Under such a circumstance, IL-6 has been considered to act as the signaling messenger in many hormone refractory cancer cells, which in reality is associated with signaling pathway net including the mitogen-activated protein kinase (MAPK), the signal transducer and activators of transcription-3 (STAT-3), etc. As often cited, MAPK is related with cell growth and differentiation, while STAT-3 is able to activate the androgen receptor (AR) in the prostate cells through the expression of some neuropeptides. Here, STAT3 is linked to cancer.