Role of SIRT1 in regulation of epithelial-to-mesenchymal transition in oral squamous cell carcinoma metastasis

Abstract

BackgroundThe epithelial-to-mesenchymal transition (EMT) process results in a loss of cell-cell adhesion, increased cell mobility, and is crucial for enabling the metastasis of cancer cells. Recently, the enzyme SIRT1 has been implicated in a variety of physiological processes; however, its role in regulating oral cancer metastasis and EMT is not fully elucidated. Here, we propose a mechanism by which the enzyme sirtuin1 (SIRT1) regulates the EMT process in oral cancer by deacetylating Smad4 and repressing the effect of TGF-β signaling on matrix metalloproteinase-7 (MMP7).MethodsThe roles of SIRT1 in tumor cell migration/invasion and metastasis to the lungs were investigated using the Boyden chamber assay and orthotopic injections, respectively. RNA interference was used to knockdown either SIRT1 or Smad4 expression in oral squamous cell carcinoma (OSCC) cell lines. Immunoblotting, zymographic assays, and co-immunoprecipitation were used to examine the effects of SIRT1 overexpression on MMP7 expression and activity, as well as on SIRT1/ Smad4 interaction.ResultsWe found that compared with normal human oral keratinocytes (HOKs), SIRT1 was underexpressed in OSCC cells, and also in oral cancer tissues obtained from 14 of 21 OSCC patients compared with expression in their matched normal tissues. Overexpression of SIRT1 inhibited migration of OSCC cells in vitro, as well as their metastasis to the lung in vivo. Furthermore, up-regulation of SIRT1 in metastatic OSCCs significantly inhibited the migration and invasion abilities of OSCC cells, while concomitantly increasing the expression of E-cadherin, and decreasing the expressions of mesenchymal markers. We also identified Smad4, a TGF-β-activated transcription factor, as a direct target protein for SIRT1. Overexpression of SIRT1 in OSCC cells led to decreased levels of acetylated Smad4, and inhibition of TGF-β-induced signaling. By associating and deacetylating Smad4, SIRT1 enzyme can influence MMP7 expression, MMP enzyme activity, and consequently, cell migration, invasion, and tumor metastasis in OSCCs.ConclusionsThese findings provide a valuable insight into the potential role of the SIRT1 enzyme in regulating cell migration and invasion in oral squamous cell carcinoma. Our findings suggest the SIRT1/Smad4/MMP7 pathway as a target for oral cancer driven by EMT.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-254) contains supplementary material, which is available to authorized users.

Overexpression of tumor suppressor gene ZNF750 inhibits oral squamous cell carcinoma metastasis

“…Despite previous studies reporting the role of ZNF750 in epidermal differentiation (7,10,17), the role of ZNF750 in OSCC has not yet been documented. To understand the potential anticancer effects of ZNF750 on OSCC, the role of ZNF750 in cell proliferation, differentiation, invasion and migration was investigated.…”

“…A previous study indicated that normal expression of ZNF750 leads to reduced expression of the progenitor gene MMP28, and increased expression of the differentiation genes LCE3A and SPRR1a mRNA in primary human undifferentiated keratinocytes (7). Loss of ZNF750 has been reported to result in impaired differentiation and enhanced proliferation of cancer cells (8).…”

“…Epidermal differentiation involves the repression of progenitor genes, which participate in cell proliferation and adhesion to the underlying basement membrane (7). A loss in cell-cell adhesion and an increase in cell motility are prerequisites for cancer metastasis (7).…”

“…It is an essential regulator of epidermal differentiation; it binds and activates the epidermal differentiation genes, including late cornified envelope 3A (LCE3A) and small proline-rich protein 1A (SPRR1a), and represses epidermal progenitor genes, including matrix metalloproteinase (MMP) 28 (6). Epidermal differentiation involves the repression of progenitor genes, which participate in cell proliferation and adhesion to the underlying basement membrane (7). A loss in cell-cell adhesion and an increase in cell motility are prerequisites for cancer metastasis (7).…”

SIRT1 promotes the proliferation and metastasis of human pancreatic cancer cells

“…EMT could dissolve the cell-cell junctions between non-motile cells and convert them into individual, motile mesenchymal cells by loss or downregulation of cell-cell adhesion molecules, such as E-cadherin, and many studies have suggested the role of SIRT1 in regulating EMT in various cancers. 15,16 Our finding shows that knockdown SIRT1 expression could significantly reduce the vimentin expression and restored E-cadherin expression.…”