Influence of doxorubicin inclusion into phospholipid nanoformulation on its antitumor activity in mice: increased efficiency for resistant tumor model.

AIM The new formulation of doxorubicin on the base of phospholipid nanoparticles (particle size <30 nm) is elaborated in the Institute of Biomedical Chemistry (Russian Academy of Medical Sciences) on the base of plant phospholipids. The aim of study is to investigate an antitumor effect of this nanoformulation in mice with two cancer models with various sensitivity to chemotherapy — lymphoid malignancy P-388 and Lewis lung carcinoma (LLC). METHODS Nanophospholipid (NPh) formulation of doxorubicin was prepared by homogenization of soybean phosphatidylcholine and doxorubicin hydrochloride. The effect of this formulation was studied in experiments with single or threefold drug administration. Percents of tumor growth inhibition in mice under influence of free or NPh doxorubicin forms were compared. RESULTS Single administration of both free and NPh doxorubicin in mice with P-388 resulted in the same quick severe inhibition of tumor growth (60–90% depending from dose), with further gradual decrease of inhibition degree. However for more resistant tumor, LLC, the obvious advantage of NPh doxorubicin form was shown. The little effect of free doxorubicin began to reveal only after 11 days, but NPh formulation induced significant inhibition of tumor growth (40%) from the first experimental point (6 days after administration). The advantages of NPh doxorubicin was manifested particularly in low drug doses, 2 and 4 mg/kg. In other experiment design in mice with LLC, with threefold weekly drug administration, NPh doxorubicin appeared to be 2.5 times more active than free drug. The reason of the same actions of free and NPh doxorubicin form in P-388 is suggested the high drug sensitivity of this model, that gives quick high drug response for any doxorubicin form. CONCLUSION Doxorubicin in phospholipids nanoformulation revealed higher antitumor efficiency as compared with free doxorubicin in mice with LLC carcinoma. The mechanism of such changes is supposed to be caused by increase of doxorubicin availability for cancer cells.