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Objectives: Alterations of components in the Wnt signaling pathway have recently been suggested to play a role in ovarian tumorigenesis. Wnt 3a is a pathway ligand that activates the canonical Wnt pathway. Lymphoid enhancer-binding factor-1 (Lef-1) is a target gene and a β-catenin-dependent transcription activator in the pathway, stimulating in vitro invasion in breast cancer cell lines. Quantification of Wnt pathway throughput and Lef-1 expression in 1 normal and 3 ovarian cancer cell lines was undertaken.

Methods: Three histologically-distinct epithelial cell lines were analyzed: TOV-112D (endometrioid), TOV-21G (clear cell) and CAOV-3 (papillary serous). One cell line, TOV-112D, harbors a β-catenin gene mutation that activates Tcf/Lef-dependent transcription. The normal cell line was immortalized ovarian surface epithelium, IOSE. Wnt pathway activity was measured using firefly luciferase activity from a Tcf/Lef-responsive reporter (SuperTopFlash). The cell lines were analyzed using quantitative reverse transcriptase PCR using primers targeted for the β-catenin binding domain to measure Lef-1 mRNA levels.

Results: IOSE exhibited no endogenous Wnt pathway activity but did show weak activity when stimulated by Wnt 3a conditioned media or by co-culture with Wnt 3a producing cells. TOV-112D exhibited endogenous Wnt pathway activity and showed a statistically significant increase in Wnt pathway throughput when stimulated by Wnt 3a conditioned media (p=0.0456). When compared to IOSE, Lef-1 expression was higher in the TOV-112D cell line (p=0.0191) and lower in the CAOV3 (p=0.0019) and TOV-21G (p=0.0011) cell lines.

Conclusions: The study demonstrates significant differences in endogenous Wnt pathway throughput between the normal and the TOV-112D cell line, an endometrioid sub-type with mutated β-catenin. This cell line also expressed the highest Lef-1 mRNA levels. Lef-1 expression was also different between normal and cancer cell lines and between histologically-distinct forms of epithelial ovarian cancer. The transcriptional activity of Lef-1/β-catenin might play a role in ovarian tumorigenesis.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA