High-throughput tissue microarray analysis of erbB-2 gene amplification in urinary bladder cancer. A study of Bulgarian patients

Introduction: Overexpression of the receptor Her-2 leads to increased proliferative response to epidermal growth factors which plays a key role in tumor development and growth. Increased oncoprotein level, in the majority of cases, is caused by erbB-2 gene amplification. To define the frequency of amplifications of erbB-2 in bladder cancer, and to determine their association with the tumor phenotype we utilized tissue microarray (TMA) approach.

Materials and methods: We analyzed a TMA consisting of 159 transitional cell bladder carcinomas for erbB-2 gene amplification by dual-color FISH.

Results: The frequency of erbB-2 amplification was 5.3% of all successfully analyzed samples (4 of 75). It increased from minimally invasive (pT1) to muscle-invasive (pT2-4) tumors, as well as with advanced tumor grade (G1 to G2 to G3). All amplifications were cluster amplifications confirming the fact that erbB-2 amplification occurs intrachromosomally in bladder cancer.

Conclusions: We concluded that despite its low incidence, erbB-2 amplification is of importance for the bladder tumor invasion and progression.