Increased expression of the Zn-finger transcription factor BTEB1 in human endometrial cells is correlated with distinct cell phenotype, gene expression patterns, and proliferative responsiveness to serum and TGF-beta 1

Basic transcription element binding (BTEB, also designated BTEB1) protein i s a member of the Sp-family of GC-box binding transcription factors that ex hibit distinct patterns of expression in many cell types and tissues. A rol e for BTEB1 in the regulation of cell growth and gene transcription has bee n invoked, but little is known about the molecular mechanisms underlying th ese activities. The present study examined the functional consequences of h igh and low BTEB1 expression in the human endometrial carcinoma cell line H cc-1-A, by deriving stable clonal lines that expressed sense (S) and anti-s ense (As) rat BTEB1 constructs. Clonal S lines, with BTEB1 mRNA and protein levels higher than in corresponding parent (N) and As lines, displayed enh anced DNA synthesis upon (3)[H]-thymidine incorporation, in serum-containin g but not in serum-free medium, and increased cell cycle kinetics, concomit ant with the induction in expression of the genes for the cell cycle-associ ated components cyclin DI, PCNA, cyclin-dependent kinase (Cdk) inhibitor p2 1, and Cdk2. Compared to N and As lines, S lines also had diminished abilit y to grow in multi-layers and exhibited increased mRNA levels for plasminog en activator inhibitor-1 (PAT-1), secretory leukocyte protease inhibitor (S LP1), and tissue inhibitor of metalloproteinases (TIMP)-2. In serum-free me dium, S, but not N nor As lilies, had enhanced DNA synthesis with transform ing growth factor (TGF)-beta1, albeit all lines demonstrated similar respon ses to insulin-like growth factor-1 and to epidermal growth factor, respect ively. The higher DNA synthesis in S relative to N and As, lines upon exoge nous TGF-beta1 addition, was observed in concert with increased expression of cyclins D1 and E and p21, genes. Moreover, S and As lines had increased mRNA levels for TIMP-1, TIMP-2, PAI-1, and beta -catenin, and diminished SL PI and to a lesser extent, Cdk4 mRNA levels, with TGF-beta1 treatment. Thes e results suggest that BTEB1 may mediate cell growth, in part, by modulatin g gene expression levels of distinct cell cycle and growth-associated prote ins. The correlation between serum- and TGF-beta1 induction of DNA synthesi s with increased BTEB1 expression further suggests that BTEB1 may constitut e an important downstream regulatory component of various signaling pathway s utilized by serum-associated and other growth factors in endometrial epit helial cells. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.