Cell penetration enhancer (CPE, DAG-Arg₄) enhances Doxorubicin Liposomes Penetration and Pharmacological Efficacy in 4T1 Murine Breast Cancer Model

Introduction

Decoration of liposomes with cell penetration enhancer (CPE) groups facilitates their interaction with the cell membranes and enhances their permeability via biological barriers. However, there is a need to combine the CPE with additional surface groups (e.g., PEG) to modulate the liposomes permeability in the different parts of the body: a) to avoid excessive distribution from the bloodstream to the different organs and tissues (which leads to toxicity), and b) to enhance tumor accumulation and permeability (which governs anti-cancer efficacy¹).

Objective

To determine the influence of the CPE (DAG-Arg₄) surface groups, in combination with poly(ethylene glycol)-based compound (mPEG-DSPE), on anticancer effects of doxorubicin liposomes in a 4T1-Luc murine orthotopic breast cancer model.

Experimental methods

We generated doxorubicin liposomes¹ decorated with the DAG-Arg₄ (tetra-Arg-[G-1]-distearoyl glycerol), and/or mPEG-DSPE (methoxy-PEG-5kDa-distearoylphosphatidylethanolamine)² groups, and extensively characterized them in vitro. In in vivo study, 4T1-Luc cells were injected into the mammary fat pad of eight-weeks-old female BALB/c mice, and the tumor volume and body weight were measured daily. From day 10 after tumor inoculation, the animals received IV injections of the studied liposomal formulations (equivalent to 9 mg/kg doxorubicin * 3 weekly doses). On day 38, tumors and internal organs were excised, weighed and analyzed.

Results and conclusions

We used liposomes decorated with 4% DAG-Arg4 and 5% mPEG-DSPE, based on the in vitro stability and permeability data. Surface groups affected liposomes association with 4T1-Luc cells in vitro: DAG-Arg₄ (68.7±0.4%) > mPEG-DSPE and DAG-Arg₄ (17.5±4.9%) > non-decorated liposomes (4.23±0.9%). In vivo anti-cancer efficacy of the liposomal formulations (tumor volume) matched in vitro data: mPEG-DSPE and DAG-Arg₄ (209±66mm³) < mPEG-DSPE (287±30mm³) < non-decorated liposomes (479±72mm³). The influence of the DAG-Arg₄ (cell association and permeation enhancer), alone and in combination with the PEG-based agents (masking and stabilizing compounds), should be further investigated and compared to other types of CPE in order to enhance tumor accumulation and permeability, anti-cancer efficacy and safety of liposomal formulations.

References

1. Barattin et al., pH-controlled liposomes for enhanced cell penetration in tumor environment. ACS Appl Mater Interfaces, 2018
2. Doxil® — The first FDA-approved nano-drug: lessons learned. J Control Release, 2012