Overexpression of ErbB2 enhances ethanol-stimulated intracellular signaling and invasion of human mammary epithelial and breast cancer cells in vitro

Abstract

Both epidemiological and experimental studies indicate that ethanol is a tumor promoter and may promote metastasis of breast cancer. However, the molecular mechanisms underlying ethanol-mediated tumor promotion remain unknown. Overexpression of ErbB proteins in breast cancer patients is generally associated with poor prognosis. The ErbB proteins are a family of receptor kinases that include four closely related members: epidermal growth factor receptor (EGFR/ErbB1), ErbB2/neu, ErbB3, and ErbB4. Particularly, ErbB2 plays a pivotal role in ErbB-mediated activities. Here we demonstrated that amplification of ErbB2 expression sensitized a specific cellular response to ethanol. Human breast cancer cells or mammary epithelial cells with a high expression of ErbB2 exhibited an enhanced response to ethanol-stimulated cell invasion in vitro. Ethanol also stimulated cell proliferation; however, this stimulation was independent of ErbB2 levels. Ethanol triggered divergent intracellular signaling among cells expressing different ErbB2 levels. In the cells overexpressing ErbB2, ethanol was more effective in the activation of c-Jun NH 2 terminal protein kinases (JNKs) and p38 mitogen-activated protein kinase (p38 MAPK) as well as the induction of reactive oxygen species (ROS) than the cells with normal ErbB2 expression. Blockage of either JNKs or p38 MAPK activation eliminated ethanol-mediated cell invasion. In contrast, the reduction of hydrogen peroxide concentration by catalase exposure had little effect on ethanolinduced cell invasion. These results indicated that ethanolinduced cell invasion was primarily mediated by JNKs and p38 MAPK, whereas the involvement of ROS formation might be minimal. Our study suggests that overexpression of ErbB2 may augment ethanol-elicited signaling and promote ethanol-stimulated tumor metastasis.

Ethanol‐induced in vitro invasion of breast cancer cells: The contribution of MMP‐2 by fibroblasts

“…For example, it is shown that the status of growth factor receptor and intracellular signaling components determine cellular sensitivity to ethanol. 21,41 Despite the differential sensitivity, these cells respond to ethanol in a similar pattern. Furthermore, selective inhibitors of MMP-2 (SB-3CT and OA-Hy) eliminate ethanolstimulated invasion.…”

“…60,61 ErbB2 has been shown to facilitate the invasion of breast cancer cells in vitro and in vivo. 21,[63][64][65] The status of ErbB2 expression in a given cell is critical in determining the cellular response to various exogenous stimuli. 21,66 -68 Overexpression of ErbB2 could result in autophosphorylation, which initiates intracellular signaling; it is suggested that ErbB2 controls stroma-toepithelium crosstalk.…”

“…Solubilized cells were centrifuged, proteinaceous supernatant was collected, and protein concentrations in the conditioned medium and cell lysates were determined. 21 …”

“…These epidemiologic results are supported by experimental studies using animal models and cell culture systems, which show that ethanol promotes mammary tumorigenesis and stimulates proliferation as well as invasion of breast cancer cells. [15][16][17][18][19][20][21] The molecular mechanisms underlying ethanol action, however, remain to be determined.Abnormal communication between the mammary epithelium and stromal cells promotes tumorigenesis and development of breast carcinomas. 22 Cancer-stroma interaction is mediated at least in part through the matrix metalloproteinases (MMPs).…”

Roles of Leptin in Cancer Progression

“…Binding of ligand to these receptors induces stimulation of the ErbB tyrosine kinase receptors. Among the ErbB family members, ErbB2 is most directly related to the tumorigenesis of breast cancer (Ma et al, 2003). Approximately 30% of breast tumors show HER2 over-expression, which is often associated with a more aggressive, metastatic phenotype and worse prognosis of breast cancer (Slamon et al, 1987;Yarden, 2001).…”