PTCH1 and prostate carcinoma: 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.