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HIF2?/EFEMP1 cascade mediates hypoxic effects on breast cancer stem cell hierarchy.

ABSTRACT: Breast cancer stem cells (BCSCs) have been shown to contribute to tumor growth, metastasis, and recurrence. They are also markedly resistant to conventional cancer treatments, such as chemotherapy and radiation. Recent studies have suggested that hypoxia is one of the prominent micro-environmental factors that increase the self-renewal ability of BCSCs, partially by enhancing CSC phenotypes. Thus, the identification and development of new therapeutic approaches based on targeting the hypoxia-dependent responses in BCSCs is urgent. Through various in vitro studies, we found that hypoxia specifically up-regulates BCSC sphere formation and a subset of CD44+/CD24-/low CSCs. Hypoxia inducible factors 2? (HIF2?) depletion suppressed CSC-like phenotypes and CSC-mediated drug resistance in breast cancer. Furthermore, the stimulatory effects of hypoxia-induced HIF2? on BCSC sphere formation were successfully attenuated by epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) knockdown. Taken together, these data suggest that HIF2? mediates hypoxia-induced cancer growth/metastasis and that EFEMP1 is a downstream effector of hypoxia-induced HIF2? during breast tumorigenesis.

SUBMITTER: Kwak JH

PROVIDER: S-EPMC5190041 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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HIF2α/EFEMP1 cascade mediates hypoxic effects on breast cancer stem cell hierarchy.

Kwak Ji-Hye JH Lee Na-Hee NH Lee Hwa-Yong HY Hong In-Sun IS Nam Jeong-Seok JS

Oncotarget 20160701 28

Breast cancer stem cells (BCSCs) have been shown to contribute to tumor growth, metastasis, and recurrence. They are also markedly resistant to conventional cancer treatments, such as chemotherapy and radiation. Recent studies have suggested that hypoxia is one of the prominent micro-environmental factors that increase the self-renewal ability of BCSCs, partially by enhancing CSC phenotypes. Thus, the identification and development of new therapeutic approaches based on targeting the hypoxia-dep ...[more]

PMID: 27270657

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Project description:BACKGROUND:Tumor hypoxia is an independent prognostic factor associated with poor patient survival. Emerging evidence suggests that hypoxia can potentially maintain or enhance the stem cell phenotype of both normal stem cells and cancer cells. However, it remains to be determined whether cell fate is regulated in vivo by the hypoxic tumor microenvironment (TME). METHODS:We established a hypoxia-sensing xenograft model to identify hypoxic tumor cell in vivo primarily using human breast cancer cell lines MDA-MB-231 and MCF7. Hypoxic tumor cells were identified in situ by fluorescence of green fluorescence protein. They were further isolated from xenografts, purified and sorted by flow cytometry for detailed analysis of their stem cell characteristics. RESULTS:We have found that hypoxic tumor cells freshly isolated from xenografts contain increased subpopulations of tumor cells with cancer stem cell (CSC)-like characteristics. The CSC characteristics of the hypoxic tumor cells are further enhanced upon re-implantation in vivo, whereas secondary xenografts derived from the non-hypoxic tumor cells remain similar to the primary xenografts. Interestingly, the phenotypes exhibited by the hypoxic tumor cells are stable and remain distinctively different from those of the non-hypoxic tumor cells isolated from the same tumor mass even when they are maintained under the same ambient culture conditions. Mechanistically, the PI3K/AKT pathway is strongly potentiated in the hypoxic tumor cells and is required to maintain the CSC-like phenotype. Importantly, the differential cell fates between hypoxic and non-hypoxic tumor cells are only found in tumor cells isolated from the hypoxic TME in vivo and are not seen in tumor cells treated by hypoxia in vitro alone. CONCLUSIONS:These previously unknown observations suggest that the hypoxic TME may promote malignant progression and therapy resistance by coordinating induction, selection and/or preferential maintenance of the CSC-like phenotype in tumor cells.

Dataset Information

HIF2?/EFEMP1 cascade mediates hypoxic effects on breast cancer stem cell hierarchy.

Publications

HIF2α/EFEMP1 cascade mediates hypoxic effects on breast cancer stem cell hierarchy.

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