Fig. 4.
IDH1 activity affects the levels of HIF-1α and HIF-1α target genes in gliomas and cultured cells. (A) Overexpression of the IDH1R132H mutant in U-87MG cells stimulates expression of HIF-1α target genes (Glut1, VEGF, and PGK1) as assayed by QPCR. Shown are mean values of triplicate assays ±SD. (B) Inhibition of IDH1 by oxalomalate activates HIF-1α target genes. U-87MG cells were either untreated (control), treated with 5 mM oxalomalate, an IDH1 inhibitor, or treated with CoCl2, a hypoxia mimetic. HIF-1α target gene mRNAs were determined. Shown are mean values of triplicate assays ±SD. (C) Immunohistochemistry of HIF-1α was carried out in 12 human gliomas with wild-type IDH1 and 8 gliomas of similar grade harboring a mutated IDH1 allele. Shown are side-by-side comparisons of four gliomas representing different types or grades. Scale bar, 40 µM. Five fields (~173 µm2 each) were randomly selected from each sample for quantification of HIF-1α-positive staining area. Statistical analysis was performed using seven IDH1 wild-type and seven IDH1-mutated gliomas.