Transferrin receptor 2 mRNA expression in normal brain and brain tumors detected by real-time PCR. The expression is normalized using internal control genes and relative expression levels are shown. *Abbreviations used for normal brain: Cx = cortex, Cb = cerebellum, T = thalamus, M = medulla oblongata, H = hippocampus. Tumor samples are numbered according to Table 1. Numbers 19 to 21 are used to indicate cell lines: 19 = CCF-STTG1, 20 = U373MG, 21 = U-87 MG. **Roman numbers in astrocytomas indicate tumor grade.