Furthermore, some studies have observed that expression of CD155 could be induced by pathways such as Raf-MEK-ERK-AP-1 and through the Sonic Hedgehog pathway, which is highly active in advanced prostate cancer and can be indirectly mediated by STAT-3 via regulation of the TTF-1 promoter [44–46]. This evidence concerns the gene TTF1 and prostate carcinoma.