High-risk neuroblastoma has poor survival rates, and novel therapies are needed. Well-chosen drug combination strategy can provide new opportunities.
13-cis-retinoic acid (13-RA) is a differentiating agent used in most current treatment regimens while naturally occurring polyphenols have been shown to exert anti-proliferative effects in a wide variety of cancer cell lines. The purpose of this study was to identify natural products potentiating the impact of 13-CRA against neuroblastoma cells and investigate the molecular mechanisms behind.
A library of about 160 natural compounds was screened for the viability of CHP134 cells challenged with a sublethal dose of for 48h. The in vitro screening identified a flavonoid, isorhamnetin, as a potential enhancer of activity in cells. Median effect analysis of drug combination revealed that isorhamnetin exerted synergistic inhibition of the growth of neuroblastoma cells both at 24h and 48h treatment, leading to 80% reduction in cell viability.
Flow cytometry and microscope investigations also revealed cell cycle arrest in G0/G1 phase and enhanced apoptosis. Microarray gene expression analysis at polysomal RNA level pointed out that combination treatment of plus isorhamnetin led to coherent perturbations of gene expression including a negative regulation of cell proliferation and specific neural cell differentiation gene pathway and up-regulation of specific G protein-coupled receptor downstream signaling, cell cycle arrest, apoptosis gene sets. Our findings also allowed us to advance an hypothesis on the molecular mechanism of this pharmacological synergism, centered on the elicited 30-fold increased of the alpha-1 adrenergic receptor expression.
Taken together, these data demonstrate that the combination of with isorhamnetin at therapeutically relevant concentrations is more efficient than the sum of each single compound alone in inhibiting neuroblastoma cell growth in vitro, suggesting potential therapeutic capabilities.