PTCH1 and neuroblastoma: However, none of these agonists was capable of eliciting a Hh signaling response in IMR32 or SH-SY5Y human NB cells (as measured by the expression of Hh target genes (GLI1, PTCH1)), despite the fact that all of these compounds were fully functional in NIH3T3 fibroblasts, a cell line which we used as positive control (Figure 2A).