Preparation and cytotoxicity of cisplatin-containing liposomes

A.D Carvalho Júnior,G.A Ramaldes,E.C Pereira-Maia,M.C De Oliveira,J.N Silveira,F.P Vieira,A Garnier-Suillerot,V.J De Melo,M.T.P Lopes

doi:10.1590/s0100-879x2006005000125

Abstract

We encapsulated cisplatin into stealth pH-sensitive liposomes and studied their stability, cytotoxicity and accumulation in a human small-cell lung carcinoma cell line (GLC4) and its resistant subline (GLC4/CDDP). Since reduced cellular drug accumulation has been shown to be the main mechanism responsible for resistance in the GLC4/CDDP subline, we evaluated the ability of this new delivery system to improve cellular uptake. The liposomes were composed of dioleoylphosphatidylethanolamine (DOPE), cholesteryl hemisuccinate (CHEMS), and distearoylphosphatidylethanolamine-polyethyleneglycol 2000 (DSPE-PEG2000) and were characterized by determining the encapsulation percentage as a function of lipid concentration. Among the different formulations, DOPE/CHEMS/DSPE-PEG liposomes (lipid concentration equal to 40 mM) encapsulated cisplatin more efficiently than other concentrations of liposomes (about 20.0%, mean diameter of 174 nm). These liposomes presented good stability in mouse plasma which was obtained using a 0.24-M EDTA solution (70% cisplatin was retained inside the liposomes after 30 min of incubation). Concerning cytotoxic effects, they are more effective (1.34-fold) than free cisplatin for growth inhibition of the human lung cancer cell line A549. The study of cytotoxicity to GLC4 and GLC4/CDDP cell lines showed similar IC50 values (approximately 1.4 microM), i.e., cisplatin-resistant cells were sensitive to this cisplatin formulation. Platinum accumulation in both sensitive and resistant cell lines followed the same pattern, i.e., approximately the same intracellular platinum concentration (4.0 x 10-17 mol/cell) yielded the same cytotoxic effect. These results indicate that long-circulating pH-sensitive liposomes, also termed as stealth pH-sensitive liposomes, may present a promising delivery system for cisplatin-based cancer treatment. This liposome system proved to be able to circumvent the cisplatin resistance, whereas it was not observed when using non-long-circulating liposomes composed of phosphatidylcholine, phosphatidylserine, and cholesterol.

Highlights

Introduction cisDiamminedichloroplatinum (II) (CDDP) or cisplatin is one of the most effective chemotherapeutic agents used for the treatment of ovary, lung, testicle, head, and neck carcinoma [1,2,3,4,5]
Four main events accompany it in most cases: i) decreased accumulation of drug concentration, ii) increased levels of sulfur-containing molecules such as glutathione or metallothionein, iii) enhanced repair of DNA damage caused by CDDPDNA adducts by nucleotide excision repair proteins such as ERCC1, XPA, and XPB which can remove DNA adducts produced by CDDP, and iv) increased tolerance to CDDP-DNA adducts as a consequence of deficiencies in the mismatch repair system and enhanced replication bypass [15,16,17,18]
In the present study, we investigated the encapsulation of CDDP into stealth pH-sensitive liposomes, the cytotoxic activity of the preparation, and its ability to circumvent CDDP resistance using A549, A431, BHK-21, and GLC4, GLC4/CDDP cell lines, respectively

Summary

Introduction

Introduction cisDiamminedichloroplatinum (II) (CDDP) or cisplatin is one of the most effective chemotherapeutic agents used for the treatment of ovary, lung, testicle, head, and neck carcinoma [1,2,3,4,5]. We encapsulated cisplatin into stealth pH-sensitive liposomes and studied their stability, cytotoxicity and accumulation in a human small-cell lung carcinoma cell line (GLC4) and its resistant subline (GLC4/CDDP). In the present study, we investigated the encapsulation of CDDP into stealth pH-sensitive liposomes, the cytotoxic activity of the preparation, and its ability to circumvent CDDP resistance using A549, A431, BHK-21, and GLC4, GLC4/CDDP cell lines, respectively.

Results

Conclusion