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Previous studies have indicated that expression of calcitonin receptor (CTR) could be induced in a proinflammatory environment. In the present study, CTR-immunoreactivity (CTR-ir) was investigated in brain tissue from patients with glioblastoma multiforme (GBM).In immunohistochemical analysis of GBM samples, tissues with complex glomeruloid structures surrounded by malignant cells were analysed for CTR-ir using anti-human CTR antibodies generated against two separate epitopes of CTR. CTR-ir was associated predominantly with glial cells. Regions with CTR-ir cells were found in 12 of 14 GBM tumours (P < 0.05). Using confocal microscopy, CTR-ir cells were identified that were also positive for glial fibrillary acidic protein, nestin and CD133. Antibodies were verified using immunoblots and confocal microscopy of the Cercopithecus aethiops(COS)-7 transfectants. Immunoblots of membrane preparations from the CTR-positive cell lines demonstrated a major band (≈ 67 kDa) and minor band (≈ 52 kDa), but the intensity was reversed for the GBM cell line A172. In cultured A172 cells, functional studies demonstrated calcitonin stimulation of adenylyl cyclase and inhibition of extracellular-regulated kinase (ERK)1/2 phosphorylation.The findings that (i) CTR was expressed by glioma cells in a majority of GBM tumours tested, (ii) CTR(+) /CD133(+) cells were identified and (iii) second messenger systems were functionally modified by calcitonin in A172 cells suggest that CTR might be a useful therapeutic target in GBM. |
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