Bone is continuously remodeled by bone resorption and formation and, accordingly, bone metabolism is tightly regulated to maintain homeostasis. Deviation from the normal conditions of bone resorption can result in bone diseases. Lipid rafts are specialized plasma membrane microdomains that are enriched with glycosphingolipids, sphingomyelin and cholesterol. Lipid rafts are important for the transport of select membranes and relay stations involved in intracellular signaling.
To investigate the role of lipid rafts in RAW264 cells signaling, lipid rafts were disrupted by depleting cholesterol through the introduction of methyl-β-cyclodextrin (MβCD). We found that sRANKL-induced differentiation into osteoclasts was markedly inhibited by MβCD in a dose-dependent manner. MβCD enhanced the sRANKL-induced phosphorylation of ERK1/2 MAP kinase. In contrast, MβCD blocked the phosphorylation of IκB. These findings suggest that cholesterol might play a crucial role in the regulation of the sRANKL-mediated signaling pathway and in osteoclast differentiation of RAW264 cells, thereby reflecting its importance in the formation of plasma membrane lipid rafts.

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The aim of this study was to investigate the strain heterogeneity of Helicobacter pylori (H. pylori) in saliva, gastric juice, and urine by nested PCR and the direct sequence method, and to clarify the mode of transmission by examining whether H. pylori in the stomach and saliva are identical.
Thirty-nine patients undergoing endoscopy were enrolled in this study. H. pylori DNA was assayed in 104 samples using two sets of primers, EHC-U/EHC-L and ET-5U/ET-5L. DNA sequencing was performed in 24 samples.
H. pylori DNA was detected in 39 gastric juice samples (100%) and in 28 saliva samples (71.8%). The prevalence in urine samples was 50% (13/26). All samples except one were identical with over 97% identity to the DNA sequence of H. pylori type strain J99 (USA).
Nested PCR was highly sensitive for detection of H. pylori DNA in saliva, and DNA sequencing may be useful to clarify the mode of transmission.

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Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), which belongs to the EGF family, has been shown to stimulate the growth of a variety of cells in an autocrine or paracrine manner. Although HB-EGF is widely expressed in tumors when compared to normal tissue, its contribution to tumor invasion is still not known. In the present study, we analyzed the effects of HB-EGF on the invasion activity of a cultured oral cancer cell line using short interfering RNA (siRNA).
Oral squamous carcinoma cell lines, HSC3 and SAS, were transfected with siRNA targeting HB-EGF. Expression of HB-EGF was analyzed by real-time PCR. The invasiveness of the transfected cells was determined using a matrigel invasion assay, and MMP-9 production was measured by RT-PCR and gelatin zymography.
The expression of HB-EGF was reduced in HSC3-siRNA and SAS-siRNA cells. The matrigel invasion assay demonstrated that the invasiveness of HSC3-siRNA and SAS-siRNA cells was reduced. Gelatin zymography demonstrated that in HSC3-siRNA and SAS-siRNA cells, MMP9 production was decreased.
These findings suggest that HB-EGF expression is related to the invasion activity of oral cancer, particularly via regulation of MMP9.

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There have been very few studies on the expression of Centromere proteins in human salivary gland carcinomas. The purpose of this study was to clarify the correlation between Centromere protein H (CENP-H) expression and clinicopathologic factors in salivary gland carcinomas. The expression of CENP-H mRNA was investigated in 28 human salivary gland tumors (7 pleomorphic adenomas, 3 Warthin tumors, 6 mucoepidermoid carcinomas, 6 adenoid cystic carcinomas, 5 acinic cell carcinomas and 1 malignant myoepithelioma) and 8 normal submandibular glands using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). The labeling index of PCNA and Ki-67 were also investigated immunohistochemically in 16 salivary gland carcinomas. The mean expression level of CENP-H mRNA was significantly higher in malignant tumors (0.55 ± 0.68) than normal submandibular glands (0.10 ± 0.029). A significant correlation between the PCNA labeling index and CENP-H mRNA expression was also found (Spearman's correlation coefficient by rank test, P=0.033). We also found a significant correlation between the Ki-67 labeling index and CENP-H mRNA expression in malignant tumors (Spearman's correlation coefficient by rank test, P=0.040). These results indicate that human CENP-H mRNA is closely linked to increased or abnormal cell proliferation in malignant salivary gland tumors.

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Apoptosis is one mechanism by which cancer cells can be eliminated. Therefore, understanding the signaling pathways that transduce apoptotic signals in cancer cells is an indispensable component of cancer research. Rac, a member of the Rho family of proteins, has been implicated in the regulation of cell survival and apoptosis. However, the mechanisms underlying this process remain to be elucidated. To understand the role of Rac in oral squamous cancer, we inhibited its activity by a Rac-specific small molecule inhibitor, NSC23766, or transfection of dominant negative Rac (Rac-DN), and discovered that inhibition of Rac activity elicits apoptosis in highly malignant oral squamous carcinoma (OSC-19) cells. Upon suppression of Rac, we observed up-regulation of c-Jun N-terminal kinase (JNK), leading to caspase-dependent apoptosis. Furthermore, stimulation of protein phosphatase (PP5) rescued apoptosis caused by Rac inhibition by dephosphorylating JNK. Taken together, inhibition of Rac activity leads to the suppression of PP5 activity, which results in extensive activation of JNK and caspase-dependent apoptosis. In conclusion, Rac inhibition may represent a novel therapeutic approach for oral squamous carcinoma.

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