A functional comparison between the HER2high/HER3 and the HER2low/HER3 dimers on heregulin-beta1-induced MMP-1 and MMP-9 expression in breast cancer cells

Overexpression of HER2 correlates with more aggressive tumors and increased resistance to cancer chemotherapy. However, a functional comparison between the HER2high/HER3 and the HER2low/HER3 dimers on tumor metastasis has not been conducted. Herein we examined the regulation mechanism of heregulin-beta1 (HRG)-induced MMP-1 and -9 expression in breast cancer cell lines. Our results showed that the basal levels of MMP-1 and -9 mRNA and protein expression were increased by HRG treatment. In addition, HRG-induced MMP-1 and -9 expression was significantly decreased by MEK1/2 inhibitor, U0126 but not by phosphatidylinositol 3-kinase (PI-3K) inhibitor, LY294002. To confirm the role of MEK/ERK pathway on HRG-induced MMP-1 and -9 expression, MCF7 cells were transfected with constitutively active adenoviral-MEK (CA-MEK). The level of MMP-1 and -9 expressions was increased by CA-MEK. MMP-1 and -9 mRNA and protein expressions in response to HRG were higher in HER2 overexpressed cells than in vector alone. The phosphorylation of HER2, HER3, ERK, Akt, and JNK were also significantly increased in HER2 overexpressed MCF7 cells compared with vector alone. HRG-induced MMP-1 and -9 expressions were significantly decreased by lapatinib, which inhibits HER1 and HER2 activity, in both vector alone and HER2 overexpressed MCF7 cells. Finally, HRG-induced MMP-1 and MMP-9 expression was decreased by HER3 siRNA overexpression. Taken together, we suggested that HRG-induced MMP-1 and MMP-9 expression is mediated through HER3 dependent pathway and highly expressed HER2 may be associated with more aggressive metastasis than the low expressed HER2 in breast cancer cells.

Cholesterol, a Major Component of Caveolae, Down-regulates Matrix Metalloproteinase-1 Expression through ERK/JNK Pathway in Cultured Human Dermal Fibroblasts

BACKGROUND: Cholesterol is a major component of specialized membrane microdomains known as lipid rafts or caveolae, which modulate the fluidity of biological membranes. Membrane cholesterol therefore plays an important role in cell signaling and vesicular transport. OBJECTIVE: In this study, we investigated the effects of cholesterol on matrix metalloproteinase-1 (MMP-1) expression in human dermal fibroblasts. METHODS: MMP-1 mRNA and protein expression were determined by RT-PCR and Western blotting, respectively. AP-1 DNA binding activity was detected by electrophoretic mobility shift assays. The amount of cholesterol was analyzed by cholesterol assay kit. RESULTS: We observed that MMP-1 mRNA and protein expression was dose-dependently decreased by cholesterol treatment. In contrast, cholesterol depletion by a cholesterol depletion agent, methyl-beta-cyclodextrin (M beta CD) in human dermal fibroblasts, increased MMP-1 mRNA and protein expression in a dose-dependent manner. Also, we investigated the regulatory mechanism of M beta CD-induced MMP-1 expression: cholesterol depletion by M beta CD, activated ERK1/2 and JNK, but not p38 MAPK cascade, and it also significantly increased c-Jun phosphorylation, c-Fos expression and activator protein-1 binding activity. Furthermore, the inhibition of ERK or JNK with specific chemical inhibitors prevented M beta CD-induced MMP-1 expression, which indicates that ERK and JNK play an important role in cholesterol depletion-mediated MMP-1 induction. In addition, M beta CD-induced phosphorylation of ERK and JNK and MMP-1 expression were suppressed by cholesterol repletion. CONCLUSION: Our results suggest that cholesterol regulates MMP-1 expression through the control of ERK and JNK activity in human dermal fibroblasts.