Expression of proto-oncogene c-Myc in patients with urinary bladder transitional cell carcinoma

BACKGROUND: c-Myc is a proto-oncogene located on human chromosome 8. It encodes a transcriptional factor which regulates the expression of approximately 10% to 15% of human genes, playing a crucial role in cell growth, differentiation, cellular metabolism, apoptosis, and cell transformation. The aim of this study is to correlate the expression of c-Myc in patients suffering from urinary bladder transitional cell carcinoma with tumor grade, stage, and lymph node metastases. MATERIALS AND METHODS: Formalin-fixed, paraffin-embedded tissue samples were obtained from 54 consecutive patients who underwent transurethral resection of bladder tumor or radical cystectomy (RC) as treatment for urinary bladder transitional cell carcinoma. Immunohistochemistry was performed using c-Myc monoclonal antibody and c-Myc expression was then analyzed for correlation with tumor stage, grade, and lymph node metastases. RESULTS: From a total of 54 patients, 42 (77.8%) had c-Myc positive staining and 12 (22.2%) were c-Myc negative. In the c-Myc positive group, 28 patients (66.7%) had low grade tumors and 33 (78.6%) presented with non-muscle-invasive disease (p < 0.05). In the c-Myc negative group, 10 patients (83.3%) had high-grade disease and 8 (66.7%) presented with muscle-invasive disease (p < 0.05). Lymph node metastases were evaluated in 17 patients who underwent RC. Of these, 5 had lymph node metastases, 4 of whom had c-Myc negative staining (p < 0.05). CONCLUSIONS: In our study, c-Myc negative staining was associated with higher grade and higher stage disease. On the contrary, most c-Myc positive tumors were low grade and non-muscle-invasive disease. In patients who underwent RC, c-Myc negative staining was associated with lymph node metastases.