p38MAPK inhibition: a new combined approach to reduce neuroblastoma resistance under etoposide treatment

Neuroblastoma (NB) is the second most common solid pediatric tumor and is characterized by clinical and biological heterogeneity, and stage-IV of the disease represents 50% of all cases. Considering the limited success of present chemotherapy treatment, it has become necessary to find new and effective therapies. In this context, our approach consists of identifying and targeting key molecular pathways associated with NB chemoresistance. This study has been carried out on three stage-IV NB cell lines with different status of MYCN amplification. Cells were exposed to a standard chemotherapy agent, namely etoposide, either alone or in combination with particular drugs, which target intracellular signaling pathways. Etoposide alone induced a concentration-dependent reduction of cell viability and, at very high doses, totally counteracted cell tumorigenicity and neurosphere formation. In addition, etoposide activated p38 mitogen-activated protein kinase (MAPK), AKT and c-Jun N-terminal kinase. Pre-treatment with SB203580, a p38MAPK inhibitor, dramatically sensibilized NB cells to etoposide, strongly reducing the dosage needed to inhibit tumorigenicity and neurosphere formation. Importantly, SB203580–etoposide cotreatment also reduced cell migration and invasion by affecting cyclooxygenase-2, intercellular adhesion molecule-1, C–X–C chemokine receptor-4 and matrix metalloprotease-9. Collectively, our results suggest that p38MAPK inhibition, in combination with standard chemotherapy, could represent an effective strategy to counteract NB resistance in stage-IV patients.