The in vivo effects of knockdown of long non-coding RNA XIST on fibroid growth and gene expression.

The role of long non-coding RNAs in fibroid pathogenesis remains largely unexplored. In a previous study, we found elevated XIST (X-inactive specific transcript) levels in fibroids, which sponged miR-29c and miR-200c, leading to the overexpression of their target genes. This study aimed to assess the therapeutic potential of XIST downregulation in fibroid treatment. Ovariectomized SCID (severe combined immunodeficiency) mice were implanted with fibroid tumors transduced with XIST siRNA or a control via lentivirus. After 1 month, animals were sacrificed and the xenografts were removed for further analysis. XIST knockdown reduced tumor weight by 15% and increased miR-29c and miR-200c expression by 3.9-fold and 2.2-fold, respectively. The mRNA expression of miR-29c targets (COL3A1, TGF-β3, CDK2, SPARC) and miR-200c targets (CDK2, FN1, TDO2), as well as PRL, E2F1, and EZH2, was significantly decreased. Protein abundance of collagen, COL3A1, FN1, CDK2, SPARC, and EZH2 was also reduced. IHC analysis of xenograft sections using the markers of Ki67 for cell proliferation and cleaved caspase 3 for apoptosis showed decreased cell proliferation and no changes in apoptosis in the XIST knockdown xenografts. This analysis also revealed decreased collagen and E2F1 staining nuclei in the XIST knockdown xenografts. These results indicate that downregulation of XIST in fibroids has beneficial therapeutic effects, by reducing tumor growth and the expression of genes involved in cell proliferation, inflammation, and extracellular matrix regulation.