Thymosin β4 expression correlates with lymph node metastasis through hypoxia inducible factor-α induction in breast cancer.
Intratumoral hypoxia has been correlated with distant metastatic potential. Two hypoxia inducible factors (HIFs), HIF-1α and HIF-2α, are induced by hypoxia, and high expression of these proteins has been correlated to angiogenesis and distant metastasis. Thymosin β4 (Tβ4) is frequently highly expressed in cancer, and this overexpression correlates with malignant progression. The objective of this study was to investigate the clinical correlation of HIF-α with Tβ4 and the intracellular functional roles of Tβ4 on HIF-α activation. We examined HIF-1α, HIF-2α and Tβ4 expressions in clinical human breast carcinoma (n=70) by immunohistochemistry. We show that high expression of HIF-1α and HIF-2α strongly correlates with Tβ4 expression (P≤0.0001) and overexpression of Tβ4 correlates significantly with patients with lymph node metastasis (P<0.05) of human breast cancer. Additionally, we demonstrate that hypoxia up-regulates intracellular Tβ4 protein, which then affects HIF-α activity, which is the key in regulating VEGF expression. We confirmed that hypoxia-induced intracellular Tβ4 and HIF-α activities were reduced by interference of Tβ4 expression using Tβ4 shRNA lentivirus. Vascular epidermal growth factor (VEGF)-A, a well-recognized lymphangiogenic cytokine, was also down-regulated, but VEGF-C and VEGF-D expressions were not affected. These findings suggest that the overexpression of Tβ4 is strongly associated with HIF-1α and HIF-2α expression and is also clinicopathologically involved with lymph node metastatic potential of breast cancer through the modulation of HIF-αactivation and induction of VEGF-A. Ultimately, these results highlight Tβ4 as a potentially therapeutic target in malignant cancers.
Department of Life Science, Sookmyung Women's University, Yongsan-gu, Seoul, Republic of Korea.
Sun Young
SY
Yoon
Ha Reum
HR
Lee
Yoorim
Y
Park
Joo Heon
JH
Kim
Soo Young
SY
Kim
Suk Ran
SR
Yoon
Wang Jae
WJ
Lee
Byung Joo
BJ
Cho
Hyeyoung
H
Min
Jung-Wook
JW
Bang
Hyunjeong
H
Park
Sa Ik
SI
Bang
Daeho
D
Cho
D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis*; D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D015687:Cell Hypoxia / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis*; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013947:Thymosin / Q000096:biosynthesis*; D000099201:Thymosin beta(4); D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D014408:Biomarkers, Tumor; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D013947:Thymosin; D000099201:Thymosin beta(4); D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human