Identification of molecular events associated with evolution of multifocal and metastatic urothelial cancer

Urothelial cell carcinoma of the bladder is characterized by multifocality. Identification of molecular events associated with multifocal disease will increase understanding of disease pathogenesis, aid development of targeted therapies and ultimately lead to reduced morbidity, mortality and healthcare costs. In the first part of the project, I determined genome-wide copy number alterations and mutations in key genes in synchronous multifocal non-invasive tumours in order to:
• Assess monoclonal or oligoclonal origin.
• Assess molecular heterogeneity of tumours within one patient as this might imply differential response to treatment.
• Identify specific features of multifocality i.e. is multifocal disease different from solitary disease matched for grade and stage.
One-way hierarchical cluster analysis of copy number and mutational data of FGFR3, PIK3CA and RAS genes from 66 tumours was performed to assess the relationships between the individual tumours of each patient. Tumours separated into 3 main clusters with tumours from the same patient tending to group together. The majority of tumours from the same patient shared at least a few copy number alterations indicating monoclonal origin.
Comparison of multifocal and solitary tumours of the same grade and stage revealed that multifocal tumours exhibited higher frequencies of chromosomal alterations than solitary counterparts.
In the second part of the project I used immunohistochemistry on tissue microarrays to assess whether the FGFR3 expression status of a primary bladder tumour can serve as a surrogate for the related metastases.
Expression levels in two evaluable tissue spots from the primary tumour (n= 97) or the lymph node metastases (n = 90) showed a high level of concordance (primary tumour: OR=8.6, p=0.000003; metastases: OR=16.7, p=0.0000002).
With few exceptions, the levels of FGFR protein expression were the same in matched primary and metastatic lesions (p=0.78), suggesting that expression in the primary tumour can be used to select FGFR-targeted therapy for disseminated disease.