Significance of maspin tumor suppressor genes in human tumors

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Cancer-associated DNA hypomethylation is as prevalent as cancer-linked hypermethylation, but the biological significance of DNA hypomethylation in carcinogenesis is less understood. The expression of maspin (mammary serpin) in cancerous and non-cancerous tissues. Paradoxical maspin expression due to epigenetic modification has been addressed in several cancer cell types. To elucidate the role of the maspin gene in thyroid cancer, we studied methylation status in the promoter region and its expression in human cancers. Their methylation status evaluated by the methylation-specific PCR method showed a good inverse correlation with their immunoreactivity in surgically resected specimens. Our data suggest that over-expression of Maspin by DNA hypomethylation is closely associated with morphological dedifferentiation in thyroid cancers. Immunoreactivity for maspin was observed in metaplastic (intestinal metaplasia) and cancerous tissues. There aberrant expression were caused by the disruption of the epigenetic status at the promoter region. Aberrant maspin expression appears to be closely associated with morphological changes such as metaplasia, dysplasia and dedifferentiation, probably as a result of disruption of epigenetic expression mechanisms.