Hypoxia-inducible factor 1 and VEGF upregulate CXCR4 in glioblastoma: implications for angiogenesis and glioma cell invasion

Abstract

Hypoxia and hypoxia-inducible factor-1 (HIF-1) play a critical role in glioblastoma multiforme (GBMs). CXCR4 is involved in angiogenesis and is upregulated by HIF-1alpha. CXCR4 is a chemokine receptor for stromal cell-derived factor-1 (SDF-1)alpha, also known as CXCL12. We hypothesized that CXCR4 would be upregulated by hypoxia in GBMs. First, we investigated the expression of HIF-1alpha and CXCR4 in GBMs. CXCR4 was consistently found colocalized with HIF-1alpha expression in pseudopalisading glioma cells around areas of necrosis. In addition, angiogenic tumor vessels were strongly positive for CXCR4. Next, we tested the in vitro effect of hypoxia and vascular endothelial growth factor (VEGF) on the expression of CXCR4 in glioma cell lines and in human brain microvascular endothelial cells (HBMECs). Exposure to hypoxia induced significant expression of CXCR4 and HIF-1alpha in glioma cells, whereas treatment with exogenous VEGF increased CXCR4 expression in HBMECs. We also transfected U87MG glioma cells with an HIF-1alpha construct and observed that CXCR4 was upregulated in these cells even in normoxic conditions. We then used a lentivirus-mediated shRNA expression vector directed against HIF-1alpha. When exposed to hypoxia, infected cells failed to show HIF-1alpha and CXCR4 upregulation. We performed migration assays under normoxic and hypoxic conditions in the presence or absence of AMD3100, a CXCR4 inhibitor. There was a significant increase in the migration of U87MG and LN308 glioma cells in hypoxic conditions, which was inhibited in the presence of AMD3100. These studies demonstrate the critical role played by hypoxia and CXCR4 in glioma cell migration. Based on these studies, we suggest that hypoxia regulates CXCR4 in GBMs at two levels. First, through HIF-1alpha in the pseudopalisading tumor cells themselves and, secondly, by the VEGF-stimulated angiogenic response in HBMECs. We believe this knowledge may lead to a potentially important two-pronged therapy against GBM progression using chemotherapy targeting CXCR4.

HIF-1α determines the metastatic potential of gastric cancer cells

“…Furthermore, HIF-1a-competent cells showed a significantly better adherence to endothelial cells without reference to the oxygen concentration. Reduced migratory capacitiy of HIF-1a-deficient cells has been shown for a wide variety of primary and transformed cells, for example, neutrophils, macrophages, glioma and small cell lung cancer cells (Cramer et al, 2003;Liu et al, 2006;Zagzag et al, 2006). In the case of primary murine phagocytes, a highly reduced content of intracellular ATP has been shown to be the underlying molecular mechanism, most likely due to the pivotal role of HIF-1a for glycolysis (Seagroves et al, 2001;Cramer et al, 2003).…”

CXCR3 expression is associated with poor survival in breast cancer and promotes metastasis in a murine model

“…A CXCL12 gradient may promote the translocation of CXCR4-positive tumor cells to sites of ligand expression. The induction of CXCR4 expression by hypoxia may also facilitate escape of tumor cells from lowoxygen environments (13). Pharmacologic antagonism or gene silencing of CXCR4 reduces metastatic potential in several models (14,15).…”

Targeted inhibition of mTORC1 and mTORC2 by active-site mTOR inhibitors has cytotoxic effects in T-cell acute lymphoblastic leukemia

“…30 Cell response to hypoxia comprises upregulation of hypoxia-inducible factor-1a (HIF-1a), which is under control of mTORC1. 31 HIF-1a then induces transcription of a number of genes, including VEGF-A, 32 CXCR4, the receptor for CXCL12 chemokine 33 and PIM-1 kinase. 34 Interactions between CXCR4 and CXCL12 strongly contribute to drug resistance of leukemic cells.…”