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HIF-2α mediates hypoxia-induced LIF expression in human colorectal cancer cells.

Wu L, Yu H, Zhao Y, Zhang C, Wang J, Yue X, Yang Q, Hu W - Oncotarget (2015)

Bottom Line: LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients.Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells.Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens.

View Article: PubMed Central - PubMed

Affiliation: Rutgers Cancer Institute of New Jersey, Rutgers the State University of New Jersey, New Brunswick, NJ, USA.

ABSTRACT
Leukemia inhibitory factor (LIF), a multi-functional cytokine, has a complex role in cancer. While LIF induces the differentiation of several myeloid leukemia cells and inhibits their growth, it also promotes tumor progression, metastasis and chemoresistance in many solid tumors. LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients. Currently, the mechanism for LIF overexpression in tumor cells is not well-understood. Here, we report that hypoxia, a hallmark of solid tumors, induced LIF mRNA expression in human colorectal cancer cells. Analysis of LIF promoter revealed several hypoxia-responsive elements (HREs) that can specifically interact with and be transactivated by HIF-2α but not HIF-1α. Consistently, ectopic expression of HIF-2α but not HIF-1α transcriptionally induced LIF expression levels in cells. Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells. Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens. In summary, results from this study demonstrate that hypoxia induces LIF expression in human cancer cells mainly through HIF-2α, which could be an important underlying mechanism for LIF overexpression in human cancers.

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HIF-2α overexpression is associated with LIF overexpression in human colorectal cancer specimensHIF-2α and LIF protein levels were determined by IHC staining in tissue microarrays containing 284 cases of human colorectal cancer specimens. (A) Representative IHC staining results for HIF-2α (upper panels) and LIF (lower panels) are shown. Positive HIF-2α or LIF staining: > 10% cells stained with HIF-2α or LIF, respectively. Scale bar: 50 μm for low magnitude images (10X); 10 μm for high magnitude images (40X). (B) HIF-2α overexpression is associated with LIF overexpression in human colorectal tumors (p < 0.0001, Fisher exact test).
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Figure 5: HIF-2α overexpression is associated with LIF overexpression in human colorectal cancer specimensHIF-2α and LIF protein levels were determined by IHC staining in tissue microarrays containing 284 cases of human colorectal cancer specimens. (A) Representative IHC staining results for HIF-2α (upper panels) and LIF (lower panels) are shown. Positive HIF-2α or LIF staining: > 10% cells stained with HIF-2α or LIF, respectively. Scale bar: 50 μm for low magnitude images (10X); 10 μm for high magnitude images (40X). (B) HIF-2α overexpression is associated with LIF overexpression in human colorectal tumors (p < 0.0001, Fisher exact test).

Mentions: In a recent study, we reported that LIF is frequently overexpressed in human colorectal cancer samples [17]. In that study, we found that a significantly higher percentage of colorectal cancer samples showed positive LIF staining (> 10% cells are stained) compared with their matched adjacent normal tissues (72% vs. 20%, p < 0.005) as determined by IHC staining in formalin-fixed and paraffin-embedded (FFPE) colorectal cancer samples and their matched adjacent normal tissues [17]. To investigate whether hypoxia and HIF-2α contribute to the increased expression of LIF in human colorectal cancer samples, the expression levels of LIF and HIF-2α were determined in the tissue microarray comprising duplicate paraffin tissue cores of 284 human colorectal tumor samples by IHC staining. The representative IHC images of LIF and HIF-2α were shown in Figure 5A. Consistent with our previous finding [17], a significant portion of colorectal cancer samples (67%; 191 out of 284 cases) showed positive LIF staining. The overexpression of LIF was observed in all stages of colorectal cancer samples (82% in stage I, 18 of 22 cases; 64% in stage II, 148 of 232 cases; 86% in stage III, 19 of 22 cases; and 75% in stage IV, 6 of 8 cases). There is also a significant portion of colorectal cancer samples (64%; 183 out of 284 cases) showed positive HIF-2α staining (> 10% cells are stained). The percentage of colorectal cancer samples with positive HIF-2α staining is much higher in late stages (stages III & IV) than in early stages (stages I & II) (45% in stage I, 10 of 22 cases; 63% in stage II, 146 of 232 cases; 91% in stage III, 20 of 22 cases; and 88% in stage IV, 7 of 8 cases). Notably, HIF-2α overexpression is strongly associated with LIF overexpression (Figure 5B) (p < 0.0001, Fisher exact test). HIF-2α positive staining was observed in 77% of cases with LIF positive staining (148 of 191 cases), but only in 32% of cases with LIF negative staining (30 of 93 cases). These results strongly suggested that the transcriptional induction of LIF by hypoxia and HIF-2α is an important mechanism accounting for the LIF overexpression in human colorectal cancers.


HIF-2α mediates hypoxia-induced LIF expression in human colorectal cancer cells.

Wu L, Yu H, Zhao Y, Zhang C, Wang J, Yue X, Yang Q, Hu W - Oncotarget (2015)

HIF-2α overexpression is associated with LIF overexpression in human colorectal cancer specimensHIF-2α and LIF protein levels were determined by IHC staining in tissue microarrays containing 284 cases of human colorectal cancer specimens. (A) Representative IHC staining results for HIF-2α (upper panels) and LIF (lower panels) are shown. Positive HIF-2α or LIF staining: > 10% cells stained with HIF-2α or LIF, respectively. Scale bar: 50 μm for low magnitude images (10X); 10 μm for high magnitude images (40X). (B) HIF-2α overexpression is associated with LIF overexpression in human colorectal tumors (p < 0.0001, Fisher exact test).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4414199&req=5

Figure 5: HIF-2α overexpression is associated with LIF overexpression in human colorectal cancer specimensHIF-2α and LIF protein levels were determined by IHC staining in tissue microarrays containing 284 cases of human colorectal cancer specimens. (A) Representative IHC staining results for HIF-2α (upper panels) and LIF (lower panels) are shown. Positive HIF-2α or LIF staining: > 10% cells stained with HIF-2α or LIF, respectively. Scale bar: 50 μm for low magnitude images (10X); 10 μm for high magnitude images (40X). (B) HIF-2α overexpression is associated with LIF overexpression in human colorectal tumors (p < 0.0001, Fisher exact test).
Mentions: In a recent study, we reported that LIF is frequently overexpressed in human colorectal cancer samples [17]. In that study, we found that a significantly higher percentage of colorectal cancer samples showed positive LIF staining (> 10% cells are stained) compared with their matched adjacent normal tissues (72% vs. 20%, p < 0.005) as determined by IHC staining in formalin-fixed and paraffin-embedded (FFPE) colorectal cancer samples and their matched adjacent normal tissues [17]. To investigate whether hypoxia and HIF-2α contribute to the increased expression of LIF in human colorectal cancer samples, the expression levels of LIF and HIF-2α were determined in the tissue microarray comprising duplicate paraffin tissue cores of 284 human colorectal tumor samples by IHC staining. The representative IHC images of LIF and HIF-2α were shown in Figure 5A. Consistent with our previous finding [17], a significant portion of colorectal cancer samples (67%; 191 out of 284 cases) showed positive LIF staining. The overexpression of LIF was observed in all stages of colorectal cancer samples (82% in stage I, 18 of 22 cases; 64% in stage II, 148 of 232 cases; 86% in stage III, 19 of 22 cases; and 75% in stage IV, 6 of 8 cases). There is also a significant portion of colorectal cancer samples (64%; 183 out of 284 cases) showed positive HIF-2α staining (> 10% cells are stained). The percentage of colorectal cancer samples with positive HIF-2α staining is much higher in late stages (stages III & IV) than in early stages (stages I & II) (45% in stage I, 10 of 22 cases; 63% in stage II, 146 of 232 cases; 91% in stage III, 20 of 22 cases; and 88% in stage IV, 7 of 8 cases). Notably, HIF-2α overexpression is strongly associated with LIF overexpression (Figure 5B) (p < 0.0001, Fisher exact test). HIF-2α positive staining was observed in 77% of cases with LIF positive staining (148 of 191 cases), but only in 32% of cases with LIF negative staining (30 of 93 cases). These results strongly suggested that the transcriptional induction of LIF by hypoxia and HIF-2α is an important mechanism accounting for the LIF overexpression in human colorectal cancers.

Bottom Line: LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients.Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells.Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens.

View Article: PubMed Central - PubMed

Affiliation: Rutgers Cancer Institute of New Jersey, Rutgers the State University of New Jersey, New Brunswick, NJ, USA.

ABSTRACT
Leukemia inhibitory factor (LIF), a multi-functional cytokine, has a complex role in cancer. While LIF induces the differentiation of several myeloid leukemia cells and inhibits their growth, it also promotes tumor progression, metastasis and chemoresistance in many solid tumors. LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients. Currently, the mechanism for LIF overexpression in tumor cells is not well-understood. Here, we report that hypoxia, a hallmark of solid tumors, induced LIF mRNA expression in human colorectal cancer cells. Analysis of LIF promoter revealed several hypoxia-responsive elements (HREs) that can specifically interact with and be transactivated by HIF-2α but not HIF-1α. Consistently, ectopic expression of HIF-2α but not HIF-1α transcriptionally induced LIF expression levels in cells. Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells. Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens. In summary, results from this study demonstrate that hypoxia induces LIF expression in human cancer cells mainly through HIF-2α, which could be an important underlying mechanism for LIF overexpression in human cancers.

Show MeSH
Related in: MedlinePlus