Hypoxia upregulates ovarian cancer invasiveness via the binding of HIF‐1α to a hypoxia‐induced, methylation‐free hypoxia response element of S100A4 gene

Abstract

Hypoxia is known to play important roles in the development and progression of tumors. We previously demonstrated that S100A4, a critical molecule for metastasis, was upregulated in ovarian cancer cells. Therefore, we examined the mechanisms of the upregulation of S100A4 expression in ovarian carcinoma cells, with particular attention paid to the effects of hypoxia. The expression levels of S100A4 were found to be correlated with the invasiveness of ovarian carcinoma cells in vitro and in vivo, and the upregulation of S100A4 expression was associated with hypomethylation of CpG sites in the first intron of S100A4 in ovarian carcinoma cell lines and tissues. The expression of S100A4 was increased under hypoxia and was associated with elevated invasiveness, which was inhibited by S100A4 small interfering RNA (siRNA). In addition, exposure to hypoxia reduced the methylation of hypoxia-response elements (HRE) of the S100A4 gene in a time-dependent fashion, in association with the increased binding of HIF-1a to a methylation-free HRE in ovarian carcinoma cells. These results indicate that hypoxia-induced hypomethylation plays an essential role in S100A4 overexpression and the epigenetic transformation of ovarian carcinoma cells into the ''metastatic phenotype.''The metastatic potential of tumor cells has been reported to be regulated by their interactions with their microenvironment. These interactions can be modified by the accumulation of genetic and epigenetic changes, which are transient alterations induced by the local tumor microenvironment. In particular, the role of microenvironmental hypoxia has been focused on with regard to tumorigenesis, tumor progression and tumor biology. [1][2][3][4] Hypoxia is known to induce the expression of the transcription factor hypoxia-inducible factor (HIF), which has been reported to be upregulated in human malignancy. 5 HIF binds to hypoxia-response elements (HRE) 3 and activates the transcription of various target genes, not only angiogenetic factors but also metastasisassociated genes. 6 We previously reported that hypoxia was associated with invasive phenotypes in ovarian carcinomas. 7,8 In addition, HIF-1a overexpression is associated with a poor prognosis in patients with ovarian cancer, 9 suggesting that hypoxia is important for the acquisition of aggressive behavior in ovarian cancer cells. S100A4, which is also known as mts-l/metastasin/pEL98/ p9k, 10,11 belongs to the calcium binding S100 protein family. Altered expression levels of S100 proteins have been reported in several human diseases, such as cancer, inflammatory disorders and neurodegenerative conditions and are associated with cell motility and invasion. 11 Interestingly, a recent report suggested that cancer cells induce S100 expression to produce an appropriate metastatic site via an autocrine/paracrine pathway 12,13 and that S100A4 might be a cancer stem cell (CSC) marker. 14 We also reported that S100A4 expression was upregulated in ovarian cancer and that the expression of S100A4 was an independent pro...

Knockdown of S100A4 impairs arecoline-induced invasiveness of oral squamous cell carcinomas

“…Consistently, a mechanistic relationship between S100A4 and the hypoxia-inducible factor-1a (HIF-1a) in ovarian cancer cells has elucidated [28]. Hypoxia or hypoxia mimicking cobalt chloride (CoCl(2)) enhanced S100A4 expression in cancer cells [28,29]. These data support our findings that the activation of the HIF-1a signaling may be involved in arecoline-induced S100A4 expression and oncogenicity of OSCC.…”

“…In this study, CAY10585 (HIF1a inhibitor) was found to reduce S100A4 protein expression by arecoline in OE cells. Consistently, a mechanistic relationship between S100A4 and the hypoxia-inducible factor-1a (HIF-1a) in ovarian cancer cells has elucidated [28]. Hypoxia or hypoxia mimicking cobalt chloride (CoCl(2)) enhanced S100A4 expression in cancer cells [28,29].…”

Increased metabolites of 5-lipoxygenase from hypoxic ovarian cancer cells promote tumor-associated macrophage infiltration

“…The different responses to hypoxia between the two cell lines were also observed in some researches. 39,40 The phenomenon may be owing to some unknown differences in the two cell lines, such as the methylation of hypoxia-response elements of the gene. 39 The production of 5-HETE and LTB4 were higher under the hypoxia condition than normoxia.…”

“…39,40 The phenomenon may be owing to some unknown differences in the two cell lines, such as the methylation of hypoxia-response elements of the gene. 39 The production of 5-HETE and LTB4 were higher under the hypoxia condition than normoxia. Interestingly, the production of 5-HETE and LTB4 were also significantly increased under the normoxia condition.…”

HIF-2α as a prognostic marker for breast cancer progression and patient survival

“…HIF-1α has been associated with poor prognosis in a range of cancers including uterine, breast, and non-small cell lung cancer, as well as poor response to cancer therapies (Horiuchi et al, 2012;Kuo et al, 2012;Marton et al, 2012). Little is known, however, about the role of HIF-2α in solid tumors.…”