The results illustrated that over-expression of Notch2 down-regulated the expression level of p21, but up-regulated CDK2 and cyclin E. Moreover, Notch2 over-expression could reserve the effect induced by NAC (Fig. 4f and Additional file 3:Figure S3B), demonstrating that NAC inhibited proliferation of GBM cells by altering the balance between p21 and CDK2/cyclin E via Notch2-depenent pathway. The gene discussed is CDK2; the disease is glioblastoma.