Microvessel Damage May Play an Important Role in Tumoricidal Effect for Murine H22 Hepatoma Cells with Hyperthermia In Vivo

BackgroundIn the present study, murine H22 hepatoma cells were provided hyperthermia with different thermal dose in vitro and in vivo, thereafter we investigated the apoptosis, necrosis rates, and intratumoral microvessel density (MVD) to determine that microvessel damage plays an important role in the tumoricidal effect of hyperthermia.MethodsH22 hepatoma cells were inoculated in the right hind legs of mice with immunosuppression. Local hyperthermia was administered to these mice for 15, 30, and 45 min, respectively. After hyperthermia, some mice with heat treatment of 30 min were killed at 3, 6, 12, 24, 48, 72, and 96 h after operation and others were immediately sacrificed. All tumor tissues were removed. They were analyzed for the death rate of tumor cells by flow cytometer (FCM) and observed MVD by immunohistochemistry. H22 hepatoma cells in vitro were also given hyperthermia for 15, 30, and 45 min, respectively, and analyzed for the death rate by FCM.ResultsMost of the dead cells were apoptotic cells in the initiation phase of hyperthermia, then the necrosis rates rose gradually. The difference of death rates between in vivo and in vitro was significant for hyperthermia for 15 min, 30 min, and 45 min (P < 0.05). A strong positive linear correlation (r = −0.879) was observed between the death rate of tumor cells and MVD.ConclusionOur study has shown that microvessel damage may play an important role in tumoricidal effect of hyperthermia.