other human epithelial cell lines, but not in human hematopoietic cells. Expression of gpl40 was induced in HeLa S3 cells by nanomolar concentrations of RI\. and in NHIK 3025 cells by micromolar amounts (I-10 @f). The glycoprotein was detectable 3-6 h following exposure to RA and its expression was reversible upon removal of RA from the medium. Our results indicate that gpl40 is a newly identified RA-inducible epithelial membrane glycoprotein which may represent a phenotypic differentiation marker for epithelial cells. 0 IYXY Academic RUS. IIK. Retinoids may induce biochemical and functional changes in epithelial cells and may play a vital role in normal differentiation and growth of epithelial tissues [1, 21. The retinoids also have anticarcinogenic activity in uiuo [3, 41 and inhibit proliferation of many cultured carcinoma cells [5]. In epithelial cell lines retinoids may induce a new phenotype including altered morphology and cytoskeleton and altered cell-surface structures 16, 71. Retinoic acid (RA) induces differentiation in vitro and it is the first morphogen identified in uiuo 181. Specific cytoplasmic binding proteins have long been known to exist [9], but their exact role has been a matter of controversy. Recently, a human nuclear RA-receptor and its DNA sequence were described [lo, II]. We have previously studied the effect of RA on the human cervical carcinoma cell line NHIK 3025 and found that RA is a growth inhibitor which causes a specific prolongation of the Gl phase, resulting in accumulation of cells in this phase [12, 131. RA alters the organization of the cytoskeleton and increases the accumulation of certain cytokerdtin lilaments suggesting an effect upon differcnti- ation [12-171. This led us to study whether RA induces specific surface antigens in NHIK 3025 cells. To address this issue, murine hybridomas secreting antibod- ies against RA-treated NHIK 3025 cells were prepared. In this report we describe a monoclonal antibody which recognizes a 140-kDa glycoprotcin induced by RA ’ To whom correspondence should be addressed at present address: European Molecular Biology Laboratory, Postfach 10.2209, 6900 Heidelberg, PKG. Copyright G 1989 by Academic Prcs. Inc. ,411 right\ of reproduction in any form rcscrvcd 0014~4%?7.‘119503.00 20