Archives of Biological Sciences 2017 Volume 69, Issue 4, Pages: 593-601
https://doi.org/10.2298/ABS161124003Y
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The role of hypoxia response element in TGFβ-induced carbonic anhydrase IX expression in Hep3B human hepatoma cells
Yildirim Hatice (University of Balikesir, Faculty of Science and Literature, Department of Molecular Biology and Genetics, Balikesir, Turkey)
Karaman Merve (University of Balikesir, Faculty of Science and Literature, Department of Molecular Biology and Genetics, Balikesir, Turkey)
Köçkar Feray (University of Balikesir, Faculty of Science and Literature, Department of Molecular Biology and Genetics, Balikesir, Turkey)
Carbonic anhydrase IX (CAIX) is a hypoxia-regulated gene. It is over expressed
in a variety of cancers, including hepatocellular cancer. Transforming growth
factor β (TGFβ) is considered to have an impact on cancer biology due to its
important roles in cell proliferation and differentiation. The effect of the
TGFβ on CAIX expression under hypoxia and the mechanism underlying the role
of the hypoxia response element (HRE) on this expression are unknown. In this
study, we demonstrate that TGFβ upregulates CAIX expression under hypoxic
conditions in the Hep3B hepatoma cell line, indicating that the
mitogen-activated protein kinase (MAPK)- and
phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)-signaling pathways
might be responsible for this response. Site-directed mutagenesis of the HRE
region in CAIX promoter reduced the TGFβ-induced CAIX promoter activity,
pointing to the significance of HRE for this response. Up regulation of
TGFβ-stimulated CAIX expression was consistent with the up regulation of
promoter activity of five different truncated constructs of the CAIX promoter
under hypoxia. Our findings show that the HRE region is critical for
TGFβ-induced CAIX expression, which is mainly controlled by MAPK and PI3K
pathways.
Keywords: carbonic anhydrase IX (CAIX), hypoxia response element (HRE), transforming growth factor β (TGFβ), mitogen-activated protein kinase (MAPK) signaling, phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) signaling