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C

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Figure 3A: Levels of activated Ras.GTP in parental human malignant astrocytoma cell lines (U373, U343, U138, U87) and in control mouse fibroblast cells (NIH-3T3) and in mouse fibroblast cells transformed with v-Ha-Ras (RT8). Levels of activated Ras.GTP were determined using the 32P-Ras loading assay, and are expressed as a percentage of total cellular %Ras (Ras.GTP/Ras.GDP+Ras.GTP). The human malignant astrocytoma cell lines have levels of activated Ras.GTP which are similar to the transformed RT8 cells and much higher than non-transformed 3T3 cells, though they do not harbor oncogenic mutations of Ras. 3B: Femtomoles Ras-GTP normalized to mG DNA extracted from 20 human malignant astrocytoma (GBM) specimens measured by the enzymatic assay. The amount of Ras.GTP, hence Ras activity, is markedly elevated in the GBM specimens, compared to the two normal brain specimens. 3C: The mean +/- SEM of four 32P-Ras loading assays demonstrates that the U373 human malignant astrocytoma cell line stably transfected with the MMTV-Asn17 Ras inhibitory mutant has decreased Ras.GTP levels compared to MMTV transfected U373 cells. v-Ha-ras transformed RT8 fibroblasts serve as positive controls.

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