Abstract 300: Identification of a panel of protein markers associated with disease progression in bladder cancer
Authors: Birkenkamp-Demtroder Karin , Dyrskjøt Lars , Mansilla Francisco , Ørntoft Torben F. 
Published: June 2012

Most bladder cancer patients are initially diagnosed with noninvasive or superficially invasive urothelial tumors, comprising benign low grade Ta tumors that rarely progress to high grade T1 tumors with concomitant CIS that progress in up to 60% of cases. So far, no biomarkers are available for solid prediction of the individual disease course.

Previously, we identified an 88-transcript signature for prediction of progression for patients with non-muscle invasive bladder cancer.

Aim: validation of key candidate markers on the protein level.

We selected four protein coding genes, where high transcript levels were related to a reduced risk of progression and five genes where high expression identified patients with an increased risk of progression.

Microarray transcript profiling data on 7 bladder cancer cell lines were used to select appropriate model cell lines. Specificity of antibodies against the selected proteins, protein expression and potential splice variants were investigated by western blotting using extracts from bladder cancer cell lines (T24, SW780) and HeLa cells. Specific antibodies were identified for six of the nine selected proteins. Immunohistochemistry was applied to a Tissue-microarray with 289 primary non-muscle invasive urothelial tumors (182 pTa, 101 pT1 and 6 CIS). 118 patients later experienced disease progression to pT2-4 bladder cancer (median time to progression 22 months). None of the remaining 171 patients showed later disease progression within the follow-up period (median follow-up 93 months).

In univariate Cox regression analysis, expression of 4 of the 6 proteins correlated significantly with disease progression from stage Ta or T1 to muscle invasive bladder cancer. A reduced risk of progression correlated significantly with a strong nuclear expression of the G1/S-specific cell cycle protein (p=0.0003) and its expression in &gt;80% nuclei (p=0.0004) as well as a membranous localization of a disintegrin and metallopeptidase (p = 0.0002). Increased risk of progression correlated significantly with strong nuclear and cytoplasmic expression of an ubiquitin-conjugating enzyme (p=0.0001) and its expression in &gt;10% nuclei (p=0.0000) and with the expression of a DNA replication licensing factor in &gt;80% nuclei (p=0.0026).

In multivariate Cox regression analysis, the G1/S-specific cell cycle protein (HR=0.62, p=0.020, 95%CI 0.42-0.92), the disintegrin and metallopeptidase (HR=0.56, p=0.008, 95%CI 0.37-0.86) and the ubiquitin-conjugating enzyme (HR=1.68, p=0.015, 95%CI 1.1-2.5) were independent prognostic variables for predicting disease progression to muscle invasive bladder cancer when stratifying for other known clinical and histopathological risk factors as stage, age and grade. The Ubiquitin-conjugating enzyme was selected for in vitro functional analyses probably affecting cell proliferation and cell migration of bladder cancer cell lines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 300. doi:10.1158/1538-7445.AM2011-300