CREB3L4 and prostate carcinoma: Our study demonstrated that the AR axis upregulates the expression of SPDEF, which in turn SPDEF directly promotes transcription of AIbZIP. It is well known that SPDEF is highly expressed in androgen-sensitive prostate cancer cells LNCaP and LNCaP C4-2, but depleted in androgen-insensitive cells PC-3 and DU-14536, 37, 38.