Transcriptional machinery & addiction
Cancer cells run a few genes (MYC, their lineage factors, their fusion oncogenes) at extreme volume from giant control regions called super-enhancers. The amplifiers, BRD4, CDK7, CDK9 and Mediator, are the same in every cell, but cancers are unusually dependent on them, and that dependence is druggable.
Lineage transcription factors (ER, AR, MITF, SOX2, ASCL1) and oncogenic fusions (EWSR1-FLI1, TMPRSS2-ERG, PAX3-FOXO1, NUT-BRD4) nucleate super-enhancers: clusters of enhancers densely loaded with Mediator, BRD4 (reading acetyl-lysine), p300/CBP, and cohesin loops to promoters. RNA Pol II is released from promoter-proximal pausing by P-TEFb (CDK9) and initiated by TFIIH (CDK7); CDK12/13 couple elongation to DNA-repair gene expression. MYC, itself super-enhancer-driven and amplified or ecDNA-borne, is an amplifier of all active genes. Because oncogene transcripts and proteins (MYC, MCL-1) are short-lived, transient inhibition of BET, CDK7 or CDK9 collapses them first ('transcriptional addiction'). Menin-KMT2A is a lineage-specific version (revumenib, ziftomenib in NPM1/KMT2A AML); CDK12 loss creates a tandem-duplicator phenotype in prostate cancer. Hormone receptors are the oldest transcription drugs; BET inhibitors were limited by thrombocytopenia, CDK9 inhibitors and BET/CBP degraders are in trials.
In one picture
A concert where a few songs are played at deafening volume through rented amplifiers. Cutting the mains for a moment (BET, CDK7/9 inhibitors) silences the loudest songs first because their sound decays fastest, while the quieter household appliances keep humming.
Diagram
top- Nuclear receptor drugs (endocrine therapy, ARPIs, SERDs, PROTAC vepdegestrant) are transcription drugs
- Menin inhibitors revumenib and ziftomenib in KMT2A-rearranged and NPM1-mutant AML
- BET inhibitors and BET/CBP degraders; CDK7 (samuraciclib) and CDK9 inhibitors in trials
- Fusion-TF cancers (Ewing, NUT carcinoma) are the proving ground for transcriptional drugs
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