p53 in normal esophageal epithelial cells and esophageal cancer cells. A. The p53 protein and its domain structure (modified from ). The normal esophageal epithelium cell line EPC-hTERT carries no p53 mutation whereas all esophageal cancer cell lines exhibit mutations of p53, but each in a different functional domain. Mutations are indicated by arrows (↓) and possible protein truncations by crosses (×). B. Photograph of p53 protein expression by immunoblot analysis, representative for 3 independent experiments. Due to mutations, the p53 protein of OE21 and OE19 is truncated, resulting in protein masses of about 14 kDa and 40 kDa, respectively. For OE19 this shift in protein mass was seen at the immunoblot (asterisks), the 14 kDa protein of OE21 cells was below the size of detectable proteins in these 10% SDS gels. β-Actin served as laoding control. C. p53 indirect immunofluorescence (green) and DNA counterstaining by DAPI (blue). Mutated p53 accumulates in the nucleus of Kyse-410, OE33 and OE19 cells. The truncated p53 protein of OE21 cells lacks almost all protein domains and is only weakly expressed. Refer to text for discussion of p53 mutations.