Prostate cancer (KEGG map)

The KEGG prostate cancer map (hsa05215) draws the androgen receptor (AR) as the central node. Testosterone is converted by SRD5A2 to dihydrotestosterone, which releases AR from HSP90 chaperones so it enters the nucleus and, with co-activators (CREBBP, EP300, NCOA family), switches on target genes such as KLK3 (PSA), TMPRSS2 and, through the TMPRSS2-ERG fusion, the ERG oncogene. During androgen deprivation the map shows how AR signalling is re-established: AR gene amplification, AR mutations that respond to other ligands, altered co-activator activity and growth-factor cross-talk. The second arm is growth-factor signalling: EGFR, ERBB2, IGF1R, FGFR and PDGFR feed PI3K to AKT to mTOR, and AKT both stabilises AR output and inhibits FOXO and BAD. PTEN loss, which is very common, and NKX3.1 loss lower p27 (CDKN1B) and remove restraint on the cell cycle, while MDM2 activation by AKT lowers p53. KEGG also draws GSTP1 silencing, which removes carcinogen detoxification in prostatic intraepithelial neoplasia, and FOLH1 (PSMA), the surface protein now used for imaging and radioligand therapy. Watson, Arora and Sawyers, Nat Rev Cancer, 2015 (doi:10.1038/nrc4016) review how castration-resistant tumours restore AR signalling through amplification, ligand-binding-domain mutations (such as F877L under enzalutamide), constitutively active splice variants like AR-V7, intratumoural androgen synthesis and glucocorticoid receptor substitution, and how PTEN loss and lineage plasticity provide AR-independent escape.

What drugs do about it: androgen deprivation (GnRH agonists or antagonists) removes the ligand; abiraterone blocks CYP17-dependent androgen synthesis; the AR antagonists enzalutamide, apalutamide and darolutamide stop AR binding DNA even when amplified; the AKT inhibitor capivasertib with abiraterone is approved for PTEN-deficient metastatic castration-resistant disease; and the PSMA radioligand lutetium-177 vipivotide tetraxetan (Pluvicto) delivers radiation to FOLH1-expressing cells after AR pathway inhibitors.