In line with these previous data, results from this study demonstrated that ATRA was able to induce growth arrest of two AR− prostate cancer cells DU145 and PC-3 in a dose-dependent manner (Fig. 1A and Fig. S1), and this effect was partially achieved through promoting HOXB13 mRNA and protein production (Fig. 1C and S2, S3). This evidence concerns the gene HOXB13 and prostate cancer.