Targeting gemcitabine containing liposomes to CD44 expressing pancreatic adenocarcinoma cells causes an increase in the antitumoral activity

Pancreatic adenocarcinoma is often diagnosed when metastatic events have occurred. The early spread of circulating cancer cells expressing the CD44 receptor may play a crucial role in this process. In this study, we have investigated the cellular delivery ability and both in vitro and in vivo anti-tumoral activity of liposomes conjugated with two different low molecular weight hyaluronic acids (HA 4.8 kDa and HA 12 kDa), the primary ligand of CD44, and containing a lipophilic gemcitabine (GEM) pro-drug. By confocal microscopy and flow cytometry analyses, we demonstrate that the cellular uptake into a highly CD44-expressing pancreatic adenocarcinoma cell line is higher with HA-conjugated (12 kDa >4.8 kDa) than non-conjugated liposomes. Consistently, in vitro cytotoxic assays display an increased sensitivity towards GEM containing HA-liposomes, compared to non-conjugated liposomes. Conversely, CD44 non-expressing normal cells show a similar uptake and in vitro cytotoxicity with both HA-conjugated and non-conjugated liposomes. Furthermore, we demonstrate that the HA-liposomes are taken up into the cells via lipid raft-mediated endocytosis. All the liposome formulations containing GEM show a higher antitumoral activity than free GEM in a mouse xenograft tumor model of human pancreatic adenocarcinoma. The 12 kDa HA-liposomes have the strongest efficiency, while non-conjugated liposomes and the 4.8 kDa HA-liposomes are similarly active. Taken together, our results provide a strong rationale for further development of HA-conjugated liposomes to treat pancreatic adenocarcinoma. (C) 2013 Elsevier B.V. All rights reserved.