We ne t investigated the possible regulation of E cadherin, N cadherin, and vimentin e pression by SIRT1, by using siRNA oligonucleotides to knock down SIRT1 e pres sion in HOK cell lines, and found either that SIRT1 silencing clearly down regulated E cadherin e pression. Addition ally, the deletion of SIRT1 led to significantly increased N cadherin and vimentin e pression in knockdown HOK cells. A similar reciprocal relationship was ob served in the case of SIRT1 overe pression in OECM1 cells, which showed increased E cadherin e pression. Moreover, we also determined the e pression of certain mesenchymal markers important for EMT. Transfection of OSCC cells with an SIRT1 e pression vector resulted in SIRT overe pression which subsequently reduced the e pression of the mesenchy mal proteins N cadherin and vimentin.

Together, these data indicated that SIRT1 may play a role in regulating epithelial and mesenchymal protein e pression. SIRT1 represses e pression of MMP7 in OSCC cells Similar to the metastatic mechanism of other cancers, oral cancer metastasis requires an e tensive remodeling and degradation of the e tracellular matri , partially via increased e pression of matri metalloproteinases. MMP7 e pression has been significantly correlated with oral cancer metastasis and EMT, which suggests that the SIRT1 overe pression might affect MMP7 e pression in OSCCs. We thus e amined the effect of transiently e pressed SIRT1 on OSCC cell lines by using a GFP tagged SIRT1 e pressing vector. We found that MMP7 transcription and translation were significantly decreased in SIRT1 overe pressing cells compared with their levels in control cells.

We also compared the enzymatic activity of MMP7 in SIRT1 overe pressing and silencing OSCC cells. When MMP7 activity was assayed by casein zymography, the activity in the media from SIRT1 overe pressing OECM1 cells was significantly lower than that in media from mock transfected cells. In contrast, SIRT1 silen cing produced a significant increase in MMP7 activity. This activity change is probably due to the difference in the protein levels, as determined by ELISA and immunoblotting with anti MMP7 antibody. The levels of MMP7 secreted into the media of OSCC cell lines were also estimated by ELISA at 48 h after trans fection with a SIRT1 e pression vector or siSIRT1.

We found that MMP7 secretion by SIRT1 overe pressing OSCC cells was significantly suppressed as compared with secretion Entinostat by mock transfected cells. In contrast, SIRT1 silencing in oral cancer cells resulted in a significant induction of MMP7 secretion. A similar result was seen in western blot e periments, where MMP7 secretion was significantly suppressed by e ogenously produced overe pression of SIRT1 in both OSCC cell lines, whereas repression of SIRT1 by SIRT1 silencing increased MMP7 secretion.