CASP3 and retinoblastoma: Interestingly, we found that Nodal plays an important role in maintaining retinoblastoma cell survival, as we observed a significant induction in the apoptotic markers, such as cleaved PARP1 and in cleaved caspase-3 (using immunoblotting and immunofluorescence assays, respectively), in retinoblastoma cells expressing Nodal shRNA compared to scrambled shRNA.