Objective: To analyze the correlation between the genotypic and phenotypic patterns of p53 in patients with transitional cell carcinoma (TCC) of the urinary bladder.
Materials and methods: Cross-sectional study of 73 patients diagnosed with TCC. DNA was obtained from the tumor tissue to perform polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) of exons 5-9 of the p53 gene, with automatic sequencing done on any mutated samples. Immunohistochemistry (IHC) was also performed using anti-human P53 monoclonal antibody, and the diagnostic performance of this test was analyzed by a ROC curve, using the presence of p53 mutations found by PCR-SSCP as 'gold standard'.
Results: The cutoff point for defining immunopositivity was 20%. IHC had a specificity of 62.9%, and a sensitivity of 65.8%. The highest sensitivity values appeared in G3 tumors (75%) and infiltrating tumors (71.4%), and the highest specificity values were observed in G1 (77.7%) and G2 tumors (90%) and superficial tumors (66.6%). Mutations in exon 8 gave a positive result most frequently (73.7%) and were considered most relevant in terms of altering P53 function (60.9%). False negatives were documented in 28.5% of infiltrating tumors, and false positives in 33.4% of superficial tumors.
Conclusions: There is a moderate correlation between p53 mutations and P53 protein overexpression, with this stronger in high-grade, infiltrating tumors, in exon 8 mutations, and when the mutation induces relevant changes in the protein structure. Although IHC is useful in routine clinical practice, the classic prognostic factors should still be considered the most important in the follow-up of these patients.
(c) 2007 S. Karger AG, Basel.