MTOR and soft tissue sarcoma: Rapamycin at the concentration of 100 nM, which is significantly higher than the dose needed to inhibit S6K phosphorylation via mTOR, as described in human soft tissue sarcoma cell lines [29], did not radiosensitize HTB-182 (DMF, 0.95), SK-MES-1 (DMF, 0.88) or MDA-MB-231 cells (DMF, 1.03) (Fig 1B).