Liposomal delivery of hydrophobic RAMBAs provides good bioavailability and significant enhancement of retinoic acid signalling in neuroblastoma tumour cells

Mayuran Mathiyalakan,Elsa Irving,Michael Orford,Stephen L. Hart,Andrew W. Stoker,Aristides D. Tagalakis,Alessia Di Florio,Simon Eaton,Claire Simons,Shreya Shah,Ruhina Maeshima,Maja Bilip

doi:10.1080/1061186x.2019.1710157

Abstract

Retinoid treatment is employed during residual disease treatment in neuroblastoma, where the aim is to induce neural differentiation or death in tumour cells. However, although therapeutically effective, retinoids have only modest benefits and suffer from poor pharmacokinetic properties. In vivo, retinoids induce CYP26 enzyme production in the liver, enhancing their own rapid metabolic clearance, while retinoid resistance in tumour cells themselves is considered to be due in part to increased CYP26 production. Retinoic acid metabolism blocking agents (RAMBAs), which inhibit CYP26 enzymes, can improve retinoic acid (RA) pharmacokinetics in pre-clinical neuroblastoma models. Here, we demonstrate that in cultured neuroblastoma tumour cells, RAMBAs enhance RA action as seen by morphological differentiation, AKT signalling and suppression of MYCN protein. Although active as retinoid enhancers, these RAMBAs are highly hydrophobic and their effective delivery in humans will be very challenging. Here, we demonstrate that such RAMBAs can be loaded efficiently into cationic liposomal particles, where the RAMBAs achieve good bioavailability and activity in cultured tumour cells. This demonstrates the efficacy of RAMBAs in enhancing retinoid signalling in neuroblastoma cells and shows for the first time that liposomal delivery of hydrophobic RAMBAs is a viable approach, providing novel opportunities for their delivery and application in humans.

Highlights

Neuroblastoma is a paediatric, peripheral nervous system cancer, accounting for 15% of childhood cancer deaths [1] and it presents a stubborn clinical challenge
Retinoic acid metabolism blocking agents (RAMBAs) induction of CPY26A1 transcription. It is unclear what pattern of expression there is of CYP26 paralogues in neuroblastoma tumour cells
CYP26B1 is expressed in all lines in basal conditions and is the most abundant paralogue in KELLY and IMR32

Summary

Introduction

Neuroblastoma is a paediatric, peripheral nervous system cancer, accounting for 15% of childhood cancer deaths [1] and it presents a stubborn clinical challenge. RA induces neuroblastoma tumour cell differentiation or death in a range of neuroblastoma-derived cells in culture [3,4]. It is uncertain exactly how RA influences tumour cell behaviour in patients, the treatment does provide modest improvements in event-free survival [2,5]. The approach of dosing infants and young children with 13-cis retinoic acid (13-cis-RA) is challenging, with sub-optimal exposure [2,6] and dose-limiting toxicities [2,6]. RA action in vivo is further hampered by its rapid metabolism by cytochrome P450 enzymes in the liver and the tumour [7]. Further improvements in RA efficacy in vivo are needed and this could be relevant to a range of cancers where retinoids are employed therapeutically [10,11]

Methods

Results

Conclusion