Comparative Evaluation of Cardiotonic Steroid Action on the Viability of Differentiated and Undifferentiated Human Neuroblastoma SH-SY5Y Cell Culture

Neuroblastoma (NB) is one of the most common childhood cancers. While it affects adults far less frequently than children, the prognosis for adults is significantly poorer. CTS, which are specific inhibitors of the Na+,K+-ATPase, are known to be cytotoxic to cancer cells. However, the mechanisms behind their differential effect on cancerous and mature cells are poorly understood. We used the SH-SY5Y NB culture to investigate these effects. We showed that the CTS ouabain, digoxin, and bufalin are toxic for both undifferentiated and differentiated SH-SY5Y neuroblastoma in the concentration range of 10–100 nM. Digoxin at a concentration of 100 nM, bufalin at a concentration of 10 nM. However, ouabain was an order of magnitude more toxic for the undifferentiated (10 nM) culture than for the differentiated (100 nM) culture. It was also shown that differentiation of SH-SY5Y neuroblastoma using retinoic acid causes a manifold increase in dopamine secreted by the culture into the culture medium. At the same time, ouabain causes a decrease in the amount of dopamine secreted by both undifferentiated and differentiated SH-SY5Y neuroblastoma. The toxic effect of ouabain in undifferentiated culture is associated with a decrease in the amount of anti-apoptotic protein Bcl-2. It was also shown that the toxic effect of ouabain on the undifferentiated culture of SH-SY5Y neuroblastoma is associated with PKC activity, since the addition of the PKC inhibitor chelerythrine neutralized the toxic effect of 10 nM ouabain. In all, our data suggests that CTS are important for future investigation of the differential effect of anticancer compounds on dividing cells and mature neurons.