Hypoxia-inducible Factor-1-mediated Regulation of Semaphorin 4D Affects Tumor Growth and Vascularity

Qiangming Sun,Hua Zhou,Nada O Binmadi,John R Basile

doi:10.1074/jbc.m109.057166

Abstract

Tumor progression and metastasis depend on the ability of cancer cells to initiate angiogenesis to ensure delivery of oxygen, nutrients, and growth factors to tumor cells and provide access to the systemic circulation. Hypoxia-inducible factor-1 (HIF-1) can activate expression of a broad range of genes that mediate many of the adaptive responses to decreased oxygen concentration, such as enhanced glucose uptake and formation of new blood vessels. Acting through Plexin-B1 on endothelial cells, Semaphorin 4D (Sema4D) has been shown to promote angiogenesis and enhance invasive growth and proliferation in some tumors. Here we show that the gene for Sema4D, the product of which is elevated in head and neck squamous cell carcinoma (HNSCC) cells, contains upstream hypoxia response elements (HRE) and is strongly induced in hypoxia in a HIF-1-dependent manner. Knocking down Sema4D expression with short hairpin (sh) RNA reduces in vitro endothelial cell migration and growth and vascularity of HNSCC xenografts expressing a degradation resistant HIF-1alpha subunit. We also demonstrate a correlation between HIF-1 activity and Sema4D expression in HNSCC specimens. These findings indicate that Sema4D is induced by hypoxia in a HIF-1-dependent manner and influences endothelial cell migration and tumor vascularity. Expression of Sema4D may be a strategy by which carcinomas promote angiogenesis and therefore could represent a therapeutic target for these malignancies.

Highlights

The semaphorins and plexins comprise a family of proteins shown to control proliferation and survival in many different cells and tissues, including the nervous system, the immune system (1), and the vasculature (2)
The head and neck squamous cell carcinoma (HNSCC) cell lines we studied here exhibited high levels of hypoxia-inducible factor-1 (HIF-1)␣ protein, even at baseline, and an enhanced activation of a hypoxia response in immunoblots and luciferase assays
Data suggest that like other pro-angiogenic factors, plexins and semaphorins are influenced by changes in oxygen tension (7)

Summary

To whom correspondence should be addressed

HIF-1 will bind to hypoxia response elements (HRE) in the promoter and activate expression of a broad range of genes that mediate the adaptive responses to decreased oxygen concentration, such as enhanced glucose uptake and the formation of new blood vessels via proliferation and migration of endothelial cells toward the developing tumor (10). This latter response is influenced by increased production of pro-angiogenic proteins such as vascular endothelial growth factor (VEGF). Expression of the HIF-1␣ oxygen-dependent degradation domain mutant (HIF-1␣ mODD) in cells resulted in elevated

The abbreviations used are

EXPERIMENTAL PROCEDURES

RESULTS

Findings

DISCUSSION