ERG is a novel and reliable marker for endothelial cells in central nervous system tumors

Abstract

ETS-related gene (ERG) is a transcription factor that has been linked to angiogenesis. Very little research has been done to assess ERG expression in central nervous system (CNS) tumors. We evaluated 57 CNS tumors, including glioblastomas (GBMs) and hemangioblastomas (HBs), as well as two arteriovenous malformations and four samples of normal brain tissue with immunohistochemistry using a specific ERG rabbit monoclonal antibody. In addition, immunostains for CD31, CD34, and α-smooth muscle actin (α-SMA) were performed on all samples. CD31 demonstrated variable and sometimes weak immunoreactivity for endothelial cells. Furthermore, in 1 case of a GBM, CD34 stained not only endothelial cells, but also tumor cells. In contrast, we observed that ERG was only expressed in the nuclei of endothelial cells, for example, in the hyperplastic vascular complexes that comprise the glomeruloid microvascular proliferation seen in GBMs. Conversely, α-SMA immunoreactivity was identified in the abluminal cells of these hyperplastic vessels. Quantitative evaluation with automated methodology and custom Matlab 2008b software was used to calculate percent staining of ERG in each case. We observed significantly higher quantitative expression of ERG in HBs than in other CNS tumors. Our results show that ERG is a novel, reliable, and specific marker for endothelial cells within CNS tumors that can be used to better study the process of neovascularization.

Figure 1.. Matlab quantitative determination of EVI. a: Original image of a GBM stained with ERG (100× magnification). b: Demonstration of calculation of degree of ERG staining (EVI = 5.028).

Figure 2.. GBM. a: H & E demonstrates pseudopalisading cells surrounding areas of central necrosis, with associated areas of microvascular proliferation. b: ERG exclusively highlights the nuclei of endothelial cells. c: CD34 highlights endothelial cells. d: CD31 weakly highlights endothelial cells. e: α-SMA highlights smooth muscle cells within the walls of vascular channels. The magnification for a: 100×. The magnification for b – e: 50×.

Figure 3.. GBM, glomeruloid type. a: H & E demonstrates glomeruloid microvascular proliferation. b: ERG exclusively highlights the nuclei of endothelial cells. c: CD34 highlights endothelial cells. d: CD31 weakly highlights endothelial cells. e: α-SMA highlights smooth muscle cells within the walls of vascular channels. The magnification for a: 100×. The magnification for b – e: 50×.

Figure 4.. GBM, epithelioid type. a: H & E demonstrates a vascular lumen. b: ERG exclusively highlights the nuclei of endothelial cells. c: CD34 highlights not only endothelial cells, but also tumor cells. d: α-SMA highlights smooth muscle cells within the wall of a vascular channel (a – d: 200× magnification).

Figure 5.. HB. a: H & E demonstrates markedly diffuse microvascular proliferation. b: ERG exclusively highlights the nuclei of endothelial cells. c: CD34 highlights endothelial cells. d: CD31 weakly highlights endothelial cells. e: α-SMA highlights abluminal smooth muscle cells within hyperplastic vascular complexes. The magnification for a: 100×. The magnification for b – e: 50×.

Figure 6.. Metastatic carcinoma. a: H & E demonstrates a vascular lumen. b: ERG exclusively highlights the nuclei of endothelial cells. c: CD34 highlights endothelial cells (a – c 200× magnification).

Figure 7.. EVI of different CNS lesions, plotted with SD.