TDO2 and Familial prostate cancer: The loss of H3K27me3 at the TDO2 transposon (L1PA5) allows GR to form a transcriptional loop between GREs in the L1PA5 promoter and the TDO2 promoter and subsequently activates TDO2 transcription and the Kyn-AhR pathway, which functions to maintain the survival of dormant tumour cells and to encourage the onset of recurrence and the progression of prostate cancer to the CRPC stage (Fig. 6).