Prognostic significance of transcription factor E2F-1 in bladder cancer: Genotypic and phenotypic characterization

Background: We sought to identify and characterize potential alterations in E2F-1, a transcription factor that binds to the retinoblastoma protein (pR B), in bladder neoplasms and to elucidate a possible role for E2F-1 as an o ncogene or a tumor suppressor gene. Methods: Tumor samples from 133 evaluab le patients with bladder cancer were analyzed for E2F-1 gene mutations by u se of polymerase chain reaction-single-strand conformational polymorphism ( PCR-SSCP) analysis and DNA sequencing. In addition, tumors were studied for E2F-1 and pRB protein expression by use of immunohistochemistry. Results f rom the above analyses were correlated with clinicopathologic parameters an d outcome. All P values are two-sided. Results: A polymorphism, consisting of a nucleotide change at amino acid codon 393 in exon 7 (GGC-->AGC [Gly--> Ser]), was identified in seven of 133 case patients, being present in both tumor and corresponding normal tissues. No bandshifts were identified in th e nuclear-localization or DNA-binding domains on PCR-SSCP analysis. On immu nohistochemical analysis, E2F-1 nuclear reactivity was observed in less tha n 5% of the cells from 53 tumors and in 5%-75% of the cells from the remain ing 80 tumors, The pattern of E2F-1 protein expression was not altered in r elation to the identified polymorphism, pRB nuclear reactivity greater than 20% (of tumor cells stained) was present in 66% of the samples. E2F-1 nucl ear reactivity correlated inversely with the percentage of cells showing pR B reactivity (Kendall tau(b) = -0.18; P = .019), On multivariate analysis, patients with lower E2F-1 reactivity had statistically significantly increa sed risks of progression to metastases (P = .001) and death (P = .02), Conc lusions: E2F-1 alterations occur at the phenotypic level, rather than at th e genotypic level, in bladder cancer. The adverse outcome for patients whos e tumors exhibit low E2F-1 nuclear expression suggests a possible tumor sup pressor role for E2F-1 in bladder cancer.