Potential use of drug carried-liposomes for cancer therapy via direct intratumoral injection

Liposomes have recognized advantages as nano-particle drug carriers for tumor therapy. In this study, the pharmacokinetics and distribution of intratumorally administered liposomes were investigated as drug carriers for treating solid tumors via direct intratumoral administration. Tc-99m-liposomes were administered intratumorally to nude rats bearing human head and neck squamous cell carcinoma xenografts. Planar gamma camera images were analyzed to evaluate the local retention of the intratumorally administered liposomes. Co-registered pinhole micro-single photon emission computed tomography (SPECT)/computed tomography (CT) images were acquired of the whole animal as well as the dissected tumors to determine intratumoral distribution of the Tc-99m-liposomes. For Tc-99m-liposomes, there was an initial retention of 47.4 +/- 11.0% (n =4) in tumors and surrounding tissues. At 20 h, 39.2 +/- 10.6% (n=4) of Tc-99m-activity still remained in the tumor. In contrast, only 18.7 +/- 3.3% (re=3) of the intratumoral Tc-99m-activity remained for unencapsulated Tc-99m-complex at 20 h. Pinhole micro-SPECT images demonstrated that Tc-99m-liposomes also have a superior intratumoral Tc-99m-activity diffusion compared with unencapsulated Tc-99m-complex. Higher intratumoral retention of Tc-99m-liposomes accompanied by an improved intratumoral diffusion suggests that intratumorally administered liposomal drugs are potentially promising agents for solid tumor local therapy. (c) 2006 Elsevier B.V. All rights reserved.