Effects of NOTCH1 re-expression on UC cell lines. (A) Five independent colony forming assays with triplicate plates for each experiment after transfection of plasmid constructs expressing NOTCH1 intracellular domain (N1ICD) or full-length protein (N1-FL) compared to control constructs. Clone numbers were counted after selection for three weeks with either G418 (pIRES-N1ICD/pIRES-2) or Zeozin (pcDNA4to-N1-FL/pcDNAto-lacZ). The student’s T Test was carried out for statistical analysis. Colony forming potential was significantly decreased in N1ICD and N1-FL transfected cells. (B) Nuclear abnormalities typically appearing after transfection of N1ICD into UC cell lines. Note nuclear enlargements, deformation, micronuclei, fragmentation, multinuclearity and mitotic catastrophe in cells expressing N1ICD (green) as compared to others. DNA was counterstained with DAPI (blue). Further analysis is shown in Additional file 1: Table S4.