Another Tyr-rich protein, STAT3, is constitutively activated in PC by the phosphorylation of Tyr705, leading to PC tumor progression at multiple stages of tumorigenesis, starting with the Pdx1 transcription factor-driven initiation of acinar-to-ductal metaplasia [73] (which is believed to be a precursor lesion of PC [1]). This evidence concerns the gene PDX1 and pachyonychia congenita.