A99
MDM2 links disease progression with motility and invasion in renal cell carcinoma
Radoslaw Polanski1, Aidan Noon1, Keith Parsons2, Helen Kalirai1, Ashraf el-Fert1, Howida Shawki2, Fiona Campbell2, Bryony Lloyd1, Ross Sibson1, Sarah Lake1, Sarah Coupland1, Carlos Rubbi1, Andy Dodson2, Nikolina Vlatkovic1, Mark Boyd1
1University of Liverpool, Liverpool, UK, 2Royal Liverpool University Hospital, Liverpool, UK
Background
A growing body of evidence suggests that up-regulation of p53 identifies a subset of patients with renal cell carcinoma (RCC) that have reduced disease free survival and/or overall survival. In some studies it has been observed that this is associated with increased MDM2 expression which is an unexpected observation.
Method
We have created a tissue microarray from a cohort of 90 patients with RCC and analysed these by IHC for p53, MDM2 and p21. p53 was also analysed by FASAY and DNA sequencing. p53 and/or MDM2 expression in RCC cell lines was modulated by stable transfection and/or by treatment with siRNAs and motility and invasion were assayed in Boyden chambers coated with matrigel as required.
Results
12/14 patients with p53 up-regulation harbour wild-type p53. p53 up-regulation in RCC is strongly linked with MDM2 up-regulation (P=0.000012) and up-regulation of both p53 and MDM2 identifies a sub-group of patients with significantly reduced disease specific survival both by univariate (P=0.036) and Cox multiple regression analysis (P=0.027, RR=3.2). In a range of RCC cells MDM2 promotes increased motility and invasion.
Conclusion
Patients with RCC typically die from metastatic disease and our analysis links disease progression with p53/MDM2 up-regulation in a tissue specific manner. We have also identified MDM2 as a determinant of motility and invasiveness in RCC cells. We also show that whilst much of MDM2 function may depend upon its activity as an E3-ubiquitin ligase, its capacity to promote motility is not determined by this activity. Our studies thus identify the p53/MDM2 axis as an important avenue for further investigation. Finally, our studies suggest a novel druggable therapeutic target in RCC which regulates p53/MDM2 expression in these cells.
