Mild chronic hypoxia-induced HIF-2α interacts with c-MYC through competition with HIF-1α to induce hepatocellular carcinoma cell proliferation.
Cell Oncol (Dordr)
; 44(5): 1151-1166, 2021 Oct.
Article
em En
| MEDLINE
| ID: mdl-34339013
ABSTRACT
PURPOSE:
Hepatocellular carcinoma (HCC) has emerged as a leading cause of cancer-related deaths globally, in which hypoxia and activated hypoxia-inducible factors (HIFs) play important roles. The sibling rivalry between HIF-1α and HIF-2α in hypoxic tumor growth and progression still remains to be resolved, including in HCC. In this study, we aimed to analyze the mechanism by which HIF-1α and HIF-2α balance the proliferative response of HCC cells to hypoxia.METHODS:
The expression of HIF-1α, HIF-2α, c-MYC, Rictor and Raptor in corresponding tumor and non-tumor tissues from twenty-six patients with HCC was analyzed. The relationships between HIF-1α and HIF-2α and their respective effects were evaluated further in vitro in hypoxic HCC cells using co-immunoprecipitation, chromatin immunoprecipitation, in situ proximity ligation, annexin V-FITC/PI staining apoptosis and MTT assay. In addition, short hairpin RNA (shRNA) transfections targeting HIF-1α/2α and Rictor and Western blotting were applied in HCC cells to study the underlying mechanism.RESULTS:
We found that HIF-2α expression showed a positive correlation with c-MYC expression in tumor tissues, whereas HIF-1α did not. In vitro, increased HCC cell proliferation and an increased interaction between HIF-2α and c-MYC were observed under mild chronic hypoxic conditions. Although mild hypoxia led to HIF-1α, HIF-2α and c-MYC up-regulation, we found that mTORC2-regulated HIF-2α competed with HIF-1α to bind to c-MYC. Moreover, we found that HIF-2α knockdown decreased the expression of downstream c-MYC, suppressed hypoxic cell proliferation, and induced HCC cell apoptosis, whereas HIF-1α knockdown did not. Additionally, we found that the PI3K inhibitor apitolisib counteracted the effect of HIF-2α, thereby inducing HCC cell apoptosis.CONCLUSIONS:
Our data highlight a role of HIF-2α in activating and binding c-MYC, thereby inducing HCC cell proliferation during mild chronic hypoxia. The PI3K/mTORC2/HIF-2α/c-MYC axis may play a key role in this process. The PI3K inhibitor apitolisib may serve as a potential treatment option for patients suffering from HCC, especially in cases with rapidly growing tumors under mild chronic hypoxic conditions.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas Proto-Oncogênicas c-myc
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Carcinoma Hepatocelular
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Proliferação de Células
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Fatores de Transcrição Hélice-Alça-Hélice Básicos
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Subunidade alfa do Fator 1 Induzível por Hipóxia
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Neoplasias Hepáticas
Limite:
Aged
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Female
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Humans
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Male
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Middle aged
Idioma:
En
Revista:
Cell Oncol (Dordr)
Ano de publicação:
2021
Tipo de documento:
Article
País de afiliação:
China