Silibinin Synergizes with Histone Deacetylase and DNA Methyltransferase Inhibitors in Upregulating E-cadherin Expression Together with Inhibition of Migration and Invasion of Human Non-small Cell Lung Cancer Cells

Abstract

Aggressive cancers in the epithelial-to-mesenchymal transition (EMT) phase are characterized by loss of cell adhesion, repression of E-cadherin, and increased cell mobility. Non-small cell lung cancer (NSCLC) differs in basal level of E-cadherin; predominantly exhibiting silenced expression due to epigeneticrelated modifications. Accordingly, effective treatments are needed to modulate these epigenetic events that in turn can positively regulate E-cadherin levels. Herein, we investigated silibinin, a natural flavonolignan with anticancer efficacy against lung cancer, either alone or in combination with epigenetic therapies to modulate E-cadherin expression in a panel of NSCLC cell lines. Silibinin combined with HDAC inhibitor Trichostatin A [TSA; 7-[4-(dimethylamino)phenyl]-N-hydroxy-4,6-dimethyl-7-oxohepta-2,4-dienamide] or DNMT inhibitor 59-Aza-deoxycytidine (Aza) significantly restored E-cadherin levels in NSCLC cells harboring epigenetically silenced E-cadherin expression. These combination treatments also strongly decreased the invasion/migration of these cells, which further emphasized the biologic significance of E-cadherin restoration. Treatment of NSCLC cells, with basal E-cadherin levels, by silibinin further increased the E-cadherin expression and inhibited their migratory and invasive potential. Additional studies showed that silibinin alone as well as in combination with TSA or Aza downmodulate the expression of Zeb1, which is a major transcriptional repressor of E-cadherin. Overall these findings demonstrate the potential of combinatorial treatments of silibinin with HDAC or DNMT inhibitor to modulate EMT events in NSCLC cell lines, leading to a significant inhibition in their migratory and invasive potentials. These results are highly significant, since loss of E-cadherin and metastatic spread of the disease via EMT is associated with poor prognosis and high mortalities in NSCLC.

miR‑145‑5p inhibits epithelial‑mesenchymal transition via the JNK signaling pathway by targeting MAP3K1 in non‑small cell lung cancer cells

“…E-cadherin has important functions in regulating cell-cell interactions (25). Epigenetic silencing of E-cadherin expression was observed in advanced NSCLC, and restoration of E-cadherin expression strongly suppressed the metastasis of cancer cells (7). Vimentin is specifically expressed in normal mesenchymal cells and overexpressed in lung cancer cells (26).…”

“…When EMT occurs, epithelial cells gradually transform into mesenchymal-like cells by losing their epithelial-associated functions and characteristics (5). Epigenetic downregulation of E-cadherin expression was observed in advanced NSCLC and restoration of E-cadherin expression strongly suppressed the invasion/migration of tumor cells (6,7). Several signaling pathways are involved in EMT in NSCLC, including TGF-β (8), Slug (9), Wnt/β-catenin/zinc finger E-box binding homeobox 1 signaling (10) and c-Jun N-terminal kinase (JNK) signaling (11).…”

Epigenetic silencing of Na,K-ATPase β1subunit geneATP1B1by methylation in clear cell renal cell carcinoma

“…In fact, it has been shown that DNMTs are induced during EMT in several cancers, including pancreatic cancer, non-small cell lung cancer, 37 and breast cancer. 38 There are no reports available on the influence of HIF-1α on DNMT activity; however multiple reports are available on the interaction between HIF-1α and histone demethylases JMJD1A, (demethylates dimethylated histone H3 lysine 9 (H3K9Me2) and JMJD2B (demethylates trimethylated H3K9).…”

High-Mobility Group Box 1 Mediates Epithelial-to-Mesenchymal Transition in Pulmonary Fibrosis Involving Transforming Growth Factor-β1/Smad2/3 Signaling

“…EMT is characterized by the loss of epithelial proteins, such as E-cadherin, and the acquisition of new mesenchymal markers, including a-smooth muscle actin (a-SMA), vimentin, and type I collagen (Col-I). It is a reversible process in which epithelial cells transform into cells with mesenchymal characteristics that contribute to ECM secretion in the progression of PF (Vittal et al, 2007;Kalluri and Weinberg, 2009;Mateen et al, 2013). Accumulated data support that injured AECs contribute greatly to the local activation of fibroblasts and myofibroblasts, and may also directly serve as a source of these cells via the EMT process (Kim et al, 2006;Liu et al, 2014;Vyas-Read et al, 2014).…”