MAPK3 and Familial prostate cancer: However, it has been reported that phosphorylation of STAT3 at serine 727 via ERK1 and/or 2 negatively regulates STAT3 activity (Kim et al, 2002; Tian et al, 2004), this supports our data that pSTAT3Ser727 is not associated with the development of hormone-refractory prostate cancer or prostate cancer patient survival.