To demonstrate activation of Shh signalling in pre-osteoblasts by Shh-expressing prostate cancer cells in mixed cultures, the expression of known Shh target genes Gli1 and Ptc1 were determined by quantitative real time RT-PCR analysis using species specific primer sequences (Table 1) which amplified these genes in mouse MC3T3 cells but not in the human prostate cancer cells. This evidence concerns the gene GLI1 and prostate cancer.