Inorganic sulfur reduces cell proliferation by inhibiting of ErbB2 and ErbB3 protein and mRNA expression in MDA-MB-231 human breast cancer cells

Dietary inorganic sulfur is the minor component in our diet, but some studies suggested that inorganic sulfur is maybe effective to treat cancer related illness. Therefore, this study aims to examine the effects of inorganic sulfur on cell proliferation and gene expression in MDA-MB-231 human breast cancer cells. MDA-MB-231 cells were cultured the absence or presence of various concentrations (12.5, 25, or 50 micromol/L) of inorganic sulfur. Inorganic sulfur significantly decreased proliferation after 72 h of incubation (P < 0.05). The protein expression of ErbB2 and its active form, pErbB2, were significantly reduced at inorganic sulfur concentrations of 50 micromol/L and greater than 25 micromol/L, respectively (P < 0.05). The mRNA expression of ErbB2 was significantly reduced at an inorganic sulfur concentration of 50 micromol/L (P < 0.05). The protein expression of ErbB3 and its active form, pErbB3, and the mRNA expression of ErbB3 were significantly reduced at inorganic sulfur concentrations greater than 25 micromol/L (P < 0.05). The protein and mRNA expression of Akt were significantly reduced at an inorganic sulfur concentration of 50 micromol/L (P < 0.05), but pAkt was not affected by inorganic sulfur treatment. The protein and mRNA expression of Bax were significantly increased with the addition of inorganic sulfur concentration of 50 micromol/L (P < 0.05). In conclusion, cell proliferation was suppressed by inorganic sulfur treatment through the ErbB-Akt pathway in MDA-MB-231 cells.

Inorganic sulfur reduces the motility and invasion of MDA-MB-231 human breast cancer cells

This study investigated the effects of inorganic sulfur on metastasis in MDA-MB-231 human breast cancer cells. MDA-MB-231 cells were cultured in the absence or presence of various concentrations (12.5, 25, or 50 micromol/L) of inorganic sulfur. Cell motility, invasion, and the activity and mRNA expression of matrix metalloproteases (MMPs) were examined. Numbers of viable MDA-MB-231 cells did not differ by inorganic sulfur treatment from 0 to 50 micromol/L within 48 h. Inorganic sulfur significantly decreased cell motility and invasion in the MDA-MB-231 cells in a dose-dependent manner (P < 0.05), as determined using a Boyden chamber assay and a Matrigel chamber. The activities of MMP-2 and MMP-9 were significantly reduced by inorganic sulfur in a dose-dependent manner (P < 0.05). The inorganic sulfur also significantly inhibited MMP-2 and MMP-9 expression in the cells (P < 0.05). These data suggest that inorganic sulfur can suppress cancer cell motility and invasion by inhibiting MMP-2 and MMP-9 activity and gene expression in MDA-MB-231 cells.