The dynamic interactions between tumor cells and their corresponding microenvironment play an important role in carcinogenesis. Fibroblasts are a dominant feature within a tumor stroma and have undergone a “reprogramming” to become cancer-activated fibroblasts (CAFs). In our study we established primary cell cultures of fibroblasts from matched pairs of normal human endometrium and endometrial cancer tissues and analyzed the differential expressions of mRNA and microRNA. We found that the WNT pathway was activated in CAFs and confirmed these results via Topflash luciferase reporter assays. Wingless-type (WNT) proteins are a highly conserved family of secreted glycoproteins that have been implicated in the carcinogenesis of many cancers. We demonstrated that one of the reasons for this WNT pathway activation was the methylation-dependent silencing of the secreted frizzled-related protein 4 (SFRP4), an antagonist to the WNT signaling pathway.

An additional reason for WNT pathway activation was found in the microRNA analysis. These experiments showed downregulation of miR-148a, which is a predicted regulator of the founder member of the WNT family, WNT1. We observed that CAFs have increased WNT1 protein expression in three of the five endometrial cancer CAFs. We confirmed that miR-148a directly targets WNT1 by cloning the WNT1 3'UTR into a luciferase reporter construct and showed that co-transfection with miR-148a results in a decrease of luciferase activity. When mutations to the miR-148a binding sites were introduced into the same luciferase reporter construct, the downregulation of luciferase activity by miR-148a was prevented. We conclude that the observed activation of the WNT pathway in endometrial cancer CAFs may be regulated by the miR-148a and contribute to the progression of the endometrial cancer tumorigenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1430.