Watanabe M, Kanao K, Suzuki S, et al. - Researchers analyzed 15 radical prostatectomies (RP) specimens and 60 biopsy specimens from patients diagnosed with prostate cancer in order to assess the expression of C-C chemokine receptor 4 (CCR4)-positive Tregs (CCR4+Tregs) in prostate cancer and the clinical potential of CCR4-targeting therapy for prostate cancer. A higher expression of CCR4+Tregs was found in RP specimens with a higher (≥ 8) Gleason score vs those with a lower (< 8) Gleason score. For CCR4, 65.9% Tregs were positive in biopsy specimens. The number of CCR4+Tregs positively associated with the clinical stage and Gleason score. In the poor prognosis group vs the good prognosis group, the total number of Tregs and CCR4+Tregs significantly rose. Moreover, a significantly longer time to progression to castration-resistant prostate cancer (CRPC) and median survival time was seen in patients with lower CCR4+Treg expression levels vs those with higher expression levels. CCR4+Tregs are profoundly infiltrated in the prostate tissue of patients with poor prognosis with the potential to progress to CRPC. The prognosis of prostate cancer correlated with the degree of infiltration of CCR4+Tregs.