Novel p21WAF1/CIP1 mutations in superficial and invasive transitional cell carcinomas

Alterations in the p53 gene are a predominant component in the development of transitional cell carcinoma (TCC), but the particular pathways distal to p53 alterations which contribute to urothelial transformation are not defined. Here, the p21WAF1/CIP1 gene, a p53 inducible and p53 independent gene product, was studied in TCC. p21WAF1/CIP1 expression was measured by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) from five cell lines and 28 tumor specimens (14 superficial, 14 muscle invasive). This was expressed as a ratio of the gene product to L7, a ribosomal housekeeping gene. In addition, exons 4 through 8 of the p53 gene as well as exon 2 of the p21WAF1/CIP1 gene were assayed for mutations by polymerase chain reaction/single stranded conformation polymorphism analysis (PCR/SSCP). Candidate mutations were verified by sequencing. p21WAF1/CIP1/L7 expression was significantly decreased in invasive lesions compared to superficial lesions (P<0.002). p53 mutations were detected by PCR/SSCP in seven tumors [25%] (one superficial, six invasive) and p21WAF1/CIP1/L7 expression was significantly decreased in all tumors that had p53 mutations (P<0.007). PCR/SSCP analysis of exon 2 in p21WAF1/CIP1 detected band shifts in four/28 tumor specimens (two superficial, two invasive), which sequencing and comparison to autologous normal matched DNA revealed as novel mutations.