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Hypoxia-inducible factor-1 up-regulates the expression of Toll-like receptor 4 in pancreatic cancer cells under hypoxic conditions #MMPMID22487528
Fan P; Zhang JJ; Wang B; Wu HQ; Zhou SX; Wang CY; Zhang JH; Tian Y; Wu HS
Pancreatology 2012[Mar]; 12 (2): 170-8 PMID22487528show ga
BACKGROUND & AIMS: Hypoxia is a common characteristic of solid tumors. Recent studies confirmed that Toll-like receptor 4 (TLR4) plays a significant role in cancer invasion and progression. In this study, the correlation between the expression of TLR4 and the change of the protein level of Hypoxia-inducible factor-1 alpha (HIF-1alpha) was studied. METHODS: We examined 84 human pancreatic cancer tissues for expression of HIF-1alpha and TLR4 proteins. Panc-1 cells were exposed to normoxia (20% O(2)) or hypoxia (<1% O(2)) or treated with CoCl(2). TLR4 protein was analyzed by flow cytometry and immunostaining. Growth studies were conducted on cells with the HIF-1alpha inhibition isolated from stable transfected cell lines. Finally, TLR4 protein was detected by immunohistochemistry in vivo tumors. RESULTS: There was a positive correlation between TLR4 and HIF-1alpha protein in pancreatic cancer tissues. Hypoxic stress induced TLR4 mRNA and protein expression in Panc-1 cells. Cells transfected with HIF-1alpha siRNA showed attenuation of hypoxia stress-induced TLR4 expression. In vivo growth decreased in response to TLR4 and HIF-1alpha inhibiton. Transient HIF-1alpha siRNA treatment could effectively curb tumor growth in vivo. CONCLUSION: These results suggest that TLR4 expression in pancreatic cancer cells is up-regulated via HIF-1alpha in response to hypoxic stress and underscore the crucial role of HIF-1alpha-induced TLR4 in tumor growth.
Pancreatology 2012 ; 12 (2): 170-8
