To shed light on the transcriptional regulation of androgen biosynthetic enzymes in tumors, we have previously shown that ERG factor regulates key enzymes in androgen synthesis [11]; thus, TMPRSS2-ERG fusion positive cancer cells producing intracellular androgens are better responders to abiraterone therapy Herein, we extended this concept to in vivo tumor studies. This evidence concerns the gene TMPRSS2 and cancer.