Introduction: According to Warburg, irreversible cellular respiratory damage causes cancer cells to depend entirely upon aerobic glycolysis. We propose that targeting aerobic metabolism will be an effective strategy for treating gliomas.
Methods: Glioblastoma (GBM) cell lines U87, U251, LN229, and CCF 247; a primary
line obtained from our brain tumor bank, were used for in vitro studies. Normal human astrocytes (HA) obtained from normal brain from epilepsy surgery patients, were also evaluated in vitro. Cells were treated with 3-Bromopyruvate (3-BrPA), a lactate/pyruvate analog which selectively depletes ATP and inhibits Hexokinase-2 dependent aerobic metabolism. We evaluated the effects of 3-BrPA treatment with use of TUNEL (DNA Flow Cytrometric Analysis Kit, Roche Diagnostic Corp) and flow cytometry (Becton Dickinson FACScan, San Jose, Ca.). Caspase activity was measured using the Apo-ONE Homogeneous Caspase-3 assay (Promega, Madison, WI).
Institutional animal facility approval was obtained for in vivo studies. U87 cells were implanted in the flank of athymic nude rats. Ten days later, rats were treated with either 3-BrPA or PBS by direct tumor injection every forty eight hours for two weeks. Tumors were measured every forty eight hours and tumor volume was calculated.
Results: Cells were treated with 3-BrPA at doses ranging from 500 micromolar to 15 millimolar for 48 hours. TUNEL analysis showed evidence of apoptosis in more than 95% of GBM cells (all cell lines) following 3-BrPA treatment at any dose, compared to HA which showed 20% apoptosis (P<0.005).
In vivo experiments showed decreased tumor size in treated rats over the course of injections. Tumor size increased in control group. After stopping treatment, tumors have continued to decrease in size in the treated animals and have not returned after three months.
Conclusions: Animals treated with 3-BrPA showed tumor regression without apparent toxicity or recurrence. These findings attest to the feasibility of completely destroying advanced, highly glycolytic brain tumors.
Patient Care: We believe that treating brain tumors by anti-glycolytic therapy would alleviate much of the stress and discomfort associated with conventional treatment as well as offer a new approach to treatment of pediatric and adult brain tumors.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of the role metabolism plays in brain tumors. 2) Discuss, in small groups, how using glycolytic agents affects tumor progression. 3) Identify an effective treatment for primary gliomas.