Antisense-mediated exon skipping targeting EZH2 suppresses tumor growth in a xenograft mouse model of hepatocellular carcinoma.

Enhancer of zeste homolog 2 (EZH2) catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3), which promotes heterochromatin formation and gene silencing. Expression of EZH2 is frequently elevated in various malignancies, including hepatocellular carcinoma (HCC). Silencing of EZH2 has been pursued as a promising strategy to halt cancer progression. Here, we identified antisense oligonucleotides (ASOs) that efficiently silence EZH2 through promoting skipping of its exon 14, an exon encoding part of the essential CXC domain, increasing production of an internally shortened isoform that exerts dominant negative effect on the full-length EZH2. A lead ASO, hybridizing to an exonic splicing enhancer element bound by SRSF3, robustly promoted exon 14 skipping not only in cultured human HCC cell lines but also in mouse peripheral tissues after systemic administration, leading to dramatic reduction of EZH2 and H3K27me3 levels. The lead ASO potently inhibited HCC cell proliferation through multiple mechanisms including enhanced apoptosis, cell-cycle arrest, and reversed epithelial-mesenchymal transition, which is likely attributable to the suppression of diverse cancer-related pathways. In an orthotopic xenograft HCC mouse model, ASO treatment repressed tumor growth, improved tissue phenotype, and extended the median survival. Our data highlight therapeutic potential of the lead exon-skipping ASO in treating HCC.