The hamster ornithine decarboxylase antizyme (ODCAz) cDNA was transfected into the hamster malignant oral keratinocyte cell line, HCPC-1. Ectopic expression of ODC-Az resulted in the reversion of malignant phenotypes and alteration of DNA methylation status of CCGG sites. The phenotypes examined include ODC enzymatic activity, doubling time, morphological change, anchorage dependent growth, tumorigenicity in nude mice, induction of epithelial dierentiation marker protein (involucrin), and change of cell cycle position. Comparison of CCGG DNA methylation status of the ODC-Az and control vector transfectants revealed a signi®cant increase in demethylation of 5-methyl cytosines (m 5 C) of CCGG sites in the ODC-Az transfectants. Ectopic expression of ODC-Az gene in hamster malignant oral keratinocytes led to reduce ODC activity and the subsequent demethylation of 5-methyl cytosines, presumably via the ODC/ polyamines/ decarboxylated S-adenosylmethionine (dc-AdoMet) pathways. Our data suggest that ODC-Az shared the same pathway of polyamines/ dc-AdoMet/DNA methyltransferase (DNA MTase). We propose that ODC-Az mediates a novel mechanism in tumor suppression by DNA demethylation and presumably re-activation of key cellular genes silenced by DNA hypermethylation during cancer development. Oncogene (2001) 20, 24 ± 33.

Although RAD21 is involved in the repair of double-strand breaks in DNA and is essential for mitotic growth, its role in cancer has been unclear. In this study, the relevance of RAD21 gene expression to the invasion and metastasis of oral squamous cell carcinoma was clarified using laser microdissection and real-time polymerase chain reaction (PCR). Using two different metastatic potential oral squamous cells [high-metastatic-potential squamous cell carcinoma cells (SAS-Ly) and low-metastatic-potential squamous cell carcinoma cells (SAS)], the relation of RAD21 gene expression to apoptosis, invasion, and metastasis was examined. The results showed that RAD21 gene expression was significantly decreased in oral squamous cell carcinoma when it expressed the INFbeta and INFgamma invasion patterns in comparison with the INFalpha invasion pattern (p<0.01). In addition, in comparison with SAS cells, SAS-Ly cells indicated tolerance to cell death induced by an apoptosis induction reagent, while the expression level of the RAD21 gene in SAS cells was increased by the apoptosis induction reagent. However, in SAS-Ly cells, the reagent induced no significant difference. Our findings indicate that the RAD21 gene was closely related to the invasion and metastasis of cancer cells.

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Protein kinase C (PKC) is an important molecule involved in various cell function, and mediates induced secretion of vascular endothelial growth factor (VEGF). It is hypothesized that PKC and VEGF may be associated with tooth development. Using the laser microdissection method and real-time reverse-transcription-polymerase chain-reaction (RT-PCR), we investigated the expression of PKC betaI and betaII, VEGF, and amelogenin (used as a marker of differentiation to ameloblasts) in the inner and outer enamel epithelia, stellate reticulum, and dental papilla in each stage of the dental germ. We found that the expression levels of PKC betaI and betaII were increased in the inner enamel epithelium during the early bell stage. In addition, the increased expression levels of PKC betaI and betaII were accompanied by increased VEGF expression. These results indicate that PKC betaI, betaII, and VEGF are closely associated with the differentiation of the inner enamel epithelium to ameloblasts.

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Some of the genes we identified with differential expression are related to the immune system. These results are telling us the new information for understanding the secretory human endometrium.