Researchers at the University of Toronto and Washington University, including Children’s Tumor Foundation-funded investigators, have published* observations suggesting that Rapamycin, a drug currently in Phase II clinical trials for benign NF1 plexiform neurofibromas, may have limited use – at least when used alone – in the treatment of the malignant peripheral nerve sheath tumors (MPNSTs) that can occur in NF1. Study authors included recipients of Children’s Tumor Foundation Young Investigator Awards (Joydeep Mukherjee and Sutapa Banerjee) and Drug Discovery Initiative Award (Abhijit Guha). The team assessed Rapamycin’s effects on the growth of MPNST tumor cells that had been implanted into mice. Rapamycin did stop the implanted malignant tumor cells from dividing, and also stopped the growth of new blood vessels into the tumors – an important indicator that growth was being halted. However cell death (another important hallmark of drug effectiveness) was not seen in the tumors. Also, while Rapamycin quieted the activity of one tumor signaling pathway (mTOR), another important tumor signaling pathway (Akt) remained active. These results suggest that Rapamycin, at least if used as a single drug treatment, most likely has limited use in treating malignant tumors. However, the potential remains open that Rapamycin may be effective if dosed in combination or sequentially with other drugs that target different signals – a theme that has repeated in drug therapy reports this year.
Foundation-Funded Research Shows Utility, Limitations of Rapamycin for treating NF1 Malignant Tumors
