[Comment to: "Detection and molecular staging of bladder cancer using real-time RT-PCR for gelatinases MMP-2, MMP-9 and TIMP-2 in peripheral blood"].

INTRODUCTION Molecular staging of bladder cancer based on the detection of mRNA of urothelial specific genes in circulating cancer cells has been inconclusive. We analyze whether real-time RT-PCR evaluation of gelatinases (MMP-9, MMP-2) and TIMP-2 in peripheral blood to diagnose and characterize patients with bladder neoplasm. MATERIAL AND METHOD Total RNA is extracted from circulating blood cells in 42 individuals (11 healthy controls, 31 patients with bladder cancer of different stages) and real-time RT-PCR performed using specific primers for MMP-9, MMP-2, TIMP-2 and ribosomal 18S. The quantification values of mRNA are described as relative to 18S mRNA (ΔΔCt method) and the results are blindly compared with data obtained from histological diagnosis and clinical staging. RESULTS Normalized levels of MMP-9 and MMP-2 mRNA are higher in patients with cancer than controls (1.82±0.6-fold and 2.7±0.6-fold, respectively; P<.05). Patients with metastatic disease also have increased MMP-9, MMP-2 and TIMP-2 mRNA levels (9.6±0,20-fold, 5.22±0.26-fold and 1,97±0,22-fold, respectively; P<.05). MMP-9 and MMP-2 are also associated with advanced clinical stage and grade (P<.05). A ratio between variables that increases the ability to segregate patients with Ta, T1, T2-4M0 and T2-4M1 tumours is proposed. CONCLUSIONS Both non-invasive bladder tumor recognition and molecular staging of the disease is possible using real-time RT-PCR-based detection of gelatinases and TIMP-2 in peripheral blood. The ability to distinguish metastatic disease is higher for MMP-9 but MMP-2 discriminates better levels of tumour invasion. Further investigation in this field could yield promising results regarding molecular evaluation of bladder neoplasia.