Temsirolimus is an inhibitor of the mammalian target of rapamycin (mTOR), a crucial regulator of cell cycle progression. It was approved in the treatment of advanced renal cell carcinoma. Temsirolimus demonstrated also antitumor activity in a variety of other human cancer models, such as gliomas, rhabdomyosarcomas, neuroblastomas, prostata and breast cancer through induction of apoptosis or inhibition of proliferation. A similar effect was noted in HNSCC cell lines.