Hedgehog pathway activation in human transitional cell carcinoma of the bladder

The Hedgehog (Hh) signalling pathway functions as an organiser in embryonic development. Recent studies have shown constitutive activation of this pathway in various malignancies, but its role in bladder cancer remains poorly studied.

Expression levels of 31 genes and 9 microRNAs (miRNAs) involved in the Hh pathway were determined by quantitative real-time RT-PCR in 71 bladder tumour samples (21 muscle-invasive (MIBC) and 50 non-muscle-invasive (NMIBC) bladder cancers), as well as in 6 bladder cancer cell lines.

The SHH ligand gene and Gli-inducible target genes (FOXM1, IGF2, OSF2, H19, and SPP1) were overexpressed in tumour samples as compared with normal bladder tissue. SHH overexpression was found in 96% of NMIBC and 52% of MIBC samples, as well as in two bladder cancer cell lines. Altered expression of miRNAs supported their oncogene or tumour-suppressor gene status. In univariate analysis, high expression levels of PTCH2, miRNA-92A, miRNA-19A, and miRNA-20A were associated with poorer overall survival in MIBC (P=0.02, P=0.012, P=0.047, and P=0.036, respectively).

We observed constitutive activation of the Hh pathway in most NMIBC and about 50% of MIBC. We also found that some protein-coding genes and miRNAs involved in the Hh pathway may have prognostic value at the individual level.