ABSTRACT
Gastrointestinal stromal tumor (GIST) is a refractory malignant tumor without satisfactory therapy. In recent years, aberrant gene methylation has been highlighted as an inducer for tumor progression. In this study, we explored whether enhancer of zeste homolog 2 (EZH2)-mediated paired box 8 (PAX8) methylation affects GIST development through regulation of Wnt4. A total of 50 cases of GIST tissues were collected and the human GIST cell lines were cultured. PAX8 methylation was examined using MS-PCR. Following loss- and gain-function approaches, GIST cell proliferation, migration, invasion, and apoptosis were examined by CCK-8 assay, Transwell assay and flow cytometry. The expression of proliferation related factors and apoptosis related factors was determined. Finally, xenograft tumors in nude mice were observed to examine in vivo tumorigenicity of GIST cells. Downregulated PAX8 and upregulated EZH2 expression was found in GIST tissues. Overexpression of PAX8 or suppression of PAX8 methylation using DNA methyltransferase inhibitor 5-Aza-dC inhibited the proliferation, migration, and invasion of GIST cells while promoting their apoptosis (diminished PCNA, Ki67 and Bcl-2, elevated Bax, and cleaved caspase-3). EZH2 promoted PAX8 methylation to inhibit its expression. Downregulated PAX8 decreased Wnt4 expression to accelerate GIST progression both in vitro and in vivo. Collectively, EZH2 inhibits PAX8 expression by promoting its methylation, which thus downregulates Wnt4 expression, thereby promoting the development of GIST.
Subject(s)
Enhancer of Zeste Homolog 2 Protein/metabolism , Gastrointestinal Stromal Tumors/genetics , Wnt4 Protein/metabolism , Animals , Disease Progression , Down-Regulation , Gastrointestinal Stromal Tumors/pathology , Humans , Methylation , Mice , Middle AgedABSTRACT
Long non-coding RNA is an endogenous non-coding RNA that has currently been proved to be an important player in cancer cell biology. In the present study, we investigated the biological role of PHACTR2-AS1 in tongue squamous cell carcinoma (TSCC). PHACTR2-AS1 was preferentially localized in the cytoplasm, and was notably upregulated in TSCC tissues. High PHACTR2-AS1 was correlated with tumour differentiation, metastatic clinical features, relapse and shortened survival time. Depletion of PHACTR2-AS1 did not affect TSCC cell viability and colony formation ability, whereas substantially inhibited cell migration and invasion in vitro and lung metastasis in vivo. Mechanistically, PHACTR2-AS1 could sponge miR-137 to increase Snail expression, resulting in triggering epithelial-mesenchymal transition process, thereby promoting TSCC cell metastasis. Taken together, our data for the first time elucidate the metastasis-promoting role of PHACTR2-AS1 in TSCC, hinting a new therapeutic target for metastatic TSCC patients.
