The present study deals with the molecular mechanisms involved in the regulation of E-cadherin expression under hypoxia, because the adjustment of the amount of E-cadherin due to physical stimuli of the microenvironment might influence the colonization of metastasis to skeleton. We analyzed the effect of 1% oxygen tension, that is similar to that encountered in the bone marrow by metastatic cells spreading from breast carcinoma. The purpose was to evaluate the hypoxiaorchestrated control of E-cadherin transactivation via hypoxia inducible factor-1 (HIF-1) and peroxisome proliferator activated receptor-gamma (PPAR gamma), and the involvement of Hippo pathway members, as regulators of transcription factors. To give a translational significance to the study, we took into consideration human pair-matched ductal breast carcinoma and bone metastasis: E-cadherin and Wwox were expressed in bone metastasis but not in breast carcinoma, while HIF-1 alpha and TAZ seemed localized principally in nuclei of metastasis and were found in all cell compartments of breast carcinoma. A close examination of the regulatory mechanisms underlying E-cadherin expression in bone metastasis was done in 1833 clone derived from MDA-MB231 cells. Hypoxia induced E-cadherin only in 1833 clone, but not in parental cells, through HIF-1 and PPAR gamma activities, while Wwox decreased. Since Wwox was highly expressed in bone metastasis, the effect of ectopic Wwox was evaluated, and we showed E-cadherin transactivation and enhanced invasiveness in WWOX transfected 1833 cells. Also, hypoxia was additive with ectopic Wwox remarkably enhancing HIF-1 alpha nuclear shuttle and accumulation due to the lengthening of the half-life of HIF-1 alpha protein; under this experimental condition HIF-1 alpha appeared as a slower migrated band compared with control, in agreement with the phosphoiylation state. The in vitro data strongly supported the almost exclusive presence of HIF-1 alpha in nuclei of human-bone metastasis. Thus, we identified Wwox as a novel molecule in the HIF-1 alpha-HDM2 regulatory loop, necessary for the dynamic regulation of the HIF-1 alpha amount, and we suggested that the reduction of endogenous Wwox free pool under hypoxia might also be due to the interaction with HDM2, sequestering the E3 ubiquitin ligase. We highlighted the importance of nuclear HIF1 alpha in the biology of metastasis for the mesenchymal-epithelial transition: this phenotype was regulated by Wwox plus hypoxia through E-cadherin target gene, playing a pivotal role in bone metastasis colonization. (C) 2014 Elsevier Inc. All rights reserved.
Hypoxia induced E-cadherin involving regulators of Hippo pathway due to HIF-1 alpha stabilization/nuclear translocation in bone metastasis from breast carcinoma
BANFI , GIUSEPPE;
2015-01-01
Abstract
The present study deals with the molecular mechanisms involved in the regulation of E-cadherin expression under hypoxia, because the adjustment of the amount of E-cadherin due to physical stimuli of the microenvironment might influence the colonization of metastasis to skeleton. We analyzed the effect of 1% oxygen tension, that is similar to that encountered in the bone marrow by metastatic cells spreading from breast carcinoma. The purpose was to evaluate the hypoxiaorchestrated control of E-cadherin transactivation via hypoxia inducible factor-1 (HIF-1) and peroxisome proliferator activated receptor-gamma (PPAR gamma), and the involvement of Hippo pathway members, as regulators of transcription factors. To give a translational significance to the study, we took into consideration human pair-matched ductal breast carcinoma and bone metastasis: E-cadherin and Wwox were expressed in bone metastasis but not in breast carcinoma, while HIF-1 alpha and TAZ seemed localized principally in nuclei of metastasis and were found in all cell compartments of breast carcinoma. A close examination of the regulatory mechanisms underlying E-cadherin expression in bone metastasis was done in 1833 clone derived from MDA-MB231 cells. Hypoxia induced E-cadherin only in 1833 clone, but not in parental cells, through HIF-1 and PPAR gamma activities, while Wwox decreased. Since Wwox was highly expressed in bone metastasis, the effect of ectopic Wwox was evaluated, and we showed E-cadherin transactivation and enhanced invasiveness in WWOX transfected 1833 cells. Also, hypoxia was additive with ectopic Wwox remarkably enhancing HIF-1 alpha nuclear shuttle and accumulation due to the lengthening of the half-life of HIF-1 alpha protein; under this experimental condition HIF-1 alpha appeared as a slower migrated band compared with control, in agreement with the phosphoiylation state. The in vitro data strongly supported the almost exclusive presence of HIF-1 alpha in nuclei of human-bone metastasis. Thus, we identified Wwox as a novel molecule in the HIF-1 alpha-HDM2 regulatory loop, necessary for the dynamic regulation of the HIF-1 alpha amount, and we suggested that the reduction of endogenous Wwox free pool under hypoxia might also be due to the interaction with HDM2, sequestering the E3 ubiquitin ligase. We highlighted the importance of nuclear HIF1 alpha in the biology of metastasis for the mesenchymal-epithelial transition: this phenotype was regulated by Wwox plus hypoxia through E-cadherin target gene, playing a pivotal role in bone metastasis colonization. (C) 2014 Elsevier Inc. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
