HIF-1α Expression In Cancer Cells Research Articles

Hypoxia-induced ebv-circLMP2A promotes angiogenesis in EBV-associated gastric carcinoma through the KHSRP/VHL/HIF1α/VEGFA pathway.

EBV-encoded circular RNA LMP2A (ebv-circLMP2A) was found to be expressed in EBV-associated gastric carcinoma (EBVaGC) and associated with distant metastasis and poor prognosis. Angiogenesis is a key step in tumor invasion and metastasis and plays a crucial role in tumor progression. However, it is unclear whether and how ebv-circLMP2A is involved in angiogenesis. In this study, we showed that MVD, HIF1α, and VEGFA expression was increased in EBVaGC mouse xenografts with high expression of ebv-circLMP2A. The expression of ebv-circLMP2A was positively correlated with MVD, HIF1α, and VEGFA expression in clinical samples of EBVaGC. Knockdown of ebv-circLMP2A repressed tube formation and migration of HUVECs and decreased VEGFA and HIF1α expression in cancer cells under hypoxia, while ectopic expression of ebv-circLMP2A reversed these effects. Additionally, knockdown of HIF1α blocked the upregulation of ebv-circLMP2A by hypoxia, and ebv-circLMP2A interacted with KHSRP to enhance KHSRP-mediated decay of VHL mRNA, leading to the accumulation of HIF1α under hypoxia. There was a positive feedback loop between HIF1α and ebv-circLMP2A that promotes angiogenesis under hypoxia. ebv-circLMP2A was essential in regulating tumor angiogenesis in EBVaGC and might provide a valuable therapeutic target for EBVaGC.

Claudin-1/4 as directly target gene of HIF-1α can feedback regulating HIF-1α by PI3K-AKT-mTOR and impact the proliferation of esophageal squamous cell though Rho GTPase and p-JNK pathway.

Immunohistochemical microarray comprising 80 patients with esophageal squamous cell carcinoma (ESCC) and discovered that the expression of CLDN1 and CLDN4 were significantly higher in cancer tissues compared to para-cancerous tissues. Furthermore, CLDN4 significantly affected the overall survival of cancer patients. When two ESCC cell lines (TE1, KYSE410) were exposed to hypoxia (0.1% O2), CLDN1/4 was shown to influence the occurrence and development of esophageal cancer. Compared with the control culture group, the cancer cells cultured under hypoxic conditions exhibited obvious changes in CLDN1 and CLDN4 expression at both the mRNA and protein levels. Through genetic intervention and Chip, we found that HIF-1α could directly regulate the expression of CLDN1 and CLDN4 in cancer cells. Hypoxia can affect the proliferation and apoptosis of cancer cells by regulating the PI3K-Akt-mTOR pathway. Molecular analysis further revealed that CLDN1 and CLDN4 can participate in the regulation process and had a feedback regulatory effect on HIF-1α expression in cancer cells. In vitro cellular experiments and vivo experiments in nude mice further revealed that changes in CLDN4 expression in cancer cells could affect the proliferation of cancer cells via regulation of Rho GTP and p-JNK pathway. Whether CLDN4 can be target for the treatment of ESCC needs further research.

FTS and 2-DG induce pancreatic cancer cell death and tumor shrinkage in mice

The Ras inhibitor S-trans-trans farnesylthiosalicylic acid (FTS) inhibits active Ras, which controls cell proliferation, differentiation, survival, and metabolism. FTS also inhibits HIF1α expression in cancer cells, leading to an energy crisis. The synthetic glucose analog 2-deoxy-D-glucose (2-DG), which inhibits glycolysis, is selectively directed to tumor cells that exhibit increased glucose consumption. The 2-DG enters tumor cells, where it competes with glucose for glycolytic enzymes. In cancer models, as well as in human phase 1 trials, 2-DG inhibits tumor growth without toxicity. We postulated that under normoxic conditions, tumor cells treated with FTS would be more sensitive than normal cells to 2-DG. We show here that combined treatment with FTS and 2-DG inhibited cancer cell proliferation additively, yet induced apoptotic cell death synergistically both in vitro and in vivo. The induced apoptosis was inferred from QVD-OPH inhibition, an increase in cleaved caspase 3, and loss of survivin. FTS and 2-DG when combined, but not separately, also induced an increase in fibrosis of the tumor tissue, chronic inflammation, and tumor shrinkage. Overall, these results suggest a possible new treatment of pancreatic tumors by the combined administration of FTS and 2-DG, which together induce pancreatic tumor cell death and tumor shrinkage under non-toxic conditions.

Validated analysis of HIF-1α expression in cancer cells using a controlled and comparative immunoassay

The immunoreactivity of hypoxia inducible factor 1alpha (HIF-1alpha) has been considered a reliable indicator of the HIF-1 pathway activation in tissue hypoxia. However, HIF-1alpha immunoreactivity has been evaluated with different antibodies and heterogeneous protocols. The need to interpret contradictory findings requires, among other things, a comparison of the antibodies. This could be accomplished by using identical, well characterized antigenic targets and by decreasing the influence of other variables. We applied most of the commercially available antibodies, and an antibody developed in our laboratories, to the human cervical cancer HeLa cell line and tissue sections from a renal cell carcinoma systematically, and to other tumors selectively. The expression of HIF-1alpha in HeLa cells was induced by the hypoxia-mimetic DFO. Non-induced HeLa cells were used as 'genuine' negative controls in addition to routine ones. HeLa cells (both induced and not induced) were also examined by immunofluorescence and Western blotting. We found that the antibodies showed immunostaining patterns with remarkable qualitative and quantitative differences, an observation not emphasized in previous literature. Certain antibodies require careful application to avoid specificity issues, and others to avoid low sensitivity problems. Pairing certain antibodies can optimize evaluation of HIF-1alpha expression. Most previous immunohistochemical studies of HIF-1alpha have attempted to map hypoxic neoplastic tissues or to demonstrate hypoxia in studies of neoangiogenesis, rather than 'measuring' HIF-1alpha expression or activation, because this requires a validated immunoassay. Our study thus allows for the development of a controlled and comparative HIF-1alpha immunoassay, which could be valuable if HIF-1alpha becomes a therapeutic target.

Activated Vegfr2/kdr Pathway In Tumour Cells And Tumour Associated Vessels Of Colorectal Cancer

Vascular endothelial cell growth factor (VEGF) acts by phosphorylating specific tyrosine kinase receptors on endothelial cell membrane promoting angiogenesis. The study of the activation status of VEGF receptors in human malignancies has recently become feasible by means of specific monoclonal antibodies recognising the phosphorylated form of these receptors. In the current study, we investigate the expression of the phosphorylated VEGFR2/KDR receptor in normal colon and colorectal adenocarcinomas in parallel with histopathological parameters, prognosis and the expression of the 'hypoxia inducible factor' HIF1alpha. pVEGFR2/KDR was weakly expressed in the normal colon, but it was expressed strongly in the cytoplasm and nuclei of cancer cells and in the tumour associated vasculature, mainly at the invading tumour edge. pVEGFR2/KDR expression in cancer cells was significantly associated with a tumour diameter > 6 cm (P = 0.04), poor histological differentiation (P = 0.004) and with high CEF1alpha expression (P = 0.05). High pVEGFR2/KDR expressing vascular density was significantly related with a high VEGF and HIF1alpha expression in cancer cells (P = 0.02 and 0.03, respectively). This was also related significantly to high pVEGFR2/KDR expression in cancer cells. In multivariate analysis, the most significant predictors for death were lympho-vascular invasion (P < 0.001) followed by VEGF (P = 0.014), node status (P = 0.015), standard vascular density (P = 0.022) and necrosis (P = 0.032). pVEGFR2 receptors are largely expressed in colon cancer cells and intratumoural vasculature. As VEGF targeting agents enter the clinical practice, the role of monoclonal antibodies recognising the phosphorylated form of VEGF receptors as predictors of response to targeted therapies should be sought in clinicopathological trials.