HIF1A and neoplasm: In murine xenograft models of rhabdomyosarcoma cell lines (Rh30 and RD), treatment with temsirolimus was effective in inhibiting tumor growth.45 The antitumor activity of temsirolimus was associated with a reduction of HIF-1α levels and VEGF protein expression and with decreased microvessel density in Rh30-derived and RD-derived tumors, demonstrating suppressed tumor growth through an antiangiogenic mechanism.