ZEB1 and viral infectious disease: For the cultured OCM1-ZEB1sh and C918-ZEB1sh cells, though all selected by puromycin right after the ZEB1sh viral infection (the viral vector contains both puromycin resistance and EGFP genes) there were still about 20% cells with dim EGFP expression due to less viral insertion numbers thereby less downregulation of ZEB1 (Fig. 5F1,G1).