Enhanced anti-tumor and anti-angiogenic efficacy of a novel liposomal fenretinide on human neuroblastoma

Neuroblastoma is an embryonal tumour originating from the simpatico-adrenal lineage of the neural crest. It approximately accounts for about 15% of all paediatric oncology deaths. Metastatic Neuroblastoma tumours at diagnosis remains a clinical challenge, despite advances in multimodal therapy. Retinoids are a class of compounds known to induce both terminal differentiation and apoptosis/necrosis of neuroblastoma cells. Among them, fenretinide (HPR), has been considered one of the most promising chemopreventive agent but it is partially efficacious due to both a scanty oral delivery and a rapid methabolism. Here, we have developed a novel liposomal HPR formulation by which the drug was encapsulated into sterically stabilized nanoliposomes (NL-[HPR]) according to the reverse-phase evaporation method. This procedure led to a high drug encapsulation and stability in organic fluids. Moreover, the liposomes were further coupled with NGR peptides for targeting the tumour endothelial cell marker, aminopeptidase N (NGR-NL-[HPR]). Orthotopic neuroblastoma xenografted -bearing mice treated with NGR-NL-[HPR] lived statistically longer than mice un-treated or treated with free HPR (NGR-NL-[HPR] vs both control and HPR: P<0.0001). NL-[HPR] resulted in a statistically improved survival (NL-[HPR] vs both control and HPR: P<0.0001) but with a less extent if compared with that obtained with NGR-NL-[HPR] (NL-[HPR] vs NGR-NL-[HPR]: P=0.01). Staining of primary tumour sections with antibodies specific for neuroblastoma and for either pericytes or endothelial cells evidenced that HPR reduced neuroblastoma growth through both antitumour and angiostatic effects, mainly when delivered by NGR-NL-[HPR]. Indeed, in this group of mice a marked reduction of intratumoral vessel counts and VEGF expression, together with a down-modulation of both matrix metalloproteinases MMP2 and MMP9, were observed. In conclusion, the use of this novel targeted delivery system for the apoptotic and anti-angiogenic drug, fenretinide, could be considered as an adjuvant tool in the future treatment of neuroblastoma patients.