LGR5 and neuroblastoma: Microarray data from the mutated ALK driven neuroblastoma mouse model showed an increase in LGR5 expression in aggressive MYCN amplified tumors as well as aggressive tumors with both MYCN amplification and mutated ALK which is in agreement with the data presented in our study that LGR5 is highly expressed in human cell lines derived from aggressive relapsed cell lines (http://www.ncbi.nlm.nih.gov/geoprofiles/101299025).