Extracellular matrix (ECM) activates β-catenin signaling in uterine fibroids

Recent studies showed that genetic aberrations in the MED12 gene, probably through the canonical WNT/beta-catenin pathway, lead to the pathogenesis of uterine fibroids. However, a comprehensive analysis of the WNT pathway in MED12-mutated and MED12-wildtype fibroids has not been performed. The objective of this study was to determine the status of the WNT pathway in human fibroids. We performed Sanger sequencing to define the MED12 mutational status of fibroids and normal myometrium samples. qPCR arrays were carried out to determine the status of the WNT signaling pathway in MED12-mutated and MED12-wild-type fibroids. Liquid chromatography-mass spectrometry (LC-MS), Western blotting and immunohistochemistry were used to monitor the expression of beta-catenin. We showed that beta-catenin expression was increased in fibroids compared to the adjacent myometrium samples. However, beta-showed the greatest differences in expression between fibroids and controls. WIF1, a WNT inhibitor, was identified as the most significantly upregulated gene in fibroids. We cultured primary fibroid cells on hydrogels of known stiffness to decipher the influence of biomechanical cues on beta-catenin expression and revealed increased levels of beta-catenin when cells were cultured on a stiffer surface. In conclusion, our data showed that beta-catenin expression in fibroids occurs independently of MED12 mutations. Biomechanical changes upregulate beta-catenin expression in fibroids, providing an attractive avenue for developing new treatments for this disease.