Nicotine promotes lymph node metastasis and cetuximab resistance in head and neck squamous cell carcinoma.

Epidermal growth factor (EGF) is overexpressed in many cancers and is associated with worse prognosis. EGF binds to its cell surface receptor (EGFR), which induces EGFR phosphorylation. Phosphorylated EGFR (p­EGFR) is translocated into the nucleus, which increases cancer cell activity. Nicotine, which is one of the main components of tobacco, is absorbed through pulmonary alveoli and mucosal epithelia in the head and neck region by smoking and moves into the blood. Nicotine in blood binds to nicotinic acetylcholine receptor (nAChR) in the central nervous system and serves a crucial role in tobacco addiction. Although nAChR localization is thought to be limited in the nervous system, nAChR is present in a wide variety of non­neuronal cells, including cancer cells. Recent studies suggest that nicotine contributes to the metastasis and resistance to anti­cancer drugs of various cancer cells. However, it remains unknown whether head and neck squamous cell carcinoma (HNSCC) cells can utilize nicotine­nAChR signaling to metastasize and acquire resistance to anti­cancer drugs, even though the mucosal epithelia of the head and neck region are the primary sites of exposure to tobacco smoke. To the best of our knowledge, the present study is the first to demonstrate the role of nicotine in metastasis and anti­EGFR­therapy resistance of HNSCC. The present findings demonstrated that nicotine increased proliferation, migration, invasion, p­EGFR nuclear translocation and protein kinase B (Akt) phosphorylation in HNSCC cells. It was also demonstrated that nicotine restored cetuximab­inhibited proliferation, migration and invasion of HNSCC cells. Finally, an in vivo experiment revealed that nicotine increased lymph node metastasis of xenografted tumors, whereas an nAChR inhibitor suppressed lymph node metastasis and p­EGFR nuclear localization of xenografted tumors. Taken together, these results demonstrated that nicotine induced nuclear accumulation of p­EGFR, and activation of Akt signaling. These signaling pathways elevated the activities of HNSCC cells, causing lymph node metastasis and serving a role in cetuximab resistance.

Induction of MMP-13 expression in bone-metastasizing cancer cells by type I collagen through integrin α1ß1 and α2ß1-p38 MAPK signaling.

BACKGROUND: Breast cancer cells frequently metastasize to the skeleton and produce and secrete proteinases, such as matrix metalloproteinase-13 (MMP-13), which promote destruction of the bone matrix. However, the mechanism of MMP-13 expression induced in areas of bone metastasis is unknown. Here, the interaction between tumors and type I collagen in bone metastasis was investigated. MATERIALS AND METHODS: A mouse model of bone metastasis was prepared by inoculating mice with suspensions of cells of the human metastatic breast cancer cell line MDA-MB-231 via the left cardiac ventricle. MMP-13 expression was examined by immunohistochemical, Western blot, and real-time RT-PCR analyses. RESULTS: MMP-13 expression was highly up-regulated in MDA-MB-231 cells, and attachment of these cells to type I collagen and the induction of MMP-13 were down-regulated by treatment with integrin α1, α2 or ß1 neutralizing antibodies. The attachment of MDA-MB-231 cells to type I collagen induced the activation of focal adhesion kinase (FAK) and p38 mitogen-activated protein kinase (MAPK). Inhibition of FAK and p38 MAPK down-regulated type I collagen-induced MMP-13 expression. CONCLUSION: Our study indicates that metastatic breast cancer cells in the bone microenvironment attached to type I collagen, which stimulated integrins α1ß1 and α2ß1, via FAK and p38 MAPK pathways, to induce MMP13 expression and further osteolysis.

Parathyroid hormone-related peptide regulates matrix metalloproteinase-13 gene expression in bone metastatic breast cancer cells.

BACKGROUND: Breast cancer (BC) cells often metastasize to bone where they express large amounts of parathyroid hormone-related protein (PTHrP). In this study, we investigated the possibility that PTHrP may have roles in breast cancer bone metastasis independently of, or in addition to, its roles in osteoclastic function. MATERIALS AND METHODS: A mouse model of bone metastasis was prepared by inoculating mice with suspensions of the human BC cell line MDA-MB-231 tumor cells via the left cardiac ventricle. Matrix metalloproteinase-13 (MMP-13) expression in the bone microenvironment was examined by Western blot and Real-time RT-PCR (RT-PCR) analysis, as well as by confocal microscopy. RESULTS: The invading MDA-MB-231 cells contained conspicuous amounts of both PTHrP and MMP-13, an important matrix-degrading enzyme; and treatment of the cells in culture with exogenous PTHrP markedly stimulated MMP13 gene expression. Analysis of signaling mechanisms showed that PTHrP treatment led to rapid increases in the levels of phosphorylated protein kinase C (PKCα) and extracellular signal-regulated kinase (ERK1/2). Pharmacologic inhibition of ERK1/2 and PKC as well as of PKA activities counteracted the PTHrP-dependent stimulation of MMP13 expression. Indeed, pharmacologic activation of PKA or PKC was sufficient for stimulation of MMP13 expression. CONCLUSION: Consistent with these findings, the inhibition of PKC prevented PTHrP-induced activation of ERK1/2, whereas 12-O-tetradecanoylphorbol-13-acetate (TPA), a stimulator of PKC, up-regulated the PTHrP-induced activation of ERK1/2. Taken together, our data indicate that the MDA-MB-231 breast cancer cells may carry out bone destruction and favor their own metastatic behavior by producing MMP-13. Given that the cells expressed PTHrP and that this factor stimulated MMP-13 expression, metastatic bone destruction may result from a PTHrP autocrine loop involving a PKC-ERK1/2 signaling pathway.