POU5F1 and prostate carcinoma: Important examples of such direct cooperativity include the p53 homotetramer[1], the NF-κB heterodimer[2], various bHLH dimers[3], SOX2–POU5F1 (SOX2–OCT4) dimerization in embryonic stem cells[4] and, more recently, AR–FOXA1 dimerization in prostate cancer cells[5].