Progression to malignancy in gliomas reflects inverse relation of PEDF and VEGF expression
A Chinese study has been the first to suggest that pigment epithelium derived factor (PEDF) expression is a marker for gliomas and might eventually be used to stop their growth.
PEDF mRNA in normal brain tissue was five times more abundant than in low grade malignant gliomas and over fifteen times more abundant than in high grade gliomas. It was significantly higher in low versus high grade gliomas. Cultured normal human glial cells were packed with PEDF protein whereas a glioma cell line (U251) was almost devoid of it. PEDF and vascular epithelial growth factor (VEGF) expression were inversely related in gliomas––PEDF expression progressively fell in transition from low to high stage malignancy as VEGF expression increased.
PEDF mRNA was measured by real time RT-PCR in surgical samples of normal brain tissue from patients with cerebral trauma (five) and 25 samples from patients with low grade (seven) and high grade (10) gliomas. PEDF and VEGF were immunostained with specific monoclonal antibodies in thin sections.
PEDF is a glycoprotein common to many tissues and found in almost all brain areas, which regulates growth and development in neural tissues. It has been implicated in inhibiting development of blood vessels and seems to protect neurones from tumour formation. So determining a relation between PEDF and VEGF—the most important stimulator of blood vessel development in solid tumours—was of special interest. Gliomas comprise 65% of primary malignant brain tumours, and their rapid growth and widespread vascularisation spells a poor prognosis.
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