SOX9 (SRY (sex determining region Y)-box 9). This transcription factor has been recently identified as having an importat role during embryogenesis and in the early stages of prostate development [76, 77] and in testis determination [78] , processes that link SOX9 upregulation to cancer development [79] . Basal epithelial cells do express SOX9 in a normal prostate. While there exists no detectable expression in lumina epithelial cells, SOX9 has already been reported as ''expressed in primary prostate cancer in vivo, at a higher frequency in recurrent prostate cancer and in prostate cancer cell lines (LNCaP, CWR22, PC3, and DU145)'' [80] . Wang et al., also in [80] add that: ''Significantly, down-regulation of SOX9 by siRNA in prostate cancer cells reduced endogenous AR protein levels, and cell growth indicating that SOX9 contributes to AR regulation and decreased cellular proliferation. These results indicate that SOX9 in prostate basal cells supports the development and maintenance of the luminal epithelium and that a subset of prostate cancer cells may escape basal cell requirements through SOX9 expression.'' An increased value of SOX9 expression in advanced prostate cancer has been associated to tumor progression and the epithelial-mesenchymal transition [81] . SOX9 expression has been associated with a putative subgroup of prostate cancer [82] , associated to lymph-node metastasis (as seems to be the case in this dataset) and has a know role in chondrogenic differentiation processes [83] .