Overexpression of bHLH domain of HIF-1 failed to inhibit the HIF-1 transcriptional activity in hypoxia

BACKGROUND: Hypoxia inducible factor-1 (HIF-1) is considered as the most activated transcriptional factor in response to low oxygen level or hypoxia. HIF-1 binds the hypoxia response element (HRE) sequence in the promoter of different genes, mainly through the bHLH domain and activates the transcription of genes, especially those involved in angiogenesis and EMT. Considering the critical role of bHLH in binding HIF-1 to the HRE sequence, we hypothesized that bHLH could be a promising candidate to be targeted in hypoxia condition. METHODS: We inserted an inhibitory bHLH (ibHLH) domain in a pIRES2-EGFP vector and transfected HEK293T cells with either the control vector or the designed construct. The ibHLH domain consisted of bHLH domains of both HIF-1a and Arnt, capable of competing with HIF-1 in binding to HRE sequences. The transfected cells were then treated with 200 µM of cobalt chloride (CoCl2) for 48 h to induce hypoxia. Real-time PCR and western blot were performed to evaluate the effect of ibHLH on the genes and proteins involved in angiogenesis and EMT. RESULTS: Hypoxia was successfully induced in the HEK293T cell line as the gene expression of VEGF, vimentin, and ß-catenin were significantly increased after treatment of untransfected HEK293T cells with 200 µM CoCl2. The gene expression of VEGF, vimentin, and ß-catenin and protein level of ß-catenin were significantly decreased in the cells transfected with either control or ibHLH vectors in hypoxia. However, ibHLH failed to be effective on these genes and the protein level of ß-catenin, when compared to the control vector. We also observed that overexpression of ibHLH had more inhibitory effect on gene and protein expression of N-cadherin compared to the control vector. However, it was not statistically significant. CONCLUSION: bHLH has been reported to be an important domain involved in the DNA binding activity of HIF. However, we found that targeting this domain is not sufficient to inhibit the endogenous HIF-1 transcriptional activity. Further studies about the function of critical domains of HIF-1 are necessary for developing a specific HIF-1 inhibitor.

Expression of aldehyde dehydrogenase after neoadjuvant chemotherapy is associated with expression of hypoxia-inducible factors 1 and 2 alpha and predicts prognosis in locally advanced breast cancer

OBJECTIVE: To analyze the expression of hypoxia-inducible factors (hypoxia-inducible factor 1A and hypoxia-inducible factor 2A) and aldehyde dehydrogenase proteins in patients with locally advanced breast carcinoma who were subjected to neoadjuvant chemotherapy. METHODS: We included 90 patients with histologically confirmed stage II and III breast carcinoma who were treated with neoadjuvant chemotherapy between 2000 and 2005. Immunohistochemistry for aldehyde dehydrogenase, hypoxia-inducible factor 1A, and hypoxia-inducible factor 2A was performed before and after neoadjuvant chemotherapy. We analyzed the influence of clinical and pathological features on clinical and pathological response, disease-free survival, and overall survival. RESULTS: An objective clinical response to neoadjuvant chemotherapy was observed in 80% of patients, with 12% showing a complete pathological response. Among all clinical and pathological parameters, only the expression of hypoxia-inducible factor 1A was associated with a pathological response. A positive association was found between expression of aldehyde dehydrogenase and that of hypoxia-inducible factor 1A before and after chemotherapy. Aldehyde dehydrogenase expression was associated with expression of hypoxia inducible-factor 2A in tumors after neoadjuvant treatment. In a univariate analysis, prognosis was influenced by age, pathological response, metastasis to axillary lymph nodes after neoadjuvant chemotherapy, overexpression of hypoxia-inducible factor 2, and the presence of aldehyde dehydrogenase-positive cells within the primary tumor after neoadjuvant chemotherapy. In a multivariate analysis, only age and the presence of aldehyde dehydrogenase-positive cells after chemotherapy were associated with reduced overall survival. CONCLUSION: The presence of aldehyde dehydrogenase-positive cells within the residual tumor after neoadjuvant chemotherapy is associated with an increase in the expression ...

Expression of Hypoxia-inducible factor 1-α and Vascular endothelial growth factor-C in locally advanced breast cancer patients

BACKGROUND: Locally advanced breast cancers are more prevalent in underdeveloped countries. Targeted therapy has been improved to identify hallmarks that are specific to these subtypes of tumors. OBJECTIVES: We aimed to prospectively assess the expression of Hypoxia inducible factor-1 α and vascular endothelial growth factor-C in locally advanced breast cancer patients. METHODS: Thirty women underwent incisional biopsies for the histopathological diagnosis of breast carcinoma and participated in neoadjuvant chemotherapy. The association of Hypoxia inducible factor-1 α and vascular endothelial growth factor-C with age, tumor size, histological grade, clinical staging, hormonal and axillary status, clinical and pathological response after neoadjuvant chemotherapy, expression of estrogen and progesterone receptors, and the presence of c-erbB-2 antigen was studied. RESULTS: Hypoxia inducible factor-1 α expression and Vascular endothelial growth factor-C expression were observed in 66.7 percent and 63.3 percent of all patients, respectively, and were marginally associated with each other (p = 0.06). Among the studied variables, only positive axillary status was associated with the presence of HIF-1α (p = 0.02). Complete pathological response was significantly associated (p = 0.04) with the expression of vascular endothelial growth factor-C prior to neoadjuvant chemotherapy. CONCLUSION: We concluded that Hypoxia inducible factor-1 α was associated with a poor prognosis and that vascular endothelial growth factor-C could be used as a predictive factor in locally advanced breast cancer patients with complete pathological response after neoadjuvant chemotherapy.

Hierro, oxígeno y desarrollo placentario en la génesis de la preeclampsia: Efectos de la altura en Ecuador / Iron, oxygen and placental development in the etiology of preeclampsia: Effects of high altitude in Ecuador

Preeclampsia is the second cause of maternal death in Ecuador. The etiology of this condition is probably a placental alteration, although the details are not well known. The development of the placenta is closely related to the availability of oxygen. A defect in the differentiation of trophoblastic cells due to a faulty sensitization to changes in oxygen pressure, could be the cause of the alteration in placental development. The role of iron and local environmental conditions of a susceptible population, should be considered in the study of the etiology of preeclampsia. In the Andrean area of Ecuador, the high incidence of preeclampsia could be explained by the high prevalence of anemia and high altitude. However more studies are required to establish a close link between the environmental conditions of this area and the imperfect placental development.

Modulation of Colon Cancer Cell Invasiveness Induced by Deoxycholic Acid / 대한소화기학회지

BACKGROUND/AIMS: Deoxycholic acid (DCA), a secondary bile acid, has been implicated to promote colon cancer growth and progression. However, its molecular mechanisms are largely unknown. In this study, we investigated the effects of DCA on proliferation, migration, and invasiveness of colon cancer cells (HT-29). METHODS: HT-29 cells were incubated with either medium (control) only or DCA for 24-48 hours. Time courses of RT-PCR for vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF)-1alpha mRNA expression, Western blotting for VEGF and matrix metalloproteinase (MMP)-9, zymography for MMP-9 activation, and wound-migration assay were determined after various concentrations of DCA (0-80mum) treatment. Moreover, these experiments were reassessed after pretreatments (2-6 hours) with specific inhibitors of various signal pathways. RESULTS: DCA enhanced HIF-1alpha mRNA expression, VEGF mRNA and VEGF protein expression, MMP-9 protein expression/activation, and cell migration ability in a dose-related manner. DCA-induced VEGF protein expression was inhibited by pretreatment with NS-398 (COX-2 inhibitor), PDTC (NF-kappaB inhibitor), or tauroursodeoxycholic acid (TUDC). DCA-induced cell migration ability was inhibited by pretreatment of GF109203X, a protein kinase C inhibitor. DCA-induced MMP-9 protein expression/activation was inhibited by pretreatment with SB203580, U0126, or PDTC. CONCLUSIONS: DCA significantly upregulates invasive and angiogenic potentials of human colon cancer cells through multiple signal transduction pathways.