TPP-Based Nanovesicles Kill MDR Neuroblastoma Cells and Induce Moderate ROS Increase, While Exerting Low Toxicity Towards Primary Cell Cultures: An In Vitro Study

Neuroblastoma (NB) is a malignant childhood tumour, which originates from neuroblasts with an incidence of approximately 15,000 new cases per year worldwide. Therapy-induced secondary tumorigenesis and the emergency of drug resistance in its high-risk (HR-NB) forms drive to a survival rate of <50%, despite aggressive treatments. Our recent research is focused on testing in vitro the effects of synthetized triphenyl phosphonium (TPP)-based bola amphiphilic nanovesicles (BPPBs) against both drug-sensitive and multi-drug-resistant (MDR) cancer cell lines. In the present study, BPPB demonstrated sub-micromolar IC₅₀ values (0.4-0.9 µM) towards drug-sensitive HTLA 230, while 1.20-1.35 µM IC₅₀ were determined on MDR HTLA ER. Noteworthily, we have demonstrated that BPPB triggers apoptosis of both NB cell populations. Additionally, since MDR NB cells (HTLA ER) are equipped with higher levels of antioxidants than sensitive ones (HTLA 230), the potential involvement of reactive oxygen species (ROS) in the cytotoxic action of BPPB was also investigated. Then, a novel analytical approach was applied to the results of cell viability and ROS monitoring for their better interpretation. Proper dispersion graphs and their best fitting nonlinear regression models were used to verify if the cytotoxic effects of BPPB could depend on BPPB concentrations, exposure times, and/or ROS generation, and if ROS increase could depend on BPPB concentrations and/or exposure times. A ROS-dependent mechanism was found in 24 h and 24/48 h treatments of HTLA ER and HTLA 230, respectively. Furthermore, the potential clinical development of BPPB as a new curative option for children affected by HR-NB was assessed by testing BPPB on astrocyte and neuron primary cell cultures, and analytical correlation studies were used to interpret the results. Notably, BPPB administration was sufficiently and well tolerated by neurons and astrocytes, respectively, allowing selectivity index values of up to 23.7. These in vitro results, associated with the low haemolytic activity of BPPB, pave the way for future in vivo investigations and, upon confirmation, for the possible development of BPPB as a novel therapeutic strategy to treat MDR HR-NB.