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- Chen, Min-Wei, et al.
(författare)
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H3K9 histone methyltransferase G9a promotes lung cancer invasion and metastasis by silencing the cell adhesion molecule Ep-CAM
- 2010
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Ingår i: Cancer Research. - : American Association for Cancer Research. - 0008-5472 .- 1538-7445. ; 70:20, s. 7830-7840
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Tidskriftsartikel (refereegranskat)abstract
- G9a is a mammalian histone methyltransferase that contributes to the epigenetic silencing of tumor suppressor genes. Emerging evidence suggests that G9a is required to maintain the malignant phenotype, but the role of G9a function in mediating tumor metastasis has not been explored. Here, we show that G9a is expressed in aggressive lung cancer cells, and its elevated expression correlates with poor prognosis. RNAi-mediated knockdown of G9a in highly invasive lung cancer cells inhibited cell migration and invasion in vitro and metastasis in vivo. Conversely, ectopic G9a expression in weakly invasive lung cancer cells increased motility and metastasis. Mechanistic investigations suggested that repression of the cell adhesion molecule Ep-CAM mediated the effects of G9a. First, RNAi-mediated knockdown of Ep-CAM partially relieved metastasis suppression imposed by G9a suppression. Second, an inverse correlation between G9a and Ep-CAM expression existed in primary lung cancer. Third, Ep-CAM repression was associated with promoter methylation and an enrichment for dimethylated histone H3K9. G9a knockdown reduced the levels of H3K9 dimethylation and decreased the recruitment of the transcriptional cofactors HP1, DNMT1, and HDAC1 to the Ep-CAM promoter. Our findings establish a functional contribution of G9a overexpression with concomitant dysregulation of epigenetic pathways in lung cancer progression.
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| 2. |
- Cha, Shih-Ting, et al.
(författare)
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MicroRNA-519c suppresses hypoxia-inducible factor-1alpha expression and tumor angiogenesis.
- 2010
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Ingår i: Cancer Research. - : American Association for Cancer Research. - 0008-5472 .- 1538-7445. ; 70:7, s. 2675-2685
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia-inducible factor-1alpha (HIF-1alpha) is widely considered to be one of the key regulators of tumor angiogenesis. The upstream regulation is complex and involves several growth factors, cytokines, and hypoxia. Herein, we have identified miR-519c as a hypoxia-independent regulator of HIF-1alpha, acting through direct binding to the HIF-1alpha 3' untranslated region and leading to reduced tumor angiogenesis. Overexpression of miR-519c resulted in a significant decrease of HIF-1alpha protein levels and reduced the tube formation of human umbilical vein endothelial cells; similarly, antagomir inhibition of miR-519c increased the level of HIF-1alpha protein and enhanced angiogenic activity, suggesting an important role of miR-519c in HIF-1alpha-mediated angiogenesis. Consistent with the overexpression of miR-519c in cancer patients with better prognosis, mice injected with miR-519c-overexpressing cells exhibited dramatically reduced HIF-1alpha levels, followed by suppressed tumor angiogenesis, growth, and metastasis. In addition, we found that hepatocyte growth factor (HGF), a known HIF-1alpha inducer, reduced the miR-519c levels through an Akt-dependent pathway. This regulation was posttranscriptional and may be mediated by suppression of miR-519c maturation. Taken together, our findings provide the first evidence that miR-519c is a pivotal regulator of tumor angiogenesis and that microenvironmental HGF contributes to regulating miR-519c biogenesis in cancer cells.
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