The actin-sequestering
protein thymosin beta-4 (Tβ4) is involved in various cellular and physiological processes such as proliferation, motility, growth and
metastasis.
Nitric oxide (NO) promotes
tumor invasiveness and
metastasis by activating various
enzymes. Herein, we investigated whether
hypoxia-inducible NO regulates Tβ4 expression and
cancer cell migration using HeLa
cervical cancer cells. NO production and Tβ4 expression were increased in a hypoxic condition. The treatment with N-(β-D-Glucopyranosyl)-N2-acetyl-S-nitroso-D, L-penicillaminamide (SNAP-1), to generate NO, enhanced the transcription of Tβ4 and
cancer cell migration. SNAP-1-induced cell migration was decreased by the inhibition of Tβ4 with small interference (si)
RNA. In a hypoxic condition, treatment with N(G)-monomethyl-
L-arginine (
L-NMMA),
nitric oxide synthase (NOS) inhibitor, reduced Tβ4 transcriptional activity, and
hypoxia-inducible factor (HIF)-1α.
Hypoxia-induced
cancer cell migration was also decreased by
L-NMMA treatment. In a normoxic condition, Tβ4 transcriptional activity was decreased in the cells incubated in the presence of
L-NMMA after co-transfection with Tβ4 promoter and GST-conjugated HIF-1α. Collectively, these results suggest that NO could regulate the expression of Tβ4 by direct or indirect effect of HIF-1α on Tβ4 promoter.