Tomotake Masuda

Nonylphenol induces the death of neural stem cells due to activation of the caspase cascade and regulation of the cell cycle

Endocrine disruptors (EDs) are a great concern throughout the world, because they have adverse effects on human health and wildlife. In the present study, we investigated the effects of EDs on the proliferation and survival of murine neural stem cells (NSCs). In contrast to bisphenol A, phthalic acid benzyl n‐butyl ester, phthalic acid di‐n‐butyl ester and phthalic acid di(2‐ethylhexyl) ester, the treatment of NSCs with 4‐nonylphenol for 24 h inhibited cell growth in a concentration‐dependent manner. In addition, treatment with 4‐nonylphenol resulted in nuclear condensation and DNA fragmentation (morphological changes due to apoptosis) in NSCs after 12 h of exposure, and activated caspase‐3 after 6 h and 9 h of exposure. Furthermore, an exposure to 4‐nonylphenol led to the accumulation of cells at the G2/M phase interface and down‐regulated the protein levels of cyclin A and B1, which are the major regulatory proteins at the G2 to M transition of the cell cycle. Together, these results indicate that, in contrast to other EDs, 4‐nonylphenol may exhibit a potent cytotoxicity through apoptosis via the caspase cascade and cell cycle arrest at the G2/M phase, and suggest that 4‐nonylphenol may affect neurogenesis in the CNS.

Critical Role of Peroxisome Proliferator-Activated Receptor γ on Anoikis and Invasion of Squamous Cell Carcinoma

Purpose: Peroxisome proliferator-activated receptor γ (PPARγ) plays a important role in various physiological functions. We examined whether PPARγ is expressed in primary squamous cell carcinoma and lymph node metastasis and whether PPARγ is a potential target for tumor therapy. Experimental Design and Results: A high-level expression of PPARγ was observed in tumor cells of human primary squamous cell carcinoma, lymph node metastasis, and squamous cell carcinoma cell lines. Treatment with PPARγ-specific antagonists, but not agonists, caused apoptotic cell death on squamous cell carcinoma cell lines in a concentration-dependent manner. Small interfering RNA for PPARγ also inhibited cell adhesion and growth of squamous cell carcinomas. The phosphorylation of focal adhesion kinase (FAK) was decreased by treatment with PPARγ antagonists, and resulted in decreases in phosphorylation of Erk and mitogen-activated protein kinase. Furthermore, PPARγ antagonists decreased the adhesion of squamous cell carcinomas into fibronectin-coated plates, indicating the inhibition of interaction between squamous cell carcinomas and fibronectin. Expression of integrin α5, a counter adhesion molecule for fibronectin, was inhibited by the treatment with PPARγ antagonists. These results indicate that the decrease in integrin α5 and following inhibition of cell adhesion may cause the inhibition of FAK signaling pathways. PPARγ antagonists also strongly inhibited invasion of squamous cell carcinoma via down-regulation of CD151 expression. Conclusions: The cell death caused by the PPARγ antagonists was a result of direct interference with cell adhesion “anoikis” involving intracellular FAK signaling pathways. These results imply a potentially important and novel role for the inhibition of PPARγ function via the use of specific antagonists in the treatment of squamous cell carcinoma and the prevention of tumor invasion and metastasis.

Critical role of estrogen receptor on anoikis and invasion of squamous cell carcinoma

Estrogen receptor (ER) plays an important role in various physiological functions. We examined whether ERα and ERβ are expressed in squamous cell carcinoma (SCC), and whether ER is a potential target for antitumor therapy. High‐level expression of ERβ, but not ERα, was observed in tumor cells of human primary SCC tissues and various SCC cultured cell lines. Treatment with ER antagonist (tamoxifen), but not agonist (estradiol), caused apoptotic cell death of SCC cells in a concentration‐ and time‐dependent manner. Adhesion of SCC was inhibited by the treatment with tamoxifen, but not with estradiol. Tamoxifen reduced the phosphorylation of focal adhesion kinase (FAK), resulting in decreases in phosphorylation of extracellular signal‐related kinase (Erk) and mitogen‐activated protein kinase. Inhibition of FAK phosphorylation is accompanied by disorder of the cytoskeletal component actin. The cell death caused by tamoxifen is therefore the result of direct interference in cell adhesion, which is called ‘anoikis’, involving a decrease in intracellular FAK signaling. Expression of epidermal growth factor receptor was also inhibited by treatment with a high concentration of tamoxifen. Knockdown of ERβ by small interfering RNA inhibited the proliferation of SCC. In addition, tamoxifen strongly inhibited invasion of SCC. These results imply a potentially important role for ER, whose inhibition may be effective for the treatment of SCC and the prevention of invasion and metastasis. (Cancer Sci 2007; 98: 636–643)

Intraductal papilloma arising from sublingual minor salivary gland: Case report and immunohistochemical study

Intraductal papilloma is a rare benign salivary gland tumor. This lesion is commonly observed in the duct of the minor salivary gland, predominantly in lip and buccal mucosa, but the case in the sublingual region is quite rare. This report shows a first case of intraductal papilloma developed in minor salivary gland of sublingual region. A 47-year-old Japanese male was referred to our hospital with painless submucosal nodule in the right sublingual region beside Whartons duct orifice. The excised specimen was histologically diagnosed as intraductal papilloma of minor salivary gland, according to the microscopic finding of the papillary growth of ductal epithelium into the ductal space with fibrovascular core. Immunohistochemical study showed the tumor cells originated from ductal luminal cells because of positive Cytokeratin 18 and 7 staining in both types of cells.