Expression patterns of Thymosin β4 and cancer stem cell marker CD133 in ovarian cancers.

Thymosin β4 (Tβ4), a small acidic actin binding peptide, is overexpressed in a side population of cancer stem cells and CD133-positive colorectal cancer stem cells. In order to understand the relationship between Tβ4 and CD133, we studied the expression patterns of Tβ4 and CD133 in ovarian cancers. The expression patterns of Tβ4 and CD133 were studied in normal ovaries, primary ovarian cancers, metastatic ovarian cancers, primary stomach cancers, and normal stomachs by Western blot and immunohistochemistry. Expression patterns and co-localization of Tβ4 and CD133 were examined by immunofluorescence and confocal laser-scanning microscopy. Tβ4 is overexpressed in primary ovarian cancers, but not in primary stomach cancers, when compared with normal controls. However, Tβ4 levels in metastatic stomach cancers to the ovary are significantly upregulated compared with levels in normal stomachs and primary stomach cancers. These results suggest that Tβ4 levels are related to tumorigenesis in ovarian cancers and metastasis in stomach cancers. The expression of Tβ4 in normal ovaries and normal stomachs was weak, but was co-localized with CD133 expression. Tβ4 expression was also co-localized with CD133 expression in primary ovarian carcinomas, metastatic ovarian cancers from stomach cancers and primary stomach cancers. These data suggest that Tβ4 expression is strongly related to CD133 expression and is a characteristic of stem cells or cancer stem cells.