Objective: The ultimate goal of the therapy of lung metastases is to destroy all malignant cells while sparing normal ones. Liposomes represent a novel approach for the selective transport of tracers and therapeutic agents to cancer cells because of their flexibility, low toxicity, wide range of possible variants, simplicity to make, and because agents can be entrapped in them in their native states in large amounts. We have studied the biodistribution of "Stealth" liposomes in the experimental model of lung metastases in the rat.
Methods: The secondaries were induced by i.v. injection 20. 10(6) cancer cells (DHD/K12/TRb line) in BD-IX rats. The study of the liposome biodistribution in the rat was carried out by the use of unilamellar liposomes with homogeneous size distribution (0.1 microns), the liposomes were labeled with Cholesteryl-Bodipy. The rats were sacrificed at scheduled times after the injection; blood, urine, metastatic and healthy lung, colon, liver and spleen were analysed by a microcytofluorimetric examination.
Results: Liposomes prolonged the circulation time of Cholesteryl-Bodipy. Only spleen and lung metastases exhibited an accretion of fluorescent liposomes.
Conclusions: The biodistribution of such formulation of liposomes in rats with lung metastases, may be of considerable importance in diagnosis and therapy of the secondaries, for increasing the concentration of tracers and therapeutic agents in tumor tissue while minimizing the likelihood of aspecific distribution and toxicity to non target tissue.