Enhancement of hyperthermia lethality by Lanthanum.

The authors have studied the effects of La3+ during hyperthermia on tumor cells, Trypan blue exclusion and 86Rb release from previously labeled Ehrlich and DS carcinosarcoma ascites cells, indicate an increase of plasma membrane permeability by La3+ as a function of the hyperthermic level. The enhancement of hyperthermia lethality by concentration of Lanthanum over 0.5 mM after 2 hours at 44 degrees C has been demonstrated on HeLa S3 cells using a well known cloning technique. In vivo experiments have been performed on Rhabdomyosarcoma C3H bearing mice using an ultrasound heating technique at 44-46 degrees C. The preliminary in vivo results show a remarkable tumor growth inhibition and a significant increase of the survival time after only one hyperthermia treatment of 30 minutes combined with one intratumoral injection of 1 mM lanthanum. The control animal groups treated by hyperthermia alone or by lanthanum alone don't show any differences of the tumor volume evolution in comparison with untreated animal groups.