Abstract 436: ΔNp63 is critical for progression of high grade non-muscle invasive bladder cancer to muscle-invasive disease
Authors: Castillo-Martin Mireia , Gladoun Nataliya , Gaya-Sopena Josep Maria , Bonal Dennis M. , Redorta Joan Palou , Cordon-Cardo Carlos 
Published: May 2015

Background. Non-Muscle Invasive Bladder Cancer (NMIBC) represents a heterogeneous disease with very different outcomes depending on progression to muscle invasive disease (MID). NMIBC is one of the major causes of malignancy-related morbidity and mortality worldwide and it is the ninth most costly cancer in the United States in terms of overall expenditures. Even though some clinical and molecular risk factors have been reported to predict progression, they have shown limited prognostic ability in the clinical setting to define which patients should be treated immediately with radical cystectomy. It is therefore critical to identify markers that can help clinicians provide individualized risk-stratified decision-making. In preliminary clinical studies we have uncovered the significance of ΔNp63 as a protective individual marker of NMIBC tumor progression. The main goal of this project is to study the mechanism by which ΔNp63 loss triggers tumor progression to MID.

Experimental design. We generated a Knock-down cell line (RTT112_shΔ) using specific shRNA against the ΔNp63 isoform in the RT112 NMIBC cell line (RT112_P). Gene expression and “in vitro” functional analysis such as cell cycle, proliferation, colony formation and matrigel invasion assays were performed comparing RT112_P and RT112_shΔ cells. Moreover, we used a novel bladder orthotopic xenograft mouse model to examine the “in vivo” effects of ΔNp63 loss in bladder tumor progression.

Results. Gene expression analyses revealed that 164 genes were significantly upregulated and 104 downregulated in RT112_shΔ cells, some of them involved in critical pathways of tumor invasion. Functionally, we observed that RT112_shΔ cells showed a higher proliferation both “in vitro” and “in vivo” as well as an increased colony formation activity when compared to parental cells. Furthermore, RT112_shΔ cells displayed a superior invasion capacity “in vitro”, which correlated with a higher tumor initiation in the bladder orthotopic “in vivo” mouse model. Notably, RT112_shΔ bladder tumors were significantly associated with higher rate of lung metastasis than RT112_P tumors.

Conclusions. Here we show that ΔNp63 loss is a major event implicated in the progression of NMIBC to MID through alteration of important genetic pathways. Our findings can ultimately assist clinicians in developing personalized medicine, identifying patients who will benefit from early radical cystectomy to prevent tumor progression, as well as patients with low risk. Consequently, it will have a great impact in reducing the economic cost of this disease for the health care system. Finally, these studies unlock the opportunity of generating new therapeutic strategies to target previously unknown altered pathways in these tumors.

Citation Format: Mireia Castillo-Martin, Nataliya Gladoun, Josep Maria Gaya-Sopena, Dennis M. Bonal, Joan Palou Redorta, Carlos Cordon-Cardo. ΔNp63 is critical for progression of high grade non-muscle invasive bladder cancer to muscle-invasive disease. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 436. doi:10.1158/1538-7445.AM2014-436