Hypoxia-inducible factor 1alpha mediates anoikis resistance via suppression of alpha5 integrin.
The transcription factor hypoxia-inducible factor 1 (HIF-1) alpha is abundantly expressed in the majority of human carcinomas and their metastases. HIF-1alpha controls central metastasis-associated pathways such as glycolysis, angiogenesis, and invasion. Functional inhibition of HIF-1alpha leads to impaired metastasis formation in murine tumor models. However, the precise molecular mechanisms underlying the metastasis-promoting role of HIF-1alpha have not been fully characterized. The ability of transformed epithelial cells to initiate the metastatic cascade relies on their ability to escape anoikis, a default program of apoptosis induction following loss of integrin anchoring to the extracellular matrix. Therefore, we addressed the function of HIF-1alpha in anoikis resistance and anchorage-independent growth. Inhibition of HIF-1alpha via RNA interference resulted in up-regulation of alpha5 integrin on the cell surface of human gastric cancer cells, whereas other integrins remained unaffected. Integrin alpha5 induction occurred at the level of transcription and was dependent on elevated intracellular superoxide in HIF-1alpha-knockdown cells. HIF-1alpha-deficient cells displayed significantly increased anoikis susceptibility due to up-regulated alpha5 integrin. Finally, colony formation in soft agar was shown to be dependent on HIF-1alpha as HIF-1alpha-deficient cells displayed a 70% reduction in anchorage-independent proliferation. Results obtained by RNA interference could be entirely confirmed by application of the pharmacologic HIF-1alpha-inhibitor 2-methoxyestradiol. Hence, our data argue for a pivotal role for HIF-1alpha in anoikis control via suppression of alpha5 integrin. HIF-1alpha-inhibiting drugs might therefore offer an innovative strategy for antimetastatic cancer therapy.
Rohwer
Nadine
N
Medizinische Klinik mit Schwerpunkt Hepatologie und Gastroenterologie, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum and Freie Universität Berlin, Fachbereich Biologie, Pharmazie, Berlin, Germany.
Welzel
Martina
M
Daskalow
Katjana
K
Pfander
David
D
Wiedenmann
Bertram
B
Detjen
Katharina
K
Cramer
Thorsten
T
D000077584:2-Methoxyestradiol; D023102:Anoikis / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D039482:Integrin alpha5 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D014162:Transfection
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D039482:Integrin alpha5; D034741:RNA, Small Interfering; D004958:Estradiol; D000077584:2-Methoxyestradiol