RSPO2 and glioblastoma: To further validate the potentiation role of Rspos in canonical Wnt signaling in GBM cells, we transduced U251 cells with 7TGP lentiviral vector (Additional file 1: Fig S1C) and demonstrated that the combination of Wnt3A and Rspo2 dramatically enhanced the activation of eGFP compared to Wnt3A or Rspo2 alone (Fig. 1d).