Thymosin β4 has multi-functional roles in cell physiology, but little is known about its mechanism(s) of action. We previously reported that thymosin β4 stimulated angiogenesis through the induction of vascular endothelial growth factor (VEGF). To identify the mechanism of VEGF induction by thymosin β4, we have used a luciferase assay system with VEGF in the 5' promoter region. We also analyzed the effect of thymosin β4 on VEGF mRNA stability and on the expression and stability of hypoxia-inducible factor (HIF)-1α. We found that thymosin β4 induces VEGF expression by an increase in the stability of HIF-1α protein. Analysis of the expression patterns of thymosin β4 and HIF-1α in colon cancer tissue microarray showed that thymosin β4 and HIF-1α co-localized in these biopsies. These data show that thymosin β4 induces the expression of VEGF indirectly by increasing the protein stability of HIF-1α.

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Recent studies have shown that thymosin β4 (TB-4) is highly related with tumor metastasis and angiogenesis. In addition, TB-4 induced the expression of VEGF in melanoma cells. We investigated the expression patterns of TB-4 and related angiogenic proteins, VEGF, and HIF-1α, at various stages of cervical cancers and also identified the expression pattern of these proteins in metastatic cervical cancers. Expression patterns of TB-4, VEGF, and HIF-1α were studied with tissue microarray containing 42 samples of cervical cancers. In addition, 15 cervical cancers and metastatic tumors in lymph nodes from patients who have metastatic tumors were also analyzed to confirm the role of TB-4, VEGF, and HIF -1α in cervical cancer metastasis. The expression levels of TB-4, VEGF, and HIF-1α were very weak at early cancer stages (stages 0 to 1A) but significantly increased at stage 1B. The numbers of blood vessels in tumors were also increased at stage 1B. The expression patterns of TB-4, VEGF, and HIF-1α were compared in tumors without lymph node metastasis, primary tumors with lymph node metastasis, and metastatic tumors in lymph nodes. The expression levels of TB-4, VEGF, and HIF-1α in primary tumors with lymph node metastasis and their metastatic tumors in lymph node were less than in tumors without lymph node metastasis. These data suggest that TB-4, VEGF, and HIF-1α triggered angiogensis and tumor invasiveness to surrounding tissues at early stage of cervical carcinoma but have a negative or no effect on the metastatic potential.