Increased aquaporin 1 water channel expression in human brain tumours

Abstract

Aquaporin 1 is a water channel protein. There was little aquaporin 1 immunoreactivity in normal brain parenchyma. In astrocytomas, aquaporin 1 was expressed in microvessel endothelia and neoplastic astrocytes. In metastatic carcinomas, aquaporin 1 was present in microvessel endothelia and reactive astrocytes. Aquaporin 1 may participate in the formation of brain tumour oedema.

Figure 1

Immunostaining (brown) for (A–G) AQP1 and (H) GFAP with cresyl violet counterstain. (A) and (B) Microvessels from normal brain tissue. In (A), which is typical of most microvessels in normal brain, only the red blood cell membranes stain for AQP1. In a few microvessels in normal brain, such as (B), the endothelial cell membranes also stain for AQP1. AQP1 immunoreactivity is upregulated in (C) low-grade and (D) high-grade astrocytoma. (E–H) Photomicrographs of carcinoma metastases to brain. In (E) the microvessel endothelium and red blood cells immunostain for AQP1. (F) Shows an AQP1 immunopositive astrocyte trapped between cancer cells. In (G) reactive astrocytes immunostain for AQP1. (H) Shows that the cells which express AQP1 also stain for GFAP. Bars=10 μm (A,B), 90 μm (C–E), 30 μm (F–H). AC=astrocytoma cells, CC=carcinoma cells, EC=endothelial cells, RA=reactive astrocytes, RC=red blood cells.