To demonstrate paracrine activation of the pathway in mouse MC3T3 cells cultured with human LNCaP or LNShh cells, the expression of known Shh target genes Gli1 and Ptc1 in MC3T3 cells was determined by quantitative real-time RT-PCR analysis using species-specific primer sequences which amplified these genes in mouse cells but not in human prostate cancer cells [6,10]. The gene discussed is GLI1; the disease is prostate carcinoma.