BET inhibitors and prostate cancer getting some attention in Nature Medicine this week. Three articles published yesterday by three different groups on how SPOP mutations affect BET inhibition therapy for prostate cancer.

Prostate cancer–associated SPOP mutations confer resistance to BET inhibitors through stabilization of BRD4 by Xiangpeng Dai et al.

Recurrent mutations in SPOP-encoding a Cullin 3-based E3 ubiquitin ligase- in prostate cancer disrupt the recognition and degradation of ubiquitination substrates, including BET proteins. Consequently, stability of BET proteins is enhanced and this increases the resistance to BET inhibitors in SPOP-mutant prostate tumors. These results, together with those in Janouskova et al. and Zhang et al., uncover a novel non genetic mechanism of resistance to BET inhibition involving cancer type-specific mutations in SPOP, and support the evaluation of SPOP mutations to inform the administration of BET inhibitors in the clinic.

Opposing effects of cancer-type-specific SPOP mutants on BET protein degradation and sensitivity to BET inhibitors by Hana Janouskova et al.

Different mutations found in endometrial and prostate tumors affecting the substrate-recognition domain of SPOP, a component of the E3 ubiquitin ligase complex, result in opposing degradation activity of BET proteins and response to BET inhibitors. This work, along with findings by Zhang et al. and Dai et al., highlights the divergent effects of recurrent mutations affecting different residues within the same functional domain of SPOP and provides scientific rationale to guide the administration of BET inhibitors in endometrial and prostate cancer patients harboring SPOP mutations.

Intrinsic BET inhibitor resistance in SPOP-mutated prostate cancer is mediated by BET protein stabilization and AKT–mTORC1 activation by Pingzhao Zhang et al.

Mutations in SPOP, the gene encoding a component of the E3 ubiquitin ligase complex, impair ubiquitination-dependent degradation of BRD2, BRD3 and BRD4 proteins and result in activation of ATK–mTORC1 signaling and resistance to BET inhibitors. Pharmacological blockade of AKT represents a viable strategy to restore the sensitivity of SPOP-mutant prostate tumors to BET inhibitors. These results, together with findings by Dai et al. and Janouskova et al., uncover a new nongenetic mechanism of resistance to BET inhibition involving cancer-type-specific mutations in SPOP, and support the evaluation of SPOP mutation status to inform the administration of BET inhibitors in the clinic.