To evaluate archival tissue specimens from bladder tumours and seek molecular changes in samples collected over seven decades previously, as although the frequencies of some cancer types have remained stable during the last 50 years, the incidence of others, including bladder tumours, has increased significantly, and molecular analyses of bladder cancer over periods with an increasing incidence are of interest as the findings might reflect varying external influences.
MATERIALS AND METHODS
Immunohistochemical staining with the biological markers p53 protein, p16 protein, epidermal growth factor receptor (EGFR), cytokeratin 7 and high molecular weight 34βE12 cytokeratin (HMW-cytokeratin, characteristic of basal cells) was used on archival, paraffin wax-embedded autopsy/biopsy tissue material collected from 144 patients with invasive bladder cancer (World Health Organisation grade II and III). The cases were selected from the periods 1932–48, 1950–59, 1960–70 and 1990–2004. Control immunohistochemistry was done on available normal tissue (i.e. connective and fatty tissue, heart, lungs and normal urinary bladder epithelium) obtained from the autopsies.
The normal tissues were all largely negative for EGFR, had <1% positively stained nuclei for p53 and strong positive reactions for p16, and in epithelial tissues the two cytokeratins were detected. The positive scores for HMW-cytokeratin in the tumour tissue decreased significantly from ≈ 90% to 30% over the 70 years. For p53 there was a higher fraction of positive scores (borderline significant) with time. The p16-positive tumours showed no significant variation, with the highest frequency of positive scores in recent years. Overexpression of EGFR in the tumours was significantly correlated with the occurrence of HMW-cytokeratin and decreased from ≈ 85% to 65% (not significant), with the lowest frequency in the samples from 1990 to 2004. Autolysis after death or long storage periods did not compromise good quality in the histochemical analyses of the autopsy tissue.
The higher frequency of HMW-cytokeratin, lower p53 accumulation and more EGFR expression in grade II and III urinary bladder carcinomas from the 1930s could indicate different phenotypes in bladder cancer during this 70-year period. The successful detection of these protein markers in old archival material allows larger retrospective studies that might increase the understanding of molecular carcinogenesis in bladder cancer.