Enhancement of ATRA-induced differentiation of neuroblastoma cells with LOX/COX inhibitors: an expression profiling study

Caffeic acid, as an inhibitor of 5-lipoxygenase, and celecoxib, as an inhibitor on cyclooxygenase-2, were used in this study. Expression profiling was performed using Human Cancer Oligo GEArray membranes that cover 440 cancer-related genes.Cluster analyses of the changes in gene expression showed the concentration-dependent increase in genes known to be involved in the process of retinoid-induced neuronal differentiation, especially in cytoskeleton remodeling. These changes were detected in both cell lines, and they were independent of the type of specific inhibitors, suggesting a common mechanism of ATRA-induced differentiation enhancement. Furthermore, we also found overexpression of some genes in the same cell line (SK-N-BE(2) or SH-SY5Y) after combined treatment with both ATRA and CA, or ATRA and CX. Finally, we also detected that gene expression was changed after treatment with the same inhibitor (CA or CX) in combination with ATRA in both cell lines.Obtained results confirmed our initial hypothesis of the common mechanism of enhancement in ATRA-induced cell differentiation via inhibition of arachidonic acid metabolic pathway.The therapeutic approach based on induced cell differentiation of transformed cells into mature phenotypes is one of the most promising strategies in recent anti-neoplastic treatment. Retinoids represent the most frequently used group of differentiation inducers, both in leukemias and in some types of solid tumors [1-6]. However, evidence of potential toxicity and intrinsic or acquired resistance substantially limits the use of retinoids in clinical protocols.Special attention has thus been paid to the combined treatment with retinoids and other compounds that are able to enhance or modulate the differentiation effect of retinoids. For example, all-trans retinoic acid (ATRA)-induced cell differentiation in the HL-60 leukemia cell line can be enhanced either by combined treatment with bile acids [7,8] or with inhibitors of the arachidonic a