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Archive - Jun 24, 2013


New Understanding of Why mTOR-Suppression-Based Cancer Therapy Stops Working at a Specific Stage

Researchers at the Hebrew University of Jerusalem and in California have achieved a breakthrough in understanding how and why a promising anti-cancer therapy has failed to achieve hoped-for success in killing tumor cells. Their work could lead to new insights into overcoming this impasse. The problematic therapy investigated involves suppression of the protein mTOR (mammalian target of rapamycin). mTOR plays an important role in regulating how cells process molecular signals from their environment, and it is observed as strongly activated in many solid cancers. Drug-induced suppression of mTOR has until now shown success in causing the death of cancer cells in the outer layers of cancerous tumors, but has been disappointing in clinical trials in dealing with the core of those tumors. Reduced oxygen supply -- hypoxia -- is a near-universal feature of solid tumors that can alter how tumors respond to therapies. It was known that the behavior of mTOR signaling is influenced and altered by the condition of hypoxia, but the mechanism to explain this was unknown. A research team, which included Professor Emeritus Raphael D. Levine of the Institute of Chemistry at the Hebrew University of Jerusalem and researchers from the California Institute of Technology and the David Geffen School of Medicine at UCLA, investigated whether the influence of hypoxia on mTOR signaling in model brain cancer systems could explain the poor performance of mTOR drugs. Their work appeared in a recent article in PNAS. For their investigation, they employed a new microchip technology that allowed them to measure the mTOR protein signaling network in individual cancer cells, and they interpreted the results using a new set of theoretical tools derived from the physical sciences. The combined approach permitted the simplification of an otherwise complex biological system.