ALTERATIONS OF TP53 IN MICRODISSECTED TRANSITIONAL-CELL CARCINOMA OF THE HUMAN URINARY-BLADDER - HIGH-FREQUENCY OF TP53 ACCUMULATION IN THEABSENCE OF DETECTED MUTATIONS IS ASSOCIATED WITH POOR-PROGNOSIS

We have used microdissection of paraffin-embedded histological section s and polymerase chain reaction (PCR)-based direct DNA sequencing for 54 transitional cell carcinoma (TCC) of the bladder, to examine critic ally the association between TP53 nuclear accumulation determined by i mmunohistochemistry and the presence of TP53 mutations, and to examine their relationship to tumour stage and grade, as well as patient surv ival. There was a significant association between the presence of TP53 -positive nuclei (> 10%) and a higher histological stage and grade (P = 0.0115, P = 0.0151 respectively; Fisher's exact), A significant asso ciation between TP53 gene mutations and TP53 nuclear reactivity in mor e than 10% of tumour cell nuclei was also observed (P = 0.0003; Fisher 's exact), Mutations were detected in 18/54 (33%) cases together with the wild-type sequence when analysed from bulk frozen samples, with si gnificant clustering of mutations in exons 7 and 8. The microdissectio n method distinguished more clearly between heterozygous and/or homozy gous alterations of the TP53 tumour-suppressor gene, and clearly showe d frequent accumulation of TP53 in the absence of mutations. When micr odissecting immunonegative regions from the same paraffin sections, th ree out of ten samples showed the identical mutations detected in the immunopositive regions. There was a significant association between TP 53 immunoreactivity in more than 50% of tumour cell nuclei and decreas ed survival among ail patients (P = 0.0325; log-rank test). The patien ts with TP53 mutations showed a trend for a shorter survival period; h owever, the association was not statistically significant at the 95% c onfidence level (P = 0.132; log-rank test). In conclusion, our observa tions show that accumulation of TP53 occurs frequently in the absence of mutations, and that such accumulation is nevertheless associated wi th poor survival when it occurs in a high proportion (> 50%) of tumour cell nuclei.